The Research Of The Combination Properties Of AAR-D Heavy Haul Wheel Steel

Such usage conditions as heavy haul of railroad vehicles have become severe in recentyears, more requirements on the quality and performance of wheel steels have been desired. Atpresent, China’s heavy haul wheels compared with foreign products, there are still a certain gap,especially on the combination property. The intensity、hardness and abrasive resistance of theChina heavy haul wheel can not fully meet the standard requirements. Therefore, in order tomeet the needs of the development of China’s heavy haul train, the factors affecting thecombination of wheel steel must be researched, to improve hardenability、mechanical propertyand abrasive resistance of our heavy haul wheel steels.According the problem of all round property of heavy haul wheel, we choose6AAR teststeels which is from maanshan iron and steel Co.LTD.as the research object, the choice of threedifferent types of steel components. The microstructure of different chemocal compositionspecimens which have different combination property were analyzed by the means of Jominytest machine, GLEEBLE3500hot/force simulation testing machine, optical microscope,scanning electron microscope and MMS-2A Microcomputer control friction and wear testingmachine, to find out the key factors affecting combination property of heavy haul wheel steels,and then, changing heat treatment parameters to improve the microstructure of wheel steels, soas to reach the purpose of improving combination property of wheel steel. In this paper, thestudying results indicate:(1) The small quantity of Cr element addition can significantly improve the steelhardenability, reduce the lamellar spacing of pearlite, refine grain, improve strength andhardness of the heavy haul wheel steel, and accordingly improve wear and shelling-resistance ofwheel steel. But when Chrome element mixed in high carbon heavy wheel steel, continuouscooling transformation stability is reduced, cooling rate significantly influenced the organization,thereby the steel cooling rate after rolling is required higher.(2) Carbon content of the heavy haul wheel steel should be0.70%. Excessive amounts ofCr is not conducive to improve the combination properties of the heavy haul wheel steel, so thecontent of Cr element must be strictly controlled.(3) The total of the alloy elements (Si, Cr, Mn) addition can significantly improvehardenability of heavy haul wheel steel;Cr and Mn added consolidated is more effective than asingle element effects. (4) From820to860°C, with the ferrite along the grain boundary changing more uniformdistribution and the volume fraction ferrite becoming higher, the same chemical compositionheavy haul wheel test steel is haven smaller grains and higher strength and ductility. When theheat treatment temperature is at840℃, the test steel is haven smallest grains and higheststrength and ductility.(5) Tempering process as a final heat treatment process can make the wheel steel reducefriction coefficient in some process of friction and wear, improve wear and shelling-resistanceof wheel steel.With actual production desingning the pretreatment and final treatment process forindustrial trial, in order to obtain good combination properties of heavy duty wheel steel, it isvery necessary to add a certain (0.24%) amount of chromium element and use heat treatment840℃×1.5h+cooling in sand+500℃×4h.