The industrial frequency induction furnace is an induction furnace that uses industrial frequency current (50 or 60 Hz) as a power source. The industrial frequency induction furnace has developed into a widely used smelting equipment. It is mainly used as a melting furnace to smelt gray cast iron, malleable cast iron, ductile cast iron and alloy cast iron. In addition, it is also used as a holding furnace. As before, the industrial frequency induction furnace has replaced the cupola furnace as the main equipment in casting production. Compared with the cupola furnace, the industrial frequency induction furnace has many advantages such as easy control of molten iron composition and temperature, low gas and inclusions in the casting, no pollution to the environment, energy saving and improved working conditions. Therefore, the industrial frequency induction furnace has developed rapidly in recent years.
The complete set of industrial frequency induction furnace equipment includes four parts.
1. Furnace body
The furnace body of the industrial frequency induction furnace for smelting cast iron consists of an induction furnace (two, one for smelting and the other for standby), a furnace cover, a furnace frame, a tilting cylinder, and a furnace cover moving opening and closing device.
2. Electrical part
The electrical part consists of power transformer, main contactor, balancing reactor, balancing capacitor, compensation capacitor and electrical control console.
3. Water cooling system
The cooling water system includes capacitor cooling, inductor cooling and soft cable cooling. The cooling water system consists of water pump and circulating water pool or cooling tower and pipeline valves.
4. Hydraulic system
The hydraulic system includes oil tank, oil pump, oil pump motor, hydraulic system pipeline and valve and hydraulic operation table.
Medium frequency
The induction furnace with power supply frequency in the range of 150-10000 Hz is called medium frequency induction furnace, and its main frequency is in the range of 150-2500 Hz. The power supply frequency of domestic low-frequency induction furnace is 150, 1000 and 2500 Hz.
Medium frequency induction furnace is a special smelting equipment suitable for smelting high-quality steel and alloys. Compared with the standard induction furnace, it has the following advantages:
(1) Fast melting speed and high production efficiency. The power density of the medium frequency induction furnace is large, and the power configuration per ton of molten steel is about 20-30% greater than that of the industrial frequency induction furnace. Therefore, under the same conditions, the medium frequency induction furnace has a fast melting speed and high production efficiency.
(2) Strong adaptability and flexible use. The molten steel of each furnace of the medium frequency induction furnace can be completely discharged, which is convenient for changing steel types; while the molten steel of each furnace of the industrial frequency induction furnace is not allowed to be completely discharged, and a part of the molten steel must be reserved for the next furnace start-up, so it is inconvenient to change the steel type, and it is only suitable for smelting a single type of steel.
(3) The electromagnetic stirring effect is better. Since the electromagnetic force on the molten steel is inversely proportional to the square root of the power frequency, the stirring force of the medium frequency power supply is smaller than that of the industrial frequency power supply. For removing impurities in steel and uniform chemical composition and uniform temperature, the stirring effect of the medium frequency power supply is better. The excessive stirring force of the industrial frequency power supply increases the scouring force of the molten steel on the furnace lining, which not only reduces the refining effect but also reduces the life of the crucible.
(4) Convenient starting operation. Since the skin effect of medium frequency current is much greater than that of industrial frequency current, there is no special requirement for the charge when starting the medium frequency induction furnace. It can be heated up quickly after loading. However, the industrial frequency induction furnace requires a specially made opening charge block (a cast steel or cast iron block with a size similar to the crucible and about half the height of the crucible) to start heating, and the heating speed is very slow. Therefore, medium frequency induction furnaces are mostly used under the conditions of cyclic operation. Another advantage brought by the convenient start is that electricity can be saved during cyclic operation.
The medium frequency furnace heating device has the advantages of small size, light weight, high efficiency, excellent thermal processing quality and favorable environment. It is rapidly replacing coal-fired furnaces, gas furnaces, oil furnaces and ordinary resistance furnaces, and is a new generation of metal heating equipment.
Due to the above advantages, medium frequency induction furnaces have been widely used in the production of steel and alloys in recent years, and have also been rapidly developed in cast iron production, especially in casting workshops with cyclic operations.