Dissolution behavior of nitrogen in Fe-Mn-Cr-Ni system austenitic stainless steel

摘要

Induction melting method under pressurizednitrogen gas was used to produce austenitic stainless steelsdissolved with high content of nitrogen. Fe-Mn-Cr-Ni alloy systemwas melted using Cr-nitride ferrous alloy(6wt.%N) as a mainadditive element. The concentration and dissolution behaviors ofnitrogen in as-casted alloys were investigated to clarify theeffectiveness of induction melting method under pressurizednitrogen gas and Cr-nitride ferrous alloy in producing highnitrogen austenitic stainless steels having excellent mechanical,corrosion-resistance and non-magnetic properties. Nitrogenconcentration in molten alloys was increased with increasingnitrogen pressure up to 1.5 atm. This result can be explained bySievert's law. The nitrogen concentration of about 6,900 ppm wasobtained in a molten alloy when melted at the nitrogen pressure of1.5 atm. XRD and XPS measurements were carried out toinvestigate the dissolution behavior of nitrogen in a molten alloy.Although it was failed to detect some nitrides by XRD, XPSmeasurement revealed the existence of nitride such as Cr2N.Therefore it can be concluded that the dissolved nitrogen in amolten alloy exists as two states, one is as a solid solution state,the other is as a nitride state. It seems reasonable to conclude themost of nitrogen were dissloved as a solid solution state, and somenitrogen are apt to be formed into a nitride.