HIGH STRENGTH FREE-CUTTING MICROALLOYED STEEL HAVING EQUALITY QUALITY OF QUENCHING AND TEMPERED CARBON STEEL, AND METHOD FOR PRODUCING THE SAME

摘要

PURPOSE: High strength free-cutting microalloyed steel and a method for producing the same are provided to reduce cost through the extension of drill lifespan and to enhance productivity through the decrease of a drill replacing time. CONSTITUTION: A method for producing high strength free-cutting microalloyed steel is as follows. Ingot steel is cast, coagulated and re-heated, which comprises C of 0.35-0.50wt%, Si of 0.40-0.70wt%, Mn of 1.30-2.00wt%, S of 0.010-0.060wt%, Cu of 0-0.30wt%, Cr of 0.10-0.30wt%, Al of 0-0.050wt%, V of 0-0.10wt%, Zr of 0.020-0.080wt%, N of 0-80ppm, Fe and other inevitable impurities. After the re-heated steel is hot-rolled, it is heated at a temperature range of 1150-1250C, is hot-forged and is air-cooled.