Effects Of Cold Rolling And Annealing On The Microstructure And Properties Of A High Nitrogen Austenitic Stainless Steel

High nitrogen austenitic stainless steel (HNASS) having excellent mechanical properties, corrosion resistance, oxidization resistance, wear resistance, etc. is more and more widely used in energy resources, chemical industry, fertilizer product, oil, natural gas, mining and communication, transport etc. As a result, great attention is now focused on high nitrogen austenitic stainless steels by researchers of many countries.The Fe-18Cr-18Mn-0.63N high nitrogen austenitic stainless steel was adopted as the target materials in the present work. First, the precipitation of the second phase particles and corresponding mechanical property were investigated through optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the mechanisms for the effect of cold deformation on the precipitation and.mechanical property were discussed. Then, the electron backscatter diffraction (EBSD) technique was to stuy the effect of cold-rolling and annealing on the grain boundary character distribution (GBCD) in the experimental steel. The evolution behavior of GBCD was discussed.The precipitation of the experimental steel after20%cold deformation is similar to that after solution heat treatment and they are both cellular Cr2N phase. The precipitation of the experimental steel is granular Cr2N phase and a phase after50%cold deformation.In the solid-solution treated steel, the precipitation of the second phase particles results in the decreases in ultimate tensile strength (UTS), yield strength (YS) and elongation with increasing aging time. In the steels cold-deformed by20%or50%and then aged for lhr, the strain recovery or recrystallization mainly contributes to the decreases in UTS and YS and the increase in elongation. The cellular Cr2N precipitation in the steel cold-deformed by20%and the granular precipitation in the steel cold-deformed by50%play a dominant role, which causes the decreases in UTS, YS and elongation with continually aging.Cold deformation, annealing temperature and annealing time have significant effects on the formation of special boundaries in the experimental steel. Cold-rolling by5%followed by annealing at1150℃for10min is the most feasible for the optimization of GBCD in the experimental steel under the current experimental conditions. The proportion of special boundaries increases from47.3%for the solid solution treated high-nitrogen austenitic stainless steel specimen to82%for the specimen cold-rolled by5%and then annealed at1150℃for10min. These special boundaries of high proportion can effectively interrupt the connectivity of general high angle boundaries network, achieving the anticipated effect of GBCD optimization for HNASS.