METALLURGICAL CONTAINER

Abstract: Metallurgical container, such as a ladle, tundish, casting box or furnace, provided with a heating device comprising an inductive heating means. According to the invention said heating device (2) consists of a tube-like portion connected or connectable to the bottom or the lower portion of the side walls of the container. At least one valve (4), such as a sliding valve, is connected to the tube-like portion, and by means of an inductive heating coil (3) and/or an electromagnetic stirrer arranged in or around said tube-like portion the melt in the heating device can be subjected to stirring. The tube-like por­ tion is preferably formed as an outlet part (2) of the container.

Description: The invention relates to a metallurgical container according to the precharacterising part of claim 1. A metallurgical container of this kind is previously known from the US-A-4 243 092. The container can be a ladle, tundish, casting box or furnace. In horizontal continuous casting machines and also in other types of continuous casting machines, the mould is arranged so as to be connected to one side of the casting box. In order to be able rapidly to exchange moulds in the event of a disturbance, a sliding valve is mounted between the mould and the casting box and is normally fixed to the casting box. One problem in this connection is that upon start-up and in the case of long shutdown periods, the steel or other metal solidifies in front of the sliding valve, among other things because of heavy heat losses to the lining, which makes it impossible to start up or restart the casting process. The casting box may sometimes be formed as a crucible furnace with the lowermost coil turns located below the outlet. However, also in such a design there is a risk of freezing at the end of the outlet. The metallurgical container disclosed in the US-A-4 243 092 is a tundish from the bottom of which protrudes a vertical casting pipe that extends into a mould vertically arranged under the container. The casting pipe is surrounded by a stirrer generating a rotating electromagnetic field that causes a rotative movement of the melt while flowing down through the casting pipe 4. There is no valve near the outlet end of the casting pipe which would allow to completely interrupt the flow of melt through the casting pipe. Instead there is an electromagnetic valve placed at the lower portion of the casting pipe that serves to control the level of molten metal in the mould. This valve is neither intended for nor capable of completely interrupting the flow of melt through the casting pipe. For this purpose there is a sliding valve arranged at the tap hole in the bottom of the container proper. Thus, there is neither the danger that, when said sliding valve is closed, a freezing of the melt may occur in the casting pipe, nor the danger, that the high hydrostatic pressure of the molten metal in the casting pipe could result in a rupture the pipe. The CH-A-444 390 discloses a container for molten metal with a tube-like outlet portion provided with a sliding valve. To prevent the molten metal from getting into contact with the sliding valve prior to casting, the outlet portion is provided with a filling material of solid state. The outlet channel portion that accommodates the solid filling material is surrounded by a heating device. The purpose of this heating device, the nature of which is not disclosed, is merely to melt the solid filling material immediately before the beginning of the casting. The Abstract of JP-A-59-30468 shows a metallurgical container with a relatively short tubular outlet nozzle which is equipped with a sliding valve. This valve is positioned very close to the bottom of the container thus preventing the lower portion of the outlet pipe from becoming clogged by frozen metal or being subjected to the hydrostatic pressure of the melt. When no teeming takes place, melt remains only in the relatively short upper portion of the outlet pipe that penetrates the wall of the metallurgical container. A electric coil is arranged to inductively heat the melt in said upper portion of the outlet pipe. No stirring of the melt in this outlet part portion is provided. The invention aims to provide a metallurgical container which can be completely shut near the lower end of the outlet part without the hazard of metal freezing in the outlet part or a rupture of the outlet part due to the high hydrostatic pressure. To achieve this aim the invention suggests a metallurgical container according to the introductory part of claim 1, which is characterized by the features of the characterizing part of claim 1. Further developments of the invention are characterized by the features of the additional claims. With the metallurgical container according to the invention the heating device is extended to such an extent that an induction coil with the necessary power is able to surround the molten metal part, the so-called "tail", thus arising. Thus, the molten metal can be heated, and usually stirred, in the outlet part to prevent freezing therein. In a preferred embodiment the heating device consists at least of 1 inductive heating coil positioned between the container and a valve, such as a sliding valve, and is formed as a tubular outlet part. The outlet part is reinforced tangentially and/or radially, which is important, among other things, because of the great hydrostatic pressure which often prevails in the outlet part of the container. The outlet part may be vertical, extending from the bottom of the container, or horizontal, or inclined, extending from the lower part of the ladle. The advantages of the subject-matter of the invention can be summarized as follows: 1) The molten metal in the outlet part and near the sliding valve is prevented from solidifying (freezing) in the case of a shutdown of the casting operation, for example in the case of a mould replacement. 2) The possibility of self-circulation up to and into the container prevents local overheating. 3) It compensates for temperature drops in the case of long casting times. 4) The bottom portion of the container can be formed so as to be completely emptied after completed casting; no valuable residues will remain. 5) The level of the bath surface can be lowered, for example by reducing the volume (height) of the casing box, while maintaining the ferrostatic pressure in the mould (see in Figure 1 where h represents the ferrostatic pressure). 6) The proposed heater, as well as the lined cylinder, is easy to dismantle and replace, which means short breakdowns. The inclination of the outlet part defined by the angle'alpha in Figure 1 may vary. A desirable location is at the bottom of conventional casting ladles in order to obtain, in combination with a sliding valve, a reliable opening mechanism. The invention will now be described in greater detail with reference to the accompanying drawings showing _ by way of example _ in Figure 1 an embodiment of a container according to the invention with an inclined outlet part, Figure 2 an embodiment of a container according to the invention with a horizontal outlet part, Figure 1 shows a casting container in the form of a ladle, tundish or furnace 1 for continuous casting which is provided with an inclined outlet part 2 connected to the bottom of the container. The angle of inclination, alpha, may be set optionally at different values; h represents the ferrostatic pressure. Around the outlet part 2, which is tubular, made of a refractory compound, and suitably reinforced tangentially and/or radially, there is arranged an induction coil 3. The induction coil 3 may also be made integral with the tubular outlet part 2. The reinforcement of the outlet part 2 may be made in accordance with EP-A-85 10 1148.6. This reinforcement is important in view of the considerable ferrostatic pressure. The inclination of the channel with the heater, i.e. the outlet part 2, may vary. It is combined with a valve, for example a sliding valve 4. The outlet part 2 and the sliding valve 4 are connected to a device according to the SE-A-8505505-1 (EP-A-86 11 5969.7), comprising a horizontal casting mould 5. Around this mould 5 there is arranged at least one electromagnetic stirrer (not shown) developing at least one component of force in the casting direction in order to improve the casting structure. Figure 2 shows a casting ladle 6 having a vertical outlet part 7. Also in this case the ladle may be designed in the same way as above (see Figure 1). The outlet part is formed with a surrounding or integral induction coil 8 around the tubular body 7 of a refractory material. The induction heater should not be mounted on the ladle 6 but at the casting station and in such a way that the "casting tail" of the ladle 6, when brought in proper position in relation to the induction heater, adopts a casting position. However, the heater can also be made movable and be located around the "casting tail" afterwards. The afore-described embodiments of the invention may be varied in many ways within the scope of the claims.

Claims: 1. Metallurgical container, such as a ladle, tundish, casting box or furnace, provided with an outlet part (2) having a tubular shape surrounded by a means for stirring the molten metal in the outlet part, characterized in that a valve (4) adapted to completely interrupt the flow of melt, for example a sliding valve, is positioned in the proximity of the outflow end of the outlet part (2), that the tubular outlet part is provided with tangential and/or axial reinforcement means in such a way as to withstand the hydrostatic pressure of the melt, and that the means for stirring consist of at least one inductive heating coil adapted to provide inductive stirring and heating of the melt in said outlet part when said valve is closed. 2. Metallurgical container according to claim 1, characterized in that the at least one inductive heating coil is positioned between the container and the valve (4, 16). 3. Metallurgical container according to claim 1 or 2, characterized in that said tubular outlet part is formed as an integral part (2, 7) of the container. 4. Metallurgical container according to any of the preceding claims, characterized in that the tubular outlet part consists of a refractory portion with an integral coil.

Inventors: GUSTAFSSON, BO, LARSSON, HANS-GUNNAR, LETTERMO, ALLAN, NORRMAN, TOR OLOV
Applicants: ASEA AB
Application year: 1987
Main classification: B22D11
IPC codes: B22D41, F27D3, B22D11, H05B6