Optimization of Online Heat Treatment Process for 100 Meter U75V Steel Rail
The 100 meter U75V steel rail is the main type of rail in China's railways,and online heat treatment is the main strengthening and toughening method.The poor uniformity of longitudinal(length direction)performance and low production efficiency are the bottleneck problems in the heat treatment production.The online heat treatment process of the 100 meter U75V steel rail is divided into two cooling stages,consisting of four cooling parameters,which are the initial quenching temperature(Ti),the cooling rate in the phase transformation stage(Vs),the final cooling temperature of phase transformation(Tf)and the cooling rate after phase transformation(Va).The influence of each parameter on the microstructure and properties of 100 meter U75V steel rail is studied through thermal simulation experiments.The interlayer spacing(S)of pearlite varies within the range of 100.7 to 209.1 nm as the process parameters change.Ti and Vs have a particularly significant impact on S,while Tf and Va have no significant impact.Ti inconsist-ency is one of the main reasons for the uneven longitudinal performance of the 100 meter U75V steel rail.The two-stage cooling procedure of"slow first and fast later"is proposed,which takes the critical cooling rate of pearlite transformation before the surface temperature of the rolled steel rail cools to the final cooling temperature of phase transformation(about 500 ℃),and then increasing the cooling rate(not exceeding 10 ℃/s),which is beneficial for improving production efficiency and the uniformity of the longitudinal performance of the 100 meter U75V steel rail.
100 meter U75V railonline heat treatmentcooling parametersmicrostructureproperties
万方数据
维普
