IMPROVING THE QUALITY AND CASTABILITY OF STEEL BY IMPROVING THE TECHNOLOGY USED FOR DEOXIDATION DURING ITS TREATMENT OUTSIDE THE FURNACE

摘要

As is known, the properties of rolled metal products depend on the chemical composition, quantity, size, distribution, and morphology of the nonmetallic inclusions in them. Most steels are presently deoxidized with aluminum, which is not only a good deoxidant but also an effective inoculant. Aluminum ensures the formation of a denser structure with the prescribed fine-grained composition, as well as high marks for ductility and toughness. However, the deoxidation operation forms alumina as a product, and even small amounts of the latter can sharply reduce the fluidity of the steel and lead to obstruction of the channel of the pouring nozzles. Acting as stress concentrators and crack nucleation sites, sharp-edged crystalline inclusions of alumina in the steel lower its ductility and strength and are particularly dangerous when the steel is embritted by low temperatures and large cyclic loads.