对20gu钢锭、方坯、圆管坯和钢管进行了表面检查,发现无缝钢管管坯的主要缺陷有裂纹、结疤、夹杂、划伤、折叠等。用对比试验、同位素Co~(60)标定,研究了不同模型、不同类型保护渣、不同规格方坯的缺陷演变过程,得出结论如下:①方坯裂纹深度≤2mm者,轧成圆管坯时可以消除,>2mm的不能消除;②圆管坯裂纹深度≤1mm者,轧成钢管时可以消除,>1mm的不能消除;③结疤缺陷是由保护渣卷入产生的,在轧成钢管时,结疤形成外折。 Surface examination of 20gu steel ingot, billet, round tube billets and steel pipes found that the main defects of seamless steel tube billets were cracks, scarring, inclusions, scratches and collapsing. The contrastive tests and isotopes Co ~ (60) calibration were used to study the evolution of defects in different molds, different types of mold fluxes and billets with different specifications. The conclusions are as follows: (1) If the depth of billet is less than 2mm, Can be eliminated,> 2mm can not be eliminated; ② round tube billet crack depth of less than 1mm, can be eliminated when rolling into the tube,> 1mm can not be eliminated; ③ scar defect is caused by the involvement of mold flux, Scar formation of the outer fold.