Main varieties of magnesite refractory bricks

Main varieties of magnesite refractory bricks

Refractories with magnesium oxide as the main component and periclase as the main crystal phase are collectively referred to as magnesia refractories. At present, the main varieties of refractories are as follows.

1. Ordinary magnesite refractory bricks: It is made of sintered magnesia stone and is made by sintering. It contains about 91% of MgO. It is a magnesia refractory product directly combined with silicate. This is a magnesium product that is widely produced and used.

2. Directly combined magnesite refractory bricks: It is made of high-purity sintered magnesia by sintering. Containing more than 95% MgO, it is a magnesia refractory product directly bonded between periclase grains.

3. Magnesia-silica brick: It is made of high-silicon sintered magnesia stone and is made by sintering. It contains SiO2 5%~11%, and the molar ratio of CaO/SiO2 is less than or equal to 1. It is a magnesia refractory product combined with forsterite.

4. Magnesia-chrome bricks: take sintered magnesia as the main raw material, add an appropriate amount of chrome ore, and are made by sintering, containing Cr2O3 8% to 20%, and are magnesia refractory products combined with magnesia-chromium spinel.

5. Forsterite brick: Forsterite refractory is a refractory with forsterite as the main crystal phase. It is mostly made of peridotite and pure peridotite as the main raw material. The formed products are called forsterite bricks.

6. Magnesia-alumina bricks: take sintered magnesia as the main raw material, and add an appropriate amount of materials rich in Al2O3, and are made by sintering, containing 5% to 10% of Al2O3, and are magnesia refractory products combined with magnesia-alumina spinel.

7. Magnesia-calcium brick: It is made of high-calcium sintered magnesia stone and is made by sintering. It contains CaO 6%~10%, and the CaO/SiO2 molar ratio is greater than or equal to 2. It is a magnesia refractory product combined with dicalcium silicate.

Magnesium-containing refractory products are divided into direct bonding products, general sintered products and non-sintered products. The refractory material is added with chemical binder to make a certain shape, and the product made without firing is called unfired product. This is a unique manufacturing method for magnesium-containing refractories. The properties of fired products and unfired products are different. Fired magnesia bricks are generally fully sintered at 1500~1700 ℃, and the crystals in the composition are sintered together to form a whole. During the heating process, the strength does not decrease much, but above 1300 ℃, due to the liquefaction of the secondary crystal phase, the strength gradually decreases. Unfired products rely on magnesia or calcareous cement hydration to maintain strength. The hydration structure is destroyed after being heated, the binding force disappears around 400℃, and the strength drops sharply. The temperature continues to rise and the strength cannot be recovered. In special cases, it will drop below 49MPa. As shown in Figure 1. Therefore, unburned products cannot withstand large loads.