The general sequence of welding is: pre welding inspection → preheating and rust removal → installing welding pads and arc plates → welding → inspection
1. Before welding, check the angle, blunt edges, gaps, and misalignment of the groove. Rust spots, oil stains, and iron oxide scales inside and on both sides of the groove should be removed thoroughly.
2. Preheat. Before welding, use gas welding or a special baking gun to evenly heat the base material within 100mm of the groove and both sides, and measure the temperature with a surface thermometer to prevent temperature deviation or local oxidation on the surface. Preheat the temperature.
3. Recheck the preheating temperature, and if the temperature is not enough, reheat it to meet the requirements.
4. Install welding pads and arc plates, with the same surface cleanliness as the groove surface. The pads should be tightly attached to the base material, and the arc plates should be firmly welded to the base material.
5. Welding: The first layer of weld should seal the connection between the base metal and the backing plate inside the groove, and then weld layer by layer until the groove is filled. After each weld is completed, welding slag and spatter must be removed. If welding defects occur, they should be promptly ground and repaired.
6. An interface must be continuously welded. If it is necessary to stop welding midway, insulation and slow cooling treatment should be carried out. Before re welding, it should be reheated according to regulations.
When encountering rain or snow, welding should be stopped. There should be wind and rain shelters around and above the welding joints of the components. Welding should be stopped when the wind speed is greater than 5m/s. When the ambient temperature is below zero degrees, preheating and post heating measures should be taken according to regulations for construction.
8. Carbon structural steel should undergo weld seam inspection after cooling to ambient temperature, and low alloy structural steel should undergo weld seam inspection after 24 hours of completion.
Welders and inspectors should carefully fill out the work record form.
