US3508743A - Apparatus for the purification of molten metal - Google Patents

Apparatus for the purification of molten metal Download PDF

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US3508743A
US3508743A US538296A US3508743DA US3508743A US 3508743 A US3508743 A US 3508743A US 538296 A US538296 A US 538296A US 3508743D A US3508743D A US 3508743DA US 3508743 A US3508743 A US 3508743A
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molten metal
chamber
vacuum chamber
metal
vacuum
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Frank F Erdelyi
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0081—Treating and handling under pressure
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum

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  • United States Patent US. Cl. 26634 6 Claims ABSTRACT OF THE DISCLOSURE Apparatus for treating molten metal comprising a vacuum chamber and a container for a quantity of molten metal to be treated including means for moving the chamber and container toward and away from each other and a molten metal conducting pipe connected in a sealed relation to the lower end of the vacuum vessel and to the container at a point below the level of molten metal.
  • Means are provided for subjecting the vacuum chamber to subatmospheric pressure suificient to draw a quantity of molten metal into the vacuum chamber and second means for simultaneously applying a pressure to the molten metal in the container which is greater than atmospheric pressure, so that the amount of molten metal drawn into the vacuum chamber is greater than that quantity therein resulting from the subatmospheric pressure alone.
  • the container may be disposed at an elevation greater than the lower end of the vacuum chamber to increase the quantity of molten metal in the chamber above that which would result from the subatmospheric pressure alone.
  • This invention relates to the purification of metals. It more particularly refers to the degassification of metals and especially to such metal degassification from metals which are moltent.
  • Such degassing action can take place by exposing the molten metal in a refractory lined container, otherwise known as ladle, to a reduced pressure, or, in order to increase the surface area for the molten metal exposed to the vacuum, by utilizing the metal movement during free fall, for instance, from a melting furnace into a ladle or from one ladle into another.
  • Still another principle is based on the metal transport from a container, or ladle, into an evacuated chamber where degassing can take place; such transport utilizes the pressure difference between atmosphere and the degassing chamber in order to create a barometric column of molten metal, thereby causing the metal to recirculate between the container and evacuated chamber by a corresponding mechanical movement of either the container or degassing chamber.
  • the vacuum chamber By selecting a chamber diameter smaller than the ladle diameter, it is possible for the vacuum chamber to come extremely close to the metal level in the ladle, only limited by the temperature radiation of such metal and heat ef- 3 fects on the exterior chamber material. This means that in such optimum case the maximum filling height in the evacuated chamber, approximately 1 meter, can be obtained. Since, however, the chamber diameter has to be kept small in reference to the ladle diameter, only a small portion of the molten metal can be transported into the degassing chamber, for instance about of the ladle contents.
  • each reduction in ladle filling height means a corresponding decrease in the filling height of the degassing chamber and, hence, an increase of degassing time which, as previously described, is limited due to the molten metal temperature loss during degassing.
  • ladle filling heights are impossible to guarantee and are dependent upon ladle refractory wear, rolling mill schedule, furnace refractory wear, furnace charge, operator control, etc.
  • a still further object of this invention is to simultaneously heat and purify molten metal.
  • this invention comprises the degassification and purification of metal, particularly molten steel, which is highly effective, takes a relatively short time, employs equipment having a relatively low capital cost and is quite simple to operate.
  • the molten metal being degassed may be heated, agitated and alloyed at the same time, if necessary or desirable.
  • purification and degassification of molten steel is effected by providing two chambers under differential pressure sufficient to cause molten steel to flow from one chamber to the other via a conduit and introducing into the con duit a purging gas, air, inert gas or reactive gases, whereby the steel melt is degassed and purified in the downstream chamber.
  • the downstream chamber is operated under vacuum such that at least part of the pressure differential is provided thereby.
  • Suitably sized heating means are provided, based on either inductive or resistance heating principles on the communicating conduit or preferably on the downstream vacuum chamber to at least offset the inherent temperature loss during degassing.
  • FIG. 1 is an elevation partially in section of an apparatus according to this invention
  • FIG. 2 is an elevation partially in section of another apparatus according to this invention.
  • FIG. 3 is an elevation partially in section of the apparatus of FIG. 2 modified to provide for metal working and/or forming after purification;
  • FIG. 4 is an elevation partially in section of another apparatus according to this invention coupled with a metal forming apparatus.
  • the conduit between the upstream and downstream chambers according to this invention is hermetically sealed to both chambers with respect to the environment of the total apparatus, and the inside thereof communicates only with these chambers and the source of purge gas.
  • the purge gas in introduced into the conduit in a part thereof, wherein molten metal is ascending into the downstream chamber, but whereat such metal is under superatmospheric pressure.
  • any change in the equilibrium between the chambers causes a flow of metal from the feed chamber to the vacuum chamber.
  • Only the purging gas is introduced within this hermetic conduit at a point where the molten metal is still under pressure, but is already in the ascending limb, that is, not at the lowest point in the communicating conduit.
  • Introduction of the purge gas at the lowest point of the conduit or in a downward leg thereof must be avoided in order to prevent the molten metal from being purged contrary to the direction of feed, thus interfering with the feed.
  • the purge gas in entering the ascending limb of the communicating conduit, reduces the specific gravity of the purge gas-molten metal mixture, so that the molten column additionally rises slightly.
  • the equilibrium of the molten metal between the two chambers is varied by exerting a superatmospheric pressure on the surface of the metal in the feed (upstream) chamber, suitably by means of a gas, while maintaining the vacuum in the vacuum chamber, and augmenting the pressure as the metal is advanced from the feed chamber to the vacuum chamber.
  • a simple adjustment in the pressure level is all that is necessary to control the metal height, portion and exposure time in the vacuum chamber.
  • This process is performed to special advantage by exerting the overpressure on the surface of the metal in the feed chamber by means of the purge gas.
  • the vacuum chamber With the conduit is immersed into the feed chamber simultaneously providing an air-tight seal between the feed chamber and the conduit or vacuum chamber.
  • the vacuum chamber is then evacuated to a vacuum of, say 0.1 torr, this value being mentioned only by way of example, without being considered critical.
  • Pressure suitably gas pressure, especially pressure provided by the purge gas, on the surface of the molten metal in the feed chamber is adjusted so that a velocity of flow is established in the ascending limb of the communicating conduit.
  • a suitable flow rate might be 1.5 m./s.
  • the speed can, of course, be increased, the important thing being only that any speed of fiow considered expedient can be set in the ascending limb of the communicating conduit by adjusting the pressure on the surface of the molten metal in the feed chamber.
  • This pressure on the surface of the molten metal in the feed chamber accordingly need not initially be a superatmospheric pressure, but may be, if desired. During the degassing operation, this pressure is superatmospheric.
  • any desired molten metal portion is forced from the feed chamber into the vacuum chamber to any desired height, a height, for instance suitable enough to energize an inductive heating coil incorporated into the chamber side walls, thereby heating the molten metal in the vacuum chamber for the length of time it is supported by the overpressure above the feed chamber metal level.
  • inductive bath stirring can be accomplished, alloy additions can be made, etc.
  • a small bath depth can be chosen, i.e., a relatively small steel portion can be forced into the feed chamber in the early stage of degassing. This might be beneficial in order to control any possible excessive outgassing and also, from the point of optimum degassing efficiency, i.e., not to limit the early gas evolution by any excessive ferrostatic pressure in the lower zones of the metal portion. Later, this portion can easily be increased for heating and/ or alloying additions, shortening of degassing time, etc.
  • This invention can also be practiced by maintaining the vacuum in the downstream chamber substantially constant and varying the equilibrium between the two chambers by drawing off some portion or all of the molten metal on the downstream side at a point where the metal is under an overpressure, with the effect that metal which is still to be purified flows from the feed chamber into the downstream chamber.
  • the drawing off of the degassed hot metal from the vacuum chamber at a point where the metal is under an overpressure is performed with the effect that fresh metal flows from the feed chamber at the rate at which degassed metal is drawn off.
  • the pressure in the vacuum chamber tends to be further reduced, which would result in an increase in the degree of vacuum in the downstream chamber. Since this vacuum in the vacuum chamber is virtually kept constant, a corresponding amount of fresh, unpurified hot metal must flow in.
  • One apparatus for the performance of the process of the invention provides a vacuum chamber which can be evacuated and placed in hermetic communication with a feed ladle which is at least under atmospheric pressure.
  • the elevation of the vacuum chamber which is hermetically sealed at the top and can be connected in its upper area with a vacuum source, is adjusted to be higher at least by the column height of the hot metal corresponding to the pressure of one atmosphere than the level of the molten metal in the feed ladle.
  • the actual height of the vacuum chamber should be at least several times the height of the column of molten metal steel portion in the vacuum chamber as supported by the overpressure in the feed chamber in order to contain the violent outgassing during the early stage of vacuum treatment.
  • Means are provided for the introduction of a purge gas under pressure into the limb of the hermetic communication conduit that ascends to the vacuum chamber at a point where the molten metal is under overpressure. Means are provided to increase the purge gas pressure on the feed chamber suflicient to overcome a situation where the vacuum chamber pressure approaches that of the feed chamber.
  • the invention apparatus comprises a feed chamber under pressure hermetically connected to a vacuum chamber through a conduit
  • the vacuum chamber should be so dimensioned that it is capable of holding at least a portion and preferably substantially all of the hot metal in the feed chamber, allowing appropriate height for outgassing of metal.
  • This apparatus is constructed, in a preferred embodiment of the invention, in such a manner that the feed ladle or chamber is movable, especially vertically, and is provided with a shoulder extending therearound which can be pressed tightly against a sealing flange of the vacuum chamber such that a hermetic connection by a skirt to the vacuum chamber is made with the purge gas compressor being connected to the skirt.
  • the feed chamber can be placed into a pit with the air-tight pressure hood connected to the vacuum chamber to seal against the pit sides and the vacuum chamber.
  • it is particularly easy to fill the feed ladle or teeming ladle with still undegassed molten metal and empty it again after performing the degassification.
  • This apparatus is constructed in a preferred embodiment of the invention to contain a suitably sized induction coil of suflicient power input and preferably net frequency in the vacuum chamber side walls to allow heating and bath stirring of said steel portion while being supported by the overpressure in the feed chamber.
  • the communicating conduit as a communicating tube with two ascending limbs and a lower middle portion connecting these two limbs together, one of the two limbs opening into the feed ladle and the other into the vacuum chamber.
  • the purge gas compressor is connected to the limbs which open into the vacuum chamber in order to introduce the purge gas into the molten metal at a point which lies below the level of the molten metal in the feed ladle at atmospheric pressure.
  • the molten metal exit out of the vacuum chamber is through an outlet which is located below the level of said feed ladle molten metal and may be controlled and shut by means of a shut-otf device.
  • a metal forming or working device can be included after the main outlet of the downstream or vacuum chamber.
  • the metal forming or working device may be, for instance, a continuous casting die or a roll mill, a tube forming die, etc. Other forming steps as required can follow in ordered sequence as shown in the art.
  • Another expedient embodiment of this invention resides in the fact that alloying components can be conveniently added to the molten metal in the vacuum chamber during the vacuum treatment, since by the intensive movement and bath agitation due to the influence of the inherent gas evolution, purge gas effect and/ or induction stirring, extremely good mixing of the added alloy components with the molten metal results which means homogeneous and segregation-free steel products.
  • the compounds which are known to be deoxidizing agents are especially considered an alloying components; ferromanganese, ferrosilicon and ferrovanadium are mentioned as examples of such agents for molten steel.
  • the invention is characterized not only by an especially effective degassing, but also by the fact that the apparatus required for the reduction of the invention to practice, especially the vacuum chambers, become extremely small. By means of the invention, it is easily possible to make several minutes available as residence time for the degassing.
  • An induction coil is preferably operatively associated with the vacuum chamber in each of the embodiments of this invention.
  • the apparatus of FIG. 1 consists substantially of a vacuum chamber 3 equipped With a metal jacket 1 and a lining 2, and a teeming ladle 4 or a feed reservoir 35.
  • the vacuum chamber 3 is equipped in its lower portion with a hermetic skirt made, for example, of steel plate, which has a marginal seal 6 on its periphery and radially overlaps the teeming ladle 4.
  • the teeming ladle 4 is mounted on a lift platform 7 and can be pressed by the latter with its marginal thickening 8 against the marginal seal 6 of the skirt 5, thereby producing a hermetic seal between the vacuum chamber 3 and the teeming ladle 4.
  • the vacuum chamber 3 has in the vicinity of its bottom portion 9 a tubular suction nozzle 11 extending close to the floor of the teeming ladle, the said nozzle having brickwork 12 and an aspirating passage 13 extending through its entire length. There are openings 14 in the suction nozzle 11 in the bottom area facing the teeming ladle floor 10.
  • the teeming ladle 4 is provided with brickwork 15, and trunnions 17-17 are provided on its jacket 16, the said trunnions being engageable by transporting and tipping apparatus which are not shown.
  • a passage 18 which is connected to a blower or compressor 19 in order to feed purge gas at elevated pressure, and a valve 20 for regulating the purge gas pressure.
  • a passage 23 connecting it to a vacuum source, such as a vacuum pump or a diffusion pump, and a shut-off device 24 is provided in the said passage.
  • the teeming ladle 4 which is normally filling up to the line 0-0, is pressed by means of the platform lift 7 With its marginal thickening 8 against the seal 6 matching the marginal thickening, thereby producing a hermetic seal and hence a pressure chamber 26 between the vacuum chamber 3 and the radially flaring skirt 5. With valve 20 closed, the vacuum source 22 communicating through passage 23 with the vacuum chamber is started up, and the interior of vacuum chamber 3 is evacuated to, for example, 0.01 torr by opening the shut-off valve 24.
  • the atmospheric pressure enclosed in pressure chamber 26- produces a pressure equalization in such a manner that molten metal flows through the bottom opening 27 in the suction nozzle 11, through its suction passage 13 and opening 27 in the bottom 9, into the interior of the vacuum chamber, until a complete pressure equalization is brought about between the molten metal column H, including the vacuum in the vacuum chamber, and the pressure present in the compression chamber 26.
  • the new level of molten metal in the teeming ladle is designated as 29, while the new level that is simultaneously produced in the vacuum chamber bears the reference number 30. Then, as a result of the evacuation of the interior of the vacuum chamber above the molten metal, gas is evolved from the molten metal.
  • valve 20 is opened and purge gas is pumped into pressure chamber 26 under elevated pressure by means of a compressor 19.
  • pressure builds up in the :pressure chamber 26
  • additional molten metal is forced through passage 13 of suction nozzle 12 into the vacuum chamber 3.
  • passages 14 in the bottom half of the suction nozzle become exposed.
  • Purge gas then flows from the pressure chamber 26 through openings 14 into the molten metal in the passage 13 of the suction nozzle 11 and causes the metal to be thoroughly agitated.
  • the passages 14 have only a small and limited cross section.
  • the amount of purge gas that enters into the molten metal is continuously exhausted by the vacuum source 22 connected to passage 23, although the vacuum source substantially maintains the vacuum in the vacuum chamber 3.
  • the purge gas pressure in the pressure chamber 26 must in this phase be proportional to a column height corresponding to H1, the level of the molten metal in the vacuum chamber being designated as 31.
  • Metal circulation for repeated exposure to vacuum can preferably be effected by reducing the purge gas pressure in the pressure chamber 26, causing the metal portion in the feed chamber 3 to return to the teeming ladle 4 via passageway 13, for instance, from a level 31 to 30. It is also possible that during the final phase of the process purge gas also flows through the entrance 27 of the suction passage 13 of the suction nozzle, and thus leads to a reduction of the vacuum in that portion of the interior of vacuum chamber 3 which is not filled with molten metal, resulting in a limited backflow of the metal until the entry- Way 27 of suction passage 13 is closed.
  • the evacuation of the vacuum chamber interior which is again performed by the vacuum pump results in a repeated pumping of the metal into the vacuum chamber, resulting in an effective agitation of the metal, and the above-described process is intensified.
  • This process could be continued for any desired length of time, provided that the metal is maintained in the molten condition.
  • the molten condition may be maintained by heating, especially by inductive heating which is preferred.
  • the openings 14 for the introduction of the purge gas into the molten metal are thus located in an area in which the metal is under an overpressure.
  • the evacuating of the vacuum chamber 3 and the pressurizing of the pressure chamber 26 are regulated by means of valves 20 and 24 of the vacuum source 22 and compressor 19 in such a manner that a velocity of flow of the metal is not too high for the brickwork.
  • the cross section of the vacuum chamber 3 is, in a prior-art manner, substantially greater than that of the suction passage 13. Since the pressure in the pressure chamber 26 and hence the height M1 of the molten metal can be made as great as desired, the cross section in both the teeming ladle 4 and the vacuum chamber 3 can be very small.
  • the embodiment of the apparatus according to FIG. 2 serves for the continuous performance of the degassing and refining process of the invention.
  • the apparatus consists substantially of a vacuum chamber 32, a feeding system 33 and a drawing-off system 34.
  • the vacuum chamber 32 is substantially similar in construction to the Vacuum chamber 3 of FIG. 1.
  • the feeding system consists of a feeding or reservoir ladle and a tube 33 for feeding the molten metal to be refined from the reservoir ladle 35 to the vacuum chamber 32.
  • the feed tube 33 is constructed in a U-shape in the manner of a communicating tube, and consists of two limbs 33a and 330, each of which is open at the top, and a substantially horizontally disposed middle portion 33b.
  • Limb 33c empties at opening 33d in the bottom third of the vacuum chamber 32 at about the same height as that of the conduit opening into the reservoir ladle 35.
  • the connecting passage 33 is equipped in the area of its horizontally disposed middle portion 33b with an outlet 36 which can be shut off by means of a shut-off member 37, 37a.
  • a shut-off member 38, 39, is disposed in the reservoir 35 for the interruption of the continuous feeding of molten metal.
  • the drawing-off system 34 consists substantially of an outlet opening 43 below the bottom 40 of the vacuum chamber 32, which merges into a pouring passage 34a and an extension passage 34b running substantially horizontally, with an outlet opening 340, which can be closed by a shut-elf member 41, and which empties into a pouring spout 42.
  • An opening 43 provided in the bottom 40 of the vacuum chamber 32 is connected by a downwardly slanting pouring passage 34d to the outlet opening 44, which can be closed by means of a shut-ofi member 45 to interrupt the flow of molten metal which normally flows continuously from the vacuum chamber.
  • the pouring passage 34a extending to the outlet opening equipped with the shut-off member 45 is disposed below the outlet opening 330!
  • connection passage 33 which serves as a communicating tube to connect the reservoir ladle 35 to the vacuum chamber 32 and extends downward slantingly from its inlet opening 43 to the outlet opening 44.
  • the pouring spouts 42 on the extension passage 34b are likewise equipped with shutoff members (not shown) and can be connected hermetically to chill moulds 47 which can be moved by platform lifts 46. Tubes 48 can be disposed on the moulds 47 to provide a connection to vacuum sources through shut-01f valves. A teeming ladle 49 is located underneath the outlet opening 341:.
  • the molten metal runs through the connecting passage 33 into the lower area of the vacuum chamber 32.
  • a position of equilibrium will establish itself in the U-shaped passage 33, corresponding approximately to the line OO. If, in the same manner in FIG. 1, the interior of the vacuum chamber 32 is evacuated through a vacuum line 51 connected to a vacuum source, a pressure differential develops between the interior of the vacuum chamber 32 and the reservoir ladle 35 which is under atmospheric pressure, thus causing additional molten metal to be forced out of the reservoir ladle 35 into the vacuum chamber to the level 52.
  • the column height (H3) of molten steel forced into the vacuum chamber will amount to about 1.45 m.
  • the equilibrium line OO is expediently located at a height (H-2) which is higher than or equal to about 1.6 m. above the horizontally disposed middle portion 33b of the feed passage 33.
  • the shut-off member of the pouring passage 34, and also the opening 43 in the bottom 40 of vacuum chamber are disposed lower than the equilibrium line OO. If the shut-off member 45 located lower by the column height (H-4) than the equilibrium line O--O is opened, the refined and degassed molten metal flows along the line indicated by the arrows in FIG.
  • the chill moulds can be evacuated through the vacuum line 48.
  • a purge gas is fed through conduits 53, which conduits are of limited cross section, to the molten metal flowing from the reservoir ladle 35 to the vacuum chamber in the ascending limb 330 of the connecting passage 33 and in the area of column height H2 in which the molten metal is under overpressure, the said conduits being connected to a compressor 54 through a passage 56 that can be shutofi by means of a shut-off valve 55.
  • the degassing and refining process to be performed with the apparatus of FIG. 2 can expediently take place continuously.
  • the reservoir ladle 35 can be supplied from one or a plurality of Bessemer, open-hearth and other furnaces.
  • the process can be set up in such a manner that the degassing of a heat can be performed in the interval between two furnace heats. Interruptions of the continuous process are made possible by means of the shut-off devices 39 and 45.
  • the untreated molten metal fed to the vacuum chamber through passage 33 first flows upwards in the vacuum chamber, then turns about in the vicinity of the surface 52 of the metal and flows downward, whereupon its still undegassed part is turned about and driven back upward by the molten metal emerging from the opening 33d.
  • the degassed part of the hot metal flows through the opening 43 and passage 34 to the outlet opening 44 which is opened more or less widely by means of the shutoff device 45.
  • the degassed part of the molten metal has a greater specific gravity than the non-degassed part, and this promotes the above-described flow. All of the molten metal is thus carried into the upper area near the surface and kept constantly in movement. Therefore, an elfective degassing and purification of all of the metal is performed, and the degassing is not hampered due to appreciable ferrostatic pressure on the bottom portion of the hot metal.
  • the feeding in of purge gas improves the effectiveness of the process of the invention and accelerates it.
  • the installation described with reference to FIG. 2 is set in operation by pouring the molten metal into the feed chamber while the vacuum chamber is still not under a vacuum. If the shut-oft device 39 is opened, the molten metal then stands in the limbs of the communicating tube at the height H-2 in FIG. 2, that is, at height zero. Now the vacuum pump 50 is turned on, causing the molten metal in the vacuum chamber to rise to the height H3. The purge gas is fed in at about the same time that the vacuum pump is turned on. Then such amount of molten metal which is resident in the vacuum chamber is degassed and treated. The vacuum pump 50 or the dilfusion pump draws out the purge gas that is pumped in, while maintaining the vacuum constant.
  • the tapping valve is opened so that the speed of flow of, for example 1.5 rn./sec., if that is considered proper, is again established in the acsending limb of the communicating tube.
  • the molten metal now flows continuously through the apparatus at the stated velocity, While it is continuously purged and degassed.
  • the column height H-3 of the molten metal, plus the small pressure head corresponding to the overpressure in the vacuum chamber 32, is therefore equal to the gas pressure exerted on the surface of the molten metal in the reservoir ladle. If this gas pressure is equal to the atmospheric pressure, H3 is approximately equal to 1.45 m. in the case of molten steel. It is, however, also possible according to the invention to apply an overpressure to the molten metal in reservoir ladle 35 by means of a gas. The column height H3 is then correspondingly higher.
  • the molten metal is under a pressure which is greater by the column height than the pressure which the molten metal has on line OO. So, if the molten metal is under atmospheric pressure on this line, it is under an overpressure below the line 0-0. In the case of a molten steel with H-ZZabout 1.4 m., an overpressure will therefore prevail in the horizontal portion 33b of something over 1 atmosphere.
  • both the outlet opening 44 with the pouring passage 34 of the vacuum chamber 32 and the openings 53 for the introduction of the purge gas must be located. Heights (H2) of at least about 1.5 m. for a steel bath and corresponding heights for other materials having different specific gravities are preferred for reasons of safety. Such column height could be lower, but in any event should always be greater than the equivalent of about one atmosphere.
  • an outlet opening 37 which can be closed by means of a blocking means 37a, which outlet opening empties into an outlet spout 36.
  • the outlet opening 37 is provided in order to drop the molten metal into a reservoir ladle 35 whenever the degassing process is to be interrupted.
  • the molten metal in the passage 33 and the ladle 35 can also be forced to the outlet opening 44 by means of a gas overpressure acting on the molten metal in the ladle 35.
  • a hopper 58 empties into the upper part of the vacuum chamber 32 through a conduit 59 into which a shut-off valve is inserted.
  • the hopper 58 can be filled through a shut-off device 61 with any desired alloy components, deoxidants or other additives. After cover 61 has been closed and the valve 60 has been opened, the alloy components, deoxidants or other additives enter into the molten metal and are there intensively mixed with the molten metal by the intensive movement of the latter and the bubbling gas passing therethrough.
  • the alloying components or deoxidants of the embodiment in FIG. 1 can be fed in as a single batch for the entire volume of the heat.
  • the hopper and the corresponding apparatus for the addition of the alloy components, deoxidants or other additives have been omitted for the sake of simplic ity.
  • the resistances in the passages 33, 34 and 42 and in the valves 39 and 45 must be taken into account with reference to the speed at which the molten metal issues from the opening, in such a manner that the velocity of flow of the metal in the connecting passage 33 will not exceed the desired velocity of flow of, for example 1.5 m./ sec.
  • the embodiment in FIG. 3 differs only in certain details from the embodiment in FIG. 2, so that the same reference numbers have been used for the same parts, and the description of the embodiment in FIG. 3 can be limited to the differences in comparison with FIG. 2.
  • the column heights H-5, H-6 and H7 of FIG. 3 correspond to the column heights H3, H-2 and H4 of FIG. 2.
  • passages 53 are provided which are connected through a conduit 56 equipped with a shut-off member 55 to a compressor 54 for pumping purge gas into the connecting passage 33.
  • heating systems 62-63 are provided, which may be supplied from a common, centrally located heating source 64 or may be heated individually, and heat the molten metal in passage 33.
  • the heating devices can be constructed especially as resistance heating systems or inductive heating systems. But other heating methods can easily be used, such as heating by the combustion of a combustible material, especially a combustible gas, or heating by means of a previously heated fluid.
  • the embodiment of the apparatus for the performance of the process of the invention as shown in FIG. 3 differs from the embodiment of FIG. 2 mainly in the area of tapping system '65.
  • a die 66 At the end of the tapping passage 65a there is disposed a die 66 through which the emerging metal can be cast into a strand of any desired shape.
  • a cooling chamber 6767a which is provided with a feed conduit 68 and a discharge conduit 69 for carrying a coolant.
  • the strand of material cast in the die 66 is cooled in the cooling chamber to a hot-forming or even cold-forming temperature.
  • a liquid such as water or a gas such as air is passed through the cooling chamber.
  • the strand of metal can be covered by shielding gas in the cooling chamber area.
  • a synchronously driven set of forming rolls 70 which seize the strand of metal emerging from the cooling chamber and subject it to a forming treatment.
  • a shut-ofi? device is located ahead of the die 66.
  • this shut-oif device serves mainly for the purpose of initiating the degassing and refining process in accordance with the above description.
  • the function of the shut-off device is the same as that of. the shut-off device 45.
  • the shut-off device 71 is opened as in the case of the embodiment in FIG. 3.
  • the task, however, of regulating the flow of the molten metal from the vacuum chamber 32 according to the velocity of flow of the metal in the connecting passage 33 is then substantially taken over by the die 66.
  • the cross section of the die (which determines its resistance to flow) is to be made such that the velocity of flow produced in the connecting passage 33 in no case exceeds the maximum speed that is recognized as being correct in each case.
  • the shielding gas enters the interior of the cooling chamber 72 directly behind the die 66 through a passage 73, after it has been compressed by means of a compressor 74. In this manner, the shielding gas can enter the chamber 72 through a distributing ring 75, in order to assure a distribution that is as uniform as possible on the inner periphery of the cooling chamber 72.
  • the shielding gas leaves the chamber 72 at a point 76 together with the strand 77. Accordingly, as it leaves the die, the strand is under the influence of an overpressure which the shielding gas has at this point. Under these circumstances, it is possible to influence the speed at which the molten metal is forced through the die 66, by varying the overpressure of the shielding gas.
  • the two rollers are driven substantially synchronously, in accordance with the speed at which the molten metal is forced through the die, that is, at which the strand 77 is shaped.
  • This strand is cooled by means of the cooling chamber 67-72 in the embodiment in FIG. 3 only to a temperature that is considered proper for the following process of shaping by means of the rollers 70.
  • the temperature may be a hot-forming temperature or a cold-forming temperature.
  • the pressure with which the molten metal is forced through the die 66 is determined by the height H-7 in FIG. 3. In other words, it is easily possible, by adjusting the setting of the die 66 with relation to the equilibrium line OO, to force the molten metal through the die with any desired pressure; the lower the discharge point, the greater the pressure.
  • the shielding gas can additionally be used for the cooling of the continuous casting die and of the strand 77 emerging from the said die.
  • FIG. 4 represents a variation of the continuous casting and forming system of FIG. 3.
  • This apparatus too, operates in conjunction with a degassing and refining installation according to the invention, as shown in FIG. 2 or FIG. 3.
  • This embodiment shows the combination of the invention of a continuous casting system for pipes, which are cast directly from the vacuum chamber by the falling weight of the molten metal.
  • the tool system in FIG. 4 consists of a continuous casting die 79 and a continuous casting mandrel 80.
  • the mandrel is provided with a tapered projection 81 and forms with the die 79 an annular gap 82 which is adjustable for gap size.
  • the mandrel is also equipped with a toothed rack 83 which engages'a pinion 84 that can be driven in both directions for the purpose of axial displacement of the mandrel 80. In this manner, the size of the annular gap 82 and thus the rate of flow of the molten metal can be regulated.
  • the continuous casting mandrel is furthermore provided with a bore 85 extending substantially over its entire length, and is provided beyond the tapered projection with cross holes 86.
  • the inner periphery of the tubular casting is swept with shielding gas for the prevention of oxidation, through the bore 85 and the holes 86, the gas having been fed through a conduit 87 after such has been put under pressure by a compressor 88.
  • the diameter of the continuous casting mandrel is reduced in the area of the holes 86, as shown at 89, to form an annular cross section for the passage of the shielding gas.
  • the mandrel is bedded in a matching mounting 90 made of fireproof material.
  • the casting 91 is surrounded on a portion of its length by a cooling chamber 92 which has an inlet 93 and an outlet 94 for the coolant.
  • the cooling chamber 92 is fed with a liquid, especially water, or with a coolant gas.
  • a shielding gas which has been compressed by a compressor 88 is fed through the conduit 95.
  • the shielding gas enters at a point 96 which lies approximately in the area where the first radial openings 86 are located. It leaves at point 97 from a chamber 98 which surrounds the tubular strand 91 while forming a gap 99 required for the passage of the shielding gas.
  • the chamber 98 can simultaneously be constructed as the inside wall of a casing 100 which forms the cooling chamber 92.
  • the tapered projection 81 of the casting mandrel 80 forms a conical valve body capable of cooperating with a matchingly conical valve seat 82 which is formed by the side of the die 79 that faces leftward in FIG. 4.
  • the conical valve body 81 is moved rightward in FIG. 4 onto the conical seat 82.
  • the valve is opened when the mandrel 80 is moved leftward in FIG. 4 along with the conical valve projection 81.
  • the process of refining the molten metal and of forming a pipe can then be performed continuously.
  • the heating devices 62 and 63 described with reference to FIG. 3 are particularly expedient for the purpose of keeping the metal liquid if the continuous drawing off of the metal from the vacuum chamber is interrupted. Such interruptions result, for example, as rigging times, when subsequently to the degassing in the vacuum chamber the molten metal is formed into strands or pipes.
  • the continuous casting mandrel could also be disposed fixedly. Owing to the fact that, in the embodiment according to FIG. 4, the casting die has been made axially displaceable, it is simultaneously capable of serving as a shut-off device by means of the conical projection'sl. If a fixed continuous casting die were provided by the fixed arrangement of the continuous casting mandrel, a separate shut-off device would be additionally provided, corresponding to the shutoff device 71 of the embodiment in FIG. 3.
  • the contents of the vacuum chamber 3 or 32 amount to 1,000 kg. for a drop of 1.6 m.
  • the inside diameter of the vacuum chamber 3 or 32 amounts to only about 0.33 m. If We take the thickness of the brickwork as being 0.15 m., the result is an outside diameter of 0.65 m. for the vacuum chamber.
  • the sealing of a vacuum chamber of such small diameter and the fastening of the brickwork in such a small vacuum chamber are extremely simple. This output, which in itself is quite large, can be still further augmented by increasing the volume of the vacuum chamber, that is, by increasing its diameter, or also by accelerating the through-flow by increasing the height H-4 in FIG. 2 and H7 in "FIG. 3, while correspondingly enlarging the cross-section of the communicating passage 33.
  • FIGS. 2 to 4 of the apparatus for the performance of the continuous degassing and refining process of the invention can all be used for the degassing and refinement of the molten metals from a plurality of furnaces.
  • Gases such as air, active and/or neutral, are used in a prior-art manner as the purge gas in the process according to the invention.
  • induction coil 1a operatively associated with the vacuum chamber of each embodiment. While the presence of this coil is preferred, it may be dispensed with where short duration degassification is to be accomplished.
  • the special advantage of the process of the invention consists, in addition to the better and more rapid degassing and refinement of the molten metal and the ability to heat during such vacuum treatment, in the capability of the process to run continuously or, in case of the embodiment in FIG. 1, semi-continuously, to be independent from the height of the barometric column by using overpressure for material transport, and in the considerable reduction in the size and'cost" of theapparatus for the performance of this process.
  • Non-metallic raw materials can also be degassed or reduced, as the case may be, and alloyed in this manner.
  • Apparatus for treating molten metal comprising first vessel means for vacuum treating molten metal, second vessel means for containingmolten metal therein, means for relatively moving said vessels into and out of an operative position, conduit means aifixed to, and extending downwardly from said first vessel meansand having one end constructed and arranged to be disposed below the level of molten metal in said second vessel means when said vessels are in an operative position to seal said first vessel means, means on one of said vessel means for sealing said second vessel means when said vessel means are in their operative position, first means coupled to said first vessel means for subjecting said first vessel means to sub-atmospheric pressure sufiicient to draw a quantity of said molten metal through said conduit means into said first vessel means, and second means coupled to said second vessel means for introducing a gas under a pressure greater than atmospheric pressure to said second vessel means so that the amount of molten metal drawn into said first vessel means is greater than that quantity therein resulting from said sub-atmospheric pressure alone.
  • additive feeding means is constructed and arranged to selectively discharge additives into said first vessel means.
  • conduit means has at least one passage formed therethrough and intermediate its ends for allowing the passage of gas from said second vessel means into the interior of said conduit means to create a gas lift for said molten metal.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US538296A 1965-04-02 1966-03-29 Apparatus for the purification of molten metal Expired - Lifetime US3508743A (en)

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CH461765A CH436362A (de) 1965-04-02 1965-04-02 Verfahren zum Reinigen von Metall-, insbesondere Stahl-Schmelzen und zum Vergiessen derartiger Schmelzen und Vorrichtung zur Ausführung des Verfahrens

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Cited By (5)

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Publication number Priority date Publication date Assignee Title
US4452634A (en) * 1982-07-20 1984-06-05 Kawasaki Steel Corporation Method of stirring molten metal and refractory cylinder for the purpose
GB2234261A (en) * 1989-07-26 1991-01-30 British Steel Plc Vaccuum transfer of molten metal
WO1996027683A1 (en) * 1995-03-07 1996-09-12 Bethlehem Steel Corporation Apparatus and method for vacuum treating molten steel in a barrel degasser
CN103981336A (zh) * 2014-05-24 2014-08-13 北京首钢国际工程技术有限公司 一种真空室下出形式的rh工艺布置方法
CN106480257A (zh) * 2015-08-29 2017-03-08 党祎贤 泵阀真空除气装置

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US3798025A (en) * 1971-12-29 1974-03-19 Allegheny Ludlum Ind Inc Vacuum decarburization in rh and dh type degassing systems
JPS5110102A (en) * 1974-07-15 1976-01-27 Sumitomo Metal Ind Dh oyobi rh shinkudatsugasuho
IT1104455B (it) * 1978-09-05 1985-10-21 Piombino Acciaierie Materozza per lingottiera di colata continua
SE430662B (sv) * 1982-03-11 1983-12-05 Korshunov Evgeny Forfarande for strenggjutning av metall
LU84093A1 (de) * 1982-04-16 1983-12-16 Arbed Einrichtung zum metallurgischen behandeln von fluessigen metallen
KR850000928B1 (ko) * 1982-04-23 1985-06-28 신메이 엔지니어링 가부시끼가이샤 용융금속의 교반장치
DE8701910U1 (de) * 1987-02-09 1987-05-27 Kreitl, Detlef, 8046 Garching Schleifscheiben-Abrichtgerät
WO1991019013A1 (fr) * 1990-05-31 1991-12-12 Nippon Steel Corporation Procede de raffinage pour metaux ou alliages en fusion
DE4325432A1 (de) * 1993-07-29 1995-02-02 Abb Patent Gmbh Regelsystem für eine Waagerecht-Strangguß-Anlage mit einem als Druckkammer ausgebildeten Warmhaltegefäß
DE102007016018A1 (de) * 2007-04-03 2008-10-09 Sms Demag Ag Brenneranordnung

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US2140607A (en) * 1935-10-19 1938-12-20 American Metal Co Ltd Method of and apparatus for casting deoxidized copper
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US598037A (en) * 1898-01-25 Machine for exhausting molten metal
US1921060A (en) * 1931-03-23 1933-08-08 Clyde E Williams Method of purifying metals
US2140607A (en) * 1935-10-19 1938-12-20 American Metal Co Ltd Method of and apparatus for casting deoxidized copper
US2997756A (en) * 1956-07-17 1961-08-29 Griffin Wheel Co Method and apparatus for casting ingots
FR1224375A (fr) * 1958-03-10 1960-06-23 Hoerder Huettenunion Ag Installation de dégazage des coulées d'acier
US3116999A (en) * 1960-03-12 1964-01-07 Heraeus Gmbh W C Method and apparatus for degassing liquids in a vacuum
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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4452634A (en) * 1982-07-20 1984-06-05 Kawasaki Steel Corporation Method of stirring molten metal and refractory cylinder for the purpose
GB2234261A (en) * 1989-07-26 1991-01-30 British Steel Plc Vaccuum transfer of molten metal
GB2234261B (en) * 1989-07-26 1993-09-22 British Steel Plc Liquid metal processing
WO1996027683A1 (en) * 1995-03-07 1996-09-12 Bethlehem Steel Corporation Apparatus and method for vacuum treating molten steel in a barrel degasser
US5603749A (en) * 1995-03-07 1997-02-18 Bethlehem Steel Corporation Apparatus and method for vacuum treating molten steel
CN103981336A (zh) * 2014-05-24 2014-08-13 北京首钢国际工程技术有限公司 一种真空室下出形式的rh工艺布置方法
CN106480257A (zh) * 2015-08-29 2017-03-08 党祎贤 泵阀真空除气装置
CN106480257B (zh) * 2015-08-29 2018-05-22 党祎贤 泵阀真空除气装置

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CH436362A (de) 1967-05-31
US3606293A (en) 1971-09-20
DE1783113A1 (de) 1971-05-06
DE1508166B1 (de) 1970-06-18
GB1113827A (en) 1968-05-15
DE1508166C2 (de) 1973-01-04

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