gree of compaction of the zone of the steel teeming hold of the part is obtained by pressing of plates with an insert corresponding to the projecting portion.The specific wear of the hole in the experimental corundum plates in service is 2~ times less than in the plates pressed by the normal method. 1. 2.3. 4.The replacement of ladle stopper assemblies by slide valves has made it necessary to organize the production of refractory parts satisfying the requirements for teeming primarily rimmed, semikilled, and low-alloy steels.As experience has shown, teeming of electric furnace steel, including constructional, through slide valves with the use of magnesite composition refractories is accompanied by contraction of the teeming channel, narrowing of the stream, a reduction in the rate of filling of the molds, and, as the result, a breakdown in the method of teeming and poorer ingot quality [i, 2]. With two usages of a set of magnesite refractories in the gate valve a tendency is observed toward an increase in the nonmetallic inclusion content in the steel [1].It is known [3, 4] that rational selection of refractories for slide valves with a certain structure and properties promotes normalization of the process of teeming a single heat of steel and elimination of contraction of the teeming channel and skull formation in it with sufficient life in service.

The Ukrainian Scientific-Research Institute for Refractories together with the Dnepr Special Steel Electrometallurgica! Plant has conducted investigations [1][2][3][4] on the development and selection of refractory materials for slide valve parts in teeming of bearing and stainless steels, which are prone to clogging of the steel-teeming channel, for the purpose of providing stability in operation of the valve, a reduction in crust formation, and an increase in the times of use of the plates, nozzles, and well blocks.The service tests of mu!lite--corundum, mullite, and kaolin refractories showed that they answer these requirements since in use of them because of the reduced thermal conductivity in comparison with periclase parts there is a reduction in crust formation and clogging of the steel teeming channel and the teeming process is more regular without a reduction in steel quality [2,4].This article presents experience in the production of chamotte nozzles and nozzle collectors and service of them in the slide gates of steel-teeming ladles of stainless steel at the Dnepr Special Steel Plant.The parts of the experimental lot were produced at the Zaporozhe Refractory plant from the raw material used in the production of chamotte refractory parts, ShKGP chamotte, PLK-0 kaolin, and DN2 clay.The charge for the molding mixture consisted of granular chamotte with a water absorption of 3% containing about 39% A1203 and a mixture of ground kaolin and clay. The mixture, with a moisture content of about 6%, was prepared in mixing mills using the normal plant method for 4 min. The nozzles (No. 13) and the nozzle collectors (No. 23) with a height of 250 and 300 mm and a channel diameter of 80 and 60 mm, respectively, were formed on a 6.3MN hydraulic press under a pressure of about i00 MPa in two stages with premolding from below in view of the significant height of the part.The apparent density of the freshly formed raw material varied within limits of 2.20-2.25 and 2.13-2.16 g/cm 3 for the nozzles and the nozzle collectors, respectively.The parts were dried and fired in a 120 m long tunnel kiln with a maximum temperature of 1400~ The nozzles were placed on the kiln cars in the vertical position on a base of chamotte brick in two rows with one part of the upper row on four of the lower with the large diameter downward. The properties of the chamotte SHS-32 nozzles and the nozzle collectors met the requirements of Technical Specification 14-8-385--81 (Table I).For the more complete characteristics of the chamotte parts the heat resistance, thermal conductivity according to the method of [5], and boundary angle of wetting by the metal in relation to heating temperature [6] in comparison with high-alumina and periclase parts were also determined.The thermal conductivity of the slide gate parts is an important property in teeming of stainless steel.It is known [i, 2] that the intensity of formation of the crust on the walls of the teeming channel is in relation to the thermal conductivity of the refractory material.It has be...

As a result of the reconstruction of the shop, the furnace was shut down for the main maintenance after being used for 1 year.When the lining was inspected, it was established that it was still in a reasonable working state.The wear on the walls in the slag zone was 40-60 mm (20-25% of the original thickness).There was only very slight wear (5-10mm) below the level of the slag zone.As a result of the work carried out, a Soviet lining for LFR-2 CTO baleout pot furnace has been developed and tested.The resistance of this lining is as good as that of the lining made from imported mass.

It is known that in teeming of alloy constructional and high-alloy steels skull formation in the channel of a slide valve leads to a reduction in teeming rate, poorer ingot quality, and premature wear of the refractories caused by required burning out of the channel with oxygen.The configuration of the channel cross section, the length of hold of steel in the ladle, and preheating of the ladle before tapping of the heat are of great significance for normal teeming. It has also been established [1][2][3] that replacement of magnesia refractories with high alumina ones with lower thermal conductivity [4] causes a reduction in choking and skull formation in the slide valve channel.Experience in the service of slide valves has shown that, in addition to rational selection of refractory parts, no small role in the process of skull formation in teeming of steels containing components with a high affinity for oxygen is played by selection of the material of the packing which fills the cavity of the ladle nozzle to prevent premature entry of metal into the channel and solidification of it in contact with the plates.At the moment of opening of the valve the packing in the form of refractory powder material pours out of the channel and the molten metal freely flows from the ladle without the use of oxygen lancing.In steel plants various forms of materials (coke fines, chamotte, staurolite, nepheline ore, etc.) excluding burning through of the channel before the start of teeming are used as the packing of the nozzle [5][6][7].Investigation of the composition and structure of the skull on the surface of the teeming channel in relation to the refractory and nozzle channel packing used is significant in searching for methods of reducing choking of the channel and the nonmetallic inclusion content in the steel, especially in repeated use of slide valve refractory parts. However, until the present, thorough investigations have not been made in this direction.During teeming of steel from steel teeming ladles through slide valves accumulation in the lower portion of the collector-nozzle of a skull formed on the inner surface of the channel in the form of hanging icicles increasing with throttling of the stream, with movements from one bottom pouring assembly to another, and also with failure of the forming edge of the teeming channel is characteristic. With dropping into the ingot this skull increases the nonmetallic inclusion content [8] and reduces the qual• of the metal.

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