Effect of quenching temperature on microstructure and mechanical properties of Q690D steel

The microstructure and mechanical properties of a Q690D high strength steel quenched at different temperatures were investigated.The results show that when the quenching temperature is between 890 ℃ and 970 ℃,with increasing quenching temperature,the strength of the tested steel increases firstly then decreases and the maximum value reaches at 930 ℃,and variation of the impact toughness and elongation are inverse compared with the strength.When the quenching temperature is in the range from 890 ℃ to 970 ℃,the mechanical properties of the tested steel could meet requirement of Q690D steel.The grain size of prior austenite is in range from 13.2 μm to 35.3 μm with increasing quenching temperature.The coarse lath-like microstructure can be obtained from coarse austenite grain after quenching.