The Production of Cold Rolled Steel Sheet of Extra Deep Drawing Quality by Continuous Annealing Process

Abstract

The Ti-stabilized steel has a uniform distribution of very fine precipitates (TiC) already in the hot rolled state. These prior precipitates are effective in developing a strong {111} recrystallization texture on annealing after cold rolling, and the slow heating up to annealing temperature such as undertaken for Al-killed steel to get effective precipitates or pre-precipitation clusters is not necessary forTi stabilized steel. Lowering carbon content of the steel to less than 0.01% results in great increases of the grain size and γ value in a very short time with the raising annealing temperature. The Tistabilized very low carbon steel (e. g., 0.005%C-0.1%Ti) therefore can get a very high γ value of above 2.0 even by applying a rapid annealing cycle with heating rates of 10⁴ to 10⁵°C/sec and with soaking times within a few minutes.
Quench-aging does not occur at all in Ti-stabilized steel rapidly cooled from annealing temperature, as the carbon (and nitrogen) in the steel is stabilized with titanium. Then continuous-annealed Tistabilized steel is non-aging and very soft without over-aging treatment.
The Ti-stabilized very low carbon steels is the most suitable to get a non-aging steel sheet having an extra deep drawing quality by the continuous annealing process