Microstructure and properties of warm worked medium carbon steels

Abstract

In response to the growing interest of the automotive industry in warm precision forging, a laboratory study has been conducted to examine the response of selected medium carbon steels to warm working in the range 650–1060°C. The microstructure and tensile and impact properties have been determined after single, double, and multipass rolling operations. The initial work on 080M40 steel was conducted in collaboration with Austin Rover for the production of stub axle forgings. Properties satisfying the BS970 ‘R’ condition were achieved after soaking at 820–900°C and finish working at 730°C, followed by air cooling. The induction hardening response of the warm worked steels was also satisfactory. The addition of vanadium can be used either to increase strength (by adopting a soaking temperature of 1150°C) or to give an improved strength–toughness combination (by using a soaking temperature of 900°C). The properties of warm worked steels are shown to be dependent upon chemical composition, soaking and working temperature, and subsequent cooling rate. The results have been explained in terms of classical structure–property relationships.MST/727