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669.183.4 The processing of metallurgical wastes has received much attention in recent years [1][2][3]. One approach to solving this problem is recycling.In searching tbr optimum methods of utilizing refining products, we examined the feasibility of using bank open-hearth slag to make up the sills of open-hearth and two-bath furnaces. This material was chosen because the sills must have certain service properties: resistance to erosion and high temperatures and stability under the ferrostatic and hydrodynamic pressure exerted by the molten metal and slag. The material must also be inexpensive and readily available. Raw dolomite has traditionally been used in this capacity, but in recent years it has been replaced by crushed limestone. In connection with the continually rising cost of limestone, an attempt was made to replace it with a cheaper material -graded bank slag from open-hearth operations.When the sills are being formed, a substantial portion of the crushed limestone is usually spilled onto the working platform. It is then raked off by the charging machine and dropped into a slag ladle. The part of the sill left after a heat is also placed in the ladle.A slag sample of the 10-40 mm traction that was obtained by the inquartation method showed that 15% of it was crushed limestone. The presence of such a quantity of partially roasted limestone allowed repeat use of the slag as a material for sill construction, even though the main mineralogical components of the slag -wollastonite, fayalite, and olivine -have a melting point of 1200-1300~In addition, bank slag has a higher bulk density than crushed rock (1.8 versus 1.55 kg/m3). It is thus more resistant to the thermal and chemical action of the furnace slag and metal before the metal subsides to a level below the main sills.In trial heats, we visually evaluated the condition of the sills and studied the effect of dissolving bank slag on the process of refining the steel to rid it of harmful impurities -sulfur and phosphorus. It was established that the sills made of slag have the necessary service properties and reliably prevent "escape" of the pig iron and slag from the furnace. On the two-bath furnaces, the degree of wear of sills made of slag was the same as for sills made of crushed limestone. This can be attributed to the rapidity of the process (the time from the beginning of the hot-metal addition to the beginning of tapping averaged 2.5 h) and the fact that a source of heat energy was located inside the bath -in the region where oxygen was injected into the molten metal.In the open-hearth fnmaces, some melting of the slag sills was observed before the end of the heating period. Wear was especially noticeable in the sill of the working door, where the molten pig iron is charged. The sills had to be partially rebuilt in certain heats, as they do when cmshed limestone is used (particularly for the sill of the middle charging door).

When the stopper of a steel-pouring ladle equipped with a slide gate is replaced, it is difficult to ensure that the molten steel will pour freely through the orifice in the gate when it is opened.The problem stems from the fact that molten steel being tapped from the fumace comes into contact with steel that is already in the orifice from the previous heat. Since these two materials differ appreciably in density, some of the residual steel is washed out of the orifice. The newly free volume of the orifice is filled with the steel from the current heat, which in turn forms a "plug" inside the orifice when it solidifies. A slag skin is also formed at the site where the two materials come into contact, the thickness of this skin being determined by the density and refractoriness of the lining formed by the particles of the material from the previous heat.To break up the metal-slag plug, it is necessary to "wash" the orifice with oxygen. This operation is performed with an L-shaped steel pipe, the short end of which has a length of 0.6-0.8 m. Such washing destroys the cylindrical shape of the orifice, which leads to an increase in the number of ingots that are cast with an unorganized stream of metal (fan-shaped, slanting, etc.) and with the orifice not completely closed as casting proceeds from one ingot mold (fountain) to the next. This leads to "seepage."Based on the above, the main requirement that must be met by the material used to close the orifice in a steel-pouring nozzle is that it form a slag skin which is easily broken up either by the pressure of the molten steel after the slide gate has been opened or at least by a single "washing" with oxygen.One method that has been proposed to prevent material from being washed out of the nozzle orifice involves completely filling the orifice with a refractory. The material of the upper layer expands when heated, leading to the formation of a slag skin [1]. The problem with this method is that it is necessary to heat the ladle after the nozzle orifice has been closed. We tried a simpler method of closing the orifice -placing a metal plate on top of the orifice after it has been filled with the refractory. Table 1 presents data on the results of tests performed with different materials to close the orifice in the nozzle of a 250-ton steel-pouring ladle.An analysis shows that the worst results in terms of burning through the hole, determined by the number of bendings of the oxygen pipe, were obtained by using coke fines, a molding-sand mixture, and natural sand. The poor results in this case are attributable to the fact that coke fines are easily washed from the orifice, resulting in the formation of a relatively thick metallic plug; the natural sand and the molding-sand mixture, characterized by a lower refractoriness compared to the other materials, form a thick slag skin. Better results were obtained with the use of coke fines, mill scale, and powdered fireclay, which is due to the fact that these materials "pack" the orifice more tightly and prevent its penetratio...

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