Laser welding method for reducing air hole and crack defects

Abstract

The invention discloses a laser welding method for reducing air hole and crack defects, the method comprises the six steps of material preparation, laser cleaning, lap joint and fixation, preheating treatment, laser welding and heat treatment, the material thickness is 0.5-5 mm, the surface roughness Ra after laser cleaning reaches 0.8-2.0 microns, and the interface gap after clamping by a clamp is smaller than 100 microns; the preheating laser power is 2000-4000 W, the welding laser power is 1000-2000 W, the interval between the preheating laser power and the welding laser power is 1-10 s, and finally heat treatment is conducted for 10-60 min at the temperature of 100-500 DEG C. Impurities are removed through laser cleaning, laser parameters are optimized to promote gas overflow, residual stress is eliminated through heat treatment, air holes and cracks are remarkably reduced, the strength of a welding joint is improved, operation is easy, cost is low, and the special-shaped part welding requirement is met.

Description

Technical Field

[0001] This invention relates to laser welding technology, specifically to a laser welding method for reducing porosity and crack defects in aluminum and copper alloys, applicable to precision welding of thin-plate alloys in the automotive, electronics, and aerospace industries. Background Technology

[0002] Laser welding, with its advantages of high energy density, narrow heat-affected zone, and fast welding speed, is widely used in the joining of alloy materials, especially meeting the needs of aluminum alloy welding for the lightweight development of new energy vehicles. However, laser welding of aluminum and copper alloys still faces many technical bottlenecks, which seriously restrict the welding quality.

[0003] Alloy materials have high reflectivity to lasers, making it difficult for laser energy to be effectively absorbed, which can easily lead to insufficient penetration and affect the joint connection strength.

[0004] High-melting-point oxide films (such as aluminum oxide in aluminum alloys) are easily formed on the surface of alloys, and they easily adsorb oil stains and inclusions. These substances can become nucleation sources for pores, resulting in a large number of pores after welding.

[0005] The supersaturated solid solution properties, aging embrittlement, and non-equilibrium structure of the alloy can easily lead to grain boundary embrittlement, which in turn can cause cracks in the welded joint.

[0006] When welding irregularly shaped alloy parts commonly used in new energy vehicles and other fields, it is difficult to precisely control the interface gap. Stress release and deformation after welding can easily induce interface cracks.

[0007] Traditional single-beam laser welding has highly concentrated energy. When applied to thin plate alloys, it can easily lead to violent fluctuations in the molten pool, alloy vapor jetting, and defects such as spatter, dense porosity, and cracks, which seriously affect the safety and reliability of the welded parts.

[0008] To address the aforementioned issues, there is an urgent need to develop a laser welding method that can fundamentally resolve porosity and crack defects while simultaneously improving joint strength. Summary of the Invention

[0009] This invention aims to provide a laser welding method that reduces porosity and crack defects. By specifically designing the welding process and parameters, it solves problems such as high reflectivity, oxide film interference, stress cracking, and poor gap control in existing alloy laser welding, and achieves a low-defect, high-strength welding effect.

[0010] To achieve the above and other related objectives, the technical solution provided by this invention is: a laser welding method for reducing porosity and crack defects, comprising the following steps:

[0011] Step 1: Provide a first alloy material and a second alloy material;

[0012] Step 2: Perform laser cleaning on the welding surfaces of the first alloy material and the second alloy material;

[0013] Step 3: Overlap the welding surface of the first alloy material onto the welding surface of the second alloy material and fix it with a clamp;

[0014] Step 4: Preheat the welding surfaces of the first alloy material and the second alloy material using a preheating laser;

[0015] Step 5: Weld the welding surfaces of the first alloy material and the second alloy material using a welding laser;

[0016] Step 6: Perform heat treatment on the welded area.

[0017] The preferred technical solution is as follows: In step 1, the first alloy material is any one of aluminum alloy and copper alloy; the second alloy material is any one of aluminum alloy and copper alloy; the first alloy material and the second alloy material are obtained by any one of the processing methods of stamping, laser cutting, high-pressure water jet cutting and 3D vertical bending; the thickness of the first alloy material or the second alloy material is 0.5~5mm; the flatness of the overlapping area of ​​the first alloy material and the second alloy material is <0.1mm.

[0018] The preferred technical solution is as follows: In step 2, the parameters of the laser cleaning are: laser scanning speed 5000~15000mm / s, power 60~150W, frequency 50~200KHz, pulse width 50~150ns, switching delay -250~-50us, light-off delay 50~150us, corner delay 50~150us; the surface roughness Ra of the first alloy material and the second alloy material after laser cleaning is 0.8~2.0um.

[0019] The preferred technical solution is: in step 3, the interface gap between the first alloy material and the second alloy material after being clamped by the fixture is <100um.

[0020] The preferred technical solution is as follows: In step 4, the parameters of the preheating laser are: defocusing amount -0.5mm to -1.5mm, laser power 2000W to 4000W, scanning speed 10mm / s to 40mm / s, oscillation frequency 50HZ to 150HZ, and oscillation amplitude 0.5mm to 1.5mm.

[0021] The preferred technical solution is as follows: In step 4, the parameters of the preheating laser are: defocusing amount -1mm, laser power 2500W, scanning speed 30mm / s, oscillation frequency 120HZ, and oscillation amplitude 1mm.

[0022] The preferred technical solution is as follows: In step 5, the parameters of the welding laser are: defocusing amount -0.5mm to -3mm, laser power 1000W to 2000W, welding speed 30 to 70mm / s, the laser is any one of sinusoidal, spiral, linear and infinite types, oscillation frequency 50 to 250HZ, and oscillation amplitude 0.5 to 2.5mm.

[0023] The preferred technical solution is as follows: In step 5, the parameters of the welding laser are: defocusing amount -1mm, laser power 1500W, scanning speed 60mm / s, the laser is in a spiral or sinusoidal shape, the oscillation frequency is 180HZ, and the oscillation amplitude is 2mm.

[0024] The preferred technical solution is that the interval between steps 4 and 5 is 1s to 10s, and the interval between steps 4 and 5 is 2s.

[0025] The preferred technical solution is as follows: In step 6, the parameters of the heat treatment are: temperature 100~500℃, time 10~60min.

[0026] Due to the application of the above technical solution, the beneficial effects of this invention are as follows:

[0027] Solving the problem of high reflectivity: Laser cleaning increases the roughness of the welding surface, and preheating treatment reduces the reflectivity of the material. Under the dual effect, the absorption efficiency of the alloy to laser energy is significantly improved, effectively solving the problem of insufficient penetration and improving the joint connection strength.

[0028] Reduce porosity defects: Laser cleaning thoroughly removes oxide film, oil stains, inclusions and other porosity nucleation sources from the welding surface. Preheating and welding parameter optimization slow down the solidification rate of the molten pool and promote gas overflow. At the same time, the fixture controls the interface gap to prevent air from entering. The synergy of multiple links greatly reduces the incidence of porosity defects.

[0029] Suppressing crack initiation: Fixture fixation reduces welding deformation and stress concentration, heat treatment eliminates residual stress and improves microstructure, avoids grain boundary embrittlement and aging embrittlement caused by non-equilibrium phases, and the stabilizing effect of welding laser reduces molten pool fluctuations, thus suppressing crack initiation and propagation from both stress and microstructure perspectives.

[0030] Adaptation to welding irregularly shaped parts: By controlling the flatness of the material and the interface gap, the method is applicable to the welding of irregularly shaped alloy parts, solving the welding defects caused by the difficulty in positioning irregularly shaped parts and poor gap control;

[0031] Simple and efficient operation: The entire process is clear and the parameter settings are well-defined. No complex equipment modifications are required, the cost is low, and the welding speed is fast with a narrow heat-affected zone. It balances production efficiency and welding quality and is suitable for large-scale production. Attached Figure Description

[0032] Figure 1 This is a flowchart of the laser welding method involved in the present invention.

[0033] Figure 2 These are metallographic photographs of the welded products involved in embodiments of the present invention.

[0034] Figure 3 The image shown is a metallographic photograph of the welded product involved in the comparative example of this invention. Detailed Implementation

[0035] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0036] Please see Figures 1-3 It should be noted that in the description of this invention, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. The terms "horizontal," "vertical," and "suspended," etc., do not indicate that the component must be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0037] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] Example:

[0039] like Figure 1 As shown, according to a general technical concept of the present invention, a laser welding method for reducing porosity and crack defects is provided, comprising the following steps:

[0040] (1) AL1060O state aluminum strip with a width of 20mm and a thickness of 3mm and AL6101T63 state aluminum alloy strip with a width of 20mm and a thickness of 4mm were prepared by 3D vertical bending process.

[0041] (2) Laser cleaning was performed on both the upper and lower surfaces of the overlapping areas of AL1060 and AL6101 strips. The parameters were: laser scanning speed 10000 mm / s, power 90 W, frequency 150 kHz, pulse width 100 ns, switching delay -150 μs, switching-off delay 100 μs, and corner delay 80 μs. This resulted in an average surface roughness Ra of 0.9~1.2 μm for AL1060 and AL6101 after laser cleaning.

[0042] (3) Place the laser-cleaned AL1060 on top and AL6101 on the bottom in the fixture, with the interface gap after overlapping <100um.

[0043] (4) Preheating is performed. The preheating laser parameters are: defocusing amount -1mm, laser power 2500W, scanning speed 30mm / s, oscillation frequency 120HZ, and oscillation amplitude 1mm.

[0044] (5) Welding is performed. The welding laser parameters are: defocusing amount -1mm, laser power 1500W, scanning speed 60mm / s, laser in spiral or sinusoidal shape, oscillation frequency 180HZ, and oscillation amplitude 2mm.

[0045] (6) Heat treatment is performed on the laser welding area at a temperature of 400℃ for 15 minutes to obtain the welded joint of AL1060 and AL6101.

[0046] It should be noted that the interval between preheating and welding is 2 seconds.

[0047] Comparative example:

[0048] The comparison shows the joints of AL1060 aluminum alloy with a thickness of 3mm and AL6101 aluminum alloy with a thickness of 4mm, welded using the traditional single-beam laser welding method.

[0049] The welded joints of AL1060 and AL6101 aluminum alloys obtained by the laser welding method of the present invention were compared and evaluated for porosity and cracks with the welded joints of AL1060 and AL6101 aluminum alloys obtained by the conventional single-beam laser welding method in the comparative example. The detailed results are shown in Table 1 below.

[0050] Table 1: Test results of porosity, cracks, and joint strength of AL1060 and AL6101 aluminum alloy welded joints in the examples and comparative examples.

[0051]

[0052] From Table 1, Figure 2 and Figure 3 It can be seen that the joints welded by the laser welding method provided in this embodiment of the invention have lower porosity, fewer cracks and higher joint strength.

[0053] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A laser welding method for reducing porosity and crack defects, characterized by, The method comprises the following steps: Step 1, providing a first alloy material and a second alloy material; Step 2, laser cleaning the welding surfaces of the first alloy material and the second alloy material; Step 3, overlapping the welding surface of the first alloy material on the welding surface of the second alloy material and clamping and fixing by a clamp; Step 4, preheating the welding surfaces of the first alloy material and the second alloy material by a preheating laser; Step 5, welding the welding surfaces of the first alloy material and the second alloy material by a welding laser; Step 6, heat treating the welding position.

2. The laser welding method of reducing porosity and crack defects according to claim 1, wherein: In step 1, the first alloy material is any one of aluminum alloy and copper alloy; the second alloy material is any one of aluminum alloy and copper alloy; the first alloy material and the second alloy material are obtained by any one of punching, laser cutting, high-pressure water jet cutting and 3D bending; the thickness of the first alloy material or the second alloy material is 0.5-5 mm; the flatness of the overlapping area of the first alloy material and the second alloy material is less than 0.1 mm.

3. The laser welding method of claim 1, wherein: In step 2, the parameters of the laser cleaning are as follows: laser scanning speed 5000-15000 mm / s, power 60-150 W, frequency 50-200 KHz, pulse width 50-150 ns, switch delay -250--50 us, off light delay 50-150 us, corner delay 50-150 us; the surface roughness Ra of the first alloy material and the second alloy material after laser cleaning is 0.8-2.0 um.

4. The laser welding method of claim 1, wherein: In step 3, the interface gap of the first alloy material and the second alloy material clamped by the clamp is less than 100 um.

5. The laser welding method of claim 1, wherein: In step 4, the parameters of the preheating laser are as follows: defocusing amount -0.5 mm--1.5 mm, laser power 2000 W-4000 W, scanning speed 10 mm / s-40 mm / s, swing frequency 50 HZ-150 HZ, swing amplitude 0.5 mm-1.5 mm.

6. The laser welding method of reducing porosity and cracking defects according to claim 1, wherein: In step 4, the parameters of the preheating laser are as follows: defocusing amount -1 mm, laser power 2500 W, scanning speed 30 mm / s, swing frequency 120 HZ, swing amplitude 1 mm.

7. The laser welding method of reducing porosity and cracking defects according to claim 1, wherein: In step 5, the parameters of the welding laser are as follows: defocusing amount -0.5 mm--3 mm, laser power 1000 W-2000 W, welding speed 30-70 mm / s, laser in any one of sine curve type, spiral line type, straight line type and infinite type, swing frequency 50-250 HZ, swing amplitude 0.5-2.5 mm.

8. The laser welding method of reducing porosity and cracking defects according to claim 1, wherein: In step 5, the parameters of the welding laser are as follows: defocusing amount -1 mm, laser power 1500 W, scanning speed 60 mm / s, laser in spiral line type or sine curve type, swing frequency 180 HZ, swing amplitude 2 mm.

9. The laser welding method of reducing porosity and cracking defects according to claim 1, wherein: The interval time between step 4 and step 5 is 1 s-10 s, and the interval time between step 4 and step 5 is 2 s.

10. The laser welding method of reducing porosity and cracking defects according to claim 1, wherein: In step 6, the parameters of the heat treatment are as follows: temperature 100-500 DEG C, time 10-60 min.

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