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Forging billet heating in induction furnace

Time:2021-02-15   Nums:3073

When the metal is heated to a certain temperature, its plasticity increases and its resistance to denaturation decreases. It is the high temperature strength curve of carbon steel containing 0.45% carbon and alloy steel containing nickel, chromium and tungsten. According to the curve, the strength of metal decreases with the increase of temperature.

Heating temperature: the forging billet is generally heated to the allowable starting forging temperature of metal. In order to ensure uniform temperature inside and outside, the forging billet surface should be kept for a certain time after being heated to the required temperature. The holding time is related to the thermal conductivity of the metal, the cross-section size of the forging billet and the placing state in the furnace. The heating rate of cold billet should not be too high to prevent excessive temperature difference between the surface and the center and large thermal stress in the center. The thermal stress in the center is easy to cause cracks. Common temperature measuring instruments include thermocouple for measuring furnace temperature and optical pyrometer for measuring metal surface temperature.

Heating method: ancient forging used open fire to heat forging billet directly. Modern forging billet heating uses a variety of coal, oil, gas and electric industrial furnaces, including intermittent chamber furnace, trolley furnace, resistance furnace, induction furnace and continuous furnace. Induction furnace has been widely used in the production line of medium and small die forgings because of its advantages of fast heating speed, uniform temperature, small occupation of land and convenient automatic control. Forging billet heating consumes a lot of energy, so it is necessary to improve the thermal efficiency of industrial furnace and improve the heating management and operation.

At high temperature, the iron in the steel and the oxidation in the furnace gas form FeO, Fe3O4, Fe2O3 and other oxides, which are called oxide scale. Oxide scale will increase metal consumption. In general, the oxidation burning rate of intermittent flame furnace is 2-3%, and that of induction heating is less than 0.5%. In addition, oxide scale will aggravate the wear of the die, reduce the forging accuracy and lead to rough surface, thus increasing the machining allowance and increasing the material consumption. Oxide scale also hinders heat conduction, prolongs heating time, affects furnace bottom life and mechanized operation of industrial furnace. In addition to oxide scale, oxidation can also reduce the surface carbon content of steel, form decarburization layer, and reduce the hardness and strength of forging surface. The formation of oxide scale is more disadvantageous to precision forging. In order to avoid or reduce various problems and losses caused by oxidation, many researches have been made on the heating of forging billet with little or no oxidation since the 20th century, and the research results have been applied to industrial production.

Yiphee Electric Furnace Co.,Ltd specializes in producing induction smelting furnace.Tel(WhatsApp):+86-13450756789, yiphee@yiphee.cn


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