Cold Reduction Ratio and Annealing Temperature of 240 MPa Grade High Strength IF Steel

Hot rolled 240 MPa grade high strength IF steel sheet was used to study of cold reduction ratio and annealing temperature of experimental steel. The experimental results showed that the recrystallization had finished under different annealing temperature followed 75%-85% cold reduction ratio. To the experimental steel of high coiling temperature 710 ℃, the yield strength, tensile strength, elongation percentage, yield point elongation, plastic strain ratio and strain hardening exponent were approximate 260 MPa, 445 MPa, 37.5%, 2.14%, 0.25, 2.0. To the experimental steel of low coiling temperature 670 ℃, that were approximate 235 MPa, 369 MPa, 38.8%, 1.73%, 0.26, 2.1.Therefore, the suggested optimal annealing temperature is 840 ℃, cold reduction ratio is 75%, and it obtains optimally match of high strength and punching property.