Metallurgical apparatus – Means for melting or vaporizing metal or treating liquefied... – By providing – treating or protecting environment – e.g. – vacuum
Patent
1981-01-15
1982-10-26
Andrews, M. J.
Metallurgical apparatus
Means for melting or vaporizing metal or treating liquefied...
By providing, treating or protecting environment, e.g., vacuum
266218, 266233, 266901, 75 65R, 75 68R, C22B 904, F04F 700
Patent
active
043557899
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to metallurgy and more particularly to apparatus, namely, gas pumps, for stirring molten metal directly in a furnace where the metal is melted, such stirring being advantageously effected to enhance the rate of melting or to maintain uniformity of composition or temperature in a standing body of molten metal.
BACKGROUND OF THE INVENTION
A variety of devices have been used for stirring molten metal directly in the bath of a melting furnace. This invention proposes a gas pump for stirring molten metals, such as aluminium alloys, which is both effective and simple to carry out.
There is known a gas pump for stirring molten metal, which comprises a refractory-lined pipe provided with a removable cover through which the interior passage of the latter is brought in communication with a compressed gas line and with a vacuum line. The gas pump of this type is usually equipped with metal level detectors incorporated in the compressed gas pulse and vacuum control ciruit.
In the above-described gas pump use is made of the pulse energy of compressed gas applied to a standing body or portion of molten metal periodically withdrawn upwardly into the pipe interior under suction and then expelled therefrom under the action of compressed gas into the bath of a melting furnace. The expelled portion of metal is caused to move in the body of molten metal, entraining the adjacent layers thereof and thus stirring the melt. Then, another portion of molten metal is drawn in the pipe under suction and the operating cycle is resumed in the same order.
Although the prior-art gas pump makes it possible to increase production efficiency of a melting furnace, it has a number of serious disadvantages. For example, a portion of molten metal withdrawn from the bath into the pipe interior is taken from the same place in the bath and expelled into the zone practically adjacent thereto. As a result, the heat and mass exchange in the bath between the upper and lower layers of metal is insufficient, especially where large-capacity melting units are used with a considerable depth of the bath wherein the difference in temperature between the layers of metal is considerable. In a case like this, the process efficiency is normally achieved by increasing the speed at which molten metal is discharged from the pump. This, however, is associated with a further increase in the coefficient of energy transfer from compressed gas to molten metal, which is also limited by the excessive gas and slag formation at the gas-metal interface. This factor is another obstacle to obtaining a desired effect in stirring. An increase in the number of pumps at a melting furnace is no solution to the problem either. On the contrary, this will only complicate its operation and construction, and will lead to an excessive consumption of gas.
It should be observed that the intensity of the heat and mass exchange between the upper hot and lower cold layers of metal in the furnace bath has direct effect on the rate of melting, the quality of metal produced, and the consumption of fuel. The rate of heat and mass exchange in the furnace bath can be stepped up by causing molten metal to flow in the vertical direction. However, this task is impossible to carry out with the existing constructions of gas pumps. From the above it follows that the gas pumps currently used for stirring of molten metal suffer from a number of disadvantages which, if obviated, will allow effective stirring of molten metal to be achieved in the course of melting operation performed in the furnace bath.
It is undisputable fact that the economy of energy is one of the most important problems confronting modern industry to-day. Therefore, a further increase in the production capacity of metallurgical units by providing favourable conditions for complete and rapid heat and mass exchange process will be a substantial contribution to the solution of this problem. And the advantages accruing therefrom are many. Apart from substantial savings in fuel it also
REFERENCES:
patent: 3015190 (1962-01-01), Arbeit
patent: 3759635 (1973-09-01), Carter et al.
patent: 4008884 (1977-02-01), Fitzpatrick
Andreev Vladimir F.
Dolzhenkov Boris S.
Pimenov Vitalii A.
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