Metallurgical apparatus – Means sealing or opening aperture in vessel – By means plugging aperture
Reexamination Certificate
1999-09-27
2001-06-05
Kastler, Scott (Department: 1742)
Metallurgical apparatus
Means sealing or opening aperture in vessel
By means plugging aperture
C501S129000
Reexamination Certificate
active
06241941
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a device for sealing the tap hole of a tiltable converter with a sealing plug consisting of a front metal plate which points towards the inside of the converter and melts on impact by liquid steel and a setting tool via which the sealing plug can be inserted into the tap hole and is deformable therein against the wall thereof, the sealing plug having a cylindrical plastic core covered by the front metal plate and a base plate, which are connected displaceably with respect to one another to the setting tool.
Tiltable converters have, in a suitable place in the converter wall above the tank level, a discharge orifice or a tap hole for conveying the liquid steel into the tapping ladle. For emptying, the converter is tipped into such a position that the steel flows through the tap hole into the attached ladle. As specifically lighter slag of varying viscosity always floats on the molten metal, during the tipping process this slag inevitably reaches the tap hole first and thus fairly large amounts of flush slag reach the tapping ladle. For numerous subsequent metallurgical processes the presence of oxygen-rich slag frequently enriched with phosphorus or sulphur is a considerable disadvantage. There is therefore a demand for conveying the converter steel into the tapping ladle with as little slag as possible. A sealing plug for this purpose is known from EP 0 635 071, in which the front metal plate is designed to pass into a funnel-shaped channel which intersects the sealing plug and core and is designed to receive a drawing claw acting on the front metal plate. The sealing plug is pushed so far into the converter wall that with its front metal plate it is positioned approximately in alignment with the inside of the converter and is then set by pulling the claw. The front metal plate passes into a funnel-shaped channel, which intersects the sealing plug, so the fixing of the plug actually does take place on the inside of the converter and not on its outer wall. Once the sealing plug is correspondingly set, the front metal plate fuses and neither slag nor other parts can flow out through the tap hole. In fact the converter can be tipped, the front metal plate and also the funnel-shaped channel now melting on contact with the liquid steel and the steel being able to flow specifically into the ladle through the funnel-shaped channel. A sealing plug of this kind consists of refractory material, primarily aluminosilicate, bonding clay, water and mineral oil.
This gives rise to problems with regard to ease of handling. This is due on the one hand to the great weight of the sealing plug, and on the other hand to a high water consumption caused by using clay a s bonding agent, as well as, in particular, to the extremely rigid design and the associated difficult deformation of the sealing plug when it is placed into the converter hole.
SUMMARY OF THE INVENTION
The object of the invention is therefore to create a sealing plug which, owing to the composition of its material, guarantees better deformation properties, easier removability from the converter hole and therefore in general greater ease of handling, with the result, in particular, that sealing plugs of this kind can also be used in larger converters than formerly.
This object is achieved according to the invention in that the mixture of the c ore serving as refractory material has easily meltable hydrocarbon compounds. This plastics material guarantees considerably better properties compared with the formerly used bonding clay. This is demonstrated particularly by the fact that with the sealing plug according to the invention the opening behaviour when the converter is being tipped is greatly improved because the plastics material as a component of the sealing plug melts or evaporates. On the other hand the sealing plug equally guarantees that, owing to the high radiation heat on the inside of the converter, the metal plate melts and fuses with the refractory material into a firm cap, but there is no simultaneous fusing with the wall of the tap hole. The fused cap remains stable until, when the converter is tipped, it conducts the flush slag safely via the tap hole. The cap only breaks down under the ferrostatic pressure. The remaining plug material is carried out within a few seconds by the outflowing steel. This process is distinctly easier to handle with the design according to the invention, owing to the properties of the material of the plastics material.
A preferred embodiment of the invention proposes that the core has a proportion by weight of easily meltable hydrocarbon compounds of 10 to 40%.
It has proved to be particularly advantageous therein if the core has a weight proportion of easily meltable hydrocarbon compounds of 33%. With this proportion, particularly favourable opening of the sealing plug was observed.
It has proved to be advantageous if the permanent binders are silicates, the temporary binders cellulose material, the plasticisers polyelectrolytic alcohols and the liquifiers fatty acids. A material is thus created which ensures that the plug is effectively fixed in the tap hole during deformation without continuous fusing occurring. The remaining mass is also protected from disintegration by corresponding heat action. Advantageously it is further proposed that the plastics material is foam-like in design. The favourable fusing properties of the plastics material are exploited even better in this way. The foam is manufactured in such a way that it represents a surface which is closed as far as possible, a space advantage thereby being achieved.
It is particularly advantageous if the plastics material consisting of hydrocarbon compounds is a polystyrene foam. This material has the advantage that its use causes no excessively high costs and it is optimally suited for processing with the other materials, so the sealing plug according to the invention guarantees reliable operation. Polystyrene with a low weight ensures that the sealing plug is pressed out of the tap hole at the most favourable moment. In particular the way these hydrocarbon compounds melt or evaporate advantageously causes parts of the sealing plug to dissolve and even less remaining plug material is carried out by the outflowing steel.
To simplify handling the invention proposes that the plastics material has the shape of balls. These balls guarantee the desired deformability of the sealing plug on its installation in the tap hole. The sealing plug is inserted into the tap hole with the aid of the setting tool. Via the lever system of the setting tool the drawing claw is pulled on to the front metal plate, whereby a pressure is exerted on the material which now deforms until the diameter of the tap hole has been completely filled. Small balls prove to be best for this process, as they adapt optimally to the movements and deformations.
It is particularly advantageous if the plastics material balls have a size of 1 to 2 mm. By choosing these extremely small plastics material balls uniform and spacious distribution is ensured. It is even possible to achieve spaces with these extremely small plastics material balls. Altogether a texture results which, owing to its fine structure, is quasi solid, while at the same time it is guaranteed that the sealing plug according to the invention fulfils its required function and is pressed out of the tap hole with as good control as possible.
For better bonding of the plastics material balls into the total mass it is proposed that the plastics material balls are provided with wetting agents. The plastics material balls provided with wetting agents are consequently coated with the clay, resulting in a more favourable structure of the material.
In addition it is proposed that the plastics material is fibrous in design. By this measure the wetting action is intensified and a more favourable and more uniform distribution of the material of the plug guaranteed.
Owing to the design of the sealing plug according to the invention the possibility now arises of arranging
Creighton Wray James
Kastler Scott
Narasimhan Meera P.
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