APPRAISAL OF 13 Cr 0.2C STEEL IN AS-ROLLED/HEAT TREATED CONDITION

Abstract

An experimental study has been made of the effect of heat treatment (hardening followed by tempering) - on the mechanical properties of martensitic grade of stainless steel X20Crl3 used in steam turbine applications. The present investigation was carried out in the form of material/product appraisal. It was observed that hardness in the as quenched condition was a function of the hardening temperature & ranged from 460 to 510 HV30. Tempering lead to a decrease in the as quenched hardness, the magnitude of the decrease being small on varying both:, the tempering temperature (660°C & 685°C) & period (90 min to 270 min). Microstructure in the as tempered condition retained the accicularity observed in the quenched condition. The material . behaviour, from the point of view of inclusion rating, was acceptable except for the presence of chunky refractory/slag materials. Tensile properties in the tempered condition were a function of the quenching temperature as well as tempering temperature - & time. The inconsistencies observed in the mechanical properties data could ` be satisfactory observed/resolved by plotting the mechanical properties as a function of dependent variables and through using the best fit method. Overall the PS ranged from 710-732 MPa, UTS from 776-875 MPa, %EL from 14 to 22 and %RA from 60-68. Impact 'toughness improved with tempering temperatures &-- less clearly with tempering periods. However, at the' 'lower of the two hardening temperatures, the toughness in the as tempered condition' showed a more distinctive tendency towards improvement, both with tempering temperature & periods. Through the above mentioned exercise a correlation is sought to be established between structure and properties. This proved helpful in arriving at understanding of the material's behaviour for the specified' application