JP5295741B2 - Composite of metal alloy and fiber reinforced plastic and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a joining force when metal alloy and fiber-reinforced plastic is joined together by a one-liquid type epoxy adhesive. <P>SOLUTION: An A7075 piece is etched, a roughness of micron order is produced on its surface, ultrafine unevenness made of a recess 40-100 nm in diameter is formed, and the surface layer is made of a thin aluminum oxide layer. After the CFRP as an adhesion object is cured three times, the surface is roughened and washed. The one-liquid type epoxy adhesive in which an inorganic filler (1) with the center of particle size distribution of 5-20 &mu;m, an ultrafine inorganic filler (2) with a particle size of 100 nm or below, and polyethersulphone resin powder (3) are filled in an epoxy resin is applied on the A7075 piece and the CFRP so that both are fixed and cured. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a mobile machine, an electric device, a medical device, a general machine, and other general manufacturing fields. Specifically, the present invention relates to a technique for manufacturing a composite in which a metal alloy and fiber reinforced plastic (hereinafter referred to as “FRP (abbreviation of Fiber Reinforced Plastics)”) are firmly bonded with an epoxy-based adhesive. In particular, the present invention relates to a technique for manufacturing a composite in which a metal alloy and a carbon fiber reinforced plastic (hereinafter referred to as “CFRP (Carbon Fiber Reinforced Plastics)”) are bonded.

  A technique for integrating a metal alloy and a resin is required in all manufacturing industries such as aircraft, automobiles, home appliances, and industrial equipment, and many adhesives have been developed for this purpose. Among these are very good adhesives. For example, an adhesive exhibiting a function at room temperature or by heating is used for joining to integrate a metal alloy and a synthetic resin, and this method is currently a common bonding technique.

  On the other hand, bonding methods that do not use an adhesive have also been studied. There is a method in which a high-strength thermoplastic engineering resin is integrated with magnesium, aluminum, light metals such as alloys thereof, and iron alloys such as stainless steel without an adhesive. For example, as a method of joining simultaneously with resin molding by a method such as injection (hereinafter referred to as “injection joining”), polybutylene terephthalate resin (hereinafter referred to as “PBT”) or polyphenylene sulfide resin which is a thermoplastic resin for an aluminum alloy Manufacturing techniques for injection joining (hereinafter referred to as “PPS”) have been developed (see, for example, Patent Documents 1 and 2). In addition, it has been demonstrated that magnesium alloy, copper alloy, titanium alloy, stainless steel, and the like can be injection-bonded using the same type of resin (see Patent Documents 3, 4, 5, and 6).

  The principle of injection joining in Patent Documents 1 and 2 is shown below. The aluminum alloy is immersed in a dilute aqueous solution of a water-soluble amine compound, and the aluminum alloy is finely etched by the weak basicity of the aqueous solution. In this immersion treatment, ultrafine irregularities are formed on the surface of the aluminum alloy, and at the same time, adsorption of amine compound molecules on the surface of the aluminum alloy occurs. The surface-treated aluminum alloy is inserted into an injection mold, and the molten thermoplastic resin is injected at a high pressure. At this time, a chemical reaction occurs when the thermoplastic resin and the amine compound molecules adsorbed on the aluminum alloy surface are encountered. This chemical reaction suppresses a physical reaction in which the thermoplastic resin is rapidly cooled in contact with an aluminum alloy maintained at a low mold temperature to crystallize and solidify. As a result, the resin is delayed in crystallization and solidification, and in the meantime, enters the ultra-fine irregularities on the surface of the aluminum alloy. This makes it difficult for the thermoplastic resin to peel off from the aluminum alloy surface even when subjected to external force. That is, the resin molded product formed with the aluminum alloy is firmly bonded. In other words, the chemical reaction and the physical reaction are in a competitive relationship, and in this case, the chemical reaction is prioritized, so it can be said that strong injection joining occurs. In fact, it has been confirmed that PBT and PPS that can chemically react with an amine compound can be injection-bonded with the aluminum alloy. The inventors called this injection joining mechanism the “NMT” (abbreviation of Nano molding technology) theory.

  In addition, as shown in Patent Documents 3, 4, 5, and 6, the present inventors obtain special exothermic reaction or assistance of some chemical reaction without chemical adsorption of the amine compound to the metal alloy surface. We have found a condition that enables injection joining without any problem. In other words, for metal alloys other than aluminum alloys, we discovered a condition that allows the metal alloy and thermoplastic resin to be firmly joined by injection joining. The mechanism of injection joining based on this condition is described as “New NMT (Nano molding technology). Abbreviated) ”theory.

  All of these inventions are by the inventors, but they are based on a relatively simple joining theory. The inventors of the present invention refer to an injection joining theory relating to an aluminum alloy as “NMT (abbreviation of Nano molding technology)” theory, and an injection joining theory relating to all metal alloys as “new NMT” theory. The hypothesis of the “new NMT” theory that can be used more widely is as follows. That is, in order to obtain injection bonding with strong bonding strength, there are conditions on both the metal alloy side and the injection resin side. First, the following three conditions are necessary on the metal side.

[Conditions on the metal alloy side in the new NMT theory]
The first condition is that the metal alloy surface has irregularities with a period of 1 to 10 μm by a chemical etching method, and the irregularity height difference is about half of the period, that is, a rough rough surface of 0.5 to 5 μm. It is. However, in actuality, it is difficult to accurately cover the entire surface with the rough surface, and it is difficult to perform a chemical reaction that is not constant. Specifically, when viewed with a roughness meter, it is not within the range of 0.2 to 20 μm. Draw a roughness curve with regular periodic irregularities and a maximum height difference in the range of 0.2-5 μm, or scan with the latest dynamic mode scanning probe microscope to meet JIS standards ( JISB0601: 2001) The average period, that is, the roughness surface having a peak-valley average interval (RSm) of 0.8 to 10 μm and a maximum height roughness (Rz) of 0.2 to 5 μm, is shown above. It is considered that the roughness condition was substantially satisfied. The inventors of the present invention called the “surface having a micron-order roughness” as an easy-to-understand word because the ideal rough surface irregularity period is approximately 1 to 10 μm as described above.

  The second condition is that ultrafine irregularities of 5 nm or more are further formed on the surface of the metal alloy having a roughness on the order of microns. In other words, it needs to be rough when viewed with microscopic eyes. In order to satisfy these conditions, the surface of the metal alloy is subjected to fine etching, oxidation treatment, chemical conversion treatment, etc., and the inner wall surface of the concave portion having the above-mentioned micron-order roughness is 5 to 500 nm, preferably 10 to 300 nm. Preferably, ultra fine irregularities with a period of 50 to 100 nm are formed.

  Describing the ultra-fine irregularities, if the irregular period is a period of 10 nm or less, it is clearly difficult to enter the resin component. Further, in this case, since the unevenness height difference is usually small, it looks smooth as viewed from the resin side. As a result, it no longer serves as a spike. Also, if the period is about 300 to 500 nm or longer (in that case, the diameter and period of the concave part having a micron order roughness is estimated to be close to 10 μm), the spike in the micron order concave part Because the number of slashes, the effect becomes difficult to work. Therefore, in principle, it is necessary that the period of the ultra fine irregularities is in the range of 10 to 300 nm. However, depending on the shape of the ultra-fine irregularities, the resin may enter between them even if it has a period of 5 nm to 10 nm. For example, this is the case when rod-like crystals having a diameter of 5 to 10 nm are complicated. Even with a period of 300 nm to 500 nm, the shape of the ultra-fine irregularities may easily cause an anchor effect. For example, this corresponds to an infinitely continuous staircase having a height and depth of several hundred to 500 nm and a width of several hundred to several thousand nm. Including such a case, the required period of ultra fine irregularities was specified to be 5 nm to 500 nm.

  Here, conventionally, regarding the first condition, the range of Rsm was defined as 1 to 10 μm and the range of Rz was defined as 0.5 to 5 μm, but Rsm was 0.8 to 1 μm and Rz was 0.2 to 0.2 μm. Even if it is the range of 0.5 micrometer, if the uneven | corrugated period of an ultra fine unevenness | corrugation exists in the especially preferable range (generally 30-100 nm), joining force can be maintained highly. Therefore, the Rsm range was slightly expanded to a smaller value. That is, Rsm was in the range of 0.8 to 10 μm and Rz was in the range of 0.2 to 5 μm.

  Furthermore, the third condition is that the surface layer of the metal alloy is ceramic. Specifically, with respect to the metal alloy type that originally has corrosion resistance, the surface layer needs to be a metal oxide layer having a thickness equal to or greater than that of the natural oxide layer, and the metal alloy type having relatively low corrosion resistance ( For example, in the case of a magnesium alloy or a general steel material, the third condition is that the surface layer is a thin layer of metal oxide or metal phosphorous oxide generated by chemical conversion treatment or the like. These are schematically illustrated as shown in FIG. The surface of the metal alloy phase 40 is formed with a concave portion (C) having a roughness on the order of microns, and further, an ultrafine unevenness (A) is formed on the inner wall of the concave portion, and the surface layer becomes a ceramic layer 41. A part of the cured adhesive phase 42 has infiltrated into the ultra-fine irregularities. When the liquid resin composition penetrates into the surface of the metal alloy thus formed and is cured after the penetration, the metal alloy and the cured resin composition are joined together very firmly.

[Conditions on the resin side in the new NMT theory]
Next, the conditions on the resin side will be described. As the resin, it is possible to use a hard, highly crystalline thermoplastic resin that has a reduced crystallization rate during quenching by compounding another polymer suitable for this. Actually, a resin composition compounded with another polymer suitable for PBT or PPS, which is a crystalline hard resin, and glass fiber can be used.

[Injection joining based on the new NMT theory]
The above metal alloy and resin can be used for injection joining with a general injection molding machine or injection mold. This process will be described according to the above-mentioned “new NMT” theoretical hypothesis. The injected molten resin is introduced into a mold having a temperature of about 150 ° C. lower than the melting point, but is cooled in this flow path, and is considered to be a temperature below the melting point. That is, when the molten crystalline resin is rapidly cooled, even if the melting point is lower than the melting point, crystals are formed in zero time and do not change to a solid. In short, a melted state below the melting point, that is, a supercooled state exists for a very short time. As described above, this supercooling time can be lengthened a little by applying a special compound to PBT or PPS. This was used to allow the microcrystals to penetrate into the concave portions of the metal surface having a roughness on the order of microns before the viscosity rapidly increased due to the generation of a large amount of microcrystals. Since it continues to cool after intrusion, the number of microcrystals increases rapidly with this, and the viscosity increases rapidly. However, whether the resin can reach the depth of the recess depends on the size and shape of the recess.

  In the experimental results of the present inventors, the metal type is not selected, and the concave portion having a diameter of 1 to 10 μm according to the roughness on the micron order, and if the depth is about half of the period, the concave portion is quite deep. It was estimated that microcrystals invaded. Furthermore, if the inner wall surface of the recess is rough when viewed with a microscopic eye as in the second condition described above, a part of the resin also penetrates into the ultra-fine irregularities, and as a result, a pulling force is exerted on the resin side. It is presumed that even if it is added, it will be caught and difficult to come off. And if this rough surface is covered with metal oxide or metal phosphorous oxide as shown in the third condition, the hardness is high, and the catch between the resin and the concave portion related to the ultra fine unevenness is effective as a spike. Become.

  A specific example is shown. For example, in the case of a magnesium alloy, the corrosion resistance of a magnesium alloy that is still covered with a natural oxide layer is low, so by converting this into a metal oxide, metal carbonate, or metal phosphate, The surface can be covered with a ceramic material having high hardness. When the surface-treated magnesium alloy is inserted into an injection mold, the mold and the inserted magnesium alloy are kept at a temperature lower than the melting point of the resin to be injected by at least 100 ° C. As soon as it enters the flow path in the mold, it is rapidly cooled, and when it approaches the magnesium alloy, there is a high possibility that it is below the melting point.

  When the diameter of the concave portion on the surface of the magnesium alloy is relatively large, such as about 1 to 10 μm, the resin can enter within a limited time during which microcrystals are generated by supercooling. Further, even when the number density of the generated polymer microcrystal group is still small, the resin can penetrate if it is the concave portion. Because the size of a microcrystal, that is, a crystallite having a shape when an alignment state occurs from a molecular chain that has been moving irregularly to a molecular chain, is estimated to be a size of several to 10 nm when estimated from a molecular model. It is. Therefore, it is difficult to say that microcrystals can easily penetrate into ultrafine irregularities with a diameter of 10 nm. However, if the ultrafine irregularities have a period of several tens of nm, there is a possibility that the tip of the resin flow slightly enters. However, since innumerable microcrystals are generated at the same time, the viscosity of the resin flow rapidly rises at the point where it is in contact with the tip of the injection resin or the metal mold surface. When the surface of the magnesium alloy that has been subjected to chemical conversion treatment is observed with an electron microscope, an ultrafine uneven surface with a period of 10 to 50 nm is observed, and if this is an ultrafine unevenness with a period of this level, the head is thrust before the viscosity of the resin flow suddenly rises. obtain.

  In addition, when the surface of a metal alloy such as a copper alloy, titanium alloy, or steel material is oxidized or subjected to chemical conversion treatment to form a ceramic crystallite group such as a metal oxide or an amorphous layer, a PPS resin (rapidly cooled) When injection bonding of a PPS resin compound that was able to reduce the PPS molecular crystallization speed at the time, a considerably strong bonding force was generated.

  Here, the bonding itself is a problem of the resin component and the surface of the metal alloy, but if the resin composition contains reinforcing fibers or inorganic fillers, the linear expansion coefficient of the entire resin can be brought close to that of the metal alloy, so It becomes easy to maintain the bonding force. For example, a composite obtained by injection-bonding a PBT or PPS resin to a magnesium alloy, copper alloy, titanium alloy, stainless steel, etc. has a shear breaking force of 20 to 30 MPa (about 200 to 300 kgf / cm 2) or more. The force is 30 to 40 MPa (about 300 to 400 kgf / cm 2) or more, which is confirmed to be a strong composite.

[NAT theory (adhesive bonding)]
The present inventors considered that the “new NMT” theoretical hypothesis can be applied to adhesive bonding, and confirmed whether high-strength bonding based on a similar theory is possible. And it tried to obtain the composite_body | complex with higher adhesive force by using the commercially available general-purpose one-component epoxy adhesive and devising the surface structure of the metal alloy.

  The procedure regarding the experimental method of adhesive bonding is shown below. Based on the “new NMT” theory, a metal alloy having the same surface as that used in the injection joining experiment (that is, a metal alloy satisfying the above three conditions) was prepared. Then, a liquid one-part epoxy adhesive is applied to a predetermined range of the metal alloy, placed in a desiccator, once placed in a vacuum, and then returned to normal pressure. Allow the adhesive to penetrate the surface. Thereafter, the adherend is bonded to the predetermined range and heated to be cured.

  In such a case, an epoxy adhesive having a certain viscosity can penetrate into the concave portion (roughness concave portion in the first condition) on the surface of the metal alloy having a roughness on the micron order because it is liquid. And the epoxy adhesive which penetrate | invaded hardens | cures in this recessed part by subsequent heating. Actually, an ultrafine unevenness is further formed on the inner wall surface of the recess (the second condition), and the ultrafine unevenness is a thin ceramic-like thin film (the third condition). Since it is covered, the epoxy resin that has entered the inside of the recess and solidified is difficult to come out by being gripped by ultra-fine irregularities such as spikes.

  The present inventors have applied the “new NMT” theory and have demonstrated that high strength adhesion between metal alloys and between metal alloys and CFRP is possible with a one-component epoxy adhesive. As an example, as a result of joining A7075 aluminum alloy plates with an adhesive composed only of a commercially available general-purpose epoxy adhesive, a joined body having an intense shear breaking force and tensile breaking force as high as 70 MPa could be obtained.

  In fact, such high-strength adhesive bonding has been demonstrated by the present inventors in magnesium alloys, copper alloys, titanium alloys, stainless steels, general steel materials, aluminum-plated steel sheets, and zinc-plated steel sheets following aluminum alloys. (See Patent Documents 7, 8, 9, 10, 11, 12, 13, and 14). In any case, various metal alloys could be bonded with unprecedented strength by controlling the state of the metal alloy surface. Specifically, it was a joined body in which various metal alloys were joined together using a commercially available one-component epoxy adhesive, and showed a shear breaking force or tensile breaking force of about 50 to 70 MPa. The present inventors have applied the “new NMT” theory for such adhesive bonding as “NAT (abbreviation of nano adhesion technology)”.

WO 03/064150 A1 (aluminum alloy) WO 2004/041532 A1 (Aluminum alloy) WO 2008/069252 A1 (magnesium alloy) WO 2008/047811 A1 (copper alloy) WO 2008/078714 A1 (titanium alloy) WO 2008/081933 A1 (stainless steel) PCT / JP2008 / 054539 (aluminum alloy) PCT / JP2008 / 057309 (magnesium alloy) PCT / JP2008 / 056820 (Copper alloy) PCT / JP2008 / 0571131 (titanium alloy) PCT / JP2008 / 057922 (stainless steel) PCT / JP2008 / 059783 (general steel) Japanese Patent Application No. 2007-336378 (aluminum plated steel sheet) Japanese Patent Application No. 2008-67313 (galvanized steel sheet) Japanese Patent Application No. 2007-325737 (CNT) JP 2006-89711 (CNT, Parker)

  As described above, the present inventors used a commercially available one-component epoxy adhesive, and based on the “NAT” theory, conducted an experiment in which metal alloys or metal alloys and CFRP were bonded to each other. Regarding the adhesive bonding between the alloy and the CFRP, the shear breaking force or the tensile breaking force tended to decrease as compared with the case where the metal alloy was bonded to each other. Strong bonding between a metal alloy and CFRP is expected in various fields such as aircraft and ships. However, with a commercially available one-component epoxy adhesive, the metal alloys that the present inventors have expected can be bonded to each other. The joining force equivalent to joining could not be produced. In addition, the composite in which the metal alloy and CFRP are bonded and bonded has a large variation between the composites in the shear breaking force or tensile breaking force, and there is a problem in practicality. Although it was possible to improve the adhesive and reduce the variation, this was achieved, but the deterioration of the bonding force compared to the case where the metal alloys were bonded and bonded became clear.

  The present invention has been made based on such a background, and an object thereof is to improve the bonding force when a metal alloy and a fiber reinforced plastic are bonded by a one-component epoxy adhesive.

  In the beginning, the present inventors optimally use co-curing (hereinafter referred to as “cocure”) in which the CFRP matrix resin and the resin constituting the adhesive are simultaneously cured in the adhesive bonding between the metal alloy and CFRP. I thought it was. That is, the CFRP prepreg uses a matrix resin made of a thermosetting epoxy resin composition, and the adhesive applied to the metal alloy also uses a thermosetting epoxy resin as a composition. It was estimated that joining was achieved. It was thought that both the CFRP prepreg and the epoxy adhesive were once melted and then gelled and cured together to achieve the optimum adhesive bonding. Therefore, the metal alloy coated with the adhesive and the CFRP prepreg were strongly bonded together and heat-cured in that state to obtain the above-described result.

  As described above, the result did not reach the bonding force between metal alloys. When a fracture surface (a fracture surface of a composite of an aluminum alloy and CFRP) was observed, a certain tendency was observed. Carbon fibers were always present on the fracture surface on the aluminum alloy side in the composite with high shear fracture strength. Since the carbon fiber was a black material, it could be confirmed visually. In addition, a composite having a higher shear breaking strength was confirmed to have more carbon fibers on the fracture surface on the aluminum alloy side. Here, it was a mass-produced CFRP prepreg that was adhesively bonded to the aluminum alloy, but there was a possibility that the carbon fiber was slightly raised from the surface of the prepreg. In that case, the protruding carbon fiber Had been taken into the adhesive applied to the aluminum alloy side and could remain on the aluminum alloy side after fracture.

  However, when the composite of the metal alloy and CFRP obtained by co-curing is sheared, the fracture surface does not occur at the interface between the adhesive cured layer and the CFRP matrix resin cured layer, but in the CFRP itself. There is also a possibility that the chain breaks starting from the inside of CFRP. Carbon fiber cords and carbon fiber cloths are severely surface-treated to improve affinity and adhesion with epoxy resin, and then form a sheet with both sides sandwiched by a matrix resin sheet, which is melted with a hot roll or the like. The CFRP prepreg is integrated with each other. Before the present inventors showed the NAT theory, the adhesive strength between the metal alloy and the epoxy adhesive cured layer was not as high as 60 to 80 MPa. Therefore, there was no problem caused by the low adhesion between the carbon fiber and the matrix resin. However, the above observation results may indicate that the adhesion between the carbon fiber and the matrix resin is inferior to the adhesion between the metal alloy and the epoxy-based adhesive. The low adhesive strength of the matrix resin also indicates the possibility of reducing the shear breaking force or tensile breaking force of the composite as a whole.

On the other hand, it was clear from the experiments by the present inventors that the shear breaking force of the joined body obtained by bonding and joining metal alloy pieces also varies depending on the thickness of the metal alloy pieces. The size of the metal alloy piece is not a 100 mm × 25 mm × 1 mm thick metal alloy piece for measuring the shear breaking force specified in the JIS adhesive test, but a small piece of 45 mm × 15 mm × 3 mm thickness or 45 mm × 18 mm × 3 mm thickness , The adhesive area was 0.6 to 0.8 cm ² , and the shear breaking strength was measured. As described above, the reason why the metal alloy piece is made smaller and thicker than the JIS standard is because the adhesive force when applying the NAT theory is much stronger than the adhesive force assumed by the JIS standard. is there. When the joined body joined with such an adhesive force is pulled to the extent of shear fracture, the local metal portion is stretched by the tension before the fracture and bending deformation starts. This causes a peeling failure at the edge of the adhesive surface, and the peeling failure is the starting point, and the remaining shear fracture occurs at a stroke, resulting in a total fracture. In order to relieve such stress concentration on the local area, it is necessary to increase the bending strength. To that end, it is necessary to make the metal alloy pieces thick and small test pieces.

  About various metal alloys, the surface treatment mentioned above was given for every metal alloy, and the adhesive strength test was done about the adhesion joining body of the same kind metal alloys. Here, it was attempted to obtain plate materials having a thickness of about 3 mm for various metal alloys. However, only a few plate materials having a thickness of 1 mm were available for most metal alloy types. The thickness of the copper alloy was 0.4 to 0.7 mm, and the thickness of the steel material was 1.6 mm. Originally, the bending strength varies depending on the alloy type, and the thickness varies. Therefore, regarding such a metal alloy, bending strength was reinforced by stacking.

  As an example, a thin KFC copper alloy piece (0.7 mm thick) was subjected to surface treatment, and four sheets were bonded together with an epoxy adhesive to form a 2.8 mm thick laminate. The copper alloy laminates having a thickness of 2.8 mm were bonded and bonded, and the shear breaking strength was measured to be 60 to 65 MPa. This is a value about 20 MPa higher than that of an unbonded copper alloy piece (0.7 mm thick), and it was revealed that the bonding was optimized by the lamination. This is equivalent to the shear breaking force exhibited by the bonded assembly of 3 mm thick A7075 aluminum alloy pieces. As a result of laminating thin metal alloy pieces by the same method to a thickness of about 3 mm, and bonding the laminated materials with a commercially available one-component epoxy adhesive and measuring the shear breaking force, regardless of the metal alloy type A shear breaking force of 60 to 70 MPa was exhibited. The NAT theory presented by the present inventors does not limit the target metal alloy type, and the strong joining force is based solely on the anchor effect, so when the numerical value of the shear breaking force converges to a specific range. Conceivable.

From the above, when the metal alloy is made into a small piece having a thickness of about 45 mm × 15 mm × 3 mm and bonded and bonded at an end portion of 0.6 to 0.8 cm ² , the bending deformation of the small piece is extremely small even when a shearing force of about 50 MPa is applied. I understand that. On the other hand, the shape of the CFRP piece used by the present inventors when the metal alloy piece and the CFRP piece were bonded using cocure was the same 45 mm × 15 mm × 3 mm thickness as the above shape. This shape of the CFRP piece is highly rigid and appears to have a bending strength equal to or greater than the 3 mm thick A7075 aluminum alloy piece.

  Based on the above examination results, if the object to be bonded and bonded to the metal alloy piece is a small and durable CFRP piece of about 45 mm × 15 mm × 3 mm thickness, if the adhesion between the metal alloy piece and the CFRP piece is perfect, It was thought that the shear fracture strength of 60 to 70 MPa should be exhibited. Further thinking that this concept is correct, the shear fracture force is not observed by the cocure method, and the reason why carbon fiber residue adheres to the metal alloy side after the fracture becomes clear. That is, the adhesive force between the carbon fiber in the CFRP and the matrix resin is insufficient. If the already hardened CFRP piece can be treated in some way to increase the adhesion between carbon fiber and matrix resin, it can produce high adhesive bonding strength based on NAT theory as well as the adhesion between A7075 aluminum alloy pieces. It was.

  Therefore, rather than a cocure that simultaneously cures uncured CFRP and adhesive, the bonding force is improved by so-called cobond that cures the adhesive with the adhesive interposed between the cured CFRP and the metal alloy. The experiment was conducted. However, in this experiment, the CFRP piece once obtained was used after further heat treatment. The reason for the additional heat treatment was because of the following estimation. That is, it was assumed that the curing method recommended by the prepreg manufacturer or actually used by the CFRP manufacturer was streamlined in terms of mass productivity and production efficiency. Even if the heat curing time for obtaining the CFRP material from the prepreg is double the manufacturer's recommended time, the curing rate of the matrix resin is improved from 97% to 98%, and the adhesion between the carbon fiber and the matrix resin is also improved by several percent. To do. In such a case, the manufacturer's production engineer does not double the heat-curing time for cost and time savings. This is because the CFRP material manufactured with the manufacturer-recommended heat-curing time only has to function sufficiently in practice. That is, assuming that the adhesive force between the carbon fiber and the matrix resin is sufficient under a general use environment, the use under conditions that require a shear breaking force of about 60 MPa or more is not assumed.

  The present inventors tried to improve the adhesion between the carbon fibers in the CFRP and the matrix resin by taking measures such as raising the curing temperature higher than the manufacturer's recommended conditions or repeating the curing process. Actually, the CFRP prepreg obtained from the purchased CFRP prepreg by applying the usual curing conditions (recommended by the manufacturer) is baked twice or three times at a slightly higher temperature. High adhesive strength.

  Even in the above case, it is a matter of course that there is no problem in the adhesive force between the cured adhesive and the cured matrix resin. For that purpose, it is necessary to give an appropriate surface treatment to the CFRP material so as to obtain a better adherend. The inventors searched for a specific method for making the CFRP piece an excellent adherend. That is, a large amount of CFRP pieces are prepared, and this is firmly polished with No. 80 to No. 1000 abrasive papers specified in JIS R6252, and roughened to such an extent that carbon fibers are not exposed, and various aqueous solutions, inorganic or organic solvents are used. Attempted surface modification such as washing with Furthermore, after apply | coating the adhesive agent to a CFRP piece, the process which once pressurizes after pressure reduction was carried out, and the adhesive agent was infiltrated into the CFRP piece. This CFRP piece was bonded to the A7075 aluminum alloy piece subjected to the surface treatment based on the NAT theory using an adhesive, and this was broken to measure the shear breaking force, and the fracture surface was observed. In this way, a method for roughening the CFRP piece that increases the shear breaking force was sought.

  Furthermore, the present inventors tried to improve the bonding force between the metal alloy and CFRP by improving the performance of the adhesive. The composition of the epoxy resin in the resin was standard, and the curing agent was not changed by adding a certain amount of dicyandiamide and its curing aid, and only the type and amount of filler were changed and tested. And the shear breaking force in normal temperature and 100 degreeC was measured, and the filler composition which shows the comprehensively excellent performance in the wide temperature range considered normal temperature range of normal temperature-100 degreeC was searched. As a result, the adhesive force at 100 ° C. can be improved by several tens of MPa only by adding the ultrafine inorganic filler.

  In the present invention, the metal alloy is subjected to surface treatment so as to satisfy the first condition to the third condition, and the CFRP as the adherend is subjected to multiple times of hardening and roughening, In addition, the present invention provides a composite that exhibits an extremely large bonding force as compared with the prior art by adhesively bonding them with an adhesive to which a filler is added. Hereinafter, all elements constituting the present invention will be described in detail.

[Improvement of adhesive]
In order to make the adhesive used for adhesively bonding the metal alloy and CFRP suitable for improving the heat resistance of the composite, the following requirements were satisfied.
(1) Including inorganic fillers (talc, clays).
(2) Add ultrafine inorganic fillers such as fumed silica.
(3) Amorphous thermoplastic resin, for example, polyethersulfone (hereinafter referred to as “PES”) powder is blended.
(4) Mixing the epoxy resin and all fillers with a sand grind mill.
4 requirements. Regarding (3), for the purpose of ensuring similarity with CFRP, PES powder often used for CFRP matrix resin was blended. In addition, since the present inventors obtained a good dispersion result by using the latest wet pulverizer for dispersion of carbon nanotubes, the requirement (4) was added. In addition, the adhesive maker usually manufactures the adhesive using an automatic mortar or a kneader for blending inorganic fillers and the like.

  Regarding the ultrafine inorganic filler of (2), an experiment was conducted after inferring the mechanism of destruction rather than merely estimating, and this requirement was defined. The present inventors measured the shear breaking strength of a joined body in which A7075 aluminum alloy (also referred to as “ultra-super duralumin”) pieces that were surface-treated so as to satisfy the first to third conditions described above were bonded and bonded together. . At this time, the shear breaking force at room temperature was measured using a commercially available one-component epoxy adhesive having dicyandiamide as a curing agent, and the value was as high as 65 to 70 MPa. On the other hand, the shear fracture strength at high temperatures of 100 ° C. and 150 ° C. was significantly reduced to 15-20 MPa and 6-7 MPa.

  Moreover, when the adhesive which used the imidazole type compound as the hardening | curing agent was used, although the shear breaking force in normal temperature was 50-60 MPa, the shear breaking force in 150 degreeC was about 15 MPa, and fell significantly. Epoxy adhesives that use imidazole compounds as curing agents are called heat-resistant adhesives, and even though they can exhibit stronger adhesive strength at higher temperatures than when dicyandiamide is used as a curing agent, this degree Only a shear breaking strength of was shown. The hardness of the cured resin suddenly decreases as it approaches the glass transition point (Tg). Since the Tg of the epoxy resin cured product using dicyandiamide or an imidazole compound as a curing agent is 100 to 140 ° C, the shear breaking force is rapidly reduced at 100 ° C or 150 ° C.

  The present inventors have inferred about the mechanism by which the adhesive strength is reduced due to a decrease in the hardness of the cured epoxy resin at a high temperature. The commercially available one-component epoxy adhesive using dicyandiamide as a curing agent is “EP106NL (manufactured by Cemedine)”, and the commercially available one-component epoxy adhesive using an imidazole compound as a curing agent is “ EP160 (Cemedine) ".

  And as a result of inference, the direct cause of fracture at high temperature is that the metal alloy surface is hardened in a state where it penetrates into a concave portion having a micron-order roughness, and further penetrates into the ultra-fine irregularities on the inner wall surface of the concave portion. The adhesive that had been softened at a high temperature no longer caused the spike effect due to the recesses and ultra-fine irregularities. This is based on the fact that when the fracture surface is observed, the amount of the resin remaining on the metal alloy side is smaller than that when the fracture is caused at room temperature. That is, the resin part is not torn off near the entrance to the recess, but simply indicates that many parts have been removed.

  Based on this inference result, when the inorganic filler is contained in the resin portion cured in the recess, the resin portion is difficult to come out of the recess, and the adhesive force can be improved. Furthermore, since there is a vertical recess (a recess having an inlet diameter smaller than the inner diameter) in the recess, if the resin in the recess contains a large amount of inorganic filler, the resin curing Objects cannot easily escape from the recess. The term “inorganic filler” as used herein means that it easily penetrates into the concave portion having a roughness on the order of microns, and the particle diameter must be at least 0.1 μm (100 nm) or less. Therefore, as defined in (2) above, an inorganic ultrafine filler was added.

  The present inventors set a target value of about 60 to 70 MPa (equivalent to the current commercially available adhesive) at room temperature as the shear breaking force of the joined body in which A7075 pieces are bonded together using an adhesive having dicyandiamide as a curing agent. At 100 ° C., the target value was 40 MPa or more (about 15 to 25 MPa for the current commercial adhesive). Further, the target value of the shear breaking force of the composite obtained by bonding the A7075 piece and the CFRP piece is 60 MPa or more at room temperature (the current commercially available adhesive is about 30 to 34 MPa in any of the methods of cocure and cobond). It was. In order to reach these target values, trial and error in which the composition ratio of the material composition was changed to produce an adhesive was repeated, and further, trial and error was repeated for the roughening method and bonding method of the CFRP piece. As a result, it came to show the shear fracture | rupture force exceeding the said target value.

[Metal alloy]
The type of metal alloy in the present invention, that is, a metal alloy having a surface structure based on the above-mentioned “NAT” theory is not particularly limited in theory. All metal species may be used, but what is actually meaningful is a hard and practical metal species or alloy species. That is, since mercury is naturally liquid, it is not relevant to the present invention, but soft metal species such as lead are also excluded from the metal species considered by the present inventors. Of course, alkali metal species and alkaline earth metal species (except for magnesium) that exist chemically but react actively in the atmosphere are also basically excluded.

  The present inventors consider that the metal alloy species to which the “NAT” theory can be applied substantially are alloy species mainly composed of aluminum, magnesium, copper, titanium, and iron. Hereinafter, these will be described. However, the “NAT” theory does not limit the metal species, and moreover, it does not limit the metal itself. It is not easy to simultaneously provide the three conditions of making the surface of a micron-order roughness, an ultra-fine irregular surface, and a high hardness with a non-metal as “NAT”. In short, “NAT” defines only the surface shape and the surface layer hardness and discusses the adhesion by the anchor effect theory, and is not limited to at least the following metal alloy types. Patent Document 7 describes an aluminum alloy. Patent Document 8 describes a magnesium alloy. Patent Document 9 describes a copper alloy. Patent Document 10 describes a titanium alloy. Patent Document 11 described stainless steel. Patent Document 12 describes general steel materials. These various metal alloys will be described in detail.

(Aluminum alloy)
The aluminum alloy that can be used in the present invention is not limited as long as it is an aluminum alloy. Specifically, all alloys such as A1000 series to 7000 series aluminum alloys for extension defined by Japanese Industrial Standards (JIS) (corrosion resistant aluminum alloy, high strength aluminum alloy, heat resistant aluminum alloy, etc.), and ADC1 Cast aluminum alloys such as ˜12 types (aluminum alloys for die casting) can be used. As the shape, if it is an alloy for casting or the like, it is possible to use a part shaped by a die-cast method, or a part that is further machined to adjust its shape. Moreover, in the alloy for extending | stretching, the board | plate material which is an intermediate material, etc., and the parts which shape | molded them by applying mechanical processing, such as hot press processing, can also be used.

(Magnesium alloy)
Magnesium alloys used in the present invention are AZ31B alloys of magnifying magnesium alloys defined by the International Standard Organization (ISO), Japanese Industrial Standards (JIS), American Material Testing Association (ASTM), etc., and castings such as AZ91D Magnesium alloy can be used. In the case of a magnesium alloy for castings, a part shaped by a method such as die casting or injection molding, or a part or structure whose shape is further processed by machining such as cutting or grinding can be used. Moreover, in the magnesium alloy for extending | stretching, the board | plate material etc. which are intermediate materials, and the components and structures which shape | molded them by applying plastic processing, such as warm press processing, can be used.

(Copper alloy)
The copper and copper alloy used in the present invention refer to copper, brass, phosphor bronze, Western night, aluminum bronze and the like. Copper developed for various uses including pure copper alloys such as C1020 and C1100, C2600 brass alloys, C5600 copper white alloys, and other iron-based connectors for connectors specified in Japanese Industrial Standards (JIS H 3000 series) All copper alloys etc., such as alloys, are the targets. These are intermediate parts such as plates, strips, pipes, bars, wires, etc., and parts that have been shaped by applying machining such as cutting and pressing, and forged parts.

(Titanium alloy)
The titanium alloy used in the present invention is a pure titanium alloy, α-type titanium alloy, β-type titanium alloy, α-β-type titanium alloy, etc. defined by the International Organization for Standardization (ISO), Japanese Industrial Standards (JIS), etc. All titanium alloys are targeted. Plates, rods, pipes, etc., which are intermediate materials of this titanium alloy, and those formed by machining such as cutting / grinding and pressing are used for parts and structures of various machines and devices. it can.

(Stainless steel)
The stainless steel referred to in the present invention is a Cr-based stainless steel obtained by adding chromium (Cr) to iron, a Cr-Ni-based stainless steel added by combining nickel (Ni) with chromium (Cr), and the like. A known corrosion-resistant iron alloy called stainless steel is the object. SUS405, SUS429, SUS403, and other Cr-based stainless steels standardized by the International Organization for Standardization (ISO), Japanese Industrial Standards (JIS), American Material Testing Association (ASTM), etc., SUS301, SUS304, SUS305, SUS316, etc. Cr-Ni type stainless steel.

(Steel)
The steel materials used in the present invention refer to steel materials such as carbon steels (so-called general steel materials) such as general structural rolled steel materials, high-tensile steels (high-tension steels), low-temperature steels, and reactor steel plates. Specifically, cold rolled steel (hereinafter referred to as “SPCC”), hot rolled steel (hereinafter referred to as “SPHC”), and hot rolled steel sheet for automobile structure (hereinafter referred to as “SAPH”). Used in the body and parts of various machines, such as hot-rolled high-tensile steel plates for automobile processing (hereinafter referred to as “SPFH”) and steel materials mainly used for machining (hereinafter referred to as “SS material”). Structural steel materials that are used are included. Since many of these steel materials can be pressed and cut, the structure and shape can be freely selected when they are used as parts and main bodies. The steel materials referred to in the present invention are not limited to the above steel materials, but include all steel materials standardized by Japanese Industrial Standards (JIS), International Organization for Standardization (ISO), and the like.

[Chemical etching of metal alloys]
The purpose of the chemical etching in the present invention is to generate a roughness on the order of microns on the surface of the metal alloy. There are various types of corrosion, such as general corrosion, pitting corrosion, and fatigue corrosion, but it is possible to select an appropriate etching agent by selecting a chemical species that causes general corrosion for the metal alloy and performing trial and error. According to literature records (for example, "Chemical Engineering Handbook (edited by Chemical Engineering Association)"), aluminum alloys are basic aqueous solutions, magnesium alloys are acidic aqueous solutions, stainless steel and general steel materials in general are hydrohalic acid such as hydrochloric acid, sulfurous acid, There is a record that the entire surface is corroded by an aqueous solution of sulfuric acid or a salt thereof. In addition, copper alloys with strong corrosion resistance can be totally corroded by oxidizing agents such as hydrogen peroxide that have been made strongly acidic, and titanium alloys can be corroded by special acids such as oxalic acid or hydrofluoric acid. And are often found in patent literature. The metal alloys that are actually sold in the market, such as pure copper-based copper alloys and pure titanium-based titanium alloys, have a purity of 99.9% or more and are hardly called alloys. Included in the alloy. In fact, most of the materials used in the world are mixed with a wide variety of other elements in order to obtain characteristic physical properties, and there are few pure metal materials, and they are substantially alloys.

  That is, most of the target metals alloyed from pure metals have improved corrosion resistance without degrading the original metal properties. Therefore, in the case of an alloy, there may be a case where a target chemical etching cannot be performed even if an acid base or a specific chemical substance applied with reference to the literature as described above is used. In short, the use of the acid-bases and specific chemicals described above is fundamental, and in practice, the concentration of the acid-base aqueous solution to be used, the liquid temperature, the immersion time, and in some cases, appropriate by trial and error while devising the additive Chemical etching is performed. Speaking of chemical etching, Patent Document 7 describes aluminum alloy, Patent Document 8 describes magnesium alloy, Patent Document 9 describes copper alloy, Patent Document 10 describes titanium alloy, Patent Document 11 relates to stainless steel. Description, Patent Document 12 describes general steel materials, Patent Document 13 describes aluminum plated steel sheets, and Patent Document 14 describes zinc-based plated steel sheets.

  To explain the points that are generally common as work actually performed, when a metal alloy shaped product is obtained, first, it is immersed in an aqueous solution in which a commercially available degreasing agent for each metal is dissolved and degreased and washed with water. This step is preferred and should always be performed because it removes most of the machine oil and finger grease deposited in the step of obtaining the metal alloy shape. Then, it is preferably immersed in a thinly diluted acid / base aqueous solution and washed with water. This is a process called the preliminary acid cleaning and preliminary base cleaning by the present inventors, and in the case of a metal species that corrodes with an acid such as a general steel material, it is immersed in a basic aqueous solution and washed with water. As described above, in the case of a metal species that is particularly rapidly corroded in a basic aqueous solution, it is immersed in a dilute acid aqueous solution and washed with water. These are processes in which a solution opposite to the aqueous solution used for chemical etching is attached (adsorbed) to the metal alloy in advance, and the subsequent chemical etching starts without an induction period, so that the reproducibility of the process is remarkably improved. . Therefore, the preliminary acid cleaning and preliminary base cleaning steps are not essential, but are preferably employed in practice. A chemical etching step is inserted after these steps.

[Fine etching / Surface hardening]
The purpose of fine etching in the present invention is to form ultra-fine irregularities on the surface of a metal alloy. Moreover, the surface hardening process in this invention aims at making the surface layer of a metal alloy into a thin layer of a metal oxide or a metal phosphate. Depending on the type of metal alloy, nano-order fine etching may be performed at the same time by performing the chemical etching, and ultra-fine irregularities may be formed. Furthermore, depending on the type of metal alloy, the natural oxide layer on the surface may be thicker than the original and the surface hardening process may be completed. For example, a pure titanium-based titanium alloy is only subjected to chemical etching, so that the surface has a roughness on the order of microns and ultra-fine irregularities are also formed. That is, fine etching is performed together with chemical etching. However, in many cases, it is necessary to perform fine etching or surface hardening treatment after forming a large uneven surface on the order of microns by chemical etching.

  Even at this time, we are often hit by unpredictable chemical phenomena. That is, when a metal alloy after chemical etching is reacted with an oxidizing agent or chemical conversion treatment for the purpose of surface hardening treatment or surface stabilization treatment, ultra fine irregularities may be formed on the resulting surface by chance. The surface layer that appears to be manganese oxide formed when a magnesium alloy is subjected to chemical conversion treatment with a potassium permanganate aqueous solution is a complex of rod-like crystals having a diameter of 5 to 10 nm that can be finally identified with a 100,000-fold electron microscope. This sample was analyzed by XRD (X-ray diffractometer), but diffraction lines derived from manganese oxides could not be detected. It is clear by XPS analysis that the surface is covered with manganese oxide. The reason why XRD could not be detected is that the crystal was a thin layer exceeding the detection limit. In short, the magnesium alloy was subjected to a chemical conversion treatment as a surface hardening treatment, so that fine etching was also completed. The same applies to copper alloys, and when surface hardening treatment was performed to change the surface to cupric oxide by oxidation under basic conditions, pure copper-based copper alloys had hole openings in the form of circular or circularly distorted surfaces. It occurs on one surface and becomes a unique ultra-fine uneven surface. A copper alloy that is not a pure copper type is not a concave shape, but is continuous with a particle having a diameter of 10 to 150 nm or an indefinite polygonal shape. Even in this case, most of the surface is covered with cupric oxide, and the hardening of the surface and the formation of ultrafine irregularities occur simultaneously.

  For general steel materials, although further verification is required, ultra-fine irregularities are often formed only by chemical etching to form micron-order roughness, and originally the surface layer (natural oxide layer) However, it was considered that the “NAT” theory can be applied without performing surface hardening treatment or fine etching again. The problem is that the corrosion resistance of the natural oxide layer is not sufficient, so that corrosion starts before the bonding process, or the adhesive force decreases in a short time depending on the environment after bonding.

  These can be prevented by chemical conversion treatment, but in practice, the durability of the adhesive is tested by performing tests such as applying the adhesive to a thermal shock test, leaving it in a general environment, and applying the coated product to a salt spray device. It is necessary to examine sex. For example, regarding a bonded body obtained by bonding steel materials not subjected to chemical conversion treatment (actually SPCC: cold rolled steel material) with a phenol resin adhesive, the adhesive strength rapidly decreased in a short period of 4 weeks. On the other hand, regarding the joined body in which the general steel materials (SPCC) subjected to the chemical conversion treatment were bonded to each other with the phenol resin-based adhesive, they did not decrease from the initial adhesive force in the same period.

  In addition, the present inventors have generally confirmed that when the thickness of a film (chemical conversion film) formed on the surface of a metal alloy by chemical conversion treatment is thick, the adhesive force often decreases. A strong adhesive force can be obtained when the thin layer is such that the diffraction line is not detected by XRD, such as the thin layer of manganese oxide adhered to the magnesium alloy. When metal alloys having a thick chemical conversion film are bonded to each other with an epoxy adhesive and subjected to a destructive test, the fracture surface is mostly between the metal phase and the chemical conversion film. In experiments conducted by the present inventors, the bonding force between the thick chemical conversion film and the cured epoxy adhesive was always stronger than the bonding force between the chemical conversion film and the internal metal alloy phase. That is, even with a general steel material, if the chemical conversion treatment time is further increased and the chemical conversion treatment layer is thickened, the durability of the adhesive (that is, the maintenance of adhesive strength) should be improved. However, if the chemical conversion film is thickened, the adhesive strength itself is lowered. Therefore, the degree of balance depends on the purpose of use and application. Hereinafter, the surface treatment method of various metal alloys will be described in detail.

(Surface treatment of aluminum alloy)
It is preferable that the aluminum alloy is first immersed in a degreasing tank to remove oils and oils adhered by machining or the like. Specifically, the degreasing treatment unique to the present invention is not necessary, and a warm aqueous solution in which a commercially available degreasing material for aluminum alloy is poured into hot water at a concentration specified by the drug manufacturer is prepared, immersed in this, and washed with water. It is preferable to do this. In short, a conventional degreasing treatment performed with an aluminum alloy may be used. Although it differs depending on the product of the degreasing material, in a general commercial product, the concentration is 5 to 10%, the liquid temperature is 50 to 80 ° C., and the immersion is performed for 5 to 10 minutes.

  Subsequent pretreatment steps differ in the treatment method between an alloy containing a relatively large amount of silicon in an aluminum alloy and an alloy containing few of these components. For alloys with low silicon content, ie, aluminum alloys for drawing such as A1050, A1100, A2014, A2024, A3003, A5052, and A7075, the following treatment methods are preferred. That is, it is preferable that the aluminum alloy is immersed in an acidic aqueous solution for a short time and washed with water, and the acid component is adsorbed on the surface layer of the aluminum alloy in order to proceed the next alkali etching with good reproducibility. This treatment may be referred to as a preliminary pickling step, but a dilute aqueous solution having a concentration of 1% to several percent of an inexpensive mineral acid such as nitric acid, hydrochloric acid, sulfuric acid or the like can be used. Next, it is immersed in a strongly basic aqueous solution, washed with water, and etched.

  By this etching, fats and oils remaining on the surface of the aluminum alloy are peeled off together with the surface layer of the aluminum alloy. Simultaneously with this peeling, the surface has a roughness on the micron level. That is, according to the JIS standard (JIS B 0601: '01, ISO 4287: '97 / ISO 1302: '02), the average interval between the valleys and valleys (RSm) is 0.8 to 10 μm, and the maximum height roughness (Rz) is The uneven surface is 0.2 to 5.0 μm. These numerical values are automatically calculated and output if applied to a recent scanning probe microscope. However, the numerical value when the fine unevenness is expressed by automatic output may not be the actual value of the calculated RSm value. In order to obtain a more accurate numerical value, it is necessary to reconfirm the RSm value by visually inspecting the roughness curve graph output by the scanning probe microscope with respect to the unevenness.

  If the roughness curve graph is visually inspected and the roughness is in the range of 0.2 to 5 μm with irregular intervals in the range of 0.2 to 20 μm, the average interval between the peaks and valleys (RSm = 0. 8 to 10 μm) and the maximum height roughness (Rz: 0.2 to 5.0 μm). This visual inspection method is preferable because it can be easily determined by visual inspection when it is determined that automatic calculation is not reliable. In short, in terms of technical terms defined in the present invention, a “surface with a roughness on the order of microns”. The working solution is preferably immersed in an aqueous caustic soda solution having a concentration of 1% to several percent at 30 to 40 ° C. for several minutes. Next, it is preferable to finish the pretreatment by removing the sodium ions by immersing again in an acidic aqueous solution and washing with water. The inventors refer to this as a neutralization step. As this acidic aqueous solution, a nitric acid aqueous solution having a concentration of several percent is particularly preferable.

  On the other hand, it is preferable to go through the following steps in casting aluminum alloys such as ADC10 and ADC12. That is, after the degreasing step of removing fats and oils from the surface of the aluminum alloy, it is preferable to carry out preliminary pickling and etching in the same manner as the above-described step. This etching results in a black smut in which the copper and silicon components that do not dissolve under strong basicity are fine particles (hereinafter, this contaminant is referred to as “smut” in the plating industry, and this expression is followed). Therefore, it is preferable to immerse the smut in an aqueous nitric acid solution having a concentration of several percent in order to dissolve and remove the smut. By immersion in an aqueous nitric acid solution, the copper smut is dissolved and the silicon smut floats from the aluminum alloy surface.

  In particular, if the alloy used is an alloy containing a large amount of silicon, such as ADC12, the silicon smut continues to adhere to the surface of the aluminum alloy substrate simply by dipping in an aqueous nitric acid solution, which cannot be completely peeled off. . Therefore, it is preferable that the silicon smut is then physically peeled off by immersing in an ultrasonic bath and ultrasonic cleaning. This does not remove all the smut, but it is sufficient for practical use. The pretreatment may be completed with this, but it is preferable to immerse again in a dilute nitric acid aqueous solution for a short time and wash with water. This completes the pretreatment. Since the pretreatment is completed by immersion in an acidic aqueous solution and washing with water, no sodium ions remain. Hereinafter, sodium ions will be described.

  From the experimental facts, the bonding strength when aluminum alloy plates are bonded to each other using an epoxy adhesive is almost determined by the roughness of the micron order and the shape characteristics of the nano-order ultra-fine irregularities on the surface. The From the experimental facts, if the immersion conditions are searched for by etching with an aqueous caustic soda solution, unexpectedly strong adhesive strength can be obtained if the conditions described in the “NAT” theory are met by chance. However, if the surface treatment is completed only by etching with caustic soda, sodium ions remain on the surface layer of the aluminum alloy even after sufficient washing with water. Sodium ions are easy to move because of their small particle size, and even after being painted or adhered, when the whole becomes wet, the remaining sodium ions are accompanied by water molecules penetrating the resin layer. Somehow, it gathers at the metal / resin interface and advances the oxidation of the aluminum surface.

  That is, corrosion of the aluminum alloy surface occurs, and as a result, peeling between the substrate and the coating film or adhesive is promoted. Under such circumstances, there is still no reason to perform etching with an aqueous caustic soda solution as an aluminum alloy pretreatment prior to bonding. Therefore, even today, it is strongly bonded to an aluminum alloy soaked in an aqueous solution of potassium dichromate or hexavalent chromium compound of chromic anhydride, or anodized and used unsealed. It is regarded as a standard pretreatment method for agent bonding. In short, before focusing on improving the adhesion by etching, the main focus was on preventing corrosion and alteration of the aluminum alloy surface.

  However, the method of caustic soda etching of an aluminum alloy is not completely used, and is often used in a pretreatment for painting. Normally, the coating does not require an extreme adhesive force, and it is based on the judgment that it will not be immersed in water unless it is used outdoors for wind and rain. In addition, this pre-painting method is not unreasonable unless the product has a coating film guarantee of 10 years. However, the present invention does not presuppose such an easy idea and makes long-term bonding stability an important issue. Therefore, the elimination of sodium ions is of paramount importance.

  The sodium (Na) contained in the aluminum alloy is also described. In the production method of aluminum metal, high purity aluminum compound is obtained by dissolving bauxite with an aqueous caustic soda solution, and aluminum ingot is produced by electrolytic reduction thereof. In this manufacturing method, it is inevitable that sodium is contained as an impurity in the aluminum metal. However, the current metallurgical technology can suppress the sodium content in the aluminum alloy to the limit. Therefore, in a normal environment where there is no acid-base mist, in the recent commercial aluminum alloys, corrosion does not proceed unless direct wetting (liquid water) coexists. In fact, corrosion proceeds at high speed when there is wetting, salt from the sea breeze (sodium chloride), and heating by sunlight. That is, when a commercially available aluminum alloy is used outdoors in a bad environment area, for example, a city located near the coast, in a strong sea breeze and in a high temperature area, the corrosion rate is high.

  As a countermeasure against corrosion, generally, the entire surface is coated with a paint, an adhesive or the like. At that time, it is necessary that cracks or the like are not generated in the coating film or adhesive layer, and it is important that salt-containing water does not enter the surface of the aluminum alloy from the cracks or the like. When such countermeasures are taken, it is not always necessary to use a general chromate treatment as a surface treatment for an aluminum alloy. If the coating film has good weather resistance and adhesion between the coating film and the substrate is good, coating It will last long enough even in a bad environment. In particular, recently, the use of hexavalent chromium is being rejected all over the world, and chromate treatment is not already a preferable aluminum alloy surface treatment method. On the other hand, at present, many paints excellent in weather resistance and adhesives excellent in moisture resistance and heat resistance are commercially available. Under these circumstances, the present inventors have attempted to optimize and theorize the conditions required on the aluminum alloy side in order to maintain a strong bond between the paint or adhesive and the aluminum alloy substrate for a long period of time. did.

  Specifically, the preferred roughness of the aluminum alloy surface is basically obtained by a strongly basic aqueous solution such as caustic soda, and thereafter sodium ions are removed by immersion in an acidic aqueous solution and sufficient water washing. However, when observed with an electron microscope, the microstructure of the surface of the aluminum alloy obtained by etching with a caustic soda solution has ultra-fine irregularities with a period of several tens of nanometers, and the surface on which the hardened adhesive is unlikely to escape from the concave portions of the substrate. In other words, the surface after the aluminum alloy was immersed in an aqueous nitric acid solution and washed with water was reduced in the quality level of the ultra-fine unevenness (the unevenness level). . In short, the immersion operation in an acidic aqueous solution for removing sodium ions is a kind of chemical polishing. Looking at the electron micrograph of the surface of the aluminum alloy after etching with an aqueous solution of caustic soda, it is a rough surface when viewed with microscopic eyes in terms of sensory expression. This rough surface is immersed in an acidic aqueous solution. In this case, the degree of roughness was reduced by chemical polishing, which had an adverse effect on adhesive bonding.

  Therefore, the roughness is recovered by fine etching described below. In short, the background, thought, and theory that the present inventors have made the present invention are based on the fact that a high-performance electron microscope capable of obtaining a high resolution of several nanometers can be easily used. In the present invention, the weather resistance and corrosion resistance of the aluminum alloy can be obtained by making the final aluminum alloy surface the aluminum oxide surface layer and by increasing the bonding strength of the adhesive to the alloy base to the maximum. It is the idea of trying.

  The aluminum alloy after the pretreatment is subjected to the following surface treatment, that is, fine etching, which is the final treatment. The pretreated aluminum alloy is preferably immersed in an aqueous solution containing one or more of hydrated hydrazine, ammonia, and a water-soluble amine compound, then washed with water and dried at 70 ° C. or lower. This is also a revival measure for the rough surface when the surface is slightly changed by the sodium removal ion treatment performed in the final treatment of the pretreatment and the roughness is maintained, but the surface becomes slightly smooth. It is immersed in a weakly basic aqueous solution such as a hydrated hydrazine aqueous solution for a short time and finely etched so that the surface is covered with an ultrafine uneven surface having a recess or protrusion having a diameter of 10 to 100 nm and an equivalent height or depth. To be precise, it is formed so that a large number of ultrafine irregularities with a period of 40 to 50 nm occupy on the inner wall surface of concaves and convexes on the order of microns. It is preferable to finish on a high surface.

  If the drying temperature after washing with water is, for example, 100 ° C. or higher, if the inside of the dryer is sealed, a hydroxylation reaction occurs between boiling water and aluminum, and the surface changes to form a boehmite layer. . This is not preferable because it cannot be said to be a strong surface layer. The humidity condition in the dryer is related not only to the size of the dryer and the state of ventilation, but also to the amount of aluminum alloy to be introduced. In that sense, hot air drying at 90 ° C. or lower, preferably 70 ° C. or lower, is preferred for obtaining good results with good reproducibility under any charging conditions to prevent surface boehmite formation. When dried at 70 ° C. or lower, only aluminum (trivalent) can be detected from the aluminum peak by surface elemental analysis by XPS, and aluminum (zero valent) that can be detected by XPS analysis of commercially available A5052, A7075 aluminum alloy sheet, etc. disappears. .

  The XPS analysis can detect elements present at a depth of 1 to 2 nm from the metal surface. From this result, it is immersed in an aqueous solution of hydrated hydrazine or an amine compound, and then washed with water and dried with warm air to obtain aluminum. It was found that the original natural oxide layer (a thin aluminum oxide layer having a thickness of about 1 nm) that the alloy had became thicker by fine etching. Since it was found that the layer had a thickness of 2 nm or more unlike at least the natural oxide layer, it was not further elucidated. That is, if XPS analysis is performed after etching with an argon ion beam or the like, analysis at a deeper position of about 10 to 100 nm is possible, but the valence of aluminum atoms in the deep layer may change due to the influence of the beam itself. The present inventors considered this analysis difficult at this time, and the present inventors stopped this consideration.

  The formation of an aluminum oxide layer on the surface of an aluminum alloy by another surface treatment method will be described. One surface treatment method for improving the weather resistance of aluminum alloys is an anodic oxidation method. When anodizing is performed on an aluminum alloy, an aluminum oxide layer having a thickness of several μm to several tens of μm can be formed, and weather resistance is greatly improved. An infinite number of holes having a diameter of about 20 to 40 nm are left in the aluminum oxide layer immediately after the anodizing treatment. In this state, that is, when the adhesive is joined or paint is applied in the unsealed alumite state, the adhesive or paint slightly enters the hole from the opening and solidifies, and exhibits a strong anchor effect. It is said that a strong bonding force is produced in the bonding. In fact, in assembling an aircraft, it is known that an anodized aluminum alloy is coated with an adhesive to join different materials.

However, the inventors have questioned this theory. That is, when a shear fracture test of an integrated product in which anodized aluminum alloys are firmly bonded with an epoxy adhesive is performed, according to the fracture test by the present inventors, a strong force of 40 MPa (40 N / mm ² ) or more is used. There was no broken sample, and when the fractured surface was viewed, the adhesive was not broken, and most of the anodized layer (aluminum oxide layer) was peeled off from the aluminum alloy substrate. According to the present inventors' consideration, "The metal side surface required for strong bonding must be a high-hardness layer of ceramic such as metal oxide, but its thickness should not be too thick. ". Although the surface layer of the anodic oxide is aluminum oxide and is an oxide of the base aluminum itself, the surface layer is ceramic and the base material is a metal, so they are foreign matter.

  If the ceramic material is thick, a difference in physical properties will always appear in the extreme state and it should break. Therefore, it is preferable that the metal oxide layer is thin, and based on common sense, it was considered that the metal oxide layer should be preferably bonded to the base material if it is an amorphous or microcrystalline ceramic material. That is, in order to increase the shear breaking force of the adhesive, the metal oxide layer should not be thickened unnecessarily, and the use of unsealed anodized anodized is not preferable.

  Hereinafter, the fine etching referred to in the present invention will be described in more detail. When immersed in an aqueous solution of hydrated hydrazine, ammonia, water-soluble amine or the like in a weakly basic aqueous solution with a pH of 9 to 10 for an appropriate temperature and for an appropriate period of time, the entire surface is an ultra-fine irregular shape with a diameter of 10 to 100 nm. It will be covered. The number average diameter is about 50 nm. In other words, the optimum pH, temperature, and time may be selected in order to obtain an ultra fine uneven shape with a diameter of 10 to 100 nm on the surface. It is empirically considered that the most preferable period of the ultra-fine irregularities predicted by the present inventors or the diameter of the ultra-fine irregularities is about 50 to 100 nm, particularly about 50 to 70 nm. The reason is that if the unevenness has a period of 10 nm, the unevenness is finer than the rough surface, and it is a smooth surface for the viscous adhesive, and if it is 100 nm or more, it is too rough for the rough surface to get caught. There is no image. Note that the “number average” in the present invention is not a total average that can be statistically verified, but an average value that is obtained by extracting up to 20 samples.

  The above-mentioned range of 50 to 70 nm is a numerical value estimated from many experimental results through trial and error. However, simply aiming for a period of 50 to 70 nm cannot be made such a disciplined chemical reaction and will vary. There is no choice but to digitize it by looking at a photograph taken with an electron microscope. According to the result, almost the entire surface is a concave portion having a diameter of 10 to 100 nm and an equivalent depth, or a convex portion having a diameter of 10 to 100 nm and an equivalent height. What is necessary is just to be the covered super fine uneven shape. As a result of the experiment, when the unevenness having a diameter of 10 to 20 nm occupies most of the surface, or conversely, the unevenness having a diameter of 100 nm or more occupies many, the bonding force was inferior. In the example described later, an example in which A7075 material or A5052 material is etched with an aqueous solution of hydrated hydrazine will be described.

  That is, in order to cover the aluminum alloy with the concave and convex portions having such a size, it is necessary to search for immersion conditions through trial and error in a number of experiments. Speaking of a 60% aqueous solution of hydrazine monohydrate at a concentration of 3.5%, it is optimal to immerse the A5052 and A7075 materials at an immersion time of about 2 minutes, and the surface by this immersion time has a diameter of 10 to 100 nm. In average, the entire surface is covered with a recess having a diameter of 40 to 50 nm. However, when immersed for 4 minutes, the diameter of the recesses expands to 80 to 200 nm, the number average value of the diameters of these recesses rapidly expands to exceed 100 nm diameter, and there are further recesses at the bottom of the recesses. Occurs and the structure becomes complicated. Further, when immersed for 8 minutes, the erosion of the horizontal hole progresses to become slightly sponge-like, and deeper recesses are connected to change into a valley or a canyon shape. When immersed for 16 minutes, it can be seen by visual observation that the aluminum alloy is slightly browned from the original metal color and the absorption of visible light begins to change.

  By the way, when the immersion time was 1 minute under the conditions described above, concave portions having a diameter of 10 to 40 nm were observed in the electron micrograph, and these number average diameters were concave portions having a diameter of 25 to 30 nm. Furthermore, when the immersion is performed for 0.5 minutes, the diameter of the concave portion covering the surface is 10 to 30 nm, and the number average diameter is about 25 nm, which is not much different from the case of the immersion time of 1 minute. And if you look closely at the electron micrographs of the immersion time of 0.5 minutes and the immersion time of 1 minute, the depth of the recess is clearly shallower than the one immersed for 1 minute. It was a state. In short, in A5052 and A7075 in weakly basic aqueous solution, for some reason, erosion started with a period of 20 to 25 nm. First, this formed a recess with a diameter of about 20 nm, and when the depth of this recess became the same level as the diameter, It was found that the edge of the recess was eroded to increase the diameter of the recess, and erosion in the indefinite direction inside the recess started. When so eroded, the simple and strong erosion condition most suitable for adhesive bonding is approximately 2 minutes when A7075 and A5052 are immersed in a 3-5% monohydric hydrazine aqueous solution (60 ° C.). Met.

  For example, a case where a one-component high-temperature curable epoxy adhesive “EP106 (manufactured by Cemedine Co., Ltd. (Tokyo, Japan)) having a viscosity of 40 Pa · sec at a temperature of 23 ° C. is described. According to the results of the adhesion experiment shown in the examples, in the case of an aluminum alloy material such as A7075 soaked in a hydrated hydrazine aqueous solution for 1 minute under the above conditions, the diameter of the ultrafine recesses was too small as about 25 nm on the number average, and epoxy. It seems that the resin hardly penetrates into the ultrafine recesses, and the adhesive strength when the immersion time is 2 minutes seems to be maximized. When A7075 or the like was immersed for 2 minutes under the above-mentioned conditions, the diameter of the ultrafine recess was about 40 nm in terms of number average diameter. It was estimated that it would be possible to pierce the head.

  In short, when the inner surface of the concave portion of the micron order is a rough surface having irregularities with a period of several tens of nanometers, the bonding force is increased. In addition, when the immersion time is longer than 2 minutes, for example, 4 minutes or 8 minutes, not only the diameter of the recesses is increased, but also recesses are formed in the recesses. Not only does the strength of the alloy surface layer itself weaken, but the adhesive cannot penetrate deeply into the complex holes. As a result, voids increase at the bonding boundary of the bonded article, and as a result, the bonding force decreases from the maximum value. In short, when the epoxy adhesive is used for an aluminum alloy such as A7075, in order to maximize the bonding force, in addition to setting the surface to a suitable roughness on the order of microns, the surface has a number average value of 40 to 40. It is preferable to cover with an ultrafine recess having a diameter of 50 nm, and it can be understood that the optimum immersion time range for making this ultrafine recess is very narrow. This is because the best joining result was obtained when the immersion time was around 2 minutes (approximately 1.5 to 3 minutes) as described above.

  When the same epoxy adhesive is used for the A5052 aluminum alloy, the dipping conditions during etching with an aqueous caustic soda solution are slightly different from those for A7075. This is probably because the erosion condition and the physical properties of the eroded surface are different.

  Ammonia water has a lower pH than an aqueous hydrazine solution, and when the aqueous solution is heated to a temperature higher than room temperature, volatilization of ammonia becomes intense. Therefore, the immersion treatment is performed at a high concentration and a low temperature, and the immersion time of 15 to 20 minutes is required even when the most concentrated ammonia water having a concentration of about 25% is used at room temperature. On the contrary, many water-soluble amines become a basic aqueous solution stronger than the hydrazine aqueous solution, so that the treatment takes a shorter time. In mass production processing, the stability of the work is lost if the immersion time is too long or too short. In that sense, hydrated hydrazine, which can have an optimum soaking time of several minutes, seems to be suitable for practical use.

  In any case, there was an alloy species that improved the bonding strength when immersed in an aqueous solution of hydrogen peroxide having a concentration of several percent after immersion in an aqueous solution of hydrated hydrazine, ammonia, or a water-soluble amine. The thickness of the metal oxide layer on the surface may have increased, but it was difficult to analyze for thicknesses of 2 nm or more and could not be solved theoretically.

(Surface treatment of magnesium alloy)
The magnesium alloy is preferably first immersed in a degreasing bath to remove oils and finger grease adhered by machining. Specifically, it is preferable that a commercially available degreased material for magnesium alloy is poured into hot water at a concentration specified by the drug manufacturer to prepare an aqueous solution and immersed in it, and then washed with water. In an ordinary commercial product, the concentration is generally 5 to 10%, the liquid temperature is 50 to 80 ° C., and the product is immersed in this for 5 to 10 minutes. Next, chemical etching in which the magnesium alloy is immersed in an acidic aqueous solution for a short time is performed and washed with water. The surface of the magnesium alloy is peeled off, including dirt that could not be removed in the degreasing process, and at the same time, the roughness on the order of microns, that is, the roughness according to the JIS standard (JISB0601: 2001 (ISO 4287)) measured by scanning probe microscopy. The surface has an uneven surface with an average length (RSm) of the curve of 0.8 to 10 μm and a maximum height roughness (Rz) of the roughness curve of 0.2 to 5 μm.

  The use solution for chemical etching performed above is preferably an aqueous solution of carboxylic acid or mineral acid having a concentration of 1% to several percent, particularly an aqueous solution of citric acid, malonic acid, acetic acid, nitric acid or the like. In chemical etching, aluminum and zinc contained in a magnesium alloy usually do not dissolve and remain on the surface of the magnesium alloy as a black smut. Then, the aluminum smut is removed by soaking in a weakly basic aqueous solution. It is preferable to dissolve the zinc smut by immersing it in a strong base aqueous solution.

  Thus, the so-called chemical conversion treatment is performed on the magnesium alloy from which the smut is dissolved and eliminated. That is, since magnesium is a metal with a very high ionization tendency, the oxidation rate due to moisture and oxygen in air is faster than other metals. Magnesium alloys have a natural oxide film, but are not strong enough in terms of corrosion resistance, and oxidative corrosion proceeds with water molecules and oxygen diffused through the natural oxide film even in a normal environment. Therefore, ordinary magnesium alloys are either immersed in an aqueous solution of chromic acid or potassium dichromate and covered with a thin layer of chromium oxide (called chromate treatment), or in an aqueous solution of manganese salt containing phosphoric acid. Immersion is performed, and the entire surface is covered with a manganese phosphate compound to perform corrosion prevention treatment. These treatments are called chemical treatments in the magnesium industry.

  In short, the chemical conversion treatment performed on the magnesium alloy is a treatment in which the magnesium alloy is immersed in an aqueous solution containing a metal salt and the surface thereof is covered with a thin layer of metal oxide and / or metal phosphate. At present, the chromate type chemical conversion treatment using a hexavalent chromium compound is avoided from the viewpoint of environmental pollution, and the chemical conversion treatment using a metal salt other than chromium, which is called non-chromate treatment, Manganese phosphate chemical conversion treatment or silicon chemical conversion treatment is performed. In the present invention, unlike these methods, it is particularly preferable to use a weakly acidic aqueous solution of potassium permanganate as an aqueous solution for chemical conversion treatment. In this case, a coating covering the surface (referred to as a chemical conversion coating) is manganese dioxide.

  As a specific treatment method, the magnesium alloy in which the smut is melted as described above is dipped in a very dilute acidic aqueous solution for a short time, and then washed with water to remove the basic component on the surface layer. The method of immersing in the aqueous solution for chemical conversion treatment after that, washing with water, and drying is preferable. As the dilute acidic aqueous solution, it is preferable to use a 0.1 to 0.3% aqueous solution of citric acid or malonic acid, and it is preferable to immerse at about room temperature for about 1 minute. As the chemical conversion treatment aqueous solution, it is preferable to use an aqueous solution containing 1.5 to 3% potassium permanganate, about 1% acetic acid and about 0.5% sodium acetate at a temperature of 40 to 50 ° C. In this aqueous solution, the immersion time is preferably about 1 minute. By these operations, the magnesium alloy is covered with a chemical conversion film of manganese dioxide, and the surface shape has a large roughness (roughness surface) on the order of microns, and when observed with an electron microscope, it is on the order of nanometers. There will be ultra-fine irregularities.

  FIGS. 3 (a) and 3 (b) are electron micrographs of ultra-fine irregularities with a magnification of 100,000 times, respectively. Although it is difficult to express these ultra-fine irregularities with a sentence expression, from an electron micrograph of FIG. 3 (a), a rod shape having a diameter of 5 to 20 nm and a length of 20 to 200 nm, or It can be said that the surface is covered with infinitely complex irregularities such as spherical objects. From the electron micrograph of FIG. 3 (b), this ultra-fine irregular shape is a rod-like shape having a diameter of 5 to 20 nm and a length of 10 to 30 nm, or a spherical object having a diameter of 80 to 120 nm with numerous spherical protrusions. However, the surface is shaped like an irregular stack. It should be said that the rod-like (needle-like) substance having a diameter of about 10 nm is completely crystalline in terms of electron microscope observation, but the diffraction line seen in the manganese oxide was not observed from the X-ray diffractometer (XRD). .

  X-ray diffractometers (XRD) cannot detect if the amount of crystals is small, so it is up to the inventor who is not a student of crystallography to determine whether or not these may be crystals. I do n’t know. At least, they are too shaped to be amorphous (non-crystalline), which cannot be said to be amorphous. From XPS analysis, large peaks of manganese (which is an ion and not zero-valent manganese) and oxygen are recognized, and there is no doubt that the surface layer is a manganese oxide. This surface has a dark color and is a manganese oxide mainly composed of manganese dioxide.

  In addition, the surface shape is quite different from the above, but the shape is a stack of particles with a diameter of 20 to 40 nm or indefinite polygonal shapes. In some cases, the shape covers almost the entire surface. In short, when a rod-like material having a diameter of 5 to 20 nm is not recognized, the shape is often like the surface of such a lava plateau, and the composition has a high aluminum content.

(Surface treatment of copper alloy)
It is preferable that the copper alloy is first immersed in a degreasing tank to remove oils and finger grease adhering by machining from the surface. Specifically, a commercially available degreasing material for copper alloy is poured into water at a concentration as specified by the drug manufacturer to prepare an aqueous solution, and it is preferably immersed in this and washed with water. An aqueous solution in which a degreasing agent for aluminum or the like, or a neutral detergent for industrial use or general household use is dissolved can also be used. Specifically, it is preferable to dissolve a commercially available degreasing agent or a neutral detergent in water at a concentration of several% to 5%, immerse at 50 to 70 ° C. for 5 to 10 minutes and wash with water.

  Next, it is preferable to perform preliminary base washing in which the copper alloy is immersed in an aqueous solution of several percent caustic soda kept at around 40 ° C. and then washed with water. Further, chemical etching is performed by immersing the copper alloy in an aqueous solution containing hydrogen peroxide and sulfuric acid, followed by washing with water. This chemical etching is preferably an aqueous solution containing several percent of both sulfuric acid and hydrogen peroxide at 20 ° C. to around room temperature. Although the immersion time at this time changes with alloy types, it is several minutes-20 minutes. In this chemical etching process, a preferable roughness on the order of microns for most copper alloys, that is, an average length (RSm) of a roughness curve according to JIS standard (JIS B 0601: 2001 (ISO4287)) analyzed by a scanning probe microscope. ) Is 0.8 to 10 μm, and the maximum height roughness (Rz) is 0.2 to 10 μm. Preferably, the maximum height roughness (Rz) is 0.2 to 5 μm.

  However, as can be said particularly with pure copper-based copper alloys, the rough surface obtained as a result of the above-mentioned chemical etching often has an irregularity period of 10 μm or more, and the average value, RSm, is a copper alloy other than pure copper-based. Big in comparison. On the other hand, the unevenness height difference is small for the large RSm. In particular, it is obvious that the metal crystal grain size is large, such as C1020 (oxygen-free copper) having a high copper content, and clearly gives a large roughness curve as described above. It was estimated that there was a direct correlation between the crystal grain size and the metal crystal grain size. It is presumed that not only pure copper-based alloys but also chemical etching performed with various alloys are mostly caused by erosion starting from the grain boundaries. In any case, even if there are irregularities with a micron order period, if the height difference of the irregularities is small for the period, the effect of the present invention is hardly exhibited. Therefore, although it will be described later, it is preferable to carry out an appropriate treatment method for those that feel that the roughness of the large unevenness is insufficient.

  The copper alloy that has undergone the chemical etching step is oxidized. A method called blackening treatment is known in the electronic component industry, but the oxidation performed in the present invention is the same in the process itself although the purpose and the degree of oxidation are different. Chemically speaking, the surface layer of the copper alloy is oxidized with an oxidizing agent under strong basicity. When copper atoms are ionized with an oxidizing agent, if the surroundings are strongly basic, they are not dissolved in an aqueous solution and become black cupric oxide. When copper alloy parts are used as heat sinks or heat-generating parts, the surface is blackened to increase the efficiency of heat dissipation and heat absorption, but this process is used in the electronic parts industry that uses copper. This is called blackening treatment. This blackening treatment method can also be used for the surface treatment of the present invention. However, the purpose of this blackening treatment is to form nano-order ultra-fine irregularities on the surface of a copper alloy having a certain roughness and to harden the surface layer (that is, to perform fine etching and surface hardening treatment). Therefore, it is not literally blackening.

  Commercially available blackening agents can be used at concentrations and temperatures specified by commercial manufacturers, but the immersion time in that case is much shorter than during so-called blackening. Actually, the immersion time is adjusted by observing the obtained alloy with an electron microscope. As a specific example, it is preferable to use an aqueous solution containing about 5% sodium chlorite and 5 to 10% caustic soda at 60 to 70 ° C, and the immersion time in this case is about 0.5 to 1.0 minutes. Is preferred. By these operations, the copper alloy is covered with a thin layer of cupric oxide, and a rough surface having a roughness on the order of microns is formed on the surface. A circular hole having a diameter of 10 to 150 nm or an elliptical hole having a major axis or a minor axis of 10 to 150 nm is formed.

  The hole opening which is this circular hole or an elliptical hole has an ultra-fine uneven shape existing on the entire surface with a period of 30 to 300 nm (this example is shown in the photograph of FIG. 4). In short, when this surface hardening treatment is performed, both the formation of ultra-fine irregularities and the surface hardened layer can be obtained simultaneously. In addition, it has been found that the surface hardening treatment is excessively performed by increasing the immersion time in the above-described treatment solution by 2 to 3 minutes, but it is not preferable because the bonding force is weakened.

  In the etching of the pure copper-based copper alloy described above, it is a sure pattern that copper erosion occurs from the metal crystal grain boundary based on the observation results, and as described above, a particularly large crystal grain size, that is, oxygen-free copper (C1020 ), It was not possible to exert a strong bonding force only by performing the above-described chemical etching and surface hardening treatment. In short, the most important size of the recess is not as expected.

  The present inventors have discovered a treatment method in such a case. The result is a very simple method, but once the surface hardening treatment (blackening) has been completed, it is again immersed in an etching solution for a short time to re-etch and then blackened again. is there. As a result, the period of the roughness on the order of microns is as expected as being close to 10 μm or less, and the appearance of the ultra-fine irregularities is different from the case of no repeated treatment according to the electron microscope observation. Absent.

(Titanium alloy surface treatment)
It is preferable that the titanium alloy is first immersed in a degreasing tank to remove oils and finger grease adhered by machining. No special products are required. Specifically, general degreasing agents such as commercially available iron degreasing agents, stainless steel degreasing agents, aluminum alloy degreasing materials, magnesium alloy degreasing agents, etc. are designated by the drug manufacturer. It is preferable to prepare an aqueous solution by pouring it into hot water at a normal concentration, and immerse in this to wash. Furthermore, it is also preferable to prepare an aqueous solution with a concentration of several percent with a commercially available industrial neutral detergent, soak it at a temperature of about 60 ° C., and then wash it with water. Next, it is preferable to immerse in a basic aqueous solution and wash with water, followed by preliminary base cleaning.

  Next, it is preferable to perform chemical etching by dipping in an aqueous solution of a reducing acid. Specifically, oxalic acid, sulfuric acid, hydrofluoric acid, and the like can be said to be reducing acids that can corrode titanium alloys entirely, and these can be used. In terms of efficiency, hydrofluoric acid has the highest etching rate. However, hydrofluoric acid may invade human skin and lead to bones, and deep pain may continue for several days. In short, there are problems different from hydrochloric acid and the like, and it is preferable to avoid using this acid from the viewpoint of the working environment.

  Preference is given to ammonium hydrofluoride, a half-neutralized product of hydrofluoric acid which can be handled much more safely than hydrofluoric acid. A treatment method in which an aqueous solution of about 1% of 1 hydrogen difluoride ammonium is immersed in this solution at a temperature of 50 to 60 ° C. for several minutes and then washed with water is preferable. Chemical etching with 1 hydrogen difluoride ammonium aqueous solution was performed to obtain micron-order roughness (roughness surface), but in electron microscope observation and observation with the latest analytical equipment, titanium was washed and dried after chemical etching. It was found that the surface of the alloy became a mysteriously shaped ultra-fine uneven shape, and the surface was covered with a thin titanium oxide layer. In short, it seems that surface treatment such as special fine etching and surface hardening treatment is unnecessary and may not be performed.

  An analysis example of a titanium alloy etched with an aqueous solution of 1 hydrogen difluoride ammonium, washed with water, and then dried is shown. First, a scanning analysis result by a scanning probe microscope was obtained. Here, scanning within a square area of 20 μm square, the average length of the roughness curve (average length of the contour curve element) RSm is 1.8 μm, and the maximum height roughness (maximum height of the contour curve) Rz. 0.9μ was obtained. Moreover, the example of the 10,000 times and 100,000 times electron micrograph of the thing which carried out the same process was shown to Fig.8 (a), (b). Here, a very unique and mysterious ultra-fine concavo-convex shape having a height or width of 10 to 300 nm and a length of 10 nm or more, or a mountain or mountain range (mountain) -like convex part having a period of 10 to 350 nm and existing on the entire surface. It has been shown.

  According to XPS analysis, large oxygen and titanium peaks were obtained, and the surface compound was clearly titanium oxide. However, the surface color tone was dark brown, and it was seen as a thin film of titanium (trivalent) oxide or a mixed oxide of titanium (trivalent) and titanium (tetravalent). That is, the surface was a metal color before etching, and this surface was a natural oxidation layer of titanium, but after etching with an aqueous hydrogen bifluoride solution, it changed to a dark titanium oxide layer that was not a natural oxidation layer. This titanium oxide layer was etched by 10 to several tens of nm with an argon ion beam, and the etched surface was subjected to XPS analysis. This XPS analysis revealed the thickness of the titanium oxide layer, which is clearly thicker than that of the natural oxide layer, and more than 50 nm for pure titanium-based titanium alloy etched products using an aqueous 1 hydrogen difluoride ammonium fluoride solution. It was seen.

  Moreover, the valence of titanium ions decreases from the surface to the inside, the divalence increases from the tetravalent or trivalent and tetravalent mixed state of the surface toward the inside, and further the divalent decreases to zero. It turns out that it leads to metal. In short, the oxide film that is titanium oxide is not a simple titanium oxide layer, but a continuously changing layer in which the titanium valence continuously decreases from the surface and reaches zero. It can be seen that the surface is an interesting continuously changing layer that becomes darker and thinner towards the interior, as if penetrated from the surface. In such a metal oxide film, there is no clear boundary between the metal phase, so the bonding force between the oxide film layer and the metal substrate is very strong, and there is no concern about its peel-off resistance (stress). You can expect nothing to do.

  The specific treatment method for titanium alloys other than pure titanium alloys is the same as the treatment method described above, but is included as a small amount of additive by the nascent hydrogen gas generated during etching with a reducing strong acid aqueous solution. Other metals may be reduced to produce insoluble matter, so-called smut. Most of the smut can be dissolved and removed by immersing in a nitric acid aqueous solution having a concentration of several percent. However, depending on the alloy, a smut that does not dissolve in the nitric acid aqueous solution may also be generated. In such a case, it is preferable to wash by applying ultrasonic waves when washing with water.

  The surface shape of an alloy other than a pure titanium-based titanium alloy etched with ammonium monohydrogen difluoride and smut-removed is a surface shape that makes it difficult to express the surface shape in a language compared to the photograph in FIG. Become. An example of an α-β type titanium alloy containing aluminum is shown in the photograph of FIG. Here, a beautiful slope of a mountain or hill that does not have ultra-fine irregularities (similar to FIG. 8), which is typical of a titanium alloy, is also observed, but a mysterious shape like a dead leaf of a plant was observed. The entire surface is not covered with ultrafine irregularities having a period of 10 to 300 nm, which is preferable as the second condition described above, but a surface with a longer period (called “fine irregularities”) is observed. The unevenness itself was smooth.

  However, apart from the smooth dome-shaped portion in this surface, the dead leaf shape portion is thin and curved, and if it has hardness, it becomes a strong spike shape. The surface of the α-β type titanium alloy has almost no portion that does not meet the above-mentioned second condition (ultra-fine irregularities with a period of 5 nm to 500 nm) in the NAT theory. It is thought that it can play the role of unevenness. Since the surface spike shape is large, it is also related to the micron-order roughness (surface roughness) required under the first condition required by NAT. Roughness satisfying the first condition (mountain valley average interval (RSm): 0.8 to 10 μm, maximum height roughness (Rz): 0.2 to 5 μm) as seen with a scanning probe microscope by this spike shape. A surface is formed. In addition, since it slightly deviates from the second condition and the concavo-convex period is large, the whole surface image cannot be grasped with an electron micrograph of 100,000 times. The surface was observed by taking a magnification photograph of 10,000 times or less. That is, as shown in FIG. 9 (a), an area of at least a 10 μm square or more is viewed with a 10,000 × electron microscope. By doing so, a fine uneven shape in which both a smooth dome shape and a curved dead leaf shape are present is observed.

(Stainless steel surface treatment)
Since various stainless steels have been developed to improve corrosion resistance, chemical resistance is clearly recorded. There are various types of corrosion, such as general corrosion, pitting corrosion, fatigue corrosion, etc., but it is possible to select an appropriate etching agent by selecting a chemical species that causes general corrosion and performing trial and error. According to literature records (eg "Chemical Engineering Handbook", 6th edition, edited by Chemical Engineering Society, Maruzen (1999)), stainless steel in general is hydrohalic acid such as hydrochloric acid, sulfurous acid, sulfuric acid, metal halide salts, etc. There is a record that the entire surface is corroded with an aqueous solution of The remaining weakness of stainless steel, which is corrosion resistant to many chemicals, is that it is corroded by halides, but the weakness is reduced in stainless steel with reduced carbon content, stainless steel with molybdenum added, etc. Yes.

  However, basically, the above-mentioned aqueous solution causes overall corrosion, so the immersion conditions may be changed depending on the type of stainless steel. Furthermore, a structure whose hardness is reduced by annealing or the like and structurally speaking has a large metal crystal grain size has fewer crystal grain boundaries, and it is difficult to corrode the entire surface to obtain unevenness on the order of microns. In such a case, it is necessary to devise such as adding some additive without changing the immersion condition to a level where the corrosion proceeds, and the etching does not progress to the intended level. In any case, chemical etching is performed for the purpose of occupying most of the roughness surface on the order of microns.

  Specifically, a special degreasing agent is not required, and a commercially available general stainless steel degreasing agent, iron degreasing agent, aluminum alloy degreasing agent, or a commercially available neutral detergent is generally used. Obtain and make an aqueous solution at a temperature of 40-70 ° C. at a concentration of several percent or as indicated in the instructions of the degreasing agent manufacturer, and immerse the stainless steel to be treated for 5-10 minutes. To do. This is a degreasing process. Next, it is preferable to immerse this stainless steel in a caustic soda aqueous solution having a concentration of several percent for a short time, and then wash it with water to adsorb basic ions on this surface. This is because the next chemical etching proceeds with good reproducibility by this operation. This is a so-called preliminary base washing step. Next, the etching process is started.

  In the case of SUS304, a method in which a sulfuric acid aqueous solution having a concentration of about 10% is set to a temperature of 60 to 70 ° C. and is immersed in the solution for several minutes is preferable. In SUS316, it is preferable to immerse an aqueous sulfuric acid solution having a concentration of about 10% at a temperature of 60 to 70 ° C. for 5 to 10 minutes. Hydrohalic acid, such as aqueous hydrochloric acid, is also suitable for etching, but if this aqueous solution is heated to high temperatures, part of the acid may volatilize and corrode surrounding iron structures. Some processing is necessary. In that sense, use of a sulfuric acid aqueous solution is preferable in terms of cost. However, depending on the steel material, the progress of overall corrosion may be too slow with an aqueous solution of sulfuric acid alone. In such a case, it is effective to add hydrohalic acid to the sulfuric acid aqueous solution for etching.

  After the chemical etching, the surface of the stainless steel is naturally oxidized and returned to the surface layer that can withstand corrosion by washing thoroughly with water, so that it is not necessary to perform a hardening process. However, in order to make the metal oxide layer on the stainless steel surface thick and strong, an oxidizing acid, for example, an oxidizing agent such as nitric acid, that is, nitric acid, hydrogen peroxide, potassium permanganate, sodium chlorate, etc. It is also preferable to wash it after immersing it in an aqueous solution.

  It is preferable to select a material having a high bonding strength through an epoxy adhesive bonding test, and then observe the same material with an electron microscope to confirm the presence or absence of an ultra-fine uneven shape. Of course, the injection bonding test may be performed after observation with an electron microscope. In any case, a stainless steel having a fine structure surface in which an ultra fine unevenness having a period of several tens to hundreds of nanometers, preferably an ultrafine unevenness having a period of about 50 nm should surely have a high injection joining force. is there. As described above, the present inventors have already confirmed these with a magnesium alloy, an aluminum alloy, a copper alloy, and a titanium alloy.

  An example in which stainless steel is actually chemically etched with a sulfuric acid aqueous solution is shown. The above-mentioned roughness surface (surface roughness surface) is obtained by appropriate etching, and this roughness surface can be confirmed by observation using a roughness meter (surface roughness meter), a scanning probe microscope, etc. Furthermore, when the surface is observed with an electron microscope, it can be seen that the surface is covered with a very interesting surface having an extremely fine uneven shape. In short, in stainless steel, fine etching can be achieved at the same time by only chemical etching as described above. This surface will be described with an electron micrograph. In FIG. 10, a shape in which particles having a diameter of 20 to 70 nm, indefinite polygonal shapes, and the like are stacked is recognized, and this 10,000 times photograph (FIG. 10A) and 100,000 times photograph (FIG. 10B). The observation photograph of) was very similar to the gala field on the slope of the lava plateau formed by lava flowing around the volcano.

  In addition, when XPS analysis was performed on stainless steel covered with the ultra-fine irregularities on the etched surface, large peaks of oxygen and iron and small peaks of nickel, chromium, carbon, and molybdenum were recognized. In short, the surface was an oxide of a metal having exactly the same composition as that of ordinary stainless steel, and was considered to be covered with a similar corrosion-resistant surface. Here, the importance of taking a chemical etching method will be described. Whatever the method, it is only necessary to obtain the above-mentioned surface shape as expected, but the reason is chemical etching. Because it is thought that if you use a high-level ultra-fine processing method that is applied using a photochemical resist and visible light, ultraviolet rays in the present invention, etc., the designed ultra-fine uneven surface can be realized. is there.

  However, there are reasons why chemical etching is particularly preferred for injection joining, other than being easy to operate. In other words, when chemical etching is performed under appropriate conditions, not only can an appropriate concavo-convex cycle and an appropriate depth of the recess be obtained, but the fine shape of the resulting recess is not a simple shape, and many of the recesses are understructured. Because it becomes. The under structure as used in the present invention means that there is a surface that cannot be seen when the concave portion is viewed from the vertical plane, and an overhang portion is visible when it is assumed that the concave portion is viewed with a microscopic eye. That's what it means. It can be easily understood that an under structure is necessary for injection joining.

  In addition, after etching with the reducing acid aqueous solution, it was immersed in an aqueous nitric acid solution, an aqueous hydrogen peroxide solution, etc., and additional processing was performed to make a metal oxide layer firmly. There was no clear difference in the joining force when joining by the addition of this additional treatment. Long-term weather resistance tests may result in differences in bonding strength.

(Surface treatment of steel materials)
There are known types of corrosion of steel materials such as general corrosion, pitting corrosion, fatigue corrosion, and the like, but it is possible to select an appropriate etching agent by selecting a chemical type that causes general corrosion and trial and error. According to the records of various documents (for example, “Chemical Engineering Handbook (edited by the Chemical Engineering Association)”), all steel materials are corroded by an aqueous solution of hydrohalic acid such as hydrochloric acid, sulfurous acid, sulfuric acid, and their salts. Is described. Depending on the amount of carbon, chromium, vanadium, molybdenum, and other small additives added, the corrosion rate and form of corrosion change, but basically the above-mentioned aqueous solution causes general corrosion. Therefore, basically, the immersion conditions may be changed depending on the type of steel material.

  Specifically, in the steel materials that are commercially available and often used such as SPCC, SPHC, SAPH, SPFH, SS material, etc., a degreasing agent that is commercially available for this steel material, degreasing for stainless steel Agents, aluminum alloy degreasing agents, and further commercially available neutral detergents, and the concentration of aqueous solution as indicated in the instructions of these degreasing agent manufacturers, or an aqueous solution of several percent concentration, After this temperature is set to 40 to 70 ° C. and immersed for 5 to 10 minutes, this is washed with water (degreasing step). Next, in order to improve etching reproducibility, it is preferable to immerse in a dilute caustic soda aqueous solution for a short time, and then wash it with water. This processing step is, so to speak, a preliminary base washing step.

  Next, in the case of SPCC, it is preferable to etch by immersing the sulfuric acid aqueous solution of about 10% concentration at 50 ° C. for several minutes. This is an etching process for obtaining a micron-order roughness. For SPHC, SAPH, SPFH, and SS materials, it is preferable that the temperature of the sulfuric acid aqueous solution is increased by 10 to 20 ° C. from the former. Hydrohalic acid, such as aqueous hydrochloric acid, is also suitable for etching, but if this aqueous solution is used, part of the acid may volatilize and corrode surrounding iron structures, and even if it is exhausted locally, it will be exhausted. Some processing is required. In that sense, use of a sulfuric acid aqueous solution is preferable in terms of cost.

[Surface Treatment Method I: Method of Forced Drying after Washing with Water]
After the chemical etching described above, it is washed with water, dried, and observed with an electron micrograph. Ultra fine irregularities with a height and depth of 50 to 500 nm and a width of several hundred to several thousand nm followed by infinite steps. Often, the shape covers almost the entire surface. This seems to have exposed the pearlite structure that steel materials generally have. Specifically, when an aqueous sulfuric acid solution is used in the above chemical etching process under appropriate conditions, an uneven surface corresponding to a large undulation is obtained, and at the same time, a surface having a fine and mysterious step-like ultra-fine uneven shape is also obtained. Often formed simultaneously. Thus, when the roughness of micron order and the creation of ultra-fine irregularities are made at once, the water after the etching is sufficiently washed and then drained and rapidly dried at a temperature of 90-100 ° C. or higher. You can use it as it is. Rust on the surface does not appear and it becomes a beautiful natural oxide layer.

  However, the natural oxidation layer alone is considered to have insufficient corrosion resistance in a general environment, particularly in a high humidity and warm environment as in Japan. Perhaps it is necessary to store it under dry conditions for the bonding process, and it is questionable whether the bonded composite can maintain the bonding strength (adhesive strength) for a sufficient amount of time. Actually, after leaving for a month in a place with a roof but practically close to the outdoors (Suehiro-cho, Ota City, Gunma Prefecture, Japan, December 2006-January 2007), when a break test was performed, the bonding strength was slightly reduced. Was. In practice, it seems that a clear surface stabilization treatment is necessary.

[Surface Treatment Method II: Method Utilizing Adsorption of Amine-Based Molecules]
After the above chemical etching, the substrate is washed with water, and subsequently immersed in an aqueous solution of ammonia, hydrazine, or a water-soluble amine compound, washed with water, and dried. It has been found that amine-based substances in a broad sense such as ammonia remain in the steel material after the etching process. Strictly speaking, nitrogen atoms are confirmed when the steel material after drying is analyzed by XPS. Therefore, we understood that amines in a broad sense, including ammonia and hydrazine, were chemically adsorbed on the surface of steel materials. Since it appears to be attached, an iron-based complex of iron may have occurred.

  More specifically, the 100,000 times electron micrographs of the steel material immersed in aqueous ammonia and the steel material immersed in the hydrazine aqueous solution appear to differ in the shape of the thin skin substance adhering to the staircase. Looks like. In any case, the adsorption or reaction of these amines seems to prevail over the adsorption of water molecules or the iron hydroxide formation reaction. In that sense, at least for several days to several weeks until the joining operation with the epoxy adhesive is performed, generation of rust due to moisture adsorption and reaction thereof can be suppressed. In addition, it is expected that the adhesion strength after adhesion is superior to the above-mentioned “Surface Treatment Method I”. There was no decrease in bonding strength when the bonded article was left for 4 weeks.

  The concentration and temperature of the aqueous ammonia, the aqueous hydrazine solution, or the aqueous solution of the water-soluble amine to be used need almost no strict conditions. Specifically, an effect can be obtained by using an aqueous solution having a concentration of 0.5 to several percent at room temperature, immersing for 0.5 to several minutes, washing with water, and drying. Industrially, a 1% to several percent aqueous solution of hydrated hydrazine having a slight odor but inexpensive and having a concentration of about 1%, or a low odor and stable effect is preferable.

[Surface treatment method III: method by chemical conversion treatment]
After the chemical etching described above, the surface of the steel material is subjected to chromium oxidation by rinsing with an aqueous solution of an acid or salt containing a hexavalent chromium compound, a permanganate, or a zinc phosphate-based compound. It is known that corrosion resistance is improved by being covered with metal oxides such as metal oxides, manganese oxides and zinc phosphorus oxides, and metal phosphorus oxides. This is a well-known method for improving the corrosion resistance of iron alloys and steel materials, and this method can also be used. However, the true purpose is not to ensure corrosion resistance that can be said to be perfect in practical use, and at least there will be no hindrance until the bonding process. If this is done, the level should be such that it is difficult to cause trouble over time in the bonded portion. In short, when the chemical conversion film is thickened, it may be preferable from the viewpoint of corrosion resistance, but it is not preferable in terms of bonding strength. Although the chemical conversion film is necessary, it is the view of the present inventors that the bonding force is weakened if it is too thick.

  The specific methods for implementing corrosion resistance can be extended. When immersed in a dilute aqueous solution of chromium trioxide in a chemical conversion treatment solution, washed with water and dried, the surface appears to be covered with chromium (III) oxide. The surface was not covered with a uniform film-like object, and protrusions having a diameter of 10 to 30 nm and an equivalent height were generated at a distance of about 100 nm. Also, an aqueous solution of potassium permanganate having a concentration of several percent adjusted to weak acidity could be preferably used.

  Moreover, the electron micrograph of the surface which carried out the chemical conversion treatment which immerses SPCC in the zinc phosphate type aqueous solution was taken. The shape was such that foreign matter mainly adhered to the vicinity of the stepped corner, and the flat portion of the step was dotted with small protrusions having a diameter of 10 to 30 nm although the density was low. In any case, it is preferable to obtain an aqueous solution at a temperature of 45 to 60 ° C., soak the SPCC for 0.5 to several minutes, wash with water, and dry to obtain a high bonding strength. Therefore, the chemical conversion film is thin. The change due to the chemical conversion treatment agent described above was not something that could be confirmed by a 10,000 × low electron micrograph.

[Surface Treatment Method IV: Silane Coupling Agent]
Numerous inventions have been made and proposed as treatment methods for imparting corrosion resistance and weather resistance to steel materials, and methods for adsorbing a silane coupling agent therein are known. A silane coupling agent is a compound having a hydrophilic group and a water repellent group in its molecule. When a steel material is immersed in a dilute aqueous solution, washed with water and dried, a silane cup is formed on the surface of the hydrophilic steel material. The hydrophilic base side of the ring agent is adsorbed, and as a result, the entire steel material is covered with the water repellent base side of the silane coupling agent. When an epoxy adhesive is allowed to act with the silane coupling agent adsorbed, even if water molecules enter the very thin gap of several tens of nanometers created by the hardened adhesive and the steel material surface, The water-repellent group of the silane coupling agent covering the water may suppress the water molecules from approaching the steel material.

  These can be expected to have better corrosion resistance than the surface treatment method I as in the surface treatment method II and surface treatment method III described above, but a long-term test is necessary to demonstrate this. In a short-term durability experiment conducted by the present inventors, at least one of the above-mentioned surface treatment method I, surface treatment method II, surface treatment method III, and surface treatment method IV is used. After joining, the fracture data (shear fracture data) after about one week (January 2007: indoors with roof in Ota City, Gunma, Japan) was almost the same strength as the initial, but after four weeks The surface treatment I deteriorated. Longer neglect tests will reveal which method is most practical. However, from a practical standpoint, steel materials are generally used by painting, and it will be necessary to select candidates in the non-painted material test and then apply the paint for a long-term environmental test.

[One-part epoxy adhesive]
In joining based on the NAT theory, it is desirable to use a one-component thermosetting adhesive. This is because the gelation of the adhesive molecules does not progress during the pre-curing operation such as coating and subsequent soaking, and the adhesive molecules sufficiently penetrate into the irregularities having a micron-order roughness on the surface of the metal alloy. This is because adhesive molecules can penetrate into ultra-fine irregularities to some extent. That is, it is required that the adhesive is not gelled when entering. Although there is no progress of gelation at normal temperature, gelation and solidification progresses at a high temperature, and the one-pack thermosetting adhesive plays the role of an adhesive. It functions as a liquid thermosetting adhesive when a material other than aliphatic amines is used as the curing agent. Specifically, there are dicyandiamide, imidazoles, and aromatic diamines included in amine compounds in a broad sense, and phenol resins and acid anhydrides also have curing ability. However, although acid anhydride has a slow gelation rate at room temperature, it is not zero, and is usually classified as two-component.

  Even if it is a two-component thermosetting adhesive, the use of a surface-treated metal alloy according to the present invention improves the bonding strength, but in many cases compared to the case of using a one-component thermosetting adhesive. Therefore, the bonding force is greatly inferior. Most two-component thermosetting adhesives begin to gel from the moment the hardener component is added to the main liquid and mixed, and the resin component penetrates into the ultra-fine irregularities due to the rapid gelation. Decrease or disappear.

  In short, when a two-component thermosetting adhesive is used, the adhesive force often changes depending on the elapsed time after mixing the curing agent, which may be inferior in stability and reproducibility. However, like an epoxy adhesive with an acid anhydride as a curing agent, even if it is generally a two-component thermosetting adhesive, the time until gelation begins is long, When the work was carried out skillfully, high adhesive strength was obtained. Thus, even if it is the epoxy adhesive which uses an acid anhydride for the hardening agent normally made into 2 liquid property, the epoxy type which uses the alicyclic polyamines made into 2 liquid property similarly as a hardening agent Even if it is an adhesive agent, there is also a type in which the gelation rate at room temperature after being added to and mixed with the epoxy resin is considerably slow. These are only classified as two-component because the curing rate at room temperature is not zero and they cannot be marketed as one-component thermosetting adhesives. However, in the present invention, it is only necessary to apply to the metal alloy that has been surface-treated within a few hours after mixing the curing agent, and then the adhesive molecules to penetrate into the ultra-fine irregularities before the soaking and treatment. Any gelation at such a low speed that does not hinder this is acceptable. That is, even if the adhesive is generally classified as two-component, if it can slow down the gelation rate, it can be treated as one-component in the present invention. It functions as a one-component thermosetting adhesive.

(Composition of 1-component epoxy adhesive)
An outline of the epoxy adhesive will be described. The epoxy adhesive is composed of an epoxy resin, a curing agent, and an inorganic filler. Although the adhesive itself has a commercial item, the raw material can be easily obtained from the market. As the epoxy resin, commercially available bisphenol type epoxy resins, polyfunctional polyphenol type epoxy resins, alicyclic epoxy resins and the like are commercially available. In addition, various polyfunctional epoxy resins in which an epoxy group is bonded to a polyfunctional compound (for example, a polyfunctional compound or oligomer having a plurality of hydroxyl groups or amino groups) are commercially available. Usually, these are used by mixing them appropriately. In ordinary commercial adhesives, the majority of all epoxy resins are liquid and low viscosity bisphenol A type epoxy resin monomer types. Add a multimeric form of bisphenol-type epoxy resin with a large molecular weight to give quickness, add a phenol-type epoxy resin to give heat resistance, and add a polyfunctional compound with an epoxy group to gain strength. Is normal. Also in the present invention, an epoxy resin was prepared based on this basic composition.

(Inorganic filler)
The filler will be described. The adhesive typically includes an inorganic filler, which plays an important role. In other words, according to the current fracture theory, local fracture occurs first in the minute part in the stress concentration area or in the weak intensity area in the vicinity of the stress concentration area before the object breaks. We think that the stress concentration of the part is increased and the chain proceeds to the local fracture chain. This chain of local destruction expands, the size of the fractured portion becomes smaller and eventually becomes a large crack, which eventually leads to complete destruction, that is, peeling. Actually, the strength of the cured adhesive is not uniform as a whole, and there is always strength. Therefore, if breaks are easily chained, the local breakage is almost complete, and the complete breakage is determined only by the strength value at a microscopically weak part. Therefore, even if the local breakage of the weakest minute part occurs, if this is not linked, the incident does not occur until the next local breakage occurs in the weakest minute part, and as a result, the adhesive force is improved. The current fracture theory is that the presence of an inorganic filler having a diameter of several μm to several tens of μm is very effective in stopping local fracture even if it occurs locally.

  Therefore, the structural adhesive always includes an inorganic filler. Commercially available epoxy adhesives usually contain several percent or more of powders of silica, clay (clay, kaolin), talc, alumina, etc. having a particle size of several μm to several tens of μm. The details of the inorganic filler to be added affect the adhesive performance and are not usually disclosed by the adhesive manufacturer. The present inventors used clay and talc from which fine powder can be purchased from the market.

  A method for producing an epoxy-based adhesive is to add a filler to the above-mentioned epoxy resin mixture, mix and disperse it, and then add a curing agent component and knead. The present invention is particularly characterized by the filler. Components necessary as the filler are (1) an inorganic filler having a particle size distribution center of 5 to 20 μm. Specifically, it is a product obtained by classifying powders such as talc, clay (clay, kaolin), calcium carbonate, silica, and glass. These inorganic fillers are usually used in structural adhesives and have a function of preventing the early microcracking of the cured adhesive from being linked to chain breakage.

(Ultra fine inorganic filler)
In the present invention, (2) addition of an ultrafine inorganic filler having a particle size of 100 nm or less is necessary. This addition is effective for improving the heat resistance of the adhesive. Specifically, fumed silica is preferably used, and the amount used is preferably 0.3 to 3.0% by mass of the adhesive. When this is added, it also penetrates into the concave portion on the micron order roughness on the metal alloy, and when it is placed under high temperature and the hardness of the resin content in the cured adhesive is lowered, that is, the spike effect in the concave portion. In the case of lowering, there is an effect of keeping the shape of the cured adhesive in the concave portion so that the cured adhesive cannot easily come out. For this reason, no effect is observed when used at room temperature. Therefore, if it is not used at high temperature, or if there is no actual harm as a product even if the adhesive strength is reduced at high temperature, there is not much meaning to add it, but there is a possibility of raising the temperature to 80-100 ° C in practical products Should always be considered, the addition of ultrafine inorganic fillers plays a very important role. Hereinafter, the basis for adding the ultrafine inorganic filler will be described in detail.

  With respect to the adhesive according to the present invention, the addition of an ultrafine inorganic filler is extremely important. If the cured adhesive in the micron-order recesses becomes soft at high temperatures and the spike grip loosens and comes off, the effect of the spike will disappear if the slip at this microinterface progresses along the interface. The anchor effect you have is zero. As a result, the degree of stress concentration on the concave group around the concave portion increases, and the same thing occurs next in the peripheral concave portion. Eventually, the cured adhesive will come out of the micron-order recesses and float, leading to breakage. However, most of existing inorganic fillers with a particle size of several μm or more can be placed in the concave portions with a roughness of micron order existing on the surface of metal alloys that have been surface-treated based on the NAT theory. Therefore, it does not contribute to the improvement of the adhesive strength at the interface. Therefore, the filler that contributes to improving the adhesive strength at the interface is an ultrafine filler that can enter a recess of about 1 μm, and specifically has a particle size of 0.1 μm (100 nm) or less. In particular, at 100 ° C., the adhesive force can be improved by 10 to 30 MPa as compared with an adhesive not containing an ultrafine inorganic filler.

  Even if it is going to maintain the hardness strength of the adhesive hardened | cured material which touches the spike, since the resin hardness falls under high temperature, it has to rely on a filler. However, since the period of the ultra-fine irregularities is usually on the order of several tens of nanometers, an ultra-fine filler with a diameter of several nanometers is required. However, at present, it is difficult to obtain an ultrafine powder having a diameter of several nm, and even if it can be obtained, it will be difficult to uniformly disperse it in the adhesive. Therefore, it is assumed that the slip progresses in the vicinity of the spike, the effect of the spike disappears, and the adhesive cured product convex portion in the micron order concave portion has already floated about several tens of nm. A schematic diagram of this situation is shown in FIG.

  In this case, in order to prevent the chain from being transmitted to the surrounding micron-order recesses, the floating distance does not exceed several tens of nanometers but stops within a certain range. The condition is that the concave shape is an under shape and the opening is narrower than the internal diameter, or that the cured adhesive that is contained in the concave portion on the metal alloy side does not collapse as a whole and the shape is maintained. is there. The recess formed on the surface of the metal alloy due to the surface treatment based on the NAT theory is not a simple hemispherical shape or V-shaped groove, that is, a bowl-shaped recess or an opening direction of the recess is narrower than the inside. There is a so-called under-shaped recess having a certain probability that it is not a vertical direction but an oblique direction. When an adhesive in which an ultrafine filler having a particle size of several tens to several hundreds of nanometers penetrates into such under-shaped recesses and solidifies, the cured adhesive present in these recesses can be easily obtained. Will not break into pieces.

  For example, when an intense peeling force in the vertical direction is applied, the cured polymer in the adhesive is slightly softened at a high temperature, and the effectiveness of the spike is reduced. Therefore, in the micron order concave portion where the strongest force is applied in the vicinity of the stress concentration point, the polymer portion in contact with the inner wall surface spike slips and the effect of the spike is lost. If such a recess has the above-described under shape, the cured adhesive in the recess is unfixed and floats by several tens of nm. That is, if the concave portion has an under structure, it only stops floating and does not come off unless the central portion of the cured adhesive in the concave portion is largely broken.

  FIG. 16 schematically shows the joint surface just before the breakage, where 50 is a metal alloy phase, 51 is a ceramic phase, 52 is a cured adhesive phase, and 53 is a space formed by peeling. Of the five micron-order recesses arranged side by side, only the three recesses in the central portion are in a state where the anchor does not work, and are in a shape that floats several tens of nm. However, since the entire cured adhesive is softened at a high temperature, it is somewhat elastic and the two recesses at the end in the figure are not lifted by being dragged to the center three. That is, even if the effect of the spike disappears and the destruction phenomenon occurs in the three recesses, it is the hypothesis of the present inventors that it is difficult to proceed to the chain destruction once it stops at this level of destruction.

  In other words, even if the anchor effect is lost in the weakest part of the infinite number of micron-order recesses, about tens of nanometers are kept floating, and the next weak part leads to local destruction. It is also the idea that adhesion can be maintained. The filler to be added according to this hypothesis was an ultrafine inorganic filler of 100 nm or less. It is based on the idea that if they enter the micron-order recess, the hardness at that portion is maintained, and even if the spike function is somewhat lowered, it will not easily come out of the recess. Fumed silica is easily available as an ultrafine inorganic filler having a particle size of 100 nm or less.

  These ultrafine inorganic powders are essential fillers for the present invention. There are two types of fumed silica. One is ultra-fine fused silica recovered from the exhaust gas in the reduction process that uses silica (silicon oxide) sand as a raw material to obtain metallic silicon. The other is vaporized and combusted silicon tetrachloride to form ultrafine fused silica, which is commercially available under the trademark “Aerosil”. Aerosil that has been surface-treated is also commercially available, and the present inventors have used a hydrophobic treatment. The fumed silica obtained by the combustion treatment is not necessarily highly hydrophilic, but the hydrophobic treatment is considered to have better affinity with the epoxy resin.

  Normally, powders with particle sizes smaller than micron order are agglomerated, and Aerosil is actually an agglomerated product. The agglomeration force becomes stronger as the powder becomes ultrafine powder, and the agglomeration cannot be solved and the dispersed state assumed in the present invention cannot be achieved as long as it is put into an adhesive and kneaded in an automatic mortar. Therefore, it is necessary to apply to a disperser after addition to the epoxy resin. This will be described later. From the experimental results, the filling rate of the ultrafine inorganic filler is preferably 0.3% by mass or more, particularly preferably 0.3 to 3.0% by mass. When it added exceeding 3.0 mass%, not only became a viscosity high and it was difficult to use, but when it was used, the adhesive force leveled off or fell.

(Thermoplastic resin powder)
In the present invention, an elastomer component is preferably added as a filler. Various vulcanized rubbers, powder rubbers modified on the surface of various vulcanized rubbers, various raw rubbers, modified rubbers modified from various raw rubbers, vinyl chloride resin (hereinafter “PVC”), vinyl acetate resin (hereinafter “PVA”), polyvinyl formal Resin (hereinafter “PVF”), ethylene vinyl acetate resin (hereinafter “EVA”), polyolefin resin, polyethylene terephthalate resin (hereinafter “PET”), various polyamide resins (hereinafter “PA”), polyethersulfone resin (hereinafter referred to as “PET”) "PES"), polyurethane resin, thermoplastic polyester elastomer (hereinafter "TPEE"), thermoplastic polyurethane elastomer (hereinafter "TPU"), thermoplastic polyamide elastomer (hereinafter "TPA"), thermoplastic polyolefin elastomer (hereinafter "TPO"). )) Etc. are elastomer components as referred to in the present invention. .

  Some of these are not usually elastomers, but the cured epoxy resin is hard and the thermoplastic resin is soft. These increase the toughness of the cured product due to its softness. Preferably, these are blended as fine powder having a particle size of 5 to 25 μm, and further, the surface is modified to a parent epoxy resin mold. Since it is an amino group or a hydroxyl group that reacts with the epoxy resin at a high temperature, it is an effective modification treatment to have these at the end of the elastomer. Moreover, since the present invention seeks an adhesive that exhibits a strong adhesive force not only at room temperature but also at a slightly high temperature, an excessively soft material is not preferred. Taking these into account, those that are readily available include PVF that is prone to hydroxyl groups, urethane resins with hydroxyl groups at the ends, PAs with countless amino groups, and PES with intentionally hydroxyl groups. is there.

  The inventors of the present invention have come to the conclusion that, by trial and error, it is effective to add (3) a thermoplastic resin powder, particularly a powder having a particle size distribution center of 5 to 25 μm as a filler. . Compared with a cured epoxy resin having a three-dimensional bond, it is soft and easily deformed, so that the adhesive itself can be made elastic. If the metal alloy side and the adherend side are highly rigid, this addition is less necessary, but since the adhesive strength is strong, when a strong external force is applied, the metal alloy or coating is concentrated due to stress concentration. The dressing itself is deformed. In such a case, if the adhesive layer is elastic, the external force level leading to breakage is improved. Specifically, it is considered that hard vulcanized rubber powder is suitable as a filler, but it is difficult to obtain a particle size of about 10 μm with such a material. Some thermoplastic resins can be produced at this level of fine powder, so they can be selected from the group. SBR, NBR (nitrile rubber), urethane resin, and other soft thermoplastic resins (including thermoplastic elastomers) are commercially available for use in electronic parts and elastic coatings. These are suitable. Also, as the main application of the adhesive composite of metal alloy and CFRP, a thermoplastic resin having a level of elasticity that does not excessively soften at a high temperature of about 100 to 150 ° C. is suitable because it is a structure of a mobile machine. Yes. In this respect, a polyethersulfone resin (“PES”) having a high softening point is preferable. PES has a use as a heat-resistant elastic paint, and since fine pulverization is industrially performed, a product having a particle size distribution center of 10 to 20 μm can be easily obtained. A preferable addition amount of the thermoplastic resin powder is 2 to 5% by mass.

(Addition of carbon nanotubes)
Furthermore, it is also effective to add (4) carbon nanotubes (hereinafter referred to as “CNT”) as a filler. As shown in Patent Document 15, this has the effect of increasing the adhesive strength at room temperature, and the effect of addition becomes unclear at high temperatures. When the fibrous CNT dispersed near the opening of the concave portion on the surface of the metal alloy in the order of micron order is torn off the hardened adhesive near the opening of the concave portion with a strong external force, it is pulled. It is thought to suppress shredding. In order for CNTs to be present in the vicinity of the entrance of the recess, the CNTs are required to be fibrous materials having a diameter of 100 nm or less and dispersed in the adhesive. In other words, it can be said that CNT is most suitable as a fibrous material having a diameter of 100 nm that can be dispersed.

  For the above reason, if the diameter of CNT is about 100 nm or less, a sufficient effect should be expected, and the effect can be expected for all CNTs from a single layer, a two-layer, a three-layer to MCNT. Here, thin CNTs with a small number of layers, for example, those having a diameter of 10 nm or less, can also pass through the recesses of the ultra-fine uneven surface on the inner wall surface of the recess. Therefore, it is estimated that there may be some effect as compared with the case where it does not pass through the concave portion of the ultra fine uneven portion. However, the greatest influence on the adhesive strength in the bonding theory is the breaking strength in the vicinity of the opening of the concave portion related to the roughness on the order of microns, and the CNT may penetrate into the concave portion of the ultra-fine unevenness. However, it has not yet reached the idea of helping to improve the bonding force.

  The present inventors tried dispersion experiments on CNTs having average diameters of about 80 nm, about 50 nm, and about 3 nm. As a result, it was only when the average diameters were 80 nm and 50 nm that the fracture dispersion into the epoxy adhesive was successful. As will be described later, CNTs having an average diameter of 3 nm did not reach sufficient dispersion by the fracture dispersion method performed by the present inventors, and an adhesion experiment could not be performed. In addition, when 0.05 to 0.06% by weight of CNT having an average diameter of 80 nm is added to the epoxy adhesive and dispersed sufficiently, the shear breaking force is improved as compared with the case where it is not added. A certain effect was recognized. The same effect was observed when the average diameter was 50 nm. These effects were in a range that could be said to be almost the same, but a more excellent effect was observed on slightly thin CNTs (that is, those having an average diameter of 50 nm).

  According to the results of a one-component epoxy adhesive experiment in which CNTs having an average diameter of 50 nm and 80 nm were added, when the CNT content was 0.1% by weight or more, there was no effect or the adhesive strength was lowered. If the CNT content is high, the CNTs are in the form of fibers, so it overlaps in the vicinity of the openings of the recesses with a roughness on the order of microns and looks like filter paper. Or, it overlaps in the vicinity of the opening of the concave portion and becomes like a filter paper, and the CNT density locally increases in that portion, and it is expected that it becomes a destruction base at the time of the tensile test. When such a surface is taken into consideration, CNT is an ultrafine fibrous material, and thus it seems that the effect is likely to be obtained with a content of less than 0.1% by weight.

  In summary, in the present invention, the blending of CNTs into the epoxy adhesive is aimed at sufficiently infiltrating and solidifying the CNTs into the concave portions with micron-order irregularities. In other words, the reinforcing fiber added to the one-component epoxy adhesive needs to be uniformly dispersed in the adhesive even in a fine range of 1 μm or less. Thus, it can be said that the aim is to match the mechanical properties of the fine part with the overall mechanical properties.

(Dispersion method of carbon nanotube)
The strengthening of the adhesive force by adding CNTs described above is based on the premise that CNTs can be well dispersed in the adhesive, but there is a situation that the dispersion is actually difficult. Many techniques have already been introduced for the dispersion method of CNTs. Many of these dispersion methods employ a means in which CNT, a special solvent, and a special dispersant are introduced into a ball mill or the like to break and disperse the CNT in the solvent. This is due to the fact that the CNTs immediately after manufacture are found to be finely entangled and must be destroyed to some extent in order to be dispersed.

  However, in this method, a solvent and a dispersing agent suitable for CNT dispersion are selected, and the solvent and the like cannot be completely removed after the adhesive composition and the dispersed CNT are mixed. That is, the solvent component newly added to the adhesive composition may reduce the adhesive performance. In fact, the present inventors also obtained several kinds of solvents and several kinds of dispersion stabilizers used in this method, and conducted experiments by mixing them with a one-component epoxy adhesive. As a result, the adhesive strength decreased in all cases.

  However, recently, a new CNT fracture dispersion method has been proposed. This is a physical method that uses a high-speed shearing disperser and a media mill, which is a high-performance crushing disperser, in series. By introducing only epoxy adhesive and CNT, a CNT fracture dispersion is obtained. (Patent Document 16). Therefore, the present inventors also referred to the present invention which attempts to disperse CNT without using a solvent or a dispersant.

  However, in the present invention, a high-speed shearing type disperser (homogenizer) was not used. The inventors of the present invention have determined that the most significant contribution to the fracture dispersion of CNTs was the use of the latest media mill, specifically the sand grind mill, the latest wet grinder. Then, when the destructive dispersion of several kinds of CNTs having different diameters was tested in a solvent or an epoxy resin, the multi-layer CNT (hereinafter referred to as “MCNT”) having an average diameter of several tens of nanometers can be broken and dispersed. It was found that fracture dispersion of nm diameter CNTs was not possible. Since such CNTs are thin and flexible, they were considered to be unbreakable and untangled even when using these latest wet pulverizers.

  The addition of CNT is summarized. The CNT that can be used for improving the adhesive force is a multi-layer CNT having a diameter of several tens of nanometers. At present, the CNT itself supplied from the CNT manufacturer is in an entangled and aggregated state, so it cannot be dispersed in a fiber form even when added to an epoxy resin and kneaded. The inventors of the present invention used a state-of-the-art wet pulverizer for crushing and dispersing. However, even if this method was used, CNTs with a diameter of a few nm could not be crushed and dispersed because of their flexibility, and only the above-mentioned multilayer CNTs could be dispersed. The filling amount is preferably 0.02 to 0.2% by mass. If it is less than this, the effect is not clear, and if it is more than this, the adhesive strength is lowered.

(Wet grinder)
When dispersing (1), (2), (3), and (4), it is preferable to use a wet pulverizer with a base material of an epoxy resin without a curing agent. (4) The use of the latest wet pulverizer is a necessary condition for the dispersion of CNT, but the dispersion of other (1), (2) and (3) is not a requirement for the use of a wet pulverizer. The inventors performed all the dispersion of the filler with the latest type of sand grind mill. We have not investigated what kind of performance can be achieved with an automatic mortar or kneader used in normal adhesive production. However, even if a sand grind mill is used, the filler is already a fine powder having a diameter of several tens of μm or less, and there is little possibility of further grinding. This sand grind mill promotes dispersion for large fine powders, and disperses and disperses ultrafine powders. Therefore, it is not necessary to use a wet pulverizer except for CNT, but when using a wet pulverizer to disperse at least (1) (2) (3) Good dispersion is possible.

  In this way, it is preferable to add a curing agent and knead after the filler is added and dispersed in the epoxy resin. The reason is that when the filler is added and dispersed with a sand grind mill, the heat generated in the grinding chamber is intense. Even if the cooling water is circulated through the crushing chamber jacket and cooled, if an epoxy resin containing a curing agent is used to add and disperse the filler, a hot spot can be formed with a slight cooling delay and gelation occurs at that location. At first, heat is generated more and more and the sand is hardened in the grinding chamber. This is because there is a risk of making the expensive sand grind mill unusable.

[Roughening of CFRP shapes]
FRP whose reinforcing fiber is carbon fiber is CFRP, the one using glass fiber is GFRP (abbreviation of Glass-Fiber Reinforced Plastics), and the one using aramid fiber is AFRP (abbreviation of Aramid-Fiber Reinforced Plastics) And KFRP (Kevlar-Fiber Reinforced Plastics). FRP is also a generic name for these. Although the present invention discusses FRP using an epoxy resin as a matrix resin, CFRP is generally used as the FRP using an epoxy resin as a matrix resin.

  In general, the shaped CFRP is a product obtained by heat-curing a multilayer CFRP prepreg while being compressed by an overlapping jig or the like. In particular, a prepreg utilization method is standard as a high-strength CFRP production method, which will be described. Past CFRP prepregs used a sticky liquid thermosetting epoxy resin similar to the current adhesive for the matrix resin. Therefore, it is a sticky sheet and is supplied as a sheet sandwiched between polyethylene films or the like, and is cut as it is in use, and then the polyethylene film is peeled off before use. However, the current prepreg is a non-adhesive sheet because it sometimes uses a large amount of aromatic diamine as a curing agent to increase the heat resistance of the cured product. The thickness is often about 0.2 mm and is standardized and easy to use.

  The manufacturing process of CFRP shaped objects is automated so that the three-dimensional shape becomes the expected one by cutting the prepregs while changing the shape one by one with a computer-controlled automatic cutting machine, and stacking the cut objects Yes. The laminate is placed in a jig so that the shape can be maintained, and then tightened with bolts or springs so that pressure is applied between the prepreg sheets, and the whole is put in a sealed bag or autoclave and sealed to make a vacuum. When the temperature is raised in a vacuum, it once melts, and then gelation and curing begin. On the contrary, if the pressure is increased after melting, the gap where the air that has escaped from between the prepregs is crushed and the integration proceeds. When curing is completed, the product is allowed to cool, and a jig or the like is removed to complete a CFRP shaped product.

  Since the surface of the CFRP shaped product is covered with a cured product of the matrix resin, the CFRP shaped product itself can be said to be a cured epoxy resin when viewed from the surface. It can be bonded even if it is applied with an epoxy adhesive, but since the adherend is a stable material that has already been sufficiently cured, it is expected to have a chemical affinity between the CFRP surface and the epoxy adhesive. Is a little impossible. Therefore, the present inventors have studied to adopt a method of increasing the adhesive force by roughening the surface by a physical method and allowing an epoxy adhesive to enter the finished uneven surface. Since it is difficult to make the CFRP shaped object surface a physically ideal adherend shaped object like the metal alloy surface satisfying the first to third conditions described above, it is physically rough. Even if it is made, it is not possible to expect high strength adhesion equivalent to the case where metal alloys are bonded to each other. Therefore, if the adhesive strength is to be equal to that of a metal alloy bonded body, there is no choice but to expect some chemical effect.

  Therefore, we focused on matrix resin. The matrix resin is a reaction-cured product of an amine compound (curing agent) and an epoxy resin, but is usually prepared with an excess of the curing agent in order to obtain stable performance. Therefore, excess amines remain in the cured product. In short, in addition to the physical effect of roughening the CFRP shaped product, it is certain that the primary amino group linked to the amine molecule or polymer is exposed on the roughened surface. It can be done. Based on this reasoning, the present inventors first scraped the surface of the CFRP shaped article with coarse abrasive papers of 80-240. After scraping, the shavings and dirt were removed, washed with pure water or an organic solvent, and dried. An epoxy adhesive was simply applied to the surface. Since the curing system of the adhesive used is also an amine compound (dicyandiamide, imidazoles or aromatic diamines) in a broad sense, it is completely the same as the amino group exposed from the surface of the CFRP shaped product. Therefore, it was speculated that the surface of the CFRP shaped object was renewed and cleaned without problems. Although a soaking treatment after application is necessary, it is not necessary to add a new chemical treatment to the rough surface of the CFRP shaped object.

  Based on the above idea, trial and error were performed and the following conclusions were reached. There is no need to be concerned with the method described below, and any method can be used as long as it is roughened, removed, dried, coated with an adhesive, soaked and treated. As a specific method performed by the present inventors, it is carefully scraped off with coarse abrasive paper of about 80 to 240, washed with a neutral or weakly basic surfactant aqueous solution, and sufficiently washed with water. It dried at 80-100 degreeC. Next, an adhesive coating / dipping process described later is performed. As a trial and error, experiments were also conducted to remove and clean with an organic solvent, but there was no particularly good effect compared to the former, and it seemed that these should not be adopted for safety and cost reasons.

  Furthermore, in order to make the process after roughening the surface which should be adhere | attached large sized CFRP shaped object, the method which does not need to be immersed in a water tank etc. was examined. In this case, a method in which an aqueous solution in which a surfactant is dissolved is applied as a high-pressure water to a rough surface is effective. Of course, it is necessary to wash with water after that. Furthermore, when tap water (Ota City, Gunma Prefecture, pH 5.8 to 6.1) was sprayed as a high-pressure high-speed fountain flow for 1 minute or more, it was found that there was almost the same effect as when immersed in a water tank or the like.

[Applying and dyeing adhesives]
The above-described epoxy adhesive is applied to predetermined portions of the surface-treated metal alloy piece and the roughened CFRP shaped product. Brush painting or spatula painting may be used. Then, put both in a vacuum vessel or pressure vessel preheated to 40 to 50 ° C., leave it for a few minutes, reduce the pressure to about several tens of mmHg for a few seconds, then add air and return to normal pressure It is preferable to set the pressure under atmospheric pressure or several tens of atmospheric pressure. The reason why the coated material is warmed is to make the viscosity of the adhesive 10 or less Pa seconds or less. The higher this temperature is, the lower the viscosity is. However, if the temperature is too high, the gelation rate increases, which is disadvantageous for securing the adhesive force. This point depends on how to predict the gelation temperature of the adhesive. Then, it is preferable to repeat the cycle of pressure reduction and pressure increase. The air between the adhesive and the metal alloy escapes under reduced pressure, and the adhesive easily enters the ultrafine recesses on the surface of the metal alloy when returned to normal pressure.

  In actual mass production, using high-pressure air using a pressure vessel leads to increased costs both in terms of equipment and costs. Therefore, use a highly airtight bag or vacuum vessel to reduce pressure / normal pressure. It is economical to perform the return several times. It is preferable to take it out from the container or bag, put it in a storage place at a temperature below room temperature, and enter the next step within a short time. If the CFRP shaped object is a large product and there is no large container for storing it, a jig with a hemispherical shape and a rubber pad shaped peripheral part is created and used by sucking it onto the surface of the CFRP shaped object. That is, a vent and a valve are attached to the top of the hemisphere and connected to a vacuum pump. If it is necessary to raise the temperature, it is better to warm it with a hair dryer before applying the adhesive.

[Adhesion process]
The metal alloy piece and CFRP shape object which apply | coated the epoxy-type adhesive agent by the said process are obtained. Tie these together and fasten them with clips. If the clip cannot be fixed, make a jig that applies pressure to the bonding surface and fix it. When storing and fixing in a jig or the like without using a clip, gravity, a spring, a clamp, or the like is used as the pressing force. Then, in a fixed state, it is put into a hot air dryer and cured by heating. The temperature was first set at about 90 ° C. for 15 to 30 minutes and leveled, then raised to 120 to 135 ° C. and heated for 40 to 60 minutes, further raised to 165 ° C. and heated for 30 to 60 minutes. This temperature condition is a condition in which curing proceeds sufficiently when the curing agent is dicyandiamide or imidazoles.

  When using a two-part epoxy adhesive with a slow curing alicyclic polyamine as a curing agent, within 1 hour if the coating, soaking, and processing after adding the curing agent can be advanced well, Even if it is delayed, it must be soaked within several hours to finish the process. After that, even if the gelation is somewhat advanced, the metal alloy and the CFRP shaped object can be bonded and fixed. If it can proceed smoothly until it is fixed, the subsequent operation is easy. These adhesives can be completely cured at 80 to 100 ° C. for 5 to 2 hours. At such a high temperature, local heating with a hot blaster or a band heater is possible, so a large autoclave or hot air dryer is not necessarily required.

[Measurement example of adhesive strength]
A method for measuring the adhesive strength of a composite of a metal alloy and CFRP used in an experimental example to be described later will be described. FIG. 14 shows the shape of an adhesive complex of a metal alloy piece 31 and a CFRP piece 32 which is an example of a CFRP shaped object. A test piece 30 for measuring adhesive strength obtained by joining a metal alloy piece and a CFRP piece with an epoxy adhesive is shown. The hatched portion in the figure is the adhesion range 33. Both ends of this test piece were pulled and broken with a tensile tester, and the obtained breaking force was divided by the adhesion area to measure the shear breaking force (Kgf / cm 2, MPa).

  The bonding technique between the metal alloy and the FRP according to the present inventor can be a basic technique applicable to many fields. According to the present invention, a metal alloy and CFRP can be strongly bonded to each other. CFRP is an advanced material that is ultralight and exhibits the same strength as steel. The main structure of the component is CFRP, and a metal alloy can be bonded and bonded only to the end. That is, the portion that is extremely lightweight as a whole and requires rigidity can be made of a metal alloy. Such parts can be easily assembled by joining the metal alloy part to other parts by screws or bolts and nuts. Furthermore, common parts can be made, and mass production at low cost becomes possible.

  Moreover, the composite of the metal alloy and CFRP according to the present invention exhibits a strong bonding force in a high temperature range. That is, it can be said that it is excellent in heat resistance. By applying the present invention, a high-strength aluminum alloy such as ultra-super duralumin or a titanium alloy can be integrated with CFRP to produce a structural member that is extremely light and excellent in heat resistance. When used in mobile machines such as aircraft and automobiles, a significant reduction in weight is possible.

Hereinafter, embodiments of the present invention will be described by experimental examples.
In addition, the equipment used for measurement etc. is shown below.
(A) X-ray surface observation (XPS observation)
ESCA “AXIS-Nova (Kraitos (USA) / Shimadzu Corporation (Kyoto Prefecture, Japan))” in the form of observing constituent elements on a surface having a diameter of several μm in a depth range of 1 to 2 nm was used.
(B) Electron microscope observation Using SEM type electron microscopes “S-4800 (manufactured by Hitachi, Ltd.)” and “JSM-6700F (manufactured by JEOL Ltd. (Tokyo, Japan))” at 1-2 KV Observed.
(C) Scanning Probe Microscope Observation A dynamic force scanning probe microscope “SPM-9600 (manufactured by Shimadzu Corporation)” was used.
(D) X-ray diffraction analysis (XRD analysis)
“XRD-6100 (manufactured by Shimadzu Corporation)” was used.
(E) Measurement of joint strength of composites Using a tensile tester “AG-10kNX (manufactured by Shimadzu Corporation)”, the shear breaking strength was measured at a pulling speed of 10 mm / min.
(F) Dispersion of filler (use of wet pulverizer)
A sand grind mill “Minitsu Air (manufactured by Ashizawa Finetech Co., Ltd.)” using zirconia beads having a diameter of 0.1 to 0.5 mm as sand was used.
Next, the surface treatment of the metal alloy will be described.

[Experiment 1] (Surface treatment of aluminum alloy)
A commercially available aluminum alloy sheet “A7075” having a thickness of 3 mm was obtained and cut to produce a large number of 45 mm × 15 mm rectangular A7075 pieces. A commercially available aluminum alloy degreasing agent “NE-6 (manufactured by Meltex Co., Ltd. (Tokyo, Japan))” was added to the water in the tank to prepare an aqueous solution (60 ° C.) having a concentration of 7.5%. The A7075 pieces were immersed in this for 7 minutes and washed thoroughly with water. Subsequently, a 1% hydrochloric acid aqueous solution (40 ° C.) was prepared in another tank, and the A7075 piece was immersed in the tank for 1 minute and washed with water. Next, a 1.5% strength aqueous caustic soda solution (40 ° C.) was prepared in another tank, and the A7075 pieces were immersed in this for 4 minutes and washed with water. Subsequently, a 3% nitric acid aqueous solution (40 ° C.) was prepared in another tank, and the A7075 pieces were immersed in the tank for 1 minute and washed with water. Next, an aqueous solution (60 ° C.) containing 3.5% monohydric hydrazine was prepared in another tank, and the A7075 pieces were immersed in this for 2 minutes and washed with water. Next, a 5% hydrogen peroxide aqueous solution (40 ° C.) was prepared, and the A7075 piece was immersed in the solution for 5 minutes and washed with water. Next, the A7075 pieces were dried in a hot air dryer at 67 ° C. for 15 minutes.

  When the A7075 piece was observed with an electron microscope after drying, it was found that the A7075 piece was covered with a recess having a diameter of 40 to 100 nm. A photograph when the electron microscope is observed at 10,000 times and 100,000 times is shown in FIG. The roughness data was obtained by scanning probe microscope. According to this, the peak-valley average interval (RSm) was 3-4 μm, and the maximum height (Rz) was 1-2 μm.

[Experimental example 2] (Surface treatment of aluminum alloy)
A commercially available 1.6 mm-thick aluminum alloy sheet “A5052” was obtained and cut to produce a large number of 45 mm × 15 mm rectangular A5052 pieces. A commercially available degreasing agent “NE-6” for aluminum alloy was added to the water in the tank to prepare an aqueous solution (60 ° C.) having a concentration of 7.5%. The A5052 piece was immersed in this for 7 minutes and washed thoroughly with water. Subsequently, a 1% hydrochloric acid aqueous solution (40 ° C.) was prepared in another tank, and the A5052 pieces were immersed in this for 1 minute and washed with water. Next, a 1.5% strength aqueous sodium hydroxide solution (40 ° C.) was prepared in another tank, and the A5052 pieces were immersed in this for 2 minutes and washed with water. Subsequently, a 3% nitric acid aqueous solution (40 ° C.) was prepared in another tank, and the A5052 piece was immersed in this for 1 minute and washed with water. Next, an aqueous solution (60 ° C.) containing 3.5% monohydric hydrazine was prepared in another tank, and the A5052 pieces were immersed in this for 2 minutes and washed with water. Next, the A5052 pieces were dried in a hot air dryer set at 67 ° C. for 15 minutes.

  When the A5052 piece was observed with an electron microscope after drying, it was found that the A5052 piece was covered with a recess having a diameter of 30 to 100 nm. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. The roughness data was obtained by scanning probe microscope. According to this, the mean valley interval (RSm) was 2.0 to 3.4 μm, and the maximum height (Rz) was 0.2 to 0.5 μm.

[Experiment 3] (Surface treatment of magnesium alloy)
A commercially available magnesium alloy sheet “AZ31B” having a thickness of 1 mm was obtained and cut to produce a large number of 45 mm × 15 mm rectangular AZ31B pieces. A commercially available degreasing agent for magnesium alloy “Cleaner 160 (manufactured by Meltex Co., Ltd.)” was added to the water in the tank to prepare an aqueous solution (65 ° C.) having a concentration of 7.5%. The AZ31B piece was immersed in this for 5 minutes and washed thoroughly with water. Subsequently, a 1% strength aqueous hydrated citric acid solution (40 ° C.) was prepared in another tank, and the AZ31B piece was dipped in this for 6 minutes and washed with water. Next, an aqueous solution (65 ° C.) containing 1% concentration sodium carbonate and 1% concentration sodium hydrogen carbonate was prepared in another tank, and the AZ31B piece was immersed in this for 5 minutes and washed with water. Subsequently, a 15% strength aqueous caustic soda solution (65 ° C.) was prepared in another tank, and the AZ31B piece was immersed in this for 5 minutes and washed with water. Next, a 0.25% strength aqueous hydrated citric acid solution (40 ° C.) was prepared in another tank, and the AZ31B piece was immersed in this for 1 minute and washed with water. Next, an aqueous solution (45 ° C.) containing 2% potassium permanganate, 1% acetic acid and 0.5% hydrated sodium acetate was prepared, and the AZ31B piece was immersed in this for 1 minute and washed with water for 15 seconds. Next, the AZ31B piece was placed in a hot air dryer set at 90 ° C. for 15 minutes and dried.

  After drying, when the AZ31B piece was observed with an electron microscope, 5 to 20 nm diameter rod-shaped crystals were intertwined in a complex manner to form a lump with a diameter of about 100 nm, and the lump was covered with a super fine uneven shape forming a surface. was there. 3A and 3B show photographs when the electron microscope is observed at a magnification of 100,000. When the roughness was observed by scanning with a scanning probe microscope, the average interval between peaks and valleys, that is, the average value (RSm) of the concave-convex period was 2 to 3 μm, and the maximum height roughness (Rz) was 1 to 1.5 μm. there were.

[Experimental Example 4] (Surface treatment of copper alloy)
A tough pitch copper plate material “C1100”, which is a commercially available pure copper-based copper alloy with a thickness of 1 mm, was obtained and cut to produce a large number of 45 mm × 15 mm rectangular C1100 pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6” was prepared in a tank, and the C1100 pieces were immersed in this for 5 minutes and washed with water. Next, the base was washed by immersing the C1100 piece in a 1.5% strength aqueous caustic soda solution (40 ° C.) for 1 minute and washing with water. Next, an aqueous solution (25 ° C.) containing 20% of an etching material for copper alloy “CB-5002 (MEC Co., Ltd., Hyogo, Japan)” and 18% of 30% hydrogen peroxide was prepared as an aqueous solution for etching. The C1100 piece was immersed in 10 minutes and washed with water. Next, an aqueous solution (65 ° C.) containing 10% caustic soda and 5% sodium chlorite was prepared as an oxidizing aqueous solution in another tank, and the C1100 pieces were immersed in this for 1 minute and washed with water. Next, the C1100 piece was again immersed in the aqueous solution for etching for 1 minute and washed with water, then immersed in the aqueous solution for oxidation for 1 minute, and thoroughly washed with water. Thereafter, the C1100 piece was placed in a warm air dryer at 90 ° C. for 15 minutes and dried.

  After drying, the C1100 piece was subjected to a scanning probe microscope. As a result, the mean valley interval (RSm) was 3 to 7 μm, and the maximum height roughness (Rz) was 3 to 5 μm. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. When observed with an electron microscope of 100,000 times, the hole or opening having a diameter or an average of a major axis and a minor axis having an average of 10 to 150 nm is covered with an ultrafine irregular shape having irregular intervals of 30 to 300 nm. It was broken.

[Experimental Example 5] (Surface treatment of copper alloy)
A commercially available phosphor bronze plate material “C5191” having a thickness of 0.8 mm was obtained and cut to produce a large number of rectangular C5191 pieces of 45 mm × 15 mm. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6” was prepared in a tank, and this was used as a degreasing aqueous solution. The C5191 piece was immersed in this degreasing aqueous solution for 5 minutes for degreasing and thoroughly washed with water. Subsequently, an aqueous solution (25 ° C.) containing 20% of an etching agent for copper alloy “CB-5002” and 18% of 30% hydrogen peroxide solution as an aqueous solution for etching is prepared in another tank, and the C5191 is added thereto. The piece was immersed for 15 minutes and washed with water. Next, an aqueous solution (65 ° C.) containing 10% caustic soda and 5% sodium chlorite was prepared as an oxidizing aqueous solution in another tank, and the C5191 pieces were immersed in this for 1 minute and washed with water. Next, the C5191 piece was again immersed in the etching aqueous solution for 1 minute and washed with water, and then immersed in the oxidizing aqueous solution for 1 minute and washed with water. Thereafter, the C5191 pieces were placed in a hot air dryer at 90 ° C. for 15 minutes and dried.

  After drying, the C5191 piece was subjected to a scanning probe microscope. As a result, the peak / valley mean interval (RSm) was 1 to 3 μm, and the maximum height roughness (Rz) was 0.3 to 0.4 μm. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. When observed with a 100,000-fold electron microscope, a convex or concave portion having an average diameter or major axis and minor axis of 10 to 200 nm is mixed and is present on the entire surface. What is the microstructure of tough pitch copper that is pure copper? It was a completely different shape.

[Experimental Example 6] (Surface treatment of copper alloy)
A commercially available iron-containing copper alloy sheet “KFC (manufactured by Kobe Steel, Ltd.)” having a thickness of 0.7 mm was obtained and cut to produce a large number of 45 mm × 15 mm rectangular KFC pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6” was prepared in a tank, and the KFC pieces were immersed in this for 5 minutes and washed with water. Next, the KFC pieces were immersed in a 1.5% strength aqueous caustic soda solution (40 ° C.) for 1 minute and washed with water to perform preliminary base washing. Next, an aqueous solution (25 ° C.) containing 20% of an etching material for copper alloy “CB5002 (made by MEC)” and 18% of 30% hydrogen peroxide is prepared as an aqueous solution for etching. It was immersed for a minute and washed with water. Next, an aqueous solution (65 ° C.) containing 10% caustic soda and 5% sodium chlorite was prepared as an oxidizing aqueous solution in another tank, and the KFC pieces were immersed in this for 1 minute and washed with water. Next, the KFC piece was again immersed in the etching aqueous solution for 1 minute and washed with water, and then immersed in the oxidizing aqueous solution for 1 minute and washed with water. Thereafter, the KFC pieces were placed in a hot air dryer at 90 ° C. for 15 minutes and dried.

  After drying, the KFC piece was applied to a scanning probe microscope. As a result, the mean valley interval (RSm) was 1 to 3 μm, and the maximum height roughness (Rz) was 0.3 to 0.5 μm. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. When observed with a 100,000-fold electron microscope, the entire surface was covered with an ultrafine uneven shape in which convex portions having an average diameter or major axis and minor axis of 10 to 200 nm were mixed and present on the entire surface.

[Experimental Example 7] (Surface treatment of copper alloy)
A commercially available 0.7 mm thick special copper alloy sheet “KLF5 (manufactured by Kobe Steel, Ltd.)” was obtained and cut to produce a large number of 45 mm × 15 mm rectangular KLF5 pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6” was prepared in a tank, and the KLF5 pieces were immersed in this for 5 minutes and washed with water. Subsequently, the KLF5 pieces were immersed in a 1.5% strength aqueous caustic soda solution (40 ° C.) for 1 minute and washed with water to perform preliminary base washing. Next, an aqueous solution (25 ° C.) containing 20% of an etching material for copper alloy “CB5002 (made by MEC)” and 18% of 30% hydrogen peroxide was prepared as an aqueous solution for etching. It was immersed for a minute and washed with water. Next, an aqueous solution (65 ° C.) containing 10% caustic soda and 5% sodium chlorite was prepared as an oxidizing aqueous solution in another tank, and the KLF5 pieces were immersed in this for 1 minute and washed with water. Subsequently, the KLF5 piece was again immersed in the etching aqueous solution for 1 minute and washed with water, and then immersed in the oxidizing aqueous solution for 1 minute and washed with water. Thereafter, the KLF5 pieces were placed in a hot air dryer at 90 ° C. for 15 minutes and dried.

  After drying, the KLF5 piece was applied to a scanning probe microscope. As a result, the mean valley interval (RSm) was 1 to 3 μm, and the maximum height roughness (Rz) was 0.3 to 0.5 μm. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. When observed with a 100,000-fold electron microscope, the shape is a mixture of 10 to 20 nm diameter particles and 50 to 150 nm indefinite polygonal shapes mixed together, in other words, a lava plateau slope-like ultra-fine uneven shape. The entire surface was covered.

[Experiment 8] (Surface treatment of titanium alloy)
A commercially available pure titanium type titanium alloy plate “KS40 (manufactured by Kobe Steel, Ltd.)” having a thickness of 1 mm was obtained and cut to produce a large number of 45 mm × 15 mm rectangular KS40 pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6” was prepared in a tank, and this was used as a degreasing aqueous solution. The KS40 pieces were immersed in this degreasing aqueous solution for 5 minutes to degrease and washed thoroughly with water. Next, an aqueous solution (60 ° C.) containing 2% of a universal etching material “KA-3 (manufactured by Metallurgy Engineering Laboratory (Tokyo, Japan))” containing 40% ammonium difluoride 40% in a separate tank is prepared. Then, the KS40 piece was immersed in this for 3 minutes and washed thoroughly with ion-exchanged water. Next, the KS40 piece was immersed in a 3% strength aqueous nitric acid solution for 1 minute and washed with water. Thereafter, the KS40 pieces were placed in a hot air dryer at 90 ° C. for 15 minutes and dried.

  After drying, the KS40 piece was observed with a scanning probe microscope. As a result, the peak / valley mean interval (RSm) was 1 to 3 μm, and the maximum height roughness (Rz) was 0.8 to 1.5 μm. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. From observation with an electron microscope, a curved continuous mountain-like projection having a width and height of 10 to several hundred nm and a length of several hundred to several μm stands on the surface with an interval period of 10 to several hundred nm. It was found to be an uneven shape. Furthermore, from the analysis by XPS, a large amount of oxygen and titanium were observed on the surface, and a small amount of carbon was observed. From these, it was found that the surface layer was composed mainly of titanium oxide, and because it was dark, it was estimated to be a trivalent titanium oxide.

[Experimental example 9] (Surface treatment of titanium alloy)
A commercially available α-β type titanium alloy plate “KSTi-9 (manufactured by Kobe Steel, Ltd.)” having a thickness of 1 mm was obtained and cut to produce a large number of 45 mm × 15 mm rectangular KSTi-9 pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6” was prepared in a tank, and this was used as a degreasing aqueous solution. The KSTi-9 pieces were immersed in this degreasing aqueous solution for 5 minutes for degreasing and thoroughly washed with water. Next, an aqueous solution (40 ° C.) having a caustic soda concentration of 1.5% was prepared in another tank, and the KSTi-9 piece was immersed in this for 1 minute and washed with water. Next, an aqueous solution (60 ° C.) in which 2% by weight of a commercially available general-purpose etching reagent “KA-3” was dissolved was prepared in another tank, and the KSTi-9 piece was immersed in this for 3 minutes and washed thoroughly with ion-exchanged water. . Since this KSTi-9 piece had a black smut attached, it was immersed in a 3% nitric acid aqueous solution (40 ° C.) for 3 minutes, and then immersed in ion-exchanged water subjected to ultrasonic waves for 5 minutes. Then, it was again immersed in a 3% nitric acid aqueous solution for 0.5 minutes and washed with water. Next, the KSTi-9 pieces were placed in a hot air dryer at 90 ° C. for 15 minutes and dried. The dried KSTi-9 pieces had a dark brown color with no metallic luster.

  After drying, the KSTi-9 pieces were observed with a scanning probe microscope. According to the scanning analysis, the average interval between the valleys and valleys (RSm) was 4 to 6 μm, and the maximum height roughness (Rz) was 1 to 2 μm. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. In addition to the part very similar to FIG. 8 of Experimental Example 8, many dead leaf-like parts that are difficult to express were seen.

[Experimental Example 10] (Stainless steel surface treatment)
A commercially available stainless steel plate “SUS304” having a thickness of 1 mm was obtained and cut to produce a large number of 45 mm × 15 mm rectangular SUS304 pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6” was prepared in a tank, and this was used as a degreasing aqueous solution. The SUS304 piece was immersed in this degreasing aqueous solution for 5 minutes to degrease and washed thoroughly with water. Subsequently, an aqueous solution (65 ° C.) containing 1% ammonium difluoride 1% and 98% sulfuric acid 5% was prepared in another tank, and the SUS304 piece was immersed in this for 4 minutes and washed thoroughly with ion-exchanged water. . Next, the SUS304 piece was immersed in a 3% nitric acid aqueous solution (40 ° C.) for 3 minutes and washed with water. Next, the SUS304 pieces were placed in a hot air dryer at 90 ° C. for 15 minutes and dried.

  After drying, the SUS304 piece was observed with a scanning probe microscope. According to the scanning analysis, the mean valley interval (RSm) was 1-2 μm, and the maximum height roughness (Rz) was 0.3-0.4 μm. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. From observation with an electron microscope, the surface was covered with a shape in which particle diameters having a diameter of 20 to 70 nm and indefinite polygonal shapes were stacked, in other words, a lava plateau slope-like ultra fine uneven shape. Another one was subjected to XPS analysis. From this XPS analysis, a large amount of oxygen and iron was observed on the surface, and a small amount of nickel, chromium, carbon, a very small amount of molybdenum and silicon were observed. From these, it was found that the surface layer was mainly composed of metal oxide. This analysis pattern was almost the same as SUS304 before etching.

[Experimental Example 11] (Surface treatment of general steel materials)
A commercially available cold rolled steel sheet material “SPCC” having a thickness of 1.6 mm was obtained and cut to produce a large number of 45 mm × 15 mm rectangular SPCC pieces. An aqueous solution (60 ° C.) containing 7.5% of an aluminum alloy degreasing agent “NE-6” was prepared in a tank, and the SPCC pieces were immersed in this for 5 minutes and washed with tap water (Ota City, Gunma Prefecture). . Next, a 1.5% caustic soda aqueous solution (40 ° C.) was prepared in another tank, and the SPCC pieces were immersed in this for 1 minute and washed with water. Next, an aqueous solution (50 ° C.) containing 10% of 98% sulfuric acid was prepared in another tank, and the SPCC pieces were immersed in this for 6 minutes and sufficiently washed with ion-exchanged water. Next, the SPCC piece was immersed in 1% aqueous ammonia (25 ° C.) for 1 minute and washed with water. The SPCC pieces were then immersed in an aqueous solution (45 ° C.) containing 2% potassium permanganate, 1% acetic acid, and 0.5% sodium hydrate acetate for 1 minute and thoroughly washed with water. Thereafter, the SPCC piece was placed in a warm air dryer at 90 ° C. for 15 minutes and dried.

  After drying, the SPCC pieces were observed with a scanning probe microscope. According to the scanning analysis, the mean valley interval (RSm) was 1 to 3 μm, and the maximum height roughness (Rz) was 0.3 to 1.0 μm. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. From the observation result with a 100,000 times electron microscope, it is found that the entire surface is almost covered with an ultra fine uneven shape having a height and depth of 80 to 200 nm and a width of several hundred to several thousand nm that is infinitely continuous. I understand. It can be seen that the pearlite structure is exposed and the chemical conversion treatment layer is very thin.

[Experiment 12] (Surface treatment of general steel)
A commercially available 1.6 mm thick hot rolled steel “SPHC” was obtained and cut to produce a large number of 45 mm × 15 mm rectangular SPHC pieces. An aqueous solution (60 ° C.) containing 7.5% of an aluminum alloy degreasing agent “NE-6” was prepared in a tank, and the SPHC pieces were immersed in this for 5 minutes and washed with tap water (Ota City, Gunma Prefecture). . Next, a 1.5% caustic soda aqueous solution (40 ° C.) was prepared in another tank, and the SPHC pieces were immersed in this for 1 minute and washed with water. Next, an aqueous solution (65 ° C.) containing 10% 98% sulfuric acid and 1% ammonium difluoride was prepared in another tank, and the SPHC pieces were immersed in this for 2 minutes and washed thoroughly with ion-exchanged water. . Next, the SPHC pieces were immersed in 1% aqueous ammonia (25 ° C.) for 1 minute and washed with water. Next, the SPHC piece was an aqueous solution (55 ° C.) containing 80% orthophosphoric acid 1.5%, zinc white 0.21%, sodium silicofluoride 0.16% and basic nickel carbonate 0.23%. For 1 minute and thoroughly washed with water. Thereafter, the SPHC pieces were placed in a warm air dryer at 90 ° C. for 15 minutes and dried.

  After drying, the SPHC pieces were observed with a scanning probe microscope. According to the scanning analysis, the mean valley interval (RSm) was 1 to 3 μm, and the maximum height roughness (Rz) was 0.3 to 1.0 μm. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. According to the result of observation with an electron microscope of 100,000 times, it was found that the entire surface was covered with an ultra-fine concavo-convex shape having an infinite number of steps having a height and depth of 80 to 500 nm and a width of several hundred to several tens of thousands of nm. Okay, this was also a pearlite structure.

[Experimental Example 13] (Preparation of adhesive (1))
An epoxy resin “JER828 (manufactured by Japan Epoxy Resin Co., Ltd., Tokyo, Japan)” having a molecular weight of about 370, the main component of which is a monomer type bisphenol-type epoxy resin, and a solid bisphenol-type epoxy resin having a molecular weight of about 1300 "JER1003 (Japan Epoxy Resin Co., Ltd.)", multifunctional phenol novolac epoxy resin "JER154 (Japan Epoxy Resin Co., Ltd.)", aniline type trifunctional epoxy resin "JER630 (Japan Epoxy Resin Co., Ltd.)" PES powder “PES4100MP (manufactured by Sumitomo Chemical Co., Ltd., Japan)” having an average particle size of about 10 μm, multi-walled carbon nanotube “MCNT” (Nanocarbon Technologies Co., Ltd. (Tokyo, Japan)) Manufactured)), average particle size is 1 Hydrophobic-treated fumed silica "Aerosil R805 (manufactured by Nippon Aerosil Co., Ltd., Tokyo, Japan)", fine powder talc "Hymicron HE5 (Takehara Chemical Co., Ltd.) with an average particle size of 8-12 μm (Manufactured by Hyogo, Japan)), calcined kaolin clay “Satinton 5 (manufactured by Takehara Chemical Co., Ltd.)” having an average particle size of 10 to 15 μm, fine powder dicyandiamide “DICY7” (Japan) Epoxy Resin Co., Ltd.) ”and 3- (3,4-dichlorophenyl) -1,1-dimethylurea“ DCMU99 (Hodogaya Chemical Co., Ltd., Tokyo, Japan), which is the same curing aid. ) ”.

  Take 60 parts of “JER828”, 20 parts of “JER1003”, 10 parts of “JER154” and 10 parts of “JER630” in a beaker and leave them in a hot air dryer at 130 ° C. to heat them. Was melted and stirred at the same time to homogenize the whole. Then, it stood to cool and stored as an epoxy resin liquid. A sand grind mill “Minitsu Air” filled with zirconia beads having a diameter of 0.3 mm and filled with 80% of the grinding chamber capacity was prepared, and an open tank with a circulation pump and a stirrer was connected to the inlet side. On the other hand, the exit of the sand grind mill was opened to an open tank. The above epoxy resin liquid was reheated to 60 ° C. to lower the viscosity, 350 g was put into an open tank, and the mill was started after the grinding chamber was completely filled with a circulation pump. Since the mill has a water cooling line, water flow was adjusted so that the inside of the grinding chamber was 50-60 ° C. The peripheral speed of the mill rotor was set to 11 to 12 m / sec. Thereafter, 10 g of “Hi-micron HE5” was gradually added to the open tank to circulate and grind, and then “Aerosil R805” was added in the same manner as 1.6 g. The circulating pulverization proceeded for about 5 minutes, and then 16 g of “PES4100MP” was gradually added, followed by wet pulverization (substantially dispersion operation) for 40 minutes. The outlet of the mill faces the polyethylene bottle from the open tank. For all 100 parts of epoxy resin, 4.5 parts of “PES4100MP”, 2.9 parts of “Himicron HE5” and 0.5 parts of “Aerosil R805” A mixture containing parts was obtained in a polyethylene bottle. Next, to 108 parts of the mixture, 5 parts of a curing agent “DICY7” was added and kneaded well with a glass rod, and then 3 parts of a curing aid “DCMU99” was added and kneaded well again. Next, the beaker was covered with aluminum foil and allowed to stand at room temperature for 50 hours, so that a kind of aging was performed. The adhesive thus obtained was designated as adhesive (1).

[Experimental Example 14] (Preparation of adhesive (2))
An adhesive was prepared in the same manner as in Experimental Example 13 with the following differences. After starting the operation of the mill, 16 g of “PES4100MP”, 10 g of “Himicron HE5”, 2 g of “Aerosil R805”, and 0.3 g of CNT “MCNT” were added. As a result, 4.5 parts of “PES4100MP”, 2.9 parts of “Hymicron HE5”, 0.5 part of “Aerosil R805”, and 0.07 of “MCNT” with respect to 100 parts of all epoxy resins from the mill. A mixture containing parts was obtained. The same treatment as in Experimental Example 13 was performed on 108 parts of this mixture, and then stored in a refrigerator at 5 ° C. The adhesive thus obtained was designated as adhesive (2).

[Experimental Example 15] (Preparation of adhesive (3))
An adhesive was prepared in the same manner as in Experimental Example 13, except that “Aerosil R805” was not added. That is, the mixture before adding the curing agent “DICY7” and the like contains 4.5 parts of “PES4100MP” and 2.9 parts of “High Micron HE5” with respect to 100 parts of the total epoxy resin. The adhesive thus obtained was designated as adhesive (3).

[Experimental Example 16] (Preparation of adhesive (4))
An adhesive was prepared in the same manner as in Experimental Example 13 except that “PES4100MP” was not added. That is, the mixture before adding the curing agent “DICY7” and the like contains 2.9 parts of “Hymicron HE5” and 0.5 part of “Aerosil R805” with respect to 100 parts of the total epoxy resin. The adhesive thus obtained was designated as adhesive (4).

[Experimental Example 17] (Preparation of adhesive (5))
An adhesive was prepared in the same manner as in Experimental Example 13, except that “PES4100MP” and “Aerosil R805” were not added. That is, the mixture before adding the curing agent “DICY7” and the like contains 2.9 parts of “High Micron HE5” with respect to 100 parts of the total epoxy resin. The adhesive thus obtained was designated as adhesive (5).

[Experiment 18] (Creation of CFRP piece)
In the present experimental example, a CFRP piece is created as an example of the above-described CFRP shaped object. This CFRP piece is constituted by laminating a plurality of CFRP prepreg pieces. A CFRP prepreg “Pyrofil TR3110 (manufactured by Mitsubishi Rayon Co., Ltd.)” was obtained, and a large number of 45 mm × 15 mm pieces were cut out. A rectangular CFRP piece is created using the firing jig 1 shown in FIG. When the mold body 2 and the mold bottom plate 5 are combined, the mold recess 3 is formed by the side wall of the mold body 2 and the upper surface of the mold bottom plate 5. A release film 17 having a thickness of 0.05 mm was laid so as to cover the mold recess 3. Spacers 11 and 16 made of polytetrafluoroethylene resin (hereinafter referred to as “PTFE”) were placed on the release film 17. A small piece of 45 mm × 15 mm CFRP prepreg that had been cut was laminated on the upper surfaces of the spacers 11 and 16 by a thickness of 3 mm (the laminate is shown as 12 in FIG. 13 and becomes a CFRP piece 12 after molding). ). In order to fill the gap between the laminate and the side wall of the mold body 2, a PTFE spacer 13 was installed, and a release film 14 was laid so as to cover them.

  A PTFE block 15 was placed on the release film 14 and placed in a hot air dryer. Further, a 5 kg weight 18 made of iron was placed on the block 15, and the dryer was energized. Raise to 90 ° C. for 30 minutes, then raise to 120 ° C. for 30 minutes, then raise to 135 ° C. for 30 minutes, then raise to 165 ° C. for 30 minutes, then 180 ° C. Then, after standing for 30 minutes, the power supply was stopped and the system was allowed to cool with the door closed. The next day, when the weight 18, the block 15, and the pedestal 8 are removed and the mold body 2 is pressed against the floor, the bottom plate protrusion 6 that protrudes below the mold bottom surface 7 from the mold through hole 4 of the mold body 2 is formed. The mold bottom plate 5 that is in contact is pushed upward. Thereby, the CFRP piece 12 which is a molded product covered with the release films 14 and 17 can be taken out from the firing jig 1. This operation was repeated to obtain many CFRP pieces 12. The CFRP piece 12 thus obtained is referred to as a once-baked product.

  Three days later, the CFRP piece 12 obtained as described above was put again in a hot air dryer, placed at 90 ° C. for 30 minutes, then heated to 135 ° C. for 30 minutes, then heated to 165 ° C. and heated to 30 ° C. Separately, further raised to 190 ° C. and allowed to cool for 30 minutes. The CFRP piece 12 thus obtained is referred to as a twice-baked product. The twice-baked product was baked again under the same conditions after 3 days. The CFRP piece 12 thus obtained is referred to as a three-time baked product.

  The end of the three-time-baked CFPR piece 12 was rubbed firmly with number 120 abrasive paper several times to roughen it. Then, it was immersed for 5 minutes in the degreasing tank made into the same 60 degreeC as what was used in Experimental example 1. FIG. Ultrasonic waves were applied to this degreasing tank. Thereafter, it was thoroughly washed with pure water and dried at 90 ° C. for 15 minutes. The CFRP pieces used in the following Experimental Examples 19-1 to 19-6 and Experimental Examples 22 to 32 are three times baked products of the CFRP pieces 12 subjected to these treatments.

[Experimental Example 19-1] (A7075 / CFRP complex (1))
Six A7075 pieces subjected to the surface treatment of Experimental Example 1 were prepared. In addition, six CFRP pieces prepared in Experimental Example 18 were prepared. The adhesive (1) prepared in Experimental Example 13 was applied to the end portions of each of these A7075 pieces and CFRP pieces. These were placed in a large desiccator that had been warmed for a long time in a hot air dryer set at 60 ° C. in advance. The lid of the desiccator was put on, and the pressure was reduced with a vacuum pump, and the pressure was kept below 15 mmHg for several minutes. Thereafter, after returning to normal pressure, the pressure was immediately reduced. Such a decompression / normal pressure return operation cycle was performed three times, the lid was opened, and A7075 pieces and CFRP pieces were taken out.

  The adhesive-applied portions of the A7075 piece and the CFRP piece taken out from the desiccator were bonded to form a test piece (FIG. 14), and both pieces were fixed with a clip and transferred into a hot air dryer. The hot air dryer was set at 90 ° C., held at 15 ° C. for 15 minutes, then raised to 135 ° C., held for 1 hour, further raised to 165 ° C. and held for 30 minutes, and then allowed to cool. The next day, the clips were removed to obtain 6 sets of A7075 / CFRP composites (1).

[Experimental Example 19-2] (A7075 / CFRP composite (2))
Six sets of A7075 / CFRP composites (2) were obtained in the same manner as in Experimental Example 19-1. However, in this experimental example, the adhesive (2) was used instead of the adhesive (1).

[Experimental Example 19-3] (A7075 / CFRP composite (3))
Six sets of A7075 / CFRP composites (3) were obtained in the same manner as in Experimental Example 19-1. However, in this experimental example, the adhesive (3) was used instead of the adhesive (1).

[Experimental Example 19-4] (A7075 / CFRP composite (4))
Six sets of A7075 / CFRP composites (4) were obtained in the same manner as in Experimental Example 19-1. However, in this experimental example, the adhesive (4) was used instead of the adhesive (1).

[Experimental Example 19-5] (A7075 / CFRP composite (5))
Six sets of A7075 / CFRP composites (5) were obtained in the same manner as in Experimental Example 19-1. However, in this experimental example, the adhesive (5) was used instead of the adhesive (1).

[Experimental Example 19-6] (A7075 / CFRP composite (6))
Six sets of A7075 / CFRP composites (6) were obtained in the same manner as in Experimental Example 19-1. However, in this experimental example, not the adhesive (1) but an epoxy adhesive “EP106” containing an inorganic filler using a commercially available dicyandiamide as a curing agent was used.

  Six types of A7075 / CFRP composites were obtained by the methods shown in Experimental Examples 19-1 to 19-6. For each of the various composites (A7075 / CFRP composites (1) to (6)), three sets were each subjected to a tensile fracture test at room temperature, and the remaining three groups were subjected to a tensile fracture test at 100 ° C. The shear breaking force was divided by the adhesion area, and three sets of shear breaking forces were calculated, and the average value was obtained. The results are shown in Table 1. According to Table 1, at room temperature, even when any adhesive was used, a high shear breaking force of about 70 MPa was shown. However, the shear breaking force at 100 ° C. is a composite using the adhesive (1), (2), or (4) filled with Aerosil R805 (Experimental Examples 19-1, 19-2, 19-4). Obviously it was expensive.

(About CFRP pieces baked once and baked twice)
Here, in Experimental example 19-1, the adhesion target of the A7075 piece was a CFRP piece baked three times, and the shear breaking strength at room temperature was 68.5 MPa as shown in Table 1. The present inventors, instead of the three-time baked product, bonded the one-time baked CFRP piece to the A7075 piece in the same manner as in Experimental Example 19-1, and obtained A7075 / CFRP (one-time baked product). ) The shear breaking strength of the composite was measured at room temperature. As a result, the average value of the three sets was 58.0 MPa. In addition, instead of the three-time baked product, the inventors bonded the two-time CFRP piece to the A7075 piece in the same manner as in Experimental Example 19-1, and obtained A7075 / CFRP (double-baked product). Article) The shear breaking strength of the composite was measured at room temperature. As a result, the average value of the three sets was 64.4 MPa. As described above, this is considered to be because the adhesive force between the carbon fiber and the matrix resin is improved by re-baking the CFRP piece. In particular, in the three-time baked product, the product with the highest shear fracture strength was 71.8 MPa. The average value of the shear breaking force was also around 70 MPa, which was equivalent to the shear breaking force of the adhesive joined body between the A7075 aluminum alloy pieces.

[Experimental Example 20-1] (Roughening Method (1))
A CFRP piece was baked three times in the same manner as in Experimental Example 18. However, unlike Experimental Example 18, the treatment after the roughening was performed as follows. The end of the CFRP piece was roughened by rubbing firmly with No. 120 polishing paper 3 to 5 times. Then, it was immersed for 5 minutes in the degreasing tank made into the same 60 degreeC as what was used in Experimental example 1. FIG. Ultrasonic waves were applied to this degreasing tank. Thereafter, it was washed thoroughly with room temperature tap water (Ota City, Gunma Prefecture) and dried at 90 ° C. for 15 minutes.

[Experimental Example 20-2] (Roughening Method (2))
A CFRP piece was baked three times in the same manner as in Experimental Example 18. However, unlike Experimental Example 18, the treatment after the roughening was performed as follows. The end of the CFRP piece was roughened by rubbing firmly with No. 80 polishing paper 3 to 5 times. Then, it was immersed for 5 minutes in the degreasing tank made into the same 60 degreeC as what was used in Experimental example 1. FIG. Ultrasonic waves were applied to this degreasing tank. Then, after being immersed in methyl ethyl ketone (hereinafter referred to as “MEK”) for 1 minute, it was thoroughly washed with pure water and dried at 90 ° C. for 15 minutes.

[Experimental Example 20-3] (Roughening Method (3))
A CFRP piece was baked three times in the same manner as in Experimental Example 18. However, unlike Experimental Example 18, the treatment after the roughening was performed as follows. The end of the CFRP piece was roughened by rubbing firmly with No. 240 polishing paper 3 to 5 times. Then, it was immersed for 5 minutes in the degreasing tank made into the same 60 degreeC as what was used in Experimental example 1. FIG. Ultrasonic waves were applied to this degreasing tank. Thereafter, it was washed thoroughly with room temperature tap water (Ota City, Gunma Prefecture) and dried at 90 ° C. for 15 minutes.

[Experimental Example 20-4] (Roughening Method (4))
A CFRP piece was baked three times in the same manner as in Experimental Example 18. However, unlike Experimental Example 18, the treatment after the roughening was performed as follows. The end of the CFRP piece was roughened by rubbing firmly with No. 800 polishing paper 3-5 times. Then, it was immersed for 5 minutes in the degreasing tank made into the same 60 degreeC as what was used in Experimental example 1. FIG. Ultrasonic waves were applied to this degreasing tank. Thereafter, it was washed thoroughly with room temperature tap water (Ota City, Gunma Prefecture) and dried at 90 ° C. for 15 minutes.

[Experimental Example 20-5] (Roughening Method (5))
A CFRP piece was baked three times in the same manner as in Experimental Example 18. However, unlike Experimental Example 18, the treatment after the roughening was performed as follows. The end of the CFRP piece was roughened by rubbing firmly with No. 1000 polishing paper 3 to 5 times. Then, it was immersed for 5 minutes in the degreasing tank made into the same 60 degreeC as what was used in Experimental example 1. FIG. Ultrasonic waves were applied to this degreasing tank. Thereafter, it was washed thoroughly with room temperature tap water (Ota City, Gunma Prefecture) and dried at 90 ° C. for 15 minutes.

  The CFRP pieces subjected to the roughening of Experimental Examples 20-1 to 20-5 were adhesively bonded to A7075 pieces using the adhesive (1) in the same manner as in Experimental Example 19-1, respectively, and A7075 / A CFRP complex was obtained. Each composite was subjected to a tensile fracture test at room temperature and at each temperature of 100 ° C., and the shear fracture strength was measured. The results are shown in Table 2. In the case of polishing with No. 80 polishing paper, even when immersed for 1 minute in the organic solvent MEK, which is an intermediate solution, the shear breaking force did not improve at both room temperature and 100 ° C., but rather decreased. Therefore, it was judged that it was not necessary to immerse in an organic solvent as an intermediate solution. The tap water used was weakly acidic water having a pH of 5.8 to 6.5, but no difference was found from cleaning with pure water (ion exchange water). Further, as the abrasive paper becomes finer (No. 240, No. 800, No. 1000), there is a tendency for the shear breaking force to decrease. Especially in the case of No. 1000, compared with the cases of No. 80 to No. 240. As a result, the shear breaking strength was significantly reduced.

  Although the influence of the force applied when roughening the CFRP is also affected, it can be said that a method of polishing with coarse abrasive paper of about 80 to 240 as defined in JIS R6252 is basically preferable. Of course, the abrasive member is not limited to abrasive paper, and other abrasive members such as abrasive cloth having a roughness corresponding to this range of roughness may be used.

[Experimental example 21-1] (Washing method (1))
A CFRP piece was baked three times in the same manner as in Experimental Example 18. However, unlike Experimental Example 18, the treatment after the roughening was performed as follows. Each CFRP piece was roughened by rubbing firmly with No. 120 abrasive paper three times. A 100 cc syringe was filled with a 200 times aqueous solution of a general liquid laundry detergent “Attack” (manufactured by Kao Corporation), and applied to the roughened portion of the CFRP piece all at once. After a few minutes, tap water was washed on the CFRP piece with a hose for 15 seconds, air-dried for 24 hours, and then dried in a hot-air dryer at 80 ° C. for 5 minutes.

[Experimental example 21-2] (Washing method (2))
A CFRP piece was baked three times in the same manner as in Experimental Example 18. However, unlike Experimental Example 18, the treatment after the roughening was performed as follows. Each CFRP piece was roughened by rubbing firmly with No. 120 abrasive paper three times. From a pressure-resistant hose with a squeezed nozzle, tap water having a pressure of 2 atm (gauge pressure) was flowed for 30 seconds with a strong bar flow to wash the roughened area of the CFRP piece. Thereafter, it was air-dried for 24 hours, and then further dried in a hot-air dryer at 80 ° C. for 5 minutes.

  The CFRP pieces subjected to the water washing in Experimental Examples 21-1 and 21-2 were bonded and bonded to A7075 pieces using the adhesive (1) in the same manner as in Experimental Example 19-1, respectively, and A7075 / CFRP composite Got the body. Each composite was subjected to a tensile fracture test at room temperature and at each temperature of 100 ° C., and the shear fracture strength was measured. The results are shown in Table 3. From this result, it is understood that it is not necessary to use a surfactant for cleaning the roughened range, and a result equivalent to Experimental Example 19-1 can be obtained by cleaning for a long time with high-pressure tap water. It was.

[Experimental Example 22] (A5052 / CFRP composite)
The A5052 piece subjected to the surface treatment of Experimental Example 2 and the CFRP piece obtained in Experimental Example 18 were adhesively bonded using the adhesive (1) in the same manner as in Experimental Example 19-1, and an A5052 / CFRP composite was obtained. Got.

[Experimental Example 23] (AZ31B / CFRP composite)
The AZ31B piece subjected to the surface treatment of Experimental Example 3 and the CFRP piece obtained in Experimental Example 18 were bonded and bonded using the adhesive (1) in the same manner as in Experimental Example 19-1, and an AZ31B / CFRP composite was obtained. Got.

[Experimental Example 24] (C1100 / CFRP composite)
The C1100 piece subjected to the surface treatment of Experimental Example 4 and the CFRP piece obtained in Experimental Example 18 were adhesively bonded using the adhesive (1) in the same manner as in Experimental Example 19-1, and a C1100 / CFRP composite was obtained. Got.

[Experiment 25] (C5191 / CFRP complex)
The C5191 piece subjected to the surface treatment of Experimental Example 5 and the CFRP piece obtained in Experimental Example 18 were bonded and bonded using the adhesive (1) in the same manner as in Experimental Example 19-1, and the C5191 / CFRP composite was obtained. Got.

[Experiment 26] (KFC / CFRP composite)
The KFC piece subjected to the surface treatment of Experimental Example 6 and the CFRP piece obtained in Experimental Example 18 were adhesively bonded using the adhesive (1) in the same manner as in Experimental Example 19-1, and a KFC / CFRP composite was obtained. Got.

[Experimental example 27] (KLF5 / CFRP composite)
The KLF5 piece subjected to the surface treatment of Experimental Example 7 and the CFRP piece obtained in Experimental Example 18 were adhesively bonded using the adhesive (1) in the same manner as in Experimental Example 19-1, and a KLF5 / CFRP composite was obtained. Got.

[Experiment 28] (KS40 / CFRP composite)
The KS40 piece subjected to the surface treatment of Experimental Example 8 and the CFRP piece obtained in Experimental Example 18 were adhesively bonded using the adhesive (1) in the same manner as in Experimental Example 19-1, and a KS40 / CFRP composite was obtained. Got.

[Experimental example 29] (KSTi-9 / CFRP composite)
The KSTi-9 piece subjected to the surface treatment of Experimental Example 9 and the CFRP piece obtained in Experimental Example 18 were adhesively bonded using the adhesive (1) in the same manner as in Experimental Example 19-1, and KSTi-9. / CFRP composite was obtained.

[Experiment 30] (SUS304 / CFRP composite)
The SUS304 piece subjected to the surface treatment of Experimental Example 10 and the CFRP piece obtained in Experimental Example 18 were bonded and bonded using the adhesive (1) in the same manner as in Experimental Example 19-1, and the SUS304 / CFRP composite was obtained. Got.

[Experimental example 31] (SPCC / CFRP composite)
The SPCC piece subjected to the surface treatment of Experimental Example 11 and the CFRP piece obtained in Experimental Example 18 were adhesively bonded using the adhesive (1) in the same manner as in Experimental Example 19-1, and an SPCC / CFRP composite was obtained. Got.

[Experiment 32] (SPHC / CFRP composite)
The SPHC piece subjected to the surface treatment of Experimental Example 12 and the CFRP piece obtained in Experimental Example 18 were adhesively bonded using the adhesive (1) in the same manner as in Experimental Example 19-1, and the SPHC / CFRP composite was obtained. Got.

  About the composite_body | complex obtained by the said Experimental Examples 22-32, the tensile fracture test was done 3 each at normal temperature and each temperature of 100 degreeC, the shear fracture force was measured, and the average value was calculated. The results are shown in Table 4. All the metal alloys showed a high shear fracture strength at a high temperature, which was unprecedented.

[Experimental Example 33] (A7075 / CFRP composite (clay filler))
An adhesive was prepared in the same manner as in Experimental Example 13. However, fine powder talc “Hi-micron HE5” was not used as the inorganic filler, and “Satinton 5” of calcined kaolin clay was used instead. This adhesive was designated as adhesive (6). The A7075 piece subjected to the surface treatment of Experimental Example 1 and the CFRP piece obtained in Experimental Example 18 were replaced with the same method as in Experimental Example 19-1 using the adhesive (6) (however, instead of the adhesive (1)). Adhesive bonding was performed using an adhesive (6)) to obtain an A7075 / CFRP composite. A tensile fracture test was conducted on the seventh day after joining. The shear breaking force at normal temperature was 66.2 MPa on average, and the shear breaking force at 100 ° C. was 52.3 MPa. This result was close to Experimental Example 19-1.

FIG. 1 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by chemically etching an A7075 aluminum alloy with a caustic soda aqueous solution and finely etching with a hydrated hydrazine aqueous solution. FIG. 2 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by chemically etching an A5052 aluminum alloy with an aqueous caustic soda solution and finely etching with an aqueous hydrazine solution. FIG. 3 is a 100,000 times electron micrograph (100% magnification of (a) and (b)) of a surface obtained by chemically etching an AZ31B magnesium alloy with a citric acid aqueous solution and chemical conversion treatment with a potassium permanganate aqueous solution. FIG. 4 is an electron micrograph of a surface obtained by chemically etching a C1100 copper alloy with an aqueous solution of sulfuric acid and hydrogen peroxide and surface-treating with an aqueous solution of sodium chlorite ((a): 10,000 times, (b): 100,000 times) ). FIG. 5 is an electron micrograph ((a): 10,000 times, (b): 100,000) of a surface obtained by chemically etching a C5191 phosphor bronze alloy with sulfuric acid / hydrogen peroxide aqueous solution and surface hardening treatment with sodium chlorite aqueous solution. Times). Fig. 6 shows electron micrographs of the surface of KFC copper alloy chemically etched with sulfuric acid / hydrogen peroxide solution and surface hardened with sodium chlorite solution ((a): 10,000 times, (b): 100,000 times) ). FIG. 7 is an electron micrograph of a surface obtained by chemically etching a KLF5 copper alloy with sulfuric acid / hydrogen peroxide aqueous solution and surface-hardening with sodium chlorite aqueous solution ((a): 10,000 times, (b): 100,000 times) ). FIG. 8 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by chemically etching a KS40 pure titanium-based titanium alloy with an aqueous hydrogen difluoride ammonium solution. FIG. 9 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by chemically etching a KSTi-9α-β titanium alloy with an aqueous solution of 1 hydrogen difluoride ammonium fluoride. FIG. 10 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by chemically etching SUS304 stainless steel with a sulfuric acid aqueous solution. FIG. 11 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by etching a SPCC cold rolled steel material with a sulfuric acid aqueous solution. FIG. 12 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of the surface of SPHC hot-rolled steel material etched with a sulfuric acid aqueous solution. FIG. 13 is a cross-sectional view of a firing jig for making CFRP pieces by overlapping CFRP prepregs and curing them in a hot air dryer. FIG. 14 shows a composite in which the metal alloy piece subjected to the surface treatment of the present invention and CFRP are bonded with a one-component epoxy adhesive. FIG. 15 is a cross-sectional view showing the surface structure of the metal alloy subjected to the surface treatment of the present invention and the one-component epoxy adhesive. FIG. 16 is a cross-sectional view when the joint surface between the metal alloy subjected to the surface treatment of the present invention and the one-component epoxy adhesive is on the verge of breaking.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Baking jig 2 ... Mold main body 3 ... Mold recessed part 4 ... Mold through-hole 5 ... Mold bottom plate 6 ... Bottom plate projection 7 ... Mold bottom surface 8 ... Base 11 ... Spacer 12 ... CFRP piece 13 ... Spacer 14 ... release film 15 ... block 16 ... spacer 17 ... release film 18 ... weight 30 ... test piece 31 ... metal alloy piece 32 ... CFRP piece 33 ... adhesion range 40 ... metal alloy phase 41 ... ceramic layer 42 ... adhesion Hardened agent phase 50 ... Metal alloy phase 51 ... Ceramic layer 52 ... Hardened adhesive phase 53 ... Space generated by peeling

Claims (31)

A composite of metal alloy and fiber reinforced plastic,
The surface of the metal alloy is etched to have a roughness on the order of microns with an average interval between peaks and valleys (RSm) of 0.8 to 10 μm and a maximum height roughness (Rz) of 0.2 to 5 μm. In the surface having the roughness, ultra-fine irregularities with a period of 5 to 500 nm are formed, and the surface layer is a thin layer of metal oxide or metal phosphate,
The fiber reinforced plastic is a cured product of carbon fiber reinforced plastic (CFRP) having an epoxy resin as a matrix resin , and the surface of the cured product is roughened,
The surface of the metal alloy and the surface of the fiber reinforced plastic are (1) an inorganic filler having a particle size distribution center of 5 to 20 μm, (2) an ultrafine inorganic filler having a particle size of 100 nm or less, and ( 3) The composite described above, which is bonded through a one-component epoxy adhesive filled with thermoplastic resin powder. A composite of the metal alloy and fiber reinforced plastic according to claim 1,
The composite is characterized in that the metal alloy is any one selected from an aluminum alloy, a magnesium alloy, a copper alloy, a titanium alloy, stainless steel, and a steel material. A composite of a metal alloy and a fiber reinforced plastic according to claim 1 or 2,
  The composite of the carbon fiber reinforced plastic has a rough surface polished by a polishing member having a roughness corresponding to polishing paper Nos. 80 to 240 defined in JIS R6252. body. A composite of a metal alloy and a fiber reinforced plastic according to claim 1 selected from claims 1 to 3,
The composite according to claim 1, wherein the ultrafine inorganic filler is fumed silica and is contained in the one-component epoxy adhesive in an amount of 0.3 to 3.0% by mass. A composite of metal alloy and fiber reinforced plastic according to claim 1 selected from claims 1 to 4,
The composite according to claim 1, wherein the thermoplastic resin is a polyethersulfone resin. A composite of the metal alloy according to claim 5 and a fiber reinforced plastic,
The polyether sulfone resin powder has a particle size distribution center of 5 to 25 μm and is contained in the one-component epoxy adhesive in an amount of 2 to 5 mass%. The surface of the metal alloy has a roughness in the order of microns with an average interval between peaks and valleys (RSm) of 0.8 to 10 μm and a maximum height roughness (Rz) of 0.2 to 5 μm. In the surface having ultra-fine irregularities with a period of 5 to 500 nm is formed, and the surface treatment step for the surface layer to be a thin layer of metal oxide or metal phosphate,
A curing process for curing a fiber reinforced plastic using an epoxy resin as a matrix resin;
A roughening step of roughening the surface of the fiber-reinforced plastic that has undergone the curing step;
(1) An inorganic filler having a particle size distribution center of 5 to 20 μm, (2) an ultrafine inorganic filler having a particle size of 100 nm or less, and (3) an epoxy resin filled with a thermoplastic resin powder 1 An adhesive preparation process for creating a liquid epoxy adhesive;
An application step of applying the one-component epoxy adhesive to the surface of the metal alloy that has undergone the surface treatment step and the surface of the fiber-reinforced plastic that has undergone the roughening step;
Bonding of the metal alloy and the fiber reinforced plastic that have undergone the coating process by heating both in a state in which the areas where the one-component epoxy adhesive is applied are pressed and fixed, and the one-component epoxy adhesive is cured. Process,
A method for producing a composite of a metal alloy and a fiber reinforced plastic, comprising: A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 7,
The metal alloy is an aluminum alloy,
The surface treatment step includes a chemical etching step of immersing the aluminum alloy in a strongly basic aqueous solution, a neutralization step of immersing the aluminum alloy in an acidic aqueous solution after the chemical etching step, and after the neutralizing step, the aluminum And a fine etching step of immersing the alloy in an aqueous solution containing at least one selected from hydrated hydrazine, ammonia, and a water-soluble amine compound. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 8,
The manufacturing method according to claim 1, wherein the surface treatment step further includes an oxidation step of immersing the aluminum alloy in a hydrogen peroxide solution after the fine etching step. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 7,
The metal alloy is a magnesium alloy,
The surface treatment step includes a chemical etching step of immersing the magnesium alloy in an acidic aqueous solution, and a chemical conversion treatment step of immersing the magnesium alloy in a permanganate aqueous solution after the chemical etching step. The manufacturing method. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 7,
The metal alloy is a copper alloy,
The surface treatment step includes a chemical etching step of immersing the copper alloy in an acidic aqueous solution containing an oxidizing agent, and a surface hardening step of immersing the copper alloy in a strongly basic aqueous solution containing an oxidizing agent after the chemical etching step, The manufacturing method characterized by including. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 11,
The copper alloy is a pure copper-based copper alloy,
The said manufacturing method characterized by performing the said chemical etching process and the said surface hardening process again with respect to the copper alloy which passed through the said chemical etching process and the said surface hardening process in the said surface treatment process. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 7,
The metal alloy is a pure titanium-based titanium alloy,
The method according to claim 1, wherein the surface treatment step includes a chemical etching step of immersing the titanium alloy in an aqueous solution containing ammonium hydrogen fluoride. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 7,
The metal alloy is stainless steel,
The method according to claim 1, wherein the surface treatment step includes a chemical etching step of immersing the stainless steel in a sulfuric acid aqueous solution. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 7,
The metal alloy is a steel material,
The manufacturing method according to claim 1, wherein the surface treatment step includes a chemical etching step of immersing the steel material in a sulfuric acid aqueous solution. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 15,
In the surface treatment step, the steel material that has undergone the chemical etching step is selected from one kind selected from hexavalent chromium compounds, permanganates, zinc phosphate compounds, ammonia, hydrazine, and water-soluble amine compounds. The said manufacturing method characterized by further including the process of immersing in the aqueous solution to contain. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 7,
The metal alloy is an α-β type titanium alloy,
The method according to claim 1, wherein the surface treatment step includes a chemical etching step of immersing the titanium alloy in an aqueous solution containing ammonium hydrogen fluoride. A method for producing a composite of a metal alloy and a fiber-reinforced plastic according to claim 1 selected from claim 7 to 17,
Prior to the bonding step, the metal alloy and the fiber reinforced plastic that have been subjected to the coating step are put in a sealed container, the inside of the container is depressurized, and then pressurized, and the one-component epoxy adhesive is the metal alloy and The said manufacturing method characterized by making it soak into the surface of the said fiber reinforced plastic. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to one selected from claim 7 to 18, comprising:
The ultrafine inorganic filler is fumed silica, and is contained in the one-component epoxy adhesive in an amount of 0.3 to 3.0% by mass. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to one of claims 7 to 19,
The said manufacturing method characterized by the said thermoplastic resin being polyether sulfone resin. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 20,
The polyethersulfone resin powder has a particle size distribution center of 5 to 25 μm and is contained in the one-component epoxy adhesive in an amount of 2 to 5 mass%. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 1 selected from claims 7 to 21,
In the adhesive preparation step, (1) the inorganic filler, (2) the ultrafine inorganic filler, and (3) the thermoplastic resin powder is filled in the epoxy resin, The said manufacturing method characterized by producing the said 1 liquid epoxy adhesive by disperse | distributing with a mill type wet grinder. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 1 selected from claims 7 to 22,
The manufacturing method, wherein the fiber reinforced plastic is carbon fiber reinforced plastic (CFRP). A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 23,
In the curing step, the carbon fiber reinforced plastic is cured a plurality of times. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 24,
In the curing step, the carbon fiber reinforced plastic is cured three times. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to one selected from claim 23 to 25,
In the roughening step, the surface of the carbon fiber reinforced plastic is polished using a polishing member having a roughness corresponding to polishing paper Nos. 80 to 240 defined in JIS R6252. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 1 selected from claims 23 to 26, comprising:
The said manufacturing method characterized by including the washing | cleaning process which wash | cleans the carbon fiber reinforced plastic which passed through the said roughening process before the said application | coating process, without using an organic solvent, and then dries. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 27,
In the washing step, the carbon fiber reinforced plastic is ultrasonically washed while being immersed in an aqueous solution of a surfactant, then washed with water, and then dried. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 27,
In the cleaning step, the manufacturing method is characterized by spraying an aqueous solution of a surfactant onto the surface of the carbon fiber reinforced plastic that has been roughened, then washing with water, and then drying. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 27,
In the washing step, the carbon fiber reinforced plastic is washed with water and then dried. A method for producing a composite of a metal alloy and a fiber reinforced plastic according to claim 27,
In the cleaning step, water is sprayed at a high pressure on the surface of the carbon fiber reinforced plastic that has been roughened, and then dried.