Heat untreated steel for the hot forging, a process for the preparation of a forging produced therefrom and forging

摘要

PURPOSE: To impart high tensile strength, high yield strength and high toughnee to non-refining steel by specifying the contents of C, Si, Mn, Cr, S, V and N in steel and specifying the carbon equivalent and the value of a bainite transformation starting point. ;CONSTITUTION: The compsn. of steel is constituted of, by weight, 0.15 to 0.40% C, 0.90 to 3.00% Si, 1.20 to 3.00% Mn, 0.10 to 0.50% Cr, 0.03 to 0.10% S, 0.05 to 0.50% V and 0.0080 to 0.0200% N, and the balance Fe with inevitable impurities. Furthermore, the carbon equivalent expressed by Ceq(%)=C+0.10(% Si)+0.18(%Mn)+0.21(%Cr)+0.328(%V) is regulated to ≥0.82%. Moreover, the value of a bainite transformation point expressed by Bs(K)=1152-618(% C)-25(%Si)-76(%Mn)-55(%Cr)-127(%V) is regulated to ≤810K. In this way, the stock for hot forging having about 1000MPa tensile strength and high toughness and in which high yield strength can be realized in a hot forging and non-refining state can be obtd.;COPYRIGHT: (C)1994,JPO