DEVELOPMENT OF CONTINUOUSLY ANNEALED HIGH STRENGTH COLD ROLLED SHEET STEELS.

The application of a continuous annealing line equipped with a water quenching device (WQ-CA method) to the production of high strength cold rolled steels has been studied. The use of WQ-CA method makes possible the economical production of steels with superior ductility. The basic heat cycle is composed of water quenching from intracritical temperatures and subsequent tempering at low temperatures, leading to the ferrite-martensite composite microstructure of the products. The tempering is carried out to thermally stabilize the steels, its desirable temperature being 200 degree to 300 degree C. For steels with guaranteed tensile strength above 50 kg/mm**2, the addition of silicon and/or phosphorus is recommended because it improves ductility. Yield stress increases in course of paint-baking, i. e. , bake-hardenability, together with a good anti-aging property at room temperature.