1. The hot-rolling positions of ASTM A53 thick-walled seamless steel tube are from 38,118 m steel head, mainly located in the middle of the steel strip.
2. It is presumed that the gap begins in the middle of the strip width, because the rolling force and shear force during rolling cause the gap to be stretched to form macro-holes.
3. Seamless steel tube breaks off in cold rolling process, and its fracture surface is smooth. There are no obvious surface defects before and after fracture.
Microstructure of fracture was observed and typical ductile fracture morphology was observed. At the same time, the fracture is layered, the central depression is large, the depression narrows near the surface, the central fracture appears, the central fracture depth is deep, it is presumed that the stratified topography is closely related to the central isolation.


Analysis of ASTM A53 Thick Wall Seamless Steel Pipe:
1. The surface morphology of hot-rolled and cold-rolled steel tubes was observed under scanning electron microscopy, and cracks were observed in the middle of fracture.
The results show that there are obvious oxidized particles near the crack and complete polygonal ferrite morphology near the crack.
3. The characteristics of 30um oxide particles near the crack are closely related to the original defects of continuous casting slab. The continuous casting slab is heated for a long time in the heating furnace, which oxidizes the elements near the cracks and forms a thicker oxide layer. Inherit to the last volume.
The results show that there are obvious cracks and oxidation zones in the thickness center, which is 1/4. There are also oxidized particles near the cracks.