수퍼 2상 스테인리스강의 오스테나이트상의 함량 및 분포가 저온 기계적 성질에 미치는 영향

The effects of alloying elements Cu and Cu+W addition, distribution and content of austenite phase on low temperature tensile and impact properites of 25%Cr-7%Ni-4%Mo-0.28%N super duplex stainless steel were investigated. The dispersed structure shows lower tensile strength and shorter elongation than fibrous structure due to the neck initiation at the austenite film precipitated at prior ferrite grain boundaries. Elongation value of fibrous structure decreased with the addition of Cu and Cu+W. With decreasing tensile deformation temperature, the maximum elongation peak was resulted in the dispersed structure due to the increase of the α′ martensite content. The level of α′ martensite content was greater in dispersed structure than in fibrous one. Low temperature impact values of the dispersed structure were greater when compared to the fibrous one due to the mutual interference of austenite and ferrite phases. Impact value decreased with the addition of Cu and Cu+W for both fibrous and dispersed structures.