Welding method: When welding thick-walled steel pipes, first clean the oil, paint, water, rust, etc. of the weld joints, and then open the bevel according to the wall thickness. It is the gap between the products, which is generally 1-1.5 times the diameter of the welding rod or wire. If the groove is accidentally widened, it can be kept smaller. Spot welding at least three points, generally four points is better to work. When welding, half and half should be welded, and the starting point should be about one centimeter beyond the bottom point so that the joint can be made from the opposite side. If the wall of the steel pipe is thick, it should be layered, with at least two layers, and the second layer can only be welded after the entire circle of the layer is welded.
Process flow: round tube billet→heating→piercing→three-roll cross rolling, continuous rolling or extrusion→pipe removal→sizing (or reducing)→cooling→straightening→hydraulic test (or flaw detection)→marking
Weld reinforcement: When the steel pipe wall thickness is not greater than 12.5mm, the weld reinforcement is not greater than 3.0mm; when the steel pipe wall thickness is greater than 12.5mm, the weld reinforcement is not greater than 3.5mm.
Curvature: steel pipes with a nominal outer diameter of 168.3mm or less shall be straight or as specified in the agreement between the supplier and the purchaser; for steel pipes with a nominal outer diameter of 168.3mm or less, the curvature shall not be greater than 0.2% of the total length of the steel pipe. For steel pipes with a pipe end wall thickness greater than 4mm, the pipe end can be processed with a bevel of 30°+5°0°, a root of 1.6mm±0.8mm, and a slope of the pipe end less than or equal to 5mm.