Basic Research On Hot Deformation Behavior Technology Of High Nitrogen Nickel-free Austenitic Stainless Steel

For the reason that China is a poor country for nickel,the cost of austenitic stainless steel is high.In order to solve this problem,researchers have developed high nitrogen stainless steel.Few reports can be found for the hot working of high nitrogen austenitic stainless steel.Especially about the difference of hot working rules between high nitrogen steel and non-nitrogen austenitic stainless steel.Therefore,it is necessary to conduct systematic research in this respect.Heat treatment is done to the nitrogen 0.7% experiment steel under cast and forging state.With the increase of temperature and holding time,the grain size of the two organization showed the tendency of growing up.In order to make the precipitate of nitrogen 0.7% steel dissolve sufficiently and abnormal grown grain not easy to appear in the organization,the heating temperature should not be higher than 1200 ? and the holding time is 1h.When the heat treatment for the nitrogen 0.7% steel at the temperature is 800?,layer deposition will appear in the grain boundary of the original grain crystal which the composition is Cr2 N and austenite after transformation.Researches of different deformation parameters for the influence of hot deformation by experimental steels with nitrogen content of 0%?0.45%?0.7% are carried;The constitutive equations is constructed by mathematical model.The apparent activation are QN0.45=823.31KJ/mol,QN0.7=524.84KJ/mol,QN0=479.59KJ/mol.After microstructure observation,with the increase of temperature and reduce of strain rate,the more of dynamic recrystallization grains and the complete of the dynamic recrystallization;the increase of nitrogen content can promote the dynamic recrystallization.The N0.7 test steel was subjected to high temperature tensile test.At the same strain rate,the temperature increases,the deformation resistance decreases,and the plasticity increases.At1200 ?,the strain rate increases and the deformation resistance increases,and the thermoplasticity increases due to the temperature effect.