APPRAISAL OF AN AUSTENITIC STEEL IN THE AS-ROLLED/SEMI-ROLLED CONDITION

Abstract

An experimental study has been made of the effect of heat treatment on the mechanical properties of austenitic grade of stainless steel used in automobile application. The present investigation was carried out in the form of material/product appraisal. It was observed that hardness was a function of heat treating temperature, time and cooling rates. The desired level of hardness -- 30 - 32 Rc can be arrived at through a number of heat treating cycles. The microstructure of the material consists of austenitic matrix and dispersed second phase namely carbides and nitrides. The nature of carbide to form was a function of heat treating temperature and time. The material behaviour, from the point of view of inclusion rating and elemental segregation was acceptable. The tensile properties stipulated in the standards namely hardness —32 HRc, 0.2% P.S. — 580 MPa, UTS —950-l200 MPa, % El —8, % RA — 10 could be obtained through various combinations of solutionzing and ageing treatments, the optimum heat treatment being solutionizing from 1150°C followed by ageing at 780°C for 10 hrs. Through the above mentioned exercise a correlation is sought to be established between structure and properties. This proved helpful in arriving at an understanding of the material's behaviour for the specified application namely as valve steel material