US2140607A - Method of and apparatus for casting deoxidized copper - Google Patents

Description

Dec.'20, 1938. w. K. THOMPSON 2,140,607

-METHOD :OF AND. APPARATUS FOR CASTING DEOXIDIZED COPPER I Filed ont. 19, 1955 2 sheets-sneek 2 Patented Dec. 20, 1938 UNITED STATES PATENT oFFlcE Y Y METHOD F AND APPARATUS FOR CASTING DEOXIDIZED COPPER William K. Thompson, Woodbridge, N. J., assignor to The American Metal Company, Limited, New York, N. Y., a corporation of New York Application October 19, 1935, Seri'al No. 45,692

7 Claims.

My present inventionkrelates to a method of and apparatus for producing and casting high density degassed metals, and more particularly to producing high density deoxidized copper.

According to my present invention the copper g or other metal to be cast is melted in the ordinary` way in a conventional type furnace and degassing or deoxidation of the molten metal is effected in a suitable apparatus by the use of either gase- 10 ous or solid deoxidizing or reducing agents or oxides.

a combination of such gaseous and solid agents capable of deoxidizing metallic or non-metallic The deoxidized metal is conducted from its deoxidizing chamber through a vacuum chamber and there cast in vacuo. The method of and apparatus for carrying outmy invention will be better understood from the detailed description which follows when consideredv in conjunction with the accompanying drawings, whereinzo Figure 1 is a vertical section through a vacuum casting apparatus embodying my invention.

Fig. 2 is a similar section, partly in elevation, showing a modification of my invention suitable for continuous casting.

Fig. 3 is a fractional top plan view of the apparatus shown in Fig. 2. f

Fig. 4 is a top plan view of a removable portion of the casting ring cover of the apparatus shown in Figs. 2 and 3.

.o Referring first to Fig. 1 of the drawings the apparatus which may be termed a casting well consists of a substantially U-shaped member I Il comprising upright branches I2 and I3 which are connected at their bottoms by a deep, substantially V-shaped trough-forming portion I4.

The top of the branch I3 is formed with a lateral extension I5. which ln turn has a reversely or downwardly directed branch or arm I 6. The casting well may be constructed in any suitable 0 manner from any number of parts, and preferably as herein shown consists of an enclosing wail or steel shell I1,provided with a suitable refractory lining I8 providing numerous connecting chambers. The branch I2 at its top is 45 closed by-a refractory plug I9 having ,a funnel opening 20 therein through which the molten metal may be poured into the receiving chamber of the well from a tilting furnace or the like 2|, and a second opening 22through which extends l0 a gas supply pipe 23 adapted tobe held in' place be said to constitute al discharge spout is formed at its lower end with a thickened wall 28 having a reduced tubular extension 29 ovei which latter is axially movable a collarv30 having an annular tongue 3i on its lower face. Movement of the collar 30 over the reduced extension 29 may be controlled by a plurality of fluid-'operated pistons 32 movable within cylinders (not shown) formed and circumferentially disposed within the thickened wall 28. The top wall of the lateral extension I is formed with openings therethrough, 33 and 34, in alignment with the openings or chambers in the branches I3 and i6 respectively, and the steel shell I1 directly above the openings 33`and 34 has sight openings 35 and 36 respectively which are provided with suitable transparent material hermetically sealed within said shell. Extending through the wall of the branch I6 and communicating with the interior chamber thereof is a duct 31 leading to the atmosphere, which .duct is provided witha manually controlled vent valve 38.

Above the lateral extension I5 the apparatus is formed with a chamber 39 having a gas inlet 40 and a duct 4I provided with a manually controlled valve 42, the duct 4| leading to apowerful vacuum pump (not shown).

The molten metal, while passing through the apparatus, may be maintained in the molten state by suitable heating means; for example, the refractory linings in the branches I2, I3 and AI6 may have incorporated therein suitable electric heating elements 43, 44 and 45, respectively, while -the lateral extension I5 between the basin 26 and the refractory arch thereover may be provided with an 'electric heating unit 46 which by radiant heat will maintain the metal in the basin 26 in the molten state. The metal in the trough I4 may be maintained in the molten state by electric induction heating and said trough is formed as an electric induction furnace of the type disclosed in the Wyatt Patent No. 1,201,671, and comprises a laminated iron core having end legs 41 and a central leg 46, 'around which latter is disposed a circular primary winding 49. The central leg 46 and the winding thereon are mounted in a refractory housing I 4a which may be integral with the refractory lining of the trough-forming portion I4. and spaced therefrom -at its opposite sides to provide a V-shaped channel. This V-shaped channeln when filled with molten metal constitutes the secondary of the induction furnace and 'by a mode of circulation in which hot metal leaves and cooler metal enters the channel, the metal in the bottom of the casting well above the induction furnace will be maintained in the molten state. The specific character and location of the various heating elements, however, do not constitute the essence of the present invention.

The metal treated in the apparatus may be cast in suitable molds 50, which, as herein shown, are of the water-cooled type and consist of a Water-cooled casing 5I mounted on a stool 52,

supported in turn upon a water-cooled base plate 53. .A tongue and groove or other suitable airtight connection may be provided between the mold casing and the stool, and in order to insure an hermetic seal between the mold and the apparatus, the top of the casing 5I is formed with an annular groove 54 which is complemental to the annular tongue 3i on the collar 30, and a packingwasher 55 of suitable material may be interposed between said tongue and groove joint. Of course, a suitable packing will also be used at the joint between the casing 5I and the stool 52.

The method of casting degassed metals in accordance with the apparatus above described is substantially as follows: Starting with an empty cold furnace, a mold 50 is first placed in position, as shown, to provide an airtight seal with the branch or discharge nozzle I6. This is accomplished by properly aligning the mold, the'stool and the tubular extension of the branch I6, and moving the collar into sealing relation with the top of the mold casing by the fluid-operated pistons 32. The funnel-shaped opening 20 in the plug IS is then temporarily closed by a suitable stopper (not shown) and the air is entirely displaced from the apparatus and the mold-cavity by the admission of non-'oxidizing or reducing gas into the various chambers through the pipe 23. While this gas is being admitted the valve 42 is closed; hence, the only exit for the gas is through the duct 31, the valve 38 of which is left open. After a period of time the eiiluent gas through the pipe 31, if combustible, may be ignited, and 4in the meantime the ow of gas into the apparatus is increased by admitting gas through the gas inlet 40. After the air is entirely displaced by the atmosphere of non-oxidizing or reducing gas or the partial pressure of the oxygen remaining has been reduced to such a low value that its presence is harmless to the metal, heating of the furnace is started while continuing the iiow of gas therethrough, after which the stopper is removed from the funnel opening 2D and the gas issuing at that point is then ignited, if combustible. When the furnace reaches proper temperature, molten metal, for example copper, is then poured in a relatively fine stream from the tilting furnace 2| into the vfunnel 2II through the ame and through the upwardly moving current of gas, and the metal after filling the trough I4, will gradually rise into the branches I2 and I3. The rise of the metal in the branch I3 is Watched through the sight opening and when said metal has reachedfxa suitable level the pouring is suspended and the valve 38 and the valve (not shown) controlling the gas inlet 40 are closed. The valve 42 is thenopened, thereby subjecting the chamber 33 and the chambers or passages in the branches I3, I5 and I6, as well as the mold cavity, to the action of the vacuum pump (not shown), and establishing a gas pressure differential above the metal in the branches I2 and I3, causing the metal in branch I3 to rise and overflow into the basin 26. e metal flowing into basin 26 is spread out into a sheet of small depth. This and the retardation of mold cavity. The progress of filling the mold is watched through the sight opening 36, and when the mold is full, the casting is allowed to cool, after which the valve 42 is closed and gas is vagain admittedthrough the gas inlet 4U. Upon the admission of gas into the chamber 39 the metal Ain the branch I3 will fall, due to the lowering of the gas pressure differential in branches I2 and I3, the valve 36 is again opened, the gas issuing from the duct 31 is ignited and the pouring of metal suspended. The seal on the mold is then broken by raising the collar 30 and the mold with the casting therein is removed and replaced by an empty mold which has preferably been washed out with a non-oxidizing gas. The continual flow of gas during this change of molds protects the molten metal in the apparatus from re-oxidation. When the empty mold has been clamped in place, gas inlet 40 is closed, valve 42 is opened and the casting operation is proceeded with as described above.

In the operation of the 'apparatus as described. the vacuum in the well and mold cavity has to be built up between each casting operation. Accordingly, a vacuum pump oi' large capacity relative lto the volume to be evacuated, is required. Applicant has found that with a ratio of pump capacity to volume to be exhausted of 1:1, it would take about iive minutes to reach a vacuum of 29.8 inches of mercury, or one which would permit the gas under atmospheric pressure inthe branch I2 to support a column of copper at 2100 F. in the' branch I3 of approximately 47 inches.

In the operation above described, the molten metal in -passing through the reducing or nonoxidizing gas in the branch I2 from the level C to the level B (Fig. 1) will become deoxidized. The distance of immersion of the pipe 23 in the gas filled chamber or branch I2 can be varied at will, as it will be obvious that said pipe can be adjustably held within the packing bushing 24. However, the pipe 23 should have as great a depth of immersion as possiblewithout dipping into the molten metal.

In Figs. 2 to 4 I have shown an apparatus with which substantially continuous casting is possible. In this embodiment of my invention I employ a casting wheel which consists of a circular frame or platform which is rotatable about its axis,

said platform having upstanding parallel walls 6I, which above their bottoms are bifurcated or' double-walled, as shown at 62, to provide annulartroughs 63. Mounted on the base of the rotatable frame in definitely circumferentially spaced relation are stools upon each o'i which is mounted a water-cooled casing 66 to provide a plurality of casting molds. The top of each of the casings 66 is formed with a removable extension or top 61, the function for which will presently appear. Extending over the rotatable frame 60. and supported in airtight definitely ilxed relation to the casting well'is a casting ring cover 10 having a top j1I and depending parallel flanges 12 adapted to telescope with the up- 7l standing walls 62 of the platform and spaced depending flanges or rings 13 adapted to extend down into the troughs 63. To provide for free relative rotation between the fixed cover 10 and the movable platform 60, roller bearings 14 are mounted between the tops of the walls 6| and the under side of cover top 1i. To insure an hermetic seal between the rotatable platform and stationary cover ring a mercury seal may be provided between the depending flanges 13 and the troughs 63. If desired, the mercury may be covered by several inches of high-fiash-point oil to maintain the airtight vcondition between the elements of the casting ring and prevent evaporation of the mercury. A removable portion 16 of the cover may be provided as a means of gaining access to the interior of the casting ring to remove the cast metal from the molds after solidification. Preferably, this removable cover will be located rearwardly adjacent the casting station, thereby permitting cooling of the castings during the complete circuit of the casting ring in order to reach the casting removing station. Of course, during the continuous operation, the cover portion 15 will provide an hermetic seal for both the casting platform and the ring cover proper.

In the operation of this continuous casting process the manipulation is substantially the same as that described with reference" to the construction shown in Fig. 1 for intermittent casting, except that a complete round of billets or other forms is cast before breaking the vacuum completely between the vacuum chamber 39 and the chamber provided by the casting wheel platform and its cover. However, between casting individual billets or shapes the ow over the basin 28 is intermittently cut off by bleeding-in through the gas inlet 40 a small quantity of gas which lowers the vacuum slightly, thus causing the metal to cease flowing into the basin. However, not a sufficient loss of vacuum is permitted to greatly alter the level differential between the planes A and B. When a complete round of billets is cast the removable portion 15 of the ring cover is removed, and the removable extensions 61 are successively taken off of the molds, thus leaving the ends of the castings accessible to a set of tongs or other means by which the castings may be removed from the molds. After all of the castings have beenremoved the cover portion 15 is replaced to again seal the moldcontaining chamber, the gas 110W is increased by admitting additional gas through pipe 4U to sweep the air out of the molds and the mold-containing chamber. When the partial pressure of original air in the molds and chamber is reduced to a harmless amount, said chamber is evacuated and the procedure of casting another round is repeated.

While the apparatus hereinbefore vdescribed is primarily designed for use with gas to effect deoxidation, it will be appreciated that solid carbonaceous material, or a combination `of both solid and gaseous deoxidizers, may be employed with but slight modification of the apparatus; also, that where deoxidized metal is to be poured into the apparatus for casting, an inert non-oxidizing gas such as nitrogen may be used instead of an inflammable reducing gas. It will also be understood that while I have shown and described certain preferred embodiments of my invention, I do not wish to be limited to the details of procedure and construction disclosed, since it will be apparent to those skilled in the art that changes may be made in said procedure and construction within the range of engineering skill without departing from the spirit of the invention.

What Iclaim is:

1. The method of casting metal, which comprises displacing the atmospheric air by a reducing or non-oxidizing atmosphere in a chamber having two upright branches connected at their bottoms, simultaneously charging molten metal and a reducing gas down into one branch of the chamber until the molten metal extends up into said branches below the tops thereof and flowing the molten metal, during the charging thereof into the chamber through a current of the reducing gas moving in a counter direction to the stream of molten metal, while maintaining the reducing atmosphere above the surface of the moltenmetal in the other branch, withdrawing the reducing atmosphere from the part of the chamber in open communication with the second mentioned branch and creating in its stead in said portion of the chamber a high vacuum, and then causing the molten metal from the chamber to ow through said high vacuum into a mold exposed to said vacuum.

2. The method" of casting metal, which comprises displacing the atmospheric air by a reducing or non-oxidizing atmosphere in a chamber having two upright branches connected at their bottoms, simultaneously charging molten metal and a reducing gas down into one branch of the chamber until the molten metal extends up into said branches below the tops thereof and flowing the molten metal during the charging thereof into the chamber through a current of the reducing gas moving in a counter direction to the stream of molten metal, While maintaining lthe reducing atmosphere above the surface of the molten metal in the other branch, withdrawing the reducing atmosphere from the part of the chamber in open communication with the second mentioned branch and creating-in its stead in said portion of the chamber a high vacuum, then continuing the counter flow of reducing gas and molten metal into the first branch of the chamber whereby to cause the molten metal in the second branch to overflow said branch and flow through said high vacuum into a mold exposed to said vacuum. 3. The method according to claim 2, supplemented by the step of charging a reducing atmosphere into the vacuum chamber after the metal l -the chamber thus causing said metal in the vacuum chamber branch to discharge over a basin into a mold exposed to said vacuum until said mold is filled, then checking the flow of metal over the basin by temporarily ceasing the metal pouring and bleeding into the evacuated chamber a small amount of reducing or doxidizing gas to lower the vacuum therein while removing the filled mold and presenting an empty mold to be filled from below the basin, and then again creating a high vacuum in said portion of the chamber containing the basin and the mold, and again charging molten metal into thefirst branch of' the chamber, thereby causing the metal in the other branch to rise and discharge over the basin into the mold.

5. Apparatus for vacuum casting metals, comprising-a chamber for receiving molten metal, a rotatable casting frame carrying a plurality of molds, a ring cover for the casting frame providing an enclosing chamber for, and open to, all the molds, a vacuum chamber in open communication with both the molten metal chamber and the enclosing chamber for the molds, and means for providing an hermetic seal between the rotatable casting frame and its ring cover while permitting relative movement therebetween, said ring cover having a removable portion to permit access to the moldsl and the molds each having a removable extension or top, which, when removed, facilitates removal of the casting from the mold through the top thereof and through the opening provided by the removable portion of the cover.

6. Apparatus for casting non-oxidized, degassed metal, comprising a molten metal receiving chamber having at least two upright branches connected together at their bottoms, one of said branches at its top being open to an overflow chamber having a discharge spout leading to a casting mold chamber which is in hermetically sealed relation to the overilow chamber, a plurality of molds in said last mentioned chamber with each mold adapted to be brought into alignment with the discharge spout, and means for providing a vacuum in the overow chamber for creating a gas pressure differential in the branches of the receiving chamber whereby t0 cause the molten metal to overilow from one branch into the overflow chamber above it, and from there down the discharge spout into the molds in the casting mold chamber.

7. Apparatus for casting non-oxidized, degassed metal, comprising a molten metal receivv ing chamber having at least two upright branches connected together at their bottoms, one oi said branches at its'top being open to an overflow 1g chamber having a discharge spout leading to a casting mold chamber which is in hermetlcally sealed relation to the overilow chamber, a plurality of molds in said last mentioned chamber with each mold adapted to be brought into alignment with the discharge spout, means for charging the mold chamber and .the overflow chamber with a non-oxidizing gas, and means for providing a vacuum in the overflow chamber and in the mold chamber for creating a gas pressure differential in the branches of the receiving chamber wherebyA to cause the molten metal to overilow from one branch into the overilow chamber above it, and from there down the discharge spout into the molds in the casting mold chamber.

WILLIAM K. THOMSON.

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