Artigos

Refractories are often exposed to thermal variations during their operational cycle, such as in torpedo cars and iron ladles, where molten metal is loaded and unloaded at a high frequency basis. Dealing with that aggressive thermal shock is not straightforward and the most common approach for these materials is to optimize the carbon sources, increasing the thermal conductivity of the bricks and reducing the thermal gradient between the hot and cold faces. If, on one hand, the material becomes more resistant to thermal shock damages, on the other hand, its higher conductivity imposes a negative consequence: higher thermal loss during operation. In this work, inspired by intelligent microstructures with the ability to adapt to the most severe environmental conditions, an innovative approach was evaluated, aiming at obtaining an Al2O3- SiC-C brick formulation designed to present a self-healing behavior, without variation in the carbon sources or content. The new developed structure successfully regenerated the cracks initiated during thermal cycles, resulting in an even tougher material after thermal shock tests. Other properties such as mechanical, oxidation, and corrosion resistance also showed promising results, pointing out the birth of a smart self-healing technology, able to completely change the role of refractories in thermal cyclic operations.

The constant increase in demand has imposed to the steel industry an intense search for high productivity. Following this trend, the use of monolithic refractories is growing significantly, allowing shorter installation times and consequently greater availability of equipment. The main disadvantage of this class of material is the need for long drying times during its application. In this work, an entirely novel binder system for monolithic refractories is proposed, aiming at the reduction and potential elimination of the drying step during trough and runners repairs. For this purpose, this binder system was evaluated in an Al2O3-SiC-C castable and compared with the two most used commercial binders: calcium aluminate cement and colloidal silica. The results showed that this system successfully produced a permeable gel-like microstructure, which led to an excellent drying behavior, even in the most aggressive heating conditions, without damaging the product’s mechanical, oxidation and corrosion resistance. In the field, runners have already operated successfully using the new binder without any drying step, maintaining their performance with the benefit of a drastic reduction in repair time. Such positive results highlighted that the use of such exclusive binder could lead to the avoidance of up to 500 tons