EFFECT OF REVERSION TREATMENT ON STRENGTH AND DUCTILITY OF LOW C, CR-NI MARTENSITIC STAINLESS-STEEL WITH HIGH-RESISTANCE TO WELD SOFTENING

In order to develop high strength stainless steels with good ductility and high resistance to weld softening, reversion behavior of martensite to austenite of low C, Si-13%Cr-7%Ni martensitic stainless steels have been studied. Moreover, dependences of mechanical properties of reversion treated steels on austenite stability, cold rolled reduction and Si have been investigated. Main results obtained are as follows; When cold rolled steels, Mf temperatures of which are around room temperature, are heat-treated at the region between As and Af temperatures, some portions of martensite are reversed to austenite, which results in microduplex structure of ultra-fine austenite grains and tempered martensite. These steels have excelent balance of high strength and good ductility. The steel containing high Si possesses good ductility as well as high strength. Softening of welded metal dose not occur because it undergoes martensitic transformation on cooling after welding.