Rails are the main component of railway tracks. Their function is to guide the wheels of rolling stock forward, bear the huge pressure of the wheels, and transmit it to the sleepers. During the work process, the rails will inevitably bear huge friction. Therefore, it is very necessary to use a medium frequency induction heating machine for quenching heat treatment.
There are two types of intermediate frequency induction quenching inductors: pointed rail and continuous. The working principles of the two are the same. The intermediate frequency continuous quenching inductor includes the functions of the pointed rail inductor, so it is more widely used.
The pointed rail mid-frequency inductor is a continuous saddle-shaped inductor with low temperature difference, which uses 1000-2500Hz mid-frequency current. Its characteristic is that the temperature difference between the rail angle and the tread is very small. By increasing the gap at the rounded corner, the ring effect and sharp corner effect are reduced. The gap is 10-12mm, and the gap between the rail angle and the tread is 2mm, so that the gap between the two places is 10-12mm. The temperature difference is reduced to 20-30°C, and the quenching method of continuous spray (mixed gas of water and oil) or air jet cooling is used. The intermediate frequency quenching uses a 120kw, 1000Hz intermediate frequency heating furnace. The moving speed of the continuous quenching of the rail is 292-350mm/min. The hardness and quenching layer depth at 9mm after quenching meet the requirements.
The medium-frequency continuous quenching inductor can be used to quench the entire length of the rail, and is also suitable for quenching the point rail and rail end. The quenching layer is hat-shaped. The moving speed of rail medium frequency induction quenching should be determined according to the specific dimensions, requirements, etc. The cooling medium after medium frequency induction heating can be selected according to the material composition and technical requirements. There are spray, air spray and air first and then water processes. They Have different cooling properties, so they should be applied differently.
The heat treatment process of the rail is: medium frequency preheating - medium frequency heating - cooling (when the surface temperature is below 750°C, compressed air cooling is carried out) - 500°C natural aging or tempering. If air is used first and then water is used, the quenching speed is fast, the production efficiency is high, the process is stable, the distortion is small, and the cost is low, so it is widely used.
The preheating temperature of the rail is 550-650℃, the temperature of the rail waist and rail bottom is in the range of 400-500℃; the heating temperature on the rail tread should be 900-920℃, and the temperature on both sides and fillets should be 1000-1020℃ ℃; wind pressure is 0.125-0.130MPa, water volume is 280-450L/h, cooling water temperature is less than 40℃; the distance between the sensor and the tread is 5-8mm.
Many manufacturers use the above process to quench and heat treat the rails. The rails produced are of good quality and meet the needs of the work. For the above processes, if you have relevant needs, please feel free to leave us a message.