| The frog is an important part for the train orbit, along with the development of railway transport to the heavy load and high speed, higher requirements are put forward to frog. Bainitic steel are considered to be the best alternative materials of high manganese steel because of their excellent comprehensive mechanical properties.The frog constantly suffers periodic impact from the wheel. With environmental factors, the frog easily leads to fatigue failure. Therefore, it is particularly important to improve the comprehensive properties of frog. In order to find the way to improve the performance of steel,the effects of heat treatment on the impact toughness and contact fatigue performance of Si-Mn-Cr series bainitic steels developed by Xihua University were studied in this paper.Two sets of austenitizing temperature and four groups of isothermal heat treatment temperature was designed to study the effects of technological parameters on impact toughness properties. The impact toughness value was found greatly improved after heat treatment,which was improved almost two times.With isothermal heat treatment temperature decreasing, the impact toughness of bainite steel increase first then decrease,the impact toughness was best under isothermal treatment at 330℃. At the same isothermal temperature, the impact toughness values of the samples were low when the austenitizing temperature is higher. The value of hardness was mainly between 39.0 and 46.9.The effects of the heat treatment and material smelting on rolling contact fatigue performance that were collected by the contact fatigue test machine was studied. The contact fatigue lives of the samples smelted by electroslag remelting were improved in different degrees. With the decrease of isothermal heat treatment temperature, the contact fatigue lives increased first and then decreased, the maximum contact fatigue life was 3.91×105r. The contact fatigue lives of the samples produced by non vacuum arc smelting furnace increased with the decrease of isothermal temperature,the best contact fatigue performance was2.43×105r at 330℃. The microstructure and spalling pits were studied, and with the decrease of isothermal temperature, the granular bainite, lath bainite and needle quasi bainite would be obtained. The main fatigue failure form of the bainite steel was pitting spalling and shallow spalling, the spalling pits were lenticular or approximate isosceles triangle. The same sample can also appear two kinds of spalling and the form of spalling has nothing to do with material smelting. |
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