Method for porosity suppression in laser welds of aluminum alloys

Abstract

The application discloses a kind of aluminum alloy laser weld seam pore inhibiting method, it includes: using fiber laser to couple swing laser and square wave modulation laser to form welding laser, the butt welding of two Al-Si series die-casting aluminum alloy plates is carried out;Wherein, during welding, the welding laser advances along an axis parallel to welding direction, and reciprocating swing is formed in the two sides of the axis, forms a zigzag movement path, wherein the duty cycle of the square wave modulation laser is set so that the welding laser has no laser output at the trough of the movement path.The aluminum alloy laser weld seam pore inhibiting method can improve the stability of the pore and the intensity of the molten pool convection, inhibit the pore in the Al-Si series die-casting aluminum alloy laser weld seam.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy welding technology, and specifically relates to a method for suppressing porosity in aluminum alloy laser welds. Background Technology

[0002] With the increasing maturity of die casting technology and the industrial application of ultra-large die casting machines, Al-Si alloys with excellent die casting performance are highly favored by major automakers and are gradually being used in the manufacture of battery casings for new energy vehicles. Welding is indispensable in the battery casing manufacturing process, and laser welding has attracted much attention due to its ability to balance welding deformation and welding efficiency. However, the poor stability of the keyhole formed by laser induction leads to the formation of large keyhole-type pores in the weld. Furthermore, due to the high-speed filling characteristics of Al-Si die-cast aluminum alloys, the hydrogen content in the weld exceeds 1 ppm, making it difficult for hydrogen bubbles to escape from the molten pool during the extremely short residence time (less than 0.1 s). Therefore, the porosity of laser welds in Al-Si die-cast aluminum alloys remains high. To reduce the porosity of laser welds, Chinese patent CN116275491A discloses a laser welding method suitable for YZAlSi10Mg aluminum alloys, which utilizes annular spot and beam oscillation coupling to solve the porosity problem in laser welds of Al-Si die-cast aluminum alloys. However, this method, which utilizes ultrasonic field assistance and annular light spots, increases equipment complexity and production costs. Furthermore, the sawtooth laser wave valley used in this patent still results in laser-induced keyholes, and the keyhole-shaped pores formed by keyhole collapse remain, making it difficult for bubbles to escape.

[0003] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a method for suppressing porosity in laser welds of aluminum alloys, which can improve keyhole stability and molten pool convection intensity, and suppress the formation of porosity in laser welds of Al-Si die-cast aluminum alloys.

[0005] To achieve the above objectives, a specific embodiment of the present invention provides a method for suppressing porosity in laser welds of aluminum alloys, comprising: using a fiber laser to couple an oscillating laser and a square-wave modulated laser to form a welding laser, and welding two Al-Si die-cast aluminum alloy plates together; wherein, during the welding process, the welding laser advances along an axis parallel to the welding direction and oscillates back and forth on both sides of the axis to form a tortuous motion path, wherein the duty cycle of the square-wave modulated laser is set such that the welding laser has no laser output at the trough of the motion path.

[0006] In one or more embodiments of the present invention, the welding laser oscillates about the axis of symmetry to form a motion path, which is composed of a plurality of "∞" shaped motion path units arranged in a repetitive manner.

[0007] In one or more embodiments of the present invention, the welding laser oscillates about the axis of symmetry to form a motion path, which is composed of a plurality of "O"-shaped motion path units arranged in a repetitive manner.

[0008] In one or more embodiments of the present invention, the welding laser oscillates about the axis of symmetry to form a motion path, which is composed of a plurality of "8"-shaped motion path units arranged in a repetitive manner.

[0009] In one or more embodiments of the present invention, the fiber laser employs a wobbling welding head, and the welding parameters are set as follows: the spot diameter is between 0.3mm and 0.5mm; the wobbling frequency is between 50Hz and 200Hz; and the wobbling diameter is between 0.8mm and 2.00mm.

[0010] In one or more embodiments of the present invention, the peak power of the welding laser is between 1.5kW and 3.5kW.

[0011] In one or more embodiments of the present invention, the emission frequency of the welding laser is between 10Hz and 20Hz, and the duty cycle is between 70% and 90%.

[0012] In one or more embodiments of the present invention, the welding speed is between 2 m / min and 5 m / min; the welding process is carried out with a protective gas, the flow rate of which is between 10 L / min and 25 L / min.

[0013] In one or more embodiments of the present invention, the thickness of the Al-Si die-cast aluminum alloy plate is between 1.0 mm and 3.0 mm.

[0014] In one or more embodiments of the present invention, it further includes:

[0015] Two Al-Si die-cast aluminum alloy plates were selected; the oxide layer on the surface of the two aluminum alloy plates was removed by mechanical or chemical methods.

[0016] The two processed aluminum alloy plates are fixed to the workbench, and a welded structure is formed between the two aluminum alloy plates.

[0017] Compared with existing technologies, the aluminum alloy laser weld porosity suppression method of the present invention uses a square-wave modulated laser to shorten the keyhole existence time during welding, and coupled with a oscillating laser to synergistically improve keyhole stability, fundamentally suppressing the formation of keyhole-type porosity. The coupled welding laser increases the convection intensity of the molten pool, promoting the escape of hydrogen bubbles from the molten pool, thereby reducing the possibility of hydrogen bubbles being captured by the solidification front, achieving the purpose of suppressing porosity in Al-Si die-cast aluminum alloy welds. In addition, this method has a simple equipment structure and low production cost. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of a method for suppressing porosity in laser welds of aluminum alloys according to an embodiment of the present invention;

[0020] Figure 2 This is a diagram showing the porosity distribution characteristics of the weld cross-section and longitudinal section of the C611 aluminum alloy plate in Example 1 of this invention; wherein, (a) the porosity morphology distribution of the weld cross-section and longitudinal section; (b) the distribution of porosity diameter ≥0.2mm in the longitudinal section of the weld and the statistical results of porosity in the longitudinal section of the weld;

[0021] Figure 3 This is a diagram showing the porosity distribution characteristics of the weld cross-section and longitudinal section of the C611 aluminum alloy plate in Comparative Example 1 of an embodiment of the present invention; wherein, (a) the porosity morphology distribution of the weld cross-section and longitudinal section; (b) the distribution of porosity diameter ≥0.2mm in the longitudinal section of the weld and the statistical results of porosity in the longitudinal section of the weld;

[0022] Figure 4 This is a diagram showing the porosity distribution characteristics of the weld cross-section and longitudinal section of the ADC12 aluminum alloy plate in Example 2 of this invention; wherein, (a) the porosity morphology distribution of the weld cross-section and longitudinal section; (b) the distribution of porosity diameter ≥0.2mm in the longitudinal section of the weld and the statistical results of porosity in the longitudinal section of the weld;

[0023] Figure 5 This is a diagram showing the porosity distribution characteristics of the weld cross-section and longitudinal section of the ADC12 aluminum alloy plate in Comparative Example 2 of an embodiment of the present invention; wherein, (a) the porosity morphology distribution of the weld cross-section and longitudinal section; (b) the distribution of porosity diameter ≥0.2mm in the longitudinal section of the weld and the statistical results of porosity in the longitudinal section of the weld;

[0024] Figure 6 This is a diagram showing the porosity distribution characteristics of the weld cross-section and longitudinal section of the ADC12 aluminum alloy plate in Example 3 of this invention; wherein, (a) the porosity morphology distribution of the weld cross-section and longitudinal section; (b) the distribution of porosity diameter ≥0.2mm in the longitudinal section of the weld and the statistical results of porosity in the longitudinal section of the weld;

[0025] Figure 7 This is a diagram showing the porosity distribution characteristics of the weld cross-section and longitudinal section of the ADC12 aluminum alloy plate in Comparative Example 3 of an embodiment of the present invention; wherein, (a) the porosity morphology distribution of the weld cross-section and longitudinal section; (b) the distribution of porosity diameter ≥0.2mm in the longitudinal section of the weld and the statistical results of porosity in the longitudinal section of the weld;

[0026] Figure 8 This is a waveform diagram of modulated laser in one embodiment of the present invention;

[0027] Figure 9 This is a schematic diagram of the welding laser path in one embodiment of the present invention. Detailed Implementation

[0028] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0029] like Figure 1 As shown, an embodiment of the present invention provides a method for suppressing porosity in aluminum alloy laser welds, which includes steps S1-S3.

[0030] Step S1: Select two Al-Si die-cast aluminum alloy plates; remove the oxide layer from the surface of the two aluminum alloy plates.

[0031] Specifically, in step S1, firstly, two Al-Si die-cast aluminum alloy plates are selected. Then, the oxide layer on the surface of the two aluminum alloy plates can be removed using chemical or mechanical methods. The oxide layer absorbs moisture and contains insoluble substances, and since aluminum alloy plates have high thermal conductivity, welding can easily lead to non-fusion. Furthermore, after removing the oxide layer, acetone or alcohol can be used to remove oil stains from the surface of the aluminum alloy plates, and they can be dried before use. The thickness of the Al-Si die-cast aluminum alloy plates is between 1.0 mm and 3.0 mm.

[0032] Step S2: Fix the two processed aluminum alloy plates to the workbench, forming a welded structure between the two aluminum alloy plates.

[0033] Specifically, in step S2, two processed aluminum alloy plates are placed on the worktable in a spliced ​​manner and fixed with welding fixtures, forming a welded structure between the two aluminum alloy plates. The welding laser can then weld along the welded structure.

[0034] Step S3: A fiber laser is used to couple a oscillating laser and a square wave modulated laser to form a welding laser, which is then used to weld the structure.

[0035] Specifically, in step S3, a fiber laser is used to couple a oscillating laser and a square-wave modulated laser to form a welding laser, and a servo motor is used to control the scanning lens inside the laser focusing lens to set different oscillation trajectories for the welding laser. During welding, the welding laser advances along an axis parallel to the welding direction and oscillates back and forth on both sides of the axis, forming a tortuous motion path, with the oscillation amplitude being the same on both sides of the axis. For example... Figure 8 As shown, the duty cycle of the square wave modulated laser is set so that the welding laser has no laser output at the trough of the motion path.

[0036] In one embodiment, the welding laser oscillates about an axis parallel to the welding direction to form a motion path. For example... Figure 9 As shown, the motion path is an "O" shaped trajectory that moves along the welding direction at a set welding speed. Additionally, the motion path can also move along the welding direction at a set welding speed in "∞" and "8" shaped patterns. The motion path can also be formed by repeating motion path units of other different shapes, and is not limited to the three motion paths mentioned above.

[0037] Furthermore, the fiber laser employs a oscillating welding head with the following welding parameters: the spot diameter is between 0.3mm and 0.5mm. Compared to annular spots, spot welding is more efficient. The oscillation frequency is between 50Hz and 200Hz; the oscillation diameter is between 0.8mm and 2.00mm. The selection of oscillation frequency and diameter increases the keyhole's movement speed, thereby improving keyhole stability and its stirring effect, reducing the possibility of keyhole instability and collapse, and enhancing molten pool convection, thus suppressing porosity.

[0038] To achieve intermittent laser output for welding, the laser's output frequency is between 10Hz and 20Hz, with a duty cycle between 70% and 90%. The peak power of the welding laser is between 1.5kW and 3.5kW. Compared to continuous and sawtooth lasers, the intermittent output of modulated lasers increases the temperature gradient of the molten pool, thereby enhancing the Marangoni force driving the molten pool flow and strengthening convection. The square-wave modulated laser has no laser output at its troughs, eliminating laser-induced keyhole formation and reducing the keyhole duration during welding, thus lowering the probability of keyhole collapse. Simultaneously, the stirring effect of the welding laser oscillating at high speed along a set trajectory synergistically enhances keyhole stability and molten pool convection intensity, further suppressing porosity.

[0039] During welding, the welding speed is controlled between 2 m / min and 5 m / min, which can be matched with the laser power to obtain a well-formed weld. Additionally, a shielding gas can be used during welding. The shielding gas can be, for example, argon. The flow rate of the shielding gas is between 10 L / min and 25 L / min.

[0040] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0041] Example 1

[0042] Two 3.0mm thick C611 die-cast aluminum alloy plates with a hydrogen content of 2.0ppm were selected. The oxide layer was removed mechanically, and the surface oil was removed with acetone and then dried before use.

[0043] The processed aluminum alloy plates are placed on the workbench in a splicing manner, forming a welded structure between the two aluminum alloy plates.

[0044] A modulated laser mode coupled with a oscillating laser from a CWX-3000 fiber laser was used for laser welding of the structure. The peak power of the welding laser was 2.0 kW, the average power was 1.6 kW, the output frequency was 10 Hz, and the duty cycle was 80%. The oscillation trajectory was "O" shaped, the oscillation frequency was 50 Hz, and the oscillation diameter was 1.0 mm. The welding speed was 2.0 m / min, the shielding gas was argon, and the gas flow rate was 20 L / min.

[0045] The porosity distribution of the weld in Example 1 was inspected according to the standard of ISO 13919-2:2001 Guidelines for Classification of Defects in Electron Beam and Laser Welded Joints Part 2: Aluminum and Aluminum Alloys. Figure 2 As shown, the test results show that the weld porosity reaches 3.0%, meeting the highest level (B grade) weld porosity defect requirement of the international standard.

[0046] Comparative Example 1

[0047] Two 3.0mm thick C611 die-cast aluminum alloy plates with a hydrogen content of 2.0ppm were selected. The oxide layer was removed mechanically, and the surface oil was removed with acetone and then dried before use.

[0048] The processed aluminum alloy plates are placed on the workbench in a splicing manner, forming a welded structure between the two aluminum alloy plates.

[0049] The CWX-3000 fiber laser was used in continuous laser mode for laser welding of the structure. The average laser power was 1.6kW and the welding speed was 2.0m / min. The shielding gas was argon with a flow rate of 20L / min.

[0050] The porosity distribution of the weld in Comparative Example 1 was detected according to the method of Example 1. Figure 3 As shown, the test results indicate that millimeter-level and dense porosity exist in the weld, with a porosity of 10.8%, which does not meet the minimum standard D level stipulated by international standards.

[0051] Example 2:

[0052] Two 3.0mm thick ADC12 die-cast aluminum alloy plates with a hydrogen content of 1.8ppm were selected. The oxide layer was removed mechanically, and the surface oil was removed with acetone and then dried before use.

[0053] The processed aluminum alloy plates are placed on the workbench in a splicing manner, forming a welded structure between the two aluminum alloy plates.

[0054] A modulated laser mode coupled with a oscillating laser from a CWX-3000 fiber laser was used for laser welding of the structure. The peak power of the welding laser was 2.4 kW, the duty cycle was 80%, the average power was 1.9 kW, and the frequency was 10 Hz. The oscillation trajectory was "O" shaped, the oscillation frequency was 100 Hz, and the oscillation diameter was 1.0 mm. The welding speed was 2.4 m / min, the shielding gas was argon, and the gas flow rate was 20 L / min.

[0055] The porosity distribution of the weld in Example 2 was detected according to the method of Example 1. Figure 4 As shown, the test results show that the porosity reaches 2.3%, meeting the Class B standard stipulated by international standards.

[0056] Comparative Example 2

[0057] Two 3.0mm thick ADC12 die-cast aluminum alloy plates with a hydrogen content of 1.8ppm were selected. The oxide layer was removed mechanically, and the surface oil was removed with acetone and then dried before use.

[0058] The processed aluminum alloy plates are placed on the workbench in a splicing manner, forming a welded structure between the two aluminum alloy plates.

[0059] The CWX-3000 fiber laser was used in continuous laser mode for laser welding of the structure. The laser power was 1.9kW, the welding speed was 2.4m / min, the shielding gas was argon, and the gas flow rate was 15L / min.

[0060] The porosity distribution of the weld in Comparative Example 2 was detected according to the method of Example 1. Figure 5 As shown, the test results indicate that millimeter-sized and densely packed pores exist in the weld, with a porosity of 5.8%, which only meets the Class D standard stipulated by international standards.

[0061] Example 3

[0062] Two 3.0mm thick ADC12 die-cast aluminum alloy plates with a hydrogen content of 2.5ppm were selected. The oxide layer was removed mechanically, and the surface oil was removed with acetone and then dried before use.

[0063] The processed aluminum alloy plates are placed on the workbench in a splicing manner, forming a welded structure between the two aluminum alloy plates.

[0064] Laser welding of the structure was performed using a modulated laser coupled with a oscillating laser from a CWX-3000 laser. The modulated laser had a peak power of 3.0 kW, a duty cycle of 80%, an average power of 2.4 kW, and a frequency of 20 Hz. The oscillation trajectory was "O"-shaped, with an oscillation frequency of 150 Hz and an oscillation diameter of 1.0 mm. The welding speed was 2.4 m / min, and the shielding gas was argon with a flow rate of 20 L / min.

[0065] The porosity distribution of the weld in Example 3 was detected according to the method of Example 1. Figure 6 As shown, the test results show that the porosity is only 0.4%, which meets the Class B standard stipulated by international standards.

[0066] Comparative Example 3

[0067] Two 3.0mm thick ADC12 die-cast aluminum alloy plates with a hydrogen content of 2.5ppm were selected. The oxide layer was removed mechanically, and the surface oil was removed with acetone and then dried before use.

[0068] The processed aluminum alloy plates are placed on the workbench in a splicing manner, forming a welded structure between the two aluminum alloy plates.

[0069] The CWX-3000 fiber laser was used in continuous laser mode for laser welding of the structure. The laser power was 2.4kW, the welding speed was 3.0m / min, the shielding gas was argon, and the gas flow rate was 15L / min.

[0070] The porosity distribution of the weld in Comparative Example 3 was detected according to the method of Example 1. Figure 7 As shown, the test results indicate that dense porosity exists in the weld, reaching 9.5%, which meets the Class D standard stipulated by international standards.

[0071] In summary, the aluminum alloy laser weld porosity suppression method of the present invention uses a square-wave modulated laser to shorten the keyhole existence time during welding, and coupled with a oscillating laser to synergistically improve keyhole stability, fundamentally suppressing keyhole-type porosity formation. The coupled welding laser increases the convection intensity of the molten pool, promoting the escape of hydrogen bubbles within the molten pool, thereby reducing the possibility of hydrogen bubbles being captured by the solidification front, achieving the purpose of suppressing porosity in Al-Si die-cast aluminum alloy welds. Furthermore, this method features a simple equipment structure and low production cost.

[0072] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0073] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for suppressing porosity in laser welds of aluminum alloys, characterized in that, include: A fiber laser is used to couple a oscillating laser and a square-wave modulated laser to form a welding laser, which is then used to weld two Al-Si die-cast aluminum alloy plates. During the welding process, the welding laser advances along an axis parallel to the welding direction and oscillates back and forth on both sides of the axis, forming a tortuous motion path. The duty cycle of the square-wave modulated laser is set so that there is no laser output at the trough of the motion path. The output frequency of the welding laser is between 10Hz and 20Hz, and the duty cycle is between 70% and 90%.

2. The method for suppressing porosity in laser welds of aluminum alloys according to claim 1, characterized in that, The welding laser oscillates about the axis of symmetry to form a motion path, which is composed of multiple "∞" shaped motion path units arranged in a repetitive manner.

3. The method for suppressing porosity in aluminum alloy laser welds according to claim 1, characterized in that, The welding laser oscillates about the axis of symmetry to form a motion path, which is composed of multiple "O"-shaped motion path units arranged in a repetitive manner.

4. The method for suppressing porosity in laser welds of aluminum alloys according to claim 1, characterized in that, The welding laser oscillates about the axis of symmetry to form a motion path, which is composed of multiple "8" shaped motion path units arranged in a repetitive pattern.

5. The method for suppressing porosity in laser welds of aluminum alloys according to claim 1, characterized in that, The fiber laser uses a wobbling welding head, and the welding parameters are set as follows: spot diameter between 0.3mm and 0.5mm; wobbling frequency between 50Hz and 200Hz; and wobbling diameter between 0.8mm and 2.00mm.

6. The method for suppressing porosity in laser welds of aluminum alloys according to claim 1, characterized in that, The peak power of the welding laser is between 1.5kW and 3.5kW.

7. The method for suppressing porosity in laser welds of aluminum alloys according to claim 1, characterized in that, The welding speed is between 2 m / min and 5 m / min; a shielding gas is used during the welding process, and the flow rate of the shielding gas is between 10 L / min and 25 L / min.

8. The method for suppressing porosity in aluminum alloy laser welds according to claim 1, characterized in that, The thickness of the Al-Si die-cast aluminum alloy plate is between 1.0 mm and 3.0 mm.

9. The method for suppressing porosity in laser welds of aluminum alloys according to claim 1, characterized in that, Also includes: Two Al-Si die-cast aluminum alloy plates were selected; the oxide layer on the surface of the two aluminum alloy plates was removed by mechanical or chemical methods. The two processed aluminum alloy plates are fixed to the workbench, and a welded structure is formed between the two aluminum alloy plates.

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