Study On The Regulation Of Microstructure And Mechanical Properties Of High Nitrogen Austenitic Stainless Steel

High nitrogen austenitic stainless steels have a good balance of strength andthoughness, stable microstructure, good corrosion resistance, do not have any magnetism.They can be used in industry field like electricity, transportation. The manufacturing costof high nitrogen austenitic stainless steel are higher than conventional austenitic stainlesssteel because its processing like melting,rolling are more difficult when mass percentageof nitrogen is over0.4%.It is necessary for reaserchers to study its microstructureregulation and mechanical properties as a trendency of better performance properties andcheaper cost.This paper focus on austenitic stainless steel of more than0.6%nitrogen,whose yield strength is about1000MPa.Gleeble and roll were used to study thenfluence of hot working parameters on microstructure and mechanical properties.The microhardness and microstructural evolution of high nitrogen austenitic stainless steel under various deformation temperature and strain was characterized bygleeble3800in order to modeling the TMCP（thermal-mechanical control process）of high nitrogen austenitic steel.Results indicated that the microhardness decreased slowly in non-recrystallization region, then quikly in partly recrystallization region,atlast slowly in complete recrystallization region with temperature increasing when deforming at certain strain. In complete recrystallization region,grain refinement strengthening is the major strengthening mechanism,microhardness and mean grain size isin accordance with the Hall-Petch empirical formula. In non-recrystallization region, deformation strengthing is the major strengthing mechanism. Comparing to deform in complete recrystallization region, the effect of a higher strength increament will obtain when deform in non-recrystallization region.The high nitrogen austenitic stainless steel plates were obtained by thermo-mechanical process with different finish rolling temperature and cooling mode. The rela tionship between microstructures and mechanical properties of steel plates under various deformation conditions were investigated. The results revealed that the strengthincreased while the ductility and impact toughness decreased with decreasing finish rolling temperature.The cooling mode after finish rolling had some effect on impact toughness and little influence on strength and ductility. The precipitation of Cr2N, which is detrimental to toughness, could be found in all the plates independenton the finish rolling temperature. The amount of Cr2N precipitation was related with the cooling mode.