US2135465A - Continuous casting of metal shapes - Google Patents

Description

N 1938. B. E, ELDRED CONTINUOUS CASTING 0F METAL SHAPES Filed Oct 26, 1935 2 Sheets-Sheet l INVENTOR.

ON 5. ELDRED 6 Q W ATTORNEY.

Nov. 1, 1938. B. E. ELDRE iD 2,135,465

CONTINUOUS CASTING OF METAL SHAPES Filed Oct. 26. 1935 2 Sheets-Sheet 2 FIG. 8

Y INVENTOR.

' ATTORNEY.

Patented Nov. 1, 1938 UNITED STATES PATENT OFFICE CONTINUOUS CASTING F METAL snarns Byron a. Eldred, Scarsdale, N. Y.

Application October ,28, 1935, Serial No. 46,884 1 Claims. (01. 22-2001) This invention relates to methods of, and apparatus for, producing continuous cast shapes of iron, nickel, copper, aluminum and other metals, metal alloys and mixtures which I call drawcastings, and is a continuation in part of my viously congealed metal; limiting and controlling 5 copending applications Serial No. 724,227, filed the rate of withdrawal of heat from the mold wall May '7, 1934, Serial No. 661,013, filed March 16, in advance of the congealing zone, as by laterally 1933, and Serial No. 589,548, filed January 28, insulating said walls and variably cooling the 1932, now Patent No. 2,048,733, and which is a same; and varying the heat withdrawal from the division of my copending application Serial No. freezing end of the casting, by adjustable means 459,040, filed June 3, 1930, issued as Patent No. for cooling the casting issuing from the mold; 1,868,099, July 19, 1932. each of which is important in combination with In the past efforts have been made to form a third variable, which is controlling rate of continuous castings by supplying molten metal withdrawal of the rod, and a fourth variable, to a chilled metal mold, wherein the mold wall which is controlling temperature of the metal contacting with the molten metal was maintained supplied to mold. at a temperature closely approximating that of In actual practice, it was found that when the chilling medium, molten metal being introthese-variables were adjusted and maintained in duced to the mold at one end thereof and conaccordance with the patent, the process opergealed metal being withdrawn at the other end, ated satisfactorily and continuously producing but as far as I am aware such processes have the above described novel castings. It was found, never proven commercially practical, and are unhowever, that the adjustments had to be mainsuited to the casting of intermediate metal shapes tained; also the possible rate of casting was which present a large surface to volume relalimited; and sometimes after running satisfactionship, such for example as cast rods suitable torily for many hours, there might be a parting for directly drawing into wire. of the casting, leaving a troublesome plug of Prior to making the present invention, I prosolid metal in the mold. posed to substitute for such chilled mold methods, In searching for a physical explanation of the some modifications of the general principle of a above limitations, it was discovered and proved hot mold method which had been previously that in actual practice, the freezing becomes used by me for casting a copper ingot in an artiintermittent; and that in such case, both the ficial graphite mold as described in my very early freezing and the intermissions were interdepend-. Patent 1,217,581. Said patent prescribes top ent phases of automatically set up cycles of heat heating of the mold and molten metal therein, removal; in each cycle the intermission was due while withdrawing heat by progressively chillto the fact that the outward heat flow through ing the mold and metal from the bottom upward. the last fro e met of the cast ng must first As there pointed out, the copper is a better conoperate to remove residual superheat from adjaductor than the graphite, and it follows that the cent molten metal; and thereafter operates to cooling to below freezing will progress upwardly freeze said metal, by developing its latent heat in the copper ingot in advance of such cooling as sensible heat and conducting it away. 4 in the surrounding mold wall. It was also discovered in certain cases, that My above specified draw casting patent, No. there was likely to be an inertia-like tendency; 1,868,099, refers to this prior method of casting; that after removing the sensible superheat, the contrasts its requirements with those involved in cooling would tend to persist, and the adjacent continuous casting While the molten and solid molten metal would be superchilled, that is, metal are passing through the mold; and disv liquid would be cooled below its freezing point closes various generic essentials of new methods before the freezing part of the cycle was rewhereby freezing from the side walls and sticksumed. During this time of prolonged sensible ing of metal thereon, were substantially elimiheat removal, the casting is being withdrawn at nated, so that sound castings were continuously a, fixed rate, and the freezing surface shifts produced, which were free from oxides, were of toward the exit end of the mold. When the theretofore unattainable high density, and which freezing is resumed, the superchilled liquid is exhibited the unique crystalline characteristics 'self freezing to an extent depending on its described in said method patent, and claimed in amount of superchill, the freezing being accomsaid Patent No. 2,048,733. panied by a rise in its own temperature'to its Some of the improvements that made such results possible are set forth in said method patent, as including withdrawing the heat of congelation substantially solely through the prefreezing point; and the sensible heat which is absorbed in raising temperature, operates to remove latent heat from said liquid, while the inner end of the casting is also removing latent heat. This ordinarily results in rapid freezing of a considerable length of metal on the end of the casting, thereby shifting the freezing surface away from the exit end of the mold. But

if the superchilling is excessive the inner end of the casting may become too cool to fuse with the subsequently freezing metal; thus interrupting the casting operation.

It was also discovered that the range of frequencies permissible for cyclic freezing was rather limited that keeping within said range depended on the maintenance of thermal balance between speed of withdrawal of the casting and rate of heat withdrawal; and that this limited the possible speed of casting.

So according to my present invention, increase in casting rate requires maintaining the metal supply at reasonably constant temperature; withdrawing the casting at the desired higher rate while withdrawing substantially all superheat through the wallsof the mold; and adjusting the heat removal from the previously frozen metal so that the heat withdrawn through its frozen end is approximately the same as that supplied by the developed latent heat from the metal freezing at the predetermined speed.

From the above, it will be seen that operating in accordance with the methods described in said draw casting patent does produce the new and useful castings having the unique characteristics described therein, but the specific details and possibilities of functionings of said methods were not known at the time, so the patent did not specifically disclose them and the method claims thereof were made generic to the basic features of procedure which it was known would produce such castings. It will also be seen that my later discoveries about the intermittent freezing cycles and their functionings, are the basis of my pres= ent inventions for obviating the practical limitations that may attend successful operations according to the basic essentials of the method disclosed in said draw casting patent. I also discovered that the law of heat flow a steady state applicable to ordinary stable conductors must be amplified for present conditions, where the temperatures are sufliciently high, and where all the metal, molten, freezing and solid, is moving through the mold. Under such conditions, wherein the heat'supplied to a unit area of mold wall heat dissipating surface, is constant and varies in accordance with the speed of casting, the thermal conductivities of the materials comprising the mold and its surroundings in thermal relationship therewith, limit therate at which heat may be removed from the metal; and this limits the temperature gradients that are possible in any given design. Consequently, when the dimensions of the parts are fixed .and temperatures are sufliciently high, a condition may be established that may be likened to that of an over-charged conductor. That is to say, by proper design and operation, the mold walls at and extending outwardly from the inner surface, may be maintained at temperatures closely approximating that of the metal adjacent thereto, while most of the temperature drop is transferred to a more remote region of the external layer of the mold wall, as hereinafter described.

My present invention is a result of my above discoveries, particularly as concerns the interfor mittent freezing cycle; and its primary objects include controlling the rate of removal of heat from the casting with a view to maintaining proper heat removal conditions at the freezing end thereof, with little or no attention to having the heat gradient in the mold wall the same as in the casting; also, corelatively, increasing the physical length of the critical part of the cooling zone of superheat removal so that changes of temperature of the molten metal flowing to the freezing surface, will be correspondingly gradual for any given rate of withdrawal of the casting; all for the purpose and with the result of locating the freezing surfacenear enough to where the molten metal is ready to freeze, to avoid setting up the intermittent freezing cycle, or at the worst having the sensible superheat at the freezing surface so slight and over such small areas thereof, that any effects of removing it either through the previously formed casting or through the mold wall, will be of negligible importance. When casting metal mixtures, more or less wide freezing ranges are provided by successive freezing of the various constituents; and in such cases it might be argued that after incipient freezing of the high melting point constituent, other lower melting constituents would still be present as liquids containing sensible heat above their respective freezing temperatures. So the term superheat is herein used in its broad sense, as meaning that sensible heat which was added to the metal or metal mixture to raise its temperature after it was completely molten. Conlast frozen surface. Limiting .heat removal through the preformed casting to this one purpose, prevents superchilling before freezing;

greatly increases the permissible speed of casting; and makes possible the growing crystals of very great length; and in special cases making a long length of rod comprising a single full diameter crystal. v

The ultimate objectives of my invention also include the following:

One object is to product cast metal shapes directly from molten metal, which shapes shall possess superior physical qualities for subsequent deformation by rolling, drawing and/or other working.

Another object is to cast metal in a mold wherein the removal of superheat and latent heat from the metal is primarily affected in separate paths.

Another object is to cast metal shapes and substantially control the size and axial trend of crystal growth therein by maintained latent heat removal from the zone of crystallization in the mold at a substantially continuous uniform controlled rate.

Another object is to cause metal to freeze continuously instead of intermittently in producing castings.

Another object is to produce a metal shape for subsequent deformation which shall be of such uniform density, like crystalline structure, and so free from nonmetallic inclusions, and interand intra-crystalline stress that the metal on subsequent deformations in working, will flow substantially evenly throughout.

Another object is to cause freezing metal to contract quickly away from the mold wall to insure good surface on the casting with consequent reduction of friction between the casting and the mold wall. a

Another object is to so regulate the speed 0 solidification of a metal mixture that the crystals formed shall be substantially'of the same order of magnitude throughout the casting.

Another object is to cast solid solution alloys by such orderly, controlled removal of heat that coring of the casting and grading of the crystals is prevented or minimized.

Other objects will appear in the following description.

According to-the present process I remove the superheat and the latent heat from the molten metal maintained in thermal relationship with suitable heat dissipating means, supplied to an open ended forming chamber, through separate paths, the superheat being substantially dissipated before the metal reaches the freezing zone, and the latent heat being withdrawn at the freezing zone through the contacting last frozen metal by a suitably established maintained outward heat flow from the preformed casting. It is desirable for the most successful practice of the process that this division of heat removalbe maintained as perfectly as possible, for it is undesirable, on the one hand, that latent heat as liberated be directly withdrawn through the mold wall, and it is also undesirable, on the other hand, that superheat be withdrawn through the congealed metal. It will be understood, however, that, some tolerance is permissible, particularly when other conditions, hereinafter referred to, are maintained which tend to minimize the undesirable effects of deviation from the ideal condition of a perfect division of heat flow in the separate paths referred to.

Separate paths of heat removal need only be maintained in the critical zones of direct heat removal, as such paths may subsequently converge and be conveniently served by a single chilling medium. It will be understood that any suitable means' for establishing the desired heat flow in the formed casting to cause metal to freeze thereto may be employed. Likewise any suitable means of dissipating superheat from the metal to prepare it to freeze may be used without departing from the spirit and intent of the invention. The means hereinafter illustrated and described is only one of several variations in design of apparatus and-processing which I have employed successfully.

It will be understood that for any given metal cast at any given speed from superheated molten metal of known temperature, an exact quantity of superheat and latent heat must be dissipated from the metal to cause it to freeze. In the present invention, heat is removed progressively to first dissipate substantially all of the superheat from the mass of metal moving through the mold in advance of an established freezing zone, and this separate and distinct operation is followed by the removal of latent heat through the last frozen metal, likewise in a separate and distinct path of heat flow. I These paths of heat flow are provided by any suitable chilling means to maintain outward heat flow from the metal, and the rate of cooling depends upon the quantity of heat removed from the metal in a given time.

In draw-casting, the speed of withdrawal of the casting establishes the quantity of metal supplied to the mold in a unit of time, likewise the quantity of superheat to be dissipated therefrom. Such heat dissipation is provided for in the design. The superheat may be dissipated in a shorter or longer distance of travel of the metal through the mold, at the established rate, by providing more or less effective heat dissipating means in thermal relation to the moldwall. I prefer the slower removal of superheat over a comparatively long distance of the mold wall. In this way, a proportionally larger volume of metal containing less superheat, is presented in advance of the freezing zone, thus insuring the desired condition of uninterrupted freezing and an equalization in metal temperature throughout its cross section. This condition is especially desirable in the metal contacting the freezing metal when axial orientation in crystal growth is desired. For any established fixed temperature outer terminal, for maintaining theheat flow from the metal in the mold, it will be apparent that the rate of heat removal will be progressively slower as the advancing metal in the mold, serving as a high temperature terminal, loses its superheat.

For convenience in description herein, the entire structure which provides a passageway for the metal from the furnace to the point where congealed metal is withdrawn will be considered as a mold, although it will be understood that in practice the said mold may consist of more than one structural element. Between its inlet and outlet ends the mold may be considered to be divided into the zones hereinbefore referred to, namely, a zone for the removal of superheat, a freezing or casting zone, and finally a zone for cooling the casting. It will be understood that these zones are not fixed either in position or extent, but the mold is preferably so constructed that when any assumed set of conditions as to temperature of metal supply and rate of travel are maintained in operation within reasonable limits of variation, the above-described conditions of heat flow will be maintained within the said zones.

The complete and separate paths for the removal of superheat andlatent heat in timed relationship may be established in apparatus embodying widely different means for controlling such heat withdrawal. In the present apparatus it is made posible to a large extent by the use of thin walled mold surrounded by an interposed conducting medium, preferably of lower thermal conductivity than the mold, providing a condition of heat flow through the mold wall which insures that its inner surface shall be maintained substantially at the temperature of the contacting metal within, thus insuring against the development and removal of latent heat by local chilling of the mold wall. This thin mold wall I have found to be most desirable and it has allowed of various designs of molds and the use of fixed chilling means not practical with thick walled molds. For example, such thin walled molds of graphite, protected against oxidation, have been successfully employed when cooled directly with air, or a surrounding water cooled jacket. Such an arrangement I found suitable for casting metal mixtures freezing over a more or less wide temperature range. The removal of heat if too rapid may be overcome by increased superheat in the metal supply. I prefer, however, to chill the metal slowly in a longer molten metal zone, especially when casting single metals, for example, copper.

The thin walled mold has the addedadvantage of presenting the minimum of radiating surface as compared with its heat accumulating surface and low thermal capacity which insures speedy adjustment to temperature variations.

The heat removal from the outer surface of the thin walled mold will depend upon the interposed resistance to heat flow established between the mold and the heat dissipating means withwhich it is in thermal relationship, and the inner surface of the mold wall will be substantially at the temperature of the contacting molten metal within it as long as the resistance to heat removal from its outer surface is sufficient, on the principle which I have discovered that when heat is received by one surface of a body and dissipated by another at a slower rate, a region of substantially uniform temperature, with maximum value equal to that of the source,

will be progressively built up on the receiving side, through which heat is transmitted .to a,

gradient conducting portion of the body which will decrease in length and increase in capacity until an equilibrium of reception and dissipation is established. v

I have used various means to restrict and con- 1 trol the cooling of metal in the mold, such for example as partial heat insulation between the mold and the surrounding furnace lining which ultimately dissipated theremoved heat to the If the mold wall is thin, the outer surface which radiates heat is relatively small, and its capacity to dissipate heat is low even if not insulated. If properly insulated or otherwise treated, the capacity of the outer surface to dissipate heat may be still further reduced. Furthermore, the rate of heat removal may be controlled by any known or desired means, and such means may include heat supplying means, as for instance surrounding the mold with molten metal.v maintained at suitable temperature; or I may use various combinations of the insulating, chilling, or heating means; but such uses of heating means are claimed in my copending application Ser. No. 233,655 filed October 6, 1938, which is a continuation-in-part of this aplication.

In the foregoing descriptions, I have referred to the desirability of maintaining a substantially constant rate of travel of the metal through the mold. While this is desirable for the production of a product having a superlatively uniform crystal structure, it will be understood that in, the case of some metals I have found that the congealed metal may be advantageously withdrawn intermittently or incrementally, provided the increments withdrawn are reasonably short, having regard to the length of the mold, and provided the average rate of travel remains sub stantially constant. When this is done, the freezing zone or line shifts forward and backward within the zone of restricted lateral heat how, and it will be understood from the foregoing description that the provision of such a zone contributes to the possibility of such intermittent withdrawal of metal. It will be understood, therefore, that the phrase constant rate of travel as used herein includes the possibility of suchintermittent or incremental withdrawal of the metal where the average rate of travel is suitably constant.

When the process, is practised in accordance with the foregoing description, and when all of the conditions are properly adjusted, the castings masses It may be stated in general that castings produced by this method are superior to similar shapes produced by deformation and annealing castings of the prior art. The orderly removal of heat from all portions of the casting at the same rate has aiforded excellent castings from metal mixtures exceedingly difficult, or even thought to be impossible, to cast by methods prior to the development of my methods.

The even removal oi. latent heat from metal prepared to freeze by the separate removal of its superheat also ofiers not only a remarkably uniform casting structure, but there is likewise evi:

deuce, to a degree not heretofore realized in commercial casting of metal mixtur, of an absence of the usual coring of the casting and grading of its crystals, also an absence of interand intracrystalline stress. 7

The excellent surface of the castings produced freezing of the metal, because of the complete pre-removal of the super-heat, thus allowing for the speedy contraction with the change of state from liquidus to soliduswith the prompt removal ofthemetali'romthemoldwall andthesubstantlal elimination of friction therewith as the casting is withdrawn. A slight tapering oi the mold-wall outwardly may be provided to eliminate friction in the withdrawing of the casting, but with the pruent method I find this no longer necessary in the casting of most metals.

Theprooess ofmakingthecastings may be carried out by varioustorms of apparatus but I have illustrated incertain figures of the drawings apparatus that I have used successfully for carrying out my method.

In these drawings:

Fig. 1 is an elevation of the casting apparatus.

Fig. 2 is a plan view of the apparatus shown in ms. 1.

Fig.3 is a front elevation of the mold or die blockused in Figures 1 and 2.

Fig. {is a plan view of the die block of Fig. 3.

Fig. 5 is a sectional elevation through a porbymymethodmaybeascribedtothecontinuous tion of the molten metal container or furnace I chamber, the section being taken through the die block of Figure 3.

Fig. 6 is a view oi. the die or mold chamber shown in section in Fig. 5. r

Fig. 'l is a section of a die block and mol chamber for casting hollow shapes. Y

8 is an end elevation of the die and mandrel ofl 'lg.7asviewedfromtheleftofthat figu e.

ReferringtoFigs. 1 and2,thefurnace chamher is shown at I. It may be constructed of refractory brick orother suitable heat resisting material. The furnace is shown as of the inductiontype andatthebaseistheusualtransformer indicated at I to keep the molten metal at proper temperature in a well known way; the details of this induction apparatus and the way in which it induces current in the molten metal need not be further explained as it is old and well known intheartandtormsnopartofthisinvention. iisuitablepipelmayadmitooolingfluidtothis transformer in a well known way.

The furnace may have any cover arrangement but I have shown a lid 5 closing the chamber 8 containing the molten metal. This lid is supported by a bar 1 attached to a forked bracket 8 secured to the lid. On this bar I is slidably arranged an arm 9 to which is pivoted the link ID. This link in turn is pivoted to the short end ll of an L-shaped lever, the longer end of which is designated by reference character l2. This L- shaped lever is rotatably fastened to a support l3 secured to standard l4 which has a pivot l5 seated in a pivot bearing in the top of the furnace wall.

On swinging the handle or lever l2 to the left in Figure 1 the link raises the arm 9 until it engages the flange IS on the bar 1. Further movewise in Figure 2, and the furnace lid, together with the lid supporting structure may be rotated to the right in that figure, thus exposing the supply chamber for replenishing the metal from time to time. Reverse movement will place the-lid back in position.

The furnace wall may have as many mold chambers as desired but in the drawings I have shown it equipped with three molds. Details of the mold header and mold are shown in Figures 3, 4 and 5. Each mold I1 may be made of any appropriate material but I have found Acheson graphite to be suitable for non-ferrous metals. The wall of this mold chamber is made quite thin, as previously described, and for the purposes given. By way of example, I would say that in this particular design the thickness of the wall of the mold is about one-quarter of an inch, but the permissible thickness of this wall will depend upon the heat conducting properties of the material from which the mold is made and upon various other factors.

The die or mold as shown is secured in the die header l8 by a forced fit of well dimensioned machined surfaces, and this is made to taper outwardly of the furnace so as to provide increasing area of the path for heat flow to overcome the thermal resistance of the block l8 and thus allow of the removal of the major portion of the superheat in the metal entering the openings in the die header. The final removal of residual superheat is effected by the slow heat leak from the thin walled molds l'l, Figure 5.

This header [8 may be made of any suitable refractory material, preferably of the same material. as the molds I! so that there shall be no difference in the expansion of these members. The mold I1 is surrounded at the outer portions by an insulating material [9 which may be of any suitable refractory material such as Sil-o-Cel or kieselguhr brick. The purpose of this insulating material is to so balance the heat removal through the mold walls as to just remove the super-heat by the time the metal reaches the congealing zone, as previously described, though a slight amount may be left in the metal without materially detracting from the properties of the casting. This mold chamber should be properly luted to keep out the air and I have also found it desirable to let a small amount of illuminating gas issue from a pipe 20' (Figures 1 and 5) so as to burn and surround the issuing casting with a neutral or non-oxidizing atmosphere and prevent air from entering and oxidizing the wall of the graphite mold surrounding the issuing casting, though of course this is a detail that may be omitted, or the condition otherwise provided for. The cast shapes illustrated in Figs.' 1 and 2 are rods 20" taking the shape of the molds shown in Figs. 3, 4 and 5. Each rod may pass through supporting rollers 20, 2|, 22 and 23 journalled respectively in levers 24, 25, 28 and 21. These levers are pivoted on rods 28, 29, 30 and 3| extending across between supporting walls 32, 33.

The supporting walls are fastened to the bottom member 34 which is secured by bolts 35 to the supporting I-beam 38. Springs 3'! resiliently move the pulleys 20 and 22 into'engagement with the rod and parallelism of movement is insured by a. tooth 38 in arms 25 and 2! meshing in a corresponding socket of arms 24 and 26. This mechanism Just described is the centering oraligning mechanism and of course may be omitted when desired, particularly when the pulling mechanism about to be described is placed closer to the mold chambers.

The pulling mechanism is generally indicated at 29 and consists of any suitable electric motor 40, belted or. otherwise connected to a speed reducing mechanism 4| so as to obtain the proper slow rotation of the shaft 42, on which is keyed the gripping pulleys 43. These gripping pulleys are arranged in Figures 1 and 2 beneath each of the rods and they may have any suitable gripping surface. Preferably they are knurled slightly for this purpose. The rods are resiliently pressed against the gripping pulleys 43 by pulleys 44 journalled in an arm 45 pivoted at 46 to the frame of the pull-out mechanism and a spring 41 of adjustable tension presses the pulleys resiliently against the rods. This pull-out mechanism is properly secured to the supporting I- beam 38.

When suitable lengths of the rods 20" have issued from the molds they are cut oil by mechanism'not shown, or these rods or other shapes suitable for coiling, may be wound into coils by any desired means.

The cooling of the rods is readily produced by flowing water as at 48, from a nozzle 49 controlled by valves 50. The water is supplied to the nozzles through a pipe or hose 5| connected to the water supply pipe 52. The main valve 53 may also be arranged to shut oft the entire water supply or adjust the flow of water simultaneously for all three of the nozzles, individual adjustments being made by the valves 50. The water from each of the nozzles flows around the issuing rods or castings and passes into a water trough 56. The water trough may deliver the water through pipe 54 to the drain connection 55.

As has been previously pointed out, it is desirable to chill the casting to maintain heat removal on a substantial planar cross-section to provide an equal heat flow from a like planar cross-section in the chilling zone, as described in my issued Patent 1,868,099. The simple expedient shown in Figures 1 and 2 of a stream of water applied to the upper surface of the issuing casting serves admirably because water flowing from this stream not only surrounds the casting, when properly regulated, but flows toward the outlet end of the mold where it is definitely or sharply arrested in its flow by the heat in the issuing casting which causes the water to boil.

By shaping the mold member to provide greater or less resistance to longitudinal heat flow therein localized accumulation of heat or ready dissipation of heat may be produced as desired.

Figure 6 illustrates a straight walled mold which provides such a minimum of mass that its heat accumulating surface is readily maintained and rammed into the furnace lining and held in use place by a metal face plate and channel iron, as,

shown in Figure 5.

Figure 7 shows a mold for casting tubular shapes. This differs from the mold shown in Figure 5 in that the mold contains a central outwardly tapered mandrel it supported in the die header against the head 59. This head has a plurality of openings I (three wing shown) so that the molten metal can flow readily into the mold chamber. By proper withdrawal of the heat, as previously described, the inner surface ofthe cast tube, like the outer surface, is quite smooth and the crystalline structure is the same as that of solid rods previously described.

I have shown molds for casting rods and circu-' lar tubes but it "will be apparent that various shapes, such as squares, flats or ovals may be by properly shaping the molds and mandrels.

The header it is designed as shown in the drawings with a taper to provide heat dissipating surface in excess of heat accumulating surface. By proper proportioning the header the quantity of heat dissipated thereby may be regulated within close limits, and I prefer to so design the assemblage that it willsufi'ice for. a constant predetermined speed of casting, thereafter performing the operation at a stated speed, so that control becomes a matter of the maintenance of 'metal supply within readily maintained temperature limits.

With the continuous uninterrupted removal of latent heat provided by the present invention not only is the permissible speed of casting increased several fold, but the chilling of the casting'may advantageously be by radiation to a suitably chilled heat dissipating means surrounding the casting after it issues from the freezing zone. As is well known, heat transfer by radiation is at the speed of light, whereas heat transfer'by conduction is a slow process.

Having described my invention. what I claim is:

1. A method of casting metal to form continuous castings from superheated molten metal, which includes progressively removing'the superheat and the latent heat from the molten metal successively and independently in separate paths of heat flow.

2. A' method of casting metal to formcontinuous castings from superheated molten metal supplied to one end of an open ended mold, which method includes providing the'mold with chilling means capable of removing superheat and latent heat progressively in quantitative timed relation- 7 ship-sothat metal entering the mold shall, as it predetermined'zone at temperatures sufficient to substantially prevent abstraction of latent heat therethrough; removing substantially latent heat only, through the surface of contact of the congealed metal with the liquid metal by progressiv'ely chilling the congealed metal while withdrawing it from the mold and supplying additional molten metal thereto at the same rate as the withdrawal rate.

4. A method of continuous casting metal in a mold from a supply of superheated m olten metal maintained therein, which method includes progressively cooling the superheated molten metal by causing the superheat to flow continuously out of said molten metal. substantially solely and directly through the mold wall, until substantially all its superheat has been removed, while progressively forming a casting by causing substantially all the latent heat to flow substantially continuously out of the thus 'cooled metal, through the inner end surface of the preformed casting.

- 5. A method of continuous casting metal in an open-ended mold, maintained in thermal relation with chilling means, which method includes supplying superheated molten metal to one end of the mold at a predetermined temperature and at such rates that the metal as it progresses through the mold, shall have substantially all its superheat progressively removed therefrom by the time it reaches a predetermined freezing zone; and, in said none, freezing the thus-cooled metal by removing substantially all of the latent heat from said metal through the last frozen metal, and withdrawing the thus-formed casting from the other end of the mold.

6. A'method of producing continuous castings in an open-ended mold in thermal relation with heat accumulating and dissipating means capable of withdrawing heat from said mold at maintained rates, which method includes supplying the mold with superheated molten metal at one of its ends, withdrawing the casting from its other end, and regulating the length of travel, per unit of time, of the superheated molten metal in the mold, by and in accordance with any established rate of withdrawal of the casting, for thepurpose and with the result of removing substantially all of the, superheat through the walls of the mold and substantially all of the latent heat through the inner end surface of the last formed casting.

7. A method of producing continuous castings in an open-ended mold formed or provided with heat accumulating and dissipating means capable of removing heat from said mold at maintained rates, which method includes supplying superheated molten metal to one end of the mold; and withdrawing the casting at the other end of the mold to advance the metal through the mold at rates predetermined with respect to the quantity of such superheat to be dissipated therefrom, so that the speed and distance of said advance of the molten metal will be sufllcient to effect removal of substantially all its superheat progressively, as the metal approaches an established freezing zone at the inner surface of the last preceding frozen metal; and there freezing the thus cooled molten metal tosaid surface by withdrawing substantlally all of the latent heat through said surface.

BYRON E. ELDRED.

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