Method for manufacturing aluminum alloy member and shot peening apparatus

Abstract

To provide a technique capable of appropriately maintaining fatigue strength of an aluminum alloy member.SOLUTION: A method for manufacturing an aluminum alloy member includes a step of preparing an aluminum alloy member made of an aluminum alloy, and a step of adding residual stresses to the aluminum alloy member by applying shot peening on the aluminum alloy member in a range in which speed of shots when the shots come into contact with the aluminum alloy member becomes 1 m / s to 7 m / s .SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an aluminum alloy member and a shot peening apparatus. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing an aluminum alloy member made of an aluminum alloy. The manufacturing method includes a step of subjecting the aluminum alloy member to shot peening. In the shot peening, shot material with a smaller particle size than conventional shot material is used, and the shot peening treatment is performed using compressed air at a faster injection speed than conventional methods. This shot peening treatment improves the fatigue life by 5 to 10 times compared to conventional shot peening treatment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-188720 Summary of the Invention [Problem to be solved by the invention]

[0004] The manufacturing method described in Patent Document 1 may result in a decrease in the fatigue strength of the aluminum alloy member over time. Shot peening introduces strain into the interior (surface layer) of the aluminum alloy member, imparting residual stress (residual compressive stress). This residual stress is released when a β phase is formed on the strain. Because the aluminum alloy member contains elements that form the β phase, β phase compounds are precipitated in the aluminum alloy over time. When the β phase compounds are precipitated, the internal strain in the aluminum alloy is relaxed. When the residual stress is released over time, it causes a decrease in the fatigue strength of the aluminum alloy member. The present disclosure provides a technology that can appropriately maintain the fatigue strength of an aluminum alloy member. [Means for solving the problem]

[0005] A method for manufacturing an aluminum alloy member according to one aspect of the present disclosure includes the steps of: preparing an aluminum alloy member made of an aluminum alloy; and shot peening the aluminum alloy member so that the speed of the shot when it contacts the aluminum alloy member is in a range of 1 m / s to 7 m / s, thereby imparting residual stress to the aluminum alloy member.

[0006] A shot peening apparatus according to another aspect of the present disclosure is a shot peening apparatus that applies shot peening to an aluminum alloy member made of an aluminum alloy, and includes: a hopper that stores shot; a pipe member that communicates with the hopper and allows the shot to pass through; and a support member that is disposed vertically below a lower end of the pipe member and supports the aluminum alloy member. [Effects of the Invention]

[0007] According to the present disclosure, the fatigue strength of an aluminum alloy member can be appropriately maintained. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a flowchart of a manufacturing method according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a shot peening device according to an embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of a shot peening device according to an embodiment. [Figure 4] FIG. 4 is a graph showing the residual stress imparted using the first shot and the second shot. [Figure 5] FIG. 5 is a graph showing the relationship between the residual stress and the elapsed time of the aluminum alloy members in the examples and the comparative examples. [Figure 6] FIG. 6 is a graph showing the relationship between the residual stress of the aluminum alloy member and the elapsed time, obtained for each shot speed. [Figure 7]FIG. 7 is a graph showing the relationship between the stress amplitude and the number of repetitions of the aluminum alloy members in the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicate descriptions will be omitted. The dimensional ratios of the drawings do not necessarily match those in the description. The terms "upper," "lower," "left," and "right" are based on the illustrated state and are for convenience only.

[0010] [Summary of manufacturing method for aluminum alloy components] The manufacturing method according to the present disclosure produces an aluminum alloy member having residual stress. The produced aluminum alloy member can be used in items handled by people, such as sporting goods (bicycles, golf clubs, fishing tackle, bats, etc.), work implements (agricultural implements, gardening implements, etc.), and daily necessities (wheelchairs, eyeglasses, chairs, etc.). These products can achieve sufficient performance with a fatigue strength lower than that of automobile parts, railway parts, aircraft parts, etc. (for example, 50 MPa to 350 MPa, or 70 MPa to 300 MPa).

[0011] Residual stress imparted to an aluminum alloy member is gradually released over time. The aluminum alloy member is composed of an aluminum alloy. In the aluminum alloy, β-phase compounds are precipitated over time. When the aluminum alloy contains at least one element selected from Mg, Cu, Mn, and Si, the reaction between these elements and aluminum makes it easier for β-phase compounds to form on the strain introduced into the aluminum alloy member. When the β-phase compounds are precipitated, the strain in the aluminum alloy member is relaxed and the residual stress is released. When the residual stress is released over time, it causes a decrease in the fatigue strength of the aluminum alloy member. Below, a method for manufacturing an aluminum alloy member that can appropriately maintain fatigue strength is described.

[0012] 1 is a flowchart of a manufacturing method according to an embodiment. As shown in FIG. 1, in step S10, an object is prepared. The object is an aluminum alloy member made of an aluminum alloy, and the aluminum alloy may contain at least one element selected from Mg, Cu, Mn, and Si.

[0013] Subsequently, in step S12, the object is peened. The peening is shot peening. Shots (shot media) with a high specific gravity are used. The specific gravity of the shot is, for example, 3.8 or more. There is no particular upper limit to the specific gravity of the shot, but it may be, for example, 6.0 or less. The specific gravity of the shot may be in the range of 3.8 to 6.0 and the Vickers hardness may be in the range of HV600 to HV1200. One example of a material that satisfies these specific gravity and Vickers hardness requirements is zirconia. The shape of the shot may be spherical. The diameter φ of the shot may be 0.05 mm to 2.0 mm.

[0014] This shot peening contacts the target with the shot at a low speed. As a specific example, when the shot contacts an aluminum alloy member, the speed of the shot ranges from 1 m / s to 7 m / s. By setting the speed of the shot to be from 1 m / s to 7 m / s, the release of the applied residual stress is suppressed. When the speed of the shot is less than 1 m / s, the residual stress immediately after peening is as small as about -100 MPa, and furthermore, the effect of suppressing the release of the residual stress becomes extremely small. When the speed of the shot exceeds 7 m / s, the effect of suppressing the release of the residual stress decreases compared to the case where the speed of the shot is from 1 m / s to 7 m / s. Incidentally, the speed of the shot may range from 1.0 m / s to 6.5 m / s. The speed of the shot may range from 1 m / s to 5 m / s. By setting the speed of the shot to be from 1 m / s to 5 m / s, the effect of suppressing the release of the residual stress is stable, and the change in the residual stress over time becomes small, so that quality control becomes easy. The above-described speed of the shot may be realized by a blower that does not use compressed air, or may be realized by allowing the shot to freely fall from above the aluminum alloy member to reach the aluminum alloy member. By performing shot peening, residual stress is applied to the aluminum alloy member.

[0015] When step S12 ends, the flowchart shown in FIG. 1 ends. According to the manufacturing method shown in FIG. 1, since it becomes difficult for the residual stress of the aluminum alloy member to be released, the fatigue strength of the aluminum alloy member is appropriately maintained. Although the reason why it becomes difficult for the residual stress of the aluminum alloy member to be released is not known, from the first timing when a predetermined time T1 has elapsed after a series of operations are completed to the second timing when a predetermined time T2 has elapsed after a series of operations are completed, the release rate of the residual stress ({(residual stress at the first timing) - (residual stress at the second timing)} ÷ (residual stress at the first timing) × 100) (hereinafter referred to as "release rate of residual stress") is 15% or less, and it has been found as a result of experiments that the attenuation of the residual stress almost stops thereafter. Here, the relationship of T1≧0 and T1<T2 can be satisfied. For example, T1 may be 20 hours and T2 may be 160 hours.

[0016] Furthermore, because shot peening can be performed without using compressed air, a compressor is not required. Therefore, the manufacturing method shown in Figure 1 improves the energy consumption efficiency of factories and reduces CO2 emissions.

[0017] [Shot peening equipment overview] An example of a shot peening apparatus that can be used in step S12 shown in Fig. 1 is shown. Fig. 2 is a diagram illustrating an example of a shot peening apparatus according to an embodiment. The shot peening apparatus 1 shown in Fig. 2 includes a chamber 2. The chamber 2 is hollow. An aluminum alloy member 10 to be treated is placed inside the chamber 2.

[0018] A hopper 3 is provided above the chamber 2. The hopper 3 stores shot 4. The shot 4 has a specific gravity of 3.8 or more. The specific gravity of the shot may be 6.0 or less. A pipe member 5 is provided at the lower end of the hopper 3, communicating with the hopper 3 and allowing the shot 4 to pass through. The lower end of the pipe member 5 communicates with the interior of the chamber 2. An opening / closing gate 6 is provided on the pipe member 5. When the opening / closing gate 6 is opened, the shot 4 stored in the hopper 3 falls freely, passes through the pipe member 5, and reaches the interior of the chamber 2. A support member 2a is provided inside the chamber 2, supporting an aluminum alloy member 10. The support member 2a is positioned vertically below the lower end of the pipe member 5. The freely falling shot 4 is guided by the pipe member 5 and projected onto the aluminum alloy member 10. The speed at which the shot 4 contacts the aluminum alloy member 10 can be determined by the height from the opening / closing gate 6 to the aluminum alloy member 10.

[0019] The interior of the chamber 2 may be divided into a processing chamber S1 and a recovery chamber S2 by a support member 2a. In this case, the support member 2a has a plurality of openings through which the shots 4 can pass. The shots 4 projected onto the aluminum alloy member 10 pass through the support member 2a and are collected in the recovery chamber S2. The shots 4 collected in the recovery chamber S2 are transported to a hopper 3 by a transport device (not shown).

[0020] According to the shot peening apparatus 1, the speed of the shots 4 when they contact the aluminum alloy member 10 can be set to a range of 1 m / s to 7 m / s by combining the specific gravity of the shots 4 and the height from the opening / closing gate 6 to the aluminum alloy member 10. This makes it difficult for residual stress in the aluminum alloy member 10 to be released, and the fatigue strength of the aluminum alloy member 10 is appropriately maintained. Furthermore, the shot peening apparatus 1 shown in FIG. 2 can perform shot peening without using compressed air, eliminating the need for a compressor. This improves the energy consumption efficiency of the factory and reduces CO2 emissions.

[0021] Next, other shot peening apparatuses that can be used in step S12 shown in Fig. 1 will be illustrated. Fig. 3 is a diagram illustrating an example of a shot peening apparatus according to an embodiment. The shot peening apparatus 1A shown in Fig. 3 is the same as the shot peening apparatus 1 shown in Fig. 2 except for the positions of the hopper, the pipe member, and the fact that a blower 7 is provided on the pipe member. The following description will focus on the differences, and redundant description will be omitted.

[0022] The hopper 3 is disposed to the side of the chamber 2. A pipe member 5A is provided at the lower end of the hopper 3, communicating with the hopper 3 and allowing the shots 4 to pass through. The pipe member 5A has a bent tip, extends from the lower end of the hopper 3 to the side of the chamber 2, and communicates with the interior of the chamber 2. A blower 7 is provided at the pipe member 5A. The blower 7 is a device that blows air without using compressed air. When the blower 7 blows air, the shots 4 stored in the hopper 3 pass through the pipe member 5A and reach the interior of the chamber 2. The shots 4 are guided horizontally by the pipe member 5A and projected onto the side of the aluminum alloy member 10. The speed at which the shots 4 contact the aluminum alloy member 10 can be determined by the air blow rate, which is adjusted within a range of 1 m / s to 7 m / s. Similar to the shot peening apparatus 1, the shot peening apparatus 1A can appropriately maintain the fatigue strength of the aluminum alloy member 10, improve the energy consumption efficiency of the factory, and reduce CO2 emissions.

[0023] Although various exemplary embodiments have been described above, various omissions, substitutions, and modifications may be made without being limited to the above exemplary embodiments.

[0024] For example, the shot peening device 1A may employ a projector that uses centrifugal force instead of the blower 7. [Example]

[0025] The effects of the manufacturing method and apparatus of the present disclosure will be described based on examples and comparative examples.

[0026] (Verification of shots that can impart residual stress) An aluminum alloy member made of an aluminum alloy specified in JIS (Japanese Industrial Standards) A7075 was prepared. Next, the aluminum alloy member was subjected to free-fall shot peening using a shot peening apparatus 1 shown in Figure 2. The shot peening consisted of a first shot with a specific gravity of 3.8 and a Vickers hardness of HV600, and a second shot with a specific gravity of 6.0 and a Vickers hardness of HV1200. The residual stress of the aluminum alloy member after the first shot and the second shot were measured. An X-ray residual stress measurement device (μ-X360s, manufactured by Pulstec Industrial Co., Ltd.) was used for the measurements. The results are shown in Figure 4.

[0027] FIG. 4 is a graph showing the residual stress imparted using the first shot and the second shot. The vertical axis represents the absolute value of the residual stress. As shown in FIG. 4, the residual stress imparted using the first shot was approximately 350 MPa, and the residual stress imparted using the second shot was approximately 400 MPa. This confirms that a shot with a specific gravity of 3.8 or higher and a Vickers hardness of HV600 or higher can impart sufficient residual stress.

[0028] (Verification of maintenance of residual stress) Example 1 An aluminum alloy member made of an aluminum alloy specified in JIS A7075 was prepared as Example 1. Next, the aluminum alloy member was subjected to free-fall shot peening using a shot peening apparatus 1 shown in Fig. 2. For the shot peening, shots were used that were spherical in shape, had a diameter φ of 0.6 mm to 0.8 mm, were made of zirconia, had a specific gravity of 6.2, and had a Vickers hardness of HV1180.

[0029] (Comparative Example 1) For Comparative Example 1, the same aluminum alloy member as in Example 1 was prepared. Next, shot peening was performed using a shot peening device (ABT type manufactured by Shinto Kogyo Co., Ltd.). For the shot peening, shots were used that were spherical in shape, had a diameter of 0.6 mm, were made of cast steel, had a specific gravity of 7.5, and had a Vickers hardness of HV600. The shot peening conditions were an injection pressure of 0.1 MPa, and an injection rate of the shot medium of 5 kg / min.

[0030] Then, the changes in residual stress over time were measured for the aluminum alloy members of Example 1 and Comparative Example 1. An X-ray residual stress measurement device (μ-X360s manufactured by Pulstec Industrial Co., Ltd.) was used to measure the residual stress. The measurements were carried out multiple times between 0 and 200 hours. The results are shown in Figure 5.

[0031] Fig. 5 is a graph showing the relationship between the residual stress and elapsed time of the aluminum alloy members in the examples and comparative examples. The vertical axis of Fig. 5 represents the residual stress of the aluminum alloy member, and the horizontal axis represents time. In Fig. 5, tensile residual stress is represented as a positive value, and compressive residual stress is represented as a negative value. As shown in Fig. 5, the aluminum alloy member of comparative example 1 had a residual stress of -280 MPa immediately after shot peening (0 hours), which gradually relaxed over time, and the residual stresses at 20 hours and 160 hours were -245 MPa and -200 MPa, respectively. When the first timing was 20 hours and the second timing was 160 hours, the residual stress release rate was 18.3%, which was more than 15%.

[0032] In contrast, the aluminum alloy member of Example 1 had a residual stress of -345 MPa immediately after shot peening, which remained roughly the same over time. The residual stresses at 20 hours and 160 hours were both -330 MPa, and the asymptote (dotted line in Figure 5) was -340 MPa and -325 MPa, respectively. The residual stress release rate was 0% (4.4% when estimated using the asymptote), which was less than 15%. This result confirmed that the aluminum alloy member produced in Example 1 was difficult to release compressive residual stress.

[0033] (Verification of the relationship between shot speed and residual stress maintenance) Example 2 As Example 2, an aluminum alloy member made of an aluminum alloy specified in JIS A7075 was prepared. Next, free-fall shot peening was performed on the aluminum alloy member using a shot peening apparatus 1 shown in FIG. 2. The free-fall height (height difference from the position where the shot starts to fall to the aluminum alloy member) was 1 m. In other words, the speed of the shot when it contacted the aluminum alloy member was 4.4 m / s. For the shot peening, a spherical shot (ZC600 manufactured by Shinto Kogyo Co., Ltd.) with a diameter φ of 0.6 mm to 0.8 mm, made of zirconia, a specific gravity of 6.2, and a Vickers hardness of HV1180 was used.

[0034] Example 3 In Example 3, the free fall height was 2 m, that is, the shot velocity when it contacted the aluminum alloy member was 6.3 m / s. The other conditions were the same as in Example 2.

[0035] (Comparative Example 2) In Comparative Example 2, the free fall height was 3 m, that is, the shot speed when it contacted the aluminum alloy member was 7.7 m / s. The other conditions were the same as in Example 2.

[0036] The changes in residual stress over time were measured for the aluminum alloy members of Examples 2 and 3 and Comparative Example 2. An X-ray residual stress measurement device (μ-X360s manufactured by Pulstec Industrial Co., Ltd.) was used to measure the residual stress. Measurements were carried out multiple times between 0 and 150 hours. The results are shown in Figure 6.

[0037] FIG. 6 is a graph showing the relationship between the residual stress of an aluminum alloy member and elapsed time, obtained for each shot speed. The vertical axis of FIG. 6 represents the residual stress of the aluminum alloy member, and the horizontal axis represents time. In FIG. 6, tensile residual stress is represented as a positive value, and compressive residual stress is represented as a negative value. As shown in FIG. 6, the residual stress of the aluminum alloy member of Comparative Example 2 (7.7 m / s) was −360 MPa immediately after shot peening (0 hours), and gradually relaxed over time. In Comparative Example 2, the rate of change was not stable, so it is expected that the residual stress will further relax over time. The residual stresses estimated from the graph at 20 hours and 160 hours were approximately −350 MPa and approximately −270 MPa, respectively. In other words, a residual stress of approximately −80 MPa was relaxed during the time lapse from the first timing 20 hours after shot peening to the second timing 160 hours after shot peening. The residual stress release rate was 22.8%, which was more than 15%.

[0038] In contrast, the residual stress of the aluminum alloy member of Example 2 (4.4 m / s) was -400 MPa immediately after shot peening, and maintained roughly the same value even after 20 hours had passed, with the residual stresses at 20 hours and 145 hours being -355 MPa and -350 MPa, respectively. When the residual stress at 145 hours was used, the residual stress release rate was 1.4%, and considering the stability of the residual stress after 20 hours, it is expected that the release rate will not change significantly from 1.4%.

[0039] Similarly, the aluminum alloy member of Example 3 (6.3 m / s) had a residual stress of -425 MPa immediately after shot peening, and maintained roughly the same value over time after 20 hours had elapsed, with the residual stresses at 20 hours and 140 hours being -365 MPa and -340 MPa, respectively. When the residual stress at 140 hours was used, the residual stress release rate was 6.8%, and considering the stability of the residual stress after 20 hours, it is expected that the release rate will not change significantly from 6.8%.

[0040] As described above, it was confirmed that the aluminum alloy members produced in Examples 2 and 3 had compressive residual stress that was difficult to release.

[0041] (Verification of maintenance of fatigue strength) The fatigue strength was evaluated for the aluminum alloy member of Example 1 and an untreated aluminum alloy member (Comparative Example 3). The aluminum alloy member of Example 1 was used after 168 hours had elapsed. To evaluate the fatigue strength, repeated stress was applied periodically to the aluminum alloy member, and the stress amplitude σ a The stress amplitude σ a The measurement was performed using a measuring device (MS-CRB-0) manufactured by Waki ​​Co., Ltd. The results are shown in Figure 7.

[0042] 7 is a graph showing the relationship between the stress amplitude and the number of repetitions of the aluminum alloy members in the examples and comparative examples. The vertical axis of FIG. 7 represents the stress amplitude σ a 7, the horizontal axis represents the number of repetitions. a is the stress amplitude σ of Comparative Example 3 a Compared with the aluminum alloy member manufactured in Example 1, the high value was maintained up to several million cycles. From this result, it was confirmed that the aluminum alloy member manufactured in Example 1 maintains its fatigue strength, and that the strength is sufficient for an article to be handled by humans.

[0043] [Forms included in this disclosure] The present disclosure includes the aspects described in the following clauses.

[0044] (Clause 1) A method for manufacturing an aluminum alloy member according to one aspect of the present disclosure includes the steps of preparing an aluminum alloy member made of an aluminum alloy, and shot peening the aluminum alloy member so that the speed of the shot when it contacts the aluminum alloy member is in the range of 1 m / s to 7 m / s, thereby imparting residual stress to the aluminum alloy member.

[0045] According to the manufacturing method described in Clause 1, shot peening is performed on an aluminum alloy member at a shot speed in the range of 1 m / s to 7 m / s when the shot contacts the aluminum alloy member. A shot speed range of 1 m / s to 7 m / s can be achieved without using compressed air. When residual stress is imparted to an aluminum alloy through general cold working, aging relaxation occurs. Residual stress imparted to an aluminum alloy member is released over time, causing the fatigue strength of the aluminum alloy member to decrease over time. The inventors have discovered that special shot peening conditions, in which shots contact the aluminum alloy member at a low speed, contribute to suppressing the decrease in fatigue strength of the aluminum alloy member over time. By using these special shot peening conditions, the manufacturing method described in Clause 1 can appropriately maintain the fatigue strength of the aluminum alloy member. Furthermore, since shot peening can be achieved without using compressed air, a compressor is not required. Therefore, the manufacturing method described in Clause 1 can improve the energy consumption efficiency of factories and contribute to CO2 reduction.

[0046] (Clause 2) In the manufacturing method described in Clause 1, the specific gravity of the shot may be 3.8 or more. It is believed that by using heavy shot with a specific gravity of 3.8 or more, a sufficient shot peening effect can be achieved even at a low speed.

[0047] (Clause 3) In the manufacturing method described in Clause 2, the shots may have a Vickers hardness in the range of HV600 to HV1200. It is believed that by using shots with a specific gravity of 3.8 or more and a Vickers hardness of HV600 to HV1200, a more sufficient shot peening effect can be achieved even at a low speed.

[0048] (Clause 4) In the manufacturing method according to clause 3, the shot may be made of zirconia. The manufacturing method according to clause 4 can appropriately maintain the fatigue strength of the aluminum alloy member by using shot made of zirconia.

[0049] (Clause 5) In the manufacturing method according to any one of clauses 1 to 4, in the step of imparting residual stress, the shot may be allowed to fall freely from above the aluminum alloy part and reach the aluminum alloy part. The manufacturing method according to clause 5 can further improve the energy consumption efficiency of factories and further contribute to CO2 reduction.

[0050] (Clause 6) In the manufacturing method according to any one of Clauses 1 to 5, the shot-peened aluminum alloy member may have a residual stress of 50 MPa to 350 MPa. The manufacturing method according to Clause 6 can impart appropriate fatigue strength to the aluminum alloy member in an article handled by humans.

[0051] (Clause 7) In the manufacturing method described in Clause 6, the residual stress release rate of the aluminum alloy member during the period from a first timing, when a predetermined time has elapsed since shot peening of the aluminum alloy member, to a second timing, may be 15% or less. The residual stress release rate during the period from the first timing, when a predetermined time (T1) has elapsed since completion of a series of operations, to the second timing, when a predetermined time (T2) has elapsed since completion of the series of operations, is expressed as ({(residual stress at the first timing) - (residual stress at the second timing)} ÷ (residual stress at the first timing) × 100). The smaller this value, the smaller the release of residual stress over time, and the more likely it is that an appropriate fatigue strength can be stably maintained. The manufacturing method described in Clause 7 can appropriately maintain the fatigue strength imparted to an aluminum alloy member in an article handled by people.

[0052] (Clause 8) A shot peening apparatus according to another aspect of the present disclosure is a shot peening apparatus for shot peening an aluminum alloy member made of an aluminum alloy, and includes a hopper for storing shot, a pipe member communicating with the hopper and allowing the shot to pass through, and a support member disposed vertically below the lower end of the pipe member and supporting the aluminum alloy member.

[0053] According to the shot peening apparatus described in Clause 8, shots fall freely from a pipe member and collide with an aluminum alloy member supported vertically below the pipe member. The inventors discovered that special shot peening conditions, in which shots contact the aluminum alloy member at low speed, contribute to suppressing deterioration of the fatigue strength of the aluminum alloy member over time. The free-fall type shot peening apparatus described in Clause 5 can appropriately maintain the fatigue strength of the aluminum alloy member. Furthermore, since shot peening can be achieved without using compressed air, a compressor is not required. Therefore, the free-fall type shot peening apparatus described in Clause 8 can improve the energy consumption efficiency of factories and contribute to CO2 reduction. [Explanation of symbols]

[0054] 1, 1A...shot peening device, 2a...support member, 3...hopper, 4...shot, 5, 5A...pipe member, 10...aluminum alloy member.

Claims

1. preparing an aluminum alloy member made of an aluminum alloy; a step of applying shot peening to the aluminum alloy member such that the speed of the shot when contacting the aluminum alloy member is in the range of 1 m / s to 7 m / s, thereby imparting residual stress to the aluminum alloy member; A method for manufacturing an aluminum alloy member, comprising:

2. The method for producing an aluminum alloy member according to claim 1, wherein the shot has a specific gravity of 3.8 or more.

3. 3. The method for manufacturing an aluminum alloy member according to claim 2, wherein the shots have a Vickers hardness in the range of HV600 to HV1200.

4. The method for manufacturing an aluminum alloy member according to claim 3, wherein the shots are made of zirconia.

5. 3. The method for manufacturing an aluminum alloy member according to claim 1, wherein in the step of imparting residual stress, the shot is allowed to fall freely from above the aluminum alloy member until it reaches the aluminum alloy member.

6. 3. The method for producing an aluminum alloy member according to claim 1, wherein the aluminum alloy member subjected to shot peening has a residual stress of 50 MPa to 350 MPa.

7. 7. The method for producing an aluminum alloy member according to claim 6, wherein a residual stress release rate of the aluminum alloy member during a period from a first timing to a second timing, when a predetermined time has elapsed since the aluminum alloy member was subjected to shot peening, is 15% or less.

8. A shot peening apparatus for performing shot peening on an aluminum alloy member made of an aluminum alloy, A hopper for storing shots, a pipe member communicating with the hopper and allowing the shot to pass through; a support member disposed vertically below a lower end of the pipe member and supporting the aluminum alloy member; A shot peening apparatus comprising:

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