JP6035672B2 - Magnesium alloy parts - Google Patents

Description

  The present invention relates to a magnesium alloy member in which a plurality of magnesium alloy materials are integrated. In particular, the present invention relates to a magnesium alloy member having excellent bonding strength between these magnesium alloy materials.

  In recent years, a magnesium (hereinafter referred to as Mg) alloy has been used as a material for mobile phone and notebook computer housings and automobile parts. As a member made of the Mg alloy, for example, there is one shown in Patent Document 1.

  Patent Document 1 discloses a Mg alloy member obtained by joining a reinforcing material (Mg alloy material) made of a metal (for example, Mg alloy) to a plate material (Mg alloy material) made of Mg alloy. The plate material and the reinforcing material are joined by spot welding.

JP 2010-157598 A

  Expanded members such as a rolled material made of Mg alloy have a limit in the shape that can be formed by plastic working. Therefore, if a plurality of Mg alloy materials are joined to each other as described above, a complex-shaped Mg alloy member that cannot be formed even if the stretched member is plastically processed can be obtained. However, further improvement in bonding strength between a plurality of Mg alloy materials is desired. Mg alloy is easily oxidized and a natural oxide film is easily formed. For this reason, when a plurality of Mg alloy materials are joined together by spot welding as described above, there is a possibility that the joint strength between the Mg alloy materials becomes insufficient due to local joining at the contact surface between the Mg alloy materials. Further, when the Mg alloy materials have different thicknesses, they may not be welded and joined.

  The present invention has been made in view of the above circumstances, and one of its purposes is an Mg alloy member formed by integrating a plurality of Mg alloy materials, and an Mg alloy excellent in bonding strength between these Mg alloy materials. It is to provide a member.

  The Mg alloy member of the present invention is formed by integrating a plurality of Mg alloy materials, and includes a stretch member, a cast member, and a joining region between the stretch member and the cast member. The extension member is made of an Mg alloy containing Mg as a main component and containing at least aluminum (hereinafter, Al) as an additive element. The cast member is made of an Mg alloy having the same kind of additive element as the Mg alloy constituting the spread member and having substantially the same Al content. The joining region has a welding region where the spreading member and the casting member are welded. And the area ratio of the welding area | region with respect to a joining area | region is 60% or more.

  The Mg alloy member of the present invention is excellent in the bonding strength between the stretched member and the cast member constituting it. This is because the extension member and the cast member are made of the above-described Mg alloy, and 60% or more of their joining regions are welded.

  In addition, since the extension member and the cast member are made of the above-described Mg alloy, electrolytic corrosion is unlikely to occur in the joining region, particularly in the welding region, in a corrosive environment.

  And since these extending members and cast members are welded, it is possible to form complex shapes that cannot be formed even by plastic working of the expanding members, and it is possible to obtain Mg alloy members having various shapes.

  As one form of the Mg alloy member of the present invention, the joining region may include a contact region around the welding region where the extension member and the cast member are not welded to contact each other. The area ratio of the contact region to the bonding region is less than 40%.

  Even if the area ratio includes the contact region in the above range, the weld region is sufficiently large, and thus the bonding strength between the stretch member and the cast member is sufficiently excellent.

  As one form of Mg alloy member of this invention, it is mentioned that content of Al in a extending member and a cast member is 5.5 to 10.5 mass%.

  According to said structure, since there is much content of Al, while being excellent in the corrosion resistance of Mg alloy member itself, it is excellent also in a mechanical characteristic.

  As an embodiment of the Mg alloy member of the present invention, the expanded member and the cast member include Al in the range of 8.3 mass% to 9.5 mass%, and zinc (Zn) in the range of 0.5 mass% to 1.5 mass%. The following is included.

  According to said structure, while being excellent in corrosion resistance, it is excellent also in a mechanical characteristic.

  One embodiment of the Mg alloy member of the present invention is that the stretched member is a plate material.

  By using the extending member as a plate material, the cast member can be easily formed integrally.

  As one form of Mg alloy member of this invention, it is mentioned that the said casting member is at least one of a rib, a boss | hub, and a pin.

  By using a rib, boss, or pin as the cast member, an Mg alloy member having a shape that cannot be formed or difficult to form even if the stretched member is plastically processed can be obtained.

  The Mg alloy member of the present invention is excellent in the bonding strength between the stretched member and the cast member constituting it.

The Mg alloy member which concerns on embodiment is shown, (A) is a schematic perspective view, (B) is (B)-(B) sectional drawing in (A).

  Embodiments of the present invention will be described below with reference to the drawings. The same reference numerals in the figure indicate the same names.

《Mg alloy member》
With reference to FIG. 1, the Mg alloy member 100 of this invention is demonstrated. The Mg alloy member 100 of the present invention is formed by integrating a plurality of Mg alloy materials, and includes a spread member 1, a cast member 2, and a weld region 31 in which the stretch member 1 and the cast member 2 are welded. A joining region 3 having The feature of this Mg alloy member 100 is that each Mg alloy constituting the extension member 1 and the cast member 2 has the same kind of additive element, contains at least Al as the additive element, and is mutually Al. The content ratio of the welding region 31 is substantially the same, and the area ratio of the welding region 31 to the bonding region 3 is large. In this example, the joining region 3 further has a contact region 32 where the expanding member 1 and the cast member 2 are not welded. Hereinafter, each configuration will be described in detail.

[Expanded members]
The extending member 1 is an Mg alloy material to which a casting member 2 described later is integrally welded. Specifically, the rolling material which rolled the casting material produced by casting, such as a twin roll, die-casting, and a thixo mold, is mentioned. In addition, a processed material in which the rolled member is further subjected to heat treatment, leveler processing, polishing processing, or the like, or a plastic processed material in which the rolled material or processed material is further subjected to plastic processing may be used. The spreading member 1 may be subjected to a solution treatment before the rolling, or may be subjected to a heat treatment for removing strain generated during plastic working.

  The shape of the spreading member 1 can be appropriately selected depending on the subsequent molded product. For example, the extending member 1 may be a plate-like body, or an L-shaped body, [shaped body, cylindrical body, or box-shaped body, etc., which is appropriately subjected to plastic processing. Also good. Here, as shown in FIG. 1 (A), the expanding member 1 is a [shaped body 10 formed by bending (plastic working) into a letter shape. The side portions of adjacent projecting pieces can be joined by welding or the like.

  It should be noted that a portion of the surface of the spreading member 1 other than a portion where the cast member 2 is integrally formed may be provided with a protective film or a coating film. By doing so, it is possible to prevent the extension member 1 from being oxidized and to improve the appearance.

(Casting member)
The casting member 2 is an Mg alloy material that is integrally welded to the spreading member 1. For example, it can be produced by die casting or thixo mold, and is integrally welded to the expanding member 1 together with the production.

  The shape of the cast member 2 can be appropriately determined according to the role (function) in the subsequent molded product. As the function of the cast member 2, for example, reinforcement of the molded Mg alloy member 100, and other members are used for the Mg alloy member 100, or for assembling for combining the Mg alloy member 100 with other members. It is done. Specifically, a rib, a boss, a pin, etc. are mentioned.

  In the case where the cast member 2 is a rib, for example, it may be a long body having various shapes such as an L shape, a T shape, or an I shape. Similarly, when it is set as a boss | hub, it is mentioned as cylindrical bodies, such as cylindrical shape and a rectangular tube shape, for example. In that case, a female screw may be formed on the inner peripheral surface of the cylindrical body so that the male screw can be screwed into the female screw. Moreover, when setting it as a pin, it is mentioned as rod-shaped bodies, such as column shape, prismatic shape, or frustum shape, for example. These can be molded by appropriately selecting the shape of the mold used in the production process (described later). Here, as shown in FIG. 1, the casting member 2 is an L-shaped long body (rib) 20, a cylindrical tubular body (boss) 21, or a columnar rod body (pin) 22. .

  The surface of the cast member 2 may also be provided with a protective film or a paint film, similar to the spreading member 1.

[Constituent materials for wrought and cast members]
Each Mg alloy that constitutes the extending member 1 and the cast member 2 is an Mg—Al-based alloy that contains at least Al as an additive element and the balance is composed of Mg and inevitable impurities.

  The Al content is preferably 3% by mass or more, more preferably 5.5% by mass, and even more preferably 7.3% by mass or more. The higher the Al content, the better the hot water flow during production and the better the castability. Further, the manufactured member tends to have excellent corrosion resistance and mechanical properties such as strength and plastic deformation resistance. However, if the Al content exceeds 12% by mass, the plastic workability is lowered, so the upper limit is 12% by mass. The Al content is preferably 11% by mass or less, more preferably 10.5% by mass or less, and particularly preferably 8.3% by mass to 9.5% by mass.

  Mg alloys include those having various compositions containing various additive elements in addition to Al. In that case, it is preferable that the extension member 1 and the cast member 2 have the same kind of additive element other than Al, and moreover, the content of Al is the largest among the additive elements contained in the Mg alloy. Specific additive elements are selected from Zn, Mn, Si, Be, Ca, Sr, Y, Cu, Ag, Sn, Li, Zr, Ce, Ni, Au, and rare earth elements (excluding Y and Ce). 1 type or more elements. When such elements are included, the total content is 0.01% by mass or more and 10% by mass or less, preferably 0.1% by mass or more and 5% by mass or less. Among these additive elements, at least one element selected from Si, Sn, Y, Ce, Ca, and rare earth elements (excluding Y and Ce) is in total 0.001% by mass or more, preferably in total 0.1 When it is contained in an amount of from 5% by mass to 5% by mass, it is excellent in heat resistance and flame retardancy. When the rare earth element is contained, the total content is preferably 0.1% by mass or more, and particularly when Y is contained, the content is preferably 0.5% by mass or more. Examples of the impurities include Fe.

  More specific compositions of Mg-Al alloys include, for example, AZ-based alloys (Mg-Al-Zn-based alloys, Zn: 0.2 mass% to 1.5 mass%) in ASTM standards, AM-based alloys (Mg -Al-Mn alloy, Mn: 0.05 mass% to 0.5 mass%), AS alloy (Mg-Al-Si alloy, Si: 0.3 mass% to 4.0 mass%), Mg -Al-RE (rare earth element) based alloy, AX based alloy (Mg-Al-Ca based alloy, Ca: 0.2 mass% to 6.0 mass%), AZX based alloy (Mg-Al-Zn-Ca based) Alloy, Zn: 0.2 mass% to 1.5 mass%, Ca: 0.1 mass% to 4.0 mass%), AJ alloy (Mg—Al—Sr alloy, Sr: 0.2 mass%) -7.0 mass%) and the like.

  The Mg alloy of the extending member 1 and the cast member 2 has the same type of additive element and substantially the same Al content. Here, the content of Al is substantially the same means that the Al content is within the specified range of the alloy type specified by the ASTM standard. On the other hand, the content of the additive element is preferably approximated. The approximate content of the additive element means that it is within a range up to a value 2 mass% higher than the upper limit value of the additive element defined range in the alloy species containing Al defined by the ASTM standard. . For example, in the case of an AZ-based alloy according to the ASTM standard, since the specified value of Zn is 0.2% by mass to 1.5% by mass as described above, the approximate range of Zn is 0.2% by mass to 3.5% by mass. It is. In particular, it is preferable that the content of the additive element is substantially the same. The fact that the content of the additive element is substantially the same means that it is within the specified range of the additive element in the alloy type containing Al specified by the above-mentioned ASTM standard. That is, the Mg alloy species of the extension member 1 and the cast member 2 are AZ61 (Al: 5.5 mass% to 7.2 mass%, Zn: 0.4 mass% to 1.5 mass%), AZ91 ( Al: 8.3 mass% to 9.5 mass%, Zn: 0.5 mass% to 1.5 mass%), AM60 (Al: 5.5 mass% to 6.0 mass%, Mn: 0.00 mass%). 05 mass% to 0.5 mass%) or AZX911 (Al: 8.3 mass% to 9.5 mass%, Zn: 0.5 mass% to 1.5 mass%, Ca: 0.1 mass%) To 1.5% by mass) or the like. If it does so, it will become difficult to produce an electric corrosion in the joining area | region 3 (especially welding area | region 31) with the extension member 1 in a corrosive environment, and the Mg alloy member 100 will not rust easily. In particular, it is preferable that both the extending member 1 and the cast member 2 are made of AZ91 alloy because of excellent corrosion resistance and mechanical properties.

(Joint area)
The joining region 3 is a place where the expanding member 1 and the casting member 2 are combined, and is formed together with the production of the casting member 2. Usually, this joining area | region 3 has the welding area | region 31 where the expansion member 1 and the casting member 2 were welded, and the contact area | region 32 where the expansion member 1 and the casting member 2 contact without being welded. Thus, although the joining area | region 3 also has the contact area | region 32 in addition to the welding area | region 31, depending on the casting conditions of the casting member 2, it can be anticipated that the whole joining area | region 3 is made into the welding area | region 31. FIG. In that case, it can be set as the Mg alloy member 100 which is further excellent by the joining strength of the extending member 1 and the casting member 2. FIG. Here, as shown in FIG. 1B, the bonding region 3 is [between the surface of the character-shaped body 10 and each of the long body 20, the cylindrical body 21, and the rod-shaped body 22.

  The formation region of the welding region 31 is at least the central portion of the bonding region 3. The area ratio of the welding region 31 is 60% or more with respect to the bonding region 3. Thus, since there are many welding area | regions 31, even if it has the contact area | region 32, it can be set as the Mg alloy member 100 which is excellent in the joining strength of the extending member 1 and the casting member 2 sufficiently. The welding region 31 is formed of the constituent materials of the extending member 1 and the cast member 2. Therefore, there is no interface between the extending member 1 and the cast member 2.

  On the other hand, the formation location of the contact region 32 is a portion around the welding region 31 and is on the peripheral side of the bonding region 3. The area ratio of the contact region 32 is less than 40% with respect to the bonding region 3. In the contact region 32, since the extension member 1 and the cast member 2 are not welded, an interface between the extension member 1 and the cast member 2 exists.

<< Method for Manufacturing Mg Alloy Member >>
The manufacturing method of the Mg alloy member is a method of integrally forming a plurality of Mg alloy materials, a stretch member preparing step for preparing the stretch member, and an integral forming step for integrally molding the stretch member and the cast member. With

[Stretched member preparation process]
In the stretched member preparation step, first, a rolled plate material is prepared as the stretched member. Specifically, a cast material made of an Mg alloy having the above-mentioned composition is prepared, and the cast material is rolled and manufactured, or a Mg alloy rolled material manufactured in the same manner is purchased in advance. . In the former case, it can be produced by a known method such as the production method described in WO2006 / 003899 or JP-A-2007-98470. The Mg alloy rolled material prepared here may be appropriately subjected to various processing such as leveler processing, polishing processing, and plastic processing as described above.

[Integral molding process]
In the integral molding process, first, the expanded member prepared in the expanded member preparing process is stored in a mold. Since the shape of the cast member after molding can be determined by this mold, the shape of the mold may be appropriately selected according to the desired shape. For example, it is possible to divide up and down, and when the expansion member is arranged on the lower mold and the upper mold is combined with the lower mold, the contour shape of the inner space is a desired shape, specifically L-shaped, cylindrical Alternatively, a divided mold having a cylindrical shape is prepared.

  Next, a molten metal of the same kind of Mg alloy as that of the above-mentioned extension member is filled into the mold. At this time, the oxygen concentration in the mold is preferably 5% by volume or less. If it does so, the oxidation of the molten alloy of Mg alloy and the surface of a extending member by the oxygen in air can be suppressed, and the fall of the joint strength of an extending member and a cast member can be suppressed in the Mg alloy member after shaping | molding. The filled molten metal is in direct contact with the spreading member, and at the contact point of the molten metal with the spreading member, the peripheral side portion is cooled and solidified by the mold, and the central portion surrounded by the peripheral side portion is the expansion member. Melt the surface. In that case, it is preferable to keep the temperature of the extending member housed in the mold at 300 ° C. or lower, and further 200 ° C. or lower. By keeping the temperature of the stretched member at 300 ° C. or lower, the crystal grain size of the stretched member can be prevented from becoming coarse, and the strength of the stretched member can be prevented from decreasing. In this state, when the molten metal is cooled and completely solidified, a cast member is formed, and a contact region that is not welded to the cast member at the peripheral portion of the stretch member, and a central region of the stretch member A welded region where the cast member and the cast member are welded is formed, and an Mg alloy member in which the stretch member and the cast member are integrally formed can be manufactured.

[Other processes]
As other steps, various surface treatments (pretreatment) may be applied to the stretched member before the integral molding step, or various surface treatments (posttreatment) may be applied to the Mg alloy member after the integral molding step. May be.

  Examples of the pretreatment include polishing and etching for removing an oxide film at least at a location where the cast member is formed on the surface of the stretch member. If it does so, the joint strength of an extension member and a cast member can be improved.

  As the post-treatment, for example, chemical conversion treatment or anodizing treatment for forming a protective film on the surface of the Mg alloy member, various coating treatments such as electrodeposition coating or spray coating for forming a coating film on the surface of the Mg alloy member, etc. Can be mentioned. If it does so, oxidation prevention of Mg alloy member and an external appearance can be made favorable. In this example, since the extension member and the cast member are made of the same kind of Mg alloy as described above, the extension member and the cast member are not separately post-processed, and the Mg alloy member can be post-processed at once. Processing is difficult.

<Effect>
The above-mentioned Mg alloy member is excellent in the bonding strength between the extending member and the cast member constituting it. This is because the extension member and the cast member are made of the same kind of Mg alloy, and 60% or more of these joining regions are welded with each other's constituent materials. In addition, since the extension member and the cast member are made of the same type of Mg alloy, the Mg alloy member is less likely to rust in a corrosive environment and less susceptible to electrolytic corrosion at the weld location.

  On the other hand, according to the manufacturing method of the above-mentioned Mg alloy member, it is possible to manufacture an Mg alloy member having excellent bonding strength between the stretched member and the cast member. In addition, the shape of the cast member can be selected as appropriate by selecting the shape of the mold, so that it is possible to easily form complex shapes that cannot be formed by plastic processing of the expanded member, and manufacture various shapes of Mg alloy members. it can.

《Test example》
As test examples, Mg alloy members (Examples: Samples 1 to 4 and Comparative Examples: Samples 21 to 23) in which a stretched member made of an Mg alloy and a cast member made of an Mg alloy are integrally formed are prepared. The joint strength test and the corrosion resistance test shown in FIG. First, a stretch member corresponding to the composition shown in Table 1 is prepared, and a cast member corresponding to the composition shown in the table is integrally formed on the surface of the stretch member, and Samples 1 to 4 and Samples 21 to 21 are formed. 23 was produced. Here, the shape of the extending member is a plate-like body, and the shape of the cast member is the same as that of the cylindrical tubular body 21 described with reference to FIG.

[Joint strength test]
Each sample is subjected to a bonding strength test. Specifically, a female screw is formed on the inner peripheral surface of the cylindrical body 21 of each sample, and after the male screw is screwed onto the female screw, rotation is applied with a torque wrench until the cylindrical body 21 is removed from the plate-like body. In this test, the bonding strength is excellent (体) when the torque when the cylindrical body 21 drops off from the plate-like body is 1.0 N · m or more, and when the joining strength is 0.5 N · m or more and less than 1.0 N · m. When it was good (◯) and less than 0.5 N · m, it was judged as bad (×). The results are shown in Table 1.

  Moreover, after the said joint strength test, the area ratio with respect to the joining area | region of the welding area | region of an extending member and a cast member was computed from the joining area | region trace with the cast member in an extending member. The results are also shown in Table 1.

[Corrosion resistance test]
Each sample is subjected to a salt spray test by a test method defined in “Salt spray test method JIS Z 2371 (2000)” as a corrosion resistance test. In this test, the corrosion resistance is excellent (）) when no corrosion is observed in the joint region between the expanded member and the cast member in each sample after the test, and good (○) when almost no corrosion is observed. When corrosion was seen, it was set as a defect (x). The results are shown in Table 1.

(Salt spray test conditions)
Salt water concentration: 5%
Test temperature: 35 ° C
Test time: 24h

"result"
Samples 1 to 4 are superior in bonding strength to samples 21 to 23. The reason why the samples 1 to 4 are superior in bonding strength to the sample 21 is considered to be because the welded region between the stretched member and the cast member in the samples 1 to 4 is as large as 60% or more. And although this sample 1-4 has a welding area | region smaller than the samples 22 and 23 whose welding area | region is 80% or more, it is excellent in joining strength. This is considered to be because the spreading members and cast members of Samples 1 to 4 are made of Mg alloys having the same type of additive element and substantially the same Al content.

  Samples 1 to 4 are excellent in corrosion resistance. This result is considered to be because the spreading members and cast members of Samples 1 to 4 are made of the same kind of additive element and are made of Mg alloys having substantially the same Al content. Therefore, it is possible to make it more difficult for electrolytic corrosion to occur in the joining region of both members, particularly in the welding region. In particular, Samples 3 and 4 were superior in corrosion resistance to Samples 1 and 2. This is presumably because Samples 3 and 4 have a higher Al content than Samples 1 and 2.

  From the above, the extension member and the cast member are made of Mg alloy having the same type of additive element and substantially the same Al content, and the weld region of both members is 60% or more. Was excellent in bonding strength and corrosion resistance, and in particular, it was found that the higher the Al content, the better the corrosion resistance.

  Note that the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention.

  The Mg alloy member of the present invention can be suitably used for a casing of a mobile phone or a notebook computer, a chassis or a stay in an industrial machine, an automobile, or the like.

DESCRIPTION OF SYMBOLS 100 Mg alloy member 1 Expanding member 10 [Shape-shaped body 2 Casting member 20 Long body (rib) 21 Cylindrical body (boss) 22 Bar-shaped body (pin)
3 Joining area 31 Welding area 32 Contact area

Claims (6)

A magnesium alloy member formed by integrating a plurality of magnesium alloy materials,
A spread member made of a magnesium alloy containing magnesium as a main component and containing at least aluminum as an additive element;
Casting made of a magnesium alloy having the same kind of additive element as that of the magnesium alloy constituting the extension member and having an aluminum content within the specified range of aluminum of the alloy type specified by the ASTM standard of the extension member Members,
Comprising a joining region between the extension member and the cast member;
The joining region has a welding region where the extension member and the casting member are welded,
The formation location of the welding region is at least a central portion of the bonding region,
The magnesium alloy member whose area ratio of the said welding area | region with respect to the said joining area | region is 60% or more.
However, a magnesium alloy member in which the joint structure between the extension member and the cast member is a spot welded portion is excluded. The joining region comprises a contact region around the welding region where the extension member and the cast member are in contact without being welded,
The magnesium alloy member according to claim 1, wherein an area ratio of a contact region to the bonding region is less than 40%. The magnesium alloy member according to claim 1 or 2, wherein a content of the aluminum in the stretch member and the cast member is 5.5% by mass or more and 10.5% by mass or less. The wrought member and casting members, aluminum 9.5 wt% 8.3 wt% or more or less, any zinc claim 1 containing 1.5 wt% or less than 0.5 wt% of claim 3 2. The magnesium alloy member according to item 1. The magnesium alloy member according to any one of claims 1 to 4, wherein the extension member is a plate material. The magnesium alloy member according to any one of claims 1 to 5, wherein the cast member is at least one of a rib, a boss, and a pin.

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