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Extensive use is made in modern steel-melting practice of buckets, converters, and arc furnaces in which gas is supplied to the metal through the bottom lining. There is fairly rapid wear on the bottom lining, which requires techniques for periodic hot repair (e.g., lining) with the retention of gas permeability in the repaired layer. One approach is to freeze a layer of liquid slag there with continuous gas blowing [1]. The scope for this method is examined here.The laboratory experiments were performed with a resistance furnace (Fig. 1) having a tubular carbon heater. The crucible was placed in the isothermal zone, with the walls provided by a graphite robe. The cylindrical periclase bottom had one axial hole with diameter 1-2 mm or was formed from a porous material having a gas permeability coefficient of 22/xm 2, open porosity 25%, and mean pore radius 70-100 ~m.We melted 450 g of the silicate Na20-SiO2, melting point about 800~ in the crucible and superheated it to 1300~ This layer of liquid with diameter and depth of 60 mm was blown through the central hole or pores with helium at 50 liter/min until it solidified, with the helium supplied from a cylinder with a pressure reducer and RMF-25 flowmeter.The crucible was cooled in one of three ways. The first was simply switching off the oven. In the second, predominantly radial heat loss was produced by rapidly inserting a steel cooler (hollow cylinder) at the wall of the crucible. In the third, the heat loss was nearly vertical (from the top downward) because the oven was not switched off but the crucible was lowered at 1.5 cm/min with a screw mechanism, and the bottom and wall were rapidly cooled by water as they emerged from the heater.The solidified specimens were extracted, examined, and photographed, and were then cut up in order to determine the numbers of blind and through channels, whose diameters were measured. Figure 2 shows schematic vertical sections.In the first mode of cooling, the rapid radiation of heat from the open surface led to its solidfying first, and it ceased to pass the gas injected in any way, numerous bubbles of which were seen throughout the volume (Fig. 2a). In the second form, the blowing was provided via the central hole, so at the center, where the silicate remained liquid longest, it was completely removed with the rising gas, so there was a through channel of height 60 mm with bottom diameter 1-2 mm and top diameter 5-6 mm (Fig. 2b).In the third case, the experiments were conducted with blowing through all the pores at the bottom. As the gas jets remained continuous up to a certain height, with vertical solidification (from the bottom upwards), 15-20 capillary channels were formed with diameters of 1-2 mm, about 3/4 of which were through ones (Fig. 2c).The through channel formation mechanism found in the second method in the laboratory experiments was used in making gas-permeable bottoms for 160 ton converters at Chelyabinsk Metallurgical Corporation. After the liquid had been poured, 7-10 ton of slag remained, and this was sup...

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Based on the expertise gained in the use of a 350-ton converter at the WSIWS Joint-Stock Co., blowing facilities and regimes have been modified. Low-temperature slag splashing is numerically simulated for a top-blown tuyere using tips with single and double-row nozzle arrangement. A slag-splashing tuyere fitted with a steel tip with a double-row arrangement of nozzles has been designed. Ways to improve the melting technology using modified tuyeres combining slag splashing and flame gunning operations and to improve repair of the lining using a vertical tuyere are proposed.At the WSISW Joint-Stock Co., the vessel campaign in converter-based steelmaking technology (with slag containing 8 -14% MgO) could be extended to 2500 -3000 heats (using techniques such as slag splashing, extra gunning, and repair of the refractory lining); for comparison, the vessel campaigns reported from the Magnitogorsk Iron and Steel Works (MISW) were 3700 -4000 heats [2], and from the Severstal' JSC, 4500 heats [3]. Foreign manufacturers, owing to the effective use of auxiliary techniques and equipment (mechanical drive, cooling systems for the converter and tuyeres, systems for escape, treatment, and entrapment of the converter gas, transfer facilities for steel and slag), could extend the vessel campaign to 30,000 heats or even more [4 -7]. Furthermore, a common practice with foreign manufacturers is the prerefining of iron prior to the converter process, careful scrap preparation, and the use of advanced automation [8,9]. The use of dynamic systems for controlling the melting process makes it possible to maintain a high efficiency (reaching 90%) in the control of carbon content ± 0.02% and melting temperature ± 12°C even in the early stage of charging a converter. Laser-based measuring systems [10] provide information about thickness of the refractory lining throughout the course of a campaign, which makes it possible to enhance the efficiency of repair of the lining, for example, by slag blowout or gunning.Melting techniques as commonly practiced in the domestic converter technology prescribe the removal of sulfur and phosphorus (as high as possible) prior to the blow of the bath; the hot repair of the vessel lining is commonly made by applying the lining slag, or the scull, by blowing out the final slag for this purpose, or by flame gunning using a patching material based on calcined magnesite or dolomite.Introduction of a technology for blowing out the final slag (containing 8 -14% MgO) with nitrogen injected through the top-blown oxygen tuyere turned out to be a challenging problem for foreign [6,7] and domestic technologists [11,12]. A rational idea was to use a special elongated tuyere [13]. Such tuyeres were employed to good effect to blow out slag with nitrogen at a flow rate of 320 -500 m 3 /min in 375-ton converters at the MISW JSC [12]. However, later the idea was abandoned, and for slagging the lining, technologists continued to use conventional oxygen tuyeres to blow nitrogen at a flow rate of 900 -1200 m 3 /min [2]. The o...

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