Dispensing – Molten metal dispensing – Flow controllers or assists
Patent
1990-03-13
1993-02-16
Kastler, Scott
Dispensing
Molten metal dispensing
Flow controllers or assists
222600, B22D 4126
Patent
active
051868458
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the pouring of liquids which are corrosive or at high temperature, particularly molten metals, such as steel.
One of the most widely used devices enabling molten liquids, such as steel, to be emptied from containers is of the so-called slide valve type.
This essentially entails sliding over one another two plates of appropriate metal, which is refractory in the case of molten metals.
One of these plates is fixed and the other movable; each of them is provided with an aperture of appropriate diameter.
The coincidence of these apertures to a greater or lesser extent enables the flow to be regulated.
Non-coincidence of the apertures stops the emptying operation.
The relative displacement of the plates may be linear or rotary: move on a straight line; move in a circle.
In the case of the pouring of steel, the irruption of the metal gives rise to a violent thermal shock in the refractory plates, thus causing cracks which are detrimental in various respects' particularly: problematical; through the flow of rapidly moving metal.
In order to withstand the various stresses, ferrostatic pressure, temperature of the metal, sliding characteristics, and so on, the plates must in fact be made of appropriate materials, having a high content of alumina, magnesia, zirconium' and the like, which are particularly sensitive to thermal shocks.
Moreover, the very operating principle of sliding closure means known at the present time concentrates wear on the plates in one or two zones situated on the path of the relative displacement of the plates.
This results in the ovalization of the holes in the plates, which is extended by "tongue"-shaped erosion, which finally entails the premature rejection of the plates.
These remarks are equally applicable to devices of the three-plate type, in which the movable plate slides between two fixed plates.
The present invention seeks to avoid to the greatest possible extent such cracks and such premature wear on the plates.
The studies which we have carried out have shown us that, although the nature of the materials used for the refractory plates makes them particularly sensitive to thermal shocks, the appearance of the cracks is essentially due to the asymmetrical shape of the plates.
The starting point for the thermal shock is in fact situated in the pouring apertures, where a jet of molten metal passes at high temperature, particularly in the case of steel.
The heat then diffuses towards the periphery of the plate.
In all cases known at the present time, in order to reach the periphery of the plate, where a substantially lower temperature prevails, the heat wave must travel over paths of very different lengths, so that considerable breaking tensions are produced.
This will easily be understood on examination of the configuration of the linear or rotary slide valve plates, provided with one or more apertures, which are used at the present time.
It therefore appears that the ideal solution is to develop a linear closure means having round plates and a single central aperture.
In the remainder of the description given below both the term "plate" and the term "closure member" will be used, depending on whether the height is small, similar or large in relation to the outside diameter.
In this closure means the path to be travelled by the heat wave between the pouring aperture and the periphery is the same in all directions.
The thickness of the plate or closure member is also of importance, since the first face is in contact with the other plate or member and the second face is directed either towards the container or towards the environment.
However, the tendency to break or crack is more or less great depending on the nature of the refractory material, whose physical properties, such as thermal expansion, thermal conductivity, and so on, vary substantially.
This means that a range of tolerance exists between the paths travelled by the heat wave between its starting point (periphery of the pouring aperture) and its finish point (periphery of the plate).
This t
REFERENCES:
patent: 3764042 (1973-10-01), Shapland et al.
patent: 4586699 (1986-05-01), Bachmann et al.
patent: 4732304 (1988-03-01), Yoshihara
patent: 4747580 (1988-05-01), Tinnes et al.
Iron and Steel Engineer, "Nippon Kokan's rotary nozzle system for teeming and continuous casting" pp. 117-124 Nov. 1973.
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