Welding method: When welding
thick-walled steel pipes, first clean the oil, paint, water, rust, etc. of the welding joints, and then open the grooves according to the wall thickness. It is the gap of the product, which is generally 1-1.5 times the diameter of the electrode or wire. If the groove is accidentally opened, it can be left smaller. Spot welding at least three points, generally four points are better to work. When welding, it should be welded in half and half, and the starting point is about one centimeter above the bottom point so that the joint is good from the opposite side. If the wall of the steel pipe is thick, it should be layered, in at least two layers and the second layer can be welded after the whole circle is welded.
Process flow: round tube billet → heating → perforation → three-roll skew rolling, continuous rolling or extrusion → pipe removal → sizing (or diameter reduction) → cooling → straightening → hydraulic test (or flaw detection) → marking
Weld height: when the steel pipe wall thickness is not more than 12.5mm, the weld excess height is not more than 3.0mm; when the steel pipe wall thickness is more than 12.5mm, the weld excess height is not more than 3.5mm.
Bending degree: The steel pipe with a nominal outer diameter of not more than 168.3mm shall be straight or according to the bending degree index stipulated in the agreement between the supplier and the buyer; for the steel pipe with a nominal outer diameter of more than 168.3mm, the bending degree shall not be greater than 0.2% of the full length of the steel pipe. For steel pipes with a wall thickness of more than 4mm at the pipe end, the pipe end can be processed with a groove of 30°+5°0°, with a root of 1.6mm±0.8mm, and the pipe end slope is less than or equal to 5mm.
