Effect of SCM435 initial microstructure and annealing process on spheroidization grade and properties

Abstract

In order to research the evolution of microstructures and properties of SCM435 wire rod after annealing with different initial structures, two kinds of initial microstructure (B+M and F+P) SCM435 wire rods were used to simulate spheroidizing annealing, softening annealing and stress relief annealing processes respectively. The results show that under the same process conditions, the spheroidization grade of B+M was 1-2 higher than that of F+P, while the hardness does not decrease with the increase of spheroidization grade. The analysis indicated that precipitation strengthening occurs not only in the micro alloy composition system, but also in carbon steel. By control the size and amount of cementite precipitation particles, obvious strengthening effect can also be produced. Besides, after high-temperature annealing, low spheroidization grade sample has more massive ferrite and concentrated cementite, causing the hardness decreasing. In addition, the differences between the simulation process and the industrial production process are analyzed to provide guidance for formulating annealing process of different enterprises and equipment.