METHOD OF PRODUCING LARGE-SIZED STEEL CASTING AND LARGE-SIZED STEEL CASTING

摘要

PROBLEM TO BE SOLVED: To provide a large-sized steel casting excellent in toughness and a method of producing the same.SOLUTION: The method of producing a large-sized steel casting comprises a step of casting a scrap as a raw material and a step of refining a casting after passing through the casting step, the composition of the steel casting containing as a basic component, C:0.1 mass% to 0.25 mass%, Si:0.01 mass% to 0.8 mass%, Mn:0.3 mass% to 2 mass%, Cr:0.01 mass% to 0.4 mass%, Ni:0.01 mass% to 0.5 mass%, Mo:0.01 mass% to 0.5 mass% and the balance Fe with inevitable impurities. The method of producing a large-sized steel casting further comprises before the refining step, a preliminary treatment step of preliminarily treating the casting in such a manner that ferrite and perlite are a main structure and retained austenite percentage content is 1 vol.% or less, and the preliminary treatment step includes a step of heating the casting to an austenitizing temperature or more and step of cooling the heated casting to 300°C or less at a rate of 60°C/h or less.SELECTED DRAWING: None