Abstract For heat treaters working with high-carbon steels such as AISI 1050–1095 and 52100, grain size is a critical process variable that directly affects austenitizing temperatures, soak times, hardness penetration, and overall production costs. This article examines the metallurgical differences between coarse-grain (ASTM 2–4) and fine-grain (ASTM 5–8) steels, explaining how finer grain structures impede carbon diffusion during austenitization and require higher temperatures and longer soak times than coarse-grain equivalents. The article quantifies the real financial impact of these constraints and offers practical recommendations for heat treaters, including material verification, development of material-specific processing recipes, and engineering specifications that account for reduced hardenability.
Stephen Kowalski (Sun,) studied this question.