Dispensing – Processes of dispensing – Molten metal
Patent
1995-10-26
1997-10-28
Kastler, Scott
Dispensing
Processes of dispensing
Molten metal
222602, B22D 4120
Patent
active
056814976
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The use of fire-resistant plugging rods for regulating the flow of a metallic melt from a ladle or a tundish into an ingot mold has been known for a long time. For this purpose, the plugging rod is moved by a lifting device, that is adjacent to the outside of the tundish, in the direction of its longitudinal axis, as a result of which a pour-out opening, that is arranged at the bottom of the tundish, is opened to a greater or lesser extent whereby, in the lowered state, the plugging rod becomes engaged and flows completely into the pour-out opening. The flow of metallic melt is capable of being controlled as a result of this. Although such regulation is, in principle, very simple, special requirements are nevertheless set for the materials and the technical construction of the plugging rods in regard to the extreme conditions that prevail during the processing of steel. Thus the plugging rod must withstand the action of a metallic melt over several hours. In addition, the plugging rod must also be suitable for withstanding the intense temperature variations, that act on the plugging rod during a casting process, and to withstand the laterally acting forces that are produced by the buoyancy of the metallic melt and that exert a strong bending moment on the plugging rod. Breakage of the plugging rod inevitably leads to the situation where pouring out can no longer be shut off and this leads, as a consequence, to uncontrolled flowing out of the melt. It therefore represents a considerable safety risk.
In the case of an earlier known form of embodiment, the plugging rod consists of a steel rod that has been provided with a screw thread at one end onto which the actual ceramic plug is screwed that engages in the pour-out opening of the tundish during later use. Above the plug, several ceramic plugging tubes that engage with one another at their front surfaces via a groove and spring and that completely encase the steel rod are pushed on from the side of the steel rod that is opposite the plug in such a way that, in the case of a tundish that is filled with a steel melt and a completely lowered plugging rod, the part of the plugging rod that is jacketed by the plugging tubes projects out of the melt by a certain length. The plugging rod is mounted in the lifting device via the upper end of the steel rod. Since direct contact of the melt with the steel rod would lead to the immediate melting through thereof, special attention has to be paid with such a plugging rod, that is made from several parts (plugs, plugging tubes), to the feature that the connections between the individual parts are leakproof in terms of the penetration of the steel melt. The connection locations are therefore additionally cemented. The plugging rods that are prepared are dried in a drying oven at approximately 100.degree. C. for approximately two days prior to their use.
A disadvantageous feature in the case of this earlier form of embodiment is that the preparation of the plugging rods requires relatively high expenditure on site in terms of material and labor. The steel rods also tend to distort as a result of the temperature gradients and variations that arise during casting and this easily leads to breakage of the jacketing and can thus lead to destruction of the plugging rod. These disadvantages and the knowledge that, as a result of the introduction of inert gases--such as, for example, argon--into the steel melt, non-metallic contaminants are, on the one hand, transported to the bath surface of the melt as a result of their interaction with the gas bubbles and, on the other hand, the formation of oxide during the casting process is reduced, have led to the development of ceramic plugging rods that are manufactured in one piece, as a result of which the inert gas is capable of being introduced simultaneously into the steel melt. These one-piece plugging rods, that are used almost exclusively in the manufacture of steel today, have a central longitudinal hole, that does not break through its lower end, an
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