JP2022044319A - Different material friction stir joining method and different material friction stir joining member - Google Patents

Abstract

To provide a different material friction stir joining method for simply and efficiently performing direct bonding of titanium or a titanium alloy material and a thermoplastic resin material, and a different material friction stir joining member having high joint strength obtained from the same.SOLUTION: A different material friction stir joining method of titanium or a titanium alloy material and a thermoplastic resin material includes: a first step of subjecting a joined region of titanium or a titanium alloy material to silane coupling treatment; a second step of bringing a thermoplastic resin material into contact with the joined region subjected to the silane coupling treatment, and forming a joined interface; and a third step of press-fitting a friction stir joining tool into the titanium or titanium alloy material, raising a temperature of the joined interface, and applying a joint pressure to the joined interface.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for friction stir welding of different materials of titanium or a titanium alloy material and a thermoplastic resin material, and a member for friction stir welding of different materials obtained by the method.

From the viewpoint of improving fuel efficiency and reducing environmental load, weight reduction of various transportation equipment is eagerly desired, and the use of resin materials such as carbon fiber reinforced plastic (CFRP) for aircraft and automobiles is being actively studied.

Against this background, it is indispensable to establish joining technology for joining various metal materials and resin materials, and development of joining technology for joining steel, aluminum alloys and magnesium alloys with resin materials is underway.

Here, when mechanically fastening with bolts or the like, it is necessary to process the material to be joined, and it is unavoidable that the weight increases due to the fastening member. Further, when joining using an adhesive, it is not possible to impart sufficient joining strength and reliability to the joined portion.

On the other hand, for example, Patent Document 1 (Re-Table 2017-065256) provides a metal resin bonding member capable of exhibiting high bonding strength and the like and a method for manufacturing the same without mainly using the anchor effect. A metal resin comprising a metal body having an iron oxide layer formed on the surface of an iron-based base material made of iron or an iron alloy, and a resin body bonded to the metal body via the iron oxide layer. The iron oxide layer, which is a bonding member, has a thickness of 50 nm to 10 μm, Fe: 60 to 40 at%, O: 40 to 60 at% on the outermost surface side, and at least magnetite (Fe ₃ O ₄ ). ) Is included in the metal-resin bonding member.

In the metal-resin bonding member described in Patent Document 1, the iron oxide layer formed on the surface of the iron-based base material is considered to be in an electron-deficient state and in an energetically high active state. Assuming that it will chemically bond with C, O, H, N, P, S, etc. near the bonded surface of the body, and as a result, the metal body and the resin body will be firmly bonded. There is.

Further, in Patent Document 2 (Japanese Unexamined Patent Publication No. 2012-170975), a metal member and a resin member can be directly bonded without interposing a resin layer between the metal member and the resin member. A method, and for the purpose of providing a joint between a metal member and a resin member, the metal member and the resin member are brought into contact with each other without a resin layer interposed therebetween, and a rotating rotating tool is used for the metal member. The friction applied to the metal member by inclining it so that the inclination angle θ of the axis of the rotation tool with respect to the normal of the surface satisfies the condition of 0 ° <θ≤5 ° and pressing it against the surface of the metal member. A method for joining a metal member and a resin member, which comprises joining the metal member and the resin member by energy, has been proposed.

In the method of joining the metal member and the resin member described in Patent Document 2, since the metal member and the resin member are brought into contact with each other without a resin layer interposed therebetween, the metal member and the resin member are brought into contact with each other at low cost because the resin layer is not used. It is possible to easily join, and the types of resin members that can be joined to metal members increase. Further, it is said that the metal member and the resin member can be joined at any place.

Re-table 2017-06525 No. Japanese Unexamined Patent Publication No. 2012-170975

The metal-resin bonding member described in Patent Document 1 and the method for producing the same are indispensable for forming magnetite (Fe ₃ O ₄ ), and cannot be applied to other than iron-based metals. Further, the method for joining the metal member and the resin member described in Patent Document 2 is to achieve the joining between the metal member and the resin member via the metal oxide film formed on the surface of the metal member. In the example, only the result of joining the aluminum alloy or magnesium alloy and the resin member is shown. That is, the method of joining the thermoplastic resin and titanium or the titanium alloy material is not shown in any patent document, and the actual situation is that there is no suitable direct joining method for the combination.

Here, when the steel material, aluminum alloy, magnesium alloy, etc. disclosed in Patent Documents 1 and 2 come into contact with a resin material such as a thermoplastic CFRP material by direct bonding, the metal material side that is base to the resin material Corrosion progresses easily (galvanic corrosion). On the other hand, titanium or a titanium alloy is electrochemically stable, and even if it is directly bonded to a resin material, the problem of corrosion does not occur. For this reason, titanium or titanium alloys are extremely suitable materials for multi-materialization with resin materials.

In view of the above problems in the prior art, an object of the present invention is a dissimilar friction stir welding method for directly bonding titanium or a titanium alloy material and a thermoplastic resin material directly and easily and efficiently, and a high level obtained by the method. It is an object of the present invention to provide a dissimilar material friction stir welding member having a joint strength.

As a result of intensive studies on the relationship between the surface condition of the material to be welded and the friction stir welding conditions and the joint strength in order to achieve the above object, the present inventor has made an appropriate silane coupling agent on the surface of titanium or a titanium alloy material. In addition to the treatment with the above, it has been found that it is extremely effective to accurately control the temperature of the interface to be joined during friction stir welding, and the present invention has been reached.

That is, the present invention
A friction stir welding method between titanium or a titanium alloy material and a thermoplastic resin material.
The first step of applying a silane coupling treatment to the bonded region of the titanium or titanium alloy material, and
The second step of abutting the thermoplastic resin material on the bonded region subjected to the silane coupling treatment to form a bonded interface, and
Having a third step of press-fitting a friction stir welding tool into the titanium or a titanium alloy material to raise the temperature of the interface to be welded and applying a bonding pressure to the interface to be welded.
Provided is a friction stir welding method for different materials.

In the dissimilar material friction stir welding method of the present invention, it is preferable that the temperature of the interface to be bonded is equal to or higher than the melting temperature of the thermoplastic resin material and lower than the decomposition temperature in the third step. By setting the temperature of the interface to be bonded to be equal to or higher than the melting temperature of the thermoplastic resin material, the functional group introduced into the bonded region of titanium or the titanium alloy material by the silane coupling treatment reacts with the thermoplastic resin material and becomes strong. It is possible to form a flexible bonding interface. On the other hand, by setting the temperature of the interface to be bonded to be equal to or lower than the decomposition temperature of the thermoplastic resin material, it is possible to suppress the decrease in strength of the bonded portion due to the thermal decomposition of the thermoplastic resin material. Here, the decomposition temperature of the thermoplastic resin material is the temperature at which gasification of the thermoplastic resin material starts.

Further, in the dissimilar material friction stir welding method of the present invention, it is preferable that the thermoplastic resin material is a carbon fiber reinforced plastic (CFRP) material. Since an extremely strong joint is formed by the dissimilar friction stirring joining method of the present invention, even when a high-strength carbon fiber reinforced plastic (CFRP) material and a titanium or titanium alloy material are joined, the carbon fiber is concerned. It is possible to form a bonded structure that takes advantage of the mechanical properties of the reinforced plastic (CFRP) material.

Further, in the dissimilar material friction stir welding method of the present invention, the thermoplastic resin material has an amide group, and in the first step, an epoxy group is formed on the surface of the bonded region of the titanium or titanium alloy material. That is preferable. The type of the thermoplastic resin material and the functional group introduced into the bonded region of the titanium or the titanium alloy material by the silane coupling treatment are not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known thermoplastic resins are used. Although it can be used as a material and a functional group, the thermoplastic resin material has an amide group, and by forming an epoxy group on the surface of the bonded region of titanium or a titanium alloy material, a high-strength bonding interface is surely obtained. Obtainable.

Further, in the dissimilar material friction stir welding method of the present invention, it is preferable that the temperature of the interface to be welded is 220 to 350 ° C. in the third step. The melting temperature and decomposition temperature differ depending on the type and state of the thermoplastic resin material, but by setting the temperature of the interface to be bonded to 220 to 350 ° C, the thermoplasticity generally used as a structural member by bonding with a metal member. It can cover most of the resin materials.

Further, in the dissimilar material friction bonding method of the present invention, it is preferable that the bonding pressure is 5 to 20 MPa in the third step. By setting the bonding pressure to 5 MPa or more, the thermoplastic resin material and the titanium or titanium alloy material can be sufficiently adhered, and by setting the bonding pressure to 20 MPa or less, deterioration of the friction stir welding tool can be suppressed. ..

Further, in the dissimilar material friction joining method of the present invention, it is preferable that the concentration of the silane coupling agent used for the silane coupling treatment is 2% or more in the first step. The concentration of the silane coupling agent is not particularly limited as long as the effect of the present invention is not impaired, and may be appropriately adjusted in relation to the joint strength of the obtained dissimilar friction stir welding member, but it may be set to 2% or more. , A sufficient amount of functional groups that contribute to the bonding strength can be introduced into the surface of the bonded region of the tongue or titanium alloy material.

Further, the present invention
It is a lap friction stir welding member of titanium or titanium alloy material and thermoplastic carbon fiber reinforced plastic (CFRP) material.
The resin portion of the carbon fiber reinforced plastic (CFRP) material has an amide group and has an amide group.
The presence of a crystallization region in the carbon fiber reinforced plastic (CFRP) material near the bonding interface,
Also provided is a dissimilar material friction stir welding member.

In the dissimilar material friction stir welding member of the present invention, the amide group present in the resin portion of the carbon fiber reinforced plastic (CFRP) material contributes to the bonding with titanium or the titanium alloy material. Although it is difficult to detect by various analyses, a strong bonding interface is formed by the reaction between the functional group and the amide group on the surface of the titanium or titanium alloy material to be bonded.

In the dissimilar material friction stir welding member of the present invention, in a tensile test piece having a friction stir welding wire having a length of 15 mm, the tensile shear strength in the direction perpendicular to the friction stir welding wire is 3.0 kN or more. Is preferable. When the tensile shear strength is 3.0 kN or more, a dissimilar friction stir welding member made of titanium or a titanium alloy material and a thermoplastic carbon fiber reinforced plastic (CFRP) material can be applied to various structures. .. Since it is difficult to accurately measure the area of the actual joint, the load is specified instead of the stress. Further, the tensile shear strength is a value in a state where there is no mechanical fastening or an adhesive region due to an adhesive.

Further, in the dissimilar material friction stirring joining member of the present invention, the difference between the hardness of the region where the material breaks in the tensile shear test using the tensile test piece and the hardness of the base material of the carbon fiber reinforced plastic (CFRP) material is 5 Hv. It is preferably within. When the hardness of the fractured region and the hardness of the member are close to each other, it is possible to obtain a good friction stir welding member made of different materials in which the joint portion does not become a singular point.

The dissimilar material friction stir welding member of the present invention can be easily obtained by the dissimilar material friction stir welding method of the present invention.

INDUSTRIAL APPLICABILITY According to the present invention, a dissimilar material friction stir welding method for directly bonding titanium or a titanium alloy material and a thermoplastic resin material directly and efficiently, and a dissimilar material friction stir welding member having high joint strength obtained by the method are provided. be able to.

It is a process drawing of the dissimilar material friction stir welding of this invention. It is a schematic diagram of the dissimilar material friction stir welding of this invention. It is the schematic sectional drawing of the dissimilar material friction stir welding member which concerns on one aspect of this invention. It is a schematic diagram of the epoxy group introduction by the silane coupling treatment. It is a schematic diagram which shows the collection position, the shape and the size of a test piece. It is a graph which shows the tensile shear strength of the joint obtained by the examination of the silane coupling agent. It is an appearance photograph of the test piece after the tensile test about the joint obtained by the examination of the silane coupling agent. It is the SEM-EDS result of the surface of the pure titanium plate of the fracture part after the tensile test about the joint obtained by the examination of the silane coupling agent. It is a graph which shows the tensile shear strength of the joint obtained by the examination of the friction stir welding condition. It is a graph which shows the maximum temperature reached in the vicinity of the interface to be welded during friction stir welding. It is an external photograph of the test piece after the tensile test about the joint obtained by the examination of the friction stir welding condition. It is a graph which shows the temperature change in the vicinity of the interface to be welded during friction stir welding. It is a schematic diagram which shows the bonding mechanism by the reaction of an epoxy group and an amide group. It is a graph which shows the joining load and joining pressure during friction stir welding. It is an SEM photograph of the joint section cross section of the joint obtained at 100, 125, 150 and 175 rpm. FIG. 3 is an optical micrograph of a cross section of a joint obtained at 200 and 300 rpm. It is an enlarged photograph of the broken line area in FIG.

Hereinafter, a typical embodiment of the dissimilar material friction stir welding method of the present invention and the dissimilar material friction stir welding member obtained by the method will be described in detail with reference to the drawings, but the present invention is not limited to these. .. In the following description, the same or corresponding parts may be designated by the same reference numerals, and duplicate description may be omitted. Further, since the drawings are for conceptually explaining the present invention, the dimensions of each component represented and their ratios may differ from the actual ones.

(1) Dissimilar Material Friction Stir Welding Method FIG. 1 shows a process diagram of the dissimilar material friction stir welding of the present invention. The friction stir welding of different materials of the present invention comprises a first step (S01) of applying a silane coupling treatment to a titanium or titanium alloy material to be joined, a second step (S02) of forming an interface to be joined, and friction stir welding. It has a third step (S03) of applying the above. Further, FIG. 2 shows a schematic diagram of the friction stir welding of different materials of the present invention. Hereinafter, each step will be described in detail.

(1-1) First step (S01: Silane coupling treatment)
The first step (S01) is a step for applying a silane coupling treatment to the bonded region of titanium or the titanium alloy material 2. By subjecting the bonded region of titanium or the titanium alloy material 2 to a silane coupling treatment, a functional group that contributes to bonding with the resin material can be imparted to the surface of the bonded region.

When the silane coupling agent and distilled water are mixed, silanol (Si-OH) is formed by hydrolysis. In addition, silanol groups show high affinity with each other and form -Si-O-Si- bonds and some hydroxyl groups by condensation reaction. The silane coupling treatment can be performed by immersing the bonded region of titanium or the titanium alloy material 2 in an aqueous solution of a silane coupling agent and distilled water, taking it out, and performing a heat treatment (drying treatment) at an appropriate temperature. can.

The silane coupling agent in which the hydrolysis and the condensation reaction have proceeded physically absorbs the hydroxyl group on the surface of titanium or the titanium alloy 2 by hydrogen bonding. Further, by heating, the hydrogen bond between silanol and the hydroxyl group of titanium or the titanium alloy material 2 is converted into an —Si—O—Ti— bond. By these processes, a bonded region having an organic group can be obtained.

Here, in order to form a good friction stir welded portion made of titanium or a titanium alloy material 2 and a thermoplastic resin material 4, a functional group possessed by the thermoplastic resin material 4 and a silane coupling agent are introduced. It is necessary that the functional group has good reactivity. That is, it is necessary to appropriately select an appropriate silane coupling agent according to the thermoplastic resin material 4 to be bonded.

For example, when the thermoplastic resin material 4 is "polyamide 6", since the polyamide 6 has an amide group, it can react and bond with an epoxy group. That is, when the thermoplastic resin material 4 having the polyamide 6 and the titanium or the titanium alloy material 2 are bonded, a strong bonding interface can be formed by using a silane coupling agent having an epoxy group.

The concentration of the aqueous solution of the silane coupling agent is not particularly limited as long as the effect of the present invention is not impaired, but is preferably 2% or more. By setting the concentration of the silane coupling agent aqueous solution to 2% or more, the titanium or titanium alloy material 2 can be immersed in the silane coupling agent aqueous solution only once to obtain a functional group having sufficient bonding strength in the bonded region. Can be introduced in. If the concentration of the silane coupling agent aqueous solution is low, the immersion and drying may be performed a plurality of times.

The method for drying the aqueous solution of the silane coupling agent adhering to the surface of the bonded region of titanium or the titanium alloy material 2 is not particularly limited as long as the effect of the present invention is not impaired, and various conventionally known methods can be used. can. For example, the titanium or the titanium alloy material 2 to which the aqueous solution of the silane coupling agent is attached may be held in a vacuum furnace at 100 to 140 ° C. for about 1 hour.

(1-2) Second step (S02: Formation of interface to be joined)
The second step is to abut the bonded region of the titanium or titanium alloy material 2 subjected to the silane coupling treatment in the first step (S01) with the thermoplastic resin material 4 to form a bonded interface. This is the process.

It is not necessary that the entire area of the titanium or the titanium alloy material 2 in contact with the thermoplastic resin material 4 is subjected to the silane coupling treatment, and it is sufficient that the region to which the silane coupling treatment is applied is included.

It is preferable that the titanium or the titanium alloy material 2 and the thermoplastic resin material 4 are fixed to such an extent that the positions do not change during friction stir welding in the third step (S03). On the other hand, in friction stir welding, since the bonding pressure is applied to the bonded region by the friction stir welding tool, it is not necessary to separately apply a pressing force to bring the surfaces to be bonded into close contact with each other.

(1-3) Third step (S03: Friction stir welding)
The third step (S03) is a step of performing friction stir welding on the bonded region.

Friction stir welding is called FSW (Friction Stir Welding), and the ends of each of the two metal materials to be welded to be welded are butted against each other, and a protrusion (probe) provided at the tip of the rotation tool is formed. It is a method of joining two metal members by inserting them between the ends of both and moving the rotation tool while rotating it along the longitudinal direction of these ends.

The "friction stir welding" in the present invention includes friction stir line joining in which the rotary tool is rotated and moved in the joining direction, and friction stir spot welding in which the rotary tool is rotated and not moved at the joint site. It means a lap friction stir welding in which a rotating tool is inserted from the side of one of the materials to be welded by laying them on top of each other. Hereinafter, as a typical embodiment, friction stir welding in which the rotation tool is rotated and moved in the joining direction will be described in detail.

The rotated friction stir welding tool 6 is press-fitted from the side of the titanium or titanium alloy material 2 above the area to be welded to generate frictional heat and apply the bonding pressure in a direction substantially perpendicular to the interface to be welded. .. In this state, the friction stir welding tool 6 can be moved along the bonded region to form a linear bonding interface.

A protrusion having an appropriate size and shape may be provided on the bottom surface of the friction stir welding tool 6, but the life of the friction stir welding tool 6 and the temperature distribution and applied pressure of the interface to be welded during friction stir welding. From the viewpoint of ensuring the uniformity of the surface, it is preferable to have a smooth bottom surface shape without protrusions. The amount of the friction stir welding tool 6 inserted from the surface of titanium or the titanium alloy material 2 does not need to be larger than necessary, and should be reduced as long as the bonding temperature and bonding pressure at the interface to be bonded are appropriate values. Is preferable. By reducing the insertion amount, the life of the friction stir welding tool 6 can be extended.

Further, the material of the friction stir welding tool 6 is not particularly limited as long as the effect of the present invention is not impaired, and various conventionally known materials used for the friction stir welding tool can be used. For example, cemented carbides made of tungsten carbide (WC), cobalt (Co), nickel (Ni), cobalt (Co) -based alloys, tungsten (W) alloys, refractory metals such as iridium (Ir) and their alloys. Alternatively, it can be made of ceramics such as Si ₃ N ₄ and the like.

The main joining parameters in friction stir welding are the rotation speed, moving speed, joining pressure and advance angle of the friction stir welding tool 6, and these are the temperatures of the interface to be joined during friction stir welding of the thermoplastic resin material 4. It may be appropriately adjusted so that it is equal to or higher than the melting temperature and lower than the decomposition temperature. Further, it is preferable to flow an inert gas such as argon through the region to be bonded to suppress the oxidation reaction of the material to be bonded and the tool.

The temperature of the interface to be welded during friction stir welding is preferably 220 to 350 ° C. The melting temperature and decomposition temperature differ depending on the type and state of the thermoplastic resin material 4, but by setting the temperature of the interface to be bonded to 220 to 350 ° C, the heat generally used as a structural member by bonding with a metal member. Most of the plastic resin materials 4 can be covered. A more preferable temperature of the interface to be joined is 250 to 320 ° C, and the most preferable temperature is 290 to 310 ° C.

The time for holding the bonding interface at an appropriate temperature (above the melting temperature of the thermoplastic resin material 4 and below the decomposition temperature) during friction stir welding is preferably 1 second or longer, more preferably 3 seconds or longer. Most preferably, it is 5 seconds or longer. By holding the bonding interface in an appropriate temperature range, the titanium or titanium alloy material 2 and the thermoplastic resin material 4 can be reliably bonded. On the other hand, if the holding time is too long, the thermoplastic resin material 4 may be deteriorated, so that it is preferably 20 seconds or less.

Further, the bonding pressure applied to the interface to be bonded by friction stir welding is preferably 5 to 20 MPa. By setting the bonding pressure to 5 MPa or more, the thermoplastic resin material 4 and the titanium or titanium alloy material 2 can be sufficiently adhered, and by setting the bonding pressure to 20 MPa or less, deterioration of the friction stir welding tool 6 is suppressed. be able to. A more preferable joining pressure is 8 to 17 MPa, and a most preferable joining pressure is 10 to 15 MPa.

The direction of rotation of the friction stir welding tool 6 can be clockwise or counterclockwise, but the friction stir welding tool is located on the side where the distance from the bonded region to the end of the titanium or titanium alloy material 2 is short. It is preferable to set 6 so that the rotation direction and the movement direction are opposite (backward side). In friction stir welding, the joining temperature tends to be higher on the side (advance side) where the rotation direction and the moving direction of the friction stir welding tool 6 are the same. Further, when the distance from the insertion position of the friction stir welding tool 6 to the end portion of the titanium or the titanium alloy material 2 is short, the bonding temperature tends to be higher due to heat storage as compared with the case where the distance is long. From these relationships, the temperature distribution in the bonding region can be made uniform by setting the side where the distance from the insertion position of the friction stir welding tool 6 to the end of the titanium or titanium alloy material 2 is short as the receding side. ..

The composition of titanium or the titanium alloy material 2 is not particularly limited as long as the effect of the present invention is not impaired, and various conventionally known titanium or titanium alloys can be used. As the titanium alloy, for example, a widely used Ti-6Al-4V alloy, various highly processable titanium alloys, and the like can be used. Further, the plate thickness of the titanium or the titanium alloy material 2 is not particularly limited as long as the effect of the present invention is not impaired, and for example, a plate material of about 1 to 5 mm can be preferably used.

Further, the type of the thermoplastic resin material 4 is not particularly limited as long as the effect of the present invention is not impaired, and various conventionally known thermoplastic resin materials can be used, but they may have an amide group. preferable. As the thermoplastic resin material having an amide group, for example, polyamide 6 can be exemplified, and carbon fiber reinforced plastic (CFRP) using polyamide 6 as a matrix can be preferably used. As other thermoplastic resins, polypropylene resin (melting point: 170 ° C., pyrolysis temperature: 328 to 410 ° C.), nylon 66 resin (melting point: 268 ° C., pyrolysis temperature: 310 to 380 ° C.), polycarbonate resin ( Melting point: 150 ° C., pyrolysis temperature: 420 to 620 ° C.), nylon 6 resin (melting point: 225 ° C., pyrolysis temperature: 310 to 380 ° C.) and the like can be mentioned.

(2) Dissimilar Material Friction Stir Welding Member FIG. 3 shows a schematic cross-sectional view of the dissimilar material friction stir welding member according to one aspect of the present invention. The dissimilar material friction stir welding member 10 is formed by laminating and joining titanium or a titanium alloy material 2 and a thermoplastic carbon fiber reinforced plastic (CFRP) material 12 by a friction stir welding portion 14. The resin portion of the carbon fiber reinforced plastic (CFRP) material 12 has an amide group.

A crystallization region 16 exists in the vicinity of the junction interface in the friction stir welding portion 14. In the crystallized region 16, the carbon fiber reinforced plastic (CFRP) material 12 was sufficiently softened during the friction stirring joining, and the surface of the titanium or titanium alloy material 2 and the surface of the carbon fiber reinforced plastic (CFRP) material 12 were in close contact with each other. It means that. Further, the friction stir welding portion 14 has no groove-like or void-like defects. This means that during friction stir welding, the temperature at the bonding interface was suppressed below the thermal decomposition of the thermoplastic resin material, which is the matrix of the carbon fiber reinforced plastic (CFRP) material 12.

In the dissimilar material friction stir welding member 10, the tensile test piece having the friction stir welding portion 14 (friction stir welding line) having a length of 15 mm has a tensile shear strength of 3.0 kN in the direction perpendicular to the friction stir welding portion 14. The above is preferable. When the tensile shear strength is 3.0 kN or more, the dissimilar friction stir welding member 10 made of titanium or titanium alloy material 2 and carbon fiber reinforced plastic (CFRP) material 12 can be applied to various structures. .. The tensile shear strength is more preferably 3.5 kN or more, and most preferably 3.7 kN or more.

In the dissimilar material friction stir welding member 10, it is preferable that the difference between the hardness of the region where the material breaks in the tensile shear test and the hardness of the base material of the carbon fiber reinforced plastic (CFRP) material 12 is within 5 Hv. When the hardness of the fractured region and the hardness of the member are close to each other, it is possible to obtain a good friction stir welding member 10 made of different materials in which the joint portion does not become a singular point. Here, the fracture region is near the outer edge of the friction stir welding portion 14.

Although the typical embodiments of the present invention have been described above, the present invention is not limited to these, and various design changes are possible, and all of these design changes are included in the technical scope of the present invention. Will be.

Hereinafter, the dissimilar material friction stir welding method and the dissimilar material friction stir welding member of the present invention will be further described in Examples, but the present invention is not limited to these examples.

In the arrangement shown in FIG. 2, an industrial pure titanium (TP-340) plate having a thickness of 2 mm, a width of 50 mm and a length of 150 mm and a carbon fiber reinforced plastic having a thickness of 3 mm, a width of 50 mm and a length of 150 mm (20% by mass). Polyamide 6) plates to which carbon fibers were added were friction-stir welded.

(1) Examination of silane coupling agent As a preliminary treatment for friction stir welding, the surface of a pure titanium plate was subjected to a silane coupling treatment. Here, in order to examine an appropriate concentration of the silane coupling agent aqueous solution used for the silane coupling treatment, the silane coupling agent and pure water are mixed, and the concentrations are 0%, 0.5%, 1.5%, and so on. 2.5% and 3.5% silane coupling agent aqueous solutions were prepared. The silane coupling agent used is OFS-6040 (3-Glycydoxypropyl trimethoxysilane, Epoxy functional), and an epoxy group can be introduced on the surface of a pure titanium plate. A schematic diagram of the introduction of the epoxy group is shown in FIG.

After polishing the surface (bonded region) of the pure titanium plate with # 3000 abrasive paper, it was immersed in a silane coupling agent aqueous solution of each concentration, and then kept in a vacuum furnace at 120 ° C. for 1 hour to dry. ..

Then, the surface (bonding region) of the pure titanium plate and the carbon fiber reinforced plastic plate were overlapped in the manner shown in FIG. 2, and a friction stir welding tool was press-fitted from the pure titanium plate side to perform friction stir welding.

The conditions for friction stir welding are a columnar diameter of 15 mm with a smooth bottom surface with no protrusions, a tool rotation speed of 300 rpm, a tool movement speed (joining speed) of 100 mm / min, and a tool advance angle of 3 °. Friction stir welding was performed using a friction stir welding tool made of super hard alloy. Argon gas was flowed through the joint, and the bottom surface of the tool was inserted 0.9 mm from the surface of the pure titanium plate.

In order to evaluate the strength of the joint, a tensile shear test was performed on the obtained dissimilar joint. FIG. 5 shows the collection position, shape and size of the test piece. The test piece for the tensile shear test is taken from A in FIG. 5 and has a width of 15 mm. Further, the tensile speed of the tensile shear test was set to 0.5 mm / min, and the measurement was performed three times.

The obtained tensile shear strength is shown in FIG. 6, a photograph of the appearance of the test piece after the tensile test is shown in FIG. 7, and the SEM-EDS result of the surface of the pure titanium plate at the fracture portion is shown in FIG. The cross-sectional sample for microstructure observation was subjected to mechanical polishing up to polishing paper # 4000 and then mirror-polished using a 1 μm diamond suspension, and JEOL JSM-7001FA was used as the SEM. The sampling position, shape and size of the tissue observation sample are shown as B in FIG.

No conjugate could be obtained without the addition of the silane coupling agent. In addition, when a silane coupling agent was added, a joint was formed, but under the set friction stir welding conditions, the tensile shear strength was less than 1 kN in all cases (Fig. 6), all at the joint interface. (Fig. 7). On the other hand, when the concentration of the silane coupling agent is 2.5% or more, carbon due to the carbon fiber reinforced plastic plate is clearly observed on the surface of the pure titanium plate at the joint, and the silane coupling agent makes a strong bond. It can be confirmed that the interface is formed (Fig. 8).

That is, a strong bonding interface can be formed between the pure titanium plate and the carbon fiber reinforced plastic plate by appropriate silane coupling treatment and friction stir welding, but the strength of the carbon fiber reinforced plastic plate is reduced by friction stir welding. Need to be suppressed.

(2) Examination of Friction Stir Welding Conditions Except that the concentration of the silane coupling agent aqueous solution was kept constant at 3.5% and the rotation speed of the tool was set to 50, 100, 125, 150, 175, 200, 250, 300 rpm. Friction stir welding was performed in the same manner as in the case of (1).

FIG. 9 shows the tensile shear strength of each joint obtained in the same manner as in the case of (1). In addition, the temperature near the interface to be joined during bonding was measured with a thermocouple, and the obtained results are also shown in FIG. A schematic diagram of the joining temperature measurement situation is shown in FIG.

As shown in FIG. 9, there is a clear range of tool rotation speeds at which a high tensile shear strength of 3.0 kN or more can be obtained (125 to 175 rpm), and the temperature near the bonded interface in the friction stir welding is carbon fiber reinforced. The melting point (225 ° C.) or higher and the decomposition temperature (350 ° C.) or lower of the base material (polyamide 6) of the plastic are set. Further, FIG. 11 shows an external photograph of the test piece after the tensile test, and all the joints obtained at 125 to 175 rpm have the base material fractured on the carbon fiber reinforced plastic plate side. Further, in these joints, the Vickers hardness at the fracture position was measured and found to be 18 to 20 Hv. The Vickers hardness of the carbon fiber reinforced plastic plate is also 18 to 20 Hv, and it can be seen that the breaking position hardly changes due to the joining.

FIG. 12 shows the temperature change in the vicinity of the bonded portion obtained by using a thermocouple when the tool rotation speeds are 100, 125, 150 and 175 rpm. The time for which the temperature in the region is maintained above the melting point of the polyamide 6 is 5.0 seconds at 125 rpm, 8.8 seconds at 150 rpm, and 10.3 seconds at 175 rpm, which is a silane cup. It is considered that a sufficient time was obtained for the epoxy group introduced by the ring agent and the amide group of the polyamide 6 to react sufficiently. On the other hand, in the case of 100 rpm, the bonding temperature is slightly higher than the melting point of the polyamide 6, but the time held in the temperature range is as short as 1.3 seconds, so that a strong bonding interface is not formed. It seems to be.

FIG. 13 schematically shows the bonding mechanism due to the reaction between the epoxy group formed on the surface of the pure titanium plate and the amide group of the polyamide 6. It is considered that the epoxy group and the amide group were bonded by the insertion reaction and the additional reaction, and the polyamide 6 in the vicinity of the interface to be bonded was melted to promote these reactions and form a strong bonding interface.

FIG. 14 shows the joining load and the joining pressure applied to the interface to be joined by the friction stir welding tool during the friction stir welding. Since the polyamide 6 softens and / or decomposes as the rotation speed of the tool increases, the bonding load and bonding pressure decrease, but at 125 to 175 rpm, where the bonding temperature is above the melting point of the polyamide 6 and below the decomposition temperature. It can be seen that an appropriate bonding pressure of 5 to 20 MPa is marked.

FIG. 15 shows SEM photographs of joint cross sections obtained at 100, 125, 150 and 175 rpm. When the bonding temperature is low at 100 rpm, there is a gap between the pure titanium plate and the carbon fiber reinforced plastic plate, and a good bonding interface is not formed. On the other hand, at 125 to 175 rpm, where the bonding temperature is equal to or higher than the melting point of the polyamide 6 and lower than the decomposition temperature, a bonding interface in which the pure titanium plate and the carbon fiber reinforced plastic plate are in close contact is formed, and no defects or the like are observed.

Optical micrographs of the cross sections of the joints obtained at 200 and 300 rpm are shown in FIG. Further, an enlarged photograph of the area surrounded by the broken line in FIG. 16 is shown in FIG. It can be seen that under the friction stir welding condition where the bonding temperature is equal to or higher than the decomposition temperature of the polyamide 6, a large groove due to the decomposition of the polyamide 6 is formed between the pure titanium plate and the carbon fiber reinforced plastic plate.

Based on the above results, the dissimilar material friction stir welding method of the present invention, which combines an appropriate silane coupling treatment and friction stir welding in which the bonding temperature is equal to or higher than the melting point of the thermoplastic resin material and lower than the decomposition temperature, is thermoplastic to the titanium material. The dissimilar material friction stir welding member of the present invention, which can form an extremely strong bonding interface with the resin material and is obtained by the dissimilar material friction stir welding method, has a tensile test having a friction stir welding wire having a length of 15 mm. In one piece, it was confirmed that a joint portion having a tensile shear strength of 3.0 kN or more in the direction perpendicular to the friction stir welding line was formed.

2 ... Titanium or titanium alloy material,
4 ... Thermoplastic resin material,
6 ... Friction stir welding tool,
10 ... Friction stir welding member of different materials,
12 ... Carbon fiber reinforced plastic material,
14 ... Friction stir welding,
16 ... Crystallization region.

Claims (10)

A friction stir welding method between titanium or a titanium alloy material and a thermoplastic resin material.
The first step of applying a silane coupling treatment to the bonded region of the titanium or titanium alloy material, and
The second step of abutting the thermoplastic resin material on the bonded region subjected to the silane coupling treatment to form a bonded interface, and
Having a third step of press-fitting a friction stir welding tool into the titanium or a titanium alloy material to raise the temperature of the interface to be welded and applying a bonding pressure to the interface to be welded.
A method of friction stir welding of different materials. In the third step, the temperature of the interface to be joined is set to be equal to or higher than the melting temperature of the thermoplastic resin material and lower than the decomposition temperature.
The dissimilar material friction stir welding method according to claim 1. Using the thermoplastic resin material as a carbon fiber reinforced plastic (CFRP) material,
The dissimilar material friction stir welding method according to claim 1 or 2. The thermoplastic resin material has an amide group and has
In the first step, forming an epoxy group on the surface of the bonded region of the titanium or the titanium alloy material.
The dissimilar material friction stir welding method according to any one of claims 1 to 3. In the third step, the temperature of the interface to be joined is set to 220 to 350 ° C.
The dissimilar material friction stir welding method according to any one of claims 1 to 4. In the third step, the joining pressure should be 5 to 20 MPa.
The dissimilar material friction stir welding method according to any one of claims 1 to 5. In the first step, the concentration of the silane coupling agent used for the silane coupling treatment shall be 2% or more.
The dissimilar material friction stir welding method according to any one of claims 1 to 6. It is a lap friction stir welding member of titanium or titanium alloy material and thermoplastic carbon fiber reinforced plastic (CFRP) material.
The resin portion of the carbon fiber reinforced plastic (CFRP) material has an amide group and has an amide group.
The presence of a crystallization region in the carbon fiber reinforced plastic (CFRP) material near the bonding interface,
A friction stir welding member made of different materials. In a tensile test piece having a friction stir welding wire having a length of 15 mm, the tensile shear strength in the direction perpendicular to the friction stir welding wire shall be 3.0 kN or more.
The dissimilar material friction stir welding member according to claim 8. The difference between the hardness of the region that breaks in the tensile shear test using the tensile test piece and the hardness of the base material of the carbon fiber reinforced plastic (CFRP) material is within 5 Hv.
The dissimilar material friction stir welding member according to claim 9.

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