Effect of Annealing Temperature on Microstructures and Mechanical Properties of 1000MPa Grade Cold Rolling High-Strength Steel on Ultra-Fast Cooling Condition

The effect of annealing temperature on microstructures and mechanical properties of 1000MPa grade cold rolling steel was studied under the condition of ultra-fast cooling in the present investigation. The component of the experimental steel has been designed and the carbon content is 0.13%[wt]. A small amount of V and Nb were added to the steel. Simulated annealing steel experiment has been carried out in the laboratory condition. The experimental steel was heated to 780°C, 800°C, 820°C, 840°C, 860°C for 80s, then slowly cooled to 680°C, and finally water quenched to room temperature. The aging temperature was 240°C(for 240s) and then the steel was air cooled to room temperature. Using optical microscope, scanning electron microscopy (SEM) and tensile testing machine to analyze and test the microstructures and properties of the steel after annealing process. The result showed that the microstructures of the annealed steel was martensite and ferrite, and when the annealing temperature was 820°C, the tensile strength could reach 999MPa, elongation could reach 13.3%. It was easy to see that the tensile strength increased and the elongation decreased with the increase of annealing temperature.