Study On Heat Treatment Process And Abrasive Wear Of Cr20 High Chromium Cast Iron

As an excellent wear-resistant material,high-chromium cast iron has been widely used in the industry,especially in the manufacture and application of cement vertical grinding roller.High-chromium cast iron grinding rolls are the main wear-resistant parts in vertical mill equipment.Their performance is one of the main factors affecting the use efficiency.In the cement production industry,a large number of grinding rolls are consumed every year,so it is of great significance to develop high chromium cast iron grinding rolls with high wear resistance.During the service of high-chromium cast iron rollers,due to its more complicated actual conditions,it is required not only to have high wear resistance,but also to have high mechanical properties to prevent the rollers from working.Deformation failure or cracking.In order to improve the performance of the high-chromium cast iron roller,this paper conducts a test study on heat treatment process and wear test.Firstly,the heat treatment process of high-chromium cast iron was tested.The influence of different heat treatment processes(different quenching temperature and cooling process and tempering temperature)on the microstructure,hardness and impact toughness of high chromium cast iron was studied to determine the best heat treatment process.After that,three-body abrasive wear was performed on the high-chromium cast iron specimens after different heat treatment.The wear patterns of the specimens after different loads and different heat treatment processes were analyzed.The wear of the matrix and carbides in the three-body abrasive wear was also discussed.The mechanism has the following conclusions:(1)The Rockwell hardness of high chromium cast iron first increases and then decreases with the increase of quenching temperature,and the impact toughness increases with the increase of quenching temperature.When the high-chromium cast iron is quenched,the micro structure mainly changes from austenite to martensite.When the quenching at a lower temperature,the carbides are not dissolved enough.When the quenching temperature is high,the content of retained austenite increases,and the quenching temperature is higher.Carbide coarsening splits the matrix.At the same quenching temperature,the samples treated with air-cooled + water mist had more martensitic transformation of the sample than the air-cooled samples.The residual austenite content was lower,and the carbides were more dispersed.(2)When the high-chromium cast iron specimen is tempered,its Rockwell hardness increases first and then decreases with the increase of tempering temperature,and the impact toughness decreases with the increase of tempering temperature.When high-chromium cast iron is tempered at lower temperature,less change in microstructure is mainly due to elimination of quenching stress;when the temperature rises,martensite matrix structure begins to decompose and soften,a small amount of carbide precipitates,and some residual austenite occurs.The secondary quenching turns into tempered martensite;at high temperature tempering,the carbides begin to aggregate and grow,and the matrix structure accelerates decomposition.(3)Under this test condition,the best heat treatment process for high chromium cast iron is 1030? ×2h(air cooling + water mist quenching)+ 450 ? ×2 h(tempering);its microstructure is martensite + carbide + small amount The retained austenite has a carbide volume fraction of 21.1%.Under the heat treatment process,the hardness is 62.0 HRC and the impact toughness is 6.45 J/cm2.(4)In the three-body abrasive wear test,the as-cast high-chromium cast iron had more scratches and furrows,and the wear loss under the 100N and 200N loads reached 0.6965g and 0.7354g,respectively,and the wear resistance was the worst.Among the three groups of specimens treated at different quenching temperatures,the scratches were the least after treatment at 1030? and the wear morphology was relatively smooth.The weight loss under the load of 100N and 200N was 0.5344g and 0.5746g,respectively,and the wear resistance was the best.(5)When the high-chromium cast iron specimen is worn out,the abrasive grain firstly cuts the matrix,which is mainly the plastic deformation and the cutting wear;the carbide is exposed and exposed under the abrasive grain cutting action,loses the support and protection,austenite and carbonization The bonding ability of the material is weak and the carbides fall off.At this time,the micro-fracture wear mechanism is mainly used.When the wear test load is small,the wear loss is also small.At this time,the main wear and plastic deformation are the main factors;when the load increases,the carbide will crack due to the abrasion of the abrasive,and some brittle fractures will cause the carbides to fall off.Cracks continue to expand,and in addition to cutting wear,it is accompanied by extensive crack growth and brittle fracture wear.