22Cr 마이크로 듀플렉스 스테인리스강의 변형유기마르텐사이트에 미치는 Ni과 Mn의 영향

The microstructure and deformation behavior in 22Cr-0.2N micro-duplex stainless steels with various Ni and Mn contents were compared using by OM, TEM, and XRD. The 22Cr-0.2N duplex stainless steel plates were fabricated and hot rolled, followed by annealing treatment at the temperature range of 1,000-1,100℃. All the samples showed the common strain hardening behaviour during the tensile test at a room temperature. The steels tested at the temperatures of -30℃ or -50℃ showed a distinct inflection point in the stress-strain curves, which should be resulted from the formation of strain-induced martensite(SIM) of austenite phase. This was confirmed by TEM observations. The onset strain of a inflection point in a stress-strain curve should be depended up the value of Md30. With the decrease of the tensile test temperature, the inflection point appeared earlier, and the strength and fracture strain were higher. The tensile behaviour was discussed from the point of austenite stability of the micro-duplex stainless steels with the different Ni and Mn content.