Microstructure And Wear Properties Of A New High Temperature Wear Resistant Steel

In recent years,through the continuous efforts of domestic researchers,the development of conventional low alloy wear resistant steel has made great progress,and has gradually formed serialization and standardization.However,the conventional conventional low-alloy wear-resistant steels are usually obtained by using martensitic structure and obtained through the quenching and low-temperature tempering process.In actual production,the service environment of wear-resistant parts is becoming more and more severe,and horses in some high-temperature production fields.The spheroidal structure will be tempered,and the strength and hardness will be drastically reduced.The conventional grade of wear-resistant steel will lose its excellent wear resistance and will not play a good role in wear resistance.This imposes requirements on the high-temperature wear resistance of the material.On the premise of green and economical,the composition and microstructure of 400HB grade new high temperature wear resistant and wear-resistant steel are designed,and the process of phase change and final microstructure are controlled by rolling,cooling after rolling and off-line heat treatment.A new high temperature wear resistant martensitic wear resistant steel with excellent comprehensive properties such as high temperature wear resistance and high toughness has been obtained.The main research contents are as follows:(1)The microstructure evolution of experimental steel during continuous cooling was studied,and the effect of added Mo element on the type of phase transition was analyzed.The two experimental steel structures designed were martensite.When the cooling rate reached 10℃/s,both experimental steels obtained the full martensite structure.Mo element can increase the hardenability of the experimental steel and make the CCT curve shift to the right.At higher cooling rates,the hardness of the two experimental steels reaches 400HB,which meets the requirements of the national standard for hardness of conventional wear-resistant steel NM400.Since the experimental steel A contains more Mo.the hardness is higher than that of the B experimental steel.(2)The morphology and microstructure of the martensite at different austenitizing temperatures were studied,and the influence of microstructure on mechanical properties after quenching was analyzed.The strength,hardness,elongation and-40℃ impact toughness of the two kinds of experimental steels vary with the quenching temperature,but overall the mechanical properties showed a tendency to increase with the quenching temperature first and then decreased.When the quenching temperature of test steel A is 930℃,the comprehensive mechanical properties are the best.For the experimental steel B,when the comprehensive mechanical properties are the best,the quenching temperature is 890℃.The strength and hardness of the experimental steel A is higher than that of the experimental steel B.This is because the experimental steel A has more Mo content than the experimental steel B,and the solid solution strengthening effect of the element Mo is stronger.(3)The microstructure and mechanical properties of as-quenched martensite during the tempering process of the experimental steel were studied.After tempering,the strength and hardness of the two experimental steels A and B decreased very little.The strength and hardness of experimental steel A after low temperature tempering were 1392 MPa and 470 HV,respectively.The strength and hardness of experimental steel B after low temperature tempering were 1269 MPa and 419 HV,respectively.In addition,both A and B test steels exhibit excellent low-temperature impact toughness.The impact energy of the experimental steel A at-40℃.reaches 50 J,while that of the B test steel at-40℃.reaches as high as 190 J,far exceeding the impact toughness requirements of the national standard on the NM400.(4)The effect of high service temperature(300～500℃)on the mechanical properties of the new wear-resistant high-temperature wear-resistant steel was studied.The intrinsic change of the microstructure was analyzed.The high-temperature mechanical properties of the conventional NM400 were compared and analyzed.With the increase of temperature,the strength and hardness of the two kinds of experimental steel A and B and the comparative steel NM400 are decreased,but the two kinds of wear-resistant high-temperature wear-resistant steel designed for the slow decline rate,while the conventional wear-resistant steel NM400 The strength and hardness decrease sharply with increasing temperature.The high temperature strength of experimental steel A decreased from 1368 MPa at 300℃ to 860 MPa at 500℃;the high temperature strength of experimental steel B changed from 1345 MPa to 927 MPa;the high temperature strength of conventional wear resistant steel NM400 dropped sharply from 1310 MPa to 554 MPa.(5)The high temperature wear properties and room temperature wear properties of A and B test steels and NM400 were compared and the wear mechanism was analyzed.The results of room temperature abrasive wear show that the room temperature wear properties of NM400 and B steels with the same hardness are very different.The room temperature wear properties of A steel with relatively high hardness are best.The wear mechanism of experimental steels is mainly based on micro-cutting and plastic fatigue.The results of high temperature friction and wear experiments show that the mechanical properties of NM400 at high temperatures are greatly reduced,and high temperature wear performance is greatly reduced.The mechanical properties of A and B test steels have a small decrease in mechanical properties,and the wear profile is dominated by shallower furrows,demonstrating excellent high temperature wear resistance.Among them,test steel A has the best high temperature wear resistance.With the service temperature of 500℃,the high-temperature wear performance of test steel A was more than 2.0 times that of conventional NM400.