First, the principle of the steel pipe welding process
(1) During the welding process, if the interlayer temperature is too high, the grain will be elongated and t8/5 will increase. Normalizing treatment will not be possible during on-site welding, and the original strength and toughness of the steel will be lost. Therefore, the interlayer temperature must be strictly controlled during the welding process to prevent grain elongation.
(2) The constant temperature time, heating width, insulation thickness, and insulation width of heat treatment are the main factors affecting the toughness of the weld.
Appropriately extending the constant temperature time, increasing the heating width insulation width, and insulation thickness will help increase the tempering degree of the martensitic structure and improve the toughness of the weld.


Second, steel pipe welding process
(1) The base weld adopts double-layer argon arc welding with a 3.2mm electrode, and the other layers adopt a multi-layer multi-pass welding process with a single-layer thickness of less than or equal to 3mm. During the welding process, it is necessary to master the relationship between welding current and welding speed. By increasing and reducing the weld thickness and welding speed, a large swing rapid thin layer welding operation technology is adopted.
(2) During welding, technicians use a far-infrared temperature gun to measure the interlayer temperature of each weld, and the interlayer temperature is strictly controlled below 300 degrees (the interlayer temperature is 10~20mm before the molten pool, expressed as the highest value).


When the far-infrared temperature gun shows that the temperature exceeds 300 degrees, stop welding immediately and continue welding when the temperature drops to 230 degrees. After each layer of welding is completed, technicians use a vernier caliper to measure the weld thickness. It is strictly forbidden to form a fillet weld between the weld and the groove. The maximum thickness is less than or equal to 3mm.