US3083422A - Porous stopper rod - Google Patents

Description

April 2, 1963 c. w, FINKL POROUS STOPPER ROD Filed April 13, 1959 2 Sheets-Sheet 1 v/ HU/ H IN V EN TOR. gar/e5 102m A @r%rffzrfer %zzameys United States Patent Office 3,083,422 Patented Apr. 2, 1963 3,083,422 POROUS STOPPER ROD Charles W. Fink], Chicago, Ill., assignor to A. Finkl & Sons Company, Chicago, Ill., a corporation of Illinois Filed Apr. 13, 1959, Ser. No. 805,927 Claims. (Cl. 22-85) This invention relates generally to methods of and apparatus for ladle degassing of molten metal.

In my co-pending application Serial No. 777,664, of which this application is a continuation in part, a method of degassing molten metals under vacuum conditions is disclosed. In this process, a hollow tube or snorkel extends through the wall of a vacuum chamber and into a ladle of metal to be treated. A vacuum is drawn in the chamber and when a sufficiently low value has been reached, an inert gas is forced through the tube and bubbled upwardly through the melt. The deleterious gases in the melt migrate into the bubbles and are discharged to vacuum when the bubble reaches the surface. The bubbles also set up a circulation which brings gas rich metal from the bottom to the surface where the vacuum can act on it. As disclosed in my aforesaid copending application, the degree of vacuum sufliciently low to effectively degas the molten metal is well below ten millimeters of mercury, and preferably on the order of about one millimeter of mercury or less.

This method has many advantages, but it requires additional equipment for positioning the snorkel in the ladle, extra time for insertion and removal of the snorkel, and higher tapping temperatures to compensate for the in creased time in the chamber.

Accordingly, a primary object of this invention is to provide a stopper rod for admitting purging gas to a ladle to eliminate additional purging equipment, cut purging equipment insertion and removal time to a minimum and utilize lower furnace tapping temperatures.

Another object is toprovide a gas porous stopper rod whereby purging gas may be diffused into the melt directly through the walls of the rod;

Another object is to provide a stopper rod having a porous refractory joint between adjacent sections of the rod which provides a localized emission point for the Purging gas.

A further object is to provide a stopper rod and plug assembly which admits purging gas to the melt at the lowest possible point in the container short of bottom purging.

Yet another object is to provide a method of treating metal in a container such as a ladle or the like under vacuum and non-vacuum conditions by the introduction of purging gas into the metal at variable distances above the bottom of the container.

Yet a further object is to provide a method of inhibiting the corrosive effect of molten metal slag on refractory stopper rods during degassing operation by washing the slag away.

Other objects will become apparent throughout the course of the following specification and drawings.

The invention is illustrated more or less diagrammatically in the accompanying drawings, wherein:

FIGURE 1 is a cross section of a ladle degassing apparatus showing a joint diffusion stopper rod;

FIGURE 2 is a section of a portion of the rod of FIG- URE 1;

FIGURE 3 is a cross section of a wall diffusion stopper rod;

FIGURE 4 is a cross section of a plug dilfusion stopper rod; and

FIGURE 5 is a view illustrating the plug diffusion rod in operation.

Like reference numerals will be used to refer to like parts throughout the following specification and drawings.

In FIGURE 1 a plurality of foundation beams 11 support a platform 12. on which rests a metal tank 13. A supporting ring 14 rises from platform 12 and carries a bearing ring 15. A layer of insulation 16 protects the platform from excmsive heat and metal leakage or spillage. The upper edge of tank 13 has a grooved flange 17 which receives a' seal ring 18 in the groove.

A dome 20 bounded at its outer lower periphery by a positioning flange 21 rests on the grooved flange 17. Aligning fingers 22 on flange 21 centerthe dome between studs 23 to ensure proper alignment. If the weight of the dome does not make a gas tight seal, additional clamping means may be utilized.

A sighting mechanism 24 including a glass 25 and heat shield 26 opens into the top of the dome so that an operator can readily observe the surface of the melt. A large exhaust passage 27 in the lower edge of the tank connects to a vacuum pumping system, not shown. Any suitable mechanism may be employed for lifting and lowering the dome into place on the tank. Since the lifting mechanism and vacuum system do not in them selves form an essential part of the invention they have not been illustrated. A heat shield 28 apertured at- 29 in line with the window is connected by brackets 30 to the dome.

A pouring ladle 31 which is lined with refractory at 32 has a circumferential seating ring 33 aligned with the bearing ring 15. Aligning fingers 34 and studs 35 position the ladle on the bearing ring.

A combination stopper rod and gas diffusing tube is indicated generally at 36 in FIGURES 1 and 2'. The assembly includes refractory sections or sleeves 37 having complementary abutting surfaces which form joints 38. The individual sleeves may be composed of any suitable refractory material. Bottom sleeve 39 rests on nozzle plug 40 which seats in' discharge nozzle 41. Each' refractory sleeve is cored to form an axial passage 42 extending the length of the rod.

The sleeves are supported on a tubular member 43 which is threaded at its upper end into the terminal portion 45 of a horizontal arm 46 and attached at its lower end to a stud 47. The stud receives plug 48. Nozzle plug 40 is molded about the lower end of the plug and forms a base for the sleeves.

The terminal portion of arm 46- is bored in line with passage 44 in the tubular member 43 and carries a fitting 50 to which agas pipe is connected. The gas pipe connects at the tank wall to' a flexible hose 52 leading to a source of pressurized, inert gas 53. Regulator 54 may be adjusted to any desired pressure readable on gauge 55.

The horizontal arm 46 is connected to piston 56 reciprocating in cylinder 57 which is secured to the ladle by bracket 58.

A detailed view of the-lower section of rod 36 is illus trated in FIGURE 2. The bottom surface of sleeve 31 has a blunt nos'e 60 which is complementary to a recess 61 in the bottom surface of sleeve 39. A porous ceramic disc 62 between the sleeve surfaces forms a porous joint which is, in effect, a gas flow path or passage extending from the longitudinal axial passage 42 through the rod: and terminating at a point a substantial distance below the surface of the molten metal. The disc may be of any suitable material such as silicon-carbide or alumina. Packing 63 prevents purging gas from escaping up the rod. Gas ports 64 are aligned with packing apertures 65 and the ceramic disc 62.

In FIGURE 3, lowermost sleeve 37 is in direct engagement with bottom sleeve 39. Uniformly or randomly spaced apertures 70 in injection pipe 71 open into direct communication with the interior of sleeve 39, and annular clearance space 72 between the pipe and sleeve acts as a diffusion chamber. In this embodiment, the refractory sleeve has a porosity great enough to permit outward seepage of gas, but small enough to prevent inward penetration of metal. A packing (not shown) may seal off chamber 72 above sleeve 39. Any individual sleeve may be used, but the best purging is attained by using the bottom sleeve. If insuffic-ient gas escapes, an additional sleeve may be utilized.

A structure for deep purging is ilustrated in FIGURE 4. In this embodiment, the lower refractory section 39 is joined to refractory nozzle plug 80 by interlock 81 threadably connected to the tip at $2. Interlock 81 receives injection pipe terminal 83 which has a flange 83:: positioned between plug 80 and the bottom of the interlock. The terminal is welded to injection pipe 43 at 84 and has a center passage 85 and branch outlets 86 communicating with injection passage 44. The outlets 86 mate with corresponding interlock apertures 87 aligned with a porous refractory disc 88 located between adjacent refractory surfaces of section 39 and plug 80. When the stopper rod is seated in discharge nozzle 89 as illustrated in FIGURE 5, the point of emission of the gas will be practically at the level of the bottom 90 of the ladle.

The use and operation of the invention are as follows:

This invention is used in purging molten metal under vacuum and non-vacuum conditions.

Present methods of purging or iusufflating utilize a separate injection tube which is lowered into the bath and connected to a source of carrier gas under pressure. This arrangement is somewhat unwieldly and time consuming since the vacuum chamber must be designed to accommodate the injection rod. With this invention, purging may be speedily and readily accomplished practically as soon as the seal is formed between the tank and vacuum dome since the stopper rod provides an initially, correctly positioned tube.

In operation, gas pipe 51 is connected to flexible hose 52 and the vacuum system turned on. As soon as flange 2'1 seats on the seal ring 18, free gases are drawn out of the tank through exhaust pipe 27. Carrier gas under pressure in tank 53 is then injected into the melt through stopper rod 36. The gas must of course be under a pressure above the ferrostatic head of the molten metal in the container at the point at which the gas is admitted to the melt.

In the embodiment of FIGURES 1 and 2, the rod itself is substantially impervious to the transmission of gases or even if pervious, transmission is effectively blocked by the solid injection tube 4-3 and packing 63. Mating apertures 64 and 65 in the tube and packing respectively, furnish a path for gas flow radially outwardly through the porous disc 62 and into the tank.

The circulation induced by the upwardly moving bubbles flows in the direction of the arrows. As the metal near the surface moves away from the rod it may carry the surface slag with it and pile it up against the opposite wall. This slag movement substantially minimizes rod deterioration due to the corrosive elfect of the slag and greatly lengthens rod life. In some cases, the bubbling may not be violent enough to pile up all the slag but in any event the area adjacent the rod is cleared and the rod is always kept free of slag.

It may be advantageous in some instances to position the stopper rod near the center of the ladle. The induced circulation is then outwardly away from the rod, and piles up the slag in a ring around the inner wall of the ladle.

In FIGURE 3, a variation is illustrated in which the purging or carrier gas is diffused outwardly directly through a rod sleeve. The rod is connected to carrier arm 46 as before and gas under pressure from tank 53 is admitted to the tank by regulator valve 54. As the gas enters the injection pipe 71 it passes through the apertures 70 and into annular diffusion chamber 72 from which it seeps outwardly through the wall and into the melt. The

rate of diffusion can be controlled by regulating the pressure and flow rate of the gas.

In the modification of FIGURES 4 and 5, the purging gas is admitted at the lowest possible point in the ladle. The ceramic disc 88 is located just above the nozzle plug 80, and gas enters the melt right at the level of the bottom. If a shorter nozzle is utilized, the [gas can enter the melt within the recess 91 surrounding the discharge hole. The behavior of [the slug will be substantially the same as in the embodiment of FIGURE 1.

Each of the embodiments of the invention may be utilized in air purging as well as vacuum purging. Less purging gas will be required under vacuum conditions, but 'the process is essentially the same and the induced circulation will be quite similar.

The foregoing description is illustrative only and not definitive. Accordingly, the invention should not be limited except by the scope of the following appended claims.

I claim:

1. A method of degassing a batch of molten metal in a ladle having a stopper rod seated in a discharge nozzle in the bottom of the ladle, said method including the steps of subjecting the surface of the molten metal to a vacuum suflicient to degas the molten metal, and simultaneously bubbling a suflicient volue of purging gas having little affinity for the molten metal outwardly through a gas porous member in the stopper rod adjacent its lower end, said gas porous member being sulficiently porous to permit outward passage of gas therethrough while resisting inward flow of molten metal, and thence upwardly through the molten metal to thereby induce a circulation within the ladle which brings substantially undegassed molten metal from remote areas in the ladle to the surface.

2. The method of claim 1 further characterized in that the purging gas is an inert gas.

3. The method of claim 1 further characterized in that the vacuum is on the order of about one millimeter of mercury or less.

4. A batch method of removing deleterious gases from a batch of molten metal in a receptacle having a bottom discharge opening and a closure member removably seated in said opening, said method including the steps of subjecting the surface of the batch of molten metal to a vacuum sufficient to degas the molten metal, and simultaneously agitating the molten metal to thereby set up a circulation within the receptacle which exposes remote, substantially undegassed portions of molten metal directly to the vacuum at the surface of the batch by forcing a carrier agent outwardly through a gas porous member in the closure member, said gas porous member being sufficiently porous to permit outward passage of gas therethrough while resisting inward flow of molten metal, and thence upwardly through the molten metal.

5. A batch method of degassing molten metal ina ladle having a stopper rod seated in a discharge nozzle located in the bottom of the ladle, said method including the steps of tapping molten metal into a ladle, subjecting the molten metal -to a vacuum sufficient to degas the molten metal, simultaneously bubbling a sufiicient volume of purging gas at a pressure above the head of the metal outwardly through a gas porous member adjacent the lower end of the stopper rod, said gas porous member being sufficiently porous to permit outward passage of gas therethrough while resisting inward flow of molten metal, and then upwardly through the molten met-a1 to induce a circulation entirely with-in the ladle which brings substantially undegassed molten metal from remote areas in the ladle to the surface, flooding the area above the surface of the molten metal in the ladle with an inert gas to thereby reduce the danger of explosion, and then exposing the ladle to atmospheric conditions.

6. Apparatus for degassing molten metal, said apparatus including, in combination, a container of molten metal to be degassed and a combination purging and stopper rod assembly for bubbling a purging gas upwardly through the molten metal, said combination purging and stopper rod assembly including an elongated rod having its lower end in sea-ting engagement with a discharge outlet in the container, said rod having a longitudinal passage extending a substantial distance through the rod, said rod being composed of a refractory material, means forming a gas flow path from the longitudinal passage through the rod and terminating a substantial distance below the surface of the molten metal in the container, said gas flow path forming means comprising a gas porous member having a plurality of gas passages of a size suflicient to permit outward passage of gas therethrough while resisting inward flow of molten metal, and means for connecting the longitudinal passage to a source of purging gas under a pressure sufficiently above the head of the molten metal at the point where the gas flow path terminates to cause the purging gas to pass outwardly into the molten metal.

7. Apparatus for degassing molten metal under vacuum, said apparatus including, in combination, a vacuum enclosure and means for drawing a vacuum therein sufiiciently low to degas molten metal, a container of molten metal to be degassed, and a combination purging and stopper rod assembly for bubbling a purging gas upwardly through the molten metal while it is subjected to a vacuum, said combination purging and stopper rod assembly including an elongated rod having its lower end in seating engagement with a discharge outlet in the container, said rod having a longitudinal passage extending a substantial distance through the rod, said rod being com posed of a refractory material, means forming a gas flow path from the longitudinal passage through the rod and terminating a substantial distance below the surface of the molten metal in the container, said gas flow path forming means comprising a gas porous member having a plurality of gas passages of a size sufficient to permit outward passage of gas therethrough while resisting inward flow of molten metal, and means for connecting the longitudinal passage to a source of purging gas under a pressure suflicien-tly above the head of the molten metal at the point where the gas flow path terminates to cause the purging gas to pass outwardly into the molten metal.

8. Apparatus for degassing molten metal, said appara tus including, in combination, a ladle of molten metal to be degassed, and a stopper rod assembly for bubbling a purging gas upwardly through the molten metal, said stopper rod assembly including, in combination, an elongated stopper rod having a nose at its lower end in seating engagement with a discharge outlet in the ladle, said stopper rod including a plurality of individual hollow refractory sections, said sections forming a longitudinal passage extending a substantial distance along the rod, a purging member between a pair of adjacent refractory surfaces, said purging member being composed of a refractory material having sufiicient porosity to permit outward flow of gas from the longitudinal passage While resisting inward penetration of the molten metal, means for connecting the longitudinal passage to a source of purging gas under a pressure suflioiently above the head of the molten metal at the point where the gas flow path terminates to cause the purging gas to pass outwardly into the molten metal.

9. The degassing apparatus of claim 8 further characterized in that the stopper rod includes a hollow metallic core extending the length of the longitudinal passage and shielded from the molten metal by the refractory sections, said hollow core having generally radially disposed apertures generally aligned with the porous refractory purging member.

10. Apparatus for degassing molten metal of claim 9 further characterized by and including a packing between the core and the refractory sections, said packing having apertures generally aligned with the porous refractory purging member and the apertures in the core.

References Cited in the file of this patent UNITED STATES PATENTS 51,397 Bessemer Dec. 5, 1865 1,261,509 Getrnan Apr. 2, 1918 2,005,311 Belding June 18, 1935 2,054,923 Betterton et al Sept. 22, 1936 2,475,777 Brown July 12, 1949 2,477,838 Toleik Aug. 2, 1949 2,724,160 Scheuer Nov. 22, 1955 2,811,346 Spire Oct. 29, 1957 2,839,292 Bellamy June 17, 1958 2,855,293 Savard Oct. 7, 1958

Claims (1)

1. A METHOD OF DEGASSING A BATCH OF MOLTEN METAL IN A LADLE HAVING A STOPPER ROD SEATED IN A DISCHARGE NOZZLE IN THE BOTTOM OF THE LADLE, SAID METHOD INCLUDING THE STEPS OF SUBJECTING THE SURFACE OF THE MOLTEN METAL TO A VACUUM SUFFICIENT TO DEGAS THE MOLTEN METAL, AND SIMULTANEOUSLY BUBBLING A SUFFICIENT VOLUE OF PURGING GAS HAVING LITTLE AFFINITY FOR THE MOLTEN METAL OUTWARDLY THROUGH A GAS POROUS MEMBER IN THE STOPPER ROD ADJACENT ITS LOWER END, SAID GAS POROUS MEMBER BEING SUFFICIENTLY POROUS TO PERMIT OUTWARD PASSAGE OF GAS THERETHROUGH WHILE RESISTING INWARD FLOW OF MOLTEN METAL, AND THENCE UPWARDLY THROUGH THE MOLTEN METAL TO THEREBY INDUCE A CIRCULATION WITHIN THE LADLE WHICH BRINGS SUBSTANTIALLY

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