Mechanisms Of Rare Earth And Mg In SS400 Steel

The samples are gained by appending RE-Mg compound to the steel. In this dissertation, the influences of RE-Mg on the inclusions, microstructure and dynamic recrystallization of SS400 are studied and analyzed.Firstly, the inclusions in different RE-Mg content sample are observed, through careful and directed attention by spectrum and scanning electronic microscope. It is found that RE-Mg compound modification can modify the inclusions in the steel very well and also control the size and distribution of the inclusions. Sulfide inclusions size decreased from 15.35μm to 9.83μm, oxide inclusions size decreased from 18.52μm to 8.79μm.Secondly, the normalizing and quenching microstructure in different RE-Mg content sample are observed, through careful and directed attention by spectrum and scanning electronic microscope. It is found that the addition of RE-Mg in steel can improve the microstructure, keep the grain smaller, increase the microhardness, decrease the inter lamellar spacing of the pearlite, reduce the amount of perlite and make the lath martensite smaller. The grain size increases from grade 7.5 to grade 9.5, the pearlite area percentage reduce from 23.16% to 16.61%. The microhardness increases from 148.2 to 187 HV.Lastly, on the heat simulation test machine, the true stress-true strain curves are mensurated to study the effect of RE-Mg in SS400 dynamic recrystallization. The resistance to deformation of SS400 steel augment, the Rs of dynamic recrystallization augment and the temperature of dynamic recrystallization increase.The addition of mini-elements (RE-Mg) can advance the quality of steel. By This approach,we can enhance the international competition ability and make the resource advantage change to variety advantage which has great meaning.