원심주조된 9Cr-1Mo 내열강의 미세조직 및 기계적 성질에 미치는 제조공정의 영향

Abstract

This study was carried out to investigate the effect of manufacturing process on the microstructure and mechanical properties in 9Cr-1Mo heat resistant steel. The result obtained from this study are as follow: The microstructure of centrifugal casted specimen, forging or ring mill after centrifugal casted specimens consisted of martensite structure. The change of manufacture process didn't effect on the microstructure of 9Cr-Mo heat resistant steel specimens. Tensile strength and hardness of centrifugal casted specimen was higher than ring mill or forging after centrifugal casted specimen, but elongation and impact value was a little lower, and centrifugal casted specimen and ring mill or forging after centrifugal casted specimen was similar. With the increase of forging starting temperature, the tensile strength slightly increased, elongation and impact value slightly decreased, and with the increase of forging finishing temperature, the tensile strength and hardness increased, elongation and impact value decreased. With the increase of forging ratio, the tensile strength and hardness increased, the elongation and impact value decreased due to be fined and hardened of martensite structure. We obtained the optimum condition was forging starting temperature; 1200℃, forging finishing temperature; 950℃, forging ratio; 30%.