What are the causes of skin injury caused by steel pipe perforation?

There are large areas of inclusions in the defects, and the formation of skin warping defects is caused by the continuous thinning of the pipe wall, the gradual exposure of inclusions and the outward appearance of skin during the deep processing of pipe piercing. The mineral phases of inclusions in the warping zone are mainly calcium aluminate and topaz, and there are also a few zirconia corundum metamorphic bodies and magnesia-alumina spinel, which are consistent with the erosion reaction products of the lower nozzle. The accumulated large inclusions are related to the mud flow after the erosion of the lower outlet.