The Research Of Mechanism Of Rare Earth In 430 Ferrite Stainless Steel

This article takes the 430 ferrite stainless steel as the study object, through systematically carries on the effect of rare earth elements on modification of inclusions, micro-alloy function in 430 ferrite stainless steel, including various influence of rare earth on nonmetallic inclusion, micro-structure, mechanical properties, corrosion resistance performance and its function mechanism.The effect of rare earth on the nonmetallic inclusion was studied by quantitative metallography, SEM, EDS.The results indicate that feasible rare earth could refinement, spheroidization of the inclusions;the scattered inclusions gatherer and grew up gradually with the increase of RE content; the categories of the nonmetallic inclusions changed from MnS,Al2O3 and aluminates to RE oxide, RE oxy-sulfide, RE aluminates and their compound after added RE into steel.The research about microstructure and grain boundary component indicate that the grain size of RE steel was refine to 8 grade of feasible rare earth contents;the dissolved rare earths were appeared in the grain boundary more than the grain, and the grain boundary was cleaned and strengthened by a trace of the dissolved RE; deleterious elements of S and P segregated in the grain boundary were reduced by REThe mechanical properties were studied by the impact test and tensile test; fracture appearances were observed by SEM and EDS.The results indicated that transverse yield strength, and transverse tensile strength change more remarkable than transverse specific elongation; the reasons of RE effect tensile properties were solution strengthening, grain size strengthening and modification of inclusions; an appropriable RE addition could improve transverse impact remarkable; when feeding RE in the 430 steel,toughness fracture area appear.The corrosion behavior of 430 ferrite stainless steel was evaluated by polarization test and electrochemical impedance spectrometry(EIS) test. The results indicated that corrosion resistance and pitting potential were raised when adding RE in 430 steel; passive film resistance of 430 steel was increased by the RE.