JPH06248402A - Production of member made of magnesium alloy - Google Patents

Abstract

PURPOSE:To produce a member improved in forgeability and furthermore excellent in mechanical properties by allowing magnesium compounds present in the structure of a forging blank made of a magnesium alloy into solid solution and thereafter executing forging. CONSTITUTION:A forging blank made of a magnesium alloy is subjected to forging and is subjected to heating treatment at 400 to 450 deg.C for about >=10hr to enter magnesium compounds present in the structure of the forging blank into solid solution. Next, it is subjected to warm forging at about 300 to 380 deg.C and is cooled to room temp., and deburring is executed. After that, it is subjected to aging treatment at about 162 to 210 deg.C for about 16hr and is air- cooled. Furthermore, it is subjected to machining and is thereafter subjected to rust preventing treatment to produce a member made of a magnesium alloy. In this way, the member improved in forgeability and excellent in mechanical properties can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnesium alloy member such as a wheel used as an automobile part or an upper arm of a suspension.

[0002]

2. Description of the Related Art Conventionally, as a method for manufacturing a magnesium alloy member for the purpose of significantly reducing the weight of parts, there is a forging method as shown in FIG. 7, for example. That is, in the first step 71, a magnesium alloy material (so-called blank)
Basting, Buster forging is performed in the second step 72, Blocker forging is performed in the third step 73, Finisher forging is performed in the fourth step 74, and Next step 5 is performed. Then, heat treatment such as T6 treatment is performed at 75, and the following sixth step 7
Machined to the final shape of the part in 6 and the next 7th step 77
This is a manufacturing method in which rust prevention treatment is applied. The forging steps 72, 73, and 74 are performed in several stages in this manner, because the magnesium alloy described above is a poor plastic working material, the forging is performed in several steps with a relatively small working rate.

However, in such a conventional method, since heating and cooling are repeated for each forging, the crystal grains become coarse, and there is a problem that the strength cannot be improved even if the forging is performed. . Further, there are problems that a large number of forging dies are required and that heat consumption energy is extremely large.

In order to solve such a problem, a casting / forging method as shown in FIG. 8 has been invented. That is, a magnesium alloy blank (forged blank) is manufactured by casting in the first step 81, the forged blank is cooled in the next second step 82, and the gate is trimmed as necessary, and the next step is performed. Finisher forging is performed in step 83 of No. 3, after this finisher forging is finished, solution treatment is performed in the following fourth step 84, and artificial aging treatment is performed in the following fifth step 85. Each of the above steps 84, 85
Is a casting forging method in which the final shape of the component is machined in the next sixth step 86 and the rust-proofing treatment is applied in the next seventh step 87 after the T6 treatment is completed.

According to this conventional method, it is possible to reduce the number of forging steps, thereby reducing the number of times heating and cooling are repeated, and to prevent the crystal grains of the magnesium alloy member from coarsening as much as possible. On the other hand, the magnesium compound as an intermetallic compound segregates in the structure of the forged blank obtained by casting in the first step 81 described above.
However, at the time of forging, cracks are generated from the segregated portion of the magnesium compound, which causes a problem of poor forgeability.

On the other hand, as a method for producing a magnesium alloy member, for example, Japanese Patent Application No. 3-26 as a prior application of the present applicant.
As described in No. 8357, when a magnesium alloy material (for example, a wheel) is formed by casting, a portion (for example, a rim portion) that is forged (for example, spinning formed) in a later step is chilled during casting. There is a method in which the crystal structure is refined by rapid solidification by the method of rapid cooling using a method such as rapid cooling and then forging by heating the rapid cooling treatment part. However, no consideration is given to segregation of magnesium compounds.

[0007]

SUMMARY OF THE INVENTION The invention according to claim 1 of the present invention is to forge-form by forming a solid solution of a magnesium compound present in the structure of a forging blank made of a magnesium alloy and then forging. It is an object of the present invention to provide a method for manufacturing a magnesium alloy member that can improve the above-mentioned properties and can obtain a member having excellent mechanical properties.

According to the second aspect of the present invention, in addition to the object of the first aspect of the invention, the heat treatment for solid-soluting the magnesium compound also serves as a solution treatment, so that the solution after forging is melted. Compared with the method of applying chemical treatment,
An object of the present invention is to provide a method for manufacturing a magnesium alloy member that can prevent the crystal grains from coarsening.

According to the invention of claim 3 of the present invention, in addition to the object of the invention of claim 1 or 2, by setting the temperature range of the heat treatment to 400 to 450 ° C.,
An object of the present invention is to provide a method for producing a magnesium alloy member, which is capable of sufficiently forming a solid solution of a magnesium compound and performing good homogenization treatment.

According to the invention of claim 4 of the present invention, in addition to the object of the invention of claim 1, 2 or 3, the heat treatment is carried out by performing warm forging continuously to the above heat treatment step. It is an object of the present invention to provide a method for manufacturing a magnesium alloy member, which can effectively utilize the heat energy at that time in a warm forging step to reduce the consumed heat energy.

[0011]

The invention according to claim 1 of the present invention comprises a step of obtaining a forged blank made of a magnesium alloy, and a solid solution of a magnesium compound existing in the structure of the forged blank after the step. A method for manufacturing a magnesium alloy member comprising a heat treatment step and a forging step of forging a forging blank after the heat treatment step.

According to the invention of claim 2 of the present invention, in addition to the constitution of the invention of claim 1, the heat treatment in the heat treatment step also serves as a solution treatment, while the aging treatment is carried out after the forging step. It is a method for manufacturing a magnesium alloy member to be applied.

According to the invention of claim 3 of the present invention, in addition to the constitution of the invention of claim 1 or 2, the heat treatment in the heat treatment step is a magnesium alloy treated at a heating temperature of 400 to 450 ° C. The method is a method for manufacturing a member.

In the invention according to claim 4 of the present invention, in addition to the constitution of the invention according to claim 1, 2 or 3, after the heat treatment, the temperature of the forging blank is continuously increased after the heat treatment. The method is a method for manufacturing a magnesium alloy member in which warm forging is performed by adjusting the temperature to a warm forging temperature.

[0015]

According to the invention of claim 1 of the present invention, the magnesium compound existing in the structure of the forging blank made of magnesium alloy is solid-solved in the above heat treatment step, and then forged. The deviation of the intermetallic compound (magnesium compound) is greatly reduced by the solid solution, and as a result, it is possible to improve the forgeability in the forging process, and at the same time, to improve the tensile strength, elongation, critical upsetting ratio, etc. There is an effect that a magnesium alloy member having excellent mechanical properties can be obtained.

According to the second aspect of the present invention,
In addition to the effect of the invention described in claim 1, since the heat treatment for solid-solving the magnesium compound also serves as the solution treatment, it is not necessary to perform the solution treatment after forging,
Therefore, there is an effect that the coarsening of crystal grains can be prevented as compared with the conventional method in which solution treatment is performed after forging. That is, the solution treatment described above is a high temperature with respect to the artificial aging treatment, crystal grains become coarse when this high temperature solution treatment is performed after forging, but since the solution treatment is performed before the forging step, It is possible to prevent such coarsening of crystal grains.

According to the invention of claim 3 of the present invention,
In addition to the effect of the invention according to claim 1 or 2, the temperature range of the above heat treatment is set to 400 to 450 ° C, so that the bent magnesium compound is sufficiently solid-dissolved in the structure of the forging blank. Therefore, there is an effect that a good homogenization treatment can be performed.

According to the invention of claim 4 of the present invention,
In addition to the effects of the invention according to claim 1, 2 or 3,
Since warm forging is continuously performed in the heat treatment step described above,
The heat energy of the heat treatment can be effectively used in the warm forging step, and as a result, the heat energy consumption can be reduced.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. The drawing shows a manufacturing method of a magnesium alloy member, and a magnesium alloy forged blank is cast-molded in a first step S1 of the process diagram shown in FIG. In this embodiment, as the magnesium alloy member, the upper arm used for the suspension of the automobile is exemplified. Therefore, a cavity having a shape close to the final shape of the upper arm is formed, and the magnesium alloy having the composition shown in Table 1 is next formed to this cavity. The molten AZ80A is cast into a forged blank 1 as shown in FIG.

[0020]

[Table 1]

When mold casting is used in the above-mentioned casting process, the mold temperature is set to about 200 ° C., but instead of this mold casting, sand mold gravity casting, die casting, low pressure casting, A semi-melt injection molding method can also be used. In addition,
When the die casting described above is used, after the forging blank 1 is cast, it is once cooled to room temperature, and then trimming of the riser portion and the gate portion is performed.

Next, in a second step S2 shown in FIG. 1, a heat treatment is carried out to form a solid solution of the magnesium compound present in the structure of the forged blank 1. This heat treatment also serves as a solution treatment, and the heating temperature is in the range of 400 to 450 ° C., preferably about 410 ° C., and the heating time is 10 hours or more.

By carrying out the above-mentioned heat treatment which also serves as such solution treatment, all the magnesium compounds (specifically Mg-Al intermetallic compounds) which are biased in the structure of the forging blank 1 at the time of casting are solid. It is melted and the forgeability in the subsequent process is greatly improved.

Next, in the third step S3 shown in FIG. 1, the current temperature of the forging blank 1 is 400 to 450 ° C., and the warm forging temperature is in the range of 300 to 380 ° C., preferably 350.
Adjust to ℃. Here, when the warm forging temperature exceeds 380 ° C., the surface of the forging blank 1 is oxidized, so the upper limit of the temperature is set to 380 ° C.

Next, in a fourth step S4 shown in FIG. 1, the forging blank 1 is warm forged (wa) by using the upper die and the lower die.
rm forging), a magnesium alloy member 2 corresponding to the upper arm in the final shape can be obtained as shown in FIG. At this point in time, since the burr 3 (flash means flash) exists on the periphery of the above-mentioned magnesium alloy member 2, the magnesium alloy member provided with the burr 3 in the fifth step S5 shown in FIG. After cooling 2 to room temperature, deburring (trimming) is performed,
As shown in FIG. 4, the magnesium alloy member 2 having no burr 3 is used.

Next, in a sixth step S6 shown in FIG. 1, the magnesium alloy member 2 is subjected to artificial aging treatment. That is, the aging treatment temperature is set in the range of 165 to 210 ° C., preferably about 175 ° C., and low temperature heating at this aging treatment temperature is performed for about 16 hours, followed by air cooling.

Next, in a seventh step S6 shown in FIG. 1, after the necessary portions of the magnesium alloy member 2 after the aging treatment are machined such as perforating, an eighth step S8 shown in FIG. Then, apply anti-corrosion treatment.

As described above, the forging blank 1 made of the magnesium alloy in the above heat treatment step (see the second step S2).
The solid solution of the magnesium compound existing in the structure in (1) is followed by forging, so the deviation of the intermetallic compound (Mg-Al compound in this example) is greatly reduced by the solid solution, and as a result, , Forging process (fourth process S4
It is possible to obtain the magnesium alloy member 2 having excellent mechanical properties such as tensile strength, elongation, and limit upsetting rate, as well as improving the forgeability in (see).

Further, the heat treatment for solid solution of the above-mentioned magnesium compound (see the second step S2) also serves as the solution treatment, so that it is not necessary to perform the solution treatment for applying high heat to the member 2 after forging. Therefore, as compared with the conventional method of performing solution treatment after forging, there is an effect that it is possible to prevent coarsening of crystal grains, and the solution treatment in the second step S2 described above and the sixth step described above. Both of the artificial aging treatment in S6 and the T6 treated metal structure can be obtained.

Further, since the temperature range of the heat treatment in the above-mentioned second step S2 is set to 400 to 450 ° C., the unevenly distributed magnesium compound is sufficiently dissolved in the structure of the forging blank 1 to form a good solution. There is an effect that various homogenization treatments can be performed.

In addition, since warm forging is carried out in the fourth step S4 following the above heat treatment step (see the second step S2), the deformation resistance during forging is small and the scale generation is small. Of course, the heat energy during the heat treatment can be effectively used in the warm forging step, and as a result, the heat energy consumption can be reduced.

In order to verify the various effects described above, the diameter 1
6mm ^φ , 24mm height magnesium alloy (specifically A
Z80A), the initial average grain size of the material is 260
Two test pieces of μm were cast in advance under the same conditions,
Forging temperature of one of the tate pieces is 350 ° C, forging rate is 3
After the warm forging at 0%, the solution was subjected to solution treatment by heating at about 400 ° C. for 15 hours, then water-cooled, and then heated at about 175 ° C. for 16 hours and then air-cooled. After subjecting the test piece to solution heating by heating at about 410 ° C. for 20 hours, the temperature was adjusted to about 350 ° C.,
After warm forging at a forging rate of 30%, 1 at about 175 ° C
Example products that were subjected to an aging treatment in which they were heated for 6 hours and then air-cooled were manufactured, and the results of measuring tensile strength, elongation, and critical upsetting ratio for these comparative products and example products are shown in FIG. As shown in FIG.

As is apparent from FIG. 5, the tensile strength of the comparative product is as low as about 300 [MPa], whereas the tensile strength of the example product is improved to about 320 [MPa]. The elongation of the comparative product is as low as about 10%, whereas the elongation of the example product is improved to about 14%.

Further, as is clear from FIG. 6, the limit upsetting ratio of the comparative product is as low as about 60%, whereas the limit upsetting ratio of the embodiment product is improved to about 70%, and the moldability is improved. You can see that it is improving. The marginal upsetting rate is expressed by the following equation 1.

[0035]

[Equation 1]

In the correspondence between the constitution of the present invention and the above-mentioned embodiment, the step of obtaining the forged blank of the present invention corresponds to the first step S1 of the embodiment, and the heat treatment step is the same as the first step S1. 2 corresponds to the step S2, the forging step corresponds to the fourth step S4, and the aging treatment step corresponds to the sixth step S4.
Although it corresponds to No. 6, the present invention is not limited to the configuration of the above-described embodiment.

For example, in the above-mentioned embodiment, the upper arm of the suspension of the automobile is exemplified as the magnesium alloy member, but it goes without saying that it may be applied to the manufacturing method of the wheel and other members.

[Brief description of drawings]

FIG. 1 is a process drawing showing a method for manufacturing a magnesium alloy member of the present invention.

FIG. 2 is a perspective view of a forged blank.

FIG. 3 is a perspective view of a magnesium alloy member having burrs after warm forging.

FIG. 4 is a perspective view of a magnesium alloy member.

FIG. 5 is a characteristic diagram showing the tensile strength and elongation of the example product and the comparative product in comparison.

FIG. 6 is a characteristic diagram showing the limit upsetting ratios of the example product and the comparative product in comparison.

FIG. 7 is a process drawing showing a conventional method for manufacturing a magnesium alloy member.

FIG. 8 is a process chart showing a conventional method for manufacturing a magnesium alloy member.

[Explanation of symbols]

 S1 ... 1st process S2 ... 2nd process (heat treatment process) S3 ... 4th process (forging process) S6 ... 6th process (aging treatment process) 1 ... Forge blank 2 ... Magnesium alloy member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shoji Hirahara 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation

Claims (4)

[Claims] 1. A step of obtaining a forged blank made of a magnesium alloy, a heat treatment step of forming a solid solution of a magnesium compound present in the structure of the forged blank after the above step, and a forging blank after the heat treatment step. A method for manufacturing a magnesium alloy member, comprising a forging step of forming. 2. The method for producing a magnesium alloy member according to claim 1, wherein the heat treatment in the heat treatment step also serves as a solution treatment, while the aging treatment is performed after the forging step. 3. The heat treatment in the heat treatment step is 40
The method according to claim 1 or 2, wherein the treatment is performed at a heating temperature of 0 to 450 ° C.
A method for producing the magnesium alloy member described. 4. The magnesium alloy according to claim 1, wherein after the heat treatment, the temperature of the forging blank is adjusted to the warm forging temperature to carry out the warm forging continuously to the heat treatment. A method of manufacturing a member.