Effect of Nb and Ti on second-phase precipitation and mechanical properties of 430 ferritic stainless steel

The influence of Ti and Nb on the microstructure,mechanical properties,and second-phase precipitation of 430 ferritic stainless steel was investigated.In addition to optical microscopy,transmission electron microscopy and X-ray diffraction analyses,tensile tests,and carbonitride extraction experiments were conducted to investigate the microscopic mechanisms.The results showed that the primary precipitates in SUS 430 ferritic stainless steel were Cr_(23)C_6,Mn_(23)C_6,and Cr_7C_3,and the primary strengthening mechanism was precipitation strengthening.When Ti was added separately,the main precipitates were TiC and TiN.However,coarse TiC adversely affected the mechanical properties of steel.When double-stabilized with Ti and Nb,coarse TiC was replaced by fine NbC.The type of precipitation was altered,and precipitation and solid solution strengthening occurred.Therefore,the tensile strength and plastic strain ratio(r-value) improved to 433.60 MPa and 1.37,respectively.