US2787537A

US2787537A - Method of producing metal

Info

Publication number: US2787537A
Application number: US690751A
Authority: US
Inventors: Harley A Wilhelm
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-08-15
Filing date: 1946-08-15
Publication date: 1957-04-02
Anticipated expiration: 1974-04-02

Description

April 2, 1957 H. A. WILHELM METHOD OF PRODUCING METAL 2 Sheets-Sheet l Filed Aug. l5, 1946 April 2, 1957 H. A. WILHELM y 2,787,537

METHOD OF PRODUCING METAL Filed Aug. 15,. 1946 2 Sheets-Sheet 2 METHOD F PRODUCING WTAL Harley A. Wilhelm, Ames, Iowa, assigner to the United States of America as represented by the United States Atomic Energy Commission Application August 15, 1946, Serial No. 690,751

Z Claims. (Cl. 75-'84.1)

This invention relates to the casting of metal produced by reduction of metal halides such as UFL; in a bomb and more particularly relates to method and lapparatus for tapping o the resulting metal from the reduction crucible.

The invention is concerned with an improvement in the process of reacting metal halides with an alkali metal or an alkaline earth metal at a temperature sufficiently high to form molten metal. In this process as previously conducted, an alkaline earth or alkali metal such as magnesium or calcium is mixed with a halide such las uranium tetrafluoride. This mixture is placed in an elongated bomb and the bomb is heated until sufflcient heat is developed by the resulting exothermic reaction and/or by the heat introduced into the mixture prior to initiation of the reaction to cause formation of uranium in molten state and to cause the uranium to remain in molten state until it has largely separated from the slag. Thus, the resulting metal collects at the bottom of the reaction bomb and the slag and other impurities rise to the top. Specific details of the theory and certain characteristics of the production of metals by reduction are set forth in the copending applications of Frank H. Spedding, Harley A. Wilhelm and Wayne H. Keller, Serial No. 628,652, iled November 4, 1945, and Serial No. 513,996, tiled December 20, 1943, which is now abandoned.

Prior to the present invention, the metal after separation had been allowed to cool to room temperature while in the bomb, and the contents removed from the Vbomb and the metal separated physically from thev `solidified slug. The usual practice has been to remelt the metal in vacuo and to recast the molten metal. has been objectionable not only because of the number of operations required but also because remelting resultsV in some loss of metal due to oxidation formation of carbide, etc. At the same time early attempts to tap off `and cast the molten uranium from the bomb in a single operation were unsuccessful.

In accordance with the present invention method and apparatus have been provided by which uranium and similar metals may be produced in molten Vstate by reduction of the corresponding halides and cast directly without ,recourse to recasting or remelting operations previously regarded as necessary. Y

It is, therefore, an object of this invention to provide a simple, dependable means and method for producing a metal such as uranium in molten state and for the tapping of molten metal off from a reaction chamber, such as a reduction bomb, without substantial reaction of the metal with the surrounding air.

This and other features of this invention contributing to the simplicity of construction and dependability in operation will be apparent from the following detailed description of a preferred embodiment taken with the accompanying drawings, in which:

Fig. ,l vis a vertical sectional view of a reduction bomb Such a processV f item in combination with a mold, the valve assembly of the bomb being shown in open position; Y

Fig. 2 is a fragmentary vertical sectional view comparable to Fig. 1 but showing the valve assembly in closed position; Y y

Fig. 3 is an enlarged horizontal sectional view of the valve yassembly taken along line 3 3 of Fig. 1;

Eig. 4 is a vertical sectional view of the valve housing shown mounted on a mandrel used for the construction of the lining of the crucible; and

Fig. 5 is a top plan View of the bomb shown in Fig. l.

In the production of Va metal such as uranium by reduction of UF. with a reducing metal and the casting of the metals into billets, it is necessary to reduce to a minimum the exposure of the hot metal to the atmosphere to minimize oxidation problems. In general, the apparatus of this invention includes a bomb in which the reaction is intended to take place provided with a special type of valve mechanism built into the bottom thereof and maintained in a closed position during the reduction reaction. This valve is actuated to lan open position at the completion of the reaction and before metal has solidified to drain the molten metal into a mold.

With reference to Fig. l, a reduction reaction bomb 1 of any convenient size, for example, 6-14 inches inner diameter and 3-4 feet in length is shown in .position for tapping and in such a position is disposed above a mold 2, a cone plate 3 of the mold 2 being centered beneathV the reaction bomb 1. The reaction bomb 1 is composed of a refractory lining 4 of calcium oxide, magnesium oxide or dolomite in a steel jacket 5 forming a chamber 6 covered by a blank ange 7 which is bolted to the` A valve assembly 8 is dis,

end plate 35 of the jacket. posed within the jacket 5 in a central opening 70 in the bottom 9 of the bomb 1. The jacket wall 5 extends beyond the bottom 9 to form a circular skirt 10 within a vertically disposed housing 12 and spout 13, the spout Y being centrally bored to provide a vertical passage` 14- which terminates in an oriiice 15 at its lower Yend and an exteriorly threaded boss 16 at its upper end. This boss, as shown, is integral with the spout 13. Below the boss 16, ports 17 are provided through the wall of the spout 13 which provide access to the central passage 14. A pointed conical head 18 which extends into chamber 6 (Fig. l) is screwed onto the threaded boss 16 with its apex 19 at the top. The horizontal sectional view of Fig. 3 is taken immediately below the top of housing 12 and shows the spout 13 in the housing 12 and ports 17 in the wall of spout 13 opening into the central passage 14. The lower end of spout 13 is formed into a truncated hemisphere 20 with its curved surface 21 facing downwardly and the flat upper surface 22 forming a ledge around the spout 13. The orice 15 ofthe passage 14 is located centrally in the lower face 23 of the spout 13.

The spout 13 is free to slide up and down in the housing 12. The normal position of the spout 13, in the housing, is shown in Fig. 2 with the spout 13 in its lowermost or closed position and with the lower surface 24 of the head 18 resting on the upper rim surface 25 of the housing 12. When the spout 13 is in this position, the head 18 disposed against the housing Wall seals the ports 17 from 4the chamber 6. The spout 13 is movable upwardly from the normal position to an upper or open position. The ledge 22 strikes the lower edge of housing 12 to limit this upward movement. In the open position, as yshown in Fig. 1, the centers of the ports 17 are disposed above the rim but preferably with the bottom of the port slightly below the rim and provide communication between the chamber 6 and the central passage 14.

In preparing the bomb, the bottom surface 9 is first provided with a refractory layer. This is accomplished by placing over the opening 'ti a rod having a length greater than that of the bomb and having a rounded plug at its lower end which is slightly larger than the opening 70. This plug has a length somewhat greater than the depth of the refractory layer to be deposited. The bottom conical portion of the bomb is then filled ywith a refractory such as dolomitic oxide or calcium oxide and the refractory lightly tamped by jolting the bomb or by other means. Thereafter the upper end of the rod is rota-ted in an essentially circular path more or less concentric with the circumference of the bomb whereby a conical opening in the tamped refractory immediately above opening 7) is produced.

Housing 12 is centrally mounted on the cylindrical shoulder 72 so that it abuts the face 73 on the bottom of mandrel 27 (Fig. 4) and is held in place by a round nut 71 screwed to the lcentral stud 46 which extends from the bottom of the mandrel. Nut 71 is locked in place by cone nut 26 which is conical in shape in order to serve as a guide to facilitate insertion of the hou-sing 12 in the opening in the refractory layer. The mandrel 27, with the housing 12 attached thereto, is lowered into and `centrally disposed in the jacket 5 after the refractory bottom lining is laid and the housing l2 is fitted through the opening in the refractory layer and the opening 7d so that an exteriorly threaded portion 2S at the lo-vver end of housing 12 protrudes from the bomb 1. When the mandrel 27 is in place the refractory in the bottom assu-mes the contour of the mandrel bottom and of the housing 12. A shoulder 29 formed around the 'upper end of housing 12 is seated in the refractory bottom lining and secures the housing in place.

The mandrel 27 is provided with an upstanding cylindrical portion 27a having an outer diameter less than the inner diameter of the jacket 5 so that when the mandrel is inserted in the jacket 5 an annular space is left between the jacket 5 and the cylinder 27a that is substantially coextensive with the heigh-t of chamber 6. The refractory lining 4 is then formed around the centrally disposed mandrel 27 by introducing into the space therearound a finely powdered anhydrous magnesium oxide, dolomitic oxide, calcium oxide or similar oxide and `subjecting the bomb to a rapid jolting action whereby the powder becomes compacted into an integral well-bonded lining.

*Following the lining operation. the nuts 26 and 71 are removed from the stud 4) and a graphite washer 35i (IFig. 2) isrfitted over the protruding portion of the housing 12 and against the bottom 9. A nut 31 is then screwed onto the threaded portion 28 until it bears against the washer 30 and tightens the shoulder Z9 in its seat. Thereupon the mandrel is removed.

The spout 13 with the head 18 removed is next inserted into the housing 12 from below until it projects into chamber 6 and then the head 18 is screwed onto the threaded boss 16 to confine movement of the spout to a sliding action limited by the abutment of head 13 and hemisphere 20 against housing 112.

Thus, there is provided a valve which seals the avenue of escape of the molten metal from its container and which has a dependable action that readily opens the valve to tap the. molten metal collected at the bottom of the chamber 6 and pour it in-to the mold 2 juxtaposed with the utmost proximity to reduce exposure to oxidation to the minimum.

As described in the above-identified applications, a finely divided mixture comprising a metal halide such as uranium tetraiiuoride and a quantity of magnesium or calcium, usual-ly 540 percent in excess of the theoretical amount Irequired for reaction, is introducedfinto the rein Fig. l.

actor and a cover 32 of graphite or similar heat resistant material is fitted on top of the charge.

The sides of this cover preferably are beveled outwardly from top and bottom toward the middle area of the side so that the diameter of the ends thereof is less than the diameter of the central area -of the cover. By means of the bottom bevel, the cover may be easily inserted into the lined bomb to form a tight fit without danger of the cover falling to the bottom Yof the bomb since the diameter of the central area is greater while the diameter of the bottom is less than the inner diameter of the lined jacket. By means of the t-op bevel further refractory may be pack-ed over the cover and in the space between the side of `the cover to permit establishment of a seal. Use of graphite or other solid integral covers of this type which do not tend to pulverize result in better yields since any tendency for the refractory oxide to fall into the reaction mass and thereby raise the melting point thereof is minimized.

Following fitting of the cover a layer of calcium oxide or other refractory is laid over the cover and the bomb is closed by bolting the blank flange 7 to the end plate 3S of the bomb. The bomb is then introduced into a soaking pit or is otherwise heated to initiate the reaction. Sufficient heat is introduced so that the total heat evolved and introduced will cause formation of molten metal and maintain the mixture in molten state until the metal has been separated and tapped from the reactor.

During the heating operation, the reaction mixture is carefully observed in order to ascertain the time at which reaction has initiated. Since the reaction proceeds with considerable vigor, the time when it initiates may be established when the bomb begins to vibrate. After a proper time has elapsed from the time of reaction initiation, the bomb is tapped. Sutlicient time before tapping should be allowed to permit the reaction to subside and the metal to separate but if too much time is allowed the metal will cool excessively. The exact time for pouring will vary with the apparatus used and theV size of the charge. However, with bombs of a size sufficient to produce from 50 to 20() pounds of uranium, it is advantageous to tap the bomb from 45 to 240 seconds after reaction initiates.

During reaction same pressure develops in the reactor particularly when a relatively volatile metal such as magnesium is used as the reducing metal. Where such pressure is developed, it is advantageous to tap the bomb bcfore cooling has occurred to a point such that this pressure has disappeared.

The bomb may be tapped by removal from the soaking pit and placing the bomb upon the mold as shown The bomb may be transferred by means of a traveling crane (not shown) which lifts the bomb by means of a hook 41 attached to the crane and inserted through the eye 43. The bomb i-s thus moved to a point above the mold and suspended so that holes 34 in the end plate 35 in the tiange 7 of the jacket are above the upright rods 33. The bomb is then lowered and guided into place by the rods 33 which tit into the holes34 so as to center the bomb properly over the mold. As the bomb is lowered the skirt 10V contacts the graphite cone plate 3 which is beveled at the edges indicated at A so as to cause the skirt edges to slide olf the beveled edge and center the skirt about the plate. Upon further lowering of the bomb, the hemispherical head 20 engages the conical sprue-ll. Because of the curved contour of the head it readily forms a sealed joint with the conicalspruc even though exact centering of the bomb is not achieved. Further lowering of the bomb moves the valve upward-ly until the ports 17 are opened and metal flows into the mold.

Fig. 1 shows the details of the suggested water cooled mold 2 which' comprises a stand 36 which supports on a platform 37 a centrally located castingchamber 38 surrounded by passages 39 for `a coolant. The coolant is introduced into the passages 39 by an inlet pipe 44 through the platform 37. The coolant running from one passage to another is discharged into an outlet pipe 4S. The top of the casting chamber 38 is open and the cone plate 3 rests on the rim 46 formed above the Water passages 39 around the chamber 38 and preferably is securely anchored to the mold by suitable means (not shown). Such anchoring is necessary when high pressures are developed in the bomb since these pressures tend to raise the cone plate 3 from the mold thus permitting escape of the metal. The sprue 11 is centrally positioned over the chamber 38 and the molten metal ilows through the sprue 11 into the chamber 38 Where it is chilled and sets in the form of an ingot.

The bomb 1 is ordinarily removed from the mold 2 at the end of 15 minutes and the cooled ingot of purified metal is removed from the mold for finishing.

The invention is particularly concerned with the production of uranium metal by reaction of magnesium or calcium with UF4. However, it may be applied to other bomb processes wherein a liquid product is produced. For example,' other metal halides such as beryllium fluoride, beryllium chloride, thorium iiuoride, or thorium fluoride, mixed with zinc chloride, beryllium chloride, manganese chloride, bismuth chloride or other metals capable of alloying or mixing with thorium metal to form a mixture melting below thorium metal, may be reacted with a more electronegative metal such as sodium, potassium, calcium or magnesium. Various halides including uorides, chlorides ofr bromides of metals below magnesium in the electromotive series may be reacted With a metal more electronegative than the metal of the halide in accordance with this invention.

A wide range of substances may be cast or poured by the above method and apparatus and while the specific example has been illustrated by the casting of reduced metal from a reduction reaction bomb, this may be applied to the casting from any container. The manner, as described, of opening and closing the ports will suggest various ways by which sliding the spout may open and close the valve assembly. The particular arrangement of the housing, spout, ports and the mold shown and described herein has been adopted for convenience. It will be apparent to those skilled in the art that various modications can be made without departing from the 6 principles of the invention as disclosed herein and for that reason, it is not intended that it should be limited other than by the scope of the appended claims.

What is claimed is:

1. A method of forming billets of metal comprising the steps of reacting metal halide with a reducing metal of the group consisting of alkali and alkaline earth metals while excluding air, establishing a temperature in said reaction mixture to form said metal in the molten state and develop superatmospheric pressure and maintaining said temperature and said pressure until the metal has separated from the fluoride formed of the reducing metal, tapping to permit outow of molten metal while still maintaining said temperature and said pressure, and cast. ing the tapped metal While excluding air and other uids.

2. A method of preparing metal which comprises reacting a metal halide with a metal more electro-negative than the the metal of the halide While excluding air at a temperature at which molten metal is formed and a superatmospheric pressure is established and tapping to permit separation and start outiiow of molten metal within seconds after reaction has initiated while still maintaining said temperature and said exclusion of air.

References Cited in the iile of this patent UNITED STATES PATENTS 319,779 Billings et al. June 9, 1885 460,575 Grace Oct. 6, 1891 717,840 Goldschmidt Jan. 6, 1903 1,106,384 Hughes Aug. 11, 1914 1,126,079 Queneau Ian. 26, 1915 1,218,412 Kissock Mar. 6, 1917 1,292,582 Coulson Ian. 28, 1919 1,540,515 Cuenot June 2, 1925 1,566,215 Kaufmann Dec. 15, 1925 1,637,619 Lucas Aug. 2, 1927 1,645,011 Kinney Oct. 11, 1927 1,899,506 Hutt Feb. 28, 1933 2,024,132 Sander Dec. 10, 1935 2,127,239 Stoody Aug. 16, 1938 2,310,766 Dornauf Feb. 9, 1943 FOREIGN PATENTS 18,628 Great Britain of 1913 230,865 Great Britain Dec. 10, 1925

Claims

1. A METHOD OF FORMING BILLETS OF METAL COMPRISING THE STEPS OF REACTING METAL HALIDE WITH A REDUCING METAL OF THE GROUP CONSISTING OF ALKALI AND ALKALINE EARTH METALS WHILE EXCLUDING AIR, ESTABLISHING A TEMPERATURE IN SAID REACTION MIXTURE TO FORM SAID METAL IN THE MOLTEN STATE AND DEVELOP SUPERATMOSPHERIC PRESSURE AND MAINTAINING SAID TEMPERATURE AND SAID PRESSURE UNTIL THE METAL HAS SEPARATED FROM STHE FLUORIDE FORMED OF THE REDUCING METAL TAPPING TO PERMIT OUTFLOW OF MOLTEN METAL WHILE STILL MAINTAINING SAID TEMPERATURE AND SAID PRESSURE, AND CASTING THE TAPPED METAL WHILE EXCLUDING AIR AND OTHER FLUIDS.