Study On Mechanical Properties And Wear Resistance Of Microalloyed Low Alloy Wear Resistant Steel

As a kind of wear-resistant steel material that can effectively resist wear,micro-alloyed low alloy wear-resistant steel is widely used in the production of various types of mechanical equipment.At present,the micro-alloyed low-alloy wear-resistant steels produced by domestic steel mills often suffer from unstable performance.In view of this,the mechanical properties of NM500 wear-resistant steel and HARDOX 450 wear-resistant steel were studied using hardness testing,quasi-static tensile and low-temperature impact experiments in this paper.SEM,EDS,TEM and EBSD techniques were used to study the microstructure and fracture morphology of wear-resistant steel.The second quenching of NM450 wear-resistant steel at different temperatures(860,880,900,920 ?)were carried out,and then compared mechanical performance testing,microstructure observation and wear resistance performance to obtain a secondary quenching process which can make the steel get stable mechanical properties and excellent wear resistance.The specific research results of this article are as follows:The mechanical properties of NM500 steel are uneven due to the large difference in the thickness direction.Tensile fractures are characterized by tearing ridges,quasi-cleavage planes and tearing of ligaments.There are two kinds of fracture morphology of micron TiN on the fracture surface: TiN is on the fracture surface and itself is on the tear ridge;TiN is on the bottom of the deep tough socket.There are three kinds of fracture mechanisms in the micron TiN of steel under tensile stress: A single crack appears in TiN initiates and spreads to the matrix.A single crack appears in TiN initiates but stops at the matrix.A plurality of cracks are generated in the TiN,and the crack stops at the base,with the TiN shape being preserved intact.The matrix structure was studied by EBSD technology,and it was found that there are several high strain regions and micron TiN in the NM500 wear-resistant steel,and the original austenite grains are coarse.After the cracks are generated on the TiN,the matrix has poor crack arrest ability,which makes the cracks easily extend on the substrate.So the plasticity of steel is poor.HARDOX450 steel has uniform mechanical properties and small structure and grain size.Tensile fractures are dominated by tough dimples and separation cracks.Low-temperature impact fractures are characterized by river-like patterns,sheared dimples and cleavage planes.The TiN on the cross-section is at the bottom of the deep tough socket.In order to explore the law of TiN precipitation,the simulation calculation found that TiN precipitated in the solid state,therefore,the content of micron TiN in HARDOX450 steel is low.There are three kinds of fracture mechanisms for micron TiN in the HARDOX450 steel: After the spontaneous nucleation of TiN,a single crack initiates and stops at the matrix;TiN heterogeneous nucleation and cracks germinate at the core and stop at the matrix;After the spontaneous nucleation of TiN,many cracks initiated,but stop at the substrate.The reason why HARDOX450 steel has good mechanical properties is that there is no high strain zone in the steel,and the fine structure and grains hinder the main crack growth during the stretching process.The gap between wear-resistant steel at home and abroad mainly lies in the uniformity of mechanical properties,and the main influencing factors are the structure and grain size and uniformity.Therefore,the structure was refined by secondary quenching at different temperatures to obtain excellent mechanical properties and wear resistance.It was found that the average grain size of the samples obtained by secondary quenching at 880 ? was the smallest,and the structure changed from elongated martensite to short in the raw material.The structure is transformed from slender martensite in the raw material to stubby martensite,the sample has the highest hardness and the strongest strength;As the secondary quenching temperature increases,the plasticity continues to increase.After 6000 times of three-body impact wear test,it is found that the wear surface of NM450 steel without secondary quenching is furrow,micro-cutting and fatigue damage;Secondary quenching can effectively improve the wear resistance of NM450 steel.The sample obtained by secondary quenching at 880 ? has the least wear and the best wear resistance and the worn surface is scale peeling and fatigue damage;HARDOX450 steel wear surface is fatigue damage.