Induction Furnace Refractory Lining Materials

Induction Furnace Refractory Lining Materials

Refractory Materials for Induction Furnace Should Meet the Conditions

Requirements that Refractory Materials Should Meet

Furnace lining refractory materials, no matter whether they are used for heart induction furnaces or centerless induction furnaces, should meet the following requirements.

(1) have the good chemical stability

Metal aluminum and aluminum alloys not only have high chemical activity but also have excellent fluidity of the melt. The viscosity of molten aluminum at 750°C is only 1.04 centipoise, which is quite close to the viscosity of water at 20°C (1.0 centipoise), which is the main reason why it easily penetrates into the furnace lining and undergoes chemical reactions.

At the temperature where the liquid aluminum is in contact with the refractory material, aluminum acts as a strong reducing agent. SiO2, TiO2, FeO, and other oxides in refractory materials should be reduced by aluminum.

The reaction between the molten aluminum and the lining refractory material not only affects the quality of the product, but also causes nodules, bulges, and sedimentation on the surface of the lining. There is a risk of cracks at the interface between the part impregnated by the molten aluminum and the original refractory brick, and the furnace is shut down. It can also cause peeling.

Therefore, the furnace lining material in contact with molten aluminum must have high chemical stability and as little impregnation as possible.

(2) have good erosion resistance

Generally, in order to make the furnace have higher electrical efficiency, the furnace wall material is designed to be very thin, but during the operation of the furnace, due to the action of electromagnetic force, the molten metal in the furnace is constantly churning and stirring, and the furnace lining is continuously washed and worn. 

For the heart induction furnace, due to the use of the jet-type melting channel, the erosion and wear of the refractory material of the melting channel are more serious.

Therefore, the refractory materials used must have high mechanical strength and hardness.

(3) High density and volume stability

As a refractory material for melting furnaces, it is hoped to obtain higher density and volume stability under the condition of certain materials.

The density of the body reflects the number of pores inside the molded body, especially the degree of sintering.

The higher the volume stability of the material, the smaller the possibility of cracks during sintering and use, the smaller the width of the cracks, and the stronger the penetration resistance.

(4) It is not easy to produce furnace tumor

There is little possibility of the formation of furnace nodules due to impurities (such as Al2O3) present on the surface or in the melt. Because the furnace tumor will significantly reduce the capacity of the furnace, and the metal tumor itself is dense and tough, so it is very difficult to remove.

(5) Not easy to be wetted and penetrated by molten metal

As we all know, refractory materials are brittle materials, and cracks will inevitably occur during heating and cooling.

But one of the key factors determining its life is the size of the crack and the speed at which it propagates.

The crack growth is related to the wetting and penetration ability of the molten metal to the contacting material.

The worse the wetting ability, the more favorable it is.

(6) Good resistance to rapid cooling and rapid heating

This is especially important for centerless induction furnaces. Because the operation mode of the centerless furnace is a continuous cycle of "feeding-melting-out of the furnace", the lining material is repeatedly subjected to thermal shock.

If the thermal shock stability of the refractory material is not good, cracks and crack extensions will easily occur, and the molten metal will penetrate into the coil in a short period of time, resulting in the scrapping of the entire furnace lining.