Welding process of thick-walled steel pipes

First, the welding method of thick-walled steel pipes
When welding thick-walled steel pipes, first clean the oil, paint, water, rust, etc. on the weld, then make a groove according to the wall thickness, thicker, larger, thinner (angle grinder), and then the gap between the products, generally 1-1.5 times the diameter of the welding rod or wire. If the groove is accidentally opened larger, it can be appropriately left smaller. Spot welding should be done at least three times, and four points are generally easier to work. When welding, it should be welded half and half, and the starting point should exceed the bottom point by about one centimeter so that it is easier to connect 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 be welded after the whole circle is welded.

Second, the process flow of thick-walled steel pipes
Round tube billet → heating → perforation → three-roller oblique rolling, continuous rolling or extrusion → tube removal → sizing (or reducing diameter) → cooling → straightening → hydraulic pressure test (or flaw detection) → marking

Third, the weld height of thick-walled steel pipes
When the wall thickness of the steel pipe is not more than 12.5mm, the weld height is not more than 3.0mm; when the wall thickness of the steel pipe is greater than 12.5mm, the weld height is not more than 3.5mm.

Fourth, the curvature of thick-walled steel pipes
Steel pipes with a nominal outer diameter of not more than 168.3mm should be straight or by the curvature index agreed upon by the supply and demand parties; for steel pipes with a nominal outer diameter greater than 168.3mm, the curvature shall not exceed 0.2% of the total length of the steel pipe. For steel pipes with wall thickness greater than 4mm, the steel pipe ends can be processed with a groove of 30°+5°0°, leaving a root of 1.6mm±0.8mm, and the slope of the steel pipe ends is less than or equal to 5mm.