Using carbon composition in high alumina bricks for clean steel-making:
Ingot casting for producing clean steel represent only 8% of world steel production. Although a small niche, ingot casting is extremely important and the only method for producing specialized steel for crank shafts, turbines and other requirements where steel is subjected to immense mechanical stress.
Refractory products for ingot casting thus becomes a very important and the last link in production before clean steel is finally manufactured. The application requires high thermal shock and erosion resistivity of hollow-wares. It is well established that high alumina compositions work much better in such applications than high silica compositions.
There has been recent research and composition of new high alumina bricks material (83% Al2O3) composed with special synthetic aggregate and a pure matrix that increases refractoriness by approximately 150 Dec C as compared to more earlier recipes suing just natural raw materials.
Also, to increase corrosion resistance, a novel approach of introducing 3%-5% carbon in the refractory matrix has proven to useful. This approach challenges the traditionally accepted norm of not adding any carbon in refractory for ingot casting due to fear of carbon pick-up by molten steel thus changing the final intended composition. Research article and patent filed in 2009 on various carbon composition and formulations have listed resins, graphite, carbon coating and pitch impregnation as sources of carbon. All carbon approach has led to very good results in terms of erosion or refractory materials thereby reducing NMIs to almost zero. Carbon also adds to non-wetting property of the refractory improving flow of material.
Research paper link: “New development on refractory hollowware materials for ingot casting” by Roberto de Paula Rettore, Erwan Gueguen, Gilbert Zieba.
