Lab-Research On Composition, Structure And Property Of The High Alloy White Cast Iron Grinding Ball Used In Molydenum Mineral

On the basis of analyzing the the latest research of grinding ball the paper is on the advantages and research of high chromium white cast iron at present and to study the composition, the structure and the property of the grinding ball used in molybdenum mineral by means of lab research work.In the paper, firstly,a comprehensive analysis of impact exerted by various chemical upon the material of the ball will be made to determine the proper chemical composition and to produce some samples. Secondly,by testing the corresponding properties and observing the microstructure of the as-cast iron with the best comprehensive properties which include hardness, impact toughness and abrasion corrosion resistance will be ultimate constituent.Thirdly, With parameters of heat treatment processes worked out tests of quenching and tempering treatment, subcritical treatment and isothermal cooling heat treatment were carried out. Fourthly, hardness, impact toughness and abrasion corrosion resistance will be measured and changes in the microstructure will be compared and analyzed.At the same time,X ray will be employed in measuring content of retained austenite and the influence of different heat treatment processes on properties will be analyzed to build up process-structure-property relation which can provide in theory for selection of the grinding ball's material.The chemical composition selected ultimately of the high alloy white cast iron: chromium 12.0%,carbon2.6%,copper1.0%,vanadium1.0%, silicon1.0%, manganese0.7%,sulphur and phosphorus<0.05%. The research indicates that With adding the proper contents of copper and vanadium in the alloy morphology and distribution of the carbide were improved and the corrosion potential were increased by conbining copper and vanadium in the matrix which can improve hardness, impact toughness and abrasion corrosion resistance effectively. The retained austenite in the matrix can precipitate secondary carbides which is ultrastructure when alloy subjected to subcritical treatment at 585℃for 120 minutes,and transforms into polymer ofα+M7C3 type in cooling process. The quenched and tempered structure was made up of temper martensite and secondary carbide. The test result shown that these two kinds of heat treatment can increase mechanical properties of the material in various degrees but cannot improve abrasion corrosion resistance property of them under the condition of wet wear. If parameters of isothermal cooling heat treatment in salt bath stay at 930℃×100min+310℃×150min the high alloy white cast iron with the best hardness, impact toughness and abrasion corrosion resistance can be obtained.The relative abrasion corrosion resistance of the alloy is higher 14% at as-cast and 21% after the isothermal cooling than that of average high chromium casts iron (18.0% Cr)not containing copper and vanadium. With the tests result the conclusion can be safely drawn that structure and property of the high alloy white cast iron after isothermal cooling heat treatment in salt bath at 310℃can satisfy the demands of the working condition of wet wear for grinding balls used in molybdenum mineral.