Effects of vanadium on upper-nose temper embrittlement and other Mechanical properties of Cr–Ni–Mo low-alloy steels

Abstract

Large components manufactured from Cr–Mo–Ni low-alloy steels are usually heavily tempered for the purpose of stress relieving, with resultant undesirable loss of strength and the inception of upper-nose temper embrittlement (UNTE). This paper describes an investigation on the effects of vanadium additions and of variation in the molybdenum content on the properties of these heavily tempered steels. It is shown that the addition of vanadium to these steels leads to a substantial improvement in their strength without impairment of their ductility and toughness, and also to a marked improvement in their resistance to UNTE. An increase in the molybdenum content of the steel from 0·5 to 1·0% leads to a moderate improvement in its strength, but has an aggravating effect on its susceptibility to UNTE, as a result of an increase in the coarsening rate of the grain boundary carbides and the formation of unfavourable M23C6 and MaCb molybdenum-rich large carbides.MST/390