수퍼 2상 스테인리스강 용접재의 저온인장성질과 내응력부식성 = Mechanical Behavior;Low Temperature Tensile Properties and Stress Corrosion Cracking Resistance in the Super Duplex Stainless Steels Weldments

다국어 초록 (Multilingual Abstract)

Low temperature tensile properties and SCC resistances of super duplex stainless steels and their weldments are investigated. Tensile strengths increase remarkably with decreasing test temperature, while elongations decrease steeply at -196℃ after showing peak or constant value down to -100℃. Owing to the low tensile deformation of weld region, elongations of welded specimen decrease in comparison to those of unwelded specimen. The welded tensile specimen is fractured through weld region at -196℃ due to the fact that the finely dispersed ferrite phase in the austenite matrix increases an opportunity to supply the crack propagation path through the brittle ferrite phase at low temperature. The stress corrosion cracking initiates preferentially at the surface ferrite phase of base metal region and propagates through ferrite phase. When the corrosion crack meets with the fibrously aligned austenite phase to the tensile direction, the ferrite phase around austenite continues to corrode. Eventually, fracture of the austenite phase begins without enduring the tensile load. The addition of Cu+W to the super duplex stainless steel deteriorates the SCC resistance in boilling MgCl₂ solution, possibly due to the increment of pits in the ferrite phase and reduction of N content in the austenite phase.