Research On The Role Of Rare Earth In NM450 Wear-Resistant Steel

Wear is one of the main forms of steel failure,which will cause huge economic loss and waste of resources,and even lead to malignant accidents.Compared with foreign countries,there is a certain gap in the comprehensive quality of low-alloy wear-resisting steels in China.Therefore,the research and development of low alloy wear-resistant steel with excellent comprehensive mechanical properties and wear resistance is of great significance to reduce wear loss and prolong the life of equipment.China has abundant rare earth resources.With the continuous improvement of the cleanliness of molten steel,the inclusion modification and micro-alloying of rare earth are increasingly prominent.Therefore,this paper takes NM450 low alloy wear-resistant steel as the research object,uses 50kg high temperature induction furnace to carry out the high-temperature simulation experiment of rare earth treatment of NM450 wear-resistant steel,systematically studies the influence of rare earth on the occurrence state of inclusions in the steel,the micro structure and mechanical properties of the steel and the wear resistance.The research results will provide a theoretical basis for the development of rare earth wear-resisting steels with the characteristics of Chinese resources.Under the present experimental conditions,the following main conclusions are obtained:(1)After rare earth treatment of NM450 wear resistant steel,the number and size of inclusions are significantly reduced,and the cleanliness of liquid steel is improved.The Al2O3 inclusions in NM450 wear resistant steel can be modified into CeAlO3 inclusions by rare earth treatment,and the CeAlO3 inclusions with high melting point can be further modified into CaOAl2O3-Ce2O3 inclusions with low melting point.When w(Ce)is 0.0037%,fine and dispersed Ce2O2S,CeS,and CeP inclusions are generated,which inhibit the precipitation of MnS inclusions.(2)The raw austenite grains of NM450 wear-resistant steel treated with rare earth are refined and distributed more evenly than those without rare earth.The strength,elongation after fracture,Brinell hardness and impact toughness of the experimental steel are all improved,especially the impact toughness is significantly improved.(3)The addition of Ce can significantly improve the wear resistance of NM450 wear resistant steel.In the range of w(Ce)from 0 to 0.0037%,the wear weight loss of the experimental steel decreases gradually with the increase of Ce content.Experimental steels with added rare earth have obvious advantages in resisting abrasive embedding and crack propagation.(4)Under the impact load,a plastic deformation zone(subsurface)with a thickness of 10～30μm is formed on the surface of NM450 wear-resistant steel,and the resulting work hardening enhances the microhardness of the surface of the experimental steel.With the increase in the mass fraction of Ce in the steel,the toughness and plasticity of the steel are enhanced,and the subsurface thickness is increased,which significantly improves the wear resistance of the experimental steel.