Coarse-grain Heat Affected Zone Microstructure and Toughness of Copper-Bearing Age-Hardening Steels

摘要

Microstructure and toughness of copper-bearing age hardening steel was studied and SHCCT curve was also measured. The result shows that cooling rate had a great effect on microstructures and toughness of coarse-grain zone. Microstructures of coarse-grain zone varied from thick granular-bainite to thin lath bainite with the increase of cooling rate. It obtained good low-temperature toughness with the MDT temperature (Nil-ductility transition temperature) below -50°C when the cooling time from 800°C to 500°C is lower than 40s. On the contrary, the toughness of coarse-grain zone was greatly decreased because of the increase in the amount of M-A island which was considered to be the important reason leading to deteriorate of coarse-grain toughness.