US3741152A - Apparatus for continuously teeming and solidifying virgin fluid metals - Google Patents

Abstract

A tundish of virgin fluid metal has a vertical tubular stopper controlling the flow of fluid downwardly through a corresponding port in the bottom of the tundish and a rod of solid state metal is moved downwardly through the hollow stopper to receive the downwardly flowing fluid metal in accretion thereon as the stopper is raised from its seat. Where more than one stopper is employed, the bottom of the tundish is stepped to provide different depths of fluid metal head for each successive stopper and means are provided for moving the rod downwardly through successive stoppers for successive accretion of metal thereon in producing a continuous billet.

Description

United States Patent [191 Williams APPARATUS FOR CONTINUOUSLY TEEMING AND SOLIDIFYING VIRGIN FLUID METALS [75] Inventor: Sylvester V. Williams, Omaha, Nebr.

[73] Assignee: Elwin A. Andrus, Milwaukee, Wis.

a part interest [22] Filed: Oct. 6, 1971 [21] Appl. No.: 187,192

Related U.S. Application Data [63] Continuation of Ser. No. 820,846, May 1, 1969, abandoned, which is a continuation-in-part of Ser. No. 497,177, Oct. 18, 1965, abandoned.

[52] U.S. Cl. 118/405 [51] Int. Cl. B05c 3/02 [58] Field of Search 118/405, 404, 420,

118/D1G.18, DIG. l9; 266/3 R; 117/115, 114 R, 114 A, 114 B, 114 C; 164/82, 86,275

2/1941 Schultz .1: 118/405 x [451 June 26, 1973 Primary Examiner-Morris Kaplan Attorney-Elwin A. Andrus 57 ABSTRACT A tundish of virgin fluid metal has a vertical tubular stopper controlling the flow of fluid downwardly through a corresponding port in the bottom of the tundish and a rod of solid state metal is moved downwardly flowing fluid metal in accertion thereon as the stopper is raised from its seat. Where more than one stopper is employed, the bottom of the tundish is stepped to provide different depthsof' fluid metal head for each successive'stopper and means are provided for moving the rod downwardly through successive stoppers for successive accretion of metal thereon in producing a continuous billet.

4 Claims,'5 Drawing Figures PATENIEDJUNZS ms 3.741. 152

sum 2 or 2 INVENTOR Suva-arm l. W/u/Ans APPARATUS FOR CONTINUOUSLY TEEMING AND SOLIDIFYING VIRGIN FLUID METALS CROSS REFERENCES This application is a continuation of application Ser. No. 820,846, filed May 1, 1969 as a continuation-inpart of application Ser. No. 497,177 filed October 18, 1965, and which first parent application was abandoned in favor of the second parent application and of an application for the method disclosed therein and which was filed on even May 1, 1969. This application was filed in response to a requirement of restriction in the prosecution of the first parent application.

This invention relates to an apparatus for continuously teeming and solidifying virgin fluid metals.

The apparatus is particularly useful in carrying out the process of the above-identified companion method application and wherein virgin fluid metal from pyrometallurgical or electrometallurgical refining processes is teemed and solidified in an accretion around a solid body while leaving the fluid outer surface free for the expulsion of gaseous state impurities as the metal coagulates and fuses to a solid state contiguously from the inside toward the outside.

The apparatus differs from that employed in accretion processes for the coating of wires principally in that a rod or core is not dipped in a molten metal bath but passes downwardly through a tubular stopper out of contact with the fluid metal until the core passes into and through the short nozzle where an accretion of fluid metal embraces the same.

The apparatus also employs a stepped tundish with nozzles at different depths of the bath to provide for recycling of the core and thereby to build up a more practical sized billet of the metal.

By employing a downward movement of the core during teeming and solidification of the virgin fluid metal thereon, the amount of accretion is not opposed by gravity or inertia and can be controlled within practical limits developed for the particular conditions of fluidity of the metal and the speed of the core.

The present invention is based upon the concept of flowing of the fluid metal downwardly around a downwardly moving rod of the same metal which fosters accretion by fusion of the two at their meeting surfaces resulting in core crystallization growth as the metal solidifies from the inside out with the outer surface remaining generally in a fluid state so that the hot gases and impurities are free to escape laterally and to be expelled from the metal as the latter crystallizes and solidifies, without any interference from a surrounding liquid or solid state environment.

In this process the freedom for escape of the gaseous impurities which generally consist of the higher energy atoms makes it possible for the remaining atoms to spontaneously reduce their energy and take their permanent position in the lattice work of the'solid state body without danger of returning to a liquid state. Thus, the soldification or change of state of the atoms becomes spontaneous and permanent.

The apparatus moves the core rod downwardly through a tubular shield in the fluid bath of virgin metal and the fluid metal is allowed to flow at a controlled rate in a continuous tubular stream or moving column about the core rod and which embraces the latter as the two move downwardly together.

The wide divergence of energy level of the inner surface of the fluid stream with the outer surface of the core rod as they move downwardly together triggers the spontaneous change of the accretion metal from a fluid state to a liquid state and then to the solid state. Theoretically, one pound of solid state metal can solidify about five pounds of fluid state metal. The volume relationship between the fluid and solid states involved should therefore be well kept within that ratio.

The core rod is kept out of contact with the fluid metal in the tundish and does not appreciably begin to lose its solidifying capacity until it comes in contact with the downward flow of virgin metal which has passed through the discharge nozzle from the tundish.

The apparatus may be quite simple and merely comprises the tundish for the fluid metal having a pouring opening or nozzle in its bottom with a stopper. The stopper is made tubular and extends to a point above the fluid metal so that the core rod is fed down through the hollow stopper without contacting the fluid metal until the rod emerges from the stopper at the discharge nozzle for the fluid metal. The fluid metal is applied to the rod by adjustably lifting the stopper and allowing a predetermined and controlled flow of fluid downwardly embracing the rod. Dropping of the stopper to its seat stops the flow of fluid metal.

In general, the relative volume and temperature or energy level of the fluid and solid state bodies and the rate of travel will determine the length of the solidifi-. cation zone required beneath the tundish and before the accretion on the solid state core can be bent laterally for horizontal movement.

The rod is preferably moved downwardly at a rate exceeding the downward gravity discharge rate for the fluid metal from the nozzle. In practice, the speed of the rod through the nozzle may be of the order of 340 feet per minute. The speed may be higher for metals that are more fluid and may be lower for metals that are less fluid. f

It is contemplated that the solidified structure may be returned to another stopper for a successiveaccretion or fusion operation thereon, and that as many successive accretions may be made as is practical for any given operation. In this way, a core rod of one-half inch diameter initially, may be built up to a final solidified billet having a diameter of the required inches.

accretion resulting pass starting size thickness size 1 A Va" 1 2 III I 5/161! 1 I! 3 l *1! 5/16! 2%! 4 2%" 3" Further passes may be made as desired.

The completed billets or shapes may be cut to suitable lengths and each will constitute in effect a billet of refined metal or alloy substantially free of defects. The costly blooming of ingots may be substantially eliminated. The continuous billet without being cut may be rolled directly into a desired rod, wire or other shape and coiled with or without further heating.

The bath of metal may be said to be in a fluid state composed of liquid phase metal and gaseous phase impurities generally in solution therein. The gaseous phase materials are generally of higher energy than the liquid phase metal, and the liquid metal is of substantially higher energy level than the solid state metal.

'The final structure would be free of pipes, fissures and impurities, since the gaseous phase materials are forced to escape from the fluid state molten material as the liquid phase metal crystallizes or solidifies in contact with the solid state core.

The tundish may be supplied with metal from a crucible disposed adjacent thereto, and a submerged spout may provide for pouring either way, from the crucible to the tundish or from the tundish to the crucible, as desired.

The present apparatus is illustrated more or less scheraised and the flow of metal during the teeming process.

Referring to the drawings, the crucible or tundish 1 is generally formed with a step bottom to provide for different and increasing depths of-fluid metal 2 in the several fusion zones A,B, ,C, D and E. Any suitable number of fusion zones may be provided within the range of practical handling of the core rod 3 which increases in diameter by fusion and accretion at each zone.

Each fusion zone of crucible 1 has a nozzle opening 4 in the bottom for the discharge of fluid metal 2, and

which opening is'closed by a stopper 5 at times other than during a teeming operation.

Each stopper 5 is tubular and has a central vertical opening 6"the rethrough for the free passage or movement of rod 3 downwardly therethrough during a teeming operation.

Stoppers 5 are made up of a plurality .of rings 7 of refractoryceramic material, each interlocked with its ad jacent blocks, with a seat ring 8 at its lower end for seating in a nozzle opening 4, a cap ring 9 at its upper end, and a tubular bolt 10 extending vertically through all of the blocks and secured at its lower end to seat ring 8 and having a threadednut I 1 at its upper end for tightening upon cap ring Qand thereby completing the stopper.

Each stopper 5 should be of a length to extend substantially above the top of the fluid metal 2 in tundish 1 when the stopper is seated upon itsnozzle opening 4. For this purpose, the number of rings 7 and the length of bolt 10 will be selected accordingly.

The shorteststopper'S is in zone A, and each successive zone, B, C, D and E has a longer stopper, determined by the amount of step in depth for the zone.

Also, the diametersof nozzle openings 4 and of stoppers 5 will be different in the different zones. The nozzle openings 4 and stopper 5 for zone A will have a diameter suited to the fusion accretion of metal upon the initial core rod 3 which may be in the order of less than 1 inch in diameter. The nozzle opening 4 and stopper 5 for the next zone B will have a diameter suited to the fusion accretion of metal upon the rod 3 after it has received a first layer of accretion metal and which may then be of a diameter somewhat in excess of one inch. The nozzle opening 4 and stopper 5 for each successive zone will have a diameter suited to the contiguous solidification of metal upon the rod 3 plus-its accretion layers previously fused thereon in the process. I

The mechanism for supplying and'handling the rod 3 during the process is illustrated schematically in FIG. 1, and comprises, in general, a supply drum 12 from which the. rod is fed over a sheave l3 and thereby aligned with the stopper 5 in zone A. As the rod 3 is fed downwardly toward stopper 5, it passes through a set of straightening rolls l4 and then into the upper end of bolt 10 of the stopper.

As the rod 3 emerges from the bottom end of bolt 10 or stopper 5 and continues downwardly through the nozzle opening 4 in tundish 1, fluid metal is released to flow with and embrace the rod by raising of the stopper, as indicated in FIG. 5.

The position of stopper 5 should be adjusted to give a desired maximum flow of fluid metal having regard to the speed of movement of rod 3 and to the practical thickness of accretion metal 15 that can be solidified upon the rod in a single pass.

As the rod 3 and its first layer of accretion metal 15 continues downwardly at a rapid rate, itpasses through a chamber 16 where partial solidification takes place, and then down to a series of rollers 17 disposed to change its course gradually from a vertical to a horizontal path and then to a vertical return path leading to the second sheave 18 above zone B.

Sheave 18 feeds the work blank,consisting of rod 3 and its firstlayer of accretion metal 15, downwardly through straightening rolls 19 and into the stopper 5 for zone B which in turnis adjustably raised to release fluid metal to the outer surface of metal 15 constituting the new outer surface of core material.

Each successive zone has a chamber 16 and rollers 17 for receiving the rod and its accretion layer of metal. Likewise, each successive zone has its sheave 18 and straightening rolls 19. In each successive zone, the

work blank will be larger in diameter, determined by the increment or layer of accretion metal added thereto at the next preceding zone.

The chamber 16 in each instance should be of such length as to effectively receive substantially all gaseous state impurities expelled from the accretion layer upon the rod prior to its reaching the rolls 17.

Depending upon the characteristics of the metal or alloy beingprocessed, the speed of movement of rod 3 and the amount of accretion flow being applied to the rod, it may be desirable to asperse inert gas into chamber 16 through connection 20 from source 21 to thereby flush out of chamber 16 the gases emitted from the fluid metal as it solidifies upon the downwardly moving rod 3. i

In general, at higher speeds and with larger amounts of accretion, it may be desirable to apply a partial vacuum tochamber 16 through connection 20 from vacuum source 22, in which case the gases exuded from the accretion metal are more rapidly drawn off and the metal remains more fluid at its surface for a longer time. The partial vacuum has a tendency to draw cooling air into the lower end of chamber l6'and thereby effect cooling and solidification of the metal just prior to entering rolls l7.

The movement of stoppers 5 may be accomplished by any suitable mechanism, not shown, and which is connected to an arm 23 secured to the upper end of each stopper.

The tundish 1 may be maintained full of fluid metal to the desired level at all times by the auxiliary container, crucible or mixer 24 into which fluid metal is poured from ladies from time to time. The arrangement is such as to provide for possible return of the fluid metal from the tundish back to the crucible should the process become stopped for any reason and it becomes desirable to empty the tundish.

- The fluid metal 2 in crucible 24 and/or in tundish 1 may be kept at a predetermined temperature by auxiliary electric induction heating means 25 extending around the crucible and tundish, and which may be designed to effect a stirring of the fluid metal.

The depth of fluid metal for each teeming zone is maintained to provide a pressure of fluid at the corresponding nozzle to give the necessary acceleration to the fluid flow through the nozzle whereby the accretion metal flows onto rod 3 at nearly the downward speed of movement of the rod.

In the teeming process, the intimate contact between the tubular column of fluid flow and rod 3, which may be assisted by maintaining a slight pressure in chamber 16 from connection 20, provides a very rapid energy transfer from the fluid column now on the solid rod 3. As the fluid state metal comes into contact with the solid state core metal, there is an instantaneous equalization of the energy level of both surfaces with a coalescing of the atoms, which may be aptly referred to as contiguous solidification. The resulting solidification of the fluid metal from the core toward the outer surface is spontaneous at the meeting surfaces. This triggers the emission of the gases as solidification advances from the inner core surface outwardly toward the outer surface of the accretion.

As the fluid metal is solidified from the inside, gases entrapped therein are forced outwardly and escape into chamber 16 where they are flushed away by the moving gases flowing through the chamber, or are drawn away by the vacuum source, as previously described.

The virgin metal, being in a fluid state with entrapped gases present, becomes triggered rapidly toward solidification of the liquid state, and the freedom for escape of the gaseous state provides freedom in the environment for crystallization of the metal during solidification.

In this process, the size or volume relationship of fluid to solid state area is controlled by the orifice size of nozzles 4 effected by raising of the stoppers 5, the head of fluid metal at the zone from which the fluid metal flows, and the speed of travel of the solid state core.

Core crystallization growth or contiguous solidification is obtained entirely without molds with their fixed dimensions and shapes to confine and compress the fluid state while the change in state takes place. There is no restricting volume of fluid metal present during the solidification. The solid state is therefore free to form spontaneously and to maintain its stable properties and shape. Thus, the core growth or contiguous solidification is always from the inside out toward the periphery.

The high energy atoms of the entrapped gaseous state present in the fluid state of the virgin metal are encouraged'by the environment to escape outwardly to the surrounding gaseous environment so that the liquid atoms of the virgin metal can drop abruptly to the energy level of the solid state freely with substantially no slowing down or arresting of the change.

This change in energy level of the atoms takes place continuously in predetermined regions of travel of the rod 3 and accretion metal 15 in chamber 16 or beneath it. The liquid state atoms seek the lower energy of the solid state and take their place and maintain it in the natural lattcice work inherent in metals of the solid state, without interference from the higher energy atoms of the gaseous state.

The nucleus of the latent solid state atoms is not encouraged to return to an excited condition of liquid state by the presence of higher energy gaseous state atoms or molecules as occurs in ingot casting processes.

The orbiting electrons of the nucleus can drop down closer to their fixed orbits of the solid state, and the free electrons can join the nucleus, thus offering them the lowest energy level to be found in the solid state. The bonding action of the free electrons becomes instantaneous, thereby establishing the solid state and shape of the metal cyrstals.

The rate of travel of. the moving solid state core through the hollow stopper can be varied independently and needs only to be adjusted to effect solidification of an optimum thickness of the newly grown solid state desired on its periphery. In general, the rate of core movement should approximate the speed of flow of fluid metal resulting from the gravity pull at the nozzle thereon for the given head and opening.

The core maintains its metallic bonding free electrons and brings under control the free electrons of the moving liquid state embracing its periphery. As the higher energy electrons of the gaseous state leave to the outside the lower energy electrons of the liquid state remain for solidification on the growing surface of the parent core.

The solid state grows exponentially as the liquid state decreases or shrinks exponentially.

An adjustment between the relative rate of travel of the core 3 and the surrounding column of fluid state virgin metal can effect relative elongation or shortening of the fluid state column and determine or establish the desired depth of solid state growth in any given fusion or teeming operation. Thus, a faster core speed for a given nozzle opening reduces the thickness of solid state accretion metal 15, and a slowercore speed for the same nozzle opening will increase the thickness of solid state accretion metal 15.

The greater the surface area and moving mass of the solid state, the larger the volume of fluid metal that can be solidified in any one cycle.

In carrying out the invention, either a single layer of accretion metal 15 may be fused upon the core rod 3, or by recycling as illustrated in FIGS. 1 to 3, a multiple number of layers of accretion metal may be successively fused upon the rod. The final size of the rod or end product will be limited depending upon practical handling'facilities and characteristics of the metal or alloy being teemed.

Where recycling is employed, each successive layer of deposited metal fused upon its predecessor will effeet a re-crystallization and refinement of the metal of the previous layer, thereby improving the physical properties of the final structure. The process utilizes the forces of gravity to accelerate the fluid flow of vir- 7 gin metal to generally simulate the speed of rod movement. In the present process, the core rod never comes into contact with the fluid metal in the container or tundish l and thus does not melt prior to the fusion or thus the core rod is retained at as low an energy level as practical so that is capacity for accretion of fluid metal by solidification from within is kept as high as is reasonably possible.

When recycling is employed to deposit one layer of metal upon another, the quality of the previously deposited metalis improved, much as in fusion welding processes where one layer is deposited upon another.

The layer or layers of accretion metal are substantially free of lattice work dislocations, voids and incipient cracks or failures, and also of internal stresses.

The more perfect lattice work of the metal offers maximum resistance to applied energy from an external source since the, bonding energy of the free electrons is at ornear to its maximum. Any applied energy is more equally distributed throughout the crystaline lattice work.

The atoms at the meeting surfaces between the core rod and the fluid column must be free to move into their natural place in the lattice work for bonding purposesflo facilitate this, it may be desirable to clean the surface of the solid state core as by grits blasting or ultrasonic means before it enters the hollow stopper to clean itof all oxides and surface impurities. If practical,

in a given instance, it may be possible to enclose the entire operation in an inert or a deoxidizing atmosphere.

I claim:

1. In combination, a tundish for containing virgin fluid metal and having a step bottom to provide zones of successively greater depths of fluid metal therein, a teeming nozzle at the bottom of each zone, a tubular stopper closing each said nozzle and extending upwardly therefrom to above the level of fluid metal in the tundish, means to move a continuous core rod downwardly through the hollow stopper for the zone of least depth and to recycle the same downwardly through each stopper of the successively deeper zones,

and means to raise and lower the stoppers to provide for the controlled flow of successive tubular columns of fluid metal upon the rod as it progresses through the several zones, said openings and stoppers for each successive zone being larger than for the next preceding zone to provide for the successive accretion of metal upon the core rod as it passes through the several zones.

2. In combination, means to contain virgin fluid metal in successive operative zones, a teeming nozzle at the bottom of each zone, a tubular stopper closing each said nozzle and extending upwardly therefrom to above the level of fluid metal in the corresponding zone, drive means to move a continuous core rod downwardly through the hollow stopper for one zone and-to recycle the same downwardly through each stopper of the successive zones, and means to raise and lower the stoppers independently of each other to provide for the controlled flow of successive tubular columns of fluidometal downwardly with and embracing the rod as it progresses through the several zones, said openings and stoppers for each successive zone being larger than for the next preceding zone to provide for the successive accretion of metal upon the core rod as it passes through the several zones.

3. The construction of claim 2 and heated storage means for virgin fluid metal adjacent said first named means, and means to transfer virgin fluid metal from said storage means to said first means and from said first named means to said storage means.

4. In combination, means to contain virgin fluid metal in zones of successively greater depths of fluid metal, a teeming nozzle at the bottom of each zone, a tubular stopper closing each said nozzle and extending upwardly therefrom to above the level of fluid metal in the, corresponding zone, drive means to move a continuous core rod downwardly through the hollow stopper through the several zones.

t a e w *I

Claims (4)

1. In combination, a tundish for containing virgIn fluid metal and having a step bottom to provide zones of successively greater depths of fluid metal therein, a teeming nozzle at the bottom of each zone, a tubular stopper closing each said nozzle and extending upwardly therefrom to above the level of fluid metal in the tundish, means to move a continuous core rod downwardly through the hollow stopper for the zone of least depth and to recycle the same downwardly through each stopper of the successively deeper zones, and means to raise and lower the stoppers to provide for the controlled flow of successive tubular columns of fluid metal upon the rod as it progresses through the several zones, said openings and stoppers for each successive zone being larger than for the next preceding zone to provide for the successive accretion of metal upon the core rod as it passes through the several zones.

2. In combination, means to contain virgin fluid metal in successive operative zones, a teeming nozzle at the bottom of each zone, a tubular stopper closing each said nozzle and extending upwardly therefrom to above the level of fluid metal in the corresponding zone, drive means to move a continuous core rod downwardly through the hollow stopper for one zone and to recycle the same downwardly through each stopper of the successive zones, and means to raise and lower the stoppers independently of each other to provide for the controlled flow of successive tubular columns of fluid metal downwardly with and embracing the rod as it progresses through the several zones, said openings and stoppers for each successive zone being larger than for the next preceding zone to provide for the successive accretion of metal upon the core rod as it passes through the several zones.

3. The construction of claim 2 and heated storage means for virgin fluid metal adjacent said first named means, and means to transfer virgin fluid metal from said storage means to said first means and from said first named means to said storage means.

4. In combination, means to contain virgin fluid metal in zones of successively greater depths of fluid metal, a teeming nozzle at the bottom of each zone, a tubular stopper closing each said nozzle and extending upwardly therefrom to above the level of fluid metal in the corresponding zone, drive means to move a continuous core rod downwardly through the hollow stopper for the zone of least depth and to recycle the same downwardly through each stopper of the successively deeper zones, and means to raise and lower the stoppers independently of each other to provide for the controlled flow of successive tubular columns of fluid metal downwardly with and embracing the rod as it progresses through the several zones, said openings and stoppers for each successive zone being larger than for the next preceding zone to provide for the successive accretion of metal upon the core rod as it passes through the several zones.

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