Magnesia-Chrome Bricks Knowledge Guide | Click Here

Magnesia-chrome bricks are refractory products mainly composed of chromium trioxide and magnesia, with spinel and periclase as the predominant mineral phases. They feature high hot strength, excellent refractoriness and superior thermal stability, strong resistance to basic slag erosion, and moderate adaptability to acidic slags. The main raw materials for producing magnesia-chrome bricks are chromite and sintered magnesia. The magnesia raw materials shall be of the highest possible purity. The chemical composition requirements for chromite are as follows: Cr₂O₃: 30% ~ 45%, CaO: 1.0% ~ 1.5%.

Magnesia-chrome bricks are classified into ordinary magnesia-chrome bricks, semi-bonded magnesia-chrome bricks, direct-bonded magnesia-chrome bricks, fused magnesia-chrome bricks and unburned magnesia-chrome bricks, as well as fused semi-bonded magnesia-chrome bricks. The main differences between ordinary and direct-bonded magnesia-chrome bricks lie in two aspects: first, the purity of magnesia raw materials; second, the sintering temperature. The sintering temperature of ordinary magnesia-chrome bricks ranges from 1550℃ to 1600℃, while that of direct-bonded ones exceeds 1700℃. At temperatures above 1700℃, the microstructure changes, and chromite bonds directly with periclase, hence the name direct-bonded magnesia-chrome brick. It outperforms ordinary magnesia-chrome bricks in all performance indicators.

Classification Standards for Magnesia-Chrome Bricks

These standards apply to magnesia-chrome bricks manufactured from magnesia and chromite.

1. The classification of bricks shall comply with YB844-75 Classification and Definition of Refractory Products.

2. Based on physical and chemical indexes, the products are divided into four grades: MGe-20, MGe-16, MGe-12 and MGe-8.

3. The shapes and dimensions shall conform to GB2074-80 Shapes and Sizes of Magnesia-Chrome Bricks for Copper Smelting Furnaces. Custom shapes are available on request.

Magnesia-chrome bricks have obvious drawbacks: complicated production processes, high sintering temperature, large energy consumption and high production costs. Furthermore, under high temperature, alkaline environments and oxidizing atmospheres, trivalent chromium (Cr³⁺) in the bricks will be converted into hexavalent chromium (Cr⁶⁺), a highly carcinogenic substance that causes severe harm to human health and the ecological environment. For this reason, magnesia-chrome bricks are gradually being replaced by magnesia-calcium refractories, which are now widely used in AOD furnaces. Europe is rich in natural dolomite resources, so dolomite refractories are generally adopted for AOD furnace linings to replace magnesia-chrome bricks. Low-grade pitch-bonded unburned magnesia-dolomite materials are used for furnace wall linings after high-temperature firing.

Common Industrial Refractory Bricks and Mortar

Common varieties include expansion partitions, magnesia carbon bricks, magnesia-alumina carbon bricks, alumina-magnesia carbon bricks, fired magnesia bricks and magnesia-chrome bricks. Refractories are inorganic non-metallic materials with a refractoriness of no less than 1580℃. Refractoriness refers to the temperature at which a cone-shaped refractory sample resists softening and melting under high temperature without external load. Nevertheless, refractoriness alone can no longer fully define refractory materials.

Currently, materials designed for high-temperature service with comprehensive qualified physicochemical properties are collectively defined as refractories. They are widely applied in metallurgy, machinery manufacturing, silicate industry, chemical engineering, petroleum, power generation and other fields. The metallurgical industry is the largest consumer, accounting for 50% to 60% of the total output of refractories.