1Cr18Ni10Ti不锈钢管扩口开裂失效分析

Failure analysis on flaring crackings of 1Cr18Ni10Ti stainless steel tube

1Cr18Ni10Ti不锈钢导管在扩口时,喇叭口外表面出现了裂纹。采用光学显微镜、显微硬度计对钢管的表面形貌、显微组织、显微硬度进行了检测分析。结果表明:导管原材料在经氨分解气氛保护热处理中残留氨控制不当,在高温下分解出N原子,导致管材表面产生硬脆的渗氮层,塑性降低,造成扩口时开裂。

Cracks were found on outer surface of 1 Cr18 Ni10 Ti stainless steel after flaring process.Surface topography,microstructure,and microhardness were investigated by using microscope and microhardness tester.The results show that due to the ammonia decomposition protection atmosphere is not appropriately controlled in heat treatment of the raw materials for tube-making,the Nitrogen atoms decomposed from the residual ammonia in the high temperature result in a hard and brittle nitriding layer on the surface of the raw materials,which reduces the plasticity of the raw material,and induce crackings at the outer surface of tube after flaring.