钢管扩孔开裂缺陷分析

Analysis of Cracking in Steel Tube Reaming

本文通过化学成分分析、硬度、金相检验等方法,对20钢扩孔开裂缺陷进行检验分析,研究了开裂的原因与机理。结果表明:引起钢管裂纹的主要原因是毛管内壁存在细小裂纹。细小裂纹的产生由于加热温度远高于奥氏体化工艺780℃,毛管冷却速度快,导致应力得不到完全释放,增加了开裂的倾向性。在冷精轧时,产生了大量的塑性变形,晶格畸变严重,在内壁应力集中处沿晶界产生裂纹,裂纹在受到外部应力作用下产生开裂。

In this paper, the chemical composition, hardness, metallographic examination and other methods were used to test and analyze the cracking during reaming of 20~# steel, and the causes and mechanisms of cracking were studied. The results show that the main cause of cracking in the steel pipes was the presence of fine cracks in the inner wall of the hollow tube. The occurrence of fine cracks was due to the fact that the heating temperature was much higher than the austenitizing temperature of 780℃, the cooling rate of the hollow tube was fast, which results in no complete release of stress, increases the tendency of cracking. In the cold finish rolling, a large amount of plastic deformation is produced, and the lattice distortion is severe, so fine cracks are generated at the inner wall along the grain boundary where the stress concentrate, and finally cracked under the action of external stress.