Development Of Hot Rolling Process For Advanced High Strength Steels And Their Practical Manufactures

Advanced high strength steels (AHSS) has higher strength and better formability than the conventional steel. So it meets the trend of energy saving of auto industry development. Steel manufacturing industries in the world have put a lot of efforts to research and produce high strength steel. Baosteel also has a lot of experiences of high strength steel producing, but as far as only using economic composition such as C-Si-Mn to produce hot-rolled advanced high strength steel is still in the blank.On the basis of laboratory studies, in order to achieve these critical processes, the laminar flow cooling device configuration and capabilities were studied and calculated. And hot rolling process control model in1880mm hot rolling line to implement step-cooling mode was developed, and hot-rolled advanced high strength steel products have been rolled successfully in Baosteel1880mm hot rolling plant.The results of this study are as follows:1. Based on the laboratory development of economical C-Si-Mn composition design of hot rolled high strength low alloy steel, such as DP (dual phase steel), TRIP (transformation induced plasticity) steel and MP (multiphase) Steel, the heating temperature during hot rolling, finishing rolling temperature, coiling temperature, step-cooling mode (cooling rate, air time, etc.) and other critical process were researched..2. To achieve these critical processes, the configuration and capabilities of laminar cooling of1880HSM have been studied and calculated. An intensive cooling-conventional cooling-intensive step-type of laminar cooling equipment configuration was established base on the calculating results. A control model to achieve step-cooling mode was developed to meet the requirements of water cooling rate control and air cooling time control of the step-cooling process.3. In Baosteel1880mm HSM line, successful trials were obtained through a step cooling mode for DP590, TRIP590, S700MC, MP1200and other advanced high-strength hot-rolled steel products. Yield strength, tensile strength and elongation of experimental steels were close to the results of laboratory experiments, which indicates that the industrial production of steel products meet the designed standards. It is to say that the designed chemical composition, key processes parameters and control models can meet the industrial production requirements. By this research, Baosteel has capability to produce AHSS steels.