An alternative lining of steel ladles: technical and economic aspects

Abstract

Quality of steel ladles lining to a big extent determine the economic efficiency of steel-making operation. Direct costs on the refractory lining of them can reach 30–50 % of the costs of lining of a steel-making complex. Experience of utilization of refractory materials of different composition considered with the purpose of efficiency increase of refractory materials application in the steel ladles lining under conditions of steel ladle treatment. Considerable abilities shown to make the lining of steel ladle walls and bottom by both carbon-containing and carbon-free refractory materials taking into account the economic aspect. Lining base of steel-making facilities — BOFs, EAFs and steel ladles — is composed by periclase-carbon (MgO–C) refractories. However those refractories have a high heat conductivity, that effects on the heat operation of steel ladles. When using MgO–С materials, vertical fractures can appear in the ladle walls lining as its residual thickness becomes small. Under definite conditions a working lining chipping takes place, problems appear with lining destruction in the pieces angles with cavities formation at the pieces joining. To level the MgO–С drawbacks, periclase-alumo-carbon (MgO–Al2O3–С) and alumo-periclase-carbon (Al2O3–MgO–С) refractory products are used. Al2O3–MgO–C refractories are widely used in most erosion-intensive lining zone — in the combatting place of steel ladle bottom lining. In Russia monolithic lining of steel ladle bottom is successfully displacing the lining by piece products, including alumo-periclase-carbon ones. Such a replace enables to decrease specific refractory consumption and specific costs of them. At present the technology of concrete application to bottom is implemented for ladles of BOF- and steel-making shops. A technology of concrete ladle walls and bottom is intensively implemented for 120–180-ton ladles. The concrete lining of steel ladles has the following advantages: high withstandability against impregnation by metal-slag melt; absence of metal carbonization by the carbon from ladle lining; increase of running duration of safety lining layer by 2–2.5 times; absence of necessity to use nest blocks in both steel outlet unit and for bottom blow-off lance; absence of cracks in lining, wash-outs in seams, angles and edges of pieces; decrease of gaseous hydrocarbon emissions(phenol, formaldehyde, benzapilene) during lining drying, heating-up and operation (only slag belt remains, where pieces have organic binders); saving of materials, working time and manpower while making and maintain the lining; decrease of specific consumption and specific costs for lining per 1t of steel. For lining of steel ladles of big volumes (more 250 t) alumo-periclase (alumo-spinel) products are widely used in China, Europe and Japan. For such a lining the thermo-mechanical tension, arising in monolithic ladle lining, has a less importance, including at its replacing with metal by using crane. It is easier for the products to compensate the ladle geometry change, resulted in metal shall geometry change in time. A positive influence of carbon-free lining, as well as a lining with low content of magnesium oxide, on metal quality noted, first of all for low- and ultralow carbon grades, and pipe low-alloyed steels.