Characteristics and Construction Requirements of Magnesia Carbon Bricks

Brief Introduction to the Production Process of Magnesia Carbon Bricks

Magnesia carbon bricks are a type of unburned carbon composite refractory material, made from high melting point (2800℃) alkaline oxide magnesia and high melting point carbon materials. This material is resistant to slag erosion and contains various non-oxide additives and carbon binders.

The raw material for preparing magnesia carbon bricks is electric fused magnesia with 98% MgO content. Magnesia carbon bricks have characteristics such as low porosity, resistance to slag erosion, thermal shock resistance, and high high-temperature strength. They are mainly used in alkaline oxygen furnaces, medium-grade magnesia, ladle slag lines, and electric arc furnace hot spots. Magnesia carbon bricks are a high-quality refractory material. Their main components are magnesia and carbon, with magnesia content ranging from 60-90% and carbon content from 10-40%. This material is made from high-purity magnesia particles, carbon materials, tar, pitch, or resin through high-temperature baking. These magnesia refractory bricks have properties such as slag corrosion resistance, thermal shock resistance, and thermal conductivity.

Common magnesia carbon bricks mainly contain 72% magnesia, 74% magnesia, 76% magnesia, 80% magnesia, 82% magnesia, 85% magnesia, ladle magnesia carbon bricks. The main raw materials for producing magnesia carbon bricks include electric fused magnesia, graphite, metallic aluminum powder, metallic silicon powder, and liquid phenolic resin, mixed by a sand mixer and then pressed by a press. As the graphite content increases, the strength of the bricks decreases, the thermal expansion rate decreases, and the residual expansion rate increases.

Therefore, the graphite content in the bricks should be controlled at about 20%. Magnesia carbon bricks have low slag wettability and excellent resistance to spalling and erosion, making them suitable for the slag line areas of ladles, especially in multi-furnace continuous casting situations.

Application of Magnesia Carbon Bricks in Converter Furnaces

To meet the needs of clean steel production, during ladle refining, the application area of magnesia carbon bricks has expanded from the slag line to the sidewalls. Magnesia carbon bricks are used in refining ladle slag lines and also in the linings of AC electric arc furnaces, DC electric arc furnaces, converters, and other furnaces. Below is a brief introduction to the application of magnesia carbon bricks in converters.

During the smelting process, the usage conditions and damage situations of different parts of the converter vary. To achieve balanced wear, different grades and qualities of magnesia carbon bricks are selected for different parts of the converter based on their usage conditions.

The furnace mouth and furnace hood areas experience drastic temperature changes and severe slag erosion, so magnesia carbon bricks with good thermal shock resistance and strong slag resistance should be selected. Both sides of the trunnion, besides damage during blowing, have no protective slag layer cover on the surface and are difficult to repair; carbon in the bricks is easily oxidized. High-quality magnesia carbon bricks with excellent slag resistance and oxidation resistance should be built. The slag line area is in long-term contact with molten slag and suffers severe slag erosion. Magnesia carbon bricks with excellent slag resistance are required. During oxygen blowing on the charging side, the splashing of slag and molten steel easily causes chemical erosion, wear, and scouring, as well as direct impact and erosion from charging scrap and molten iron. Magnesia carbon bricks with strong slag resistance, high high-temperature strength, and good thermal shock resistance should be selected. The furnace shell and bottom experience lighter erosion compared to other parts and can use ordinary magnesia carbon bricks. When using top-bottom combined blowing technology, especially bottom blowing with CO2, O2, and other gases, damage is more severe. High-grade magnesia carbon bricks with good oxidation resistance, thermal shock resistance, high high-temperature strength, and strong slag resistance should be selected. Selecting converter magnesia carbon bricks with corresponding performance for different parts of the converter is an effective way to improve the technical and economic indicators of the converter.

Masonry of Magnesia Carbon Bricks

(1) Brick Making and Storage

1. During the brick-making process, bricks must be prepared strictly according to standard proportions, and the quality and dimensional accuracy of the bricks must be controlled.

2. Bricks should be stacked in a dry environment or in a place cleaner, ventilated, and drier than the brick yard.

(2) Treatment of Brick Joints

1. The construction of converter masonry is a cyclic operation, and the treatment of gaps between successive masonry must be ensured to provide suitable opportunities for later brick repairs.

2. The gaps along the furnace seam direction should be kept horizontal, and a certain number of hooks or lifting plates should be added at the joints to ensure smooth jointing.

(3) Masonry Techniques

1. Masonry iron rods must be set at various corners and intersections of the wall to ensure the wall is stable and reliable.

2. Attention should be paid to the fit and gaps between bricks during masonry.

3. Under no circumstances should bricks be dropped into place by gravity during masonry.

(4) Construction Tools

1. When masonry the furnace roof part, tools that do not leak oil and safety clothing and hats must be used. Tool operators must undergo safety training and examinations and hold relevant certificates before working.

2. The toolbox must be properly installed and complete, placed in a safe area away from the site to avoid obstructing the view and causing danger.

Converter magnesia carbon bricks are important materials for internal masonry of converters. The quality of masonry directly affects the service life and production efficiency of the furnace. Therefore, during masonry, operations must be strictly carried out according to standard requirements, especially paying attention to brick joint treatment, masonry techniques, and construction tools. Only in this way can the safe operation and long-term stable production of the furnace be ensured.