Kulyk V. Substantiation of serviceability of high-strength railway wheel steels taking into account their crack growth resistance

Wheel steels and solid-rolled middle- and high-strength railway wheels. Establishment of regularities of the change of strength and fatigue crack growth resistance characteristics of wheel steels depending on the structural phase state, production technologies and influence of operating factors for the scientific substantiation of replacement of middle-strength railway wheels of in-line production for high-strength ones. Methodological basis of the work is optical and electronic microscopy, local thermo-electromotive force measuring, microfractography analysis, mechanical tests, under static loading for short-timed strength and under the cyclic loading for fatigue crack growth resistance and durability. Fatigue crack growth resistance of the wheel high-strength steel with a high content carbon (0,63 %) and microalloyed with vanadium (~0.1 %) under the cyclic loadings has been investigated for the first time. It has been established that for the service ability improvement of high-strength railway wheels this steel needs also the improvement of cyclic fracture toughness. It has been found that by strength, hardness and fatigue crack growth resistance of steel the optimum tempering temperature of high-strength wheels is 500 0C. The researches results have been used for optimization technology of high-strength railway wheels of improved life time.