Development of locomotive tire steel with increased strength and crack growth resistance

The paper tackles the problems of serial locomotive tires (as per GOST 398 - 210) operation under new generation freight electric locomotives 2ES10 with asynchronous traction drive, attributed to low operational resource of such tires and their insufficient reliability in terms of crack damageability. It is demonstrated that actual level of the tires’ mechanical properties and especially of strength characteristics of tire steel grade 2 as per GOST 398 - 210 is insufficient and does not comply with more tough conditions of tire loading in operation caused by the increased locomotive power rating and implementation of higher coefficient of “tire - rail” adhesion. To enhance resource and reliability of locomotive tires there were developed and tested in a laboratory environment three prototype versions of medium alloy tire steel with various content of carbon and alloying agents, improving mechanical property package up to the standards of tire operation under the new generation electric locomotives. The discussed tire steel prototypes have alloying system of Ni - Cr - Mo and differ from each other in the content of Ni (~0,5 %, ~2,0 % and ~2,3 % respectively), the main alloying agent which positive effect covers nearly all the property package of steel. By making use of special-purpose rolled specimens of steel obtained by way of laboratory melting there were conducted heat treatment modes approbation of steel prototypes and heat treatment (inclusive of heated water quenching and high-temperature tempering) of full-size tire simulant in the form of specimen with facings, creating tempered martensite microstructure with the best possible combination of strength and plastic properties all over the tire working layer It was demonstrated that in the context of obtained mechanical properties steel containing ~2 % of Ni with post-heat treatment tempered martensite microstructure, which exhibited the best test results in a part of hardness and strength (with considerable impact strength reserve) is the most prospective one.