The quenching at different temperatures for different heating time of B800 NQ steel was carried out by using salt bath furnace. The microstructure of the heat treated sample was observed by scanning electron microscope, and the mechanical properties were detected with the universal tensile testing machine. The results show that, when quenching temperature is 930 ℃, the microstructure is mainly the lath martensite. With the increase of heating time, the martensite microstructure changes little, and the mecha...