Increasing the number of uses of the refractories in the slide gates of large steel-teeming ladles

Abstract

In 1982 the Magnitogorsk Metallurgical Combine completed the changeover to slide gate teeming of steel from 300-and 230-ton steel teeming ladles.Composite periclase plates produced by Magnesite Combine with 96.5-97.0 wt.% magnesium oxide in the insert are used as the refractory elements of the slide gate. The steel is top poured into mblds from 230-ton ladles with two slide gates into 7.8-8.8 ton ingots and from 300-ton ladles with a single slide gate into 7.8-20.5 ton ingots. The large number of openings and closings and slowings (70-80) creates severe service conditions for the periclase plates in the slide gate, as the result of which its refractory elements are used only once.The quality of teeming is at the 96-97% level but in teeming manganese and alloy steels it is significantly lower. For example, in teeming types 18YuA, 09G2, and 30T metal as the result of the low wear resistance of the plates the lack of closure and leakage are 7-9%. As the result of insufficient life of the refractories and imperfections in the design of the slide gates the advantages of slide gate teeming have not been realized to full degree.At present Magnitogorsk Metallurgical Combine is a large user of magnesia refractories. Therefore the question of increasing the effectiveness and repetition of use of refractories in ladle slide gates is a pressing one.Tests conducted earlier in the combine of plates of pure brine magnesium oxide and of Bui magnesium carbonate with not less than 98 wt.% MgO showed the possibility of repeated use of a single set of refractories [i].