Refractory Materials That Can Replace Some Traditional Refractory Bricks and Refractory Castables

2023-11-01 14:54:18

Prefabricated blocks and unfired bricks are formed products in amorphous refractory materials. They are non-flammable or light-burning products with excellent performance. They are new materials that are developing rapidly and widely used.

Prefabricated blocks, also known as prefabricated components, belong to the category of amorphous refractory materials. The reason is that the raw material composition, preparation principle, binder, and additive use of non-burning bricks are the same as those of non-burning refractory materials, and they are no-burning or light-burning products. Compared with unshaped refractory materials constructed on site, this product has the advantages of accurate size, stable performance, short construction period, and low cost; compared with sintered refractory bricks, the product yield is high, no kiln is needed, energy saving, and low production cost, excellent performance. Therefore, prefabricated blocks and unfired bricks have broad development prospects.

It should be pointed out that in recent years, non-fired bricks have developed rapidly, and new varieties have emerged one after another, forming a new prosperity. The development and application of new varieties of magnesia-carbon bricks, alumina-magnesia-carbon bricks, aluminum-carbon bricks, and Al2O3-SiC-C unburned bricks have led to the replacement of furnace linings of thermal equipment such as steelmaking converters, electric furnaces, and ladles, improving their service life. Significant social and economic benefits have been achieved; at the same time, high-performance unfired bricks such as breathable bricks and seat bricks have been developed using expansion agents, ultrafine powders, additives, and particle grading technology. It has achieved good application results in electric furnaces, ladle kilns, and other equipment.

Unshaped refractory prefabricated blocks are mainly made of refractory castables and refractory plastic materials, and are divided into castable prefabricated blocks and plastic prefabricated blocks; prefabricated blocks use binders such as aluminate cement, sodium silicate, phosphoric acid, and aluminum phosphate, Clay is bonded to form cement; according to the type of aggregate, it can be divided into high alumina, clay, silicon, and corundum; according to the molding method, it can be divided into vibration molding, vibration pressure molding, and tamping molding prefabricated blocks; the mass of the prefabricated blocks ranges from tens of kilograms to Between several tons, they are divided into large, medium and small prefabricated blocks; prefabricated blocks with steel bars and anchors are also divided into ordinary prefabricated blocks, steel prefabricated blocks and anchored prefabricated blocks.

In industrial kilns and thermal equipment, prefabricated block furnace bodies can achieve mechanized hoisting, saving manpower and labor, shortening the construction period, and improving the furnace operation rate.

Blast furnaces, hot blast furnaces, heating furnaces, electric furnace tops, iron ore powder roasting shaft furnaces, pellet roasting furnaces, etc. have a history of using prefabricated blocks to build hot kilns. They are still widely used in tapping tanks, electric furnace tops, and roasting furnaces, and played a greater role.

In recent years, the tapholes and slag tubes of small and medium-sized blast furnaces have been constructed with alumina-silicon carbide refractory castables, which have achieved good results. Prefabricated blocks are produced in the factory and are processed at low temperatures before leaving the factory. Therefore, the furnace lining does not need to be baked and has a long service life, which is an important development direction in the future.

It should be noted that all refractory castables and refractory plastic materials can be used as prefabricated blocks. Since production conditions are better than on-site construction conditions, performance has also improved.

The results show that the aggregates of CA-50 cement and phosphate clay castables are respectively 70% clay clinker particles smaller than 10mm, 15% and 30% high aluminum powder smaller than 0.09mm, and 15% and 2.5% CA- 50 cement. The former is mixed with water water-reducing agent and the water consumption is 10%. The latter uses 42.5% phosphoric acid as the binder and the dosage is 13%; the results show that the aggregate and powder of the water glass-aluminum-magnesium castable prefabricated block are first-grade bauxite clinker, and the aggregate is less than 5mm The content is 60%, the powder is 30% and 26% respectively, the magnesia powder for brick making is 10%, the modulus is 2.8, the water glass dosage with a density of 1.32g/cm3 is 9%, and its performance is good. Add 4% flake graphite; low cement and ultra-low cement high aluminum castable prefabricated parts. The shapes of prefabricated blocks mainly include square, long strip, arch, ring, etc., and they are special-shaped products.

The partitions and sizes of prefabricated blocks should be determined according to the size of the furnace body and the thickness of the lining. Minimize the model and save templates to facilitate management and construction. The unit weight of prefabricated blocks for furnace construction is 1~3T, and the unit weight is for manual handling and furnace construction. The prefabricated block should not be larger than 30kg. The size, length, and thickness direction of the prefabricated block should be 116mm and 68mm respectively as the module, and the appropriate multiple should be selected to subtract the joint size. The width of the furnace top prefabricated block depends on the length of the furnace and must not be less than 300mm. The height of the furnace wall prefabricated blocks shall not be less than 400mm. The joint width of two prefabricated blocks is 3~8mm.

When there are holes in the prefabricated blocks, the tire mold should have a slope of 1% to 2%, and it should be easy to dismantle; large prefabricated blocks should be equipped with lifting rings, and the top of the lifting rings should be away from the heating surface. The spacing should be greater than 200mm, and the burial depth should be 100 to 100mm. 200mm. As the weight of a single prefabricated block increases, the diameter of the lifting ring steel bars also increases.

When the steel bars are installed on large prefabricated blocks, they should be kept as far away from the heating surface as possible and made into a convex shape. Reinforcement bars are generally No. 3 steel, and aluminized steel bars should be used. At the same time, the steel bars must not be wrapped or oiled so that they can work tightly with the material. The structure is characterized by stirrups inserted into the rib beams, which can withstand shear stress caused by temperature changes and have a long service life. The distance between the lower end of the stirrups and the working surface should be greater than 160~260mm, and the specific size depends on the operating temperature in the furnace.

After the prefabricated blocks are formed, their maintenance system is the same as that of castables and plastic materials of the same material; when stacked, the prefabricated blocks should be padded with wooden strips, the lifting rings upward, and the signs should face outwards; when the prefabricated blocks are hoisted and constructed, there should be gaps left with the same material. Refractory slurry leveling fill. If the gap is too large, it should be leveled with the same material and compacted with tapping.

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