According to different raw materials, firing can be divided into natural dolomite brick and synthetic magnesia calcium brick with synthetic magnesia calcium sand as raw materials. The content of calcium oxide in synthetic magnesia calcium brick can be adjusted according to the actual needs, and a series of products with different content of calcium oxide can be produced.
The main raw materials of magnesia brick are synthetic magnesia sand, magnesia and binder, which are calcined at high temperature. In order to ensure the high temperature performance index, it is required to increase the content of MgO and CaO as far as possible, reduce the total amount of impurities A1303, SiO2 and Fe2O3, and improve the purity and calcination temperature to improve the density and fine microstructure of the synthetic sand.
(1) Preparation of raw materials
According to the actual demand of steel works, magnesia-calcium refractory containing high free CaO is needed for the production of clean steel and ultra-clean steel. Therefore, the synthetic magnesia calcium sand with 40%-60% Ca0 content should be prepared to prepare high calcium magnesia calcium brick. With the increase of Ca0 content, the production month is difficult and the yield decreases. At present, magnesia-calcium brick with CaO content of 20% or 30% is usually produced in China, which is widely used and qualified
(2) Crushing of raw materials
Generally, jaw crusher, two-roll crusher and cone crusher are used, and the particle size is in the range of 5-1 mm, 1-0 mm and 0.088 mm. In order to improve the thermal shock resistance of bricks and the defects of actual size, the critical particle size can be appropriately increased, the accumulation density of bricks can be increased, and the cold crack scrap rate can be reduced in the firing process.
Third or fourth grade ingredients can be used in production, third grade ingredients: 5-1 mm, 1-0 mm and <<0.088 mm, fourth grade ingredients: 5-3 mm, 3-1 mm, 1-0 mm and <<0.088 mm, for low calcium magnesia calcium brick, fine powder using magnesia calcium sand. Due to the large surface area and high activity of fine powder, considering hydration issues,
The binder is paraffin wax or anhydrous resin, first thickened into medium particles, and then added paraffin wax. After mixing thoroughly, add fine powder and mix for more than 20 minutes.
According to the shape of the brick, the general use of friction press or hydraulic press, raw brick density control in 2.98-3.05 g/cc. Because the product shrinks during firing, it needs to be scaled.
After firing, the surface of the brick should be waterproof treatment, usually by sealing wax, vacuum packaging and other surface modification treatment.