Gas welding cast aluminum is a useful skill in some industries, how to gas weld aluminum correctly?
Gas welding of cast aluminum alloy, generally speaking, the welding technology of cast aluminum and deformed aluminum is basically similar, and the strength of gas welding joint is generally about 70% of the base metal. The color of aluminum silicon alloy is bluish and dull, the fracture structure is fine and dense, the fluidity is good after melting, there are black spots on the aluminum liquid, the shrinkage rate after welding is small, and there is no male cracking. The color of aluminum magnesium alloy is white, and the fracture structure is coarse. When it is heated and melted, white flowers fly out and white smoke appears, which is due to the burning loss of magnesium.
1. Preparation before welding
The defects shall be completely eliminated. The thick wall machinist shall drill a 60 º V-shaped Pojiang at both ends of the crack. The back of the crack shall be padded with asbestos cloth. The welding wire shall be homogeneous or universal (HS311), the flux CJ401, and the medium size welding gun shall be used. Prepare or make necessary clamps according to the needs of weldments to improve welding quality.
2. Gas welding process
Preheat 250-300 ℃, start to use a neutral flame, and use a slightly magnetized flame after melting. The welding nozzle angle is 25-30 º. When the weldment is melted at the heating point, raise the welding torch and send the welding wire with deep flux. When the end of the welding wire is melted, the droplet drops into the molten pool immediately. When impurities such as oxide film are found on the surface of the molten pool during welding, they shall be removed with welding wire at any time.
3. Post welding treatment
Slow cooling measures shall be taken after welding, or annealing treatment at 300 ℃-350 ℃ can be carried out to reduce welding stress. After all welding partners have cooled down, use hot water and wire brush to clean the welding slag and flux near the weld. If post weld heat treatment is required for special strengthening requirements, the specific removal sequence is as follows:
1) When the weldment is not completely cooled, immerse it in a 40 ℃-50 ℃ hot water bath, and brush the weld repeatedly with a brush.
2) Immerse the weldment in nitric acid solution. When the room temperature is above 25 ℃, the solution concentration is 15%-20%, and the immersion time is 10-15 minutes; When the room temperature is 10 ℃-15 ℃, the solution concentration is 20%-25%, and the immersion time is 15 minutes.
3) Place the weldment in the tank with flowing hot water (40 ℃-50 ℃): clean for 5-10 minutes. Rinse the weldment with cold water for 5 minutes.
4) Dry the weldment by drying or air blowing.