Selection Of Refractory Bricks For Heat Treatment Furnaces

Selection of refractory bricks for heat treatment furnaces

Raw material selection

If the temperature of the steel heat treatment furnace is less than 300 ℃, high alumina and alumina silicate refractory bricks or amorphous refractory materials can be used to build the furnace lining.

If controlled atmosphere operation is implemented in the furnace, the lining should not undergo chemical reactions with the controlled atmosphere at high temperatures. It is recommended to use anti carburizing bricks with particularly low Fe2O3 content as the lining, and the Fe2O3 content should be less than 1% at this time.
Due to the influence of the heat treatment furnace process, the lining area and volume of the heat treatment furnace are larger than those of the heating furnace at the same productivity. Therefore, the loss of heat dissipation and heat storage in the furnace lining is much greater: for example, the loss of heat dissipation in consecutive heating furnaces accounts for 3% to 5% of the total heat, and generally accounts for 20% in heat treatment furnaces; Continuous heating furnaces do not consider the loss of heat storage. Abnormal heat storage loss in the heat treatment furnace during periodic operations accounts for 30% -40% of the stored heat. Therefore, reducing the heat loss of the furnace lining in heat treatment furnaces plays a very important role in improving the thermal efficiency of the furnace.

To reduce heat storage loss while meeting the working temperature and furnace atmosphere, furnace lining materials with low bulk density and specific heat should be selected; To reduce heat loss, it is necessary to choose furnace lining materials with low thermal conductivity. For example, a 300kW electric hood furnace can save 38.3% energy by replacing lightweight clay refractory bricks (with a density of 1.3t/m3) with aluminum silicate refractory fibers.

Shape Scale

The furnace scale should strive for compactness, reducing useless space inside the furnace, in order to facilitate uniform temperature inside the furnace and improve thermal efficiency. For example, cylindrical furnaces are often used instead of square furnaces in well furnaces.

When using controlled atmosphere heat treatment, the thickness of the furnace lining should be thicker than when the furnace is filled with air. Due to the higher thermal conductivity of controlled atmosphere compared to air, if the thermal conductivity of air is 1, the NH5 decomposition gas is 5.5 and the H2 is 7. We can use the criteria of minimal heat loss, high economic benefits, and short payback period to list relevant thermal and economic functions, and use optimization methods to obtain the optimal thickness of the furnace lining.