25Cr-­7Ni-­2Mo-­4W 슈퍼 2상 스테인리스강의 미세조직 및 기계적 성질에 미치는 시효처리의 영향

Abstract

This study was carried out to investigate the effect of aging treatment on the mechanical properties of 25Cr­-7Ni­-2Mo-­4W super duplex stainless steel. The results obtained from this study is as follow: When aging at 650℃ R-phase was precipitated and at 750℃ χ-phase was deposited. R and χ phase was precipitated in the early stage of aging, and these phases were transformed to σ-phase with increasing of aging time. Ferrite phase also decomposed into new austenite(γ2)phase and σ-phase by aging treatment. The amount of σphase increased with increasing of aging time. The hardness and tensile strength with increasing aging time was increased, aging treatment time becomes longer when there is no significant change, In case of the elongation and impact toughness decreased rapidly in the early stage of aging treatment. but, there was not a big difference as aging time longer. Accordingly, the hardness and strength were affected by σ-phase elongation and impact toughness were affected by R-phase and χ-phase which was precipitated.