Research On The Preparation And Heat Treatment Process Of High Vanadium Steel

In the context of the great market demand for wear-resistant materials and the rapid development of high vanadium high speed steel,This paper mainly uses the high vanadium high speed steel with vanadium as the design concept first add elements to obtain a large number of high-quality carbide,with high carbon martensite and carbide alloy heat treatment to obtain a certain amount of reach,dispersion strengthening and solid solution strengthening idea,and to avoid carbide segregation and up to the effect of fine grain strengthening,a high vanadium high speed steel was designed and prepared by powder sintering,later,its heat treatment was also carried out.The microstructure and properties of OM were analyzed by means of metallographic microscope(SEM),X ray energy spectrum analyzer(EDS),X ray diffractometer(XRD),multifunctional surface tester and universal testing machine.The main conclusions are as follows:(1)In order to avoid the formation of net carbide easily,the carbide powder and carbon and iron powder with an average particle size of 4-7?m were selected.Using the characteristics of paraffin dissolved in hot alcohol,liquid and liquid mixing method was applied to add the forming agent,and the particle size was obtained by manual screening and granulation,and the particle size of 75-100 ?m was obtained.350MPa pressure is used to press the blank to get the blank body with the density of about 5.3854g/cm3,and the density has reached 70.64%of the theoretical density.(2)The high vanadium high speed steel billet was sintered by vacuum sintering.A sintering temperature range was obtained through calculation and analysis of DSC and phase diagram.It was proved by experiment that the liquid temperature obtained by theory is not different from the actual experimental temperature.The microstructure obtained by sintering is martensite,residual austenite and carbide(mainly vanadium carbide),Materials below 1250?also contains a certain amount of undissolved carburized carburized body;with the rising of sintering temperature,density,volume shrinkage increases,the hardness,bending strength and wear rate were increased first and then decreased.The proper sintering temperature should be about 1275?,the performance of the material at this temperature:the sintered density is up to 97.61%,the volume shrinkage rate is about 21%,the hardness is HRC62.3,flexural strength is 1100MPa,the average friction coefficient is 0.582,the wear rate is 3.97*10-5 mm3*N-1*mm-1.(3)The heat treatment of materials with more than 95%density was analyzed.According to the literature,phase diagram and DSC analysis,the process parameters were set up.The changes of microstructure and hardness of the materials were analyzed,and a general process parameter range was obtained.The results show that the volume change of materials with low density is not obvious after the quenching process;As the quenching temperature increases,the hardness increases,and tempering has two hardening phenomena;Compared with those obtained by sintering at 1275?,the same heat treatment process has better performance.(4)On a sintering temperature of the material found more detailed research on heat treatment,with the increase of quenching temperature,the grain began to grow,the hardness first increased and then decreased;with the increase of the tempering temperature,the hardness and bending strength decreased first and then increased,the wear resistance is the same trend;with the increase of tempering time,material the organization and performance did not show significant changes,but can reduce more internal stress.The best sintering and heat treatment process matching is sintering at 1275?,quenching at 1150?,temperingat 550?and tempering three times.The material properties are:hardness 67.5HRC,bending strength1598.63MPa,friction coefficient 0.487,wear rate of 5.28*10-5 mm3*N-1*mm-1.(5)The microstructure and properties of quenched and tempered high vanadium steel and M2 steel were compared and analyzed,found that the tissues were tempered martensite+residual austenite+carbide,but in contrast,the distribution of carbides in high vanadium steel is more uniform.In performance,high vanadium steel hardness is higher than that of M2 steel,but the bending strengt is lower than M2,In the wear resistance,high vanadium steel has superior wear resistance,the wear rate is only about 46.93%M2 steel;wear mechanism of high vanadium steel for oxidation wear,abrasive wear of M2 steel.