Effect of Annealing Process on Microstructure and Properties of Cold Rolled Strip Steel for Deep Drawing

Because of its excellent deep-drawing performance, cold-rolled strip steel for deep-drawing can get a bright surface after deep-drawing, and is widely used in various auto parts and other civilian products. The traditional hot rolling method of this kind of steel is that the rough rolling and finishing rolling temperature are above Ar3, that is, rolling in the austenite zone; while the rough rolling is rolled in the austenite zone and the finish rolling is below Ar3, it is ferrite.

Zone rolling. Considering its process performance, high-performance hot-rolled plates for direct application are produced by rolling in the ferrite zone. This new rolling process is being widely studied and has begun to be applied in practice. Regardless of whether rolling in the austenite zone or in the ferrite zone is used, the recrystallization annealing after cold rolling has a very important effect on the mechanical properties of the cold rolled strip for deep drawing.

Cold-rolled steel strip for deep drawing is annealed in a bell-type furnace. A slight change in annealing temperature affects the strip’s recovery and recrystallization behavior and has an important impact on its microstructure, resulting in different mechanical properties. After DC01 steel is annealed at 680℃, the ferrite grains are fine, and the grains are obviously elongated along the rolling direction. After annealing at 700, 710℃, the ferrite grains are slightly coarser; DC06 steel is annealed at 680, 690℃ Later, the deformed ferrite grains are more obvious.

After annealing at 710°C, the ferrite grains begin to grow. 690 and 700°C are the best annealing temperatures for DC01 and DC06 steels respectively, and their recovery and recrystallization effects are better, and excellent deep drawing performance meeting the standard can be obtained. DC06 steel contains microalloyed Ti, B and other elements, which hinder the recrystallization of metals and increase the recrystallization temperature of metals, so the cover annealing temperature is higher than that of DC01 steel. Due to the n value and r value of its deep drawing performance, DC06 steel is also better than DC01 steel.