Influences of Quenching and Tempering Process on Mechanical Properties and Microstructures of Q690D Steel Plates

The influence of quenching and tempering process on the mechanical properties and microstructures of the Q690D high strength structural steel plates with 60 mm thick based on the same hot rolling conditions,has been studied in detail,including the theoretical analysis of the precipitated second phases.The results show that with the increase of quenching temperature,the strength of the tested steels is increased but the toughness is worse.And with the increase of tempering temperature,the strength is decreased but the toughness is significantly improved.The steel plates show an excellent match of strength and toughness when use the heat treatment process of quenching at 930 ℃(preserving the temperature for 10 min) and tempering at 650 ℃(holding 40 min),which meets the requirements of Chinese national standard of GB/T 16270—2009.