Effect of Annealing Process and Cold Reduction Ratio on Microstructure and Mechanical Property of 350MPa Grade Structural Hot Dip Galvanized Steel Sheets

Hot rolled 350MPa Grade structural hot dip galvanized steel sheets was used to study the effect of annealing process and cold reduction ratio on the microstructures and mechanical properties. The results showed that the experimental steel was recrystallize finished after cold rolling follow different cold reduction ratio and Salt-bath annealing (annealing temperature 750°C and soaking time 60s) under experimental condition. When the cold reduction ratio was increased, annealing temperature was above 720°C, the yield strength and tension strength had no significant change. The annealing temperature was 750°C,the elongation had no significant change . when the cold reduction ratio was increased,the plastic strain ratio value reduced, and the strain hardening exponent value was gradually increase. In the end, that suggested the optimal annealing temperature is 750°C,and cold reduction ratio is 55% to 65%, consequently that obtained good match of mechanical properties and punching property.