1.4% Mn 강의 동·정적 물성에 미치는 미세조직의 영향

Abstract

This study was carried out to investigate the effect of homogeneous microstructure and inhomogeneous microstructure on the mechanical properties and fatigue property of 1.4% Mn steel. After 88% forging and heat treatment, the microstructure of 1.4% Mn steel consisted of homogeneous and inhomogeneous of pearlite and ferrite structure. inhomogeneous microstructure has thicker eutectoid cementite and more Mn and P content than homogeneous microstructure. Tensile strength and elongation of homogeneous microstructure have the similar level with inhomogeneous microstructure. Tensile strength of homogeneous microstructure and inhomogeneous microstructure is slightly lowered from surface area to the core area, but it is not that seriously different. Elongation shows no difference in value from core and surface. In a condition of 293MPa fatigue strength, homogeneous microstructure is failed at 33,730 cycles and inhomogeneous microstructure is failed at 47,191 cycles. In a condition of 253MPa fatigue strength, both homogeneous microstructure and inhomogeneous microstructure run out of 2×106 cycles. Also, with increasing the fatigue strength, the fatigue limit of homogeneous microstructure and inhomogeneous microstructure decreased. The static and fatigue strength of the inhomogeneous microstructure specimen are slightly high, but the degree of segregation is not large, so the presence of inhomogeneous microstructure does not have a big effect.