US2873491A - Apparatus for casting metallic articles - Google Patents

Description

5 Sheets-Sheet 1 J. B. BRENNAN Feb. 11, 1,959

APPARATUS FOR CASTING METALLIC ARTICLES Filed May 2, `1955 5 Sheets-Sheet 2 INVENToR. JOSEPH B. 8PM/NAN Feb- 17, 1959 J. B. BRENNAN APPARATUS FoR CASTING METALLIC ARTICLES Filed may 2. 1955 Arme/Vers J. B. BRENNAN APPARATUS FOR CASTING METALLIC ARTICLES Feb. 17, 1959 5 Shets-Sheet Filed May 2, 1955 f7 MOV wml wmv

Feb. 17, 1959 J. B. BRENNAN 2,873,491

APPARATUS FOR CASTING METALLIC ARTICLES Filed May 2, 1955 i 5 sheets-sheet 5 f T-:I- l l La 't INVENTOR. JOSEPH B. @EEA/IVAN JmpA/EYS United States Patent O APPARATUS FOR 'CASTING METALLIC ARTICLES Joseph B. Brennan, Cleveland, Ohio; Helen E. Brennan, executrix of said Joseph B. Brennan, deceased Application May 2, 1955, Serial No. 505,099

1 claim. (cl. zzs7.z)

The present invention relates generally as indicated to a method andapparatus for casting, the present application being a continuation in part of my copending applications Seriall Nos. 225,949 and 406,809, filed May 12, 1951, and January 28, 1954, respectively, the former having issued as Pat. No. 2,716,790.

It is one object of this invention to provide an apparatus and method for economically, rapidly, and accurately producing, either continuously or successively, castings or laminated products in which the cast material is applied to a liner or the like in the mold cavity.

Another object of this invention is to provide a casting method and apparatus which involves relative movement of moltenmaterial supply means and mold-cavity forming means for bringing the latter into communication with a pool of molten material in the former while the material is under the influence of a vacuum, whereby air and gases are withdrawn from the cavity to facilitate theflow of the molten metal thereinto. l

`It is another object of this invention to provide a castingmethod and apparatus in which the mold cavity is successively communicated withv a vacuum chamber and with a molten material supply whereby the mold cavity is `first evacuated and then filled with the molten material. 1

Another object of this invention is to provide an apparatus and method for casting in which the `molding v material is `effectively de-gassed and de-oxidated,

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claim, the following description and the annexed drawings setting `forth in detail certain illustrative embodiments of the inventionjthese being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In `said `annexed drawings:

Fig. lis a vertical cross-section view of one form of `apparatus constituting the `present invention;

Fig. 2 is a fragmentary Vertical section similar to Fig. 1` except illustrating a modification in the mold cavity forming means;

Pig. 3 is another fragmentary vertical cross-section view illustrating a still further modification in the cold cavity forming means;

Fig. 4 is a transverse cross-section view taken substantially along the line 4-4, Fig. 3;

Fig. 5 is a vertical cross-section view of another form of apparatus constituting the present invention;

Fig. 6 is a vertical cross-section View of a vacuum casting apparatus wherein molds are shoved horizontally therethrough;

Fig. 7 is a vertical cross-section View of another apparatus wherein empty molds are loaded into a table, and are 2,873,491 Patented Feb. 17, 1959 ice carried thereby to a casting zone for filling and to an unloading zone for discharge; and

Fig. 8 is a vertical cross-section view of still another apparatus wherein vacuum-degassed molten metal flows as a thin stream and is cast into a mold in particulate form. v v

As illustrated in Fig. 1, the apparatus comprises a receptacle 1 of graphite or the like heated as by means of the high frequency heating coils 2 therearound, said receptacle being adapted to receive therein a quantity of molten material 3 therein either supplied intermittently` material 3 in said receptacle 1 is evacuated and main-` tained at a desired negative pressure as by means of the conduit 7 which leads to a suitable vacuum source, and, if desired, means may be provided on said receptacle 1 for introducing an inert atmosphere into the chamber whereby to prevent oxidation or' deterioration of the molten material 3 therein.

The chamber 6 aforesaid may be `defined by bellshaped parts 8 and 9, of which the latter preferably surrounds the receptacle 1 so that the exterior of said receptacle is not exposed to the atmosphere, said parts 8 and 9' being made from heat-resistant glass, aluminum oxide, silicon carbide, or equivalent material.`

The spiral trough 4 is so formed that `the material flows as a thin layer therealong; and, as shown, said trough may have projections to produce a sort of Weir which would exposethe molding material, suchas copper, for example, to the graphite of which the trough is preferably made. By so exposing the molten material tothe vacuum, de-gassing and deoxidation is effected very effectively. Of course, a gas permeable carbon or like tube may be substituted for the trough 4 to spread out` the molding material after it is introduced into the vacuum chamber.

While the heating coils 2 and5 are herein shown within the parts 8 and 9.surrounding the receptacle 1 and trough 4, either one or both may be disposed eXteriorly of said parts 8 or 9 or located elsewhere within said parts other than in surrounding relation to the receptacle and the trough.

Extending vertically through said receptacle 1 is a guide tube 10, also of graphite or the like, provided with cooling means 11 around the lower end thereof, almolten material inlet passage 12 below the level of the pool 3 in the receptacle and another passage 13|` therethrough communicating with the vacuum chamber 6. The vacuum chamber cover 8 may be sealed to the guide tube 10 as by means of the conventional O-ring 14 or other suitable packing means.

Other packing rings are disposed adjacent the upper and lower ends of said guide tube 10 operative to sealingly engage the molds 15which are adapted to be moved downwardly through the guide 10, said molds 15 being inserted from the top and pushed downwardly to successively communicate the sprues 16 thereof with the passages 13 and 12 in the guide 7 whereby, as each mold 15 is positioned or passed in register with the passage 13, the mold cavity therein is evacuated, and when each mold is in register with the passage 12, molten material will run into the evacuated cavity and thereby completely till the same. As the filled molds 15 pass downwardly, the material therein is cooled and solidified by the cooling means 11.

aereas@ It is to be notedrthat the sealing rings adjacent the upper and lower ends of the guide 'serve to cause the mold sections therebetween to be pressed together as by the differential pressure, that is, atmospheric pressre acting'on the end molds 1 5 land vacuum in betweeny successive molds. Still other packing rings are disposed between tube 10 and receptacle land between said receptacle and the surrounding part 9. In order to permit use of packing rings of rubber-like material without melting, the parts are cored where necessary for circulation of coolant such as water.

The molds 15 just described may be of the type described n detail in the aforesaid copendi'ng application and as disclosed in my Patent No. 2,530,853, dated N'ovember 21, 1950.Y Briefly,` however, the mold cavities may be formed in the molds by a process similar to the well known' lost wax process, that is, embedding a meltable,`c ombustible, o-r volatile model ina body of zirconium oxide, molding plaster, core sand, molding sand binders, carbon, or the like', whereby upon disposal of the model, an accurate mold cavity is left without any parting lines or the like. Also, if desired, only a portion Iof the model may be made of such meltable, combustible, vor volatile material whereby the non-meltable, non-combustible, or non-volatile portion of the Vmodel will remain in the mold body for casting of the molten material 3 thereagainst to form a laminated product.

VIn order to prevent exposure of the exterior surface of the upper end of tube 10 from the atmosphere and to effect a vacuum seal, a surrounding shell 17 may be provided made of a material the same or equivalent to that of the parts 8 and 9.

` If desired, a vacuum bell may be provided on the bottom and top of tube 10 so that the casting could be removed while under vacuum and also so that the investment mold could be introduced while under vacuum.

"It i's'to be understood that the particular mold 1S herein 'illustrated is to be regarded as merely typical andy that, for example, adjacent molds 15 may define cavities therebetween with sprues and gates leading from the exterior of the molds to such cavities.

The modification of theV invention illustrated in Fig. 2 comprises adjacent mold sections 20 adapted to be forced through a guide 21 and to have the molten material 22 flowed into mold cavities defined between the adjacent and interfitting mold sections 20. Here again, the mold v member may be of any desired cross-section shape; and, if desired', the molten material 35 may be cast therearound as a continuous sleeve or sheave and then stripped from the rod-like member as disclosed in my copending application Serial No. 147,466, filed February 18, 1950. In this connection, it is to be noted further that, if desired, the cast sheave may become a permanent part of the krod-like member 30, thereby forming alamcavities successively communicate with the vacuum chamber 23 and with the pool of molten material 22 through the passages 24 and 25 respectively, and, asY aforesaid, any portion of the mold cavity may be lined with a material having a' higher melting point than the temperature to which the molten'pool 22 is heated, whereby a laminated product may be produced.

In the modification of the invention illustrated in Figs. 3 and 4, the mold cavity forming means comprises a rodlike' vmemberv 30, either continuous or composed of adjacentSectiOns and preferably of rectangular cross-section as shown, and a guide 31 having'sealedengagement with the rod-like member at the upper" end. The guide 31 is formed with passages 32 and 33 respectivelyvcommunicating thev mold cavities defined between the guide 31 `and the rod member 30 with the vacuum chamber 34 and with the pool of molten material 35.

In the particular assembly shown, the guide 31 is formed with a plurality of guide ribs 36 engaging the f corners of the rod-like member 30 and thereby defining four strip-like cavities 37, whereby as the molten material flows into such cavities and solidifes therein as the rod 30 and adjacent material pass through the cooling zone'ot` the guide 31, there" will be produced a plurality of'at strips which may be removed from the rod-like member 30 and'further processed as by rolling or other treatment yor simply coiled or otherwise' bundled without such further treatment. l

In the modification illustrated in Fig. 3, the rod-like inated product.

In the forms of the apparatus shown in Figs. 2 and 3, the lower ends of the guides21 and 31 will preferably be provided with'packing rings 14 such as illustrated in Fig. l for making sealed engagement, in Fig. 2 with the exterior surfaces of the mold sections 20 and the castings formed between adjacent sections, and in Fig. 3 with the external surface of the cast strips 37 or like cast parts.

With further reference to Figs. 3 and 4, while the ribs 36 lare shown as being part of the guide member 31 to define cavities 37 for casting strips, it will be apparent to those skilled in the art that such ribs may be provided by longitudinally groovingthe exterior surface of the rodlike member 30 while having a regular rectangular opening through the guide member.

It is now apparent that, with the apparatus disclosed herein, it is possible to economically produce sound castings with great rapidity and in conformance with the mold cavities by reason of evacuation of the mold cavities to facilitate owingof the'molten metal thereinto, such evacuation withdrawing air and gases which otherwise might be trapped in the mold cavities.

While the apparatuses illustrated show special passages 13, 24, and 32 in the guide means 10, 21, and 31, respectively, for communicating the cavity with the vacuum chambers 6, 23, and 34, it can be Aseen that, by'maintaning the pool of molten metal under vacuum, the gases in the mold cavities andV in thernolten metal pool will bubble through the molten material to permit de-oxidation and flow of the molten material thereinto by gravity. Moreover, because the molding material is caused to ilow into the receptacle 1 and into the vacuum chamber 6 (or 23, or 34, as the case may be) as a thin layer, the same is more effectively de-gassed and de-oxidized.

In order to effectively de-gas the molten metal 3, the pressure in the chamber 6 (or 32 or 34) should be about l mm. of mercury or less, preferably 500 microns. The de-'gas'sing operation is further rendered more complete and rapid by reason of the exposure of the metal to vacuum while in particulate form as it drops into "the vacuum chamber and onto the trough 4 and asV it further drops through the Vacuum chamber in particulate form from the trough 4 into the pool of metal 3Y in container-1.

Referring now to the apparatus illustrated in Fig.- 5; there is shown therein an elongated conduit-like member 40 provided adjacent one end thereof with a feed-in opening 41 through which metal 42 in rod or bar form is adapted to be fed for melting. A vacuum port 43 is adapted to be connected to a vacuum pump or the like to maintain a pressure of about 1 mm. of mercury within said member 40. The member 40 `is preferably made of ceramic material which may be graphite coated with silica or other ceramic material, and surrounding said member is a high frequency induction heating coil 45. In this way, corona is eliminated.

As the rod 42 is melted, the metal in droplet or particulate form drops down into the shallow pool of metal in the member 40 and is thereby effectively de-gassed. Moreover, as the molten metal flows in the member 40 as a relatively shallow stream, gas bubbles are withdrawn by the vacuum.

Extending vertically through the other, enlarged end of said member is a mold guide member 46 formed with an opening or openings 47 above the metal level corresponding to openings 13 in Fig. 1 for evacuating the cavities in molds 4t; as the latter are shoved down and register with openings: 47. Said;v guide member also formed with an opening or openings 49 below the metal,

level (corresponding to openings 12 in Fig. 1) through whichtthe degassed molten metal ows into the evacuated' the operator can `be stationed at the righthand end there-Y of away from the intense member 40.

`In the apparatus illustrated in Fig. 6, `there is a horizontally orgenerally horizontally .disposed .mold guide member 60 provided with waterlcooledHO-ring seals at its ends and through which molds 61 are adapted to-bc shoved. Surrounding said member 60 is a vacuum chamber housing 62 having aA vacuumport 63 `and a feed-infopening 64.

Inthe area of the mold guide member 60, beneath the feed-invopening 64, the member 60 is formed with an opening 65 to expose the mold cavities 67 in molds 61 to the vacuum. `The evacuated molds then pass under a molten metal container 68 having a perforate bottom from which metal drops, in particulate or droplet form, into the mold cavities 67, and even after iilling of the molds the metal is yet under the inuence of vacuum and is maintained in molten condition for a time by the high frequency coil 69. Finally, before the filled molds emerge from the guide member 60, they pass through a water-cooled section thereof to chill and solidify the metal therein.

There is also preferably a Water-cooled section of the upwardly rising heat from guide member 60 ahead of the opening 65 and a high frequency coil 70 for pre-heating the molds prior to being lled with the degassed molten metal.

In the Fig. 6 embodiment of the invention, metal slugs 71 ofA volume sufficient to ll a mold cavity 67, are

loaded into successive pockets 72 of an indexable table 73 as the pockets register with the loading opening 74. As the slug-containing pockets 72 approach the unloading opening 75, they are evacuated by the vacuum connection 76, and iinally the slugs 71 either drop down, or are shoved down by plunger 78, through opening 75 in the melting unit 79.

The melting unit here is shown as comprising a high frequency coil 80, and it has been found that the slug 71 rises up by levitation in the field and will melt without hardly touching the walls of the slug receiver 81. The melted metal drops down in particulate form in the vacuum chamber into the perforate bottom container 68 and then further drops in particulate form from the latter into the mold cavity 67 therebelow, still under the intiuence of vacuum for effective de-gassing. As in the other examples of this invention, the pressure in the vacuum chamber should be about 1 mm. of mercury or less.

The slugs 71 may, of course, be pieces of solid metal bar or may be in the form of powdered metal briquets or in any desired form, even cast metal slugs or pieces.

In the foregoing examples of this invention,. effective and rapid de-gassing of molten metal may be done in a vacuum chamber maintained at a pressure of about 1 mm. of mercury or less, and the particle size of the metal in particulate or droplet form as aforesaid` should be less than MW; and, of course, the smaller the particle size, the more elective and rapid the de-gassing.

The de-gassing operation here with with 1,@2" particles occurs instantaneously, whereas it takes 3 to 4 hours to de-gas a pool of molten metal in a container, whether solid metal is melted in the container or whether molten metal flows into the container through a pouring spout.

Even then, the ,four-hourtde-gassingina pool is not near-` ly as complete asthat achieved by my method, because the head of metalreduces the eifectiveness of the vacuum. i t i Particulate molten metal may also be de-gassed and collected in a container for casting by spraying molten metal, preferably without use` of atomizing gas, into a vacuum chamber wherein said container is located, and from the container the de-gassed metal may be discharged into an evacuated mold cavity or `into the inlet of an open-ended chilling die.

t In Fig. 7, there is shown a vacuum casting apparatus comprising a housing defining a vacuum chamber 86 in which the` casting operationis carried on. As in other forms of the invention, the molten metal in a container 87 is under the influence of vacuum and `main-` tained inmolten condition by inductionheating coil 88,1 the metal being dropped, in particulate form, onto aA spiral trough 89 and further dropped therefrom-in particulate form, into a mold 90. The` metal may 1be discharged in desired amounts from container 87 by operating the valve rod 91. `An induction heating coil 92A keeps the metal in molten condition as: it ows as a thin stream or streams along the trough 89. The molds 9i) may be made of 96% silica, for example.

After one mold 90 has been filled` with molten metal, it is carried by an indexing table 92 toward a discharge zone, and the next mold 90 is positioned under the trough 89. When the lled molds 90 register with the openings of the loading and unloading tables 93 and 94, the. iilled mold 90 drops down into an opening in the unloading table 94, and an empty mold drops into the opening of the indexing table 92 from the opening of the loading table 93.

As the unloading table indexes, the filled mold 90 therein is progressively carried to the unloading zone whereat is drops through a chilling die 95 for effecting further solidiication of the metal therein.. Usually, the metal will have congealed in the mold 90 during transport thereof by table 92 from the position underneath trough 89 to the position in register with the openings of tables 93 and 94, such congealing being eliected under influence of vacuum in chamber 86.

Driving of the tables 92, 93, and 94 may be effected as by an indexing drive assembly 96 which, through the gears 97, effects indexing of table 92 and indexing of tables 93 and 94. As evident, the tables 92, 93, and 94 may bevprovided withany desired number of circularly arranged openings.

In Fig. 8, there is shown an apparatus for vacuum casting of ingots which comprises a multi-part housing 101 forming vacuum chambers 102 in which vacuum degassing of the water-cooled ingot mold 103 and of the molten metal is effected. In the upper part of the housing assembly, there is a tilt crucible 104 into which metal to be cast is supplied as through the plugged opening at the top. When the Crucible 104 is tilted, the metal drops onto a spiral trough 105 along which it flows in relatively thin stream form and drips therefrom into a container 106.

The metal in container 106 then drips through several (for example, eight to twelve) l diameter holes in the bottom of said container into the upper end of a porous tube 107 for ilow as a thin wall tube along the inside of said tube 107. The tube 107 may be of aluminum oxide when a non-ferrous metal is being cast and of magnesium oxide when steel is being cast.

Surrounding the porous tube 107 is a high frequency induction heating coil 108 which keeps the thin tubular layer of metal in molten condition as it flows down and is degassed both internally and externally.

The metal then drips in particulate form from the lower end of tube 107 into the ingot mold 103.

In order to avoid splashing of the metal, the distance that the metal drops from tube 107 into mold 103 is preferably less than 6'?, usually 3` to 4". 'This isfael complished'b'y Vn:1ouit1tin-gthe mold 1.03 -for gradual vdownward movement las -the flling progressesso as to main tain the desired 3 to 4" distance between the metal level in mold 103 andthe lower end of tube 107.

When `the vmold 103 has been filled -with lvacuum degassedmetal and the metal therein has solidified under the influence of vacuum, the housingV assembly 101 may be `hoisted 4for removal of the mold 1103 and insertion of anempty mold. The container 104 may then be lled with metal and the housing evacuated, the `mold 103 being raised sotI1at the ,bottom thereof is spaced the desired distance below the lower end ,of tube 107.

As can be seen, vthe degassing operation is carried out effectively., and quickly. The molten metal is degassed while in ithe -tilt vCrucible 10,4, as it drops down through theivacuum chamber onto trough 105, as it flows along saidtrough, as it drips from said ltrough into container 10.6, as it drips from vthe container into the porous tube 107, as `it ows as a thin wall tube through said tube 107,

as it drips fromthe tube 107 `into vthe ingot mold 103, and while being ,solidied in the mold.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided .the lfeatures stated in the followingclaim, or the equivalent of such, be employed.

lli

I ithereforefpartieularly' vpoint out anddistinc'tly claim;

as ,my invention:`

Metal l deigassing' vapparatus comprising a vacuum charml metal feed member, heating means for melting the metal, i

and .a member alongwhichy the melted metal ows vas a thin layer andefrom` which it is discharged into said receptacle in particulate form.

References Cited `in the tile of this patentV i UNITED STATES PATENTS 493,047 simpson-` Mar. 7,1893 1,024,722 Ensslen I H -v ..;..M Apr. 30, 1912 2,253,421 13 eMare pd Aug. 19, 1941 2,625,719 Moore `V v k. l Ian. 20, 119,53 2,709,842 Findlay y l k June 7, 1955 2,713,183 Winkler Q...- Iuly 19, 1955 2,716,790 Brennan sept. 6,1955 2,734,240 ISouthern c Feb. 14, 1 956 FOREIGN PATENTS 519,656 Belgium` 4- May-30, 11953

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