US3188702A

US3188702A - Apparatus for vacuum melting and casting metals

Info

Publication number: US3188702A
Application number: US54401A
Authority: US
Inventors: Smurthwaite John William
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1959-09-21
Filing date: 1960-09-07
Publication date: 1965-06-15
Anticipated expiration: 1982-06-15
Also published as: GB921484A; ES261129A1

Description

June 15, 1965 J. W. SMURTHWAITE APPARATUS FOR VACUUM mmme AND CASTING METALS Fi led Sept. 7. 1960 4 Sheets-Sheet 1 83 ENTQ? 25V a 1m 1965 4.. w. SMURTHWAIQTE 3,188,702

APPARATUS FOR VACUUM MELTIUG AND CASTING METALS Filed Sept. 7, 1960 4 Sheets-Sheet 2 m r----j N P Q" 1.-' v LDM q Hum d- I 8 'I '1 H I H Q l LL 1: u "II n i L' b8 2- if" v g co &

BY -2., "1w

June 15, 1965 J. w. SMURTHWAITE APPARATUS FOR VACUUM MEETING AND CASTING METALS Filed Sept. '7, 1960 4 Sheets-Sheet 3 mli w MM mm a? 8 4 a? l -6 lmwmmih i r Y L NVENTOR' June-v 15, 1965 Filed Sept. 7, 1960 J. w. SMURTHWAITE APPARATUS FOR VACUUM MELTING AND CASTING METALS 4 Sheets-Sheet 4 FIG.4.

Iuvtuun 3,188,702 APPARATUS FOR VACUUM MELTING AND I CASTING METALS John William Sm urthwaite, Lea, Preston, England, assignor to United Kingdom Atomic Energy Authority, London, England Filed Sept. 7, 1960, Ser. No. 54,401

Claims priority, application Great Britain, Sept. 21, 1959,

32,046/ 59 3 Claims. (Cl. 22--73) enced in the dismantling operation due to the hazard of radiation and toxic uraniferous dust.

Apparatus according to the invention for vacuum melting and casting metals comprises heating means defining a heating cavity, a melting and bottom pouring crucible assembly in said heating cavity, a supporting structure for said heating means and crucible assembly, a casting mould to accept metal poured from the crucible, and a removable vacuum sealing envelope for the combination of heating means, crucible assembly, supporting structure and casting mould, characterised in that the crucible assembly is supported on a carrier so as to be insertable into and withdrawable from the base of the heating cavity on removal of said sealing envelope,

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings wherein:

FIGURE 1 is a sectional view of apparatus for vacuum melting and casting metallic uranium,

FIGURE 2 is a fragmentary elevation of part (designated II in FIGURE 1) of the assembly of FIGURE 1 in the same plane as FIGURE 1,

FIGURE 3 is a view similar to FIGURE 2 but in a plane at right angles to that of FIGURE 2, and

FIGURE 4 is an enlarged fragmentary section of a further part (designated IV in FIGURE 4) of the assembly of FIGURE 1 in the same plane as FIGURE 1.

Referring to the drawings, in the construction shown therein, apparatus for vacuum melting and casting metallic uranium comprises high frequency induction coils 1 defining a heating cavity 2, a melting crucible assembly 3 disposed within the cavity 2 and having a bottom pouring outlet 4, a supporting structure 5 for the high frequency induction coils 1 and crucible assembly 3, a holder 6 for casting moulds which accept poured metal, and a removable vacuum sealing envelope 7 for the combination of heating coils 1, crucible assembly 3, supporting structure Sand holder 6. An evacuation duct 63 connects a top extract hood 61 to a vacuum source. The crucible assembly 3 is supported on a stillage 8 so as to be insertable into and withdrawable from the base 9 of the heating cavity on removal of the sealing envelope 7.

In greater detail, the structure 5 is fabricated from rolled steel angle and is capped with a supporting plate 10 upon which the heating coils 1 are carried. An orifice 10a in the supporting plate 10 provides access for the crucible assembly to the heating cavity 2 from beneath. A base plate 11 of the structure carries a sealing ring 12 for engagement by the removable vacuum sealing envelope 7, and a graphite push rod 13, actuated by means of a lever mechanism 14 mounted on the sealing envelope 7, is provided to initiate pouring, aswill be more particularly referred to hereinafter. The high frequency induction United States Patent 0 coils l are housed within an annulus l8 defined by an outer sleeve 19, which serves as a screen against outwardly radiating magnetic flux, and an inner lining of refractory material, for example, monolithicrammed fireclay. The annulus 18 is closed at each end with asbestos insulating board 21 and the induction coils 1 have combined electrical power and water cooling connections 22. The crucible assembly 3 comprises a graphite crucible 23 and a tundish 27, the crucible 23 being in two parts and having a graphite cover 24 with a vent 25. In the base 16 of the crucible 23 and outlet duct 26, normally sealed by a graphite sealing plug 15, feeds into the tundish 27 which has a perforated outlet nozzle 28. The crucible assembly is capped with firebrick 29 through which extends a sheathed thermocouple 30 housed in the crucible 23, and is supported and thermally insulated by firebrick 32 interposed between the tundish 27 and the stillage 8. An orifice 33 penetrates the firebrick 32 and the stillage 8,.the latter being supported in the position shown in FIGURE 1 by two sliding bolts 35 carried in brackets 36 attached to the supporting structure 5 and shown in FIGURES 2 and 3.

The sliding bolts 35 are of rectangular cross section and carry supporting brackets 37 with adjustable feet 38 upon which the stillage 8 rests. A notch 39 engaged by a stop 40 determines the extent of sliding travel of each bolt whilst a notch 41 in combination with a pivoted lever 42 constitutes a locking device. Notches 43 in the edges of a bed plate'34 of the stillage 8 provide clearance for the feet 38 during crucible loading operations described in detail hereafter. The casting mould holder 6 is mounted on two guide rails 44 by wheels 45 and has a graphite header 46. The stops 17 are attached to the base plate 11 and arranged to efiect register of the header 46 of the holder 6 with the pouring outlet 4. Two adjustable stops 47 locate a fork lift loading truck (not shown) employed during loading operations and each rail 44 has a hinge 48 enabling it to be folded to clear the sealing ring 12. The sealing envelope 7 has

cooling water duets

49 and 49a with water connections 50 and 50a respectively and includes a sighting window 51 carried by a branch pipe 52. The lever mechanism 14 comprises a lever 53 pivoted at an end 54 and pivotally connected to striker rod 55 which is slideably carried in lugs 56 mounted on the inner wall of the sealing envelope 7, passage of the rod 55 through the top of the sealing envelope 7 being sealed by a bellows 57. The rod 55 is connected to the push rod 13 through a pivoted lever 58 and is actuated by an opera-ting rod 59 depending from the lever 53. A removable pin 60 is provided to prevent inadvertent operation. The push rod 13 on being moved upwardly serves to displace the plug 15 and initiate pouring.

The top extract hood 61 registers with the vent 25 and is connected to the vacuum source by the evacuation duct 63 (shown broken for clarity in FIGURE 1) which passes through the base plate 11, a pressure relief valve 60a be ing attached to the top of the envelope 7. Referring now to FIGURE 4, the hood 61 includes an outer container 64 having a branch 65 connected to duct 63 and is supported on the asbestos insulating board 21 by three adjustable feet 66. A graphite condensing plate 67 is located by an upper flange 68 of the hood in close proximity to the water jacket 49a and is secured to the flange 68 by a clamping ring 69 which comprises three clamps 70, 71 (FIGURE 4) and 72 (FIGURE 1) attached to a ring 73 at equally spaced intervals about its circumference, the ring 69 being clamped to the upper flange 68 by engagement of

clamps

70, 71 and 72 with clamping wedges (only one of which is shown in FIGURE 4, namely, that in engagement with clamp and designated 74) attached to the underside of the flange 68. Three slots 75 (one only of which appears in FIGURE 4) are proto FIGURE 1, leads 82 to the theimocouple 30 are accommodated in sheathing 83 and penetrate the base plate of the structure through a vacuumtight terminal box 84.

Assembly of the vacuum furnace commences with the assembly of the crucible 23, tundish 27 and

bricks

29, 32 on the stillage 8'and charging of the-crucible 23 with metallic uranium. The stillage and crucible assembly are transported by a fork lift loading truck to a position inside the base of the structure preparatory to lifting for installation inthe heating cavity; Approximate orientation of the stillage and crucible assembly 'is provided by the guide rails 44 in combination with guide members on the truck and with the stop 47 in combination with the stillage 8. The stillage and crucible assembly are then lifted by the fork lift loading truck'to a point just below that at which the top of the crucible assembly ei ters the orifice 10a of the plate 10, whereupon accurate orientation is achieved by manual adjustment of the fo'rk lift loading truck.

Lifting is then continued until the srucible is in the installed position'when the bolts are, engaged and locked.

The push rod: 13 is inserted and eipivoted lever 58 mounted on the structure 5', the vacu mpipe 63 and hood 61 are installed and the holder 6 lbcated beneath the crucible assembly pouring outlet 4. The sealing envelope 7 is lowered over'the'structure 5 and assembly 3 'to en close'them, and the envelope 7 is then evacuated via the duct 63. When the uranium metal in the crucible has been melted by the heating coils 1, as indicated by the temperature reading of thermocouple 30, the push rod 13 is actuated by the lever mechanism 14 to displace the graphite plug 15 (which floats to the top of the melt) thereby discharging, the molten uranium via thetu'ndish 27 to the moulds. After the casting operation has been completed the apparatus is dismantled in the reverse order and the crucible assembly transferred to a protectedarea where it can be'dismantled, cleaned and reassembled with adequate protection againstradiation and toxic uraniferous dust emitted by residue adhering'to the in'-' terior of the crucible and tundish.

In operation of the furnace a vapour, which isbeta ray emitting, em'anates from the crucible 23. The vapour is drawn olf via the hood 61 and in passage therethrough' it comes into contact with the cool surface of the condensing plate 67 to form a sublimate which can subsequently be removed by scraping. 'I' he condensing plate is maintained in a cool condition by its close proximity to the water jacket 49a ofthe envelope 7 and by the protection offered by the thermal baffle plate 77 "interposed between the molten mass within the crucible and the condensing plate 67. .The feet 66 are adjustable to compensate for irregularities in the upper level of the asbestos insulating board 21 whilst the sleeve 79 in resting on the firebrick29 provides closure for the joint between the hood and the firebrick.

I claimz. I

1. Apparatus-for vacuum meltingand casting of metals, said apparatus comprising means defining a cavity having an access port inthe base thereof, heati g means surrounding said cavity, a melting crucible assembly in- I thereof, closure means for said pouring opening, a sup-- 4 a port structure for said means defining a cavity and for said heating means, carrier means forsupporting'said crucible assembly, releasable securing means for securing said carrier means to said support structure so that said crucible assembly is in operative position in said cavity, said carrier means being movable when released'from said support structure for insertion of said crucible assembly into and withdrawal thereof from said cavity, a mould assembly disposable. beneath said crucible assemblyand movable transversely into and out of operable position beneath said crucible assembly a removable vacuum sealing envelope for enclosing all' of said means for defining a' cavity, said heating means, said crucible assembly, said support structure, said carrier means, and said mould assembly, and means for operating said pouring opening closure means from outside said sealing envelope and extending sealingly through an aperture in said sealing envelope.

2. Apparatus according to claim 1 and including a hood which terminates the evacuation duct means and is disin the base thereof and heating means surrounding said cavity; a melting crucible assembly in said cavity; said crucible assembly having a pouring opening in the base thereof; closure means for said pouring opening; said access port in the base of said cavity being of a size and configuration su'fiicient to enable said crucible assembly to pass therethrough; a supp rt structure for supporting said cavity means and said heating means and for defining a moulding station underneath said cavity; carrier means for supporting said crucible assemblyand closure means within the cavity and for supporting thecrucible assembly during insertion of the crucible assembly into the cavity and withdrawal therefromthrough'said access port; said carrier means being demountably supported beneath the cavity by the support structure with the crucible assembly disposed within the cavity; a transversely movable casting mould for receiving molten metal poured from said pouring opening in the base of said crucible assembly; a removable vacuum sealing envelope for collectively enclosing said cavity means, said heating means, said crucible assembly, said. support structure, said carrier means, and said transversely movable casting mould; means extending from outside to inside said vacuum sealing envelope and to below said crucible assembly for operating said pouring opening closure means to initiate pouring ofmolten metal from said pouring opening of said crucible assembly to said mould; and means for creating a vacuum in said envelope.

References Cited by the Examiner UNITED STATES PATENTS 6/3 1 Rohn. 2/33 5/55 Tama 22-84 Southern 266-34 Wroughton et al 22-84 X 33/58 Ulrech et al 22-79 X 11/ 60 Hanks 266-34 FOREIGN PATENTS 469,762 11/50 Canada.

MORRIS o. WOLK, Primary Examiner. RAY K. WINDHAM, Examiner.

Reeves -Q. 22-43-

Claims

1. APPARATUS FOR VACUUM MELTING AND CASTING OF METALS, SAID APPARATUS COMPRISING MEANS DEFINING A CAVITY HAVING AN ACCESS PORT IN THE BASE THEREOF, HEATING MEANS SURROUNDING SAID CAVITY, A MELTING CRUCIBLE ASSEMBLY INSERTABLE INTO AND WITHDRAWABLE FROM SAID CAVITY THROUGH SAID ACCESS PORT AND HAVING A POURING OPENING IN THE BASE THEREOF, CLOSURE MEANS FOR SAID POURING OPENING, A SUPPORT STRUCTURE FOR SAID MEANS DEFINING A CAVITY AND FOR SAID HEATING MEANS, CARRIER MEANS FOR SUPPORTING SAID CRUCIBLE ASSEMBLY, RELEASABLE SECURING MEANS FOR SECURING SAID CARRIER MEANS TO SAID SUPPORT STRUCTURE SO THAT SAID CRUCIBLE ASSEMBLY IS IN OPERATIVE POSITION IN SAID CAVITY, SAID CARRIER MEANS BEING MOVABLE WHEN RELEASED FROM SAID SUPPORT STRUCTURE FOR INSERTION OF SAID CRUCIBLE ASSEMBLY INTO AND WITHDRAWAL THEREOF FROM SAID CAVITY, A MOULD ASSEMBLY DISPOSABLE BENEATH SAID CRUCIBLE ASSEMBLY AND MOVABLE TRANSVERSELY INTO AND OUT OF OPERABLE POSITION BENEATH SAID CRUCIBLE ASSEMBLY, A REMOVABLE VACUUM SEALING ENVELOPE FOR ENCLOSING ALL OF SAID MEANS FOR DEFINING A CAVITY, SAID HEATING MEANS, SAID CRUCIBLE ASSEMBLY, SAID SUPPORT STRUCTURE, SAID CARRIER MEANS, AND SAID MOULD ASSEMBLY, AND MEANS FOR OPERATING SAID POURING OPENING CLOSURE MEANS FROM OUTSIDE SAID SEALING ENVELOPE AND EXTENDING SEALINGLY THROUGH AN APERTURE IN SAID SEALING ENVELOPE.