Method and apparatus for cooperatively preparing multi-level heterostructure of weld seam by using dual laser beams

Abstract

A method and apparatus for cooperatively preparing a multi-level heterostructure of a weld seam by using dual laser beams. Said preparation apparatus comprises an optical fiber laser (1) provided with a galvanometer system, a short-wave laser (2), a dual-band hybrid wobble welding head (4), an optical path system (3), a robot control system (5), a cooling system (6), and a protection apparatus (7). Said method comprises: using an optical fiber laser (1) to perform wobble filling welding, using an Al-Si-Mg-Cu-Zn-Sn-based alloy as a filling material for a weld seam, and obtaining a weld seam having a heterogeneous crystalline structure; at the same time, using a short-wave laser for on-line baking the weld seam, which promotes complex precipitation of various nano-phases and a gradient distribution in the depth direction of the weld seam. According to said apparatus and method, a weld seam made of an aluminum alloy provided with a combination of multi-level heterostructures can be prepared, the comprehensive performance of the weld joint is cooperatively improved, and thus the problem of unmatched strength and plasticity of a fusion weld seam of a heat-treatable reinforced aluminum alloy is solved.

Description

A method and device for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams Technical Field

[0001] The present invention relates to the technical field of metal material welding, and in particular to a method and device for collaboratively preparing a weld multi-level heterogeneous structure with dual laser beams. Background Art

[0002] With the development of the industrial age, cars are becoming more and more popular in our lives, but this also brings about high energy consumption and environmental pollution problems. Lightweighting of vehicle bodies is considered an effective strategy to reduce automobile energy consumption and pollution. Therefore, aluminum alloys with low density and high strength have been widely used. However, under the action of welding heat source, the softening problem of aluminum alloy welds seriously deteriorates the mechanical properties of welded joints. So far, people have used traditional methods such as grain boundary strengthening, precipitation phase strengthening, solid solution strengthening, and deformation strengthening to improve the mechanical properties of welded joints. Although these methods improve the strength and hardness of the weld, they sacrifice plasticity, resulting in the problem of inverted weld strength and plasticity.

[0003] In recent years, it has been discovered that metallic materials with gradient heterostructures exhibit unexpectedly high mechanical properties. The synergistic effects of heterogeneous regions can simultaneously enhance weld strength and ductility. Heterostructures exhibit distinct material / structural differences between regions, often manifesting as macro / microstructural heterogeneity. The design of these heterostructures is inspired by heterogeneous biomaterials found in nature, which have evolved through millions of years of natural selection to survive in harsh environments. Heterostructures impart unprecedented performance and functional synergies to biomaterials.

[0004] Inspired by nature, researchers are using heterogeneous structures as a new strategy to customize the properties of aluminum alloys. Patent CN·116162872·A utilizes a solid solution-rapid heating-large deformation-aging process to produce a multi-level heterogeneous strengthening structure, improving the hardness, strength and other mechanical properties of the aluminum alloy. Patent CN·116479281·A adds TiB2 and TiC particles to the aluminum alloy during preparation, and after extrusion and solid solution heat treatment, produces an alloy with mixed crystal heterogeneous structure characteristics, simultaneously improving the strength and elongation of the aluminum alloy profile. However, existing methods are not suitable for preparing heterogeneous structures of welds and cannot meet the welding manufacturing requirements of automobile bodies. Summary of the Invention

[0005] The present invention aims to provide a method and apparatus for collaboratively fabricating weld seams with dual laser beams to simultaneously enhance both weld strength and ductility, thereby meeting the requirements of automobile body welding. To achieve this goal, the present invention employs the following technical solutions:

[0006] A method for collaboratively preparing a weld multi-level heterogeneous structure using dual laser beams comprises the following steps:

[0007] Step (1): Swinging laser filling welding: The aluminum alloy plate is filled with welding by swinging laser. The reheating effect of the beam swing is used to continuously melt the solidified grains in the molten pool to form broken crystals, providing nucleation conditions for the formation of fine equiaxed crystal bands.

[0008] Step (2): laser online baking of the solid weld: the weld obtained by laser welding is repeatedly scanned by laser, and the weld is baked quickly and in a short time, so that the temperature field generated by the baking is distributed in a gradient in the depth direction of the weld;

[0009] Step (3): Adjust the laser welding-laser baking process parameters, and coordinately control the molten pool solidification parameters and the weld temperature field to promote the survival of broken dendrites, form fine equiaxed crystal bands at the bottom of the remelted molten pool, and meet the temperature conditions for nanophase precipitation, thereby promoting the precipitation of multiple nanophases and distributing them in a gradient along the depth direction of the weld. Through the above steps, the aluminum alloy weld forms a heterogeneous grain structure with a mixture of fine equiaxed crystal bands and coarse grains and a gradient precipitation phase structure, thus forming a multi-level heterogeneous structure.

[0010] Furthermore, the aluminum alloy described in step (1) is a heat-treatable and strengthened aluminum alloy, including 2XXX series, 4XXX series, 5XXX series, 6XXX series, and 7XXX series aluminum alloys.

[0011] Furthermore, the reheating temperature brought about by the power, oscillation frequency, and oscillation amplitude of the oscillating laser welding in step (1) must match the solidification range of the material.

[0012] Furthermore, the oscillating laser filling welding method in step (1) is one or more of oscillating laser wire filling welding, oscillating laser powder filling welding, oscillating laser sheet filling welding, oscillating laser-CMT composite, oscillating laser-MIG composite, and oscillating laser-TIG composite.

[0013] Furthermore, the filling material in step (1) is an Al-Si-Mg-Cu-Zn-Sn alloy or an Al-Mg-Si-Cu-Zn-Sn alloy.

[0014] Furthermore, the filler material in step (1) is in the form of one or more of 10-200um powder, 50-1000um flakes, and 0.5-3.2mm diameter welding wire.

[0015] Furthermore, the type of baking laser used in step (2) is one or more of infrared laser, blue laser, and green laser.

[0016] Furthermore, the parameters for regulating the molten pool solidification in step (3) include temperature gradient, solidification rate and cooling rate.

[0017] Furthermore, the temperature condition of the rapid short-time baking in step (2) is 100-350° C., and the baking time is 0-30 min.

[0018] A device for collaboratively preparing multi-level heterogeneous structures of welds using dual laser beams comprises a fiber laser with a galvanometer system, a short-wavelength laser, an optical path system, a dual-band composite oscillating welding head, a control system, a cooling system, and a protective device. The fiber laser and the short-wavelength laser are mounted side by side on the upper portion of the optical path system, the dual-band composite oscillating welding head is mounted on the lower portion of the optical path system, the control system is communicatively connected to the optical path system, the cooling system is mounted on the fiber laser and the short-wavelength laser, and the protective device is connected to the optical path system.

[0019] Furthermore, the cooling system is a cooling water pipe, and the protection device is an inert gas protection pipe.

[0020] The beneficial effects of the invention are:

[0021] First, by synergistically utilizing oscillating laser welding and laser online baking welds, a multi-level heterogeneous structure with heterogeneous grains and gradient precipitation phases is prepared, significantly improving the strength and ductility of the welds and resolving the problem of inverted strength and ductility in heat-treatable aluminum alloy fusion welds.

[0022] 2. The characteristics of heterogeneous structures can be adjusted without expanding the heat affected zone of welding;

[0023] 3. Swinging laser welding can effectively suppress defects such as pores, increase the supersaturation of the aluminum matrix, promote the rapid precipitation of multiple strengthening phases during laser baking, and greatly improve welding quality and efficiency;

[0024] 4. Flexible and efficient, it can realize the simultaneous integration of welding and baking of large structural parts, complex joints and micro-areas, and support online monitoring of on-site welding process and baking temperature to meet the welding manufacturing needs of high-end equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0026] FIG1 is a flow chart of a method for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams according to the present invention;

[0027] FIG2 is a schematic diagram of a device for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams according to the present invention;

[0028] FIG3 is a longitudinal cross-sectional view of the grain morphology of Comparative Example 1 of the present invention;

[0029] FIG4 is a longitudinal cross-sectional view of the grain morphology of Example 1 of the present invention;

[0030] FIG5 is a cross-sectional microhardness diagram of Example 1, Example 2 and Comparative Example 1 of the present invention;

[0031] FIG6 is a graph showing the tensile mechanical properties of Example 1, Example 2, and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0032] To make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention more clear, the technical solutions of the embodiments of the present invention will be further described in detail below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] A device for collaboratively preparing multi-level heterogeneous structures of welds using dual laser beams comprises a fiber laser 1 with a galvanometer system, a short-wavelength laser 2, an optical path system 3, a dual-band composite oscillating welding head 4, a control system 5, a cooling system 6, and a protective device 7. The fiber laser and the short-wavelength laser are mounted side by side on the upper portion of the optical path system, the dual-band composite oscillating welding head is mounted on the lower portion of the optical path system, the control system is communicatively connected to the optical path system, the cooling system is mounted on the fiber laser and the short-wavelength laser, and the protective device is connected to the optical path system.

[0034] The cooling system is a cooling water pipe, the protection device is an inert gas protection pipeline, and the control system is a computer.

[0035] Example 1: This example describes a method for achieving a multi-level heterogeneous structure reinforcement. The welding base material used is a 3 mm thick Al-Mg-Si-Cu alloy plate with dimensions of 50 mm x 50 mm. The filler material is a 1.2 mm diameter Al-Si-Mg-Cu-Zn aluminum alloy welding wire.

[0036] The specific implementation steps of this embodiment are:

[0037] (1) The oscillating laser wire filling welding was performed using the following process parameters: laser power of 2800 W, welding speed of 50 mm / s, defocus of 0 mm, oscillation frequency of 100 Hz, and oscillation amplitude of 1.2 mm.

[0038] (2) Using blue laser (wavelength ~ 450nm) to bake the solid weld online. The process parameters of blue laser power of 500W and scanning speed of 60mm / s are used to bake the weld online.

[0039] (3) The spacing between the oscillating laser and blue laser beams was adjusted to control the solidification conditions of the molten pool, and a heterogeneous grain structure weld with a mixture of fine equiaxed crystal bands and coarse grain areas was obtained. At the same time, the defocus of the blue laser was adjusted, and the weld was baked online for 1 minute to promote the composite precipitation of multiple strengthening phases and their gradient distribution along the depth direction of the weld, so that the microhardness also showed a gradient distribution along the depth direction of the weld.

[0040] Example 2: This example describes a method for achieving a multi-level heterogeneous structure reinforcement. The welding base material used is a 3 mm thick Al-Mg-Si-Cu alloy plate with dimensions of 50 mm x 50 mm. The filler material is a 1.2 mm diameter Al-Si-Mg-Cu-Zn aluminum alloy welding wire.

[0041] The specific implementation steps of this embodiment are:

[0042] (1) The oscillating laser wire filling welding was performed using the following process parameters: laser power of 2800 W, welding speed of 50 mm / s, defocus of 0 mm, oscillation frequency of 100 Hz, and oscillation amplitude of 1.2 mm.

[0043] (2) Using blue laser (wavelength ~ 450nm) to bake the solid weld online. The process parameters of blue laser power of 500W and scanning speed of 60mm / s are used to bake the weld online.

[0044] (3) The spacing between the oscillating laser and blue laser beams was adjusted to control the solidification conditions of the molten pool, and a heterogeneous grain structure weld with a mixture of fine equiaxed crystal bands and coarse grain areas was obtained. At the same time, the defocus of the blue laser was adjusted, and the weld was baked online for 5 minutes to promote the composite precipitation of multiple strengthening phases and their gradient distribution along the depth direction of the weld, so that the microhardness also showed a gradient distribution along the depth direction of the weld.

[0045] Comparative Example 1: For comparison with Example 1, the material used was a 3 mm thick Al-Mg-Si-Cu alloy plate with a size of 50 mm × 50 mm. The filler material was an Al-Si-Mg-Cu-Zn aluminum alloy welding wire with a diameter of 1.2 mm.

[0046] This comparative example uses direct laser welding:

[0047] The welding was performed with a laser power of 2800 W, a welding speed of 50 mm / s, and a defocus amount of 0 mm to directly obtain the weld joint.

[0048] By comparison, it can be found that the swing laser welding and laser online baking welds of the present invention produce a structure with a multi-level heterogeneous structure, which synergistically improves the strengthening and plasticity of the heat-treatable strengthened aluminum alloy welds.

[0049] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will readily conceive of other specific embodiments of the present invention without inventive effort, and such embodiments will fall within the scope of protection of the present invention.

Claims

1. A method for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams, characterized in that: The following steps are involved: Step (1): Swinging laser filling welding: The aluminum alloy plate is filled with welding by swinging laser. The reheating effect of the beam swing is used to continuously melt the solidified grains in the molten pool to form broken crystals, providing nucleation conditions for the formation of fine equiaxed crystal bands. Step (2): laser online baking of the solid weld: the weld obtained by laser welding is repeatedly scanned by laser, and the weld is baked quickly and in a short time, so that the temperature field generated by the baking is distributed in a gradient in the depth direction of the weld; Step (3): Adjust the laser welding and laser baking process parameters, and coordinately control the molten pool solidification parameters and the weld temperature field to promote the survival of broken dendrites, so that fine equiaxed crystal bands are formed at the bottom of the remelted molten pool, and at the same time meet the temperature conditions for the precipitation of nanophases, thereby promoting the precipitation of multiple nanophases, and distributing them in a gradient in the depth direction of the weld, so that the aluminum alloy weld forms a heterogeneous grain structure of fine equiaxed crystal bands and coarse grain areas, and a gradient precipitation phase structure, thereby forming a multi-level heterogeneous structure.

2. The method for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams according to claim 1, characterized in that: The aluminum alloy described in step (1) is a heat-treatable and strengthened aluminum alloy, which is one or more of 2XXX series, 4XXX series, 5XXX series, 6XXX series and 7XXX series aluminum alloys.

3. The method for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams according to claim 1, characterized in that: The reheating temperature brought about by the power, oscillation frequency and oscillation amplitude of the oscillating laser welding in step (1) matches the solidification range of the material.

4. The method for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams according to claim 1, characterized in that: The oscillating laser filling welding method in step (1) is one or more of oscillating laser wire filling welding, oscillating laser powder filling welding, oscillating laser sheet filling welding, oscillating laser-CMT composite, oscillating laser-MIG composite, and oscillating laser-TIG composite.

5. The method for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams according to claim 1, characterized in that: The filling material in step (1) is an Al-Si-Mg-Cu-Zn-Sn alloy or an Al-Mg-Si-Cu-Zn-Sn alloy, and the filling material is in the form of one or more of 10-200um powder, 50-1000um flakes and 0.5-3.2mm diameter welding wire.

6. The method for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams according to claim 1, characterized in that: The laser used for baking in step (2) is one or more of infrared laser, blue laser and green laser.

7. The method for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams according to claim 1, characterized in that: The temperature condition of the rapid short-time baking in step (2) is 100-350° C., and the baking time is 0-30 minutes.

8. The method for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams according to claim 1, characterized in that: The parameters for regulating the molten pool solidification in step (3) include temperature gradient, solidification rate and cooling rate.

9. A device for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams, characterized in that: The invention comprises a fiber laser with a galvanometer system, a short-wave laser, an optical path system, a dual-band composite oscillating welding head, a control system, a cooling system and a protective device. The fiber laser and the short-wave laser are installed side by side on the upper part of the optical path system, the dual-band composite oscillating welding head is installed on the lower part of the optical path system, the control system is communicatively connected with the optical path system, the cooling system is installed on the fiber laser and the short-wave laser, and the protective device is connected to the optical path system.

10. The device for collaboratively preparing weld multi-level heterogeneous structures using dual laser beams according to claim 9, characterized in that: The cooling system is a cooling water pipe, and the protection device is an inert gas protection pipeline.

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