Microstructure and wear resistance of NR400 high strength bainitic wear-resistant steel plate
The microstructure of NR400 wear-resistant steel plate consists of a martensitic matrix, with bainite islands and network. The bainite network consists of low C hardness and S-C-Mn-Ni-Cr particles. At the same time, a semi-martensite/fee-martensite structure of acicular ferrite (AF) /prior austenite (PA) develops. The AF-PA structure consists of a Fe-Mn-C-Ni-Cr triplet, with a low C hardness. Alloy elements; Ni, Cr, Mo and Cu can enhance the impact toughness and wear resistance of NR400.
In order to improve wear resistance, it is proposed to optimize the thermal processing parameters during the quenching and tempering process. During quenching and tempering, the hardness is reduced and the impact toughness is improved slightly. Typical hardness can achieve HRC45-50, and the impact toughness is 10J-14J (single point). The microstructure mainly consists of martensite and bainitic matrix with a small amount of AF and PA. The wear-resistant layer remains relatively flat, and the wear is uniform.
The Bainitic Microstructure of NR400 Wear-Resistant Steel Plate
To meet the requirements of the industry, it is necessary to use different hardfacing materials to further enhance the wear resistance of the NR400 wear-resistant steel plate. The most commonly used hardfacing materials are high manganese wear-resistant plate and high chromium wear-resistant plate. The high chromium wear-resistant plate can obtain high hardness and wear resistance up to HRC58-62 after being thermally processed by submerged arc welding, and the single impact toughness is 20～25J. The high manganese wear-resistant plate has good wear resistance and is generally treated by electric arc welding, with a reliable chemical composition and high thermal stability.
In order to improve the overall performance of the NR400 wear-resistant steel plate, different surface treatments can be adopted. Common surface treatments include quenching and tempering, shot blasting, sandblasting and knurling. Quenching and tempering by heating to high temperature (above 930℃) and cooling rapidly can improve the wear resistance and impact toughness of the steel plate material. The shot blasting method is to use high-speed steel shot to blast the surface of the steel plate, which can improve the adhesion force between the steel plate and the hardfacing layer. Sandblasting is the use of high-speed sand to grind the surface of the steel plate, which can improve the wear resistance of the steel plate material. The knurling method is to press, emboss and grind the surface of the steel plate to improve the wear resistance of the steel plate.
Hardfacing Materials on NR400 Wear-Resistant Steel Plate
In conclusion, NR400 high strength bainitic wear-resistant steel plate has excellent wear resistance and impact resistance, which makes it suitable for use in the harsh working environments of the mining industry, construction machinery and steel industries. The microstructure of the material consists of a martensitic matrix, bainitic islands and networks, and semi-martensite/free-martensite (AF/PA). In order to further improve the wear resistance of the steel plate material, different hardfacing materials can be applied, such as high manganese wear-resistant plate and high chromium wear-resistant plate. After quenching and tempering, shot blasting, sandblasting and roll knurling, the wear resistance of the steel plate can be further improved.
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