Solution for Heat Treatment in Quenching Process of S45C Steel Small Diameter Machine Parts Having Strong Texture

Abstract

Small machine parts, made of the JIS S45C rolled steel after common quenching process, have usually crack defects and unsatisfactory hardness of less than 52 HRC. The heat treatment processes give unsatisfactory material structure, such as inhomogeneous and coarse-grained along rolling direction (RD) and traverse direction (TD). This is mostly due to the strong texture microstructure, generated after rolling. This paper represents the heat treatment process, allowing to remove the strong texture to achieve fine grains and high hardness without cracks. This process includes three stages: (i) normalising at 950°C for 15 minutes to remove the texture; (ii) normalising twice at 840°C for 15 minutes and 760°C for 15 minutes, giving grain homogeneousness and the sizes from 10 to 20 m t m; and (iii) quenching at 850°C for 15 minutes and then rapidly cooling in water to obtain hardness from 56 to 58 HRC.