Furnace materials are mainly refractory bricks, heavy fireclay castables, or high-alumina castables. Due to the large material capacity, large heat capacity, and large thermal conductivity, the heat storage and heat dissipation losses of the furnace body are relatively serious. Moreover, due to the large heat capacity of the material, it takes a long time for the oven and the shutdown to cool down, which limits the energy-saving and efficient operation of the heating furnace. In order to save energy and improve operating efficiency, the use of lightweight castables with light bulk density, low heat capacity, and low thermal conductivity is an effective method. However, most lightweight castables at present are difficult to meet the requirements of high temperature and flame erosion in the heating furnace due to the low use temperature. Lightweight composite furnace lining is used, that is, the heavy castable (contact fire filling) in the inner layer is covered with lightweight castable (heat preservation and energy saving). The construction process is complicated and the effect is not ideal. Due to the different expansion coefficients of lightweight castables, they will also cause greater shear stress to the hanging bricks and increase the risk of furnace roof collapse. This has been confirmed in practice.
Lightweight Mullite Refractory Castable and Its Application Advantages
The key raw material of lightweight castables is lightweight refractory aggregates that can make the bulk density of the castables lighter. Lightweight aggregates generally account for 50% to 70% of the total pouring, and the volume ratio can reach more than 90%. Therefore, the performance of castables also mainly depends on the performance of lightweight aggregates. In the past, the reason why the use temperature of lightweight castables was low was that the use temperature of its aggregates was low.
In order to use castables with a long-term use temperature of 1400 to 1500°C, lightweight mullite aggregates have been successfully used. Mullite is a refractory mineral with good mechanics and high-temperature properties. Its melting point can reach 1910°C, with high hardness and low creep. Refractory products with mullite as the main mineral phase have higher fire resistance.
Lightweight mullite refractory castables are prepared by using lightweight mullite aggregates. This castable has refractoriness of more than 1710°C, has the characteristics of small bulk density and high temperature, and can be used for a long time at an ambient temperature of 1500°C.
For example, the heating furnace in the 500 steel rolling workshop of a steelmaking plant is used to heat 325kg of steel ingots. The heating conditions are harsh, and the maximum temperature of the furnace is 1450°C. Adopt liquid slagging. The original furnace roof is made of high-aluminum castables, and the spalling is more serious in the high-temperature section, and the service life is less than one year. At the same time, due to the high thermal conductivity of high-aluminum castables, the heat dissipation of the furnace body is greater. In April 1992, the heating furnace used lightweight mullite refractory castables. By the time the furnace was shut down in October 1992, it had been in operation for nearly 6 months. The furnace top has no cracks, and the inner surface has no peeling, smooth as before.
The use of lightweight mullite refractory castables not only improves the life of the furnace top and reduces heat loss, but also because of the high porosity of the lightweight materials, the baking is simple, which can achieve rapid baking, rapid heating, and save maintenance time. This is unmatched by heavy castables. At the same time, because the flexible castable has good resistance to rapid cold and rapid heat, its peeling resistance is also much better than that of heavy castables.
When the 500 billet heating furnace was repaired and shut down, the inner surface of the furnace roof was only slightly peeled off after one year, and the furnace roof was still in good condition.
The successful application of the lightweight mullite castable in the 500 billet heating furnace has established a model for other heating furnaces, and the castable has been quickly promoted in other heating furnaces.
Why Choose Lightweight Mullite Refractory Castable?
(1) Lightweight mullite castable is a high-temperature, lightweight castable with light bulk density, low thermal conductivity, and high operating temperature. It can be used for a long time under high temperature and direct flame environment, and it is extremely suitable for steel rolling heating furnace as furnace wall and furnace roof material.
(2) Because the lightweight castable has high porosity and small heat capacity, it can achieve rapid baking, rapid heating, and cooling. Save maintenance time and improve productivity.
(3) The application of light-weight mullite refractory castable has an obvious effect on heat preservation and energy saving.
(4) The castable has good resistance to rapid cold and heat and peeling resistance.
(5) After using the castable, the original light and heavy composite structures are canceled. On the one hand, it eliminates the shear stress caused by the different expansion coefficients of the light and heavy castables on the hanging bricks. On the other hand, it also reduces the load of hanging bricks and steel structures, greatly increasing the safety factor of the furnace roof and furnace wall.
Rongsheng Refractory Manufacturer
Rongsheng is a refractory manufacturer with rich experience in refractory production and sales. Its refractory materials have been sold to more than 60 countries around the world. For example, Russia, South Africa, Kazakhstan, Philippines, Chile, Malaysia, Uzbekistan, Indonesia, Vietnam, Kuwait, Turkey, Zambia, Peru, Mexico, Qatar, etc. And received unanimous praise from customers. High customer return rate. Moreover, Rongsheng‘s newly established advanced environment-friendly and fully automatic unshaped refractory production line have an annual output of 80,000 tons. It provides a reliable guarantee for the normal operation of the refractory lining of various thermal furnace equipment. Our high-quality lightweight mullite refractory castables can also provide better insulation for the lining of your kiln equipment so that your equipment can achieve the best energy-saving state during normal operation and save production costs.
