질소첨가에 따른 주조용 CD4MCU 이상 스테인레스강의 분위기에서의 저속인장 거동 = Slow Strain Rate Tensile Behavior of CD4MCU Cast Duplex Stainless Steel with Different Nitrogen Contents

다국어 초록 (Multilingual Abstract)

The effect of nitrogen contents on the microstructure, tensile and corrosion behaviors of CD4MCU (Fe-25Cr-5Ni-2.8Cu-2Mo) cast duplex stainless steel was examined in the present study. The slow strain rate test was conducted at a nominal strain rate of 1×10^-6/sec in air and 3.5%NaCl+5% H_2SO_4 solution for studying the stress corrosion cracking behavior of the present alloy. It was observed that the volume fraction of austenitic phase in CD4MCU alloy increased from 49% to 65% with increasing nitrogen content from 0.13 to 0.27 wt.%. The yield strength decreased, while the ultimate tensile strength and the tensile elongation increased, with increasing nitrogen contents. The variation of tensile behavior appeared to be strongly related to the volume changes in ferritic and austenitic phases associated with different nitrogen contents. The increase in the volume fraction of austenitic phases was beneficial for both general corrosion and stress corrosion cracking in 3.5% NaCl+5% H_2SO_4 solution. It was believed that the selected corrosion of ferritic phases in high austenitic duplex stainless steel smoothened the initial stress corrosion cracks and, consequently, increased the resistance to stress corrosion cracking.