Thermo-Calc Calculation and Experimental Study of Microstructure of SUS 410S and SUS 430 Ferrite Stainless Steels at High Temperature

Abstract

Abstract SUS 410S and SUS 430 are the ferrite stainless steel being applied in some electrical appliance industry due to their excellent corrosion resistance and considerable cold formability. They have the ferrite microstructure at room temperature, while they might have different microstructure at high temperature. Since the microstructure may have remarkable effect on the hot ductility and thus the hot workability, it is of importance make some investigations. This paper summarized the studies of the microstructure of SUS 410S and SUS 430 ferrite stainless steels at high temperature by means of optical microscope with main attentions paid to the volume fraction of ferrite and austenite phases at different temperatures. It was found that both steels have the duplex structures consisting of two phases: austenite and ferrite at high hot working temperatures, which was different from that at room temperature. The thermodynamic calculation for the microstructure of SUS 410S and SUS 430 at high temperature was carried out by means of Thermo-Calc and the calculation results agreed well with the experiment. Since austenite and ferrite phases have different hot workability during hot working, it is of importance to balance their fraction to get optimum hot workability for both ferritic stainless steels. Based on these studies, the optimum hot working parameters to avoid any hot cracking can be decided.