US3062523A

US3062523A - System for degassing steel

Info

Publication number: US3062523A
Application number: US836167A
Authority: US
Inventors: Knuppel Helmut
Original assignee: Dortmund Hoerder Huettenunion AG
Current assignee: Dortmund Hoerder Huettenunion AG
Priority date: 1958-09-11
Filing date: 1959-08-26
Publication date: 1962-11-06
Anticipated expiration: 1979-11-06
Also published as: NL243177A; FR1234646A; GB896974A

Description

Nov. 6, 1962 H. KNUPPEL SYSTEM FOR DEGASSING STEEL 4 Sheets-Sheet 1 Filed Aug. 26, 1959 .IIIIIIIII Nov. 6, 1962 H. KNUPPEL SYSTEM FOR DEGASSING STEEL 4 Sheets-Sheet 2 Filed Aug. 26, 1959 w/ my 8 s .9 Jr r m u r M A l E. H

Nov. 6, 1962 H. KNUPPEL SYSTEM FOR DEGASSING STEEL 4 Sheets-Sheet 5 Filed Aug. 26, 1959 m t B Jnvgnfor: A l-lElMUT lf/W/PPEL Nov. 6, 1962 H. KNUPPEL 3,062,523

SYSTEM FOR DEGASSING STEEL Filed Aug. 26, 1959 4 Sheets-Sheet 4 Jn venfor:

/ Maw United States Patent 3,062,523 SYSTEM FOR DEGASSING STEEL Helmut Kniippel, Dortmund-Lottringhausen, Germany,

assignor to Dortmund-Herder Huttenunion Alrtiengesellschaft, Dortmund, Germany Filed Aug. 26, 1959, Ser. No. 836,167 Claims priority, application Germany Sept. 11, 1958 13 Claims. (Cl. 266-34) For degassing molten steel on a large industrial scale, essentially two different processes are used. In one, the molten steel is poured into an evacuated vessel, becomes dispersed therein in fine droplets, and is then received by a ladle or mold. In the other, portions of a quantity of steel in a ladle are transferred to a degassing vessel arranged above the ladle, where they are degassed under vacuum and then returned to the ladle.

The latter process, to which alone the invention relates, may be carried on continuously or intermittently. In the intermittent method, portions of molten steel are transferred from the ladle into the degassing vessel through a nipple and, after vacuum treatment, returned to the ladle by the same route. In the continuous method, a degassing vessel with two nipples is used. Suitable means are provided, such as a stream of gas generating dynamic lift inside one of the nipples, to ensure continuous flow of the molten metal from the ladle through the degassing vessel and back into the ladle.

For degassing steel by the intermittent method, the suction may be varied for the purpose of continually repeated charging and discharging of the degassing vessel. Preferably, however, the periodic charging and discharging is accomplished by variation of the vertical distance between ladle and degassing vessel. This may be achieved by vertical movement of the degassing vessel or the ladle or both.

To carry out the continuous and the discontinuous process in practice, two separate handling operations are required. Thus the ladle filled with steel to be degassed must always first be placed on a truck by the crane, and then transported underneath the degassing vessel; for the degassing vessel would obstruct the crane in an attempt to deposit the ladle in place. This twofold handling is wasteful of time and space.

One object of the invention is to make one handling operation suffice, and dispense with transportation of the ladle on a car or truck. This problem is solved by rendering the vessel laterally extensible. How this may be accomplished in detail will be explained below.

The lateral extensibility of the degassing vessel enables the crane to deposit the ladle at and withdraw it from the actual point of operation. Any haulage of the ladle is eliminated. After deposit, the degassing vessel is returned to operating position, and the nipple or pair of nipples is dipped into the melt as usual by vertical movement of the vessel or ladle. Elimination of the car or truck is not merely a simplification; it also disposes of a hazardous condition. Whereas heretofore the occurrence of a stopper leak necessitated removal of the ladle from under the unit by means of the vehicle, exposing the latter to damage by the molten steel, according to the invention the degassing system is simply retracted and the ladle picked up by the crane.

The lateral retractability of the degassing vessel may readily be achieved, for example, by pivoting the vessel on at least one horizontal axis. This pivotability on a horizontal axis will then afford advantages and opportunities quite independent of the simplified handling, and realized even if the retractability is not carried to the extent where it simplifies handling.

In the first place, the pivot feature makes it possible to set the vessel obliquely and thus provide space on the inclined bottom where alloy components may be melted in prior to the vacuum treatment. In an unpivoted degassing vessel, such space could be provided only by means of a weir on the bottom surface, and then it could not be discharged through the main nipple.

When, in the intermittent process, periodic charging and discharging are accomplished solely by rhythmically varying the vertical distance between ladle and degassing vessel, the quantity of steel entering or leaving in each instance is limited by the barometric head of the steel, which depends on the vacuum and averages only 1.40 meters. It is hardly possible to treat more than about ,4; of the contents of the ladle at a time in this way. But quite substantially larger quantities are arrived at if, instead of varying the vertical distance between ladle and vessel, the vessel is swung about a horizontal axis. Respecting the arrangement of the axis and the geometrical conformation of the interior of the vessel, a great many different procedures are possible. The vessel may be symmetrical with respect to the nipple, and likewise with respect to the axis. Nor need its motion be a pure rotation; rather, it may be composed of a rotation about a horizontal axis and a translation. Anyone skilled in the art may easily devise numerous variants of this idea.

In the preferred embodiment of the invention, whether for the purpose of simplifying handling, fusing of alloy constituents, or timing of degassing movements, or combinations of these, the degassing vessel is suspended in a linkage or system of levers. Such suspension of the degassing vessel aiiords special advantages in relation to the admission of heating currents, the connection of suction lines, and the supply of compressed air and water for cooling purposes as required. In other types of suspension, such lines must usually be movably arranged in the form of trailing lines. But if the vessel is suspended in a system of levers or linkage, all distances between individual points of rotation may be kept constant, and at the pivots themselves, only limited rotations will occur, generally of less than This results in a substantial simplification of heating, vacuum, compressed air and cooling water piping.

The device according to the invention will now be more fully described with reference to the accompanying drawings, but it should be understood that these are given by way of illustration and not of limitation and that many changes in the details may be made without departing from the spirit of the invention.

In the drawings:

FIG. I, in simplified schematic form, illustrates an embodiment of the invention.

FIG. 2 similarly illustrates another embodiment of the invention.

FIG. 3 similarly illustrates a variant form of degassing vessel.

FIG. 4 similarly illustrates still another embodiment of the invention.

In all embodiments, 10 is the ladle, 11 the evacuable and preferably electrically heated degassing vessel, and 12 a nipple of the degassing vessel, dipping into the molten metal in the ladle 10. All the embodiments described pertain to the intermittent degassing method referred to in the preamble.

In the embodiment of FIG. 1, the vessel 11 is suspended by articulations 13 and 14 from a lever 15 and a guide rod 16, rotatably mounted by fixed pivots 17 and 18 to a trestle 19. The short arm 20 of the lever 15 is engaged by a pulling means purchasing on a fixed point 21, which may consist of a block and tackle or, as illustrated, a hydraulic cylinder. With the aid of this suspension, the vessel 11 may be brought from the operative position indicated by solid lines into the position shown dotted. In this position, space is provided for a crane bringing up apes 3 or removing the ladle ill. Whether the portions to be successively degassed are charged and discharged by periodic variation of the suction in the vessel or by variation of the vertical distance between vessel 11 and ladle it is in principle immaterial. If the latter possibility is chosen, then it is expedient to employ the actuating force acting at point 22 on arm 24 of lever in order to provide the necessary vertical thrust for raising and lowering the vessel 11, rather than a vertically movable platform for the ladle 10.

In the embodiment of FIG. 2, the degassing vessel lift is pivoted on the horizontal axis 23 of a pair of articulations. The articulations 23- form one end of a pair of levers 24 which, much as in PEG. 1, are mounted on a fixed center 25 upon a trestle 25. The short arm 27 f the lever is engaged in an articulation 28 by a hy system supported at 29 on a base 36 and composed of cylinders 31 and pistons 32. With the aid of the hydraulic axis of swing of the vessel 11 can be moved along circular path about point 2.5 as center. At 33, the v'ess t 11 is engaged by the piston 34 of a hydraulic cylinder 35 articulated at 36 to the trestle 126. With the aid of as assumed in swinging about the axis of rotation may be adjusted at will.

It will be obvious that by means of the suspension and mechanisms shown, the vessel 11, much as in FIG. 1, may be brought into a position permitting direct crane handling of the ladle N. In addition, the pivoting about axis 23 in conjunction with the hydraulic system 3%, makes it possible before commencing evacuation to bring the vessel into the inclined position shown and to fuse alloy components that are to be added to the steel to be degassed in the corner space 37 formed by the inclined floor and wall surfaces. This advantage would remain even if the suspension and hydraulic mechanisms were so restricted that direct handling of the ladle It? by means of a crane would not be possible.

In FIG. 2, the suspension and mechanisms, much as in FIG. I, may be utilized to vary the vertical distance between ladle 10 and vessel 11 and thereby convey the portion subjected to degassing in each instance into the vessel 11 and out again. With vessel 11 in vertical position, this may be done with

mechanism

31, 32 alone, or in other words by a motion such as the vessel II. in FIG. l is executing. However, it is possible for this purpose to make use partially or entirely of the swinging motion provided by mechanism 34, 35. But this alternative and the advantages it sometimes afiords will be explained with reference to the embodiment of FIG. 3, where the kinematic relationships have been chosen so as to bring out these advantages with especial clarity.

The suspension and mechanical means in FIG. 3 are essentially the same as in FIG. 2. Accordingly, the vessel 11 is pivoted on the axis 3%; of two articulations at one end of lever 39, rotatably mounted at 40 on a trestle 41. The short arm 42 of lever 39 is engaged at 43 by a hydraulic mechanism consisting of piston 44 and cylinder 45, and supported at a pivot 46 on trestle 41. The angular position of vessel 11 in rotation about the axis 38 is determined by an additional hydraulic piston .7 and cylinder 48, articulated to vessel 11 and trestle ll at 49 and 50.

By means of the suspension and mechanisms shown, the vessel 11, just as in FIG. 1, may be laterally retracted sufficiently to allow a crane to deposit the ladle It at the point of operation. Similarly, it is apparent that in the embodiment of FIG. 3, also, by suitable inclination of the degassing vessel, a space can be provided for fusing alloy material, as was explained with reference to FIG. 2.

The chief purpose of the illustration of FIG. 3 is to show that the vessel, with the aid of its suspension and associated drive members, by means of a motion consisting essentially of a rotation and a small vertical displacement superimposed upon it, may be moved between two extreme positions in one of which, indicated by solid lines, it will take up an extraordinarily ample quantity of steel, and in the other of which positions, shown dotted, it is nearly empty. The level of molten metal in each position is clearly indicated by the dimensions marked Ah.

Fit 3, a shape of degassing vessel has been chosen in which the point where the nipple 12 opens into the degassing chamber is virtually the high point of the floor of vessel Ill in one extreme position. Such a design of the vessel is expedient, but not essential, in order to secure the effect obtainable, withrespect to volume of charge, by a swinging motion rather than simple raising and lowering.

Tie advantages of the invention in all its embodiments include the absence of any sort of hoisting gear above the degassing vessel, for which there is often no space to spare in a steel plant. FIG. 3 illustrates the further advantage that the ladle lit) may be set in a pit 51, thus further reducing the structural height of the system.

A linkage consisting of lever, guide bar and two hydraulic cylinders is by no means obligatory to secure the advantages sought by the invention. With suitable choice of geometrical relationships, it is sufficient for the degassing vessel 11, as in FIG. 4, to be rotatable about one fixed point 52. If a suitable mechanism for this rotation is provided, and if the an le of rotation is taken large enough, then all advantages of the invention as above described may be realized on this simple principie or" mounting the degassing vessel 11.

1 claim:

l. T method of degassing molten steel contained in a plur of ladies, comprising, charging a ladle with molten steel While the ladle is in a stationary position, providing an evacuable degassing vessel having a nipple above said ladle, dipping the nipple into the melt, repeatedly evacuating the degassing vessel to a predeter- T1 .ed point, to thereby effect suction of the metal into vessel and the degassing of the metal, withdrawing vessel and nipple from the ladle to afford clearance re-between, removing the ladle from its stationary position, emplacing another ladle in its place and repeat ing the foregoing step sequence.

2. Apparatus for the treatment of molten metal disposed in a plurality of containers, in combination, a vessel defining a chamber, a nipple extending downward from said vessel and opening into the lower end of said chamber, support means for positioning said vessel above one of said containers, said support means including lever means, said vessel being pivotable about a horizontal axis on one end of said lever means, and motive means operatively secured to the other ends of said lever means, said lever means being pivotally mounted intermediate its ends on said support means so that said vessel is movable into and out of vertical alignment with said containers.

3. The device according to claim 2, wherein said lever means are arranged to displace said vessel in a vertical plane.

4. The device according to claim 2, wherein said lever means are arranged to displace said vessel in an inclined plane.

5. The device according to claim 2, wherein said lever means are arranged to displace said vessel in a horizontal position.

6. The apparatus set forth in claim 2 wherein said support means also includes a second lever means pivotally connected to said vessel so that said vessel may be selectively pivoted about two horizontal axes.

7. The apparatus set forth in claim 6 wherein said second lever means includes extensible power means.

8. Apparatus for the treatment of molten metal dis posed in a container, in combination, an evacuable vessel defining a chamber, a nipple extending downward from the said vessel and opening into the lower end of said chamber, support means for positioning said vessel above said container, said support means including means for connecting said vessel to said support means for relative pivotal movement about a horizontal axis remote from the center of said container and below the center of said vessel, means for rotating said vessel about its pivotal axis so that it may be rotated into and out of vertical alignment with said container and said nipple immersed to varying depths below the surface of said molten metal, so that said molten metal is drawn into said chamber from said container and through said nipple upon evacuation of said chamber.

9. Apparatus for the treatment of molten metal disposed in a container, in combination, an evacuable vessel defining a chamber, said chamber having a relatively large lower surface, a nipple extending downward from said vessel and opening into the lower end of said chamber adjacent one side of said surface, support means for positioning said vessel above said container, said support means including means for connecting said vessel to said support means for relative pivotal movement about an axis substantially normal to a plane containing the axis of said nipple and lying between the axis of said nipple and said support means, evacuation of said vessel drawing said molten metal into said chamber from said container and through said nipple, and means for rotating said vessel about it's pivotal axis whereby the portion of said surface remote from said nipple may be raised and lowered relative to said nipple so that the quantity of metal in said chamber can be changed without substantial vertical movement of said chamber.

10. Apparatus for the treatment of molten metal disposed in a container, in combination, an evacuable vessel defining a chamber, said chamber having a relatively large lower surface, a nipple extending downward from said vessel and opening into the lower end of said chamber, support means for positioning said vessel above said container, means for pivotally connecting said vessel to said support means for rotational movement about a horizontal axis, means for producing relative vertical movement between said container and said vessel so that the lower end of said nipple may be immersed beneath the surface of said molten metal, so that said molten metal is drawn into said chamber from said container and into said nipple upon evacuation of said chamber, and means for rotating said vessel about it's pivotal axis whereby one side of said lower surface remote from said nipple may be raised and lowered relative to said nipple, so that the quantity of metal Within said chamber may be changed without substantial vertical movement of said vessel.

11. Apparatus for the treatment of molten metal disposed in a container, in combination, an evacuable vessel defining a chamber, a nipple extending downward from said vessel and opening into the lower end of said chamber, support means for positioning said vessel above said container, said support means including means for pivotably mounting said vessel about an axis substantially normal to a plane containing the axis of said nipple and remote from the center of said container, means for rotating said vessel about its pivotal axis so that said vessel may be moved into and out of vertical alignment with said container and said nipple is immersed below the surface of-said molten metal, so that said molten metal is drawn into said chamber from said container and through said nipple upon evacuation of said chamber.

12. Apparatus for the treatment of molten metal disposed in a container, in combination, a vessel defining a chamber, a nipple extending downward from the said vessel and opening into the lower end of said chamber, support means, arm means pivotally connected to said support means about a first horizontal axis and to said vessel on a second horizontal axis parallel to said first axis and substantially normal to a plane containing the axis of said nipple, means for pivoting said lever about said first horizontal axis so that said vessel may be moved into and out of a position vertically above said container.

13. A process for the degasification of molten metal comprising, maintaining subatmospheric pressure in a vacuum zone provided with a molten metal interconnecting passageway, maintaining a pool of molten metal in adjustable relationship with respect to said zone, causing a quantity of said metal to be drawn into said vacuum zone by reducing the relative distance between said zone and said bath, rotating said zone about a horizontal axis to lower a portion thereof relative to said passageway and thereby increase the quantity of molten metal therein, degasifying the metal within said zone by the application of said subatmospheric pressure thereto, returning said zone to its unrotated position to discharge a portion of the metal therefrom to said pool, and successively repeating the steps of rotating and unrotating said zone until the metal in said pool is brought to the desired degree of purity.

References Cited in the file of this patent UNITED STATES PATENTS 1,949,391 Lindner Feb. 27, 1934 1,990,370 Caputa Feb. 5, 1935 2,202,180 West May 28, 1940 2,512,643 Hannon June 27, 1950 2,678,714 Davis May 18, 1954 2,788,270 Nisbet et a1 Apr. 9, 1957 2,848,317 Coupette et a1. Aug. 19, 1958 2,893,860 Lorenz July 7, 1959 2,895,820 Harders July 21, 1959 2,948,417 Haanes Aug. 9, 1960