Process analysis of rail SQ treatment using medium frequency induction heating equipment

Rail induction heating SQ treatment is carried out using medium frequency induction heating equipment. What is the heat treatment process like?

The rail induction heating SQ treatment process includes three processes: preheating, heating and cooling.

(1) Preheat the rail head. Medium-frequency induction heating equipment is used to inductively heat the rail head and preheat it to 550-600°C. The purpose is to improve the electrical efficiency during later induction heating. If the power supply power and frequency are configured appropriately, induction heating can be performed directly without preheating.

(2) The rail head is heated to the quenching temperature. The rail head is heated to 850-900°C using medium-frequency induction heating equipment with a power supply frequency of 1-6kHz, and the head metal is completely austenitized for a short period of time through heat and temperature equalization. Subsequently, rapid quenching and cooling is immediately entered.

(3) Quenching and cooling of the rail head. After the rail head reaches the austenitizing temperature, it is immediately cooled by compressed air injection or pressure spray quenching. Control the cooling rate in the high-temperature section of the C curve and maintain the cooling rate to obtain a pearlite structure with fine lamellar spacing. During the quenching cooling stage, when the head temperature drops to 450-500°C, the compressed air or pressure water mist cooling should be stopped and switched to air cooling until normal temperature.

Rail head SQ processing is a continuous operation on a dedicated production line. The process of SQ treatment focuses on three important links: rapid temperature rise by induction heating, determination of quenching temperature, and control of cooling rate.

This article briefly introduces the induction heating SQ treatment process of rails. Many manufacturers use the above process for heat treatment, and the rails produced are of good quality and meet work needs.