Medium frequency induction heating furnace: Small steel tubes are generally better treated by medium frequency induction heating furnace. The medium frequency power supply with frequency of 2500 Hz is used, and the power is selected to be 100 kW. The medium frequency inductor used is a circular spiral coil and a small steel tube is placed in the inductor.

The intermediate frequency sensor is mainly composed of an induction coil, an asbestos tube, a heat-resistant bottom plate, and copper cleats at both ends, and these parts are connected by a copper tie rod, such as a material of 50 steel, an outer diameter of ø20 mm, an inner diameter of ø7 mm, and a length of 540 mm. For example, the intermediate frequency induction coil is wound with a square pure copper tube of 8 mm×10 mm and 10 mm×12 mm, and a square pure copper tube of 8 mm×10 mm is arranged at both ends of the induction coil to strengthen the magnetic field strength and compensate the magnetic field loss. The turns of the induction coil 58 are insulated by a 1 mm thick gummy board. The heat-resistant bottom plate is made of 1Cr18Ni9Ti material to prevent the heat from becoming a loop. In the inductor, 5 small steel pipes are simultaneously heated, and each piece is loaded and discharged in 22g, the power is 60kW, and the heating temperature is 910~930°C. The productivity is 163 pieces/h, and the power consumption of a single product is 0.37 kW·h. The small steel pipe is tempered by medium frequency induction heating furnace. The medium frequency inductor used is a circular spiral tube coil. The fixture is placed in the inductor for heating for 56s, the temperature reaches 650~680 °C, and then the output is 386 pieces. /h, power 60kW, the power consumption of a single product is 0.155kW·h.