What are the surface defects of carbon steel pipes?

1.folding
it is a kind of straight line or spiral, continuous or discontinuous state that exists on the outer or inner surface of seamless steel pipe. the main reason for folding is poor quality of the pipe material, folding itself, or inclusions, serious scratches and cracks on the surface, edges and corners in the grinding place, and folding after drawing. in order to avoid folding, the quality of the pipe material should be improved and attention should be paid to inspection and grinding.

2.cracks
refers to the small cracks on the inner and outer surfaces of seamless steel pipes that are distributed in straight lines or spirals, with a depth of 1 mm or more, and there are continuous and discontinuous. according to the analysis of shandong jute pipe industry, the reasons are: the hot-rolled billet has subcutaneous bubbles and subcutaneous inclusions, and there are cracks or deep pits on the steel pipe before drawing. during hot rolling or cold drawing operations, longitudinal scratches or scratches were produced. preventing the formation of cracks also lies in improving the quality of the tube blank and strengthening the inspection and grinding of the tube material. at the same time, it is necessary to avoid pitting, scratches and scratches on the pipe during the cold drawing production process.

3.scratches
the characteristic of the defect is that there are longitudinally linear scratches of varying lengths on the inner and outer surfaces of the seamless pipe. most of them are groove-shaped, but they may also be raised stripes. the main reason for the scratches (cutting) is: there are internal markings on the pipe material, which cannot be eliminated during drawing, the iron oxide skin remains on the steel pipe and the mold sticks to the steel, the strength and hardness of the mold are insufficient or uneven, and the mold fragmentation and wear occur, the hammer head is defective, and the sharp edges and corners of the hammer head transition part damage the mold. in order to prevent scratches and scratches, the quality of each preparation process before drawing should be improved, and molds with high strength and hardness and good smoothness should be used.