关键词: SA-106B, 钢管, 热弯, 铜脆, 晶界开裂, 富Cu相

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