Study on Deformation Behavior of Non–Hardenable Austenitic Stainless Steel (Grade X5CrNi18–10) by Hot Torsion Tests

The steel’s deformation resistance, in which high strain rates have an important influence on the mechanism of failure, might be obtained from asuitably instrumented torsion test. Determination of stainless steel deformability by hot torsion test is the only method that allows obtaining large deformationsalong the length of the test specimen, so it is mainly used to determine the characteristics at large plastic deformations. By this method, the hot deformabilityof stainless steel is determined by subjecting to hot torsion the cylindrical stainless steel specimens maintained at the deformation temperature in a tubularoven belonging to the Laboratory of Metal Rolling and Plastic Deformation, at the Faculty of Engineering – Hunedoara, University Politehnica Timişoara. Forthe experimental hot torsion tests, several stainless steel grades were used and included in a large series of studies destined to determining the deformationbehavior of steel. Having in view the previous results obtained in the study of deformability characteristics of two stainless steels (hardenable martensiticstainless steel, grade X46Cr13 and non–hardenable ferritic stainless steel, grade X6Cr17), this paper includes the results of the hot torsion tests conducted tofind the deformation behavior of the non–hardenable austenitic stainless steel (grade X5CrNi18–10). For analysis of laboratory hot torsion tests results theunivariate and multivariate regression analysis was used, estimating the relationships among the hot–testing temperature, torque moment and number oftorsions up to the breaking point of the specimens of austenitic stainless steel. Therefore, the optimum range of heating temperatures applied for deformingthe studied steels results clearly from the deformability – temperature (plasticity – temperature and deformation resistance – temperature) diagrams.Correlations are useful because they can indicate a predictive relationship that can be exploited in the laboratory or industrial practice.