Tangshan Tangbao Refractories Co., Ltd.
Address：Beijiadian Third Street, Guye District, Tangshan
The refractory castables for iron trench are compact materials. The production process requires that the castables should be dried quickly after construction 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 ferric refractory castables mixed with aluminum powder react with water and react exothermic to form Aluminium Hydroxide Gel and escape hydrogen. The reaction formulas are as follows:
When hydroxyl radicals coexist in the reaction, complex ions will be formed, which will make the product soluble and accelerate the reaction.
Al(OH)3 + OH- →〔〔Al(0H)4〕-
For the relationship between the curing time of castable and its heating and dehydration. From the figure, it can be seen that the reaction between aluminium powder and water begins about 4 hours after casting, and it is intense and exothermic at 5-6 hours, which makes the temperature of the castable reach about 70 C. At the same time, a large amount of hydrogen escaped, which accelerated the dehydration of the material, cured for 10 hours, and removed about 17% of the moisture, thus shortening the baking time. Moreover, due to the escape of hydrogen, a uniform micro-opening pore is formed inside the castable, which is conducive to the smooth discharge of water in the castable. Therefore, the iron groove castable with aluminium powder can achieve rapid baking and comparison.
The castable without aluminium powder has more pore at 100 nm and less pore at 1000-5000 nm. The former decreases remarkably while the latter increases remarkably, that is, the tiny pore increases, which is beneficial to water removal.
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) gels also plays an important role in strength. In addition, in order to improve the intermediate temperature strength of the castable, 0.7%. 1.5% of the medium temperature reinforcement was added, which nearly doubled the flexural strength of the castable. In this way, the castable can satisfy the repetitive effect of 1000 - 1500 C in the tapping trench of blast furnace, and the trench lining does not crack and peel, thus increasing its service life.
It should be pointed out that the addition of aluminium powder in AI2O3-SiC-C ultra-low cement refractory castables not only plays an explosion-proof and enhancement role, but also plays an oxidation-proof role. 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.