Welding method of aluminum alloy, and aluminum molding

Abstract

To provide a welding method of aluminum alloys in which cracking hardly occurs, and an aluminum molding.SOLUTION: A welding method of aluminum alloys includes: a preparation step for preparing a pair of laminates 14 obtained by laminating an Al-Si-Mg-based alloy 11 and an Al-Si-based alloy 12; and a welding step for welding a pair of laminates 14A, 14B by arranging the pair of laminates 14A, 14B so that layers of the Al-Si-based alloys 12,12 face each other, and then, radiating laser from a side of the Al-Si-Mg-based alloy 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for welding aluminum alloys and aluminum formed products. [Background technology]

[0002] In electric vehicles, aluminum alloys are sometimes used for battery cases, for example. Aluminum alloys have high strength, excellent laser weldability, and are suitable for thinning, making them suitable for use as secondary battery cases (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-293059 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a growing need to select high-strength 6000-series aluminum materials in order to reduce the thickness of aluminum alloy plates in aluminum formed products and reduce the cost of aluminum materials. However, in such cases, solidification cracking occurs during the solidification process of the weld when the aluminum alloy is laser welded. Solidification cracking occurs for two reasons: the wide temperature range in which the solid and liquid phases coexist during the process from melting to solidification, and the large residual stress from the weld.

[0005] Therefore, there is a need for a simple method for welding aluminum alloys that is less likely to cause solidification cracking during laser welding, and for an aluminum formed product. [Means for solving the problem]

[0006] The method for welding aluminum alloys according to the present invention is characterized in that it comprises a preparation step of preparing a pair of laminates each having an Al-Si-Mg alloy and an Al-Si alloy stacked together, and a welding step of arranging the pair of laminates so that the Al-Si alloy layers face each other and irradiating a laser from the Al-Si-Mg alloy side to weld the pair of laminates together.

[0007] By including the above-described preparation process and welding process in the aluminum alloy welding method, the aluminum alloy is welded with the Al-Si alloy disposed on the inner side. Here, the Al-Si alloy has a higher Si content than the Al-Si-Mg alloy. This narrows the temperature range in which the solid and liquid phases coexist during the solidification process of the weld. As a result, the aluminum alloy can suppress cracking in the welded portion by laser welding. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing an outline of an aluminum alloy to be welded. [Figure 2] 1 is a table showing an example of the composition of an aluminum alloy. [Figure 3] FIG. 1 is a plan view of an aluminum alloy in a welded state. [Figure 4] 10A and 10B are diagrams illustrating a welding process at the end portion. [Figure 5] FIG. 10 is a cross-sectional view of a termination welded without wire feed. [Figure 6] FIG. 10 is a cross-sectional view of a termination welded while feeding a wire. [Figure 7] 1A and 1B are cross-sectional views of a welded area at different welding speeds. [Figure 8] 1 is a graph showing the relationship between melting speed and the amount of warpage of a product. [Figure 9] 1 is a graph showing the relationship between the plate thickness of an Al—Si alloy and the number of cracks in the fusion zone when the welding speed is 15 m / min. [Figure 10]1 is a graph showing the relationship between the plate thickness of an Al—Si alloy and the number of cracks in a fusion zone when the welding speed is 10 m / min. [Figure 11] FIG. 10 is a diagram showing a welding state using a single laser. [Figure 12] FIG. 10 is a diagram showing a welding state using a multi-spot laser. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes a method for welding aluminum alloys and an aluminum formed product manufactured by the method. However, the method for welding aluminum alloys and the aluminum formed product are not limited to the following embodiments, and various modifications are possible without departing from the spirit and scope of the invention.

[0010] [First embodiment] The embodiment will be described in the order of a method for welding aluminum alloys and an aluminum formed product.

[0011] [Welding method for aluminum alloys] A welding method for an aluminum alloy 10 according to an embodiment will be described with reference to FIG. The welding method for aluminum alloy 10 according to the embodiment includes a preparation step of preparing a pair of laminates 14 each having an Al-Si-Mg alloy 11 and an Al-Si alloy 12 stacked thereon, and a welding step of arranging the pair of laminates 14A, 14B so that the layers of the Al-Si alloy 12, 12 face each other, and irradiating a laser from the Al-Si-Mg alloy 11 side of one of the laminates 14A to weld the pair of laminates 14A, 14B together.

[0012] The welding method for the aluminum alloy 10 is characterized in that a plurality of Al alloys 11, 12 having a specific composition are prepared in the preparation step, and that a laser is irradiated from the side of the Al-Si-Mg alloy 11 in the welding step.

[0013] Each step will be described in detail. In the following explanation, the side irradiated with the laser is referred to as the front (upper side of the paper in FIG. 1), and the opposite side is referred to as the back (lower side of the paper in FIG. 1), with the front-to-back direction being the thickness direction.

[0014] [Preparation process] In the preparation step, an Al-Si-Mg alloy 11 and an Al-Si alloy 12 are prepared as Al alloys 11, 12 having specific compositions that constitute the aluminum alloy 10. Next, the Al-Si-Mg alloy 11 and the Al-Si alloy 12 are stacked to form a laminate 14, and a pair of such laminates 14 are prepared. In this embodiment, the laminate 14 is formed by stacking an Al alloy 13 on one of both surfaces of the Al-Si-Mg alloy 11, the surface opposite to the Al-Si alloy 12. The Al alloy 13 is used as a sacrificial layer that exhibits sacrificial corrosion protection.

[0015] Here, the Al alloy is an alloy mainly composed of Al (aluminum) and containing additional elements such as Si (silicon), Fe (iron), Cu (copper), Mn (manganese), and Mg (magnesium). The table shown in FIG. 2 shows examples of the compositions of the Al-Si-Mg alloy 11 and the Al-Si alloy 12. The Al-Si-Mg alloy 11 is, for example, a 6000-series aluminum alloy containing a large amount of Si (silicon) and Mg (magnesium). The Al-Si alloy 12 is, for example, a 4000-series aluminum alloy containing a large amount of Si (silicon). The Al alloy 13 used as the sacrificial layer is, for example, a 7000-series aluminum alloy containing a large amount of Zn (zinc) and Mg (magnesium).

[0016] In the laminate 14, for example, the thickness W1 of the Al-Si-Mg alloy 11 is set to 60 to 70% of the total thickness, the thickness W2 of the Al-Si alloy 12 is set to 30 to 20%, and the thickness W3 of the Al alloy 13 is set to approximately 10%.

[0017] [Welding process] In the welding process, the pair of laminates 14A, 14B are welded together. This welding is performed by arranging the Al-Si alloy layers 12, 12 facing each other and irradiating a laser from the side of the Al-Si-Mg alloy 11, as shown in Fig. 1. As a result, the constituent materials of the pair of laminates 14, 14 are melted and solidified, and the aluminum molded product 1 is produced.

[0018] By irradiating the laser, one laminate 14A is melted across both the front and back of the laser irradiated area, and the other laminate 14B is melted at least in part at a location facing the melted area of ​​the one laminate 14A. Depending on the laser irradiation conditions, the other laminate 14B is melted across both the front and back, similar to the one laminate 14A.

[0019] Any type of laser may be used as long as it can melt and weld the pair of laminates 14A and 14B. Examples of the type of laser include solid-state lasers in which the laser medium is solid, and are selected from, for example, fiber lasers, YAG lasers, YVO4 lasers, etc.

[0020] The laser irradiation conditions can be appropriately selected depending on the thickness of the pair of laminates 14A, 14B, etc. The laser scanning speed (welding speed) can be 10 mm / sec or more. By setting the laser scanning speed to 10 mm / sec or more, the scanning speed is not too slow and the welding time of the pair of laminates 14A, 14B is not too long, thereby improving productivity. The laser scanning speed is preferably 90 mm / sec or less. If the laser scanning speed is 90 mm / sec or less, the scanning speed is not too fast and the surface of the other laminate 14B can be melted. The laser scanning speed is preferably 15 mm / sec or more and 60 mm / sec or less, and more preferably 20 mm / sec or more and 30 mm / sec or less. The laser scanning direction can be appropriately selected, and here it is set to the direction perpendicular to the plane of the paper in FIG. 1.

[0021] [Welded parts of aluminum molded products] The pair of laminates 14A, 14B are welded together by a laser to produce an aluminum formed product 1. As shown in Fig. 3, in the aluminum formed product 1, laser welding is performed, for example, in a linear manner, and a welded region 20 includes a general portion 21 and a terminal portion 22. The general portion 21 is the portion where a normal weld bead exists, and the terminal portion 22 is the final portion (end) of the weld bead.

[0022] A depression may be formed in the terminal end portion 22 shown in Fig. 3, and in that case, the central portion of the terminal end portion 22A is recessed from the surface portion 2A of the aluminum formed product 1A, as shown in Fig. 5. This may cause a crack 25 to occur in the terminal end portion 22A due to the effect of tensile stress.

[0023] Therefore, in the welding step of this embodiment, wire welding using a welding wire 42 is also used at the end portion 22 of the linear welded portion 20 by the laser.

[0024] Specifically, as shown in Fig. 4, welding wire 42 is supplied from wire supply unit 41 to terminal end 22, which has been welded in the direction of arrow A by gas supply unit 31 and laser 32. In this way, as shown in Fig. 6, central portion 23 of terminal end 22 protrudes beyond surface portion 2 of aluminum formed product 1. This prevents terminal end 22 from being affected by tensile stress, thereby suppressing the occurrence of cracks.

[0025] [Test Example 1] [Test piece 1] The thickness of the Al-Si-Mg alloy 11 was set to 0.9 mm, and the thickness of the Al alloy 13 was set to 0.1 mm, and the specimen 1 (a pair of laminates 14A and 14B) was prepared in the form of a plate measuring 1200 mm x 300 mm. Note that the Al-Si alloy 12 was not used in the specimen 1.

[0026] The welding speed for test piece 1 was changed in order from 5, 10, 15, and 20 m / min, and the amount of warpage of the product was measured. The test results are shown in Figures 7 and 8. Figure 7 is a cross-sectional view (left) of the welded portion 20 of test piece 1 when the welding speed was 5 m / min, and a cross-sectional view (right) of the welded portion 20 of test piece 1 when the welding speed was 15 m / min. Figure 8 is a graph showing the relationship between the welding speed and the amount of warpage of aluminum formed product 1 (aluminum product).

[0027] As can be seen from the left diagram in Figure 7, when the welding speed is 5 m / min, the welding of the test piece 1 is thermal conduction welding, resulting in a large temperature difference between the upper and lower laminates 14A and 14B. As a result, the amount of warpage (3.5 mm) of the aluminum molded product 1 at a welding speed of 5 m / min is large (see Figure 8). On the other hand, as can be seen from the right diagram in Figure 7, when the welding speed is 15 m / min, a deep keyhole is formed, resulting in a small temperature difference between the upper and lower laminates 14A and 14B. As a result, the amount of warpage of the product at a welding speed of 5 m / min is small (approximately 1.0 mm) (see Figure 8). Here, in the case of an aluminum molded product 1 formed as a 1200 x 300 mm square plate, it is considered preferable that the allowable amount of warpage be within 1.4 mm. Therefore, from the test results shown in Figure 8, it can be understood that when laser welding an aluminum alloy (laminated bodies 14A, 14B), if the welding speed is 10 m / min or more, the amount of warping of the aluminum molded product 1 will be within the allowable range.

[0028] [Test Example 2] [Test piece 2] A plurality of specimens 2 (a pair of laminates 14A, 14B) with different thicknesses of the Al-Si alloy 12 were prepared. The thickness of the Al-Si alloy 12 ranged from 0 to 0.5 mm. The specimen 2 was a plate-like specimen measuring 1200 x 300 mm, the same as the specimen 1. In the specimen 2, the thickness of the Al-Si-Mg alloy 11 was fixed at 0.8 mm. The specimen 2 did not use an Al alloy 13.

[0029] For the above test specimen 2, the occurrence of cracks in the general portion 21 and the terminal end portion 22 was examined with the welding speeds of 15 m / min and 10 m / min and the thickness of the Al-Si alloy 12 varied.

[0030] As shown in Figure 9, when the welding speed was 15 m / min, when the plate thickness of the Al-Si alloy 12 in the test specimen 2 was 0.1 mm or more and 0.2 mm or less, the number of cracks in the general portion 21 was significantly reduced from around 5 to nearly 0 (zero). On the other hand, when the plate thickness of the Al-Si alloy 12 in the test specimen 2 was 0.225 mm (plate thickness T1) or more, no cracks occurred in the general portion 21. Regarding the end portion 22, when the plate thickness of the Al-Si alloy 12 in the test specimen 2 was 0.2 mm or less, the number of cracks occurred to 10 or more.

[0031] As shown in Figure 10, when the welding speed was 10 m / min, there were few cracks overall in the general portion 21, and when the plate thickness of the Al-Si alloy 12 in the test specimen 2 was 0.135 mm (plate thickness T2) or more, no cracks occurred in the general portion 21. In the end portion 22, there were generally less than 10 cracks, and a tendency was observed in which the number of cracks gradually decreased as the plate thickness of the Al-Si alloy 12 in the test specimen 2 increased.

[0032] 9 and 10, it can be seen that for the general portion 21 of the welded portion 20, a welding speed of 10 m / min or more is preferable, and a welding speed of 15 m / min or more is more preferable. On the other hand, it can be seen that for the terminal end portion 22 of the welded portion 20, a welding speed of less than 10 m / min is preferable.

[0033] Other Embodiments The laser 32 used in the method for welding aluminum alloys may be a single laser 32 as shown in FIG. 11, or multiple lasers 32 (four lasers in FIG. 12) as shown in FIG. 12. However, when welding aluminum alloys using a single laser 32 as shown in FIG. 11, it is necessary to move the single laser 32 left and right in the welding direction perpendicular to the laser 32. Therefore, in this case, blowholes P may occur in the welded area 20. On the other hand, when welding aluminum alloys using, for example, four lasers 32 as shown in FIG. 12, the four lasers 32 can be advanced straight in the welding direction perpendicular to the laser 32. Therefore, in this case, blowholes P are less likely to occur in the welded area 20. In view of these factors, it is preferable to use multiple lasers 32 when welding aluminum alloys.

[0034] [Summary of the above embodiment] In the above-described embodiment of the aluminum alloy welding method and aluminum formed product, the following configurations are envisioned.

[0035] (1) A method for welding aluminum alloys, comprising a preparation step of preparing a pair of laminates 14 each made by stacking an Al-Si-Mg alloy 11 and an Al-Si alloy 12, and a welding step of arranging the pair of laminates 14A, 14B so that the layers of the Al-Si alloys 12, 12 face each other, and irradiating a laser 32 from the side of the Al-Si-Mg alloy 11 to weld the pair of laminates 14A, 14B together.

[0036] The aluminum alloy welding method includes the above-mentioned preparation process and welding process, and thus the aluminum alloy 10 is welded with the Al-Si alloy 12 disposed inside. The Al-Si alloy 12 has a higher Si content than the Al-Si-Mg alloy 11. This narrows the temperature range in which the solid and liquid phases coexist during the solidification process of the welded portion 20. As a result, the aluminum alloy 10 can suppress cracking of the welded portion 20 welded by the laser 32.

[0037] (2) In the method for welding an aluminum alloy described in (1), the welding step preferably also includes wire welding using a welding wire 42 at the end 22 of the linear welded portion 20 formed by the laser 32.

[0038] In the linear welded portion 20 formed in the aluminum alloy by the laser 32, it is necessary to stop the laser irradiation at the terminal end 22. For this reason, a depression may be formed in the terminal end 22 due to the laser irradiation, and in this case, the central portion of the terminal end 22 is recessed from the surface portion 2 of the aluminum molded product 1, and therefore the terminal end 22 may be subjected to tensile stress and crack.

[0039] Therefore, in the welding method of this embodiment, wire welding using a welding wire 42 is also used in the welding step at the terminal end portion 22. In this way, even if a depression is formed in the terminal end portion 22 by laser irradiation, the depression can be filled with the welding wire 42. This makes it possible to easily eliminate the depression in the terminal end portion 22 and effectively suppress cracking in the terminal end portion 22.

[0040] (3) In the method for welding an aluminum alloy described in (1) or (2), the welding process is preferably set so that the welding speed by the laser 32 is 10 m / min or more at the linear welded portion 20 except for the terminal end 22, and the welding speed at the terminal end 22 is less than 10 m / min.

[0041] In the method for welding aluminum alloys, reducing the welding speed by the laser 32 reduces the tensile residual stress generated in the welded portion 20, but also increases the amount of warpage of the aluminum formed product 1 caused by laser welding. Therefore, in this embodiment, in the welding process, the laser welding speed is 10 m / min or more at the linear welded portion 20 by the laser 32 except for the terminal end 22. In this way, the welding speed by the laser 32 is a predetermined value or higher, and therefore the amount of warpage of the surface portion 2 of the aluminum formed product 1 caused by laser welding can be reduced.

[0042] (4) The aluminum formed product (1) is formed using the method for welding aluminum alloys according to any one of (1) to (3).

[0043] With the above-described characteristic configuration, it is possible to easily form the aluminum formed product 1 in which cracks at the welded portion 20 are appropriately suppressed by laser welding. [Industrial Applicability]

[0044] The technology disclosed herein can be widely used in aluminum alloy welding methods and aluminum formed products. [Explanation of symbols]

[0045] 1: aluminum molded product (aluminum product), 11: Al-Si-Mg alloy, 12: Al-Si alloy, 14, 14A, 14B: laminate, 20: welding part, 22: end part, 31: gas supply part, 32: laser, 41: wire supply part, 42: welding wire

Claims

1. A method for welding aluminum alloys, comprising the steps of: a preparation step of preparing a pair of laminates each including an Al—Si—Mg alloy and an Al—Si alloy; and a welding step of placing the pair of laminates so that the Al-Si-based alloy layers face each other, and irradiating a laser from the Al-Si-Mg-based alloy side to weld the pair of laminates.

2. 2. The method for welding an aluminum alloy according to claim 1, wherein the welding step additionally uses wire welding using a welding wire at an end portion of the linear welded portion by the laser.

3. 2. The method for welding an aluminum alloy according to claim 1, wherein the welding step is set so that the welding speed by the laser is 10 m / min or more at a portion of the linear welded portion other than the terminal end, and the welding speed at the terminal end is less than 10 m / min.

4. An aluminum formed product formed using the aluminum alloy welding method according to any one of claims 1 to 3.

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