Effects of Cooling Methods after Hot-Rolling and Cold Rolling Reduction Ratio on Microstructure and Mechanical Properties of Cold Rolled Ti-IF Steel Sheet

Taking industrial Ti-IF steel sheets prepared under laminar cooling and ultra-fast cooling conditions as tested materials, and the effects of cooling methods after hot-rolling and cold rolling reduction ratio on microstructure and mechanical properties were studied. The results show that when the cold rolling reduction ratio was 65% and 75%, comparing with the laminar cooling, the Rp0.2of the steel under ultra-fast cooling was overall low around 10 MPa, the n value was high 0.02 and the r value slightly higher. When the cold reduction ratio was 55%-85%, the Rp0.2 was 100-120 MPa. The optimal processes were ultra-fast cooling after hot rolling, PY400 temperature of 780 ℃, cold reduction ratio of 65%-75% and the annealing temperature of 730 ℃. At the optimum processes, the tested steel had a lower yield strength and good stamping performance.