US3225398A

US3225398A - Bottom pour furnace

Info

Publication number: US3225398A
Application number: US159412A
Authority: US
Inventors: Davey Norman; Aldersley Kenneth
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1960-12-19
Filing date: 1961-12-14
Publication date: 1965-12-28
Anticipated expiration: 1982-12-28
Also published as: GB928434A

Description

Dec. 28, 1965 DAVEY ETAL BOTTOM POUR FURNACE 2 Sheets-Sheet 1 Filed Dec. 14, 1961 FIG. 7.

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il W /A 1965 N. DAVEY ETAL BOTTOM POUR FURNACE 2 Sheets-Sheet 2 Filed Dec. 14, 1961 .II n (M United States Patent 3,225,398 BOTTOM POUR FURNACE Norman Davey, Newbury, and Kenneth Aldersley, Reading, England, assignors to United Kingdom Atomic Energy Authority, London, Engiand Filed Dec. 14, 1961, Ser. No. 159,412 Claims priority, application Great Britain Dec. 19, 1960 7 Claims. (Cl. 2284) This invention relates to bottom pouring furnaces for the handling or casting of molten material.

Many practical difiiculties have accompanied the use of bottom pouring techniques. One difficulty has been to find some method of stopping the pouring opening of the charge container so that there is no leakage and also that there is no interference with the flow of molten material through the pouring opening.

One very common system uses a stopper rod positioned in the charge container and movable to close and open the pouring opening. The closure is not always effective since it depends on good line contact between the stopper rod and the wall of the pouring opening. Furthermore it is normally necessary to restore the seating after each pour, a procedure which is both difficult and expensive. In addition to this the rod obstructs the centre of the charge container and makes charging and stirring difiicult.

Another known system involves the use of a pushout plug. The plug is seated in the pouring in the pouring opening and can be pushed upwards by a lever mechanism to open the pouring opening. It is necessary to regrind the mating surfaces or to fit a new plug after each pour. The lever mechanism obstructs the fiow of material and gives erratic feeding to the mould. Furthermore with this system it is extremely difficult to stop the flow of material once it has started.

A system which is free from leakage trouble but which can be used only once involves the use of a melt-out plug. The plug has a composition such that contamination is minimized. The plug is melted and allowed to mingle with the materal being poured. It can be readily seen that this system does not allow interrupted pouring.

A water-cooled pouring opening has been proposed in some cases. In this instance the melt in contact with the water-cooled opening solidifies and forms a seal. Difficulties are numerous with this system. It appears to be necessary to leave a gap between the charge container and the mould and this results in turbulent pouring which gives porosity in the casting. Interrupted pouring is almost impossible. Water-coOling is dangerous if the melt is reactive, and it introduces a steep temperature gradient which gives a great thermal strain in most refractory materials.

Another system which has been proposed involves the use of a thin metal disc which is secured over the pouring opening. The disc is pierced when pouring is to be begun. The system gives irregular pouring since the pierced disc has an irregular opening. It also increases the possibility of entrapment of gas in the mould. Furthermore, the piercing mechanism forms a most undesirable obstruction.

A sliding pouring gate has been proposed in the past. In this system a slide is made to bear against the exterior surface of the charge container. The slide is moved backwards and forwards as required. In this system the maintenance of adequate sealing pressure requires special means and careful maintenance.

An object of the invention is the provision of a bottom pouring furnace having a charge container which is simple in construction, reliable in operation, easily maintained, and substantially free from leakage problems and which can enable the use of interrupted pouring techniques.

A further object is the provision of a charge container having a pouring opening whose surfaces can be easily restored after use.

The invention consists in a bottom pouring furnace having a charge container with a pouring opening in its base, a support pad for the charge container, said pad having a pouring opening, the charge container and the support pad being movable relative to each other so as to bring their pouring openings into and out of alignment.

The charge container bears down on its support pad and the weight of the charge increases this pressure and assists the maintenance of a leak-proof seal.

The absence of any leak in normal cases is a surprising feature of the invention. It is thought that the surface tension of the molten charge restricts the flow of the charge through any narrow gap which might remain between the exterior of the charge container and the support pad.

In a preferred form of the invention the charge container and the support pad are rotatable relative to each other, thereby avoiding undesirably high forces when pouring is to be begun or ended.

It is preferred that the support pad should be a cup and that the charge container should fit therein. It is a simple matter to rotate the charge container on the support pad when pouring is to be carried out.

The cup may have more than one outlet as desired. Thus by adapting the charge container so that it can be rotated in a stationary cup having more than one outlet, each positioned over a separate charge receiver or mould, it is possible to form a succession of castings from a single charge Without running into leakage difficulties.

The effect of molten material on the outlet of a bottom pouring furnace is normally to roughen and pit the surface. In the types of outlet used before the invention, this was a serious problem and it was normally necessary either to take elaborate precautions to protect the outlet or to replace the outlet at frequent intervals. In the invention, on the other hand, it is merely necessary to rub the surfaces of the charge container and the support pad to improve the surface finish. The condition of the inside walls of the outlets is of no significant importance.

It has been found convenient to provide the cup with an expendable floor or liner. This can be removed and thrown away as desired or can be treated to restore the surface round the pouring opening.

The charge container and pad may be made of standard materials. It has been found, for example, that magnesia, graphite, tantalum, or mild steel can be used. Graphite is preferred.

The charge container may be composed of refractory material lined with a suitable metal, or vice versa.

The restoration of the surfaces of the charge container and the pad is easily accomplished by the use of emery faced plates. Graphite is best treated with a fine grained emery.

The pad may, if desired, be made of thick material and form a mould header.

Embodiments of the invention are illustrated in the accompanying drawings in which:

FIGURE 1 is a section showing a cylindrical charge container in a cup-shaped support pad, the container pourin opening being closed;

FIGURE 2 shows the system open;

FIGURE 3 shows a cup-shaped support pad having an expendable floor liner;

FIGURE 4 is a sectional elevation of a bottom pouring furnace particularly suitable for use in alloy development;

FIGURE 5 is a perspective drawing of part of FIG- URE 4; and

FIGURE 6 is a section of a charge container and support pad for multiple pouring.

In FIGURES 1 and 2 a charge container 1 has a pouring opening 2 and rests in a cup-shaped support pad 3 having a pouring opening 4. The charge container 1 has 3 a slot (FIGURE 1 only) for allowing rotation of the charge container in the cup.

In FIGURE 3 reference numerals 1 to 5 have the same signification as in FIGURES 1 and 2. A liner-floor 6 is fixed to cup 3 by screws 7. The liner 6 has a pouring opening 8 aligned with pouring opening 4.

In FIGURE 4 a bottom pouring furnace has a base 9 to which is fixed by brackets 10 an asbestos chamber 11 sub-divided by a floor 12 fixed by brackets 13. Pins 14 hold cup 3 in place. The mould crucible 15 is positioned beneath pouring opening 4 of cup 3.

A peg 16 engages slot 5 and is mounted on a ring 17 which itself is pivotally mounted on bars 18. A handle 19 is pivotally mounted on a swinging-arm 20 which itself is pivotally mounted on a bracket 21 so as to rotate about a vertical axis, passing up the centre of a square pin 22. The square pin engages a square hole in a cross bar 23 which is pivotally mounted on bars 13 and has a corresponding cross-bar 24 pivotally mounted on a pin 25 supported by a bracket 26.

An induction heater coil 27 surrounds the charge container 1.

In FIGURE 5 the cross-bar arrangement can be better seen. Cross-bar 23 has a square hole 28 for engaging pin 22 and cross-bar 24 has a pivot hole 29 for engaging pin 25. Ring 17 is mounted on bars 18 by arms 30 and pivot bearings 31.

In FIGURE 6 charge container 1 has additional pouring opening 2A and cup 3 has additional pouring opening 4A by allowing multiple pouring.

The apparatus described above has been successfully used up to 1000 C. and there is no reason to think that it could not be used at higher temperatures. It has been capable of carrying out ten or more casting operations with a light metal such as aluminum and with a heavy metal such as lead. It has also proved successful with uranium. After a number of pourings pitting of the surfaces is observed but this pitting does not appear to cause any significant leakage.

The extent of penetration of metal between the cup and the charge container can be observed by the traces left by the metal and when the penetration spreads undesirably far then it is time to restore the surfaces by rubbing with emery plates.

In an example of the use of the bottom pouring furnace, lumps of metal in proportions to form an alloy were placed in the charge container and the temperature raised above the melting points of the metals. Stirring was carried out continuously. When sufiicient mixing had occurred and it was desired to cast the alloy, the charge container was rotated to bring the pouring openings in the cup and the charge container into alignment and a portion of the molten material was allowed to fall into the mould. When the desired quantity of molten material had run through the pouring openings, the charge container was rotated again to bring the pouring openings out of alignment thereby bringing pouring to an end. The material in the mould was allowed to solidify and was examined. It was felt that the proportion of one of the constituents should be increased slightly and so a further quantity of the constituent was added to the molten mixture in the charge container. A portion of the new alloy material was cast in a fresh crucible and was examined.

It can be appreciated that such operations are rendered extremely simple by the use of the invention.

We claim:

'1. A bottom pouring furnace, comprising a charge container with a pouring opening in its base, a support pad for the charge container, said pad having a pouring opening, the charge container and the support pad being movable relative to each other so as to bring their pouring Openings into and out of alignment, said charge container having a smooth-surfaced lower base, said support pad having a corresponding smooth surface, whereby the weight of material in said charge container forces said two surfaces into sealing engagement.

2. Apparatus as set forth in claim 1, further comprising means for limiting said relative movement to rotatable relative movement between said support pad and said charge container'about a fixed point, said pouring openings in said charge container and said support pad being located equidistant from said fixed point.

3. A bottom pouring furnace as claimed in claim 2 in which the pad is a cup having a fiat internal bottom surface and the charge container rests therein, the walls of said cup and said charge container being substantially corresponding right circular cylinders.

4. A bottom pouring furnace as claimed in claim 3 in which the support pad has a plurality of pouring openings positioned to be alignable in turn with the pouring opening of the charge container.

5. A bottom pouring furnace as claimed in claim 3 in which the support pad and the charge container each have a plurality of pouring openings positioned to be alignable to provide multiple pouring.

6. A bottom pouring furnace, comprising a charge container having a pouring opening in its base, a support pad for the charge container, said pad having a pouring opening, means mounting said charge container and said support pad for rotatable relative movement about a fixed point, said pouring openings being located equidistant from said fixed point, the bottom surface of said charge container and the upper surface of said support pad being flat, a flat expandable liner fixed to said support pad and having an opening coinciding with the pouring opening in said support pad, said charge container resting on said expandable liner and being forced into sealing engagement therewith by the weight of material in said charge container.

7. In a bottom pouring furnace, a charge container in the form of a right circular cylinder with a pouring opening at its base, a stationary support pad for said charge container, said support pad being in the form of a corresponding right circular cylinder and embracing said charge container so as to permit said charge container to be rotated about the longitudinal axis of said support pad, said support pad having a pouring opening in its bottom, said pouring openings being located equidistant from the longitudinal axis about which said charge container is rotatable, the bottom external surface of said charge container and the bottom internal surface of said support pad being smoothly flat, whereby the weight of material in said charge container forces said two surfaces into substantial sealing engagement.

References Cited by the Examiner UNITED STATES PATENTS 329,491 11/1885 Berge 2284 1,507,852 9/ 1924 Pleukharp et a1 2284' 2,762,095 9/ 1956 Pemetzrieder 2279 3,014,432 12/ 1961 Murarsheed 266-38 FOREIGN PATENTS 165,292 2/ 1950 Austria. 611,024 10/ 1960 Italy.

WILLIAM J. STEPHENSON, Primary Examiner.

RAY K. WINDHAM, MICHAEL V. BRINDISI,

Examiners.

Claims

1. A BOTTOM POURING FURNACE, COMPRISING A CHARGE CONTAINER WITH A POURING OPENING IN ITS BASE, A SUPPORT PAD FOR THE CHARGE CONTAINER, SAID PAD HAVING A POURING OPENING, THE CHARGE CONTAINER AND THE SUPPORT PAD BEING MOVABLE RELATIVE TO EACH OTHER SO AS TO BRING THEIR POURING OPENINGS INTO AND OUT OF ALIGNMENT, SAID CHARGE CONTAINER HAVING A SMOOTH-SURFACED LOWER BASE, SAID SUPPORT PAD HAVING A CORRESPONDING SMOOTH SURFACE, WHEREBY THE WEIGHT OF MATERIAL IN SAID CHARGE CONTAINER FORCES SAID TWO SURFACES INTO SEALING ENGAGEMENT.