Modification The Resistance To Wear And RCF For Bainitic Railway By Tailoring Microstructure

The evolution of microstructure and the effect of bainitic morpholinogy on the properties of impact wear resistance of bainitic railway steel were investigated in the present work.The resistance to wear and rolling contact fatigue (RCF) of a Mn-Si-Cr seriou bainitic railway steel and conventional pearlite railway steel were studied using a RCF testing mechine and impact wear testing machine.The microstructure evolution during austempering and continous cooling as well as the relation between microstructure and properties were analyzed. And it indicated that the bainitic railway steel showed excellent bainitic hardability. Bainite/martersite multiphase microstructure can be obtained with a wide cooling rate (0.05℃/s～8℃/s). When the cooling rate is between 0.25℃/s～8℃/s, the kinetic processes of continuous cooling phase transformation are almost the same. So, it was confirmed that the scientific basis for the ability that this kind of bainitic railway can be air cooled. The effects of tempering processes on properties were analyzed. The result suggested that the tempering resistance of this kind of bainitic railway steel is very high. And the combination of strength and toughness is excellent after tempering at 280℃. Comparing with the air cooling bainitic railway steels (without tempering), the thermal and mechanical stability of retained austenite were enchanced after tempering at 280℃. Thus, the influence of tempering after air cooling was investigated which is of great importance for practical manufacture of this seriou bainitic railway. The microstructure evolution and mechanical properties were discussed of practical manufacturing bainitic railway. It indicated that the process during bainitic air cooling is relatively complex. And the properties of actual manufacturing bainitic rail are very favorable.According to CCT, TTT, and the microstructure of air cooling bainitic railway, three heat treatment processes were designed. The result suggested that the properties (such as the combination of strenghth and toughness, the resistance to wear) of acicular bainite/martensite railway steel are superior to granular bainite/martensite railway steel.In conclusion, the evlution of microstructure during austempering and continous cooling of this kind of bainitic railway steel and actual processes during manufacture were explored systematacially in this study. And based on the above results three heat treatments were designed to tailor microstructure, thus to controlling the properties of bainitic railway steels.