Effect of Pulse Current Treatment on Microstructure and Properties of 304 Stainless Steel Ultra-thin Strip after Rolling

Abstract The annealing process is usually used to recrystallize the cold-deformed 304 stainless steel ultra-thin strip, but the whole process requires high temperature and long time. Here, we use the method of loading pulse current instead of the traditional annealing process to process the cold-rolled ultra-thin strip. After the cold-rolled sample with a thickness of 0.035 mm and a width of 6mm was loaded with 25 W pulse current for 5 minutes, complete recrystallization occurred. At this time, the measured temperature was only 540℃, and the annealing process at the same temperature and time was used. The microstructure of the sample is still dominated by deformed crystals, and the difference between the two is significant. By studying the microstructure and mechanical properties after treatment, it is found that the pulse current can greatly improve the plastic deformation ability of the cold-rolled ultra-thin strip. The reason is that the electrical effect generated by the pulse current flowing through the sample promotes recrystallization and causes grain refinement. However, the pulse current power has a threshold value. When the loading current power is lower than the threshold value, the effect is not enough to make the sample fully recrystallize. In this range, the area of recrystallization increases with the increase of power, and the fine grain chain is generated from part of the grain boundary area and develops into a large area of recrystallization. When the threshold value is exceeded, the recrystallized grain will grow again, thereby affecting the mechanical properties of the sample. This discovery provides a new idea for the recrystallization process of cold-rolled 304 stainless steel ultra-thin strip.