JP4192755B2 - Aluminum alloy member and manufacturing method thereof - Google Patents

Description

  The present invention relates to an aluminum alloy member excellent in castability and forgeability, and excellent in mechanical properties such as tensile strength, yield strength, elongation, and corrosion resistance, and a method for producing the same.

There is a casting forging method in which an aluminum alloy member is obtained by casting an aluminum alloy-based molten metal in a shape approximate to the final shape of the product, and hot forging the resulting cast material. Such a method is employed, for example, when manufacturing a vehicle suspension arm or the like. As such an aluminum alloy having an appropriate composition to which the casting forging method can be applied, JIS-A6061 alloy (aluminum expanded material) with good forgeability, JIS-AC4CH, AC4C (with excellent castability) Various studies have been made on aluminum casting materials) and those having an intermediate composition between these aluminum extension materials and aluminum casting materials. Several casting forging methods using such aluminum alloys are described in the following patent documents.
JP 2002-302728 A Japanese Patent No. 2555182 JP-A-6-73482

  In the above Patent Documents 1, 2, and 3, for example, aluminum alloys that are lightweight and have good mechanical properties are disclosed as aluminum alloy members used for undercarriage parts such as an upper arm and a lower arm of an automobile. Incidentally, undercarriage parts of automobiles are naturally required to have good corrosion resistance as well as good mechanical properties. However, the aluminum alloy members described in the above-mentioned Patent Documents 1, 2, and 3 mainly focus on improving the mechanical properties, and it can be said that sufficient studies have been made on improving the corrosion resistance. Absent.

  For example, in Patent Document 1, as described in paragraph [0028], it is preferable that the strength of the alloy member is improved by forming an Al—Cu-based precipitate by containing Cu. Is described. On the other hand, regarding the corrosion resistance, there is only a description that it is important to set the content of Cu to be small.

  Similarly, in Patent Document 2, as described in paragraph [0014], it is preferable to contain 0.2 to 0.5 wt% of Cu in order to improve the strength of the aluminum alloy member. Are listed. On the other hand, there is almost no description regarding improvement of corrosion resistance, and no experimental results regarding corrosion resistance are disclosed. In addition, in these patent documents 1 and patent documents 2, since content of Si is set comparatively low, there also exists a field that it cannot be said that sufficient castability is realizable.

  Next, in Patent Document 3, forging reduction of 50% or more of an aluminum alloy with Cu: 0.3 wt% or less, Si: 2.5 wt% to 4.0 wt%, and Mg: 0.4 to 0.5 wt% An aluminum alloy member forged at a rate is disclosed. According to this technology, even if Cu is limited to 0.3 wt% or less, sufficient mechanical strength can be realized while suppressing deterioration in corrosion resistance by hot forging under the condition of a forging reduction ratio of 50% or more. It is said. However, even if the Cu content is limited to 0.3 wt% or less, the optimum condition for the Cu content is 0.2 wt% as shown in paragraph [0012] of FIG. In order to improve the mechanical properties of aluminum alloys, it is claimed that the inclusion of Cu is desirable. Further, there is only a qualitative description about the decrease in corrosion resistance due to the inclusion of Cu, and it cannot be said that sufficient measures have been taken for improving the corrosion resistance. This is clear from the fact that the results of the corrosion resistance test are not disclosed.

  Moreover, as an aluminum alloy member used for a suspension arm of an automobile, not only mechanical strength but also mechanical properties such as elongation are required to be good.

  The present invention has been made in view of the above circumstances, has good forgeability and castability, is excellent in mechanical properties such as mechanical strength and elongation after forging, and also has corrosion resistance. It is an object to provide an excellent aluminum alloy member and a method for producing such an aluminum alloy member.

In an aluminum alloy member for a suspension arm hot forged from an approximate shape cast material having a shape close to the final product shape, Si: 3.0 to 4.2 wt%, Mg: 0.4 to 0.6 wt%, Zn , Mn, Ni, Sn, Cr total amount: 0.5 wt% or less, the balance is inevitable impurities and Al composition, Cu is not included as an essential additive element, inevitably included Cu to be added is 0.02% wt or less and Fe: 0.2 wt% or less.

Furthermore, in order to solve the above-described problems of the present invention, the manufacturing method of an aluminum alloy member for a suspension arm according to the present invention includes Si: 3.0 to 4.2 wt%, Mg: 0.4 to 0.6 wt% , Fe : 0.2 wt% or less, the total amount of Zn, Mn, Ni, Sn, Cr: 0.5 wt% or less, the balance is made of inevitable impurities and Al, and Cu as an essential additive element Cu, which is unavoidably contained, is an approximation that has an aluminum alloy composed of an aluminum alloy that is 0.02% wt or less and Fe: 0.2 wt% or less, in a shape that approximates the shape of the final product. Casting into a shape cast material;
A method for producing an aluminum alloy member for a suspension arm , comprising: hot forging the approximate shape cast material under a forging reduction ratio of 30 to 50%. Here, the forging reduction ratio refers to a reduction rate of the thickness when the thickness of the approximate shape cast material is changed by the forging process.

  Furthermore, in the manufacturing method of the aluminum alloy member of the present invention, the forged member obtained by the hot forging step of the approximate shape cast material is rapidly cooled after the solution treatment, and in the temperature range of 155 to 165 ° C., 6 An aging treatment of ˜8 hours can be performed.

  The present inventor is an aluminum that has sufficient mechanical properties such as mechanical strength and elongation rate by hot forging an approximate shape cast material having a shape approximate to the final product without substantially adding Cu. The present inventors have found that an alloy member can be realized, and have completed the present invention. According to the aluminum alloy member of the present invention as described above, in an aluminum alloy member obtained by forging an approximately-shaped cast material after casting, the castability and forgeability are maintained well, and good mechanical strength is obtained. In order to achieve this, the contents of Si and Mg are defined within a predetermined range, and, unlike conventional aluminum alloy members, Cu is not included as an essential additive element. Therefore, the corrosion resistance is remarkably improved as compared with a conventional aluminum alloy containing Cu for improving the mechanical strength. Furthermore, since it is hot-forged under desired conditions, mechanical properties such as mechanical strength and elongation rate are comparable to conventional aluminum alloy members. Therefore, according to the present invention, it is possible to realize an aluminum alloy member that maintains excellent castability and forgeability, is excellent in corrosion resistance, and is inferior in mechanical properties.

  And it was found that by employing the method for producing an aluminum alloy member of the present invention, an aluminum alloy member having sufficient mechanical strength can be obtained without actively adding Cu to the aluminum alloy. In other words, by setting the forging reduction rate when hot forging the approximate shape cast material in the range of 30 to 50%, sufficient mechanical strength and the like can be obtained without adding Cu to the alloy actively. It was found that mechanical properties could be realized. In hot forging, it is considered that mechanical properties such as tensile strength and elongation rate are generally improved by increasing the forging reduction ratio. However, when the present inventors have studied, Cu is contained as an essential additive element. In the case where the forging reduction ratio is not less than 50%, the improvement in the mechanical properties such as tensile strength, proof stress and elongation rate has reached its peak, and it may be lowered. Forging improves mechanical properties by eliminating shrinkage and pinholes formed in the structure of aluminum alloy members and densifying the structure, but if the forging reduction ratio exceeds 50%, It is considered that the degree of the orientation of the structure becomes too strong and induces a decrease in mechanical properties (particularly, tensile strength). The forging reduction ratio of 50% means that the thickness of the approximate shape cast material before forging is reduced by 50% after forging. On the other hand, when the forging reduction rate is less than 30%, the elongation rate of the aluminum alloy member cannot be sufficiently maintained. When an aluminum alloy member used for an automobile suspension arm is exemplified, it is desirable to achieve an elongation of 11% or more in order to obtain a sufficient elongation, but the forging reduction ratio is 30% or more. By doing so, it becomes possible to set the elongation rate of an aluminum alloy member in the favorable range of 11% or more.

  Thus, according to the method for producing an aluminum alloy member of the present invention, castability and forgeability are sufficiently maintained, mechanical properties such as mechanical strength and elongation rate are excellent, and corrosion resistance is also excellent. An aluminum alloy member can be manufactured.

  Furthermore, in order to improve the mechanical strength of the aluminum alloy member as described above, it is effective to supply the aluminum alloy member to a solution treatment after the forging step, and then rapidly cool and supply to the aging treatment. . As a solution treatment condition, a temperature range of 155 to 165 ° C. and an aging time range of 6 to 8 hours can be set. If the temperature is lower than 155 ° C., the mechanical properties (particularly, tensile strength) are inferior, and if the temperature exceeds 165 ° C., the precipitate is not sufficiently precipitated and a sufficient elongation can be realized. There is a problem that you can not. Further, if the aging treatment time is less than 6 hours, precipitates are not sufficiently precipitated, and the strength (particularly tensile strength) is not sufficient, and if it exceeds 8 hours, the strength of the aluminum alloy member is improved. However, there is a problem that the elongation rate decreases rapidly.

  Hereinafter, the reasons for limiting the composition of the aluminum alloy member of the present invention will be described.

  (Si: 3.0 to 4.2 wt%) Si is an element that can improve the flowability and shrinkage of molten metal, suppress the occurrence of casting cracks, and improve the castability. If Si is excessive, the plastic deformability is impaired, and the elongation and mechanical strength are likely to be lowered. Therefore, the Si content is set within the above range. If the Si content is less than 3.0 wt%, the effect of containing Si as described above is not sufficiently exerted. On the other hand, if the Si content exceeds 4.2 wt%, the mechanical strength is increased. Damage. The Si content is desirably 3.0 to 4.2 wt%, and more desirably 3.0 to 4.0 wt%.

(Mg: 0.4 to 0.6 wt%) Mg is contained in the presence of Si, so that Mg ₂ Si is generated in the structure of the aluminum alloy, and the tensile strength, proof strength, etc. are reduced by precipitation hardening with this compound. It is an element that can improve the mechanical strength. However, when it contains excessively, the elongation rate and impact value of an aluminum alloy member will fall. Therefore, the content of Mg is set in the above range. The Mg content is desirably 0.35 to 0.65 wt%, and more desirably 0.40 to 0.60 wt%.

  (Cu: not contained as an essential additive element) As described above, according to the present invention, the corrosion resistance of the aluminum alloy member can be significantly improved by substantially not adding Cu. Conventionally, in order to improve the mechanical strength of an aluminum alloy member used, for example, in an automobile suspension arm or the like, it has been strongly believed that Cu is essential. However, according to the manufacturing method of the present invention, Cu is substantially reduced. Even if it is not contained, an aluminum alloy member having excellent mechanical strength and excellent corrosion resistance can be produced. Therefore, Cu is preferably not contained as much as possible, but may be contained as an inevitable impurity. When Cu is contained as an inevitable impurity in the aluminum alloy member, the Cu content can be 0.02 wt% or less. Furthermore, in the aluminum alloy member in which Cu as an inevitable impurity is suppressed, the Cu content can be 0.01 wt% or less.

  (Fe: 0.2 wt% or less) Fe causes nests to adversely affect castability, and also adversely affects forgeability by impairing plastic deformability. Therefore, it is desirable to set the content of Fe as an inevitable impurity as low as possible. When the Fe content exceeds 0.2 wt%, shrinkage cavities (microporosity) formed in the approximate shape cast material increase and cracks occur in the forged product obtained when forging the approximate shape cast material. It becomes easy.

  (The total content of Zn, Mn, Ni, Sn, and Cr is 0.5 wt% or less) If Zn is excessive, the corrosion resistance is lowered. Therefore, it is preferable to limit the content of the aluminum alloy member of the present invention for the purpose of improving corrosion resistance as much as possible. On the other hand, if the Mn content is excessively large, slats are likely to occur. Moreover, when Ni and Sn are contained excessively, corrosion resistance tends to deteriorate. Moreover, when there is too much content of Cr, the production | generation of a slat is assisted. The content of these elements is desirably limited for the reasons described above, and the above problems can be prevented by setting the total content of these elements to 0.5% or less.

  Embodiments of the present invention will be described below with reference to the drawings. A mold 1 used in a casting process according to the present embodiment is a mold equipped in a casting mold apparatus having a swing function, and manufactures a vehicle suspension arm that is a representative example of a component requiring high strength and high corrosion resistance. Is for. As schematically shown in FIG. 1, the mold 1 has a first cavity 11 that approximates the shape of the final product and a second cavity 12 that communicates with the first cavity 11. The front is a horizontal type. Then, molten aluminum alloy is poured into the first cavity 11 of the mold 1.

  Here, the molten aluminum alloy-based molten metal is Si: 3.0 to 4.2 wt%, Mg: 0.4 to 0.6 wt%, Fe: 0.2 wt% or less, Zn, Mn, Ni, The total content of Sn and Cr: 0.5 wt% or less, the balance is composed of inevitable impurities and Al, and Cu is not contained as an essential additive element. Specifically, when Cu is not contained as an essential additive element, Cu inevitably contained can be, for example, 0.02% by weight or less, and further 0.01% by weight.

  In the casting process, the temperature of the molten metal can be generally 720 to 750 ° C. The mold temperature of the mold 1 can generally be set to 250 to 350 ° C. In the casting process, pouring is performed from the dam opening 12x by providing the dam opening 12x on the second cavity 12 side. When the first cavity 11 and the second cavity 12 are filled with molten metal, the horizontal mold 1 is swung to form a vertical mold (not shown) so that the first cavity 11 faces upward. If it does in this way, in the casting process, while the molten metal of the 1st cavity 11 will be solidified early, solidification of the 2nd cavity 12 will be delayed. Thus, if the molten metal is directional solidified, even if the approximate shape cast material 2 that is a cast product has a complicated shape, it is possible to suppress the occurrence of shrinkage and pinholes in the cast product to be formed. be able to. When the entire molten metal is solidified, the mold 1 is leveled again, the mold 1 is opened, and an approximate shape casting 2 as schematically shown in FIG. 2 can be obtained. The approximate shape cast material 2 has a main body 2a having an arm shape, a boss portion 2s in which a bolt insertion hole is formed, and boss portions 2b and 2c in which a bolt insertion hole is formed. The solidification time depends on the size and shape, but is generally about 30 to 120 seconds, particularly about 40 to 80 seconds. However, it is not limited to this.

Next, the forging process concerning this embodiment is demonstrated. In the forging process according to the present embodiment, the approximately shaped cast material 2 that has once returned to room temperature is heated in the atmosphere to a required temperature (for example, about 430 ° C.). Then, as shown in FIG. 3, the approximate shape cast material 2 is arranged in the forging die 4, and hot forging is performed by forging die 4 in the thickness direction of the approximate shape cast material 2 to obtain a cast forged product 5. . The forging die 4 has a metal upper die 43 and a lower die 41 having a flat lower surface 40. The forging die 4 has a forging cavity 46 formed by recessing the lower split surface 40 and the upper split surface 42, and a burr forming space 47 formed so as to make a round around the forging cavity 46. The temperature of the approximate shape cast material 2 at the time of forging is generally 390 to 430 ° C. In the forging process, hot casting is performed by strongly pressing the approximate shape casting agent 2 in the thickness direction at the die surface 46f of the forging cavity 46. The forging process is semi-sealed forging that actively generates burrs while forging, and the inner portion of the approximate shape casting material 2 escapes to the outer space 47 due to strong pressure, and around the approximate shape forging material 2. A cast forged material 5 having a burr 20 is formed. The bosses 2s, 2b, and 2c in which the main body 2a and bolt insertion holes are formed are strengthened by forging. The burrs 20 are formed in the central region in the thickness direction of the cast forged product 5. The cast forged product 5 has a forged surface 5 f that is strongly pressed by the die surface 46 f of the forging die 4. In the forging step described above, the forging reduction rate for forging the side near the second cavity 12 of the approximate shape casting material 2 is αn, and the forging reduction rate for forging the side far from the second cavity 12 of the approximate shape casting material 2. Where αd> αd. In the present embodiment, the approximately shaped casting material 2 is solidified in the form of directional solidification. Therefore, in the portion of the approximate shape cast material 2 formed by the first cavity, the occurrence of defects such as pinholes is suppressed. However, even with the approximate shape cast material 2 formed of the first cavity, a close or pinhole may occur on the side close to the second cavity where solidification is delayed depending on the shape. Therefore, as described above, by setting αn> αd, even if a shrinkage or a pinhole is formed in the portion of the approximate shape cast material 2 on the side close to the second cavity 12, these shrinkage and It becomes easy to crush the pinhole. Therefore, it can contribute to the improvement of the mechanical strength of the aluminum alloy member.

  In the forging step described above, a method in which the forging reduction ratio is set within a range of 30 to 50% can be employed. The cross-sectional reduction rate is preferably set to 30% or less, particularly 15% or less. As described above, in the aluminum alloy member according to the present invention which does not substantially contain Cu, the tensile strength and the elongation rate increase as the forging reduction rate is increased from 0% to 50%. However, when the forging reduction rate exceeds 50%, the tensile strength, the elongation rate, and the like decrease. On the other hand, if the forging reduction ratio is less than 30%, sufficient tensile strength, proof stress, elongation rate and the like cannot be realized. For example, in an aluminum alloy member used for undercarriage parts such as an automobile suspension arm, it is desired that the elongation rate is 11% or more, and the elongation rate of the aluminum alloy member is 11% or more. For this, the forging reduction ratio is preferably 30% or more. Here, when the cross-section reduction rate is 30% or less, the flesh portion basically corresponding to the cross-section reduction rate becomes the burr portion 20.

  According to the present embodiment, the degree of orientation through which the metal structure flows is large in the central region in the thickness direction of the cast forged product 5. However, in the cast forged product 5, the degree of orientation through which the metal structure flows was not recognized on the forged surface 5 f near the die surface 46 f of the forged cavity 46. Therefore, in the casting forged product 5, the casting chill structure remains in the casting process near the die surface 46 f of the forging cavity 46.

  In order to confirm that the aluminum alloy member according to the present invention exhibits good mechanical properties and excellent corrosion resistance, or by the method for producing an aluminum alloy member according to the present invention, it has excellent mechanical properties and corrosion resistance. In order to confirm that an aluminum alloy can be produced, the following experiment was conducted.

  (Experimental example 1) An aluminum alloy having a composition as shown in Table 1 (the balance is Al) is used as a molten metal, and an approximate shape casting material as shown in FIG. Got. Casting conditions are: molten aluminum temperature: 720 ° C., casting mold temperature: 250-350 ° C. After the obtained approximately shaped cast material was heated to 430 ° C., as shown in FIG. 3, a cast forged product was produced by hot forging with a cross-sectional reduction rate of 10% and a forging reduction rate of 30%. The obtained cast forged product was subjected to heat treatment. Specifically, solution treatment was performed at 540 ° C. for 6 hours, and in that state, treatment was performed at 160 ° C. for 8 hours.

図５のような状態の耐食性試験片に対して、ボルト６により１５０〜２００ＭＰａの応力を付与しつつ、塩水噴霧試験を行った。そして耐食性試験片の断面において、顕微鏡観察を行い、該断面に粒界腐食が発生しているかどうかを評価した。応力は、図５に示すように試験片１０に取り付けられた歪ゲージ８により測定した。

表２よりわかるように、Ｃｕを実質的に添加していない、Ｃｕの含有量が０．０１ｗｔ％の試料では、粒界腐食が全く発生せず、極めて良好な耐食性を実現できることがわかる。一方、Ｃｕの含有量を制限している、Ｃｕの含有量が０．３３ｗｔ％や０．２６ｗｔ％である試料においては、粒界腐食が観察された試料が、全体の１０％程度もあり、十分な耐食性が実現されていないことがわかる。 The cast forged product thus obtained was subjected to a corrosion resistance test according to the following procedure. First, the corrosion resistance test piece 10 was formed into a shape shown in FIG. 4 from the cross section of the cast forged product. The dimensions of the test piece are as shown in FIG. And the corrosion-resistant test piece of such a shape was assembled | attached in the form as shown in FIG. 5 so that stress can be provided. Specifically, circular through-holes 10 a were formed in the flange portions of the U-shaped corrosion resistance test pieces, and bolts 6 were inserted into the through-holes 10 a and fixed with nuts 7. Specifically, it assembled | attached as shown in FIG.

A salt spray test was performed on the corrosion resistance test piece in the state shown in FIG. 5 while applying a stress of 150 to 200 MPa with the bolt 6. And in the cross section of the corrosion-resistant test piece, the microscope observation was performed and it was evaluated whether the intergranular corrosion had generate | occur | produced in this cross section. The stress was measured with a strain gauge 8 attached to the test piece 10 as shown in FIG.

As can be seen from Table 2, in the sample with substantially no Cu added and a Cu content of 0.01 wt%, intergranular corrosion does not occur at all, and it can be seen that extremely good corrosion resistance can be realized. On the other hand, in the sample where the Cu content is limited and the Cu content is 0.33 wt% or 0.26 wt%, there are about 10% of the samples in which intergranular corrosion is observed, It can be seen that sufficient corrosion resistance is not realized.

表３に示すように、鍛造圧下率が３０％以上の試料においては、比較的高い引張強さ及び耐力を実現することができるとともに、１１％以上の伸び率を実現することができ、例えば自動車の足回り品として好適なアルミニウム合金部材を得ることができる。しかしながら、鍛造圧下率が５０％を越えると、アルミニウム合金部材の伸び率の増加が飽和し、引張り強さや耐力は低下してしまう。したがって、Ｃｕを実質的に含有しないアルミニウム合金部材の場合、鍛造工程における鍛造圧下率は、３０〜５０％の範囲に設定するのが好ましいことがわかる。 (Experimental example 2) Next, sample No. which does not contain Cu substantially as an essential addition element of Table 1 is shown. As shown in Table 3, a plurality of aluminum alloy members having the composition 1 having different forging reduction ratios in the forging process were produced. Conditions in the steps other than the forging step are the same as those in Experimental Example 1. A tensile strength test piece 15 was formed into a shape as shown in FIG. 6 from the aluminum alloy member thus obtained. Using such a tensile test piece, the tensile test specified in JISZ2241 was performed, and the tensile strength, proof stress, and elongation rate of the sample were measured. The obtained results are shown in Table 3.

As shown in Table 3, in a sample having a forging reduction ratio of 30% or more, a relatively high tensile strength and yield strength can be realized, and an elongation ratio of 11% or more can be realized. An aluminum alloy member suitable as an underbody product can be obtained. However, if the forging reduction rate exceeds 50%, the increase in the elongation rate of the aluminum alloy member is saturated, and the tensile strength and proof stress are reduced. Therefore, in the case of the aluminum alloy member which does not contain Cu substantially, it turns out that it is preferable to set the forge reduction rate in a forging process in the range of 30 to 50%.

表４に示すように、時効時間が６〜８時間の範囲では、Ｃｕを強度向上を目的として含有するアルミニウム合金と遜色ない程度の、引張強さ及び耐力を実現でき、さらに、１１％以上の伸び率を確保することができることがわかる。時効時間が６時間に満たないと、十分な引張強さ及び耐力を実現することができず、時効時間が８時間を越えると、１１％以上の伸び率を実現することができない。 (Experimental example 3) Next, sample No. In the aluminum alloy member having the composition 1, a plurality of aluminum alloy members were prepared by changing the aging time in the aging treatment as shown in Table 4. In the forging process, the cross-sectional reduction rate was 10%, and the forging reduction rate was 40%. In the aging treatment, the temperature of the atmosphere to which the aluminum alloy member is exposed is set to 160 ° C. as in Experimental Example 1. In addition, the production conditions other than the aging time are the same as in Experimental Example 1. A tensile test was performed on the aluminum alloy member thus obtained by the same method as in Experimental Example 2. The results are shown in Table 5.

As shown in Table 4, when the aging time is in the range of 6 to 8 hours, the tensile strength and the proof stress are comparable to those of an aluminum alloy containing Cu for the purpose of improving the strength, and more than 11%. It can be seen that the elongation rate can be secured. If the aging time is less than 6 hours, sufficient tensile strength and proof stress cannot be realized, and if the aging time exceeds 8 hours, an elongation of 11% or more cannot be realized.

  From the above experiments, it was confirmed that the aluminum alloy member of the present invention was excellent in mechanical properties and also had high corrosion resistance. Furthermore, according to the method for producing an aluminum alloy member of the present invention, it was confirmed that an aluminum alloy member having excellent mechanical properties and high corrosion resistance can be produced.

The figure for demonstrating a casting process. The top view which shows an approximate shape casting material typically. Sectional drawing which shows the state which is forging the approximate shape casting material with the die surface of a forging die. The figure explaining the shape of a corrosion-resistant test piece. The figure explaining the attachment structure of a corrosion-resistant test piece and a volt | bolt. The figure for demonstrating the shape of a tensile strength test piece.

Explanation of symbols

2 Cast material with approximate shape 5 Aluminum alloy member

Claims (3)

In an aluminum alloy member hot forged from an approximate shape cast material having a shape approximate to the final product shape,
Si: 3.0 to 4.2 wt%, Mg: 0.4 to 0.6 wt% , Zn, Mn, Ni, Sn, Cr total amount: 0.5 wt% or less, the balance is inevitable impurities and The composition is made of Al,
An aluminum alloy member for a suspension arm , which does not contain Cu as an essential additive element, and unavoidably contained Cu is 0.02% wt or less and Fe: 0.2 wt% or less. Si: 3.0-4.2 wt%, Mg: 0.4-0.6 wt%, Fe: 0.2 wt% or less, Zn, Mn, Ni, Sn, Cr total amount: 0.5 wt% or less Containing, the balance is made of inevitable impurities and Al,
In addition, Cu is unavoidably contained as an essential additive element, and Cu contained unavoidably is 0.02% wt or less, Fe: 0.2 wt% or less, an aluminum alloy composed of an aluminum alloy is used as the final product. Casting into an approximate shape cast material having a shape close to the shape;
A method for producing an aluminum alloy member for a suspension arm , comprising: hot forging the approximate shape cast material under a forging reduction ratio of 30 to 50%. The forged member obtained by the hot forging step of the approximate shape cast material is rapidly cooled after the solution treatment, and is subjected to an aging treatment for 6 to 8 hours in a temperature range of 155 to 165 ° C. Item 3. A method for producing an aluminum alloy member for a suspension arm according to Item 2.

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