Influence of austenitization time on the grain size and mechanical properties of a 5Cr–0.5Mo steel

Abstract This study investigated the effect of austenitization time on the mechanical properties of 5Cr–0.5Mo steel. As-received steel specimens were subjected to water quenching heat treatment with five austenitization durations (1, 2, 4, 6, and 8 h) to produce different grain sizes with a consistent microstructure. The microstructural characteristics and hardness of the resulting specimens were then analyzed. Subsequently, normalizing heat treatment was applied to three specimens austenitized for 1, 4, and 8 h to evaluate their metallographic characteristics and mechanical properties through microhardness and tensile tests. Mechanical properties, including yield strength, ultimate tensile strength, percentage of area reduction, and elongation at break, were quantified through tensile testing. Area reduction and elongation were found to decrease by approximately 50 % as austenitization (grain size increased) progressed. Additionally, yield strength and ultimate tensile strength increased by approximately 300 % and 150 %, respectively, relative to the as-received specimen after normalizing heat treatment following 1 h of austenitization. The yield strengths of normalized specimens demonstrated minimal variations across different austenitization times.