What is the welding process for thick-walled steel pipes

First, what are the welding methods for thick-walled steel pipes?
When welding thick-walled steel pipes, first clean the weld joint thoroughly to remove oil, paint, water, rust, etc. Then, bevel the weld according to the wall thickness; make the bevel larger for thicker pipes and smaller for thinner pipes (using an angle grinder). Next, determine the gap between the weld joints, generally 1-1.5 times the diameter of the welding rod or wire. If the bevel is accidentally made too large, it can be reduced appropriately. For tack welding, at least three points are required; four points are generally better for easier work. Welding should be done in halves, with the starting point extending about one centimeter beyond the bottom point for easier jointing from the opposite side. If the steel pipe wall is thick, it should be welded in layers, at least two layers, with the first layer completely welded before welding the second layer.

Second, the manufacturing process of thick-walled steel pipes？
Round billet → heating → piercing → three-roll skew rolling, continuous rolling or extrusion → pipe removal → sizing (or reduction) → cooling → straightening → hydrostatic test (or flaw detection) → marking

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

Fourth, details of the curvature of thick-walled steel pipes？
Steel pipes with a nominal outer diameter not greater than 168.3mm shall be straight or meet the curvature index specified in the agreement between the supplier and the buyer; Steel pipes with a nominal outer diameter greater than 168.3mm shall have a curvature not greater than 0.2% of the total length of the steel pipe.

For steel pipes with a wall thickness greater than 4mm at the pipe end, the pipe end can be beveled at 30°+5°0°, leaving a root of 1.6mm±0.8mm, and the pipe end slope is less than or equal to 5mm.