A friction stir welding method for a thick copper plate and a multi-layer copper foil

Abstract

The present invention discloses a friction stir welding method for a thick copper plate and multiple layers of copper foils, which includes step S1: stacking multiple layers of thin copper foils into a copper foil body, then placing copper plates on the upper and lower layers of the copper foil body to obtain a first sample piece, and then placing an arc starting plate and an arc ending plate on both sides of the first sample piece, and performing a first pass of welding using a friction stir welding device; step S2: removing the arc starting plate and the arc ending plate, and then cutting the first sample piece along the middle of the weld seam to obtain two second sample pieces; step S3: turning the bottom end surface of one of the second sample pieces upwards, then butt-welding the thick copper plate with the weld seam of the second sample piece, placing copper plates on both the upper and lower layers of the thick copper plate to obtain a workpiece to be welded, placing the arc starting plate and the arc ending plate on both sides of the workpiece to be welded, and performing a second pass of welding using a friction stir welding device; step S4: removing the arc starting plate, the arc ending plate and the copper plates to obtain a friction stir welded joint of the thick copper plate and multiple layers of copper foils. This method has good welding performance, small deformation, no smoke and dust, and is green and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive metal welding, and more specifically, to a friction stir welding method for a thick copper plate and multiple layers of copper foil. Background Art

[0002] Copper has many excellent properties such as high thermal conductivity and electrical conductivity. It is a common metal in the power field and is the most commonly used material in electronic components and cables. In complete sets of electrical equipment such as high-power motors, high- and low-voltage switchgear cabinets, joints formed by connecting copper plates and copper foils are widely used. Copper plates and copper foils are usually connected by brazing. With the development of industry and the improvement of people's material living standards, the electricity consumption in industry and life has increased sharply, and the load borne by metal joints in the conductive system has increased greatly, resulting in overheating of the joints. In addition, due to its good flexibility and soft texture, copper foil is extremely easy to deform under the high temperature of welding. Coupled with the many defects, low strength, and poor stability of brazed joints, it will greatly affect the stability of the power transmission process. Therefore, further requirements need to be put forward for the connection performance of conductive metals.

[0003] Friction stir welding is a new type of solid-state connection process. It hardly generates soot during the welding process and is a green and environmentally friendly welding technology. Its working principle is that through the low heat input generated by the friction between the stirring head and the workpiece to be welded, the workpiece to be welded reaches the plasticized state, and then under the action of pressure and the stirring head, the plastic materials are extruded and mixed with each other to form a dense joint. The joints obtained by this method have the advantages of fine microstructure, high strength, and few defects. At present, friction stir welding technology is mostly used for welding alloy plates, and it has not been seen that it is applied to the connection between thick copper plates and copper foil sheets.

[0004] Therefore, how to provide a friction stir welding method for a thick copper plate and multiple layers of copper foil with good joint welding performance, small welding deformation, no smoke and dust, and green and environmentally friendly production is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a friction stir welding method for a thick copper plate and multiple layers of copper foil with good joint welding performance, small welding deformation, no smoke and dust, and green and environmentally friendly production.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A friction stir welding method for a thick copper plate and multiple layers of copper foil, comprising the following welding steps:

[0008] Step S1: Stack multiple layers of thin copper foils into a copper foil body, then place copper plates on both the upper and lower layers of the copper foil body to obtain a first sample piece. Then, place an arc starting plate and an arc ending plate on both sides of the first sample piece, and use a welding fixture to fix the arc starting plate, the arc ending plate, and the first sample piece. Finally, perform a single-pass weld on the arc starting plate, the first sample piece, and the arc ending plate using a friction stir welding device.

[0009] Step S2: After the single-pass weld is completed, remove the arc starting plate and the arc ending plate, and then cut the first sample piece along the middle of the weld seam of the single-pass weld to obtain two second sample pieces.

[0010] Step S3: Place one of the second sample pieces with its bottom end face facing up, then butt one side of a thick copper plate against the weld seam of the second sample piece. Then, place copper plates on both the upper and lower layers of the thick copper plate to obtain a workpiece to be welded. Then, place the arc starting plate and the arc ending plate on both sides of the workpiece to be welded, and use a welding fixture to fix the arc starting plate, the arc ending plate, and the workpiece to be welded. Finally, perform a double-pass weld on the arc starting plate, the workpiece to be welded, and the arc ending plate along the weld seam using a friction stir welding device.

[0011] Step S4: Process the sample piece obtained after welding in Step S3, remove the arc starting plate, the arc ending plate, and the copper plates above and below, and then a friction stir welding joint of the thick copper plate and multiple layers of copper foils is obtained.

[0012] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a friction stir welding method for a thick copper plate and multiple layers of copper foils. This welding method realizes the metallurgical connection between the thick copper plate and multiple layers of copper foils, the joint has good performance, the joint is flat, the deformation is small, and the joint volume is significantly smaller than that of a commonly used brazed joint. And welding with the bottom end face of the second sample piece facing up, that is, the back of the weld seam facing up, can solve the deformation of the bottom copper foil caused by heat influence and reduce the risk of copper foil deformation. At the same time, compared with brazing, friction stir welding has the beneficial effects of smokeless and dustless, green production, without using solder and flux, and low production cost. The present invention realizes the effective connection between the thick copper plate and the foil through reasonable joint welding process design, which is of great significance for improving the stability of power transmission.

[0013] Further, the thickness of the thin copper foil is 0.1 - 0.3 mm.

[0014] Further, in Step S1 and Step S3, the rotation speed of the stirring head of the friction stir welding device is 1180 r / min, the welding speed is 60 mm / min, the tilt angle is -3°, and the downward pressure is 0.2 mm.

[0015] The beneficial effects of adopting the above technical solution are that it is convenient to obtain a welded joint with good surface forming and no defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0017] Figure 1 The drawing is a schematic diagram of step S1 in a friction stir welding method for a thick copper plate and multiple copper foils provided by the present invention.

[0018] Figure 2 The drawing is a schematic diagram of step S2 in a friction stir welding method for a thick copper plate and multiple copper foils provided by the present invention.

[0019] Figure 3 The drawing is a schematic diagram of step S3 in a friction stir welding method for a thick copper plate and multiple copper foils provided by the present invention.

[0020] Figure 4 The drawing is a schematic diagram of the welding process flow of a friction stir welding method for a thick copper plate and multiple copper foils provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0022] The embodiment of the present invention discloses a friction stir welding method for a thick copper plate and multiple copper foils, including the following welding steps:

[0023] See Figure 1 , step S1: Stack multiple thin copper foils 1 with a thickness of 0.1 - 0.3 mm into a copper foil body 2 with a thickness of 10.2 - 10.5 mm. Then, place copper plates 3 with a thickness of 2 mm on both the upper and lower layers of the copper foil body 2 to obtain a first sample part 4. Then, place an arc starting plate 5 and an arc ending plate 6 on both sides of the first sample part 4, and use a welding fixture to fix the arc starting plate 5, the arc ending plate 6, and the first sample part 4. Finally, perform a single pass welding on the arc starting plate 5, the first sample part 4, and the arc ending plate 6 using a friction stir welding device 7 to facilitate the welding of the multiple copper foils;

[0024] See Figure 2 , Step S2: After the first pass of welding is completed, remove the starting plate 5 and the ending plate 6, and then cut the first sample piece 4 along the middle of the weld seam 8 of the first pass of welding to obtain two second sample pieces 41;

[0025] See Figure 3 , Step S3: Place one of the second sample pieces 41 with its bottom end face facing up, that is, with the back side of the weld seam facing up, then buttweld one side of the thick copper plate 9 with the weld seam 8 of the second sample piece 41, and then place copper plates 3 with a thickness of 2 mm on both the upper and lower layers of the thick copper plate 9 to obtain the workpiece to be welded 10. Then place the starting plate 5 and the ending plate 6 on both sides of the workpiece to be welded 10, and use a welding fixture to fix the starting plate 5, the ending plate 6 and the workpiece to be welded 10. Finally, use the friction stir welding device 7 to perform the second pass of welding along the weld seam 8 on the starting plate 5, the workpiece to be welded 10 and the ending plate 6;

[0026] Step S4: Process the sample obtained after welding in Step S3, and remove the starting plate 5, the ending plate 6 and the copper plates 3 above and below, that is, obtain the friction stir welding joint of the thick copper plate and the multi-layer copper foils.

[0027] Among them, in Step S1 and Step S3, the rotation speed of the stirring head of the friction stir welding device 7 is 1180 r / min, the welding speed is 60 mm / min, the tilt angle is -3°, and the downward pressure is 0.2 mm. The downward pressure of 0.2 mm can avoid excessive downward pressure from damaging the copper plate and cutting and thinning the copper foil; at the same time, it can avoid too small downward pressure and insufficient heat input, which cannot achieve the effect of frictionally extruding and forming the multi-layer thin copper foils.

[0028] In this method, copper plates are arranged on both the upper and lower layers of the thin copper foil and the thick copper plate, so that the stirring head of the friction stir welding device does not directly bear force on the thin copper foil and the thick copper plate, thus preventing damage to the thin copper foil and the thick copper plate during the welding process. Moreover, after the first pass of welding, the copper foil at the bottom of the second sample piece will be bent and deformed due to the heat effect. Before the second pass of welding, the back of the weld seam is turned upwards, that is, the bottom end face of the second sample piece is turned upwards, and then the stirring head of the friction stir welding device is used to press down on this surface, which can reduce the deformation of the bottom copper foil caused by the heat effect. Therefore, this welding process can greatly reduce the welding deformation defect of the welded joint between the thick copper plate and the multi-layer copper foil. In addition, in the above welding process, welding starts from the arc starting plate to facilitate heat transfer to the arc starting plate, making the material reach the plasticized state to reduce the wear of the stirring head. During the welding process, due to the plastic flow of the material, the plasticized material in the arc starting plate will fill the gap when the second sample piece is butted against the thick copper plate to reduce defects. After the welding is completed, the stirring head moves to the arc ending plate. At this time, the excess material of the second sample piece and the thick copper plate moves to the arc ending plate along with the plastic flow of the material, ensuring that the welded joint is flat and dense, and at the same time, the keyhole remains on the arc ending plate. Therefore, the setting of the arc starting plate and the arc ending plate can further ensure the welding quality of the friction stir welded joint between the thick copper plate and the multi-layer copper foil.

[0029] Specific Embodiment 1:

[0030] Step S1: Stack multiple 0.1-mm-thick thin copper foils 1 to form a 5.2-mm-thick copper foil body 2, then place copper plates 3 with a thickness of 2 mm on both the upper and lower layers of the copper foil body 2 to obtain a first sample piece 4. Then, place the arc starting plate 5 and the arc ending plate 6 on both sides of the first sample piece 4, and use welding jigs to fix the arc starting plate 5, the arc ending plate 6, and the first sample piece 4. Finally, perform the first pass of welding on the arc starting plate 5, the first sample piece 4, and the arc ending plate 6 using a friction stir welding device 7. The rotation speed of the stirring head of the friction stir welding device 7 is 1180 r / min, the welding speed is 60 mm / min, the tilt angle is -3°, and the downward pressure is 0.2 mm.

[0031] Step S2: After the first pass of welding is completed, use a hacksaw to remove the arc starting plate 5 and the arc ending plate 6, and then cut the first sample piece 4 along the middle of the weld seam 8 of the first pass of welding to obtain two second sample pieces 41.

[0032] Step S3: Turn the bottom end face of one of the second sample pieces 41 upwards, that is, make the back side of the weld seam face upwards, then butt one side of a copper thick plate 9 with a thickness of 5 mm against the weld seam 8 of the second sample piece 41, then place copper plates 3 with a thickness of 2 mm on both the upper layer and the lower layer of the copper thick plate 9 to obtain the workpiece to be welded 10, then place the arc starting plate 5 and the arc ending plate 6 on both sides of the workpiece to be welded 10, and use a welding fixture to fix the arc starting plate 5, the arc ending plate 6 and the workpiece to be welded 10. Finally, use a friction stir welding device 7 to perform two-pass welding along the weld seam 8 on the arc starting plate 5, the workpiece to be welded 10, and the arc ending plate 6. The rotation speed of the stirring head of the friction stir welding device 7 is 1180 r / min, the welding speed is 60 mm / min, the inclination angle is -3°, and the downward pressure is 0.2 mm;

[0033] Step S4: Process the sample piece obtained after welding in Step S3, and use a hacksaw to remove the arc starting plate 5, the arc ending plate 6, and the copper plates 3 above and below, that is, obtain the friction stir welding joint of the copper thick plate and the multi-layer copper foil.

[0034] Specific Embodiment 2:

[0035] Step S1: Stack multi-layer thin copper foils 1 with a thickness of 0.1 mm into a copper foil body 2 with a thickness of 10.2 mm, then place copper plates 3 with a thickness of 2 mm on both the upper layer and the lower layer of the copper foil body 2 to obtain the first sample piece 4, then place the arc starting plate 5 and the arc ending plate 6 on both sides of the first sample piece 4, and use a welding fixture to fix the arc starting plate 5, the arc ending plate 6 and the first sample piece 4. Finally, use a friction stir welding device 7 to perform one-pass welding on the arc starting plate 5, the first sample piece 4, and the arc ending plate 6. The rotation speed of the stirring head of the friction stir welding device 7 is 1180 r / min, the welding speed is 60 mm / min, the inclination angle is -3°, and the downward pressure is 0.2 mm;

[0036] After the one-pass welding is completed, use a hacksaw to remove the arc starting plate 5 and the arc ending plate 6, and then cut the first sample piece 4 along the middle of the weld seam 8 of the one-pass welding to obtain two second sample pieces 41;

[0037] Step S3: Turn the bottom end face of one of the second sample pieces 41 upwards, that is, make the back side of the weld seam face upwards, then butt one side of a copper thick plate 9 with a thickness of 10 mm against the weld seam 8 of the second sample piece 41, then place copper plates 3 with a thickness of 2 mm on both the upper layer and the lower layer of the copper thick plate 9 to obtain the workpiece to be welded 10, then place the arc starting plate 5 and the arc ending plate 6 on both sides of the workpiece to be welded 10, and use a welding fixture to fix the arc starting plate 5, the arc ending plate 6 and the workpiece to be welded 10. Finally, use a friction stir welding device 7 to perform two-pass welding along the weld seam 8 on the arc starting plate 5, the workpiece to be welded 10, and the arc ending plate 6. The rotation speed of the stirring head of the friction stir welding device 7 is 1180 r / min, the welding speed is 60 mm / min, the inclination angle is -3°, and the downward pressure is 0.2 mm;

[0038] Step S4: Process the sample material obtained after welding in Step S3. Use a hacksaw to remove the arc striking plate 5, the arc extinguishing plate 6, and the copper plates 3 above and below, and thus obtain a friction stir welding joint of a thick copper plate and multiple layers of copper foil.

[0039] Through the electrical conductivity test and strength test on the welded joints obtained in the above-mentioned Embodiment 1 and Embodiment 2, the service performance of the welded joint of the thick copper plate and multiple layers of copper foil is satisfied. Therefore, this welding method can achieve the welding of a defect-free metallurgical welded joint of the thick copper plate and multiple layers of copper foil.

[0040] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and reference can be made to the description in the method part for the relevant parts.

[0041] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A friction stir welding method for a thick copper plate and a multi-layer copper foil, characterized in that, It includes the following welding steps: Step S1: Stack multiple layers of thin copper foils (1) into a copper foil body (2), then place copper plates (3) on both the upper and lower layers of the copper foil body (2) to obtain a first sample piece (4). Then, place an arc starting plate (5) and an arc ending plate (6) on both sides of the first sample piece (4), and use a welding fixture to fix the arc starting plate (5), the arc ending plate (6), and the first sample piece (4). Finally, perform a single-pass weld on the arc starting plate (5), the first sample piece (4), and the arc ending plate (6) using a friction stir welding device (7); Step S2: After the single-pass weld is completed, remove the arc starting plate (5) and the arc ending plate (6), and then cut the first sample piece (4) along the middle of the weld seam (8) of the single-pass weld to obtain two second sample pieces (41); Step S3: Place one of the second sample pieces (41) with its bottom end face facing up, then butt one side of a thick copper plate (9) against the weld seam (8) of the second sample piece (41). Then, place the copper plates (3) on both the upper and lower layers of the thick copper plate (9) to obtain a workpiece to be welded (10). Then, place the arc starting plate (5) and the arc ending plate (6) on both sides of the workpiece to be welded (10), and use a welding fixture to fix the arc starting plate (5), the arc ending plate (6), and the workpiece to be welded (10). Finally, perform a double-pass weld on the arc starting plate (5), the workpiece to be welded (10), and the arc ending plate (6) along the weld seam (8) using the friction stir welding device (7); Step S4: Process the sample piece obtained after welding in Step S3, remove the arc starting plate (5), the arc ending plate (6), and the copper plates (3) above and below, and thus obtain a friction stir welding joint of the thick copper plate and multiple layers of copper foils.

2. A friction stir welding method for a thick copper plate and a multi-layer copper foil according to claim 1, characterized in that, The thickness of the thin copper foil (1) is 0.1 - 0.3 mm.

3. A friction stir welding method for a thick copper plate and a multi-layer copper foil according to claim 1, characterized in that, In Step S1 and Step S3, the rotational speed of the stirring head of the friction stir welding device (7) is 1180 r / min, the welding speed is 60 mm / min, the tilt angle is -3°, and the downward pressure is 0.2 mm.

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