A Study on Structures and Mechanical Properties of Cr-Ni-Mn Stainless Steels

Abstract

The effects of Mn additions on structures of Cr-Ni stainless steels are not well known yet. It has been reported that in a certain case Mn acts as a ferrite former and in another it does as an austenite former. In this report, analysis of alloying elements in phases forming Cr-Ni stainless steel was made using Electron Probe X-ray Micro analyzer in order to study the effect of Mn on the structures of Cr-Ni stainless steels and the relations between the structures and mechanical properties such as impact value, deformation resistance and hot work ability were investigated.
The following results were obtained.
1) Th amount of δ ferrite decreased with increasing Mn content for martensitic stainless steels but it increased with increasing Mn content for austenitic stainless steels.
2) Impact property was improved with increasing Mn content in the specimens as solutiontreated but impact values of the specimens aged at 750°C decreased with increasing Mn content because an addition of Mn promoted the formation of σ phase from δ ferrite.
3) Deformation resistance at high temperature increased with increasing amount of alloying elements but it decreased with increasing amount of δ ferrite.
4) Hot work ability of the specimens with duplex structure was worse than that of the specimens with single phase.
It was not the amount of δ ferrite but the duplex structure itself that had a bad influence on hot work ability.