Use of different refractories in steel production at the oskol electrometallurgical combine

Abstract

666.764The electric steelmaking shop at the Oskol Electrometallurgical Combine (Ot~MK) includes four 150-ton electric furnaces with 90-MVA transformers, two integrated steel-finishing units (ISFUs) with 24-MVA transformers, four radial continuous casters for casting 300 x 360 semifinished products, two batch vacuum-degassing units, two units for injecting powdered desulfurizers, and two units for argon injection of the metal in the ladle. Ladle capacity is 150 tons and tundish capacity is 25 tons.Before introduction of the ISFUs in 1995, the working layer of the walls of the ladles was formed by using the following materials: mullite-corundum bricks of grade MKS-72 from the Borovichsk Refractories Combine and the same type of bricks of grades MKS-72 and MKB-75 from the Semiluki Refractories Plant. The slag zone and bottom of the ladles were lined with PKhS periclase-chromite bricks made by the "Magnezit" Combine. The average life of the lining was 23 heats with one intermediate replacement of the lining of the slag zone and the bottom; refractories consumption for the working layer was 10.8 kg/ton steel.During the introduction-of the ISFUs, the Oskol combine tried lining the slag zone with domestic periclase-carbon bricks of grades PUPE and PUSK, made by the Magnezit Combine. Accidents occurred in both cases, with molten metal escaping through the slag zone during treatment of the steel on the ISFU. The PUPE-grade bricks lasted three heats before burn-through, while the PUSK-grade products lasted five heats. The OEMK henceforth abandoned the use of domestic refractories in the working layer of ladles used on ISFUs.In 1994, tests were begun of periclase-carbon refractories made by the Austrian company Radex. The lining method proposed by the company for the working layer of the ladles involved the use of universal bricks (SU-format) of different levels of quality. Bricks of better quality were to be used in the slag zone. The use of this method increased the average life of the working layer of the walls and the slag zone to 47 heats with one intermediate replacement of the lining of the bottom; refractories consumption for the working layer of the ladles decreased by a factor of 2.2 to 5.0 kg/ton steel. However, the given lining scheme did have the following shortcomings: the structural strength of the lining was low -it periodically fractured during the removal of encrusted metal and slag from the ladle; the wear of the lining was nonuniform about the perimeter and over the height of the ladle.Several measures to improve the durability of the lining of the ladles and reduce unit refractory consumption were introduced during the period 1996-1997:-the universal products were replaced by wedge-shaped (P-format) products to increase structural strength; -refractories of different thicknesses were used in the lining -the regions characterized by intensive wear (the slag zone, a section of the "impact" wall and the wall in the operating region of the injection block) were reinforced, while the regions that undergo min...