US3071362A - Immersion pipe for degassing metals by a vacuum - Google Patents

Description

INVENTOR A. LORENZ Filed May 21, 1959 Jan. 1, 1963 IMMERSION PIPE FOR DEGASSING METALS BY A VACUUM United States Patent many Filed May 21, 1959, Ser. No. 814,868 Claims priority, application Germany May 30, 1958 1 Claim. (Cl. 266-34) The present invention relates to an immersion pipe for degassing molten metals, particularly steel, by means of a vacuum apparatus.

The method of degassing molten metals and particularly steel by means of a vacuum is recently carried out by conducting the molten metal from one vessel through a pipe, which is immersed into the metal bath, in an upward direction into and through a continuously evacuated chamber in a second vessel which is disposed above the first vessel and then back downwardly into the first vessel. For thus conveying the molten metal from the lower vesesl through the immersion pipe into the upper vessel, a suitable gas is injected into the immersion pipe which then rises therein and takes along the molten metal into the upper evacuated chamber in which the gases contained in the metal itself as well as thegas used for conveying it are extracted by the vacuum. The point at which the conveying gas is injected into the molten metal is usually disposed at one side of the immersion pipe and at a relatively low level above the surface of the metal bath. It has, however, been found that the supplying of the gas at one side of the immersion pipe causes considerable difliculties since, because of the high viscosity of the molten metal, those parts of the pipe which are more remote from this point, and especially those at the side opposite to the gas inlet opening, will hardly be reached by and brought in contact with the gas, so that the molten metal will be very unevenly interspersed with such gas and the conveying action thereof upon the molten metal will not be very eflicient.

It is an object of the present invention to overcome these disadvantages in a very simple manner by providing the immersion pipe with an annular channel and a plurality of small gas inlet openings or a continuous peripheral opening rather than a single opening at one point as in previous immersion pipes. Therefore, the actual immersion pipe, that is, the lining on the inside of the metal pipe, which consists of a highly refractory material, preferably a ceramic material, is surrounded by an annular channel from which the conveying gas is passed through a series of small openings or one continuous opening around the periphery of the pipe to the inside thereof through which the molten metal is conveyed to the evacuated degassing chamber. These small inlet openings or the continuous slot are made of a size so that the conveying gas can pass from the outside into the molten metal but the relatively viscous metal cannot penetrate from the inside of the pipe into the annular channel.

According to the invention it has further been found that the immersion pipes used for degassing metals by means of a supplemental conveying gas are preferably made of several sections in which the ceramic lining portions of these sections fit so well upon each other without any intermediate sealing means that a narrow gap remains between the adjacent lining portions through which the conveying gas may be passed to the inside of the pipe.

These and other objects, features, and advantages of ice the present invention will become further apparent from.

which shows a longitudinal section of an immersion pipeaccording to one preferred embodiment of the invention.

As illustrated in the drawing, the immersion pipe according to the invention consists of two parts, namely, an outer steel jacket 1 and a lining member 2 of highly refractory and preferably ceramic material. By means of a flange 1' on the lower end of steel jacket 1, the latter is held at a spaced relation to lining member 2. A second pipe 4 of ceramic material is secured to the steel jacket 1 of the upper pipe by means of a flange ring 3, preferably by bolts, so as to be removable therefrom. For this purpose, the upper end of the lower ceramic pipe is made of a conical inner wall. The two flanges 1' and 3 are designed so as to secure the upper and lower ceramic pipes 2 and 4 in a fixed position relative to each other but so as to leave a narrow gap 5' between the adjacent end surfaces and a wider annular gap or channel 6 around the inner gap 5 between the outer parts of the conical flange and the inner parts of flange 1'. This flange 1' has a bore therein into which a pipe 7 is tightly inserted or secured through which the conveying gas as previously mentioned is supplied into a the annular channel 6 and from the latter to the inside of ceramic pipes 2 and 4. Thus when the immersion pipe is sunk to a sufficient depth into the metal bath, the conveying gas will pass from all sides into the molten metal in the pipe, and the buoyancy of the gas bubbles increasing in size as they rise in the metal will effect a uniform conveying action upon the metal, taking it along into the evacuated degassing vessel where this conveying gas as well as the oxidizing gases normally contained in the metal will be extracted therefrom by the vacuum.

The immersion pipe according to the present invention when used in degassing metals with a high melting point by means of an additional supply of a conveying gas not only produces the advantage of a more uniform conveying of the molten metal from the metal bath in the lower vessel into the vacuum chamber in the upper vessel but also the very important further advantage that the uniform entry of the conveying gas into the molten metal from all points around the periphery of the pipe results in a much more thorough intermixture of the gas with the metal than was possible prior to this invention. Consequently, particularly if the conveying gas is of the type which willexert a reducing action-upon the metal, the deoxidation of the molten metal will proceed much more uniformly than was hitherto possible.

By being composed of several parts, the immersion pipes according to the invention have the further advantage that no additional structural elements will be required for bringing the molten metal uniformly into contact with the specially injected conveying gas since the latter will pass automatic-ally into the metal through the narrow slot provided between the adjacent ceramic pipes and around the entire inner periphery thereof. Although naturally in place of a continuous narrow slot, a larger number of small radial inlet openings may be provided between the adjacent ceramic pipes, for example, in the form of serrations in the adjacent ends of one or both pipes, while the portions of the ends of the two pipes between these openings or serrations abut against each other, the provision of a continuous slot between the annular channel 6 and the inner pipe edges more safely excludes the danger that the openings might become clogged by the metal. The slot is therefore. made of a width sufiicient to permit the conveying gas to pass through it and enter into the metal but so narrow as to prevent the viscous metal from entering into it and from clogging it.

Although my invention has been illustrated and described with reference to the preferred embodiment thereof, I wish to have it understood that it is in no way limited to the details of such embodiment, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully described my invention,

In a continuous recycling device for the vacuum degassification of molten metal and having as elements vacuum degassing chamber means, a lower positioned container for holding molten metal, riser conduit means for conveying molten metal from said container to said chamber means, discharge conduit means for discharging molten metal from said chamber means into said container, and means for forcing gas bubbles into and through said riser conduit means, said riser and said discharge conduit means being with their immersion ends arranged in separate and spaced relation, the improvement which comprises in combination with said elements such riser conduit having a substantially metallic cylindrical jacket, a first cylindrical ceramic member arranged what I claim coaxially within said jacket and spaced lightly radially therefrom, a second cylindrical member, means associated with said jacket for mounting said second member in end to end axial relationship with said first member but spaced therefrom to form a narrow annular slot between adjacent ends of said members, said pipe being formed with an annular channel peripherally surrounding said slot, and a conduit connected to said channel for passing a gas therein to and from said channel through said slot for peripheral discharge to the inside of said pipe.

References Cited in the file of this patent UNITED STATES PATENTS 1,444,069 Gyger Feb. 6, 1923 1,686,713 Scott Oct. 9, 1928 2,825,104- Jones Mar. 4, 1958 2,837,790 Rozian June 10, 1958 FOREIGN PATENTS 1,057,342 Germany May 14, 1959

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