Study On Mechanical Properties And Fracture Behavior Of Low Alloy Wear-resistant Steel

Wear-resistant steel is usually used to make lining plates,toothed plates,hammers and other metal components.These parts must be made of materials with good strength,toughness and wear resistance.This paper mainly focuses on a typical low alloy wear resistant steel,through the study of its mechanical properties,enrich the characteristics of low alloy wear resistant steel products in different shapes and under different working conditions.The mechanical properties of low alloy wear-resistant steel were studied by hardness test and quasi-static tensile test.SEM and EDS techniques were used to analyze the structure types,inclusions and precipitates distribution,and to study the influence of the structure types on the mechanical properties of materials and their role in the crack growth process,as well as the morphological changes of inclusions and precipitates in the fracture process of materials.The research results of this paper are as follows:The mechanical properties and fracture behavior of low alloy wear resistant steel were studied by tensile tests under different strain rates.With the increase of strain rate,the tensile strength and yield strength of the material increased,the average dimple size increased gradually,the elongation of the material decreased,and the total area of cleavage plane on the fracture increased.Because of the microscopic segregation,the carbide distribution in the tempering microstructure of the test steel was spherical and strip.In the process of fracture,the crack deflects greatly at the junction of two kinds of tissues.Ti(C,N)inclusion rich in N is a regular polygon,single distribution,random in the matrix.Ti(C,N)rich in C is in long irregular shape and distributed along the rolling direction.Both kinds of inclusions will lead to local weakening of the material and reduce its strength and plasticity.In the process of fracture,the regular shape of Ti(C,N)rich inclusion cracks inside the formation of micro cracks,and to the inclusion and matrix junction.Ti(C,N)inclusions rich in C are distributed along the rolling direction,and cracks nucleate at the junction ofinclusions and matrix.The relationship between notch shape and mechanical properties is analyzed.Notch sensitivity coefficient and mechanical properties of v-shaped and U-shaped ring notch samples were analyzed,and smooth round bar samples were taken for comparison.The experimental results show that no matter the V-shaped or U-shaped notch,the stress concentration at the gap will occur during the tensile process,resulting in a higher tensile strength of the material than that of the smooth sample.And v-shaped gap compared with the u-shaped gap gap has more sensitive coefficient,in the process of tensile fracture in gap position of stress concentration is more obvious,the tensile results also show that V type notch specimen has a greater tensile strength,cause material in the process of tensile stress concentration,the maximum stress of greater in gaps,crack growth faster,so as to make the material of the plastic elongation decreases.The elongation after fracture of u-shaped notch is slightly higher than that of V-shaped notch,but both of them are much lower than that of smooth sample.The mechanical properties of low alloy wear-resistant steel at different thickness were studied.There are low hardness zones in the thickness center of NM400 wear-resisting steel,and there are many segregation zones on the upper and lower surfaces,which cause the hardness value to fluctuate greatly.The strength and plasticity of the thickness center sample is poor,but the standard deviation is small.The strength and plasticity of the thickness center sample is less than 1/4 thickness and 3/4 thickness.The tensile uniformity of rolled specimens is better than that of rolled specimens.The tensile strength and elongation after fracture in the thickness direction are lower than those in the transverse and rolling direction.The microstructure in the segregation zone remained strip martensite after tempering with high hardness and strength.However,the distribution of carbide at the thickness center after tempering was stripe and granular,and the hardness and strength were low.Inclusion rating Category B and DS inclusion thickness is significantly more numerous and higher in the center than in the upper and lower third.There are many Ti inclusions and large size in the center of thickness,and it is found that the ti-containing inclusions are precipitated into strips along the crystal.