Strength Behaviour of Hot Die Steel with Respect to its Heat Treatment

Abstract

The surface temperature of hot die steel reaches typically up to 550ºC or above during processes like hot extrusion and casting non-ferrous material. The present paper explores the impact of austenitizing temperature as well as tempering temperature on the tensile strength of hot die steel. Heat treatment is done at three different austenitizing temperatures of 1010ºC, 1030ºC, and 1050ºC, followed by tempering done at two different temperatures of 540ºC and 580°C. Tempering is done twice for two hours. Metallographic grinding, polishing, and then etching using 2% Nital is done to investigate the microstructure of hot die steel with respect to its heat treatment. It is found that the grain size of hot die steel increases with an increase in austenitizing temperature. The impact on tensile strength of hot die steel for its heat treatment is examined by conducting the uniaxial tensile test to fracture. And investigation of the morphology of the fracture surface produced after the tensile test is done. It was found that hot die steel with large grain size exhibits lesser tensile strength. Whereas, the one having smaller grain has higher tensile strength that is found to be in accordance with the Hall-Patch equation.