JP7472623B2 - Aluminum case and method for manufacturing the aluminum case - Google Patents

Description

The present invention relates to an aluminum case and a method for manufacturing an aluminum case.

In recent years, aluminum cases made from castings of aluminum or its alloys have come into widespread use due to their advantages of being lightweight, non-magnetic, and having good thermal conductivity. Patent Document 1 shows a transmission case (cast case) as an example of such an aluminum case.

The aluminum members that make up the aluminum case are prone to casting defects such as blowholes (hereinafter simply referred to as blowholes) in the thick parts during casting. In the cast case shown in Patent Document 1, a recessed cast-out portion (referred to as a hollowed-out portion in Patent Document 1) is provided in the thick parts of the outer surface of the case to prevent the occurrence of blowholes.

Aluminum cases are sometimes manufactured by joining multiple aluminum members together. Patent Document 2 shows a configuration in which aluminum plate members are joined by friction stir welding.

JP 2005-59082 A Japanese Patent Application Laid-Open No. 10-263852

In the friction stir welding method used to manufacture aluminum cases, two cast aluminum members are butted together and a stirrer is brought into contact with a predetermined width (joint area) including the butted portion, thereby stir-joining the two members. If the joint area is thin, the butted portion opens when the stirrer is brought into contact with the joint area, creating a gap, making it easy for internal defects to occur in the joint area. For this reason, the joint area needs to be configured as a thick-walled portion, but as mentioned above, casting holes are likely to occur in the thick-walled portion. Here, in aluminum cases, through holes are sometimes formed in the joint area for internal ventilation or for inserting members to be housed inside. Such through holes are formed, for example, across two members. When a through hole is formed in the thick-walled portion of the joint area, casting holes may be exposed on the inner surface (machined surface) of the through hole in the aluminum case. In aluminum cases, the through hole may receive a reaction force from the inside, so if a casting hole exists on the inner surface of the through hole, stress concentration occurs in the casting hole, and there is a risk of damage to the area around the through hole.

In view of the above situation, there is a need for an aluminum case and a method for manufacturing the aluminum case that can suppress the formation of blowholes exposed on the inner circumferential surface of the through hole formed in the aluminum case.

The aluminum case according to the present invention is characterized in that it is an aluminum case having a joint where a first member and a second member, which are aluminum alloy members formed by casting, are joined by friction stir welding, and a through hole is formed that spans both the first member and the second member across the joint, and the open end of the through hole is made up of an angular portion and a rounded portion along the circumferential direction.

According to this configuration, the aluminum case is formed by joining the first member and the second member, and the opening end of the through hole that straddles both the first member and the second member across the joint between the two members is composed of a corner portion and a rounded corner portion along the circumferential direction. Here, the corner portion corresponds to a right angle portion formed by the surface around the through hole and the inner peripheral surface of the through hole. Such a corner portion can be formed by processing the through hole with a drill or the like. On the other hand, the rounded corner portion corresponds to a portion in which the corner portion of the opening end of the through hole is rounded in an R shape in the penetrating direction of the through hole. If the first member and the second member are formed by casting, such a rounded corner portion can be formed by a cast-out portion provided during casting, and may remain even after processing the through hole with a drill or the like. If a cast-out portion is formed during casting, the thickness near the cast-out portion becomes thin, and blowholes are less likely to occur. Therefore, if a through hole is formed in the aluminum case at a position close to the cast-out portion, blowholes are less likely to occur near the cast-out portion, so that it is possible to suppress exposure of blowholes on the inner peripheral surface of the through hole. Additionally, the rounded corners of the through holes in the aluminum case can also function as guides when inserting various components into the aluminum case.

As another characteristic configuration, the corner portion is formed in a joining region that spans the first member and the second member across the joint and is joined by the friction stir welding, and the rounded corner portion is formed in a non-joint region that is continuous from the joining region to each of the first member and the second member.

According to this configuration, in the through hole formed in the aluminum case, a corner portion that can be formed by hole processing using a drill or the like is formed in the joining region of the first member and the second member. The joining region is the region where the first member and the second member are joined by friction stir welding, and is the region that is stirred by the rotor during friction stir welding. For this reason, the portion that becomes the joining region in the first member and the second member needs to be made thick to ensure rigidity. Therefore, when casting the first member and the second member, it is not possible to form a cast-out portion in the portion that becomes the joining region by friction stir welding to make it thinner. As a result, the opening end of the through hole formed in the portion that is not the cast-out portion becomes a corner portion. In other words, the corner portion is formed in the joining region. On the other hand, since the non-joining region is a region that is not affected by friction stir welding, it is not necessary to make it thick, and it is possible to provide a cast-out portion in that region. And the opening end of the cast-out portion can be formed with round corners. Therefore, the round corner portion of the opening end of the through hole is a round corner portion formed in the cast-out portion in the non-joining region. In other words, the round corner portion can be formed in the non-joining region. In this way, at the open end of the through hole, the corners are formed in the joint area and the rounded corners are formed in the non-joint area, so that the aluminum case can prevent blowholes from being exposed on the inner surface of the through hole while ensuring the rigidity of the joint.

The manufacturing method of the aluminum case according to the present invention is characterized by the following: a casting process for forming a first member and a second member made of aluminum alloy members and having a cast-out portion by casting; a joining process for abutting the first member and the second member and applying a friction stir rotor to the abutting portion to join the first member and the second member by friction stir welding to form a joint; and a hole forming process for forming a through hole in a location that straddles the first member and the second member across the joint and includes at least a part of each of the cast-out portions, the through hole having a joint region that straddles the first member and the second member across the joint and is joined by the friction stir welding, and a non-joint region that is a region that continues from the joint region to each of the first member and the second member, and the portion of the open end of the through hole that is located in the non-joint region is formed by the cast-out portion.

According to this configuration, an aluminum case having a through hole can be properly manufactured by performing a casting process, a joining process, and a hole forming process on a first member and a second member made of an aluminum alloy member. Here, the through hole is formed in the joining region and the non-jointed region across the first member and the second member, and the portion of the open end of the through hole located in the non-jointed region is formed by the cast-out portion. In other words, the through hole formed in the aluminum case is formed in a region that includes a part of the cast-out portion in the non-jointed region. The first member and the second member are thinner near the cast-out portion, making it difficult for blowholes to occur inside. Therefore, it is possible to suppress the exposure of blowholes on the inner surface of the through hole in the manufactured aluminum case.

Another characteristic feature is that the shape of the inner circumferential surface of the cast-out portion on the side farther from the joint is substantially the same as the shape of the inner circumferential surface of the through hole.

According to this configuration, the shape of the inner peripheral surface of the cast-out portion farther from the joint is substantially the same as the shape of the inner peripheral surface of the through hole, so the through hole can be formed along the inner peripheral surface of the cast-out portion, and the hole forming process can be easily performed. Since the cast-out portion is a portion of the aluminum case where the thickness of the member is thin, the strength of the through hole may decrease if there are many cast-out portions around the through hole. However, with this configuration, by forming the through hole along the inner peripheral surface of the cast-out portion, the cast-out portions of the first member and the second member can be largely removed by the through hole. This makes it possible to reduce the area of the cast-out portion remaining around the through hole in the aluminum case. As a result, it is possible to suppress the decrease in strength of the surrounding area of the through hole in the manufactured aluminum case.

2A and 2B are a perspective view and a plan view of a main portion of an aluminum case. 2 is a cross-sectional view taken along the line II-II of FIG. 1. 3 is a cross-sectional view taken along the line III-III in FIG. 1 . FIG. 2 is a plan view of a main portion of a first member and a second member. 5 is a cross-sectional view taken along the line VV in FIG. 4. 4 is a cross-sectional view of a first member and a second member during the manufacturing process of the aluminum case. FIG. 1 is a plan view of a main portion of a first member and a second member during the manufacturing process of an aluminum case. FIG. 4 is a cross-sectional view of a first member and a second member during the manufacturing process of the aluminum case. FIG. FIG. 11 is a plan view of a main portion of a first member and a second member according to another embodiment. FIG. 11 is a plan view of a main portion of a first member and a second member according to another embodiment. FIG. 11 is a cross-sectional view of a first member and a second member according to another embodiment.

The following describes an aluminum case and a method for manufacturing an aluminum case according to an embodiment of the present invention with reference to the drawings.

1 shows an example of an aluminum case 1. The aluminum case 1 is formed by joining a first member 11 and a second member 12, which are aluminum alloys formed by casting, and are in the shape of a rectangular cylinder with a bottom. As shown in FIG. 1, the aluminum case 1 is formed by joining the first member 11 and the second member 12 at a joint 13 to form an integrated body. The first member 11 and the second member 12 are joined by friction stir welding, and the first member 11 has a processed part A1 that is thicker than the surrounding area, and the second member 12 has a processed part A2 that is thicker than the surrounding area (see FIG. 3). The joint area 14, which is an area friction stir welded by contacting the rotor 3 used for friction stir welding (an example of a rotor for friction stir welding, see FIG. 6), is formed across the processed part A1 and the processed part A2. The processed part A1 of the first member 11 has the joint area 14 and a non-joined area 15, which is an area other than the joint area 14. The processed portion A2 of the second member 12 has a bonding region 14 and a non-bonding region 16, which is the region other than the bonding region 14.

As shown in Figs. 1 to 3, the aluminum case 1 has a through hole 17 formed by processing with a drill or the like (not shown). The through hole 17 is formed across the first member 11 and the second member 12, and from the joint region 14 to the non-joint regions 15 and 16. The opening end 18 of the through hole 17 has a corner portion 23a and rounded corner portions 21a and 22a. The actual inner peripheral surface of the through hole 17 is a processed surface 23 processed with a drill or the like. The processed surface 23 is composed of the corner portion 23a of the opening end 18 and the straight portion 23b continuing from the rounded corner portions 21a and 22a. In this embodiment, the cross section of the through hole 17 is circular. The cross section of the through hole 17 may be circular, such as an ellipse or an oval, or angular, such as a rectangle.

The through hole 17 is provided in the side surface 2 of the aluminum case 1. The corner portions 23a of the opening end 18 of the through hole 17 are formed in two places in the joining region 14 that straddles the first member 11 and the second member 12 across the joining portion 13 and is joined by friction stir welding. The rounded corner portions 21a, 22a of the opening end 18 of the through hole 17 are formed in the non-jointed regions 15, 16 that continue from the joining region 14 to the first member 11 and the second member 12, respectively. In other words, the opening end 18 of the through hole 17 consists of two corner portions 23a and rounded corner portions 21a, 22a along the circumferential direction.

Here, the corner portion 23a corresponds to a right angle portion formed by the upper surface 4 of the processed portion A1, A2 around the through hole 17 in the joining region 14 and the inner peripheral surface (machined surface 23) of the through hole 17. Such corner portion 23a can be formed, for example, by a drill for machining the through hole 17. On the other hand, the rounded corner portions 21a, 22a correspond to the portion where the opening end 18 of the through hole 17 in the non-joining region 15, 16 is rounded in an R shape. If the first member 11 and the second member 12 are aluminum alloy members formed by casting, such rounded corner portions 21a, 22a can be formed by the cast-out portions 21, 22 (see FIG. 3) provided during casting. Here, the cast-out portions 21, 22 are recesses formed in the thickness direction of the processed portions A1, A2 of the first member 11 and the second member 12. By forming the cast-out portions 21, 22, the thickness of the vicinity thereof can be made thin. In addition, by making the shape of the inner peripheral surface 33b, 34b (see FIG. 4) of the inner peripheral surface 33, 34 of the cast-out portions 21, 22, which is farther from the joint portion 13, approximately the same shape as the inner peripheral surface of the through hole 17, the through hole 17 of the aluminum case 1 can be formed in a position close to the cast-out portions 21, 22. Since the vicinity of the cast-out portions 21, 22 is thin, it is difficult for blowholes to occur, and it is possible to prevent blowholes from being exposed on the inner peripheral surface (machined surface 23) of the through hole 17 in the aluminum case 1.

As shown in FIG. 3, the through hole 17 is used when inserting various members 40 into the aluminum case 1 and for ventilation inside the aluminum case 1. In this case, the rounded corners 21a and 22a can function as guides when inserting various members 40 into the aluminum case 1.

In addition, in the aluminum case 1 of this embodiment, the corner portion 23a that can be formed by drilling or the like in the through hole 17 is formed in the joining region 14 of the first member 11 and the second member 12. The joining region 14 is the region where the first member 11 and the second member 12 are joined by friction stir welding, and is the region that is stirred by the rotor 3 (see FIG. 6) during friction stir welding. For this reason, the portion that becomes the joining region 14 in the first member 11 and the second member 12 needs to be thick to ensure rigidity. Therefore, when casting the first member 11 and the second member 12, the portion that becomes the joining region 14 by friction stir welding cannot be thinned by forming the cast-out portions 21, 22. As a result, the opening end 18 of the through hole 17 formed in the portion that is not the cast-out portion 21, 22 becomes the corner portion 23a. In other words, the corner portion 23a is formed in the joining region 14. On the other hand, the non-bonded regions 15, 16 continuing from the bonding region 14 to the first member 11 and the second member 12, respectively, are not affected by the friction stir welding, so there is no need to make them thick, and it is possible to provide the cast-out portions 21, 22 in the regions. The open ends 18A of the cast-out portions 21, 22 can be formed with rounded corners 21aA, 22aA (see Figs. 5, 6, and 8). Therefore, the rounded corners 21a, 22a of the open ends 18 of the through holes 17 are part of the rounded corners 21aA, 22aA formed in the cast-out portions 21, 22 in the non-bonded regions 15, 16. That is, the rounded corners 21a, 22a are the portions after the rounded corners 21aA, 22aA are machined by a drill or the like in the hole forming process described later. In this way, at the opening end 18 of the through hole 17, the corner portion 23a is formed in the joint area 14, and the rounded corner portions 21a, 22a are formed in the non-joint areas 15, 16, so that the aluminum case 1 can prevent the exposure of blowholes on the inner surface (machined surface 23) of the through hole 17 while ensuring the rigidity of the joint 13.

The manufacturing method of the aluminum case 1 will be described below with reference to Figures 4 to 8. The manufacturing method of the aluminum case 1 includes a casting process, a joining process, and a hole forming process.

[Casting process]
In the casting process, the first member 11, which is made of an aluminum alloy member and has a cast-out portion 21, and the second member 12, which has a cast-out portion 22, are formed by casting. As shown in Figs. 4 and 5, the cast-out portion 21 is formed in the processed portion A1 of the first member 11, and the cast-out portion 22 is formed in the processed portion A2 of the second member 12 by the casting process. The cast-out portions 21, 22 are formed as recesses extending from the upper surfaces 4 of the first member 11 and the second member 12 in the thickness direction. Rounded corners 21aA, 22aA are formed around the entire circumference of the opening ends 18A of the cast-out portions 21, 22, respectively. The rounded corners 21aA, 22aA are portions that are rounded from the upper surface 4 toward the bottoms 31, 32 of the cast-out portions 21, 22 at the opening ends 18A of the cast-out portions 21, 22. A part of the rounded corners 21 aA, 22 aA formed at the opening end 18 A of the cast-out portions 21, 22 becomes the rounded corners 21 a, 22 a of the opening end 18 of the through hole 17.

The cast-out portions 21 and 22 are symmetrical with respect to the abutment portion B where the first member 11 and the second member 12 are abutted, and have the arched portions 21b and 22b and the extension portions 21c and 22c formed on both sides of the arched portions 21b and 22b. The extension portions 21c and 22c are formed by extending only the arc portions from the arched portions 21b and 22b. The arched portion 21b of the first member 11 and the arched portion 22b of the second member 12 are evenly spaced from the abutment portion B, and the distance W3 between them is greater than the width W1 of the joining area 14. On the other hand, the distance W2 between the extension portions 21c and 22c is set to be approximately the same as the width W1 of the joining area 14. In other words, the cast-out portions 21 and 22 are provided with the extension portions 21c so that the distance W2 between them is approximately the same as the width W1 of the joining area 14.

As shown in Figures 4 and 5, the cast-out portions 21, 22 are provided along the abutment portion B (joint 13 after joining), and the inner circumferential surfaces 33, 34 include inner circumferential surfaces 33a, 34a on the side closer to the abutment portion B (joint 13 after friction stir welding) and inner circumferential surfaces 33b, 34b on the side farther from the abutment portion B (joint 13 after joining). Here, the inner circumferential surfaces 33b, 34b are formed in approximately the same shape (an arc shape with approximately the same radius as the radius of the through hole 17) as the shape of the inner circumferential surface of the through hole 17 (two-dot chain line) formed in the subsequent hole forming process.

In the vicinity of the inner circumferential surface (machined surface 23) of the through hole 17, if a blow hole is exposed from the inner circumferential surface, stress concentration occurs in the blow hole, which may damage the area around the through hole 17, so it is preferable to make the wall thin, and therefore the cast-out portions 21 and 22 are formed. However, if the wall is thin near the abutment portion B, when the rotor 3 is brought into contact with the abutment portion B, the abutment portion B opens, creating a gap, and an internal defect occurs in the joint portion 13, so it is preferable to make the wall thick. In order to solve this conflicting problem, the cast-out portions 21 and 22 are composed of the arched portions 21b and 22b and the extended portions 21c and 22c. That is, since the inner circumferential surfaces 33b and 34b are near the inner circumferential surface of the through hole 17, the extended portions 21c and 22c are provided to make the wall thin, forming a thin wall portion up to the distance W2 near the abutment portion B. On the other hand, the inner circumferential surfaces 33a and 34a are removed by machining the through hole 17, so there is no problem even if there is a blow hole in the vicinity. Therefore, the distance between the inner circumferential surfaces 33a and 34a is set to W3, which is thicker than the distance W2 in the plan view shown in Figure 4. This makes it possible to prevent the abutting portion B from opening and creating a gap even in the joining process by friction stir welding described below.

[Joining process]
Next, in the joining process, the first member 11 and the second member 12 are joined. In the joining process, friction stir welding is used. In the friction stir welding, a rotor 3 including a probe 3a made of a material harder than the workpieces (the first member 11 and the second member 12) is rotated and brought into sliding contact with the workpieces, thereby joining the butted portions (abutment portion B) of the workpieces.

As shown in FIG. 6, the probe 3a protruding from the axis of the rotating rotor 3 is pressed against the abutment portion B of the butted first member 11 and second member 12, and the rotor 3 is moved in this pressed state along the extension direction of the abutment portion B (the longitudinal direction in FIG. 4). As a result, the probe 3a is embedded in the abutment portion B and proceeds along the abutment portion B while remaining embedded. The aluminum alloy, which is the material of the first member 11 and the second member 12, is stirred and kneaded in the portion through which the probe 3a passes, and hardens in a completely integrated state. Therefore, when the probe 3a is released from the other end side of the abutment portion B, the first member 11 and the second member 12 are joined together to form an integrated body.

In friction stir welding, the aluminum alloy, which is the material of the first member 11 and the second member 12, becomes plasticized by frictional heat in the joint area 14 at the front side in the direction of travel of the probe 3a, and while being stirred and kneaded, it gradually moves to the rear side in the direction of travel of the probe 3a, where it loses the frictional heat and rapidly cools and solidifies.

At the abutment portion B, only the areas where the extensions 21c, 22c of the cast-out portions 21, 22 are formed are thin-walled by a distance W2 in the plan view shown in Figure 4, but this is an extremely small area compared to the entire abutment portion B, and other areas are thick-walled, so even if the rotor 3 is pressed against it, the abutment portion B can be prevented from opening and creating a gap.

[Hole forming process]
Next, in the hole forming process, a through hole 17 is formed at a location that straddles the first member 11 and the second member 12 across the joint 13 and includes at least a part of each of the cast-out portions 21, 22. Specifically, as shown in Figs. 7 and 8, a through hole 17 (see Fig. 8) indicated by a two-dot chain line is formed in the first member 11 and the second member 12 that are joined with a joint trace 14a formed in the joint region 14. The through hole 17 is formed by processing such as a drill. As shown in Fig. 8, the through hole 17 (two-dot chain line) is formed by leaving a part of the rounded corners 21aA, 22aA at the opening end 18A in the cast-out portions 21, 22. In Fig. 8, the radius of the through hole 17 is slightly larger than the radius of the inner peripheral surfaces 33b, 34b, but the radius of the inner peripheral surfaces 33b, 34b may be the same as the radius of the through hole 17.

As described above, the aluminum case 1 (see FIG. 1) having the through hole 17 can be properly manufactured by performing the casting process, the joining process, and the hole forming process on the first member 11 and the second member 12 made of aluminum alloy members. Here, the through hole 17 is formed across the first member 11 and the second member 12 in the joining region 14 and the non-jointed regions 15, 16, and the portion of the opening end 18 of the through hole 17 located in the non-jointed regions 15, 16 is formed by the cast-out portions 21, 22. That is, the through hole 17 formed in the aluminum case 1 is formed in the region including a part of the cast-out portions 21, 22 in the non-jointed regions 15, 16. The first member 11 and the second member 12 are thin near the cast-out portions 21, 22, making it difficult for blowholes to occur inside. Therefore, it is possible to suppress the exposure of blowholes on the inner peripheral surface (machined surface 23) of the through hole 17.

Furthermore, in this embodiment, the inner circumferential surfaces 33b, 34b of the cast-out portions 21, 22 are formed in a shape (arc-shaped with a radius approximately the same as that of the through hole 17) that is substantially the same as the shape of the inner circumferential surface of the through hole 17 formed in the hole forming process. Therefore, in the hole forming process, the through hole 17 can be formed along the inner circumferential surfaces 33b, 34b of the cast-out portions 21, 22, and the through hole 17 can be formed. Since the cast-out portions 21, 22 are the parts of the aluminum case 1 where the thickness of the member is thin, if there are many cast-out portions 21, 22 around the through hole 17, the strength of the parts around the through hole 17 in the aluminum case 1 may decrease. However, with this configuration, by forming the through hole 17 along the inner circumferential surfaces 33b, 34b of the cast-out portions 21, 22, the cast-out portions 21, 22 of the first member 11 and the second member 12 can be largely removed from the aluminum case 1 by the through hole 17. This makes it possible to reduce the area of the cast-out portions 21, 22 remaining around the through hole 17 in the aluminum case 1. As a result, it is possible to suppress a decrease in strength of the area around the through hole 17 in the aluminum case 1 after manufacturing.

[Another embodiment]
(1) In the above embodiment, the cut-out portions 21, 22 formed in the first member 11 and the second member 12 are configured by the arch-shaped portion 21b and the extension portion 21c. As shown in FIG. 9, the cut-out portions 21, 22 may each be arch-shaped. In the example shown in FIG. 9, the distance W2 between the cut-out portion 21 and the cut-out portion 22 is constant in the direction along the abutting portion B and is equal to the width W1 of the joining region 14. As shown in FIG. 10, the cut-out portions 21, 22 may each be arc-shaped. In the example shown in FIG. 10, the distance W2 between both ends of the arc-shaped cut-out portion 21 of the first member 11 and both ends of the cut-out portion 22 of the second member 12 facing the cut-out portion 21 is equal to the width W1 of the joining region 14. 9 and 10 , the shape of the inner circumferential surfaces 33b, 34b of the inner circumferential surfaces 33, 34 of the cut-out portions 21, 22 on the side farther from the joint 13 is substantially the same as the shape of the inner circumferential surface of the through hole 17. Although not shown, the inner circumferential surfaces 33a, 34a of the cut-out portions 21, 22 on the side closer to the joint 13 may be configured with a recess in the central portion of the inner circumferential surfaces 33a, 34a facing the joint 13 so that the central portion is close to the joint 13 in addition to both ends of the arc portion shown in FIG.

(2) In the above embodiment, as shown in FIG. 5, an example was shown in which the cut-out portions 21, 22 are formed only on the front side (side surface 2 side) of the aluminum case 1 (first member 11 and second member 12). However, as shown in FIG. 11, the cut-out portions 21, 22 may be provided on both sides of the first member 11 and second member 12. In addition, although not shown, the cut-out portions 21, 22 may be formed only on the back side (opposite side surface 2) of the first member 11 and second member 12.

The present invention can be widely used in aluminum cases and methods for manufacturing aluminum cases.

1: Aluminum case 2: Side surface 11: First member 12: Second member 13: Joint portion 14: Joint region 15, 16: Non-joint region 17: Through hole 18: Opening end 21, 22: Cast-out portion 21a, 22a: Rounded corner portion 23: Machined surface (inner peripheral surface)
23a: Corner portion 23b: Straight portion 33, 34: Inner peripheral surface A1, A2: Processing portion B: Contact portion W1: Width of joining area W2: Distance between two cast-out portions

Claims (3)

An aluminum case having a joint formed by friction stir welding of a first member and a second member, the first member and the second member being aluminum alloy members formed by casting, and a through hole formed in the first member and the second member across the joint,
The aluminum case has an opening end of the through hole that has a corner portion and a rounded corner portion along the circumferential direction. The corner portion is formed in a joining region that spans the first member and the second member across the joint and is joined by the friction stir welding,
The aluminum case according to claim 1 , wherein the rounded corners are formed in non-bonded regions that are continuous from the bonded region to each of the first member and the second member. a casting step of forming a first member and a second member, each of which is made of an aluminum alloy member and has a cast-out portion, by casting;
a joining process in which the first member and the second member are brought into contact with each other and a friction stir rotor is applied to the contacting portion to join the first member and the second member by friction stir welding to form a welded portion;
a hole forming step of forming a through hole at a location that straddles the first member and the second member across the joint portion and includes at least a part of each of the cast-out portions,
The through hole has a joint region that spans the first member and the second member across the joint and is joined by the friction stir welding, and a non-joint region that is a region continuous from the joint region to each of the first member and the second member,
A manufacturing method for an aluminum case, wherein the portion of the open end of the through hole located in the non-jointed region is formed by the cast-out portion.

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