At present, in the medium frequency industry, the medium frequency smelting furnace is structurally divided into hydraulic tilting furnace with steel shell and magnetic yoke and tilting furnace with aluminum shell and reducer. Generally speaking

Steel shell furnace:

Long service life (generally the normal service life is more than 10 years);

The magnet has good stability because it has two functions: first, the magnet is firmly fixed with the induction coil with the jackscrew, so that the coil and the magnet form a stable structure. The magnetic conductor can form a magnetic barrier around the coil;

Energy saving, as the furnace with magnet can save 3% - 5% electricity than the aluminum shell furnace;

The casting point is stable, and the hydraulic furnace tilting device can well control the casting angle and speed;

Good safety performance, due to the features of furnace leakage alarm device and refractory mortar layer, the steel shell structure is selected when the tonnage is more than 2T.

Aluminum shell furnace:

The aluminum shell furnace is a simple structure, with a service life of about 5-8 years. It has no magnet, lining ejection mechanism, and refractory mortar layer. Its safety performance is poor, and it is generally used with a capacity below 2T. For example, when a 5T medium frequency furnace is full of molten iron, the overall weight of the equipment reaches 8-10T. If the aluminum shell structure is selected, when the reducer rotates the furnace body to 95 degrees, the whole furnace body will tilt forward, and the safety performance is very poor. Aluminum shell furnace is suitable for users who change production in a short time, small tonnage.

The advantages and disadvantages of steel shell furnace and aluminum shell furnace are compared as follows

Compared with aluminum shell furnace, steel shell furnace has five advantages:

1) It is sturdy, durable, beautiful and generous, especially the large capacity furnace body, which requires a strong rigid structure. From the safety point of view of tilting furnace, steel shell furnace should be used as much as possible.

2) The magnetic yoke made of silicon steel sheet shields and emits the magnetic lines of force generated by the induction coil, reduces magnetic leakage, improves thermal efficiency, increases output, and saves energy by about 5% - 8%.

3) The existence of the furnace cover reduces the heat loss and improves the safety of the equipment.

4) Long service life, aluminum is oxidized seriously at high temperature, resulting in fatigue of metal toughness. At the casting enterprise site, it is often seen that the aluminum shell furnace shell, which has been used for about one year, is in a state of dilapidation, while the service life of the steel shell furnace is much longer than that of the aluminum shell furnace due to less magnetic leakage.

5) The safety performance of the steel shell furnace is much better than that of the aluminum shell furnace. Due to high temperature and heavy pressure, the aluminum shell of the aluminum shell furnace is easy to deform and has poor safety. The steel shell furnace uses hydraulic tilting furnace, which is safe and reliable.

According to the industry custom, the aluminum alloy structure supply smelting furnace with reducer as tilting furnace is commonly called aluminum shell furnace. Induction melting furnace with steel structure using hydraulic cylinder as tilting furnace is commonly known as steel shell furnace. The difference between the two is shown in the table:

Difference between steel shell furnace and aluminum shell furnace (take 1 ton cast iron furnace as an example)