Large-gap MIG welding method for aluminum alloy

Abstract

The invention discloses an aluminum alloy large-gap MIG welding method which comprises the following steps: firstly, determining the thickness position and the welding direction of a fillet weld of a to-be-welded workpiece, determining welding current according to the thickness of the to-be-welded workpiece, and continuously heating a molten pool by adopting a delay staying method in an arcing stage; s2, in the welding stage, switches of the robot and the MIG welding machine are turned on, and a MIG welding gun walking path program carried by the welding robot is compiled; an MIG welding gun carried by the robot swings in a Z shape and swings back and forth, a double-pulse scheme is adopted in the welding process specification, according to the welding current scheme, the welding current is determined according to the thickness of the aluminum alloy, the welding parameter of welding swing in the forward direction is small current, and the welding parameter of welding swing in the backward direction is large current; and after swinging of the welding gun is finished, the welding gun continuously moves for a certain distance, and the welding gun moves to a welding end point. Effective welding can be achieved under the working conditions of different thicknesses and large gaps, and the welding quality is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a large-gap MIG welding method for aluminum alloys, which is suitable for aluminum alloy parts on new energy vehicles. Background Art

[0002] Due to the relatively small density of aluminum alloy, the mass of aluminum alloy of the same volume is only about 1 / 3 of carbon steel, and it has the advantages of good corrosion resistance, high recycling value, good conductivity and energy absorption performance. Under the trend of lightweighting of new energy vehicles, aluminum alloy profiles and aluminum alloy castings are widely used. At the same time, in order to achieve weight reduction requirements, profiles are designed into structures of various thicknesses. MIG welding is an efficient and high-quality welding method, which is often used in various structural welding of aluminum profiles. In the welding of aluminum alloy profiles, welding joints with different thickness combinations of materials are often encountered. Different thicknesses lead to unbalanced welding heat distribution during welding. Due to the large thermal expansion coefficient of aluminum alloy, the product sizes produced at different temperatures are different, and there are different gaps in the welding joints. The gap adaptability of ordinary MIG welding is 0.7mm. Under actual working conditions, it is very normal for the gap of welding joints composed of profiles with a length of more than 1500mm to fluctuate within 2mm. Therefore, various defects such as weld breakage, weld deviation, back penetration and lack of root penetration often occur, which seriously affect the welding quality and product qualification.

[0003] The aluminum alloy MIG welding methods in the prior art mostly use the position offset method to distribute the welding heat for welding profiles of different thicknesses. Since MIG welding is pulse welding, the welding molten pool is often unstable. As the temperature rises, it shifts to the thick plate, resulting in insufficient penetration of the thick plate, partial weld breakage and back penetration of the thin plate. For large-gap welded joints, the existing MIG welding method is prone to weld breakage and weld holes using a one-time welding method, which requires subsequent repair using the TIG welding process; the two-time welding method is prone to defects such as insufficient root penetration. Therefore, the MIG welding process requires the gap of the joint to be controlled to be less than 0.7mm. This gap requirement can greatly improve the accuracy of the product, but it leads to a decrease in the product qualification rate and an increase in production costs. The market also has different thicknesses using different welding specifications to solve the problem of different thickness combination joints, but it cannot solve the MIG welding defects of large-gap thick plates and the low qualification rate. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a large gap MIG welding method for aluminum alloy, which can achieve effective welding under conditions of different thicknesses and large gaps, improve welding quality, and increase the strength of welded joints; utilize the robot swinging action to adjust the welding specifications so that materials of different thicknesses obtain welding heat produced by different specifications, expand the robot swing range, and use high-speed weld cooling to increase the thickness of the weld and reduce the size of the molten pool, thereby reducing defects such as weld breakage.

[0005] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme: A large gap MIG welding method for aluminum alloy comprises the following steps: S1. Arc starting stage: determine the thickness position and welding direction of the fillet weld of the workpiece to be welded, and determine the welding current according to the thickness of the workpiece to be welded. The relationship between the welding current I and the plate thickness t of the workpiece to be welded is determined by the following formula: I=~2.43t²+64.8t+1; The arc starting current is set to 130% of the welding current of the maximum plate thickness; the delay dwell method is used to continuously heat the molten pool during the arc starting stage, and the delay time is controlled to be 0.1~0.3s; S2, welding stage: turn on the robot and MIG welding machine switches, and compile the MIG welding gun walking path program carried by the welding robot; the MIG welding gun carried by the robot swings in a Z-shaped manner, the swing frequency is 1.2-1.8Hz, the swing mode is forward and backward swing, the rear swing point is 1.5-2mm away from the thick plate, the front swing amplitude is controlled at 8-12mm, and the rear swing amplitude is controlled at 3-5mm; the welding process specification adopts a double pulse scheme: the welding current scheme determines the welding current according to the thickness of the aluminum alloy, the welding parameters of the welding swing in the forward direction are small current a, and the swing in the backward direction is large current b, and the size of the small current a and the large current b are set according to the plate thickness according to the formula in step S1; the small current a is controlled at 100A-180A, the large current is 130%-150% of the small current, and the welding speed is controlled at 0.3-0.6m / min; S3, arc closure stage: After the welding gun finishes swinging, it continues to move for a distance of 2 to 4 mm, and then moves to the end point of welding; the welding current for arc closure at the end point is 50 to 80A, the voltage is 13 to 17V, and the arc closure time is 0.5 to 0.8s.

[0006] Due to the adoption of the above-mentioned technical solution, the present invention has the following advantages: The invention discloses a large gap MIG welding method for aluminum alloy, wherein the welding process adopts a swinging process, the MIG welding arc always contacts the root of the joint, and the welding root penetration of the joint is guaranteed; the arc swings at a high speed during welding, which increases the heat dissipation area, improves the solidification speed of the molten pool, and controls the penetration size at the same time, so that materials of small thickness can be welded, and the profile is not easy to be welded broken; since a large current swinging and stopping method is adopted during welding, the size of the weld bead is increased, and the welding strength and the weld bead bearing strength are guaranteed; the swinging is at a certain angle, which plays a bridging role on the welding gap, and effectively prevents the problem of weld breaking caused by the large gap; the swinging action is added during the welding process, so that the welding metallographic characteristics present a standard bowl-shaped penetration depth, which is significantly improved compared with the finger-shaped penetration depth in the prior art, and the welding qualified rate is increased from 75% to 99.7%; the welded weld has a smooth surface, small spatter, and no defects such as weld breaking; for joints with a gap within 1.5 mm, the welding qualified rate reaches 100%, and for joints with a gap within 2.0 mm, the welding qualified rate reaches 99%, which has good promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a schematic diagram of the swing mode in the aluminum alloy large gap MIG welding method of the present invention; Figure 2 It is a schematic diagram of welding heat distribution in the aluminum alloy large gap MIG welding method of the present invention; Figure 3 It is a schematic diagram of the robot swing path in the aluminum alloy large gap MIG welding method of the present invention; DETAILED DESCRIPTION

[0008] The technical solution of the present invention is further described in detail below through the drawings and embodiments.

[0009] like Figure 1 As shown, a large gap MIG welding method for aluminum alloy comprises the following steps: S1. Arc starting stage: Determine the thickness position and welding direction of the fillet weld of the workpiece to be welded, and determine the welding current according to the thickness of the workpiece to be welded. The relationship between the welding current I and the plate thickness t of the workpiece to be welded is determined by the following formula: I=~2.43t²+64.8t+1, such as Figure 2 As shown; The arc starting current is set to 130% of the welding current of the maximum plate thickness; the delay dwell method is used to continuously heat the molten pool during the arc starting stage, and the delay time is controlled to be 0.1~0.3s to increase the weld heat and weld size and reduce spatter; S2, welding stage: turn on the robot and MIG welding machine, and program the MIG welding gun walking path carried by the welding robot; Figure 3As shown, the MIG welding gun carried by the robot swings in a Z-shape with a swing frequency of 1.2 to 1.8 Hz, which is determined according to the gap between the products. The larger the gap, the faster the swing frequency. Preferably, the swing frequency is set to 1.8 Hz; the swing mode is forward and backward swing, and the rear swing point is 1.5 to 2 mm away from the thick plate. The front swing amplitude is controlled at 8 to 12 mm, and the rear swing amplitude is controlled at 3 to 5 mm. The function is to weld forward at high speed with small current specifications, reduce the size of the molten pool, and increase the bridging ability under large gaps; to weld backward at low speed with large current specifications to increase the size of the weld bead, increase strength and improve surface appearance; during welding, the swing frequency is adjusted according to the swing frequency. Amplitude and position, adjust the welding specifications to adapt to different thickness requirements. The welding process specifications adopt a double pulse scheme: the welding current scheme determines the welding current according to the thickness of the aluminum alloy. The welding parameters of the welding swing in the forward direction are small current a and large current b in the backward direction. The size of small current a and large current b is set according to the formula in step S1 according to the plate thickness; the small current a is controlled at 100A~180A, the large current is 130%~150% of the small current, and the welding speed is controlled at 0.3~0.6m / min; when the welding speed corresponding to the welding material is small and the thickness of the welding profile is small, the swing speed needs to be larger; S3, arc closure stage: After the welding gun finishes swinging, it continues to move for a distance of 2 to 4 mm, and then moves to the end point of welding; the welding current for arc closure at the end point is 50 to 80A, the voltage is 13 to 17V, and the arc closure time is 0.5 to 0.8s.

[0010] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for large gap MIG welding of aluminum alloy, characterized by: It includes the following steps: S1. Arc starting stage: determine the thickness position and welding direction of the fillet weld of the workpiece to be welded, and determine the welding current according to the thickness of the workpiece to be welded. The relationship between the welding current I and the plate thickness t of the workpiece to be welded is determined by the following formula: I=~2.43t²+64.8t+1; The arc starting current is set to 130% of the welding current of the maximum plate thickness; the delay dwell method is used to continuously heat the molten pool during the arc starting stage, and the delay time is controlled to be 0.1~0.3s; S2, welding stage: turn on the robot and MIG welding machine switches, and compile the MIG welding gun walking path program carried by the welding robot; the MIG welding gun carried by the robot swings in a Z-shaped manner, the swing frequency is 1.2-1.8Hz, the swing mode is forward and backward swing, the rear swing point is 1.5-2mm away from the thick plate, the front swing amplitude is controlled at 8-12mm, and the rear swing amplitude is controlled at 3-5mm; the welding process specification adopts a double pulse scheme: the welding current scheme determines the welding current according to the thickness of the aluminum alloy, the welding parameters of the welding swing in the forward direction are small current a, and the swing in the backward direction is large current b, and the size of the small current a and the large current b are set according to the plate thickness according to the formula in step S1; the small current a is controlled at 100A-180A, the large current is 130%-150% of the small current, and the welding speed is controlled at 0.3-0.6m / min; S3, arc closure stage: After the welding gun finishes swinging, it continues to move for a distance of 2 to 4 mm, and then moves to the end point of welding; the welding current for arc closure at the end point is 50 to 80A, the voltage is 13 to 17V, and the arc closure time is 0.5 to 0.8s.

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