Effect of Initial Microstructure on Final Mechanical Properties of Quenched and Tempered High Strength Steel Plates

In order to develop 960MPa in yield strength steel plates for engineering machinery by quenching and tempering technology,the effects of rolling and cooling on microstructure and mechanical properties after heat treatment were investigated.The results showed that initial structure before quenched and tempered processes was determined by various rolling and cooling modes.And then the final mechanical properties after heat treatment were influenced by initial microstructure.When controlled rolling and controlled cooling process was performed, the initial microstructure composed of granular bainite and a few martensite phases could be obtained. And the dispersed M/A constituent distributing in the matrix showed mainly stripy feature.In this case,the experimental steel after heat treatment could achieve optimum mechanical properties,the yield strength is 1033MPa,the tensile strength is 1053MPa and the Charpy impact energy at -40℃could reach 173J.All indexes could meet the requirement of national standard.