Optimization of high temperature quenching and tempering process of 590 MPa high-strength steel plate used in ship

In order to improve comprehensive mechanical properties of 590 MPa high-strength steel plate used in ship,the tempering process of HQ60T steel plate with thickness 40 mm was studied.Different primary microstructures were firstly obtained by means of different tempering processes,then experiments of different quenching and tempering processes were done.Microstructure analysis and mechanical properties experiments of different test samples were conducted,and microstructure of different test samples was observed in detail,moreover,the evolving rule and properties affected by microstructure of test samples were discussed.Experimental results indicate that,when the tempering temperature is increased in the same quenching and tempering process,strength of the steel plate is depressed,and its tenacity is increase;when the quenching temperature is increased in the tempering process of 580 ℃,tenacity of the steel plate is depressed after the increase within a certain range,and the peak value appears at 920 ℃;when the tempering temperature is over 580 ℃,tenacity of the steel plate is depressed,and its strength is depressed rapidly.The best comprehensive mechanical properties of the steel plate occur in 920 ℃ quenching in water and 580 ℃ tempering.