1. Environmental requirements
1. The welding repair site should be in still air above 5℃.
2. When the ambient and workpiece temperatures are lower than 5°C, welding is not allowed, but partial preheating is allowed before welding.
2. Selection of welding machines and welding rods and adjustment of welding current
1. Both DC arc welding machines and AC arc welding machines can be used.
2. When welding and repairing the chassis or car body steel structure made of weathering steel, weathering steel and corresponding weathering steel electrodes (such as J502, etc.) must be used. When welding ordinary steel and weathering steel, ordinary carbon steel electrodes (such as J442, J506, J507, etc.).
3. Use DC reverse connection when welding with alkaline electrodes (J507 can only be used with DC arc welding machines).
4. For welding current adjustment, refer to Table 8-1.
3. Preparation before welding
1. When using alkaline welding rods (such as J506, J507), they need to be dried at 350~400℃ for 1~2h. The dried welding rod should be placed in the insulation cylinder and taken out as needed. Pay attention to keep it dry during use. Welding rods that are not used up on the same day must be re-dried before use the next day, and the number of repeated drying times shall not exceed 3 times.
2. When using acidic welding rods (such as J502, J442), they need to be dried at a temperature of 150 to 200°C. The dried welding rod should be placed in the insulation cylinder and taken out as needed. Pay attention to keep it dry during use. Welding rods that are not used up on the same day must be re-dried before use the next day, and the number of repeated drying times shall not exceed 3 times.
3. Before welding operation, the weldment should be preheated before welding. The method of local uniform preheating can be used to preheat the welded area to about 150℃.
4. Before welding, impurities such as rust, oil, and sewage must be removed from the welded parts.
4. Precautions during welding
1. When striking the arc, be careful to prevent the arc from damaging the surface of the accessory. Do not strike the arc on non-welded repair surfaces.
2. Before welding, impurities such as rust, oil and water must be removed from the welded parts. Short arc operation must be used during welding, and a narrow weld bead is suitable.
5. Post-weld quality inspection
1. The surface of the weld should be smooth, and the connection between each part of the weld and the base metal should be smooth.
2. The weld should not have defects such as cracks, slag inclusions, incomplete penetration, incomplete fusion and arc craters, and the undercut depth should not be greater than 0.5mm.
6. Post-weld heat treatment
After welding, cover the welding area with asbestos cloth and slowly cool to room temperature.
