Effects of annealing temperature on microstructure and properties of tailor-rolled blank of medium-manganese steel

The microstructure and mechanical properties of tailor-rolled blank (TRB) of medium-manganese steel during annealing were investigated. The annealing process of austenite-reverted transformation of the experimental steel was formulated. The effects of different morphologies on properties with different annealing temperatures in different thickness zones of TRB were analyzed. In the thin zone, the morphology is blocky, and in the thick zone, the morphology is lamellar. At the same annealing temperature, the tensile strength of the thick zone is lower than that of the thin zone, and the elongation and product of strength and elongation (PSE) of the thick zone are higher than those of the thin zone. With the increase in annealing temperature, the tensile strength increases, while the yield strength, the elongation and the PSE all decrease in the same thickness zone. Because the stability of lamellar austenite is higher than that of blocky austenite, the comprehensive mechanical properties in the thick zone are good. At the annealing temperature of 640 °C, the experimental steel has the best comprehensive mechanical properties, and the maximum PSE is more than 40.0 GPa% in different thickness zones. Particularly, PSE is up to 45.6 GPa% in the thickness zone of 2.0 mm.