US2931082A

US2931082A - Casting method and apparatus

Info

Publication number: US2931082A
Application number: US608250A
Authority: US
Inventors: Joseph B Brennan; Helen E Brennan
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-09-06
Filing date: 1956-09-06
Publication date: 1960-04-05
Anticipated expiration: 1977-04-05

Description

April 5, 1960 J. B. BRENNAN CASTING METHOD AND APPARATUS Filed Sept. 6, 1956 5 x Y MM w MN a mm m t e H m m United States Patent CASTING METHOD AND APPARATUS Joseph B. Brennan, Cleveland, Ohio; Helen E. Brennan, executrix of said Brennan, deceased Application September 6, 1956, Serial No. 608,250

5 Claims. (Cl. 22-2001) This invention relates generally as indicated to a casting method and apparatus and more particularly to a casting method and apparatus by which and with which molten metal may be continuously and efiiciently cast continuously in the form of rod, strip, wire, etc. This invention also relates to the formation of composite metal articles by continuously casting molten metal against a longitudinally moving base, such as a metal strip or the like.

The present application is a continuation in part of my co-pending applications, Serial Nos. 97,195 and 293,184, now Pat. Nos. 2,763,044 and 2,772,454,-respectively, which were filed on June 4, 1949, and on May 28, 1952, respectively, the disclosure of said applications being incorporated herein by reference so as not to require detailed illustration and description.

It is a primary object of this invention to provide a casting method and apparatus by which and with which the casting of metal may be carried out continuously and efiiciently to produce castings which have superior characteristics as such, or as the constituents of composite metal articles.

It is another object of this invention to provide a casting method and apparatus in which the casting metal is supplied into a die from beneath the level of a pool of molten metal whereby dross, or other floating impurities in the molten metal, are not cast into the die, and in which a portion of the die is longitudinally movable and thus serves to carry the metal cast thereagainst through the die, wherefrom the cast metal emerges in solid form after having been subjected to sliding or troweling action against a stationary die wall while in molten condition and while being solidified.

Another object of this invention is to provide a casting method and apparatus in which the molten metal when cast against a longitudinally moving base is keyed to the latter to insure movement thereof in unison with the base while in sliding contact with a stationary die wall.

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 claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these 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. l is a side elevation view, partly in cross-section, of one embodiment of this invention for continuously casting metal strip or the like;

Fig. 2 is a transverse cross-section view, on somewhat enlarged scale, taken substantially along the line 2-2, Fig. l;

Fig. 3 is a fragmentary cross-section view, on some- 2,931,082 Patented Apr. 5, 1960 ice what enlarged scale, showing another embodiment of this invention, wherein molten metal is cast against a longitudinally moving base strip, or the like, to form composite strip metal;

Fig. 4 is an elevation view, as viewed along the line 44 Fig. 3;

Fig. 5 is a much enlarged fragmentary cross-sectio view of the Fig. 1 apparatus and method, showing the shaping and cooling of the cast metal in the die passage defined by the moving base and a stationary die member; and

Fig. 6 is a much enlarged fragmentary cross-section view showing the diiferent stages of the casting metal when cast against a longitudinally moving base strip, as disclosed in the Fig. 3 embodiment of the invention.

Referring now more particularly to the drawings and first to Figs. 1 and 2, there is shown a ring 1 which is supported for rotation about its central horizontal axis as by the flanged rolls 2, 3, and 4, one of which is provided with gear teeth 5 meshing with teeth 6 formed on the inner periphery of said ring 1. Said ring 1 is formed with a peripheral groove 7 therearound, said groove being formed, adjacent the opposite edges thereof, with recesses or notches 8, which, as will be seen, are effective to key the casting C for movement in unison with the ring 1 through the shaping and cooling die assembly 9, presently to be described.

Disposed adjacent a downwardly moving portion of said ring is a container 10 for molten metal, said container preferably being chambered as shown for connection to a vacuum line 11 (or to a pressure line through which an inert gas at the desired pressure is supplied to act on the molten metal in said container). The molten metal is preferably introduced into the container 10 in previously degassed condition and is further vacuum degassed, as it drips in particulate form from the supply conduit 12 into the container 10. Said container 10 is provided with a partition 14, the lower end of which, forms with the container 10 a feed opening 15, through which molten metal is applied against the periphery of the ring 1 from beneath the surface of the molten metal pool whereby dross, or other impurities floating in the molten metal, are prevented from being cast against said ring.

The lower end portion of said container 10 forms with the peripheral groove 7 of said ring 1, a shaping die 16 through which the molten metal is carried by the rotation of said ring 1 in the direction indicated by the arrow.

An induction heating coil 17 associated with the container 10 heats the metal to maintain the same in molten condition in the container and in the inlet end portion of the shaping die 16, whereby the metal is given its final, accurate shape while in molten condition in that portion of the die passage which is immediately below said feed opening 15. Preferably the speed of rotation of said ring 1 is such that the feed opening 15 is full but the molten metal does not back upwardly to any appreciable extent into the space between the partition 14 and the peripheral groove 7 of said ring.

Immediately below said shaping die 16 and constituting a continuation thereof, is a cooling die 18 provided with passages 19, through which a coolant such as cold water is adapted to be circulated, so as to eifect solidification of the casting as hot-shaped above and in the casting of the metal in notches 8 form driving lugs by which the casting C is uniformly driven in unison with the ring 1, without opportunity for slippage and without tendency of pulling apart of the casting as it is slid'in contact with the stationary die wall as formed by the shaping die 16 and the cooling die lS.

After the casting C emerges from the die assembly :9, theears or lugs 20 thereon, may be machined off as by means of milling cutters 21, or the like, the casting C being continuously pulled out of the die and past the milling cutters as by drive rolls -23. Thereupon, the casting C herein shown in the form of a metal strip,.may :becut into desired lengths or may be coiled continuously.

As a specific example of the method depicted in Figs. .1, 2. and the rotary wheel 1 was madeof nitrided silicon carbide, that is, silicon carbide bonded with sili- ;-con nitride. Satisfactory results have also been obtained using a wheel 1 of aluminum oxide, graphite, and like .refractory'or ceramic materials. Said wheel 1, in one specific example, was of 30" diameter with .214" wide face and formed with a peripheral groove 3" wide and JA deep.

The receptacle 10 for molten metal, in this case aluminum, was made of the same material as Wheel 1 and -was of a size to accommodateabout 30 lbs. of the molten aluminum. The aluminum was supplied into said receptacle 10 continuously through conduit 12 so as to maintain constant level of metal therein during the casting operation. The lower end portion 16 of said receptacle 10 forming the upper inlet portion of the die was arranged to define with the wheel 1 a passage of A3 thick- .ness that tapers down to a thickness of A The wheel may be made up of sectional pieces that arefitted and fired together, with a bonding cement and ,held together, for example, as by means of ceramic screws or bolts, preferably of thesame material as said -wheel. I

When the wheel 1 was rotated at the rate of approximately 5 r.p.m. aluminum strip C was continuously produced at the rate of about 450 inches per minute, said cast strip being A thick and 3" wide. The induction coil 17 was made of O.D. copper tubing with water circulated therethrough at the rate of gallons .per .minute, the coil having 11 turns and being energized by 50 kw., 450,000 cycles current. The cars that were cast on said strip C were spaced apart about 6" and were of /8 half round form and about Ms" deep. In lieu of such cars, it is also contemplated to provide axially extending fins which can readily be removed from the vedges of the strip.

The cooling die 18 in this specific example extended about 18" circumferentially of the wheel 1, the metal .being cooled below its melting point by circulation of .water through the coolant coils19 and/or optionally spraying coolant water, or otherfluid on the strip itself .1 as it emerges from the lower end of the cooling die 18.

It has been found helpful, and desirable, to use a short above its melting point, for instance, l300 for aluminum.

After the metal begins to chill, it has .been found desirableto keep the outside surface hot and this can most easily be done by an induction coil situated near the outside surface of the casting and in the case of a die which ,is 10 to 12" long, a 450,000 cycle coil with seven turns -of A" copper tubinghas been found suitable-located about 2f away from the cooling die therebjelow.

It is to be understood that the cooling water that is =dischargedfrom the induction coilsmay be used to cool ghe-caststripby spraying such coolant against the induction coil of high frequency, for instance, 15 kw.

.4 strip so as to further cool the latter as it is withdrawn from the lower end of the die.

It is preferred to withdraw or extract a major portion of the heat from the casting from the inside surface thereof. Separate cooling coils may be employed for this purpose so as to proportion to best advantage and to get the desired smoothening effect between the outer surface of the casting C and the corresponding stationary surface of the cooling die18.

In the case of aluminum, it has been found that as long as a hot head is maintained and aslong as the surface of the casting is kept labile, two-thirds of the cooling Water may be c'irculated'through coils inside the wheel 1 and one-third through coils outside of the casting C and wheel 1. In such case, separate cooling coils have worked out satisfactorily.

The vacuum connection 11 is preferably connected to a vacuum source so as to maintain a vacuum'in the receptacle 10 equivalent to 28" of mercury, such vacuum receptacle through conduit 12 in particulate form.

The conduit 12 may be made of material similar to that of the wheel 1 and is preferably supplied with molten metal from a chamber to produce a head of at least3 p.s.i. above normal atmospheric pressure, such conduit 12 terminating as, for example, in four converging orifices 'of diameter which are effective to break up the aluminum into quite small particles of about diameter maximum which are readily de-gassed as above by the vacuum in the receptacle 10.

In the embodiment of the invention illustrated in Figs. 3, 4, and 6, there is again provided a ring 30 formed with a peripheral groove 31 and adjacent the downwardly moving portion thereof, is the container 32, shaping die 34, and cooling die 35 of substantially the same general form as illustrated and described in connection withFigs. 1, 2 and 5. The principal feature of distinction of'the Figs. 3, 4 and 6 method and apparatus is that the peripheral groove 31 of said ring 30, is of depth to accommodate the continuous metal strip S which preferably is notched or otherwise formed along its edges as indicated by reference numerals 36 so as to key thereto the molten -metal .M as cast against said strip S in the

die

34, 35.

After the composite metal strip MS emerges from the lower end of the cooling die 35, the opposite edges thereof may be trimmed as by slitting rolls 37; 37 to remove thenotches 36 and metal M therein. If such notches 36 filled with casting metal M are not objectionable, the

composite metal strip M.S need not thus be trimmed. Further operations in the manufacture, for example, of

leaded bronze, steel-backed bearings may be performed .with or withoutsuch trimming. In fact, the notches 36 maybe longitudinally spaced apart so that half bearing shells may be formed by cutting the composite strip transversely at each notch 36.

As shown in Fig. 3, the induction heating coil 38 is effective not only to maintain the casting metal M molten in the container 32 and in the feed opening 39 and therebelow, as .shown, but also is effective to heat the'strip S to plastic condition, or at least a temperature greater than the meltingpoint of the casting metal M so that the castingmetal M will firmly bond to the base metal strip S. As in Fig. 5, the cast metal M in ,therein may be similar to that shown and described with reference to Figs. 1, 2, and 5 and, therefore, the description thereof will not be repeated. For instance, withthe Fig. 3 apparatus, a composite metal strip comprising a base S of steel and a casting M of aluminum may be produced at the rate indicated for Fig. 1. Preferably, the steel base strip S is pre-heated in vacuum prior to the casting of the aluminum thereonto, such pre-heating being carried out approximately to a temperature of 1400-1500 F. This can best be accomplished by a heating coil and a vacuum chamber located above the receptacle 32. Actually, the surface of the steel base for a length of 12" will be exposed to such heating coil and will be brought up to a temperature of about 1500 F. in this zone, thus allowing about a 100 F. temperature drop by the time that the heated steel strip moves to a point opposite the feed opening 39.

In addition, the pre-heated steel S may pass through a bath of cleaning salts of known composition and if desired, said salts may be floated on top of the molten aluminum so as to contact the steel strip.

Again as before, the vacuum chamber in the receptacle 32 should be operated at about 28" mercury vacuum. In one specific example molten aluminum composition #750X (produced by the Aluminum Company of America) was applied as a layer of 30 mils thickness onto the base strip of steel, the aluminum layer being very accurate and within ,6 accuracy as the composite metal strip emerged from the lower end of the chilling die 35. In this case, as in the other case, the cast aluminum and base strip were of 3" width.

As in the other example, the key notches 36 may be spaced apart about 6" and, as evident, said notches 36 need not be formed in the steel strips, but instead may comprise notches or cavities formed in the wheel 30 itself, in which event, none of the steel strip need be machined, but only the excess aluminum that flows into the wheel recesses.

It is to be understood that numerous other bi-metallic structures may be formed by the Figs. 3, 4, and 6 apparatus. For instance, the casting metal may be a bearing alloy composed of copper and lead in which case, the induction coil 38 will be effective to keep the copper lead alloy to a temperature of 2350 F., in the case of an alloy comprising 90% copper and 10% lead.

It has been found desirable to deposit nickel powder on the steel base strip toassist in the bonding of the aluminum alloy or bronze thereto. Fine nickel powder of 100 to 200 mesh may be brushed on the steel surface and fired thereon and fused thereto as a nickel lattice work 40 (see Fig. 6) or dispersion that assists in the bonding of aluminum alloy or bronze M to the steel base strip S.

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

I, therefore, particularly point out and distinctly claim as my invention:

1. A method of continuously casting a metal which comprises feeding molten metal from beneath a surface of a pool thereof against a longitudinally moving member, carrying the metal as a laterally confined stream synchrononsly with such member through a chilling die, cooling the metal less on the die contacting surface than on such moving member, and extracting heat from the metal to solidify it as the metal is carried through such chilling die.

2. The method of claim 1 wherein the longitudinally moving member comprises a pre-heated metal strip to which the molten metal is bonded when cast thereagainst.

3.- The method of claim 1 wherein the molten metal is introduced into the pool in particulate form and is subjected to vacuum prior to casting whereby said metal is .in tie-gassed condition when cast.

4. A method of continuously casting a metal which comprises feeding molten metal from beneath the surface of a pool thereof against a longitudinally moving member, carrying the metal as a laterally confined stream synchronously with such member through a chilling die, heating the metal in the inlet end portion of such die to maintain the metal in molten condition for accurate hotshaping in such die, cooling the metal less on the die contacting surface than on such moving member, sliding such die contacting surface along the die to smooth the surface of the casting, and extracting heat from the metal to solidify it as the metal is carried through such chilling die.

5. A method of continuously casting a metal which comprises feeding molten metal from beneath the surface of a pool thereof against a longitudinally moving member, carrying the metal as a laterally confined stream synchronously with such member through a chilling die, heating the metal in the inlet end portion of such die to maintain the metal in molten condition for accurate hot-shaping in such die, cooling the metal less on the die contacting surface than, on such moving member, and extracting heat from the metal to solidify it as the metal is carried through such chilling die.

References Cited in the file of this patent UNITED STATES PATENTS f359,348 Daniels Mar. 15, 1887 441,643 Close Dec. 2, 1890 560,759 Smith May 26, 1896 2,139,215 Wasson Dec. 6, 1938 2,169,893 Crampton Aug. 15, 1939 2,242,350 Eldred May 20, 1941 2,253,421 De Mare Aug. 19, 1941 2,371,604 Brennan Mar. 20, 1945 2,383,310 Hazelett Aug. 21, 1945 2,714,235 Brennan Aug. 2, 1955 FOREIGN PATENTS 881,292 Germany June 29, 1953