초고탄소 저합금강의 강도와 인성에 미치는 열간단조의 영향

Abstract

Effect of the hot-forging ratio on the microstructure, hardness, tensile properties and impact toughness of ultra-high carbon low alloy steel was investigated. The results obtained from this study are as follows: With an increasing hot-forging ratio, the thickness of the network and acicular proeutectoid cementite decreased. Lamella spacing and thickness of eutectoid cementite decreased and were broken up into particle shapes, which then became spheroidized with the increasing hot-forging ratio. When the forging ratio was over 65%, the network and acicular shape of the as-cast state disappeared. By increasing the hot-forging ratio, tensile strength and elongation were not changed up 50 %, and then increased rapidly with the increase in the forging ratio. Strength and elongation were not affected by the thickness of the proeutectoid and eutectoid cementites, but were greatly affected by the shape of the proeutectoid cementite. With increasing hot forging ratio, hardness, tensile strength, elongation and impact value were not changed up 50%, and then hardness rapidly decreased, while impact value rapidly increased. Hardness and impact value was greatly affected by the disappeared of network and acicular shape of proeutectoid cementite, and became particle shape than thickness reduction of proeutectoid and eutectoid cementite.