Heat-treatment-free die-casting aluminum alloy welding method based on laser oscillation technology

Abstract

The invention discloses a heat-treatment-free die-casting aluminum alloy welding method based on a laser oscillation technology. The heat-treatment-free die-casting aluminum alloy welding method comprises the steps that firstly, a to-be-welded plate is pretreated; the to-be-welded plate is a heat-treatment-free die-casting aluminum alloy plate; secondly, the to-be-welded plate is clamped through a clamp, the position of a laser oscillation welding head is adjusted, and an included angle is formed between the axis of a laser beam and the vertical line direction of the to-be-welded plate; thirdly, the laser oscillation welding head emits an oscillation laser beam to weld the plate to be welded, the oscillation frequency of the oscillation laser beam ranges from 50 Hz to 200 Hz, and the oscillation amplitude ranges from 5 mm to 7 mm; and fourthly, after solution treatment, water quenching and aging treatment are conducted on the welded plate, the welded plate is cooled to the room temperature. According to the heat-treatment-free die-casting aluminum alloy welding method based on the laser oscillation technology, the problems that in the heat-treatment-free die-casting aluminum alloy welding process, welding seams collapse, the porosity is high, and the second phase is thick can be solved, and the welding quality of the heat-treatment-free die-casting aluminum alloy is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment-free die-casting aluminum alloy welding, and in particular relates to a heat treatment-free die-casting aluminum alloy welding method based on laser oscillation technology. Background Art

[0002] The integrated die-casting process has become one of the disruptive technologies in the automotive industry. Compared with traditional processes, one-step forming has a natural advantage in saving manufacturing costs. In 2020, Tesla first applied an integrated die-cast rear floor to the Model Y, and in 2023, Huawei's M9 model used the world's largest integrated die-cast body. The common problems faced by integrated die-casting parts in production applications are part deformation and surface blistering caused by heat treatment, as well as the expensive transportation costs of oversized die-casting parts.

[0003] Heat-treatment-free die-casting aluminum alloy is a new type of die-casting material developed on the basis of traditional die-casting aluminum alloy. It can directly obtain good comprehensive performance without heat treatment, and effectively avoid the adverse effects of heat treatment on part performance.

[0004] In the current market, mechanical connection is still the common connection method for aluminum alloy materials. This is because the characteristics of aluminum alloy materials, especially die-cast aluminum alloy materials, lead to many problems in the welding process of such materials. Die-cast aluminum alloys contain more strengthening phase elements, forming a large number of low-melting eutectic structures. In the welded joints, the low-melting eutectic structures are connected to each other in sheets, which easily cause cracks in the weld during welding, reducing the strength of the welded joint. In addition, the most common phenomenon in aluminum alloy welds is the presence of welding pores. Taking laser as an example, because the reflectivity of the aluminum alloy surface to the laser is high, a large laser power is usually required to achieve effective welding. However, due to the low surface tension of the aluminum melt and the poor anti-interference ability of the small holes formed by the high-power laser, the small holes are prone to collapse and form pores. At the same time, the concentrated heat source commonly used in fusion welding will cause the energy density in the center of the weld to be higher than that on both sides of the weld, which is easy to cause weld collapse or undercut.

[0005] The development of high-quality welding technology between heat-treatment-free die-casting aluminum alloy materials can effectively control the huge transportation costs of super-large integrated die-casting parts, which is of great significance for the flexible application of integrated die-casting technology in industry.

[0006] Patent No. CN 116727864A (hereinafter referred to as Patent Document 1) and Patent No. CN 116713597A (hereinafter referred to as Patent Document 2) both provide a composite welding method for connecting die-cast aluminum alloys.

[0007] Patent Document 1 uses laser-arc hybrid welding technology to achieve die-cast aluminum alloy battery pack tray welding, expands the molten pool and increases the welding speed. Patent Document 2 uses a special welding wire independently developed to achieve laser-MIG hybrid welding and laser-CMT hybrid welding of die-cast aluminum alloys, which can significantly improve the strength of the welded joint.

[0008] However, Patent Documents 1 and 2 have the following problems: special welding wires need to be developed according to die-casting materials, and the wire feeding system and the laser beam need to be precisely matched to achieve welding, which increases production costs and technical requirements. Moreover, hybrid welding uses a laser-arc composite heat source, and the welding heat source still has the highest energy density in the center and lower energy density at the edge, which can easily cause weld collapse or undercut after welding, and also easily produce a large piece of low-melting eutectic structure in the center of the weld due to the relatively higher heat input in the center of the weld. Summary of the invention

[0009] The present invention provides a heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology, which can overcome the problems of weld collapse, high porosity, coarse second phase, etc. that occur during the heat treatment-free die-cast aluminum alloy welding process, and improve the welding quality of the heat treatment-free die-cast aluminum alloy.

[0010] The technical solution provided by the present invention is:

[0011] A heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology comprises the following steps:

[0012] Step 1: Pre-treat the plate to be welded;

[0013] Wherein, the plate to be welded is a heat-treatment-free die-cast aluminum alloy plate;

[0014] Step 2: Clamp the plate to be welded with a fixture, and adjust the position of the laser oscillation welding head so that the axis of the laser beam has an angle with the vertical direction of the plate to be welded;

[0015] Step 3: The laser oscillation welding head emits an oscillating laser beam to weld the plate to be welded, the oscillation frequency of the oscillating laser beam is 50 Hz to 200 Hz, and the oscillation amplitude is 5 mm to 7 mm;

[0016] Step 4: After solution treatment, water quenching and aging treatment, the welded plates are cooled to room temperature.

[0017] Preferably, in step 1, the method for pre-treating the plate to be welded is: grinding the plate to be welded to remove surface oxides, and then cleaning the surface oil stains of the plate to be welded with acetone.

[0018] Preferably, the plates to be welded are placed in a flat plate overlap manner with an overlap amount of 25 mm to 30 mm.

[0019] Preferably, in step 2, the angle between the axis of the laser beam and the perpendicular direction of the plate to be welded is 8° to 12°.

[0020] Preferably, in the step three, the oscillation mode of the oscillating laser beam is a sinusoidal oscillation mode.

[0021] Preferably, in step three, the laser power of the oscillating laser beam is 3.7KW to 4.3KW, the welding speed is 48mm / s to 55mm / s, and the defocus amount is 0mm.

[0022] Preferably, in step 4, the solution temperature is 450° C. to 540° C., and the solution time is 4 h to 4.5 h.

[0023] Preferably, in step 4, the aging treatment temperature is 180° C. to 220° C., and the aging time is 2.5 h to 3 h.

[0024] The beneficial effects of the present invention are:

[0025] The heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology provided by the present invention can optimize the spatial configuration of heat source energy and introduce strong stirring effect through oscillating laser beam, thereby avoiding problems such as weld porosity, high thermal cracking tendency, weld collapse caused by keyhole collapse and uneven distribution of heat source energy; the solid solution and aging heat treatment after laser oscillation welding can effectively eliminate the layered structure and composition segregation, and enhance the tensile shear performance of the weld joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the welding state of the heat treatment-free die-cast aluminum alloy welding method based on laser oscillation provided by the present invention.

[0027] Figure 2 Schematic diagram of the principle of improving weld porosity using laser oscillation technology.

[0028] Figure 3 Schematic diagram of the principle of improving weld structure using laser oscillation technology.

[0029] Figure 4 (a) is the macroscopic morphology of the weld obtained in Example 1 of the present invention.

[0030] Figure 4 (b) is the macroscopic morphology of the weld obtained in Example 2 of the present invention.

[0031] Figure 4 (c) is the weld macroscopic morphology obtained in Example 3 of the present invention.

[0032] Figure 4(d) is the macroscopic morphology of the weld obtained in Example 4 of the present invention.

[0033] Figure 5 (a1) is a metallographic image of the fusion line on the upper plate side of the weld obtained in Example 1 of the present invention. Figure 5 (b1) is the metallographic image of the weld center obtained in Example 1 of the present invention.

[0034] Figure 5 Where (c1) is Figure 5 Enlarged view of (b1).

[0035] Figure 5 (d1) is a metallographic image of the fusion line on the lower plate side of the weld obtained in Example 1 of the present invention.

[0036] Figure 5 (a2) is a metallographic image of the fusion line on the upper plate side of the weld obtained in Example 2 of the present invention.

[0037] Figure 5 (b2) is the metallographic image of the weld center obtained in Example 2 of the present invention.

[0038] Figure 5 In (c2) Figure 5 Enlarged view of (b2).

[0039] Figure 5 (d2) is a metallographic image of the fusion line on the lower plate side of the weld obtained in Example 2 of the present invention.

[0040] Figure 5 (a3) is a metallographic image of the fusion line on the upper plate side of the weld obtained in Example 3 of the present invention.

[0041] Figure 5 (b3) is the metallographic image of the weld center obtained in Example 3 of the present invention.

[0042] Figure 5 In (c3) Figure 5 Enlarged view of (b3).

[0043] Figure 5 (d3) is a metallographic image of the fusion line on the lower plate side of the weld obtained in Example 3 of the present invention.

[0044] Figure 5 (a4) is a metallographic image of the fusion line on the upper plate side of the weld obtained in Example 4 of the present invention.

[0045] Figure 5 (b4) is the metallographic image of the weld center obtained in Example 4 of the present invention.

[0046] Figure 5 In (c4) Figure 5 Enlarged view of (b4).

[0047] Figure 5 (d4) is a metallographic image of the fusion line on the lower plate side of the weld obtained in Example 4 of the present invention.

[0048] Figure 6 (a1) is an electronic scanning image of the weld center obtained in Example 1 of the present invention. Figure 6 (b1) is the Si element distribution diagram of the weld center obtained in Example 1 of the present invention.

[0049] Figure 6 (c1) is the Mn element distribution diagram of the weld center obtained in Example 1 of the present invention.

[0050] Figure 6 (d1) is the Mg element distribution diagram of the weld center obtained in Example 1 of the present invention.

[0051] Figure 6 (a2) is an electronic scanning image of the weld center obtained in Example 2 of the present invention. Figure 6 (b2) is the Si element distribution diagram of the weld center obtained in Example 2 of the present invention.

[0052] Figure 6 (c2) is the Mn element distribution diagram of the weld center obtained in Example 2 of the present invention.

[0053] Figure 6 (d2) is the Mg element distribution diagram of the weld center obtained in Example 2 of the present invention.

[0054] Figure 6 (a3) is an electronic scanning image of the weld center obtained in Example 3 of the present invention. Figure 6 (b3) is the Si element distribution diagram of the weld center obtained in Example 3 of the present invention.

[0055] Figure 6 (c3) is the Mn element distribution diagram of the weld center obtained in Example 3 of the present invention.

[0056] Figure 6 (d3) is the Mg element distribution diagram of the weld center obtained in Example 3 of the present invention.

[0057] Figure 6 (a4) is an electronic scanning image of the weld center obtained in Example 4 of the present invention. Figure 6 (b4) is the Si element distribution diagram of the weld center obtained in Example 4 of the present invention.

[0058] Figure 6 (c4) is the Mn element distribution diagram of the weld center obtained in Example 4 of the present invention.

[0059] Figure 6 (d4) is the Mg element distribution diagram of the weld center obtained in Example 4 of the present invention.

[0060] Figure 7 This is the macroscopic morphology of the weld obtained in Comparative Example 1 of the present invention.

[0061] Figure 8 (a) is a metallographic image of the fusion line on the lower plate side of the weld obtained in Comparative Example 1 of the present invention.

[0062] Figure 8 (b) is a metallographic image of the weld center obtained in Comparative Example 1 of the present invention.

[0063] Figure 8 (c) is a metallographic image of the fusion line on the upper plate side of the weld obtained in Comparative Example 1 of the present invention.

[0064] Figure 8 (d) is Figure 8 Enlarged view of (b).

[0065] Fig. 9 (a) is an electronic scanning image of the weld center obtained in Comparative Example 1 of the present invention.

[0066] Fig. 9 (b) is the Si element distribution diagram of the weld center obtained in Comparative Example 1 of the present invention.

[0067] Fig. 9 (c) is the Mn element distribution diagram of the weld center obtained in Comparative Example 1 of the present invention.

[0068] Fig. 9 (d) is the Mg element distribution diagram of the weld center obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0069] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0070] like Figure 1 As shown, the present invention provides a heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology, and the specific implementation process is as follows.

[0071] 1. Pretreatment of the plates to be welded

[0072] Use sandpaper and angle grinder to grind the plates to be welded to remove the oxide film on the surface of the plates to be welded, and then use acetone to wipe off the oil stains on the surface of the plates to be welded to give them a metallic luster.

[0073] Wherein, the plate to be welded is a die-cast aluminum alloy plate that does not require heat treatment.

[0074] Second, the plates to be welded are clamped with a fixture, and the position of the laser oscillation welding head is adjusted so that the axis of the laser beam forms an angle with the vertical direction of the plates to be welded.

[0075] Among them, the placement method of the plates to be welded is flat plate overlap, and the overlap amount is 25mm to 30mm.

[0076] Since the plate to be welded (die-cast aluminum alloy plate without heat treatment) has a high reflection intensity of the laser beam, setting an angle between the axis of the laser beam and the perpendicular direction of the plate to be welded can ensure that the laser beam will not directly return and damage the laser generator after reflection.

[0077] As a preference, the angle between the axis of the laser beam and the perpendicular direction of the plate to be welded is set to 8° to 12°.

[0078] 3. The laser oscillation welding head emits an oscillating laser beam to weld the plate to be welded, and the oscillation frequency of the oscillating laser beam is 50Hz to 200Hz, and the oscillation amplitude is 5mm to 7mm. The laser oscillation welding system used in the present invention is composed of a laser generator and a scanning laser head, wherein the scanning laser head is composed of a collimation unit, a focusing unit, and a beam deflector. After passing through the collimation unit, the laser beam is incident on two beam deflectors equipped with reflectors, and the beam deflector can be rotated along the X and Y axes, so that the beam can be deflected in any direction; after passing through the focusing unit, the laser can emit the laser to various parts of the workpiece surface, so as to achieve the purpose of laser welding along a periodic scanning trajectory on the workpiece surface.

[0079] It has been verified that when the oscillation frequency is controlled at 50Hz to 200Hz and the oscillation amplitude is 5mm to 7mm, a higher quality weld can be obtained. When the oscillation frequency of the laser beam is higher than 200Hz, it is easy to cause serious stratification, resulting in a decrease in elongation. When the oscillation frequency of the laser beam is lower than 50Hz, the advantage of optimizing the organization is not obvious. When the laser amplitude is too large, it is easy to cause excessive agitation and lead to stratification. If it is too low, it cannot effectively heat the side wall of the weld.

[0080] The oscillation mode of the oscillating laser beam is a sinusoidal oscillation mode. The sinusoidal scanning route ensures that the laser beam will not continuously advance along the welding direction on any parallel line of the weld, so the laser energy is averaged in the direction perpendicular to the weld, and only slightly increases at the laser beam speed zero at the two sides of the weld.

[0081] As the oscillation frequency increases, the movement speed of the small holes generated by the laser beam inside the molten pool increases. High-speed movement helps to improve the anti-interference ability of the small holes and reduce the possibility of pores. The high-speed oscillation of the laser beam also introduces a strong stirring effect to the molten pool, driving the high-speed flow of the melt, accelerating the discharge of internal gas while forming a uniform temperature field and material field inside the molten pool, thereby transforming the coarse continuous line of low-melting-point eutectic phase into a spider web shape, and reducing the tendency of thermal cracks.

[0082] As a preferred embodiment, the laser power of the oscillating laser beam is 3.7KW to 4.3KW, the welding speed is 48mm / s to 55mm / s, and the defocus is 0mm.

[0083] It has been verified that the laser power of the oscillating laser beam is 3.7KW~4.3KW, the welding speed is 48mm / s~55mm / s, and the defocus is 0mm, which can achieve better welding results. When the laser power is higher than 4.3KW, it is easy to cause low-melting-point elements to burn; when the laser power is lower than 3.7KW, it is easy to cause reduced welding efficiency. When the welding speed is greater than 55mm / s, it is easy to cause local heat input to be too low, resulting in defects such as unfused and undercut; when the welding speed is less than 48mm / s, it is easy to limit the welding efficiency. If the defocus is too large, the laser power density will decrease, and if it is too small, the power density will be too high, which is easy to cause surface burning.

[0084] like Figure 2 As shown in the figure, compared with the conventional laser welding process, high-frequency oscillation provides a strong stirring effect for the weld pool. On the one hand, the higher anti-interference ability of the high-speed laser keyhole reduces the gas generation. On the other hand, the stirring effect drives the melt flow and promotes the gas discharge outside the molten pool, so the porosity inside the weld is reduced. Figure 3 As shown in the figure, the high-speed oscillation of the laser beam introduces a strong stirring effect, which drives the high-speed flow of the melt, accelerates the discharge of internal gas, and forms a uniform temperature field and material field inside the molten pool, thereby transforming the coarse continuous linear low-melting point eutectic phase into fine dispersed particles, reducing the tendency of thermal cracks, and the second phase also transforms from an aggregated coarse phase to a uniformly dispersed fine phase.

[0085] 4. After solution treatment, water quenching and aging treatment, the welded plates are cooled to room temperature by air cooling.

[0086] As a preferred embodiment, the solution temperature is 450°C to 540°C, the solution time is 4h to 4.5h, the aging treatment temperature is 180°C to 220°C, and the aging time is 2.5h to 3h.

[0087] Solid solution and aging treatment can promote recrystallization, improve the internal structure stratification and composition segregation of laser oscillation welding, and further enhance the tensile shear performance while maintaining the advantages of laser oscillation welding.

[0088] Example 1

[0089] The surface of the die-cast aluminum alloy plate to be welded without heat treatment is cleaned with sandpaper and an angle grinder to remove oxides and impurities on the surface of the plate to be welded, and then the die-cast aluminum alloy plate to be welded without heat treatment is scrubbed with acetone to reveal the metallic luster.

[0090] Use a fixture to clamp the heat-free die-cast aluminum alloy plate to be welded. The placement method is flat overlap, the overlap is 30mm, the upper plate thickness is 2mm, and the lower plate thickness is 3mm. No inert gas protection is required. Adjust the laser oscillation welding head to ensure that the laser beam axis is at a 10° angle to the vertical direction of the surface of the plate to be welded, and ensure that the laser beam will not directly return to damage the laser generator after reflection. Turn on the laser and use the laser beam to laser weld the plate to be welded. The oscillation mode of the oscillating laser is sinusoidal mode, the oscillation frequency is 50Hz, the amplitude is 5mm, the laser power is 4KW, the welding speed is 50mm / s, and the defocus is 0mm. After welding, the weldment is solution treated at 530℃ for 4h, water quenched, and aged at 200℃ for 2.5h, and then air-cooled to room temperature.

[0091] The internal porosity of the weld obtained in Example 1 is 11.6%. The macroscopic morphology of the cross section of the weld obtained in Example 1 is as follows: Figure 4 As shown in (a), it can be seen that in this embodiment, the laser energy configuration is optimized by oscillating the path, the heat input per unit area is limited, and the weld collapse defect is eliminated. Figure 5 As shown in (a1) to (d1), the partial melting zone (PMZ) is eliminated, and the structure of the upper and lower parts of the weld plate is more consistent. Figure 6 As shown in (a1) to (d1), it can be seen that the number of large-sized blocky second phases in the weld is reduced, the eutectic phase segregation form begins to change from lamellar segregation to network segregation, and the segregation phenomenon of Mg element almost disappears.

[0092] Example 2

[0093] The surface of the heat-free die-cast aluminum alloy to be welded is cleaned with sandpaper and an angle grinder to remove oxides and impurities on the surface of the plate to be welded, and then the heat-free die-cast aluminum alloy to be welded is scrubbed with acetone to reveal the metallic luster.

[0094] Use a fixture to clamp the heat-free die-cast aluminum alloy to be welded. The placement method is flat overlap, the overlap is 30mm, the upper plate thickness is 2mm, and the lower plate thickness is 3mm. No inert gas protection is required. Adjust the laser oscillation welding head to ensure that the laser beam axis is at an angle of 10° to the vertical direction of the surface of the plate to be welded, and ensure that the laser beam will not directly return to damage the laser generator after reflection. Turn on the laser and use the laser beam to laser weld the plate to be welded. The oscillation mode of the oscillating laser is sinusoidal mode, the oscillation frequency is 100Hz, the amplitude is 5mm, the laser power is 4KW, the welding speed is 50mm / s, and the defocus is 0mm. After welding, the weldment is solution treated at 530℃ for 4h, water quenched, aged at 200℃ for 2.5h, and then air-cooled to room temperature.

[0095] The internal porosity of the weld obtained in Example 1 is 8.6%. The macroscopic morphology of the cross section of the weld obtained in Example 2 is as follows: Figure 4 As shown in (b), it can be seen that in this embodiment, the laser energy configuration is optimized by oscillating the path, the heat input per unit area is limited, and the weld collapse defect is eliminated. Figure 5 As shown in (a2) to (d2), the partial melting zone (PMZ) is eliminated, the weld microstructure uniformity increases, the fusion line becomes smoother, and the crystal growth direction begins to grow uniformly. Figure 6 As shown in (a2) to (d2), it can be seen that the number of large-sized blocky second phases in the weld is reduced, the eutectic phase segregation form is transformed from lamellar segregation to network segregation, and the segregation phenomenon of Mg element almost disappears.

[0096] Example 3

[0097] The surface of the die-cast aluminum alloy to be welded without heat treatment is cleaned with sandpaper and an angle grinder to remove oxides and impurities on the surface of the plate to be welded, and then the die-cast aluminum alloy to be welded without heat treatment is scrubbed with acetone to reveal the metallic luster.

[0098] Use a fixture to clamp the heat-free die-cast aluminum alloy plate to be welded. The placement method is flat overlap, the overlap is 30mm, the upper plate thickness is 2mm, and the lower plate thickness is 3mm. No inert gas protection is required. Adjust the laser oscillation welding head to ensure that the laser beam axis is at an angle of 10° to the vertical direction of the surface of the plate to be welded, and ensure that the laser beam will not directly return to damage the laser generator after reflection. Turn on the laser and use the laser beam to laser weld the plate to be welded. The oscillation mode of the oscillating laser is sinusoidal mode, the oscillation frequency is 150Hz, the amplitude is 5mm, the laser power is 4KW, the welding speed is 50mm / s, and the defocus is 0mm. After welding, the weldment is solution treated at 530℃ for 4h, water quenched, aged at 200℃ for 2.5h, and then air-cooled to room temperature.

[0099] The porosity of the weld obtained in Example 3 is 7.1%. The macroscopic morphology of the cross section of the weld obtained in Example 3 is as follows: Figure 4 As shown in (c), it can be seen that in this embodiment, the laser energy configuration is optimized by oscillating the path, the heat input per unit area is limited, and the weld collapse defect is eliminated. Figure 5 As shown in (a3) ​​to (d3), the partial melting zone (PMZ) is eliminated, the upper and lower parts of the weld plate have more consistent structures, the fusion line becomes smoother, the crystal growth direction begins to grow uniformly, and the proportion of equiaxed grains in the center of the weld increases. Figure 6 As shown in (a3) ​​to (d3), it can be seen that a large number of large-sized blocky second phases in the weld disappear, the eutectic phase segregation form changes from lamellar segregation to network segregation, and the segregation phenomenon of Mn and Mg elements almost disappears.

[0100] Example 4

[0101] The surface of the die-cast aluminum alloy to be welded without heat treatment is cleaned with sandpaper and an angle grinder to remove oxides and impurities on the surface of the plate to be welded, and then the die-cast aluminum alloy to be welded without heat treatment is scrubbed with acetone to reveal the metallic luster.

[0102] Use a fixture to clamp the heat-free die-cast aluminum alloy plate to be welded. The placement method is flat overlap, the overlap is 30mm, the upper plate thickness is 2mm, and the lower plate thickness is 3mm. No inert gas protection is required. Adjust the laser oscillation welding head to ensure that the laser beam axis is at an angle of 10° to the vertical direction of the surface of the plate to be welded, and ensure that the laser beam will not directly return to damage the laser generator after reflection. Turn on the laser and use the laser beam to laser weld the plate to be welded. The oscillation mode of the oscillating laser is sinusoidal mode, the oscillation frequency is 200Hz, the amplitude is 5mm, the laser power is 4KW, the welding speed is 50mm / s, and the defocus is 0mm. After welding, the weldment is solution treated at 530℃ for 4h, water quenched, aged at 200℃ for 2.5h, and then air-cooled to room temperature.

[0103] The internal porosity of the weld obtained in Example 4 is 5.4%. The macroscopic morphology of the cross section of the weld obtained in Example 4 is as follows: Figure 4 As shown in (d), the laser energy configuration is optimized by oscillating the path, limiting the heat input per unit area and eliminating the weld collapse defect. Figure 5 As shown in (a4) to (d4), the partial melting zone (PMZ) is eliminated, the upper and lower parts of the weld plate have more consistent structures, the fusion line becomes smoother, the crystal growth direction begins to grow uniformly, the proportion of equiaxed grains in the center of the weld increases, and stratification can be observed. After solution aging treatment, the stratification phenomenon in the weld disappears. The SEM image of the weld is shown in Figure 6As shown in (a4) to (d4), a large number of large-sized blocky second phases in the weld disappear, the segregation phenomenon of the eutectic phase is eliminated, the eutectic phase elements are evenly distributed, and the segregation phenomenon of Mn and Mg elements almost disappears.

[0104] Comparative Example 1

[0105] The surface of the heat-free die-cast aluminum alloy to be welded is cleaned with sandpaper and an angle grinder to remove oxides and impurities on the surface of the plate to be welded, and then the heat-free die-cast aluminum alloy to be welded is scrubbed with acetone to reveal the metallic luster. The heat-free die-cast aluminum alloy to be welded is clamped with a clamp, and the placement method is flat overlap, the overlap amount is 30mm, the upper plate thickness is 2mm, and the lower plate thickness is 3mm. No inert gas protection is required. The laser oscillation welding head is adjusted to ensure that the axis of the laser beam is at an angle of 10° to the vertical direction of the surface of the plate to be welded; turn on the laser, and laser weld the plate to be welded by the laser beam. No laser oscillation is added, the laser power is 4KW, the welding speed is 50mm / s, and the defocus is 0mm. After welding, the weldment is solid-solution treated at 530℃ for 4h, aged at 200℃ for 2.5h, and then air-cooled to room temperature.

[0106] After laser welding, the porosity inside the weld is 20.6%. The macroscopic morphology of the weld cross section is as follows: Figure 7 As shown in the figure, due to the excessive heat input per unit area, serious weld collapse defects are caused. Figure 8 As shown in (a) to (d), there is a partial melting zone (PMZ) between the FZ and the HAZ, and the fusion line is tortuous and serrated in some places. Fig. 9 As shown in (a) to (d), it can be seen that there are large-sized blocky precipitates in the weld, and the precipitate elements Si, Fe, Mn, and Mg all have obvious segregation.

[0107] Comparative Example 2

[0108] The surface of the heat-free die-cast aluminum alloy to be welded is cleaned with sandpaper and an angle grinder to remove oxides and impurities on the surface of the plate to be welded, and then the heat-free die-cast aluminum alloy to be welded is scrubbed with acetone to expose the metallic luster. The heat-free die-cast aluminum alloy to be welded is clamped with a clamp, and the placement method is flat overlap, the overlap amount is 30mm, the upper plate thickness is 2mm, and the lower plate thickness is 3mm. No inert gas protection is required. Adjust the laser oscillation welding head to ensure that the laser beam axis is at an angle of 10° to the vertical direction of the surface of the plate to be welded; turn on the laser, and laser weld the plate to be welded by the laser beam. No laser oscillation is added, the laser power is 4KW, the welding speed is 50mm / s, and the defocus is 0mm. After welding, no solid solution treatment is performed. The macroscopic morphology and metallographic diagram of the cross-section of the weld are the same as those of Comparative Example 1, and the element segregation phenomenon is stronger than that of Comparative Example 1.

[0109] By comparing the welding results of Example 1-4 with those of Comparative Example 1-2, it can be seen that Example 1-4 welds the heat-treatment-free die-cast aluminum alloy plates to be welded by laser oscillation method, effectively eliminating weld collapse defects, reducing welding porosity defects, eliminating part of the melting zone, and obtaining a finer and more uniformly oriented crystal structure, a more diffuse and uniform distribution of precipitated phase elements, and a precipitated phase with a more regular morphology and a smaller size.

[0110] The mechanical properties of the welded joints obtained in Examples 1-4 and Comparative Examples 1-2 are shown in Table 1.

[0111] Table 1 Mechanical properties of welded joints obtained in various embodiments and comparative examples

[0112]

[0113] As can be seen from Table 1, the present invention adopts laser oscillation technology to significantly improve the mechanical properties of the heat-treatment-free die-cast aluminum alloy laser welded joint. In the tensile shear test, compared with comparative example 1, the maximum tensile shear load and maximum displacement of Example 4 are increased by 81.4% and 88.5%, respectively; after welding, the mechanical properties of the heat-treatment-free die-cast aluminum alloy laser welded joint are further improved by solid solution and aging treatment.

[0114] In addition, the heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology provided by the present invention also has the advantages of simple equipment modification, no need for additional welding materials and matching tooling, and low technical requirements.

[0115] In summary, the comprehensive performance of the welded joint obtained by the heat-treatment-free die-cast aluminum alloy welding method based on laser oscillation technology provided by the present invention is better than that of the welded joint obtained by the existing conventional laser heat-treatment-free die-cast aluminum alloy welding method without adding laser oscillation. Taking into account the cost, modification difficulty and technical requirements, laser oscillation welding will be a more promising welding method for heat-treatment-free die-cast aluminum alloy welding.

[0116] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology, characterized in that: The steps include: Step 1: Pre-treat the plate to be welded; Wherein, the plate to be welded is a heat-treatment-free die-cast aluminum alloy plate; Step 2: Clamp the plate to be welded with a fixture, and adjust the position of the laser oscillation welding head so that the axis of the laser beam has an angle with the vertical direction of the plate to be welded; Step 3: The laser oscillation welding head emits an oscillating laser beam to weld the plate to be welded, the oscillation frequency of the oscillating laser beam is 50 Hz to 200 Hz, and the oscillation amplitude is 5 mm to 7 mm; Step 4: After solution treatment, water quenching and aging treatment, the welded plates are cooled to room temperature.

2. The heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology according to claim 1 is characterized in that: In the step 1, the method for pre-treating the plate to be welded is: grinding the plate to be welded to remove surface oxides, and then cleaning the oil stains on the surface of the plate to be welded with acetone.

3. The heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology according to claim 2 is characterized in that: The plates to be welded are placed in a flat plate overlap manner with an overlap amount of 25 mm to 30 mm.

4. The heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology according to claim 3 is characterized in that: In the step 2, the angle between the axis of the laser beam and the perpendicular direction of the plate to be welded is 8° to 12°.

5. The heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology according to claim 3 or 4, characterized in that: In the step three, the oscillation mode of the oscillating laser beam is a sinusoidal oscillation mode.

6. The heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology according to claim 5 is characterized in that: In the step three, the laser power of the oscillating laser beam is 3.7KW to 4.3KW, the welding speed is 48mm / s to 55mm / s, and the defocus amount is 0mm.

7. The heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology according to claim 6 is characterized in that: In the step 4, the solution temperature is 450°C to 540°C, and the solution time is 4h to 4.5h.

8. The heat treatment-free die-cast aluminum alloy welding method based on laser oscillation technology according to claim 7 is characterized in that: In the step 4, the aging treatment temperature is 180° C. to 220° C., and the aging time is 2.5 h to 3 h.

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