JP5725424B2 - Magnesium alloy parts - Google Patents

Description

  The present invention relates to a magnesium alloy member that can be suitably used for a casing of a portable electric device.

  Magnesium alloys containing various additive elements in magnesium have been used as constituent materials for various members such as casings of portable electric and electronic devices such as mobile phones and notebook personal computers, and automobile parts.

  Patent Document 1 discloses a magnesium alloy material made of an alloy equivalent to ASTM standard AZ91 alloy and excellent in impact resistance. This magnesium alloy material is manufactured by subjecting a cast material manufactured by a continuous casting method to solution treatment, rolling, polishing, and the like in order. Since magnesium is an active metal, the surface of the magnesium alloy material is subjected to anticorrosion treatment such as chemical conversion treatment.

JP 2011-140712 A

  In some cases, reinforcing bosses or ribs formed of a resin molded body are joined to the magnesium alloy material. For example, the boss can form a female screw on its inner peripheral surface and can be screwed into the male screw. Joining a resin molded body to the magnesium alloy material described in the cited document 1 has been studied, and it is desired to join both firmly.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a magnesium alloy member in which a resin molded body is firmly joined.

  The present inventors considered that a chemical film was formed on the surface of the magnesium alloy material, and a resin molded body was joined to the chemical film by injection molding. Thus, a magnesium alloy member in which the chemical film formation and the resin molded body were joined was produced by performing uneven surface processing on the chemical film forming side and entangling the resin with the uneven part. It was thought that by defining the irregularities (surface roughness) of this surface processing, it was possible to secure a bonding area between the chemical film formation and the resin molded body, and to firmly bond both, but that alone would maintain the bonding state Was difficult. Therefore, as a result of investigating the firm bonding between the chemical film formation and the resin molded body, the inventors have found that it is important to define the surface area ratio in addition to the surface roughness. The present invention is based on the above findings.

  The present invention includes a base material made of a magnesium alloy containing Al in excess of 7.5% by mass, a chemical film formed on the surface of the base material, and a resin molding directly joined to the chemical film. The surface roughness of the chemical film formation is 10 μm or more in Rz and the surface area ratio is 2 or more.

  According to this configuration, it is possible to secure a sufficient bonding area between the chemical film formation and the resin molded body and firmly bond both.

  As one form of this invention, the said chemical film formation has the form comprised from the phosphoric acid compound.

  The phosphoric acid compound can suppress oxidation of the substrate and is excellent in corrosion resistance.

  As one embodiment of the present invention, the chemical film formation may include a film thickness of 1 μm or less.

  According to this configuration, the surface shape of the chemical film formation can be a surface state in which the surface shape of the base material is accurately reflected.

  As an embodiment of the present invention, the magnesium alloy includes an embodiment in which Al is contained in an amount of 8.3 to 9.5 mass% and Zn is contained in an amount of 0.5 to 1.5 mass%.

  So-called AZ-based magnesium alloys tend to have better mechanical properties such as corrosion resistance and strength as the amount of Al increases. Therefore, according to this configuration, the corrosion resistance is very excellent and the mechanical characteristics are also excellent.

  As one form of this invention, the form which has a press work part by which the press work was given to at least one part of the said base material is mentioned.

  According to this structure, it can shape | mold to the magnesium alloy member of a desired shape, and can improve the designability of the member.

  The magnesium alloy member of the present invention can sufficiently secure a bonding area between the chemical film formation and the resin molded body, and can firmly bond both.

FIG. 1 is a SEM photograph of the surface of a magnesium alloy member, FIG. 1 (A) is Example 1 (200,000 times), FIG. 1 (B) is Comparative Example 1 (200,000 times), FIG. 1 (C). FIG. 1 shows Comparative Example 2 (200,000 times), and FIG. 1D shows Comparative Example 3 (300,000 times). FIG. 2 is a schematic diagram for explaining the measurement method. FIG. 2 (A) shows tensile bond strength measurement, and FIG. 2 (B) shows sideways maximum load measurement. FIG. 3 shows a magnesium alloy member according to the third embodiment.

The present invention will be described in detail below.
<Embodiment 1>
[Magnesium alloy members]
The magnesium alloy member of the present invention includes a base material made of a magnesium alloy containing 7.5% by mass or more of Al, a chemical film formed on the surface of the base material, and a resin molded body directly joined to the chemical film. Is provided. The feature of this magnesium alloy member is that the surface roughness of chemical film formation is 10 μm or more in Rz and the surface area ratio is 2 or more. Hereinafter, each configuration will be described in detail.

(Base material)
Examples of the base material include those having various compositions containing additive elements in magnesium (Mg) (remainder: Mg and impurities, Mg: 50% by mass or more). In particular, in the present invention, it is preferable to use an Mg—Al alloy containing at least 7.5% by mass of Al as an additive element. By containing more than 7.5% by mass of Al, the mechanical properties such as strength and plastic deformation resistance of the magnesium alloy itself can be improved, and the corrosion resistance is also excellent. Mg-Al alloys tend to have better mechanical properties such as strength and corrosion resistance as the amount of Al increases. However, exceeding 12 mass% causes a decrease in plastic workability, and the temperature of the material increases during rolling. Since it is necessary to heat, the content of Al is preferably 12% by mass or less.

  Additive elements other than Al were selected from Zn, Mn, Si, Ca, Sr, Y, Cu, Ag, Be, Sn, Li, Zr, Ce, Ni, Au, and rare earth elements (excluding Y and Ce) One or more elements are listed. When these elements are contained, the content of each element is 0.01 mass% or more and 10 mass% or less, preferably 0.1 mass% or more and 5 mass% or less. More specific Mg-Al alloys include, for example, AZ alloys (Mg-Al-Zn alloys, Zn: 0.2 mass% to 1.5 mass%) and AM alloys (Mg-Al-Mn alloys) according to ASTM standards. , Mn: 0.15 mass% to 0.5 mass%), Mg-Al-RE (rare earth element) alloy, AX alloy (Mg-Al-Ca alloy, Ca: 0.2 mass% to 6.0 mass%), AJ alloy (Mg—Al—Sr alloy, Sr: 0.2 mass% to 7.0 mass%) and the like. In particular, the form containing 8.3 mass% to 9.5 mass% of Al is excellent in strength and corrosion resistance. More specifically, an Mg—Al alloy containing 8.3 mass% to 9.5 mass% Al and 0.5 mass% to 1.5 mass% Zn, typically AZ91 alloy. When at least one element selected from Y, Ce, Ca and rare earth elements (excluding Y and Ce) is contained in a total amount of 0.001% by mass or more, preferably 0.1% by mass or more and 5% by mass or less, heat resistance is difficult. Excellent flammability.

It is preferable that the base material has a structure in which precipitates are dispersed in the mother phase and part of the precipitates are exposed from the mother phase so that irregularities are formed on the surface of the chemical film to be described later. The precipitate has an average particle size of 0.02 μm or more and 5 μm or less, and is present in an area of 2 area% or more and 15 area% or less when the cross section of the substrate is 100 area%. The precipitate is typically an intermetallic compound containing Mg or Al, and more specifically, a precipitate composed of Mg ₁₇ Al ₁₂ (not limited to Mg ₁₇ Al ₁₂ ). This precipitate has an average particle size of 0.2 μm or more and a content of 5 area% or more, so that the precipitate is sufficiently present in the base material to form sufficient irregularities on the surface of the chemical film. can do. In addition, the precipitate has an average particle size of 5 μm or less and a content of 15 area% or less, so that there is no excess precipitate in the base material or no coarse precipitate is present, and the film is formed. Appropriate irregularities can be formed on the surface.

  The shape of the substrate is not particularly limited as long as it is appropriately selected according to the use of the magnesium alloy member. Further, the thickness of the substrate is not particularly limited.

(Chemical film formation)
Chemical film formation is a state in which a part of the deposit of the base material is exposed from the film surface, and irregularities are formed on the surface. Due to this unevenness, the surface roughness of chemical conversion film is 10 μm or more in Rz (maximum height: distance from the lowest position to the highest position). The surface roughness Rz can be measured using a shape measuring laser microscope (manufactured by KEYENCE). The surface roughness measurement region may be a bonding region between the chemical film formation and the resin molded body or the vicinity thereof, for example, a region within a range of 2 mm from the edge of the bonding region. If the surface roughness Rz is 10 μm or more, the resin of the resin molded body, which will be described later, can be entangled with relatively large uneven portions, and both can be firmly bonded. A more preferable surface roughness Rz is 11 μm or more.

  The surface area ratio of chemical film formation is 2 or more. This surface area ratio is a value obtained by dividing the surface area of the three-dimensional shape by the unevenness of the chemical film formation by the area of the two-dimensional shape. The surface area of the three-dimensional shape can be measured using a shape measuring laser microscope (manufactured by KEYENCE). The measurement area of the surface area ratio may be a bonding area between the chemical film formation and the resin molded body or the vicinity thereof, for example, an area within a range of 2 mm from the edge of the bonding area. If the surface area ratio is 2 or more, it is possible to secure a sufficient bonding area between the chemical film formation and the resin molded body and firmly bond both. A more preferable surface area ratio is 2.1 or more.

  Chemical film formation is formed by chemical conversion treatment. As the treatment liquid for chemical conversion treatment, those specified in JIS H 8651 (2011) and other commercially available ones can be used. For the chemical conversion treatment solution, it is preferable from the viewpoint of environmental conservation to use a non-chromium treatment solution such as manganese phosphate / calcium solution or calcium phosphate solution.

  In forming a chemical film on the substrate surface, it is preferable to perform etching or the like as a pretreatment. When the chemical conversion treatment is performed after the pretreatment, a plurality of precipitates are interposed during the chemical film formation depending on the etching conditions. The interposition of precipitates during chemical film formation is the one embedded during chemical film formation, the part embedded in chemical film formation and the other part exposed to the outside, the part embedded in chemical film formation and the other part Embedded in the base material. Among these, a part of the precipitate exposed from the chemical film contributes to the unevenness of the chemical film surface.

  The thickness of the chemical conversion film is preferably 1 μm or less. This film thickness can be measured by taking a cross section by cutting in the film thickness direction of the chemical film formation and observing the cross section by SEM. At this time, several points where no precipitate is present are selected and the thickness is measured, and the average value is taken as the film thickness. The number of measurement points is, for example, 3 points. When the film thickness is 1 μm or less, the surface shape of the chemical film formation can be a surface state that accurately reflects the surface shape of the substrate. A more preferable film thickness is 0.2 μm or more and 0.8 μm or less.

(Resin molding)
The shape of the resin molded body may be appropriately selected according to the use of the magnesium alloy member, and is not particularly limited. The resin molded body is used, for example, as a reinforcing boss or rib. When used as a boss, for example, a cylindrical resin molded body is erected on the chemical film. This boss forms a female screw on its inner peripheral surface, and the male screw is screwed onto the female screw. When used as a rib, for example, a plate material orthogonal to the base material is erected in the chemical film formation.

  The material of the resin molded body may be appropriately selected according to the use of the magnesium alloy member in consideration of the hardness, corrosion resistance, durability, and heat resistance of the material, and is not particularly limited. For example, a thermoplastic resin or a thermosetting resin, and specific examples include polyphenylene sulfide resin, polybutylene terephthalate resin, and epoxy resin.

  The resin molded body is bonded to at least a part of the chemical film formation surface, and is usually bonded to a part of the chemical film formation surface, but may be bonded to the entire surface.

[Manufacturing method of magnesium alloy member]
This invention magnesium alloy member can be manufactured with the manufacturing method of a magnesium alloy member provided with each following processes, when a base material is a plate-shaped material.
Preparation step: A step of preparing a cast plate made of a magnesium alloy containing more than 7.5% by mass of Al and manufactured by a continuous casting method.
Solution treatment step: A step of producing a solid solution plate by subjecting the cast plate to a solution treatment at a temperature of 350 ° C. or higher.
Rolling step: A step of producing a rolled plate by subjecting the solid solution plate to warm rolling.
Polishing step: A step of polishing the rolled plate to produce a polished plate (base material).
Pretreatment step: a step of subjecting the substrate to an etching treatment to expose at least a part of precipitates present in the substrate on the surface of the polishing plate.
Chemical conversion treatment step: a step of subjecting the pretreated plate to chemical conversion treatment to form a chemical film on the surface.
Resin molded body joining step: A step of directly joining the resin molded body to the chemical film.

  Furthermore, the said manufacturing method can be equipped with the correction process which corrects the said rolled sheet. Further, the manufacturing method includes a plastic working step of performing plastic working such as press working on the rolled plate, the straightened plate obtained by the straightening step, the polishing plate (base material), and the base material on which the chemical film is formed. Can be provided.

  In manufacturing the magnesium alloy member of the present invention, as described above, Al is sufficiently dissolved in the magnesium alloy by performing the solution treatment. And in the manufacturing process after the solution treatment, by setting the time for holding the material composed of the magnesium alloy in a temperature range (150 ° C. to 300 ° C.) where the precipitate is likely to be precipitated within a specific range, While precipitating, the amount can be within a specific range. In addition, by controlling the time for holding in the specific temperature range, excessive growth of the precipitate can be suppressed, and a structure in which fine precipitates are dispersed can be obtained.

Hereinafter, each process is demonstrated in detail.
(Preparation process)
As the cast plate, it is preferable to use a cast plate produced by a continuous casting method such as a twin-roll method, in particular, a casting method described in WO / 2006/003899. Since the continuous casting method can be rapidly solidified, it can reduce oxides, segregation, and the like, and can suppress the formation of coarse crystal precipitates exceeding 10 μm that can be the starting point of cracking. Therefore, a cast plate having excellent rolling properties can be obtained. The size of the cast plate is not particularly limited, but segregation is likely to occur if it is too thick, and therefore it is preferably 10 mm or less, particularly 5 mm or less. In particular, when producing a cast coil material obtained by winding a long cast plate, if the portion immediately before winding in the material is wound in a state heated to 150 ° C. or more, cracks and the like may occur even when the winding diameter is small. It can be wound up without occurring. When the winding diameter is large, the winding may be performed cold.

(Solution process)
The cast plate is subjected to a solution treatment so that the composition is homogenized and a solid solution plate in which an element such as Al is dissolved is manufactured. The solution treatment is preferably performed at a holding temperature of 350 ° C. or higher, particularly a holding temperature: 380 ° C. to 420 ° C., a holding time: 60 minutes to 2400 minutes (1 hour to 40 hours). Further, it is preferable that the holding time is longer as the Al content is higher. Furthermore, in the cooling process from the above holding time, if forced cooling such as water cooling or blast is used to increase the cooling rate (for example, 50 ° C./min or more), it is possible to suppress the precipitation of coarse precipitates. This is preferable.

(Rolling process)
In rolling the solid solution plate, plastic workability can be improved by heating the material (solid solution plate or plate in the middle of rolling). Therefore, warm rolling is performed for at least one pass. By rolling a plurality of times (multi-pass), a desired plate thickness can be obtained, and the average crystal grain size of the material can be reduced (for example, 10 μm or less), and plastic workability such as rolling and pressing can be improved. The rolling may be performed by heating a known condition, for example, not only the material but also the rolling roll. Further, in rolling with a small degree of work (rolling ratio) such as finish rolling, the rolling may be performed cold. Furthermore, when the above-described rolling is appropriately used with a lubricant, the frictional resistance during rolling can be reduced, and the material can be prevented from being seized and rolled.

  When performing multi-pass rolling, intermediate heat treatment may be performed between passes. By removing and reducing distortion, residual stress, texture, etc. introduced into the material to be processed by plastic working (mainly rolling) up to intermediate heat treatment, it is possible to prevent inadvertent cracking, distortion and deformation in subsequent rolling. Rolling can be performed more smoothly.

(Correction process)
It is preferable to perform warm correction on the rolled plate because of excellent plastic workability such as press working. The correction may be performed by using a roll leveler or the like in which a plurality of rolls are arranged in a staggered manner, and heating the rolled plate to 100 to 300 ° C., preferably 150 to 280 ° C. When plastic processing such as press processing is performed on the straightened plate that has been subjected to such warm correction, dynamic recrystallization occurs during the plastic processing, and the plastic workability is excellent. In addition, the said holding time in a correction process can be made very short by performing correction processing with respect to the raw material which became comparatively thin by rolling. For example, depending on the thickness of the material, the holding time can be set to several minutes, and further within one minute.

(Plastic processing process)
When plastic processing such as pressing is performed on the rolled plate, the correction plate obtained by the correction process, the polishing plate (base material), or the base material on which the chemical film is formed, in a temperature range of 200 ° C to 300 ° C. This is preferable because the plastic workability can be improved. The time for holding the plate material at 200 to 300 ° C. during the plastic working is very short, for example, it may be within 60 seconds depending on the press working, and defects such as the coarsening of the precipitates as described above are substantial. It is thought that it does not occur.

  When the plastic working is performed prior to the resin molded body joining step, it is preferable to prevent the resin molded body from being damaged during the plastic working, but it may be performed after the resin molded body joining step. The plastic processed product formed by this plastic working is, for example, a cross-sectional box-shaped box or a] -shaped bent body having a top plate portion (bottom surface portion) and a side wall portion standing from the periphery of the top plate portion. Etc.

(Polishing process)
A polishing plate is produced by subjecting the rolled plate or the straightened plate subjected to the correction to a polishing treatment to smooth the surface of the rolled plate. The polishing process is typically wet belt type polishing. The smaller the abrasive count of the abrasive (abrasive grains), the rougher the surface of the substrate.

(Pretreatment process)
In performing chemical conversion treatment on the polishing plate (base material), at least etching treatment is applied as a pretreatment to the base material in order to expose precipitates such as intermetallic compounds in the base material. A known processing liquid can be used as the processing liquid for the etching process. The etching processing time is preferably set to 30 seconds or longer, more preferably 60 seconds or longer. By setting the treatment time to 60 s or longer, the amount of deposits exposed in the substrate can be increased. Therefore, the surface area of the substrate surface can be increased, contributing to an increase in surface roughness.

  In the pretreatment step, it is more preferable to perform not only the etching process but also degreasing, etching, desmutting and surface adjustment. By performing such pretreatment, it is possible to remove the lubricant used at the time of rolling or plastic working, etc., and the chemical film can be formed with high accuracy, and the base material and chemical film are closely adhered. Can be made.

(Chemical conversion treatment process)
A chemical conversion treatment is performed on the pretreated plate to form a chemical film on the surface. The preferable temperature and time of the chemical conversion treatment are 33 ° C. to 37 ° C. and 40 s to 90 s.

(Resin molded body joining process)
The resin molded body is directly bonded onto the chemical film that has been subjected to the chemical conversion treatment. As a method of joining the resin molded body onto the chemical film, for example, the base material on which the chemical film is formed is placed in a mold, an uncured resin is injected into the mold, and the resin is solidified. This includes injection molding in which the chemical film and the resin molded body are joined and integrated. Injection molding makes it easy to give flexibility to the shape of the resin molded body, and is preferable from the viewpoint of mass productivity.

<Test example>
According to the manufacturing method of the above-described embodiment, a magnesium alloy member including a resin molded body directly bonded onto the chemical film formed on the surface of the substrate is manufactured, and the bonding strength between the chemical film and the resin molded body is manufactured. And the joining degree was investigated. Specific test conditions are shown below.

[Example 1]
The magnesium alloy member of Example 1 is manufactured by a process of casting → solution treatment → rolling (warm) → polishing → chemical conversion treatment → resin molding joining.

First, a cast plate (thickness 4 mm) made of a magnesium alloy having a composition equivalent to AZ91 alloy (Mg-9.0% Al-1.0% Zn (all mass%)) and obtained by a twin roll continuous casting method is prepared. The obtained cast plate was subjected to a solution treatment at 400 ° C. for 8 hours. The solid solution plate subjected to solution treatment was rolled a plurality of times under the following rolling conditions until the thickness became 0.6 mm.
(Rolling conditions)
Degree of processing (rolling rate): 5% / pass to 40% / pass Heating temperature of plate: 250 ° C to 280 ° C
Roll temperature: 100 ℃ ~ 250 ℃

  Here, in each pass of the rolling process, by adjusting the heating time and rolling speed (roll peripheral speed) of the material to be rolled, the total time for which the material is maintained in the temperature range of 270 ° C. to 300 ° C. 4 hours.

  The obtained rolled plate was subjected to wet belt type polishing using a # 400 polishing belt, and the surface of the rolled plate was smoothed by polishing to prepare a polished plate (base material). This substrate is arbitrarily cut in the plate thickness direction to obtain a cross section. When the cross section is observed with a scanning electron microscope (SEM), the average particle size is 0.02 μm or more and 5 μm or less, and the cross section of the substrate is 100% by area. In this case, precipitates existed in the range of 2 area% or more and 15 area% or less.

The obtained polishing plate was pretreated by the procedure of etching → desmutting, and the treated plate was subjected to chemical conversion to form a chemical film.
Etching: 2.8% phosphoric acid solution under stirring, 60 ° C, 60 seconds Desmutting: 45% sodium hydroxide solution under stirring, 60 ° C, 600 seconds Chemical conversion treatment: Calcium phosphate-based chemical treatment solution, treatment temperature 35 ° C, immersion time 60 seconds

  FIG. 1 (A) shows the surface state of the chemical film formation on the obtained substrate surface. Fig. 1 (A) shows the surface of the chemical film formed with a scanning electron microscope: SEM (200,000 times), and light gray (white) small particles are precipitates, and the precipitates are uniformly dispersed. You can see that

  The film thickness of the chemical film formation was 0.2 μm. The film thickness was measured by observing a cross section with an SEM by cutting the cross section in the film thickness direction of the chemical film formation. At this time, three points where no precipitate was present were selected, the thickness was measured, and the average value was obtained.

  The surface roughness and surface area ratio of the chemical film formation on the obtained substrate surface were measured as follows. The results are shown in Table 1.

[Surface roughness Rz]
The surface roughness Rz was measured by using a shape measurement laser microscope (manufactured by KEYENCE) at a planned bonding position with a resin molded body to be described later on the chemical film forming surface. As a result, the surface roughness Rz was 11.6 μm.

[Surface area ratio]
The surface area ratio is measured by measuring the surface area of the three-dimensional shape of the measurement area at the location where the resin molded body, which will be described later, is to be bonded on the chemical film formation surface, using a shape measurement laser microscope (manufactured by KEYENCE). It was obtained by dividing by the two-dimensional area of the region. As a result, the surface area ratio was 2.1.

Next, the resin molding was directly joined to the obtained chemical film on the substrate surface by injection molding. The shape of the resin formed body will be described in the following measurement of bonding strength and bonding degree.
(Resin molded body joining conditions)
Resin: PPS: Polyphenylene sulfide (Elastomer modified type, 40% GF (glass fiber) blended)
Resin temperature: 280 ℃
Mold temperature: 160 ℃
Injection pressure: 120MPa

[Joint strength]
The bonding strength of the resin molded body bonded to the chemical film formation was measured. The results are shown in Table 1. Here, as shown in FIG. 2 (A), two cylindrical resin molded bodies 10 are prepared, and the end surface of the resin molded body 10 and the chemical film 3 on the substrate 2 are joined together to form a magnesium alloy member. It was set to 1. The total bonding area between the chemical conversion film 3 and the two resin molded bodies 10 was 52 mm ² . With the base material 2 fixed, the two resin molded bodies 10 were pulled six times at a tensile speed of 1 mm / min in the direction of the arrow, and the average value was defined as the bonding strength of the resin molded body 10 to the chemical film 3. As a result, the bonding strength was 0.82 MPa.

[Degree of joining]
The degree of bonding of the resin molded body bonded to the chemical film formation was measured. The results are shown in Table 1. Here, as shown in FIG. 2 (B), two] resin molded bodies 11 are prepared, and the end face 2 surface of each resin molded body 11 and the chemical film 3 on the substrate 2 are joined, A magnesium alloy member 1 was obtained. ] -Shaped resin molded body 11 is formed by integrally molding, for example, a top plate portion and leg portions erected from both ends of the top plate portion. The total bonding area between the chemical conversion film 3 and the legs was 30 mm ² . With the base material 2 fixed, it was necessary to press the resin molding body 11 in the direction of the arrow perpendicular to the length direction of the resin molding body 11 and parallel to the base material 2, and to push down the molding body 11. The maximum load was the degree of joining. The press location of each resin molded body 11 is a position having a height of 8.5 mm at the center in the longitudinal direction of the top plate portion, and is a position of 77% with respect to the height of the entire resin molded body 11. As a result, it was 18.8N.

[Comparative Example 1]
Comparative Example 1 differs from Example 1 in that after the rolling step, the obtained rolled plate was heated in nitrogen at 400 ° C. for 8 hours to re-dissolve the precipitate. Other casting processes, solution treatment processes, rolling processes, pretreatment processes, chemical conversion treatment processes, and resin molded body joining processes are the same as those in the first embodiment. Further, the method for measuring the surface roughness Rz and the surface area ratio and the method for measuring the bonding strength and the degree of bonding are the same as those in Example 1.

  FIG. 1B shows the surface state of the chemical film formation on the surface of the obtained substrate. In FIG. 1B, it can be seen that the light gray (white) small granular material is a precipitate, and the interval between adjacent precipitates is larger than that in Example 1. At this time, the surface roughness Rz was 20.3 μm, the surface area ratio was 1.6, the bonding strength was 0.56 MPa, and the bonding degree was 13.7 N (Table 1).

[Comparative Example 2]
In Comparative Example 2, in the rolling step, the heating temperature range of the material is maintained in a temperature range of 230 ° C. to 260 ° C., and the point that the # 600 polishing belt is used in the polishing step is the same as in Example 1. Different. Other casting steps, solution treatment steps, pretreatment steps, chemical conversion treatment steps, and resin molded body joining steps are the same as those in the first embodiment. Further, the method for measuring the surface roughness Rz and the surface area ratio and the method for measuring the bonding strength and the degree of bonding are the same as those in Example 1.

  FIG. 1C shows the surface state of the chemical film formation on the surface of the obtained substrate. In FIG. 1C, it can be seen that the light gray (white) small granular material is a precipitate, and the size of the precipitate is smaller than that of Example 1. At this time, the surface roughness Rz was 8.9 μm, the surface area ratio was 2.1, the bonding strength was 0.67 MPa, and the bonding degree was 8.7 N (Table 1).

[Comparative Example 3]
Comparative Example 3 is different from Example 1 in that anodization was performed instead of chemical conversion. Other casting processes, solution treatment processes, rolling processes, pretreatment processes, and resin molded body joining processes are the same as those in the first embodiment. Further, the method for measuring the surface roughness Rz and the surface area ratio and the method for measuring the bonding strength and the degree of bonding are the same as those in Example 1.

  The surface state of the anodic oxide film on the surface of the obtained substrate is shown in FIG. 1 (D) (SEM (300,000 times)). In FIG. 1 (D), it can be seen that black holes are present. At this time, the surface roughness Rz was 1.2 μm, and the surface area ratio was 1.5. In Comparative Example 3, the resin molded body could not be bonded onto the film formed by the solution treatment. Therefore, the bonding strength was 0.00 MPa and the bonding degree was 0.0 N (Table 1).

  As shown in Table 1, when the surface roughness Rz is 10 μm or more and the surface area ratio is 2 or more, the bonding strength and the degree of bonding are large, and the chemical film can be firmly bonded to the resin molded body. I understand.

<Embodiment 2>
The unevenness affecting the surface roughness Rz and the surface area ratio of the chemical film formation was caused by precipitates formed in the base material in the first embodiment, but in the second embodiment, the unevenness in the base material was inorganic. This is due to the addition of the material and the inorganic material exposed on the surface of the chemical film formation. The second embodiment is different from the first embodiment in the composition of the substrate. The chemical film formation and the resin molded body are the same as those in the first embodiment. Hereinafter, the substrate will be described in detail.

(Base material)
The base material is an inorganic material added to a magnesium alloy. Inorganic materials are typically ceramics such as SiC. Other examples include Al ₂ O ₃ . The inorganic material preferably has a volume distribution center particle size D50 of 80 nm or more. When the volume distribution center particle diameter D50 is 80 nm or more, the surface roughness on the substrate surface can be increased.

  The inorganic material is in a substantially uniformly dispersed state in the base material, and the content of the inorganic material in the base material is 10% by volume or more when the base material is 100% by volume. The greater the content of the inorganic material in the base material, the easier it is to expose the inorganic material on the surface, and the easier it is to roughen the surface.

  The manufacturing method of the magnesium alloy member which formed the chemical film on the said base material, and joined the resin molding to the chemical film formed in the preparatory process, and prepares the cast board which continuously cast the magnesium alloy which mixed the inorganic material The difference from Embodiment 1 is that the solution treatment step is not performed. Other steps after the rolling step are the same as in the first embodiment. The inorganic material is mixed into the molten magnesium alloy.

  The magnesium alloy member of the second embodiment can sufficiently secure the bonding area between the chemical film formation and the resin molded body by the unevenness of the inorganic material, and can firmly bond both.

<Embodiment 3>
In addition, in the magnesium alloy member according to the first embodiment and the second embodiment, an embodiment having a press working part in which at least a part of the base material is subjected to press working will be described with reference to FIG. The point that the base material is subjected to press working is different from the first embodiment, and other configurations are the same as those of the first embodiment.

  The press working part can be manufactured, for example, by subjecting a polishing plate obtained by the method for manufacturing a magnesium alloy member of Embodiment 1 as a raw material to press working. Here, it is a form in which a resin molded body is joined as reinforcing ribs in the vicinity of the four corners of the bottom surface of the casing of the notebook computer. The base material 2 having the press-worked portion 20 obtained by the press working is subjected to a chemical conversion treatment to form a chemical film 3, and the resin molded body 12 is joined to the chemical film 3 to thereby form the magnesium of the present invention. Alloy member 1 can be obtained. Examples of the press working part include a cross section having a top plate part (bottom surface part) and a side wall part erected from the periphery of the top plate part, a box-like bent body, and the like. The size is not particularly limited.

  The above-described embodiment can be appropriately changed without departing from the gist of the present invention, and is not limited to the above-described configuration. For example, the composition of the magnesium alloy (particularly the Al content), the thickness and shape of the magnesium alloy material, the constituent materials for the chemical film formation, and the like can be changed as appropriate.

  The magnesium alloy member of the present invention can be suitably used as a constituent material of various members such as a casing of a portable electric / electronic device such as a mobile phone or a notebook personal computer or an automobile part.

1 Magnesium alloy parts
2 Substrate 3 Film formation
10,11,12 Molded resin
20 Press working section

Claims (5)

A base material made of a magnesium alloy containing more than 7.5% by mass of Al,
A chemical film formed on the substrate surface;
A resin molded body directly bonded to the chemical film,
A magnesium alloy member wherein the surface roughness of the chemical film is 10 μm or more in Rz, and the surface area ratio obtained by dividing the three-dimensional surface area due to the irregularities of the chemical film by the two-dimensional area is 2 or more.   2. The magnesium alloy member according to claim 1, wherein the chemical film formation is made of a phosphate compound.   3. The magnesium alloy member according to claim 1, wherein the chemical film formation has a film thickness of 1 μm or less.   The magnesium alloy member according to any one of claims 1 to 3, wherein the magnesium alloy contains Al in a range of 8.3 mass% to 9.5 mass% and Zn in a range of 0.5 mass% to 1.5 mass%.   The magnesium alloy member according to any one of claims 1 to 4, further comprising a press-worked portion in which at least a part of the base material is press-worked.