Effect of Cooling Rate and Austenite Deformation on Hardness and Microstructure of 960MPa High Strength Steel

In order to develop 960MPa grade high strength steel, the effects of cooling rate and austenite deformation on the hardness and the microstructure of high strength steel has been studied by Scanning Electron microscope (SEM), Transmission Electron Microscope (TEM), Gleeble-3500 thermal simulation testing machine and T2500 Vickers hardness tester. The results show that only when the cooling rate was higher than 10 degrees C/s and the final cooling temperature was lower than 250 degrees C, the microstructure mainly consists of martensite, and the strength of high strength steel could be above 960MPa; and austenite deformation could effectively refine the width of martensite lath, thus improving the strength and toughness.