Mod. 440A 마르텐사이트계 스테인리스강의 기계적 성질과 내식성

Abstract

In this study, the effect of temperature, the volume fraction of residual and tempered carbide on the mechanical properties, corrosion resistance of Mod. 440A martensitic stainless steels were investigated using specimens obtained by quenching and tempering with different temperature and time. The results obtained from this study are as follows: The amount of remaining carbide has decreased with an increase in the austenitizing treatment temperature, and all carbides were completely dissolved at 1250℃. The amount of remaining carbide has decreased with an increase of the austenitizing time, but the carbide remained insoluble up to 120 minutes at 1050℃. By increasing the tempering temperature, tensile strength has decreased, and elongation has increased slowly, while hardness has rapidly decreased; and the impact value remained unchanged and then rapidly increased over 500℃. The strength and hardness have slowly decreased, while the elongation and impact absorbed energy have increased with an increase in the tempering time. Cr23C6 type carbide was precipitated by temperature treatment, and sharp decrease of elongation and toughness by tempering did not appear. In tempered specimens after quenching, the volume fraction of total carbide was decreased with the increase of austenitizing temperature. In tempered specimens after quenching, strength was decrease and elongation was increased with the increase of austenitizing temperature. Tensile strength was increase and elongation was decreased with the increase of volume fraction of residual and total carbides. Tensile properties of Mod. 440A martensitic stainless steel was affected greatly by residual carbide than precipitated carbides produced by tempering. Pitting resistance was increased with the increase of austenitizing temperature. With the increase of volume fraction of residual and total carbides, pitting resistance was decreased. Pitting resistance of mod. 440A martensitic stainless was affected greatly by residual carbides than precipitated carbides produced by tempering.