Abstract: After induction heating， the SA-106B seamless steel pipe has cracks during hot bending process， the physical and chemical properties of the SA-106B seamless steel pipe and the hardness uniformity of the full cross-section were analyzed， and the cracking samples were tested by optical microscope. Combined with energy spectrum analysis， the hot bending cracking was confirmed to be caused by the contact between the surface of the steel pipe and the Cu parts during the production process. Caused by Cu adhesion to the surface of the steel pipe， the formation of a molten Cu-rich phase during induction heating， the rich Cu-rich phase erosion of the steel pipe surface of the grain boundary， and along the grain boundary to spread inward， resulting in "copper brittle" cracking under tensile stress After a comprehensive investigation， the improvement measures are proposed to replace the material of the outlet guide barrel of the straightener from “brass” to nylon sheet， which can effectively avoid "copper brittle" cracking. The analysis shows that copper fittings and similar low melting point metal fittings cannot be used in the production process of steel pipes that need to be hot bent， so as to avoid cracking caused by "copper brittleness" and cracking caused by pollution of low melting point metal materials. At the same time， during the transfer， loading， unloading and storage process， care should also be taken to avoid contact with copper fittings and similar low-melting metals.

Key words: SA-106B, Steel Pipe, Hot Bending, Copper Brittle, Grain Boundary Cracking, Cu-rich Phase

摘要： SA-106B无缝钢管经过感应加热后，热弯制时出现裂纹，对SA-106B无缝钢管的理化性能和全截面的硬度均匀性进行分析，并采用光学显微镜对开裂样品进行检验，配合能谱分析，确认热弯开裂原因为钢管在生产过程中，钢管表面与Cu质配件接触，造成Cu黏附在钢管表面，感应加热时，形成了熔融的富Cu相，富Cu相侵蚀钢管表面的晶界，并沿晶界向内扩散，在受到拉应力作用时，造成了“铜脆”开裂。经全面排查，提出了将矫直机出口导筒材质由“黄铜”更换为尼龙板的改进措施，可以有效避免“铜脆”开裂。通过分析表明，对于需要进行热弯加工的钢管，生产过程中不能使用铜质配件及类似的低熔点金属材料配件，避免出现“铜脆”开裂及低熔点金属材料污染导致的开裂；同时，在转移及装卸和存储过程中，也应注意避免接触铜质配件及类似的低熔点金属。

关键词: SA-106B, 钢管, 热弯, 铜脆, 晶界开裂, 富Cu相