Folding Seamless Steel Pipe

Seamless steel pipe external folding is divided into two types: steel external folding and operation external folding.

(1) Steel outer folding

There are two main types of steel outer folds: the first is irregular sheet-like folds on the outer surface of the steel pipe, and the outer edges of the folds are zigzag. The cause of such defects is mainly due to the subcutaneous bubbles (pores) or pores over the billet. The cold skin produced in the casting process of the billet is not cleaned up; the second is that the outer surface of the steel pipe is folded in a regular large spiral. The main reason for such defects is generally due to the surface of the billet during the continuous casting process. The edge of the stop roller is scratched to form a straight line or form lugs, or there are cracks on the surface of the continuous casting billet. The straight line is not cleaned or the edge of the straight line is not smooth transition when the blank is arranged, causing the outer surface to fold during perforation.

(2) Operation outside folding

There are mainly two types of external folds: linear short-line and spiral external folds. The linear short-line outward fold is mainly formed by the deep and steep grooves of the piercing section of the piercer roll; the spiral outward fold is mainly caused by the use of damaged rolls during rolling or improper adjustment of the mill pass.