The use of unfired magnesite--chromite refractories in the metal zone of ladles of the ASEA-SKF equipment instead of high-alumina grade MKO-72 products improves the desulfuration of the metal when we use out-of-furnace refining; it prevents a reduction in the basicity of the slag due to destruction of the lining. Furthermore, the cost of the unfired basic articles is lower than for high alumina, and their manufacture requires much less fuel and energy outlay.Publications [1, 2] give the results of testing unfired magnesite--chromite in ladles. The main problem in making these is to ensure the minimum change in volume and strength during heating. A magnesia-spinel compound with a magnesium sulfate bond meets this requirement.To determine the technical parameters for such refractories in laboratory conditions, tests were made on two batches (Nos. i and 2). The starting materials consisted of waste magnesite--chromite brick (12.0%* Cr203) produced by the Magnezit Factory, chromite (45~ Cr203), and electrocorundum (98% A12Q ). Boric acid was added to stabilize the properties of the refractories during low-temperature heat treatment [3], and sulfite lye (pot-still residues) to confer green strength after pressing. The compositions of the batches are shown in Table 1.The monofraction powders were made separately. The combined-grind mixture was obtained by mixing in a vibromill the constituents premilled to fractions --0.063 mm. The magnesium sulfate and boric acid were added to the combined-grind mixture.

One of the important questions in organization of pouring of steel into a billet continuous casting machine with a small cross section mold is selection of the material and design of the pony ladle nonswirl nozzle providing a stable rate of pouring of the metal for a long time (up to 5 h of continuous operation).A stable pouring rate is a necessary condition for obtaining high-quality cast billets and failure-free operation of the equipment.For example, with a pouring rate of less than 1.7 m/min clogging of the channel with molten metal occurs while with pouring of the steel at a rate of more than 2.5 m/min the metal billet leaving the zone of secondary cooling does not have a completely solidifed axial portion.Providing a constant pouring rate is also complex as the result of the relationship to many production parameters.Under otherwise equal conditions the pouring rate of steel depends upon the dimensions of the nozzle channel.Forpouring into small cross section molds nonswirl nozzles with a channel diameter from 14 to 15.5 mm are used and therefore insignificant clogging or erosion of the channel leads to significant changes in pouring rate. Tests have shown that the use of nozzles with a channel diameter of 14 mm is most desirable since with the use of them the pouring rate stabilizes and is 1.8-2.0 m/min.The first domestic nonswirl nozzles for pouring of steel into small cross section molds were produced at Krasnoarmeisk Dinas Plant and were introduced under the conditions of the Melt Shop of Belorussian Metallurgical Plant in 1985 in place of Didier-Werke parts.Billets with a cross section of 125 x 125 mm up to 12 m long of killed constructional and low-alloy types of steels are cast on two curved six-strand continuous billet casting machines of the plant. The pouring is done through a 10-ton pony ladle by the "heat on heat" method in a series of three heats (average weight of a single heat 102 tons).The nozzle unit of the pony ladle consists of a zirconic composition nonswirl nozzle and an aluminosilicate funnel.The space between the nozzle unit and the reinforcing lining of the bottom is filled with corundum or quartz-clay compound.A feature of pouring of steel in the continuous billet casting machines of Beiorussian Metallurgical Plant is the free flow of the stream from the pony ladle into the open pool of metal in the mold without protection from secondary oxidation.The rate of flow of the stream is controlled by controlling the level of filling of the ladle and also by supplying gaseous oxygen for cleaning out the channel with a decrease in the pouring rate below the allowable.The absence of a stopper and controlling mechanism imposes increased requirements for the nonswirl nozzle under the action of the molten metal and the gmseous oxygen.Investigations of Didier-Werke and nonswirl nozzles showed that they consist primarily of baddeleyite and zircon (Fig. I). The chemical analysis of the nonswirl nozzles in wt.% is 23 SiO2, 0.90 CaO, 0.42 AI20 B, 0.40 Pe2Os, 0.44 MgO, 73.6 ZrO2, and 2-6 Y203, the op...

The quality of the gunited coating makes it possible to continuously cast up to five heats in a single series and the specific consumption of the guniting compound is 1.5-1.6 kg/tonne of steel. The hardened residues of metal and slag are removed from the tundish without difficulties. No increase in nonmetallic inclusion content of the steel in comparison with the period of use of imported compounds was noted. CONCLUSIONSUnder the conditions of the Electric Melt Shop of Belorussian Metallurgical Plant a guniting compound composition has been developed and a production method has been intnoduced for guniting of the lining of tundishes for casting of cord, cable, and alloy steels. i. 2.3.

In 1977 the Izhorskii Works Production Union put into operation an imported furnace-ladle type installation for refining and vacuum treatment of steel outside the furnace (IRVO); this permits arc heating of the metal, electromagnetic mixing throughput the period of treatment, vacuum treatment and desulfurization of the metal, purging with oxygen and argon, and introduction of alloy components.The installation includes ( Fig. 1) a ladle 1 (70 or 150-ton), a car 2 for transporting the ladle with its fitted inductive mixer coils, a device 3 for arc heating (two stands), a vacuum system 4, and a system for blowing oxygen and argon.The distinguishing feature of this installation is the flexibility of performace of the possible technological operations, ensuring preparation of high-grade metal. Operation of the IRVO gave steels with mass fractions of sulfur and oxygen of 0.003 and 0.0005%, respectively, in the end sample; the hydrogen content after vacuum treatment of the steel was 1 cm 3 per 100 g of sample.Operation of the installation showed that refractory service conditions in it are more severe than in batch and circulation types. This is due to the great length of treatment (up to 5 h), to marked circulation of metal (as a result of electromagnetic mixing) and gaseous segregations during the period of vacuum treatment, to blowing with argon and oxygen, and to cooling of the ladles between fusions. Superheating of the ladle lining in the extraelectrode space during arc heating of steel is also observed. As a consequence the refractory consumption on the furnace lining, according to foreign data and the results of operation of imported refractories in the installation, is 10-15 kg per ton of processed steel, whereas in batch and circulation types it is 0.6-0.8 kg / ton.Abroad, under these service conditions high-alumina refractories, and in the most intensely worn slag belt of the lining magnesite-chromite refractories, are used in furnace-ladle installations [1-3]. Imported refractories were obtained in the period of initial mastery of the installation, and they were investigated with the aim of replacing them by home-produced ones (Table 1).Mineralogical analysis* showed that the bauxite artifacts used for the reinforcement and working linings of the ladles consist (Fig. 2a) of large grains of high-alumina composition (0.5-3 mm), small (0.5-1.5 mm)

The investigating results are given for the ferrouschromium slags using as the refractory materials to prepare the refractory concretes. The temperature range of their application was defned. It was established that the magnesia oxide addition considerably reduced the Chromium VI formation during service in composition of the refractory materials manufactured on base of the ferrous-chromium slags. Ref. 5. Tab. 4.