Tangshan Tangbao Refractories Co., Ltd.
Address：Beijiadian Third Street, Guye District, Tangshan
The groove refractory castables are usually ultra-low cement refractory castables, but also low cement or no cement refractory castables. At home and abroad, there are also self-flowing refractory castables, on-site non-stirring refractory castables, refractory castables mixed with organic explosive-resistant agents and baking-free refractory castables for blast furnace tapping trench, which are characterized by convenient construction and safe baking.
Blast furnace tapping ditch is the passage through which hot metal or slag flows. Its refractory lining should have the following characteristics:
(1) Strong resistance to erosion and erosion of molten iron and slag;
(2) It has good thermal shock resistance and small volume change of reburning.
(3) Strong antioxidant capacity;
(4) Easy to construct, quick baking without bursting, easy to repair and dismantle;
(5) When used, it does not produce harmful gases, does not stick slag iron, and has long service life.
These characteristics complement each other and should be compatible with each other.
In the past, blast furnace tapping ditches in China were usually made of clay clinker, coke grains, soft clay and tar asphalt, with less iron flux, frequent repairs, high labor intensity and environmental pollution. Later, Al2O3-SiC-C ramming material was used, which resulted in a significant increase in iron flux, but a large labor intensity.
By the late 1980s, Al2O3-SiC-C ultra-low cement refractory castables were developed. Such castables are usually made of compact white corundum, sub-white corundum, brown corundum, high-quality aluminium clinker, silicon carbide and flake graphite, and then mixed with ultrafine powder, binder and additives. The middle and middle grade products are suitable for the tapping ditches of large and medium blast furnaces, while the middle and low grade products are suitable for the tapping ditches or slag ditches of medium and small blast furnaces.
Its chemical composition is basically similar, but its properties are quite different. The main material of high-grade products is fused compact white corundum, middle-grade products are fused brown corundum, and low-grade products are high-quality sintered bauxite clinker. With the increase of heating temperature, the strength of each grade products also increases, generally 1-3 times higher than its drying strength.
The refractory castable for iron trench is a compact material. The production process requires rapid drying after masonry to meet the needs of blast furnace tapping. Therefore, in refractory castables, it is necessary to mix accelerating agent or explosion-proof agent to meet the requirements of rapid lining drying. Quick-drying agents mainly include aluminium powder and aluminium lactate, explosion-proof agents mainly include polystyrene fibers and carbon fibers. At home and abroad, the most widely used metal aluminium powder. It should be pointed out that after adding quick-drying agent and explosion-proof agent to the iron trench material, it can be made into non-baking iron trench material.
The air permeability of iron ditch refractory castables with aluminium powder is tens of times higher than that without aluminium powder, which is conducive to rapid baking and drying. At the same time, the exothermic reaction between aluminium powder and water will promote the development of the coagulation of ultra-fine powder and clay, thus enhancing its strength. The generation of Al (OH) 3 gel also plays an important role in strength. In addition, in order to improve the medium temperature strength of the castable, 0.7% - 1.5% medium temperature reinforcement was added to nearly double the flexural strength. In this way, the castable can satisfy the repetitive effect of 1000 - 1500 C in the tapping ditch of blast furnace, and the ditch village does not crack and spall, thus improving its service life.
It should be pointed out that the addition of aluminium powder in Al2O3-SiC-C ultra-low cement refractory castables not only plays the role of explosion-proof and enhancement, but also plays the role of oxidation-proof. When adding aluminium powder, the variety, fineness and dosage of aluminium powder should be reasonably selected according to the specific conditions of matrix material, and the curing temperature should also be adapted. Otherwise, it will cause adverse consequences, even catastrophic accidents. For example, the amount of aluminium powder is large, the curing temperature is high, and the reaction between aluminium powder and water produces a large amount of hydrogen. When it is too late to eliminate, the lining will crack or explode and collapse.
In the 1990s, trench refractory castables have made great progress, mainly manifested in the variety of castables, which can meet the needs of modern large, medium and small blast furnaces tapping trenches; the quality has been greatly improved, especially the drying strength has been significantly improved, and other properties have also been significantly improved. The main technical measures are to adopt composite superplasticizer and superfine powder, to mix metal silicon and other additives, and to strictly control the quality and gradation of aggregate powder.
In the tapping trench of medium and small blast furnaces, the traditional trench material is commonly used for tamping, and the Al2O3-SiC-C quality tamping material is also used. The main materials of Al2O3-SiC-C ramming material are fused brown corundum and high-quality bauxite clinker. Its service life is much longer than that of traditional trench material, but its construction labor intensity is great. Therefore, refractory castables for iron trenches and slag trenches of medium and small blast furnaces are being widely promoted.