Let you know about the intermediate frequency heating furnace for billet heat treatment

Induction heating is increasingly used in hot deformation processing in the metallurgical industry and machinery manufacturing industry. Non-ferrous metals such as aluminum alloys, magnesium alloys and copper alloys are widely used in induction heating before rolling and extrusion. Today, the editor will briefly talk about the intermediate frequency heating furnace used for induction heating of steel billets.

(1) Purpose of billet intermediate frequency heating furnace: used to heat carbon steel, alloy steel, ball bearing steel including ferritic steel and austenitic steel to the maximum extrusion temperature of 1250°C. After the steel billet is heated to 1250°C in the "heating" furnace, it is pierced on the piercing machine. Due to the decrease in temperature of the steel billet, it must be heated in the "reheating" furnace and then extruded.

The intermediate frequency heating furnace can handle four different diameters of steel billets. Changing from one diameter of steel billet to another requires some adjustments to the furnace and the replacement of the sensor.

(2) Structure of the intermediate frequency heating furnace: The induction heating furnace is vertical and hydraulically driven for easy automatic control.

The coil of the inductor is made of special-shaped pure copper tubes, arranged in a single layer, cooled by water, and has a magnetic conductor. There is an open tube of high-temperature resistant material in the coil, and there is a protection between the coil and the heat-resistant tube. cylinder.

(3) Compensation of billet end temperature: The billet is fixedly heated in the inductor, and due to the end effect, the temperature at both ends of the billet is lower. In order to enhance the power at both ends of the coil, an adjustable single-phase dry-type transformer and a variable capacitor bank are connected to both ends of the coil.

(4) Pressure and temperature control of coil cooling water: In order to ensure the normal operation of the sensor, water is passed through the coil for cooling. The water pressure is about 3×105Pa. The inlet water temperature does not exceed 35°C. However, to avoid condensation, the inlet water temperature does not exceed It should be lower than the surrounding temperature, and the outlet water temperature should not exceed 65℃.

A pressure gauge is installed on the water inlet side of the coil and for some reason the fixed water pressure is reduced, which will cause the power to the inductor to be interrupted through a contact on the pressure gauge.

There is a temperature monitor on each water path of the coil. If the amount of water provided is not enough and the water temperature rises to the specified 65°C, the power supply will be cut off through the fault alarm device.

(5) Measurement of billet temperature: During the heating process, the surface temperature of the billet is measured through a side coil hole. The optical temperature measuring head passes through this hole and faces the surface of the steel billet.

The measurement of optical temperature depends on the surface of the billet and its emissivity. A potentiometer is connected to the measuring head. For each material to be heated, its adjustment is determined by numerous trials and comparative measurements in order to find out the deviation of the actual temperature from the indicated measured value.

Since the measurement of optical temperature depends on the surface of the steel billet, if the steel billet stays at high temperature for a long time, oxide scale will be generated on the surface. Over time, bubbles will form and eventually fall off. The temperature of this layer of bubbles is lower than the temperature of the steel billet, causing errors in the measured temperature. To this end, nitrogen gas is blown into the hole on the coil to prevent oxygen in the surrounding air from impacting the surface of the steel billet in the measurement point area. The consumption of nitrogen gas is about 20L/h.

The temperature measured by the optical temperature measuring head is recorded by the temperature recorder. When the heating temperature exceeds the specified maximum temperature, the power supply of the sensor is cut off to ensure that the billet will not be overheated; when the temperature of the steel billet is lower than the specified temperature, the power supply of the sensor is automatically turned on.