What are the characteristics of refractory materials used in induction melting aluminum furnaces
What are the characteristics of refractory materials used in induction melting aluminum furnaces? Below is a detailed introduction by the editor of Chongde Refractory:
Working characteristics of a power frequency cored induction furnace
The heat source of the intentional induction furnace comes from a groove type inductor located in the lower part of the furnace body. The aluminum liquid is induced and heated in the melting groove, and then exchanges heat with the aluminum liquid in the furnace through circulation or unidirectional flow. The large tonnage intentional induction aluminum melting furnace adopts a jet type inductor developed by Ajax Company in the United States. This type of sensor not only greatly reduces the temperature difference between the metal liquid in the melt groove and the metal liquid in the furnace, but also prevents the accumulation of chemical reaction products on the melt groove wall, which to some extent changes the blockage of the melt groove. However, due to the increase in electric power, the flow speed of aluminum liquid increases, and the complexity of the shape of the melt groove increases, which increases the wear and structural stress of the lining refractory material; The thinning of the molten groove wall and the setting of the water-cooled jacket increase the thermal stress borne by the refractory material.
The low energy consumption of the intentional induction furnace lies in its continuous operation mode, which undoubtedly increases the time and opportunity for the reaction between the refractory material and the molten liquid in the molten channel, while the possibility of channel blockage always exists.
2. Working Characteristics of Heartless Induction Furnace
The commonly used heartless induction furnaces are divided into two types: power frequency and intermediate frequency. From the current development trend, intermediate frequency furnaces have more prospects. The commonality between the two lies in the ability to operate intermittently or continuously as needed. The furnace lining is subjected to significant thermal stress due to the repeated process of "feeding melting discharging". The metal liquid in the industrial frequency furnace is more turbulent than that in the intermediate frequency furnace, which means the furnace lining is severely eroded. However, the intermediate frequency furnace has a higher specific power (twice the power of the industrial frequency furnace), higher power density, faster melting speed, and faster cold and hot alternation. Due to the high inter turn voltage (about 2-4 times that of a power frequency furnace), the possibility of overheating of the metal liquid penetrating into the furnace lining through cracks and causing coil damage is relatively high.
3. Requirements that refractory materials should meet
The refractory material for furnace lining, whether used in a cored induction furnace or a coreless induction furnace, should meet the following requirements.
(1) Has good chemical stability
Metal aluminum and aluminum alloys not only have high chemical activity, but also have excellent fluidity of their melt. The viscosity of aluminum melt at 750 ℃ is only 1.04 centipoise, which is quite close to the viscosity of water at 20 ℃ (1.0 centipoise). This is the main reason why it is easy to penetrate and undergo chemical reactions inside the furnace lining. At the temperature at which aluminum liquid comes into contact with refractory materials, aluminum acts as a strong reducing agent. Oxides such as SiO2, TiO2, and FeO in refractory materials need to be reduced by aluminum. The reaction between the aluminum liquid and the refractory material of the furnace lining not only affects the quality of the product, but also causes the surface of the furnace lining to form nodules, bulges, and precipitate impurities. There is a risk of cracks appearing at the interface between the aluminum liquid impregnated part and the original brick, and it can also cause peeling during furnace shutdown. Therefore, the lining material in contact with aluminum liquid must have high chemical stability and as little impregnation as possible.
(2) Has good erosion resistance
Generally, in order to achieve high electrical efficiency in the furnace, the furnace wall materials are designed to be very thin, but the furnace is