GCD 50 구상흑연주철의 기계적 성질에 미치는 퀜칭매질의 영향

Abstract

Effect of quenching medium on the Mechanical properties of ductil iron GCD 50 has been investigated using GCD 50 specimen. The specimens have been austenitized for 2 hours at 900℃, followed by controlled cooling to 800℃ by cooling rate of 0.05℃/sec and austempered for 1 hour at 380℃, 330℃, 280℃ and 230℃. hardenability was improved by using new method with the addition of 5% water to the salt. The specimens treated in the salt of with the addition 5% water have been higher hardenability and higher tensile strenght, but elongation was similar to cast specimens. Elongation and impct energy were increased with the increasing of volume fraction of retained austenite. The increasing of cooling rate of the salt due to the addition of 5% water to the salt which resulted wit the increasing of volume the fraction of retained austenite, resulting in the formation of fine bainitic ferrite.