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FINE GRAIN STEEL HAVING FIVE MICROMETERS OR LESS OF AN AVERAGE GRAIN SIZE BY HEAT-TREATING AT A LOW TEMPERATURE AFTER ADDING GRAIN REFINING ELEMENTS TO THE BASE OF HIGH CARBON STEEL, AND A MANUFACTURING METHOD THEREOF
FINE GRAIN STEEL HAVING FIVE MICROMETERS OR LESS OF AN AVERAGE GRAIN SIZE BY HEAT-TREATING AT A LOW TEMPERATURE AFTER ADDING GRAIN REFINING ELEMENTS TO THE BASE OF HIGH CARBON STEEL, AND A MANUFACTURING METHOD THEREOF
PURPOSE: Fine grain steel and a manufacturing method thereof are provided to refine grains by adding grain refining alloy elements such as silicone, molybdenum, and vanadium to the base of high carbon steel and then by performing a low heat treatment at a low temperature compared with existing bearing steel.;CONSTITUTION: Fine grain steel is composed of, in wt%: C of 0.71-0.85, Si of 0.30-1.10, Mn of 0.20-1.50, P of 0.02 or less, S of 0.06 or less, Cr of 0.25 or less, Mo of 0.05-0.50, Ni of 0.25, V of 0.30 or less, Cu of 0.20 or less, Ti of 0.003 or less, Al of 0.005-0.055, B of 0.001-0.005, O of 0.0015 or less, the remainder Fe, and inevitable impurities. A fine-grain steel manufacturing method comprises a step of heating the fine grain steel at an austenitizing temperature and a step of rapidly cooling and tempering austenitized steel. .;COPYRIGHT KIPO 2013;[Reference numerals] (AA) 880°C High-frequency heat treatment; (BB) 780°C Quenching/tempering; (CC) 840°C Quenching/tempering; (DD) Reference steel; (EE) Example 1; (FF) Example 2; (GG) Example 3
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