US3895672A

US3895672A - Integrated furnace method and apparatus for the continuous production of individual castings

Info

Publication number: US3895672A
Application number: US427980A
Authority: US
Inventors: Jr Robert E King; Bruce E Terkelsen
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1973-12-26
Filing date: 1973-12-26
Publication date: 1975-07-22
Anticipated expiration: 1992-07-22
Also published as: DE2451921A1; JPS5419853B2; FR2255983B1; DE2451921B2; GB1489892A; SE409560B; JPS5097523A; SE7413517L; FR2255983A1; DE2451921C3

Abstract

An apparatus and method for forming and casting metal alloys on a continuous basis in an integrated furnace system are disclosed. A highly flexible manipulator and a plurality of solidification cells are integrated in a main chamber to enable the manipulator to service all the solidification locations, each of which has the capability to control the solidification of an individual casting independent of the solidification occurring in the remaining cells. A bulk material container interfaces with the main chamber to form a melting and pouring station at the interface. Electron beam means provide high density power at controlled rates to a suitable location at which the metal alloy is melted with precision and poured from a crucible. In the operation of the furnace, the manipulator forms an assembly from a mold and a casting plate, delivers the assembly to the melting station where it is filled, delivers the filled assembly to a solidification cell where the alloy is cooled under controlled conditions and then removes the assembly to a discharge chute. The solidification process is the operation of longest time interval and while any given assembly is being cooled in a solidification cell, the manipulator is generally engaged elsewhere in the furnace system. After a vacancy has occurred in a cell, the manipulator delivers a new assembly for solidification and the furnace system is operated continuously for an essentially indefinite period.

Description

United States tet [1 1 King, Jr. et al.

INTEGRATED FURNACE METHOD AND APPARATUS FOR THE CONTINUOUS PRODUCTION OF INDIVIDUAL CASTINGS Inventors: Robert E. King, Jr., West Willington; Bruce E. Terkelsen, Cheshire, both of Conn.

United Aircralit Corporation, East Hartford, Conn.

Filed: Dec. 26, 1973 Appl. No.: 427,980

[73] Assignee:

References Cited UNITED STATES PATENTS 3/1958 Ulrech et al. 164/322 X 9/1967 Treppschuh et al.. 3,532,155 10/1970 Kane et a1 164/65 X 3,677,324 7/1972 Higginbotham et al. 164/338 X FOREIGN PATENTS OR APPLICATIONS 414,955 2/1966 Switzerland 164/6] 1,214,359 4/1966 Germany 164/258 Primary Examiner-Francis S. I-Iusar Assistant Examiner-Carl A. Rowold Attorney, Agent, or FirmAnthony .l. Criso [451 July 22,1975

[57] ABSTRACT An apparatus and method for forming and casting metal alloys on a continuous basis in an integrated furnace system are disclosed. A highly flexible manipulator and a plurality of solidification cells are integrated in a main chamber to enable the manipulator to service all the solidification locations, each of which has the capability to control the solidification of an individual casting independent of the solidification occurring in the remaining cells. A bulk material container interfaces with the main chamber to form a melting and pouring station at the interface. Electron beam means provide high density power at controlled rates to a suitable location at which the metal alloy is melted with precision and poured from a crucible. In the operation of the furnace, the manipulator forms an assembly from a mold and a casting plate, delivers the assembly to the melting station where it is filled, delivers the filled assembly to a solidification cell where the alloy is cooled under controlled conditions and then removes the assembly to a discharge chute. The solidification process is the operation of longest time interval and while any given assembly is being cooled in a solidification cell, the manipulator is generally engaged elsewhere in the furnace system. After a vacancy has occurred in a cell, the manipulator delivers a new assembly for solidification and the furnace system is operated continuously for an essentially indefinite period.

16 Claims, 6 Drawing Figures PATENTEDJUL 22 ms SHEET INTEGRATED FURNACE METHOD AND APPARATUS FOR THE CONTINUOUS PRODUCTION OF INDIVIDUAL CASTINGS BACKGROUND OF THE INVENTION 1. Field of Invention The present invention relates to the casting of metals and more particularly to a high utilization furnace system for the continuous production of metal casting.

2. Description of the Prior Art The technology which supports the melting. pouring.

cooling and related processes for metals to form a cast product has always involved a relatively high investment of capital and time per finished casting procedure. In general, a large amount of equipment is involved, the pieces of equipment tend to be expensive and the time utilization of some of the components is low.

One of the principal shortcomings common to metal casting apparatus is the limited number of pourings which can be produced with a given set of melting and pouring apparatus. In general, a relatively long period of time is required in order to melt a metal charge in a crucible and then a casting is made with a single pour from the crucible. The heating equipment and the crucible then go unused until the casting is solidified and the cycle is repeated. It is not uncommon to take up to several hours to heat a mold and melt a metal charge and an equal amount of time to solidify the resultant castin, particularly in such highly refined casting procedures as directional solidification. One technique for making better utilization of the heating and pouring equipment in a casting furnace is to use a technique as suggested by May in U.S. Pat. No. 596,897 wherein a single charge is melted in a crucible and with the aid of a rotatable pouring chute, a plurality of castings is made from a single melt in a batch process. Some of the obvious drawbacks to the May technique include the nonutilization of the melting and pouring equipment during solidification as well as the fact that the process is not a continuous one. Once the molten charge is consumed or all the molds which can be serviced by the pouring chute are filled, the equipment remains idle during solidification. Also, there is a problem of quality control since the composition of the molten material in the crucible tends to change when it is held for a period of time while several different castings are sequentially poured from a single melt.

Conceptually. one can easily improve on the utilization of the melting and pouring equipment in a casting process by simply presenting a series of suitably prepared molds to a single crucible. As each mold is filled, the casting is moved out of the pouring region and a fresh mold is presented to the crucible. As a practical matter, the implementation of the concept usually becomes cluttered with the realities of a physically cumbersome and poorly utilized physical plant. In U.S. Pat. No. 2,651,668, for example, Southern teaches a furnace system with several molds and a single melt station. Each mold is filled and hydraulically moved to a cooling area and while one mold is cooling an additional mold is filled. While the Southern teaching is directed to the specific problems of casting titanium in gots, it does represent a conceptual improvement over some of the previous slower techniques since cooling and pouring are conducted simultaneously. The Southern approach still leaves much room for improvement since there is a great deal of time during which the equipment is not being utilized when the molds are being transferred through the interlocking devices required to control the atmosphere in contact with the molten metal; the technique is relatively specific since a consumable electrode technique is used to melt the titanium.

A more conventional method of heating a charge to molten conditions is with induction heating. Induction heating is used more commonly than consumable electrode processes although a furnace requiring a vacuum or other controlled atmosphere presents the formidable problem of providing a suitable technique which will allow a single crucible melt to be tapped several times for individual molds. In U.S. Pat. No. 3,014,255, Bussard et al teach a technique in which a small tap hole is located in the bottom of a crucible, the tap having a sufficiently large surface to cause the molten material in the tap region to solidify unless an auxiliary localized induction heater is activated. With this apparatus, a number of castings can be made from a single melt with certain limitations. One of the obvious shortcomings of this technique is the absence of continuous pouring during the period required to recharge the crucible and melt the charge in the crucible.

A further improvement in the long sought ultimate goal of providing continuous casting and solidification of metal is provided by the Tingquist et al teaching in U.S. Pat. No. 3,460,604. Briefly, Tingquist et al teach the loading of a charge into one region, creating the proper atmosphere, opening the loading region to a melt region where the charge is melted and poured, and moving the casting back into the loading zone for removal from the furnace. A significant shortcoming of this method of casting is the complication and lost time caused by the number of gas tight locks which must be operated to get the raw materials in and the finished products out of the furnace. This process is described as a continuous method of melting and casting and did represent an improvement over previously used techniques but as a practical matter the batch pouring process disclosed does not make full utilization of the melting, pouring and cooling apparatus involved.

The Taylor teaching presented in U.S. Pat. No. 3,601,179 represents a great improvement in equipment utilization, particularly with respect to castings which are directionally solidified. Taylor uses a system in which a plurality of individual molding chambers is visited by a crucible of molten metal; a rail device which passes alongside each molding chamber transports the crucible and a freshly poured casting can be solidified under controlled temperature gradient conditions in each chamber. With this technique, a single charge is melted in a large crucible and a pouring is made within each chamber as the crucible is transported from one pouring station to another. The primary drawbacks to the Taylor process include the extensive amount of equipment which must be assembled to form the system, the fact that the metallurgical composition of the melt changes as the castings are made sequentially, the requirement to deliver the crucible to each station through relatively slow and massive atmosphere control lock mechanisms, and the dead time representing the intervals during which the pouring chamber is being disconnected from one molding chamber and attached to an adjacent molding chamber during which no castings are poured.

One of the best techniques for casting metals on a continuous basis is taught by Higginbotham in US. Pat.

No. 3,677,324 wherein preheated molds are delivered v to a pouring station and a suitable metal charge corresponding to the casting involved is inductively heated and poured into the mold. The mold is on a chill plate which moves with respect to the furnace and suitable temperature control of the mold environment is provided to permit directional solidification of the casting. One of the shortcomings of this process is the lack of symmetry between the heating elements and the molds. Since the heaters form two planar thermal fronts and successive molds pass essentially between and parallel to the fronts, the individual castings do not experience a symmetric temperature profile. Further, all of the essential equipment is operated in a series fashion so that the failure of any one component disrupts the operationof the entire furnace.

While several variations showing gradual improvements to the general art of metal casting have been outlined above, all of these techniques are based on crucibles made of ceramics; this is the only feasible technology compatible with the elevated temperatures involved when the cast metal is melted in the pouring utensiL'Ceramic crucibles are undesirable particularly in the casting of highly reactive metals since the ceramic tends to contaminate the pour metal thereby compromising its strength.

SUMMARY OF THE INVENTION An object of the presentinvention is to produce castings on a continuous basis with multiple solidification station furnace having a single puring station. Another object is to produce directionally solidified castings with independently controlled components which are integrated into a furnace system to permit maximum utilization of the components forming the system. Another object is to produce discrete castings in a continuous process with a single furnace system. Another object is to completely process a source of metal alloy intopa continuous supply of finished castings with an integrated furnace system which is operated essentially unattended and continuously.

According to the present invention, cast elements are continuously produced in an integrated furnace system wherein the operations are coordinated to permit a single melting and pouring station to accept a continuous supply of molds in rapid succession; the molds are preheated, mated with a casting plate, presented to the pouring station and filled with superheated liquid metal from a crucible; a predetermined quantity of the liquid metal 'is collected in the crucible by rapidly melting a controlled amount of a source metal with an electron beam; a manipulator transfers the casting plate and mold to a solidification cell wherein the molten metal is cooled until solid; the casting is removed from the solidification cell and delivered to a station external of the furnace through suitable locking means where the casting plate is prepared for recycling with a new mold.

A primary advantage of the present invention is the full utilization of the melting and pouring equipment which does not remain idle during the solidification period of a casting. Also, various solidification cycles can be mixed and even changed during the continuous operation of the melting and pouring apparatus. Further, a malfunction in a single solidification station does not force a shutdown of the entire furnace. Similarly, if a single mold is found defective. the mold can be rejected without interfering with the melting and pouring operation. The present invention has the advantages of a continuous series of discrete pourings from a single crucible, the absence of a ceramic crucible, an extremely short time requirement to melt a quantitized amount of alloy for pouring, a high rate of production of castings which have consistent metallurgical properties, and a high degree of utilization of essentially all the main components of the integrated furnace system.

A'main feature of the present invention is the manipulator which has access to a wide range of locations in the furnace apparatus and means for applying compressive loads at the end of the manipulator. The invention is characterized by a fixed pouring station. fixed cooling stations and means for pickup and delivery between these stations. Further, the casting plate used beneath each mold during casting and solidification is not cooled directly but is sized to provide an ample heat sink for the period during which the mold is filled and transported from the filling station to the solidification cells. The system is further characterized by the many solidification cells which are serviced by a single manipulator and pouring station and the fact that a vacuum or inert gas atmosphere is maintained throughout the melting, pouring, and cool-down spaces of the furnace system.

The foregoing and other features and advantages of the present invention will become more apparent in the light of the detailed description of a preferred embodiment thereof as illustrated in the accompanying draw- BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a simplified elevation view of a section through a furnace system in accordance with the present invention; 7

FIG. 2 is a simplified plan view through a section of the furnace showing solidification cells, the mold feed chute, the casting plate feed chute, the casting discharge chute and the manipulator;

FIG. 3 is a simplified cross-sectional view of a solidification unit as shown in FIGS. 1 and 2; 7

FIG. 4 is a simplified sketch of the pouring station;

FIG. 5 is a simplified sketch of the work end of a cooled manipulator; and

FIG. 6 is a simplified sketch of the gripper plate in the manipulator.

DESCRIPTION OF A PREFERRED EMBODIMENT The integrated furnace apparatus in accordance with the present invention is shown in FIG. 1; an elevation view is taken through the furnace system to show the main components which in combination form the system. A main chamber 10 which resembles a right cylinder is the central and largest component in the system. The main chamber has a generally convex lower surface 12 and a similar upper surface 14 which resist crushing when the pressure inside the chamber is reduced. Supported between the lower dome and the upper surface is a central column 16 which is concentric with the main chamber. Fixedly attached to the central column is a pair of bearings 18 on which is rotatably mounted a hollow cylinder 20 having a gear face 22 extending from its lower end and engaging a spur gear 24 which is driven by an electric motor 26.

A manipulator assembly 28 is translationally attached to the hollow cylinder to allow relative motion between the assembly and the cylinder in a vertical direction. t

A bulk material container 30 is located adjacent to the main chamber. The container includes an alloy storage chamber 32 and a melting and pouring chamber'34, the interior volumes of which are interconnected through an alloy delivery port 36; a delivery port valve is slidably mounted to permit sealing of the storage chamber from the pouring chamber 34. Similarly, the interior volumes of the main chamber and the melting and pouring chamber communicate through a pouring port 40; a pouring port valve 42 is available to isolate thesetwo chambers. Internal of the bulk material container are metal ingots 44 supported by a rotatable umbrella structure 46. A variable speed motor 48 drives an ingot feed shaft 50 having an ingot engagement fixture 52. An electron beam gun 54 is mounted on the top of the melting and pouring chamber and an observation sight port 56 is aligned to view a rotatably mounted crucible 58 which is positioned directly below the ingot feed shaft and the melting and pouring stations.

A pumping system 60 which is capable of controlling the atmosphere throughout the entire ingot container and'the main chamber and also maintain a vacuum through these spaces is connected to the main chamber and the pouring chamber. A structural beam 62 assists in supporting the main chamber.

A plurality of solidification cells 64 is positioned vertically along the outer wall of the main chamber as is shown in FIG. 1. The cells are positioned around the entire periphery of the chamber in the lower level shown and around most of the higher level in the chamber as shown in FIG. 2; the number of levels is a matter of design choice. Each cell is attached to the main chamber with an individual backing plate 66 in a manner whichpermits the replacement of a cell as a unit during shutdown without disturbance to the rest of the system. Each cell has an individual power supply and control unit 68.

Above the top level of solidification cells and in the region of the pouring port, the main chamber is penetrated by a mold feed chute 70, a casting plate feed chute 72 and a casting discharge chute 74 which terminate inside the chamber on a work shelf 76; the casting plates and the molds are delivered into the main chamber at two different elevations. Each chute includes conveyer means which carry the castings and chill plates into and out of the main chamber. The mold and chill plate feed chutes have entry interlocks 78 through which fresh molds are placed on the conveyer means for entry into the main chamber; similarly, the casting discharge chute has an exit interlock 80 through which the solidified castings from'the main chamber are removed from the furnace system. The interior surfaces of the mold feed chute are lined with suitable heaters and the chill plate feed chute is sometimes fitted with suitable coolers.

A simplified cross-sectional view of a typical solidification cell is shown in FIG. 3. The cell is held by a support member 82which ismade integral with the cover plate 66. The cell structure includes an outer cylinder 84 which surrounds a graphite felt insulator 86 which in turn encloses agraphite susceptor 88; the outer cylinder is capped on the top by an insulator cover 90 and on the bottom by an annular radiation shield 92. A mold 94 and a mold chill plate 96 form a mold assembly 98 which is supported by a solidification cell chill plate 100. The cell chill plate which has coolant passages 102 is movable in a vertical direction as shown.

' An induction coil 104.surrounds the outer cylinder of the cell. Detail on the construction and operation of a typical solidification cellis provided in US. pat. No. 3,714,977. entitled Method and Apparatus for the Production of Direc tionally Solidified Castings".

FIG. 4 is a simplified sketch of the melting and pour.- ing station. The metal ingot 44 is shown positioned over the crucible 58, the latter being mounted on a'rotatable shaft 106 which penetrates the side wallof the melting and pouring chamber 34. This chamber has a floor plate 108 and the pouring port 40 in the floor, the metal ingot, the mold, and the mold chill plate are all positioned along an essentially vertical-axis as shown in FIG. 4, throughout the melting and pouring operations.

FIG. 5 is a sketch of a gripper assembly 110 in the manipulator. The gripper includes a reference plate 112, a gripper drive motor 114 and a pair of adjustable arms 116 which are pivotally attached to the plate. A main actuator rod 118 which is slidably attached to the reference plate has a screw thread 120 at one end rotationally engaged with the motor 114; the other end of the rod'is pivotally attached to the arms by transfer links 122. Fixedly attached to each adjustable arm is a gripper plate 124 which has a series of internal coolant passages 126 as shown in FIG. 6. r

In the operation of the apparatus described above, the umbrella structure in the alloy storage chamber is initially loaded with a full charge of metal-ingots and the pumping system 60 is activated to provide a suitable atmosphere throughout the entire main chamber. and the ingot chamber; depending upon the metal I which is being poured, the controlled atmosphere may.

be a vacuum condition approaching l X lOVa torror a controlled pressure of inert gas such as-argon in the 3 to 6 hundred torr range.

A supply of molds is introduced into the mold'feed chute through the entry interlock and directed toward the work shelf interior of the main chamber'by the conveyer means. The mold feed chute is essentially a tun= nel type device having electrical resistance heaters along the inner surfaces thereof and as the molds progress from the entry interlock to the work shelf they become heated. Presuming, for the purposes of explanation, that the metal ingots consist of an alloy having a nominal melting temperature of 2350F, the molds would be held in the feed chute long enough to achieve a temperature of approximately 2750V. Simultaneous to the activity concerning the molds, the casting plates are admitted into the furnace system through the entry interlock at the end of the casting plate feed chute. Presuming the process to be a directional solidification casting, the casting plates are chill plates which are nominally at room temperature. A typical chill plate is made of copper and has no provision for internal cooling; the chill plate is suitably sized and shaped so that when it is combined with a preheated mold, the plate has enough heat capacity to avoid physical damage due:

to overheating until additional cooling is applied as, for example, by the manipulator or at the solidification cells as will be described further hereinafter.

The manipulatoricombines a heated mold and a. chill plate into the mold assembly and delivers the assembly to a position directly beneath the pouring port in the melting and pouring chamber within a matter of a few seconds. While the mold assembly-is being formed and delivered to the pouring port, a predetermined amount of metal is melted from the metal ingot. The melting is accomplished by the electronbeam gun, the output of which is directed at the tip of the. metal ingot which is simultaneouslyadvanced into the melting and pouring chamber and rotated. As the metal melts and becomes detached from the ingot, the molten droplets fall into the copper crucible. Since the crucible is' water cooled,

its temperature remains substantially below the melting temperature of the metals being contained therein and therefore a skull forms within the crucible. The skull provides'a physical separation between the crucible and the molten metal, and since'the molten metal does not directly contact the crucible the poured metal is maintained contaminationfree.

The beam from the electron gun is swept over a pattern which intercepts both the tip of the metal ingot and the material collecting in the crucible. In this manner, the molten metal is superheated to a temperature in the neightborhood of 2900F. The melting and preheating of a predetermined amount of ingot material in the crucible is timed to be completed when the mold assembly is presented to the pouring port by the manipulator. As these independent activities come together in time and space, the crucible is tipped and the molten metal is poured into the mold. The electron beam is painted across the surface of the molten metal throughout the pouring process.

The filled mold is then quickly relocated away from the pouring port and the mold assembly is mated with a solidification cell chill plate. In the solidification cell shown in the drawing, an induction type electrical heater is used-to produce a temperature of approxi-. mately 2800F in the susceptor of the cell. When the mold assembly is delivered to the solidification cell chill plate, the assembly is engaged by the chill plate and inserted into the cell as is shown in FIG. 3. The mold is allowed to soak within the cell for a period of about minutes to allow the liquid solid interface which begins at the chill plate to grow up the casting to a position corresponding to the radiation shield of the cell. The mold is open on the bottom and the liquid metal is exposed directly to the-mold chill plate which is in intimate contact with the water cooled solidification cell chill plate. As solidification begins, a solid liquid interface is formed in a horizontal plane and movement of the cell chill plate in a downward vertical direction allows the interface to slowly move through the entire casting as the mold is removed from the heat. For the parameters indicated above, a withdrawal rate of about four inches per hour for five minutes has been found satisfactory; the rate is then increased to 8 inches per hour and remains unchanged until the casting is completely removed from the solidification cell. Under these conditions, castings weighing approximately l.-

pound are produced at a rate of one per minute. As the charge weight is increased, the time required for proper melting and superheating of the charge is increased accordingly and the casting output rate .is reduced.

When the alloy is cast solidalthough not completely cooled, the manipulator removes the mold assembly from the solidification cell and delivers it to the casting discharge chute. The complete casting and chill plate are conveyed from the work shelf area out of the main I chamber, and removed from the furnace system by the exit interlock. During the removal process, the casing is further cooled by radiation to the walls of the discharge chute until the temperature is nominally 1000F so that exposure to the natural atmosphere surrounding the furnace causes no oxidation damage to the casting. Also the difference in the thermal conductivity between the mold and the casting materials can lead to stress buildup in the casting if it is exposed to environmental temperatures too quickly. I

I The electron beam gun melting apparatus is an important element of the present invention. The metal ingots which are initially loaded into the alloy storage chamber are advanced into the melting and pouring chamber by the ingot feed shaft. An ingot is presented to the area immediately above the crucible and rotated at a predetermined speed. The electron beam intercepts the tip of the ingot producing a cone shape as the metal is heated to a liquid state and drips from the ingot into the crucible. 'When a measured amount of metal has accumulated in the crucible the electrode is quickly retracted from the electron beam path which is used to further increase the temperature of the metal in the crucible. The quantity of metal melted in each charge is controlled and this is accomplished preferably by mounting a strain gage on the crucible suitably calibrated to indicate the weight of metal added to the crucible. Alternatively, a weighing indicator is attached to the ingot feed shaft and the decrease in ingot weight is recorded as the electron beam melts the tip of the crucible. The latter technique has the disadvantage of being unaccountable for any material whichspatters during melting and not collected in the crucible. The superheated metal is poured into a preheated mold and the ingot is returned to the melting position and a new melting cycle begun.

The main chamber of the furnace system has been described as a generally cylindrical-shell in which the solidification cells are positionedconveniently around the inside of the shell. Alternate furnace geometries include a rectangular configuration having cells which are positioned along the side walls thereof and serviced by a single manipulator which has ready access to all the cells. A further variation is a furnace having a shell of any convenient geometry with the solidification cells attached outside the shell through suitable interlocking mechanisms so that a faulty cell can be isolated from the system proper and repaired or replaced. Similarly, the specific details of the solidification cell can vary without departing from the essence of the invention.

- Although the solidification cell discussed previously is an inductively heated directional solidification device, cells which are heated by electric resistance, cold cathode or electron beam methods are equally applicable. Also, equiaxed solidification techniques are readily substitutable for the DS casting; in the equiaxed case the casting plate is formed of a good thermal insulator material.- v

Another variation to the present invention involves the use of pelletized metal alloy in place of the ingots. In this system a predetermined amount of the bulk alloy is placed in the crucible in a batch process step and the electron beam device is used to melt andsuperheat the metal which is then processes as has been described previously for the ingot feed system.

Various structure .and cooperating processes have been described and a suitable coordinating of the various operations is an essential aspect of the present invention. While it is not essential, a computer control of the overall operation of the integrated furnace is especially advantageous. The computer can simultaneously examine the various functions which are being performed at diverse locations in the furnace system. the rates at which the solidification cells are operating. the forming of mold assemblies, the delivery of the ingot material, the melting, superheating and pouring of the metal, the delivery of the poured castings to the solidification cells, the'solidification operation, the removal of the solidified casting to the discharge chute and other related operations. The integrated furnace is readily programmable so that the continuous production of the same cast product as well as the continuous production of castings having different shapes which require for example variable volumes of molten metal and corresponding solidification. A master computer control can also be programmed to observe malfunctions in such units as solidification cells with 'rapid internal reprogramming so that future castings are not delivered to the area suffering a malfunction.

Another attractive aspect of computer control of the integrated furnace system described herein is the application of a real time control to the liquid solid interface during the solidification process. While most directional solidification withdrawal rates are based on imperical data, it is possible to sense the position of the interface in the solidification cell with infrared sensors and provide a feedback to the computer control which would continuously change the withdrawal rate to maximize the efficiency of the solidification process. This procedure permits adjustment for any change in geometry to the various sections of the casting.

Although this invention has been shown and described with respect to preferred embodiments thereof, it should be understood by those skilled in the art that various other changes and omissions in the form and detail thereof may be made therein without departing from the spirit and scope of the invention.

Having thus described typical embodiments of our invention, that which we claim as new and desire to secure by Letters Patent of the U.S. is:

1. An intergrated furnace system for the continuous production of individual castings comprising:

a main chamber having a controllable internal atmosphere;

means for providing a controlled atmosphere in the main chamber;

a bulk material container adjacent to the main chamber to. provide bulk material for melting, pouring and delivery to the main chamber, and including: a melting and pouring station located at the interface of the main chamber and the bulk container; and means for melting the bulk material; a manipulator positioned internal of the main chamber and capable of rotational and translational motions sufficient to provide access of the manipulator to multiple locations within the main chamber; a fresh mold feeder chute which is joined to, and penetrates the side of, the main chamber and includes: an open end which is fixedly attached to the main chamber to permit the delivery of fresh molds into the main chamber;

an entry interlock to permit fresh molds to be admitted into the mold feeder chute from the surrounding environment without destroying the controlled atmosphere within the main chamber; a conveyer for transporting molds from the interlock to the main chamber; and l heater elements internal of the chute to raise the temperature of the molds prior to entry into the main chamber; a casting discharge chute which is joined to, and penetrates the side of, the main chamber and includes: an open end which is fixedly attached to the main chamber to permit the removal of solidified castings from the main chamber;

an exit interlock to permit solidified castings to be removed from the discharge chute to the surrounding environment without destroying the controlled atmosphere within the main chamber;

a conveyer for transporting the solidified castings from the main chamber to the exit interlock; and

first cooling means internal of the discharge chute to lower the temperature of the castings; a casting plate feed chute which is joined to, and penetrates the side of, the main chamber and includes: an open end which is fixedly attached to the main chamber to permit the delivery of casting plates to the main chamber;

an atmospheric entry interlock to permit fresh plates to be admitted into the casting plate chute from the surrounding environment withoug destroying the controlled atmosphere in the main chamber; and

a conveyer for transporting the plates from the atmospheric interlock to the main chamber; and

solidification cells integral with the main chamber for controlled cooling of the castings.

2. The invention according to claim 1 wherein the solidification cells are internal to the main chamber.

3. The invention according to claim 1 wherein the bulk container includes further means for feeding the bulk material into the melting and pouring station at a controlled rate.

4. The invention according to claim 3 wherein the means for melting the bulk material comprises electron beam means. 1 v

5. The invention according to claim 4 wherein the bulk container includes further a crucible for collecting and containing the bulk material during melting.

6. The invention according to claim 5 wherein the casting plate is a chill plate having a high thermal conductivity.

7. The invention according to claim 5 wherein the casting plate is a material having a low thermal conductivity.

8. The invention according to claim 6 wherein the solidification cell is a directional solidification cell.

9. The method of producing castings continuously in a furnace system having a controllable atmosphere including the steps of:

providing a controlled atmosphere in the furnace;

admitting a supply of casting plates into the furnace through an atmospheric interlock;

admitting a supply of molds into the furnace through an atmospheric interlock;

cooling the casting plates;

preheating the molds;

combining individual preheated molds with individual cooled casting plates to form individual mold assemblies;

admitting a source of metal alloy into a melting and pouring chamber in the furnace;

melting the metal alloy;

collecting the melted alloy in a crucible;

pouring the melted alloy into a mold assembly;

inserting the filled mold assembly into a solidification cell in the furnace;

soaking the filled mold assembly within the solidification cell;

cooling the filled mold assembly until the metal alloy is frozen; and

discharging the solidified casting from the furnace through an atmospheric interlock.

10. The process according to claim 9 further including the step of superheating the metal alloy in the crucible to a pouring temperature which is at least 400F greater than the melting temperature of the alloy.

11. The process according to claim 9 wherein the controlled atmosphere is a vacuum condition with a pressure less than 1 X 10* torr.

12. The process according to claim 9 wherein the molds are preheated to a temperature greater than the melting temperature of the metal alloy.

13. The process according to claim 9 further including the setp of cooling the crucible to a temperature below the melting temperature of the metal so that a skull is formed between the crucible and the molten metal contained therein.

14. The process according to claim 13 wherein the volume of metal which is melted into the crucible is measured.

15. The process according to claim 14 wherein the filled mold assembly is maintained at a temperature greater than the melting temperature of the metal alloy.

16. The process according to claim 15 wherein the filled mold assembly is cooled to a temperature suitable to avoid oxidation and excessive thermal stresses in the casting prior to discharge from the furnace.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION a PATENT NO. 3, 95,672

DATED I July 22, 1975 INVENTOR(S) ROBERT E KING, JR. and BRUCE E. TERKELSEN It is certified that error appears in theabove-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 30, "castin" should read casting Column 3, line 33, "puring" should read pouring Column 6, line 38, "l x l0'/3 should read l X 10' Column 6, line 52, "275ov" should read 2750F Column 8, line 65, "processes" should read processed Signed and Scaled this thirteenth Day of Aprill976 [SEAL] Q Attest.

RUTH c. MASON c. MARSHALL DANN Arresting Ojfr'ze (ummissirmer uj'larw'rrs and Trademarks O

Claims

1. An intergrated furnace system for the continuous production of individual castings comprising: a main chamber having a controllable internal atmosphere; means for providing a controlled atmosphere in the main chamber; a bulk material container adjacent to the main chamber to provide bulk material for melting, pouring and delivery to the main chamber, and including: a melting and pouring station located at the interface of the main chamber and the bulk container; and means for melting the bulk material; a manipulator positioned internal of the main chamber and capable of rotational and translational motions sufficient to provide access of the manipulator to multiple locations within the main chamber; a fresh mold feeder chute which is joined to, and penetrates the side of, the main chamber and includes: an open end which is fixedly attached to the main chamber to permit the delivery of fresh molds into the main chamber; an entry interlock to permit fresh molds to be admitted into the mold feeder chute from the surrounding environment without destroying the controlled atmosphere within the main chamber; a conveyer for transporting molds from the interlock to the main chamber; and heater elements internal of the chute to raise the temperature of the molds prior to entry into the main chamber; a casting discharge chute which is joined to, and penetrates the side of, the main chamber and includes: an open end which is fixedly attached to the main chamber to permit the removal of solidified castings from the main chamber; an exit interlock to permit solidified castings to be removed from the discharge chute to the surrounding environment without destroying the controlled atmosphere within the main chamber; a conveyer for transporting the solidified castings from the main chamber to the exit interlock; and first cooling means internal of the discharge chute to lower the temperature of the castings; a casting plate feed chute which is joined to, and penetrates the side of, the main chamber and includes: an open end which is fixedly attached to the main chamber to permit the delivery of casting plates to the main chamber; an atmospheric entry interlock to permit fresh plates to be admitted into the casting plate chute from the surrounding environment withoug destroying the controlled atmosphere in the main chamber; and a conveyer for transporting the plates from the atmospheric interlock to the main chamber; and solidification cells integral with the main chamber for controlled cooling of the castings.

4. The invention according to claim 3 wherein the means for melting the bulk material comprises electron beam means.

9. The method of producing castings continuously in a furnace system having a conTrollable atmosphere including the steps of: providing a controlled atmosphere in the furnace; admitting a supply of casting plates into the furnace through an atmospheric interlock; admitting a supply of molds into the furnace through an atmospheric interlock; cooling the casting plates; preheating the molds; combining individual preheated molds with individual cooled casting plates to form individual mold assemblies; admitting a source of metal alloy into a melting and pouring chamber in the furnace; melting the metal alloy; collecting the melted alloy in a crucible; pouring the melted alloy into a mold assembly; inserting the filled mold assembly into a solidification cell in the furnace; soaking the filled mold assembly within the solidification cell; cooling the filled mold assembly until the metal alloy is frozen; and discharging the solidified casting from the furnace through an atmospheric interlock.

10. The process according to claim 9 further including the step of superheating the metal alloy in the crucible to a pouring temperature which is at least 400*F greater than the melting temperature of the alloy.

11. The process according to claim 9 wherein the controlled atmosphere is a vacuum condition with a pressure less than 1 X 10 3 torr.