Experimental Study of Continuous Annealing Process for Cold Rolled TRB Sheet

To explore the effect of continuous annealing on microstructure and properties of TRB sheet,a reversible four high cold rolling mill was used to roll a single variable gauge zone TRB sheet in laboratory.The differences of microstructure and mechanical properties of various thickness zones were investigated by continuous annealing experiments of cold rolled DP590 dual phase steel and 22 Mn B5 hot forming steel TRB sheet,which were analyzed by optical microscope and scanning electrical scope and tested by tension and hardness experiments.Resultsshow that the maximum thickness deviation in variable gauge zone of TRB sheet is less than 0. 03 mm,length deviation is less than 1 mm. The temperature of the thin zone of TBR sheet is below 57- 20 ℃ than the variable thickness zone and thick zone during cooling and over-aging phase of continuous annealing. It leads to the higher tensile strength and elongation in thin zone than others,and the almost same yield strength as that of in thick zone for DP590 steel,but higher yield and tensile strength for 22 Mn B5 steel. There are small changes of Vickers hardness in the variable gauge zone. The continuous annealing process should be determined by the thickness of the thick zone for cold rolled DP590 dual phase steel TRB sheet,which is more conducive to the mechanical properties control. Batch annealing is suggested for 22 Mn B5 hot forming steel TRB sheet.