US3744943A

US3744943A - Apparatus for converting miscellaneous pieces of reactive metal to a usable form

Info

Publication number: US3744943A
Application number: US00173437A
Authority: US
Inventors: H Bomberger; H Kessler
Original assignee: RMI Co
Current assignee: RMI Co
Priority date: 1970-09-21
Filing date: 1971-08-20
Publication date: 1973-07-10
Anticipated expiration: 1990-07-10

Abstract

Pieces of a reactive metal, such as titanium or zirconium, are melted on a hearth within a chamber which is evacuated or filled with inert gas. Stream of molten metal overflows the hearth and is acted on by a mechanism which disperses it into small particles. The particles solidify as pellets and/or flakes which are readily blended with sponge metal and used in making up a melting charge. Dense inclusions in the starting material sink to the bottom of the hearth and thus are eliminated from the product.

Description

United @tes Patent fiemherger, Jr. et ai,

APPARATUS FOR CONVERTING MISCELLANEOUS PECES OF REACTWE METAL TO A USABLE FORM Inventors: Howard B. Bomber-gar, .1122; Harold D. Kessier, both .of Canfield, Ohio Assignee: RMI Company, Niles, Ohio Filed: Aug. 20, 1971 Appl. N0.: 173,437

Related US. Application Data Division of Ser. No. 74,20l, Sept. 21, 1970, Pat. No. 3,646,175, which is a continuation of Ser. No. 726,400, May 3, i968, abandoned.

US. Cl 425/6, 264/8, 266/33 R, 266/34 R, 425/8 Int. CL. 32% 23/00 Field of Search 425/6, 8; 264/8, 264/9; 266/33 R, 34 R, 34 V References Cited UNITED STATES PATENTS 4/1957 Stalego 13/33 [451 ,Huiy ill), H973 3,235,243 2/1966 Taylor 266/34 V 3,597,176 8/l97i Plumat 264/8 X 3,266,789 8/!966 Henry ct al. 266/33 R X Primary Examiner-Robert L. Spicer, Jr. Attorneywalter P. Wood 57 ABSTRACT Pieces of a reactive metal, such as titanium or zirconium, are melted on a hearth within a chamber which is evacuated or filled with inert gas. Stream of molten metal overflows the hearth and is acted on by a mechanism which disperses it into small particles. The particles solidify as pellets and/or flakes which are readily blended with sponge metal and used in making up a melting charge. Dense inclusions in the starting material sink to the bottom of the hearth and thus are eliminated from the product.

11 Claims, 2 Drawing Figures Patented July 10, 1973 I 3,744,943

m/vm TORS HOWARD s. BOMBERGER JR. 5 HAROLD 0. x5551. m

Atlamey arranarns son CONVER'HHNG MESCELLANEGUS PIECES or REACTEVE METAL TO A USABLE roRIvi This application is a division of application Ser. No. 74,201, filed Sept. 21, 1970 (now U.S. Pat. No. 3,646,175), which was a continuation of application Ser. No. 726,400, filed May 3, 1968 (now abandoned).

This invention relates to an improved apparatus for converting miscellaneous pieces of a reactive metal to a form suitable for blending and usable in making up a melting charge.

As used in the present specification and claims, the term reactive metal refers to any metal which in its molten state oxidizes immediately on exposure to air. Examples are titanium, zirconium, hafnium, and alloys which have one of these metals as a base. Conventional practice in producing ingots of reactive metals is to make up a melting charge of sponge metal blended with scrap or other small pieces and any alloying ingredients, and melt the charge as an electrode in a consumahie-electrode furnace. Any piece which contains a dense inclusion, such as a carbide tool bit or a chunk of molybedenum, tungsten or tantalum, must not go into a melting charge, even though the inclusion may be very small. Such inclusions do not melt, but remain as objectional inclusions in the ingot and in finished parts made therefrom. Small pieces of scrap, such as lathe turnings and sheet clippings, are readily used in a melting charge, provided they contain no harmful inclusions and are of the proper composition to go into the ingot. Larger pieces, such as crop ends, can be welded together to form an electrode. it is difficult to make any use of (1) pieces which contain dense inclusions; (2) pieces of in-between size too large to blend with sponge metal but too small to weld; and (3) fines from a sponge plant. Such materials are disposed of at a fraction of their value as normal sponge metal.

An object of our invention is to provide an apparatus for converting miscellaneous pieces of a reactive metal of any available size or shape or containing dense inclusions to a form and quality suitable for blending and usable in making up a melting charge.

A further object is to provide a converting apparatus which produces reactive metals in the form of small pellets and/or flakes readily blended with sponge metal to form a melting charge.

A more specific object is to provide a converting apparatus in which reactive metal pieces of any available size or shape can be melted and the liquid metal dispersed mechanically so that it solidifies as small pellets and/or flakes readily used in a melting charge, while dense inclusions are eliminated.

in the drawings:

FIG. 1 is a partly diagrammatic vertical sectional view of an apparatus constructed in accordance with our invention; and

FIG. 2 is a horizontal section on line ll-ll of FIG. 1 showing a preferred form of dispersing wheel embodied in the apparatus.

Our apparatus is housed in a chamber from which we exclude gases which react with the reactive metal; that is, we may either evacuate the chamber or till it with an inert gas, such as argon. We mount a water cooled metal hearth 12, preferably copper, in the upper portion of the chamber on horizontal trunnions 113, which extend through bearings lid in the opposed side walls of the chamber. We show a mechanism 115 for tilting the hearth connected to one of the trunnions outside the chamber, and a water line it? wrapped around the hearth to provide cooling. We feed miscellaneous pieces M of reactive metal to the hearth from a bin ll'7 through an airtight chute 18 which extends through the top wall of the chamber. We equip the bin and chute with vibrating feeders l9 and 20 respectively. The chute has a pair of air locks Zll and 22, only one of which can be open at any one time. The feeders and air locks per se are of conventional construction and hence not shown in detail. We connect

pipes

23 and 2 8 to the chamber and to the chute between the two air locks, through which pipes we evacuate the chamber and chute or introduce inert gas.

The apparatus includes means for melting metal pieces which have been fed to the hearth E2. The melting means illustrated is a non-consumable electrode 26 which extends through a gas seal 27 in the top wall of chamber R0 to the vicinity of material on the hearth. The electrode may be of any suitable material, such as carbon, graphite, tungsten or water-cooled copper. We connect bus bars 23 and 29 to one of the trunnions l3 and to the electrode 26 respectively for applying electric current and producing an arc which melts pieces on the hearth in accordance with known principles. Melted metal solidifies at the hearth wall and forms a skull S which contains a pool L of liquid metal. Dense inclusions D in the feed material do not melt, but sink to the bottom of the pool and thus are eliminated from the product. Preferably we mount a refractory heat shield 30 on the electrode above the hearth to protect the top wall of the chamber. it is also apparent we could employ other melting means, such as an electron beam, a consumable electrode of the same metal as the pieces M, a plasma arc device or a hollow cathode.

The hearth 12 has an overflow 353 from which liquid metal L discharges to a dispersing mechanism below. We may tilt the hearth on its trunnions or merely allow the metal to overflow while the hearth remains upright. We show a dispersing mechanism which includes a drive motor 3d beneath the chamber floor 35., a vertical shaft 36 extending upwardly from the motor through a gas seal 37 in the floor, and a metal wheel 38 preferably copper, fixed to the upper end of the shaft. As FIG. 2 shows, the wheel is formed of a plurality of angularly spaced spokes 39 and is open at its circumference between spokes. Conveniently the vertical dimension of the wheel is about 1 to 15 inches and the diameter about 5 to 60 inches. The wheel spins at speeds of about to 3,000 rpm. Preferably we water cool shaft 36 and wheel 38 to permit continuous operation. We show a water jacket 40 and inlet and discharge lines ell and 42 for this purpose. l-leat from small wheels is removed through the shaft, but larger wheels may have internal cooling ducts. The stream of liquid metal from hearth l2 strikes the wheel intermediate its axis and circumference, as indicated at X in FIG. 2. it is also apparent we could use multiple wheels or dispersing means of other design.

As the stream of liquid metal strikes the wheel, the rapidly moving spokes 39 mechanically disperse it. The resulting dispersed particles quickly solidify in the form of small pellets P, flakes F or a mixture of the two, as illustrated. The chamber floor 35 slopes away from the shaft 1% and may carry another conventional vibrating feeder 435. An airtight exit chute 436 extends from the chamber at the low point of the floor 35 for collecting the product. Wheel 38 rotates in a direction to throw the dispersed particles toward the exit chute, as indicated by the arrow in FIG. 2. We equip the exit chute with another vibrating feeder 47 and a pair of air locks 48 and 49. We connect a pipe 50 to the exit chute between air locks, through which pipe we evacuate the chute or introduce inert gas. Preferably we cool the exit chute with water which flows through a line 51 wrapped around the chute.

When the product is a mixture of pellets and flakes, we prefer to screen the mixture to separate pellets from flakes. The pellets range in diameter from about 0.01 to 0.25 inch, while the flakes are paper thin and readily broken to any desired size. Both the pellets and flakes are readily incorporated in an electrode or other melting charge, but are best used separately. If portions of the feed material are contaminated with interstitially soluble oxygen or nitrogen, the contaminated portions are distributed through the product mass, whereby the contamination is lowered to an acceptable level. Likewise if the product picks up contaminants, such as carbon, in the conversion process, we lower the contamination to an acceptable level by blending the product with virgin metal as we make up the melting charge.

From the foregoing description, it is seen that our invention affords a simple apparatus for converting miscellaneous pieces of a reactive metal to a form usable in making up a melting charge. Heretofore many such pieces have been incapable of use and wasted. Thus our invention effectively overcomes the problem of utilizing valuable material otherwise lost.

While we have shown and described only a single embodiment of our invention, it is apparent that modifications may arise. Therefore, we do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

We claim:

1. An apparatus for converting pieces of reactive metal of miscellaneous size and shape to a form usable in making up a melting charge, said apparatus comprising:

a chamber from which are excluded gases which react with the metal;

a metal hearth supported in the upper portion of said chamber;

means for feeding pieces of reactive metal to said hearth;

means in said chamber for melting the pieces on said hearth; a cooling coil surrounding the outside of said hearth; means connected to said coil for circulating water therethrough, said coil being effective for solidifying a skull of melted metal throughout the inside surface of said hearth, which skull is adapted to contain a pool of molten metal;

said hearth having an overflow for discharging a through a wall of said chamber and air locks and a vibrating feeder carried by said chute.

3. An apparatus as defined in claim 1 in which said melting means includes an non-consumable electrode extending through the top wall of said chamber.

4. An apparatus as defined in claim 1 in which said dispersing mechanism includes a motor, a shaft upstanding from said motor, and a wheel fixed to said shaft for rotation on a vertical axis, said wheel being formed of angularly spaced spokes and being open at its circumference between spokes.

5. An apparatus as defined in claim 1 in which said collecting means includes a discharge chute extending from the bottom of said chamber, and air locks in said discharge chute.

6. An apparatus as defined in claim 1 further comprising means for tilting said hearth to permit the molten metal to overflow.

7. An apparatus as defined in claim 1 in which said dispersing means solidifies the molten metal into particles in the form of small pellets and flakes.

8. An apparatus for converting pieces of reactive metal of miscellaneous size and shape to a form usable in making up a melting charge, said apparatus comprising a chamber, a hearth within said chamber, means for feeding pieces of reactive metal to said hearth, means for melting the pieces on said hearth, a cooling coil surrounding the outside of said hearth, means connected to said coil for circulating water therethrough, said coil being effective for solidifying a skull of the melted metal throughout the inside surface of said hearth, which skull is adapted to contain a pool of molten metal, means in said chamber below said hearth for solidifying in dispersed form molten metal which overflows said hearth from said pool, and means for excluding from said chamber gases which would react with the metal.

9. An apparatus as defined in claim 8 in which the means for melting the pieces includes a nonconsumable electrode extending into said chamber.

10. An apparatus as defined in claim 8 which includes in addition drive means operatively connected with the means for solidifying the molten metal.

11. An apparatus as defined in claim 10 in which the means for solidifying the molten metal is water-cooled and turns about an axis as it is driven by said drive means.

* i i i

Claims

1. An apparatus for converting pieces of reactive metal of miscellaneous size and shape to a form usable in making up a melting charge, said apparatus comprising: a chamber from which are excluded gases which react with the metal; a metal hearth supported in the upper portion of said chamber; means for feeding pieces of reactive metal to said hearth; means in said chamber for melting the pieces on said hearth; a cooling coil surrounding the outside of said hearth; means connected to said coil for circulating water therethrough, said coil being effective for solidifying a skull of melted metal throughout the inside surface of said hearth, which skull is adapted to contain a pool of molten metal; said hearth having an overflow for discharging a stream of molten metal from said pool; a dispersing mechanism mounted in said chamber beneath said overflow for dispersing said stream into particles which solidify; and means connected to said chamber for collecting the solidified particles.

2. An apparatus as defined in claim 1 in which said feeding means includes an airtight chute extending through a wall of said chamber and air locks and a vibrating feeder carried by said chute.

3. An apparatus as defined in claim 1 in which said melting means includes a non-consumable electrode extending through the top wall of said chamber.

9. An apparatus as defined in claim 8 in which the means for melting the pieces includes a non-consumable electrode extending into said chamber.