Welding of aluminium and aluminium alloys prepared before welding
Release time:
2022-11-03
【Summary Description】 1. Aluminum groove processing should adopt mechanical methods (including shearing), and the groove surface should be silvery white metallic luster; if necessary, 100%PT should be carried out within the scope of not less than 50 mm on the groove and both sides. 2. The welding wire, groove surface and the range of not less than 50 mm on both sides must be cleaned (including removal of oxide film, oxide skin, pollution and unqualified oxide color). Cleaning should also be careful not to press the oxide film into the substrate, so do not use too much force when cleaning; but it is not allowed to use grinding wheel or ordinary sandpaper, because the aluminum material is very soft, resulting in residual sand particles in the aluminum material, which is easy to produce defects such as pores and slag inclusion after welding. 3. The surface of the welding wire can be scrubbed with a stainless steel wire brush or clean oil paper; the welding wire with thicker oxide skin needs to be chemically cleaned before and after welding. Chemical cleaning: soak in 5% ~ 10% NaOH solution at 70 ℃ for about 0.5~3min, then rinse with clean water, soak in 15% HNO3 solution at room temperature for about 1~2min, then rinse with warm water, blow dry with hand-held hair dryer (air compressor is not allowed, because there is water and oil in the air), and then dry in oven at 100 ℃. 4. The cleaned welding wire and weldment should be kept clean and dry, and the welding part should not be touched or blown by hand. Welders generally wear white welding gloves, do not wear dirty gloves, afraid of trouble. Pollution is prohibited before welding, otherwise it should be cleaned again, and local pollution can be partially cleaned; it is best to cover both sides of the groove with white paper. Welding should generally be carried out immediately after mechanical cleaning. If welding is not carried out within 4h after cleaning, it should be cleaned again before welding. 5. Welding parts assembly should be accurate. If the assembly is poor, the parts should be replaced, and the assembly should not be forced to avoid excessive stress. Before formal welding, the groove size should be checked, and welding can be carried out only after it is qualified. 6. When assembling weldments, try to avoid spot welding in places where stress is concentrated (such as weld intersections and corners on the workpiece, etc.).). The length and spacing of tack welds are as follows:(mm) Painting 7. Aluminum is easy to deform and collapse during welding, so it is necessary to make fixtures and shim iron before welding. When using a fixture, the front and back of the parts generally need to be clamped, and the rigidity and clamping force of the fixture should be moderate, because it is too small to control the deformation; if it is too large, the degree of restraint of the weld is too strong, which will easily lead to weld cracking. The clamping force shall be 350Kg/100mm. The soft aluminum fixture can be carbon steel or stainless steel, which can slow down heat dissipation; reinforced aluminum can be used as a fixture to enhance heat dissipation. The longitudinal seam clamp may be a keyboard type and the annular seam clamp may be a hydraulic bulge clamp. When assembling the longitudinal seam, the gap can be appropriately increased to allow shrinkage space after welding; circumferential seam (including circular flange, flange, etc.) There are some reverse wrong edges or cross edges, because the flange will collapse and deform after welding. The backing plate is generally made of stainless steel or carbon steel, and graphite can be used for aluminum welding with low requirements. The choice of liner material should also consider the effect on the cooling rate of the weld. When the aluminum plate is thicker or the assembly gap of the backing plate is larger, the gap can be sealed with clay mud and removed after welding.
1. Aluminum groove processing should adopt mechanical methods (including shearing), and the groove surface should be silvery white metallic luster; if necessary, 100%PT should be carried out within the scope of not less than 50 mm on the groove and both sides.
2. The welding wire, groove surface and the range of not less than 50 mm on both sides must be cleaned (including removal of oxide film, oxide skin, pollution and unqualified oxide color).
Cleaning should also be careful not to press the oxide film into the substrate, so do not use too much force when cleaning; but it is not allowed to use grinding wheel or ordinary sandpaper, because the aluminum material is very soft, resulting in residual sand particles in the aluminum material, which is easy to produce defects such as pores and slag inclusion after welding.
3. The surface of the welding wire can be scrubbed with a stainless steel wire brush or clean oil paper; the welding wire with thicker oxide skin needs to be chemically cleaned before and after welding.
Chemical cleaning: soak in 5% ~ 10% NaOH solution at 70 ℃ for about 0.5~3min, then rinse with clean water, soak in 15% HNO3 solution at room temperature for about 1~2min, then rinse with warm water, blow dry with hand-held hair dryer (air compressor is not allowed, because there is water and oil in the air), and then dry in oven at 100 ℃.
4. The cleaned welding wire and weldment should be kept clean and dry, and the welding part should not be touched or blown by hand. Welders generally wear white welding gloves, do not wear dirty gloves, afraid of trouble.
Pollution is prohibited before welding, otherwise it should be cleaned again, and local pollution can be partially cleaned; it is best to cover both sides of the groove with white paper. Welding should generally be carried out immediately after mechanical cleaning. If welding is not carried out within 4h after cleaning, it should be cleaned again before welding.
5. Welding parts assembly should be accurate. If the assembly is poor, the parts should be replaced, and the assembly should not be forced to avoid excessive stress. Before formal welding, the groove size should be checked, and welding can be carried out only after it is qualified.
6. When assembling weldments, try to avoid spot welding in places where stress is concentrated (such as weld intersections and corners on the workpiece, etc.).). The length and spacing of tack welds are as follows:(mm)
Painting
7. Aluminum is easy to deform and collapse during welding, so it is necessary to make fixtures and shim iron before welding.
When using a fixture, the front and back of the parts generally need to be clamped, and the rigidity and clamping force of the fixture should be moderate, because it is too small to control the deformation; if it is too large, the degree of restraint of the weld is too strong, which will easily lead to weld cracking. The clamping force shall be 350Kg/100mm.
The soft aluminum fixture can be carbon steel or stainless steel, which can slow down heat dissipation; reinforced aluminum can be used as a fixture to enhance heat dissipation.
The longitudinal seam clamp may be a keyboard type and the annular seam clamp may be a hydraulic bulge clamp. When assembling the longitudinal seam, the gap can be appropriately increased to allow shrinkage space after welding; circumferential seam (including circular flange, flange, etc.) There are some reverse wrong edges or cross edges, because the flange will collapse and deform after welding.
The backing plate is generally made of stainless steel or carbon steel, and graphite can be used for aluminum welding with low requirements. The choice of liner material should also consider the effect on the cooling rate of the weld. When the aluminum plate is thicker or the assembly gap of the backing plate is larger, the gap can be sealed with clay mud and removed after welding.
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