Evolution of microstructure and mechanical properties of cold-rolled SUS430 stainless steel during a continuous annealing process

This study investigates the effect of the annealing temperature on the microstructure, strength, elongation, and anisotropy properties of cold-rolled SUS430 stainless steel by a continuous annealing experiment. The SUS430 stainless steels of cold-rolled reductions of 84% and 60% were used in this study. The evolution of the microstructure and mechanical properties of SUS430 stainless steel during the annealing process was obtained. As continuous annealing proceeds, the softening behavior of the cold-rolled SUS430 stainless steel strip presented a two-stage trend characterized as recovery and recrystallization. Recovery mainly occurred at a temperature ranging from 600 °C to 700 °C. The hardness of the strip presented a certain decrease and unobvious change in microstructure was observed in this stage. Recrystallization of the deformed grains initiated at the temperature higher than 700 °C, and the hardness of the strip decreased significantly. The mean recrystallized grain size of the sample cold rolled to 84% and 60% reductions are 13.5 µm and 20 µm, respectively. The tensile and yield strength of the specimens decrease as annealing temperature increases, and the elongation displays a sigmoidal increase with annealing temperature. Annealing temperature has little influence on the mean Lankford value (rm); however, an increase in cold-rolled reduction from 60% to 84% increases the value of rm from 0.9 to 1.3.The yield strength Re, the elongation δ, and the quantitative relationship between the yield strength Re and the softening fraction X were determined for cold-rolled SUS430 stainless steel in the range of εCR=1.0-2.2. The results of our study provide a theoretical basis for the prediction of the mechanical properties of cold-rolled SUS430 stainless steel as well as for the development of new annealing processes.