HIGH STRENGTH HOT ROLLED STEEL PLATE EXCELLENT IN UPSET BUTT WELDABILITY AND FORMABILITY AND ITS PRODUCTION

摘要

PURPOSE: To produce a 780N/mm² class high strength hot rolled steel-plate excellent in upset butt weldability and formability and suitable for the production of an automobile wheel rim. ;CONSTITUTION: This high strength hot rolled steel plate having a compsn. essentially contg., by weight, 0.07 to 0.12% C, 0.1 to 0.6% Si, 2.0 to 2.5% Mn, 0.025 to 0.060% Nb and 0.10 to 0.15% Ti, having a fine-grained ferritic structure with ≤5μm average grain size as rolled, ≥780N/mm² of tensile strength, product of the tensile strength TS (N/mm²) and uniform elongation U-E1 (%) is regulated to ≥10000N/mm²%, and the method for producing the same is provided. If required, either one kind among Ca and rare earth metals may be incorporated therein. Thus, the plate thickness of a wheel rim can be reduced, and it contributes to the lightening of an automobile weight.;COPYRIGHT: (C)1995,JPO