Patent ID: 7976651
Filing Date: 2011-07-12
Classification: C21D,C22C

Abstract:
1. A method of producing weldable automobile parts, which comprises steps of: forging the weldable automobile parts at a temperature of 1050° C. or higher and shaping the weldable automobile parts; reheating to A quenching and tempering to a pre-determined hardness, wherein the weldable automobile parts consist essentially of, by weight %, C: 0.10-0.16%, Si: 0.05-0.50%, Mn: 1.3-2.3%, Cu: up to 0.5%, Ni: up to 0.5%, Cr: up to 0.8%, Mo: up to 0.3% and Ti: up to 0.06%, and the balance of Fe and inevitable impurities, and satisfy the condition that the weld-cracking susceptibility, Pcm, defined by the formula 1A below is less than 0.35, and the condition that the manganese equivalent, Mneq, defined by the formula 2A below is larger than 2.0, wherein wherein the forging includes a first forging of the steel at a temperature of 1050° C. or higher followed by at least one another forging to give shape to the weldable automobile parts, the last forging being carried out at a temperature of 900-1000° C., and directly quenching after the last forging.