NM400 steel plate is a kind of Chinese wear-resistant steel material, which is very popular in the Middle East and Africa. The NM400 steel plate is hot rolled, and then the plates are heat treated by direct quenching and tempering and reheat quenching and tempering techniques. The impact test is carried out with an instrumented impact testing machine. A combination of optical microscope, transmission electron microscope and scanning electron microscope was used to study the microstructure and fracture surface. NM400 has high mechanical strength, which is 3 to 5 times that of ordinary low-alloy steel plates, and can significantly increase the surface hardness, usually reaching 360-450HB.
