Abstract:

Adding strong carbide forming elements in SCM435 cold heading steel reduces the diffusion rate of carbon atoms and results in longer spheroidizing annealing time. By controlling the rolling temperature and post-rolling cooling process, bainite-dominated transformation structure can be obtained, and rapid spheroidization of the matrix structure can be achieved in subsequent spheroidizing annealing process. By comparison, the spheroidizing annealing time can be shortened by about 50%, uniform and fine spheroids can be obtained after spheroidizing, which can meet the cold heading performance requirements of the customers, and achieve the goal of energy saving with emission reduction.

Key words: SCM435 cold heading steel, bainite, spheroidizing annealing, controlled rolling and controlled cooling