The measurement principle of the temperature of the billet induction heating furnace

Billet temperature measurement: During the heating process, the surface temperature of the billet is measured through a coil hole on the side. The optical temperature measuring head faces the surface of the billet through this hole. The measurement of optical temperature depends on the surface of the billet and its emissivity. For each material that needs to be heated, a potentiometer connected to the measuring head is adjusted by multiple tests and comparative measurements. The purpose is to find the deviation between the actual temperature and the indicated measurement value. Because the measurement of optical temperature depends on the surface of the billet, and the longer the billet stays at high temperature will produce oxide scale on the surface, which will form bubbles after a long time and finally fall off. The temperature of this layer of bubbles is lower than the temperature of the billet, causing errors in the measured temperature.

For this reason, nitrogen is blown into the holes on the coil to prevent the oxygen in the surrounding air from impacting the surface of the billet in the area of ​​the measuring point. The nitrogen consumption is about 20L/h for the billet provided by the “slab induction heating furnace”. The surface of the billet is moving towards The punching machine and in the process of punching, and then in the process of transporting out from the punching machine. Will be exposed to the surrounding atmosphere. Therefore, a layer of oxide scale has been produced on the surface of the billet. In order to remove the oxide scale, a compressed air nozzle is installed under the “steel billet induction heating furnace”. When charging, the nozzle blows the compressed air onto the surface of the billet to remove the loose oxide scale on the billet temperature measurement position and compress it. The air requirement is about 45m3/h, the optical temperature measuring head, the measured temperature is recorded by the temperature recorder. When the heating temperature exceeds the specified maximum temperature, the power supply of the inductor is disconnected to ensure that the billet does not overheat; when the temperature of the billet is lower than the specified temperature, the power supply of the inductor is automatically turned on. The operation of the “heating” furnace: For magnetic steel billets that are prone to cracks, when heated at a temperature below the Curie point, the heating speed is very fast. In order to prevent cracks in the billet, only low power can be used for operation. When the heating temperature exceeds the Curie point temperature, the power of the inductor decreases, and the heating speed of the billet is very slow. The voltage on the inductor must be increased to heat the billet to the required extrusion temperature with high power.