US2225373A

US2225373A - Method and apparatus for casting metal

Info

Publication number: US2225373A
Application number: US156327A
Authority: US
Inventors: Norman P Goss
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-07-29
Filing date: 1937-07-29
Publication date: 1940-12-17
Anticipated expiration: 1957-12-17

Description

Dec. 17, 194i). N. P. Goss METHOD AND APPARATUS FOR CASTING METAL Original Filed July 29, 193'! 3 Sheets-Sheet l FI Grl uw /Vcu RO oG n m. m EP /o v NN Mdm m) Dec. 17, 1940. N, P, Goss uETHon Arm APPARATUS FOR cAs'rIuc `MFTAL.

`3 SheetS-Sheet 2 original Filed July 29, 1937 INVENTOR NORMAN P. Goss nga 17, 1940.

N. P. Goss 2,225,373

METHOD AND APARATUS FOR CASTING METAL Urignal Filed July 29, 19257 3 Sheets-Sheet 3 Fla-4 INVENTOR VNORMAN P. GOSS Patented Dec. i7,

PATENT oFF-TCE METHOD AND APPARATUS FOR CASTIN l METAL Norman P. Goss, Youngstown, Ohio Application July 29, 1937, Serial No. 156,327

` Renewed May '1, 1940 Claims.

This invention relates toca method and apparatus for continuously casting metals.

My invention provides a method and apparatus' for passing astream of molten metal into a die and extruding or extracting a continuous member of solid or seuil-solid metal from the other end of the die. I am aware that methods and apparatus for a similar purpose have been heretofore proposed but. where they purported to deal 0 with metals of high melting temperature, such as steel and the like, they were of no practical or commercial value because, if successful at all,

after a brief operation the apparatus broke down.'

due to the freezing of thegmetal at such points as 5 to stop the process, or because of the disintegrato provide a novel die in which the molten metal ,is cooled and a skin cast upon it, and wherein a substance is provided between the walls of the die and the cast metal which performs a number of functions, among them being the lubrication of the passage of the metal through the die, the filling of the spaces where the solidifying metal draws away from the die bya self-accommodating material which maintains efcient heat conductivity between the metal and the die, the protection of the walls of the die from direct contact with and heat radiation from the metal, and the maintaining of a suitable surface on the cast metal. One preferred form of such a lubricant or self-accommodating die lining material is graphite, which is a good black body and performs the function of absorbing and conducting heat from the solldifying metal to the walls of the die while reecting back to the metal little of the heat received, this in addition to performing all of the functions outlined just above.

Another feature of the present invention is the provision of apparatus for very carefully controlling the temperature of the metal during all stages of the casting process.` This temperature control extends to the metal in the reservoir from which molten metal is fed to the casting or chilling apparatus and to the various parts of the apparatus as the metal passes through it. By

such close control the metal may be cast from a point just slightly above the solidus, giving certain preferred characteristics to the solidified metal where desired. Also the rate of contraction and the correspondence of the sectional area of the cast metal to the die is assured at all points during the passage of the metal through the die. This assures a predetermined space for accommodating the die lining material such as graphite mentioned above.

Another feature of my process and apparatus is the special arrangement at the molten metal receiving end of the die where special means is provided for confining the molten metal while the rst skin is being formed thereon. This feature involves the use of a member or means which is hereinafter termed a liner, the use of which is very important in controlling the formation of the first skin on the solidifying'metal. By the use of varying types of liners the texture of this skin may be vvaried as will hereinafter appear. The use of such a liner contributes to the long life and commercial practiability of* iny die casting process.

Another object of the Ypresent invention is to provide novel means for insuring the steady and continuous passage of the metal through the idle,

both by means of the hydrostatic pressure of molten metal is held preferably in a reservoir of sufficient capacity to provide a steady stream of molten metal to the die apparatus at a substantially constant temperature. Such a reservoir is also of. sumcient capacity to permit the molten metal to lie quietly so that slag and other occluded foreign material may have time and opportunity to rise to the surface where it may be disposed of. Another novel feature which protects the quality of the metal is the provision of nonoxidizing and, where desired, a reducing atmosphere about the metal as it passes into the die and as it passes through the die. This prevents the formation of oxides during the course of the casting process which oxides might be occluded vin the solidified metal or might appear upon the surface thereof with not only bad effects upon the metal quality but deleterious eifects upon the walls of the die. Y

Another function of the'application of nonoxidizing or reducing gases about the solidifying metal as it passes through the die is the protection which certain of such gases may provide for the walls of the die and the aid of such gases as for instance hydrogen, in maintaining heatconductivity between the solidifying metal and the walls of the die. l

Another novel feature of my apparatus is the provision of nonoxidizing or reducing gases in such a way in the apparatus that they not only provide the advantageous features pointed out above but in addition may be arranged to bubble through the molten metal in the feeding reservoir thereby producing a metal agitating or cleanmetal and the walls of the die without distorting or damaging the `solidifying skin on themetal through the die. l

Another novel feature of the present invention is the careful construction of the walls of the die to conform to the cross section of the solidifying `and contracting metal passing therethrough.

Among the novel features of my invention is the provision of a metal constricting portion at the exit end of the die whereby to reiine the crystalline structure of the metal at that point and to protect the semi-solid metal in the die from the pulling effect of the pinch rolls or other pulling apparatus which may be used to aid in the passage of the metal out of the die.

Other advantages and novel features of my method and apparatus will appear hereinafter from the speciilcation and the drawings and the essential features thereof will be summarized in the claims.

In the drawings:

Fig. 1 is a central section showing typical apparatus for carrying out my novel casting process with certain portions thereof relative to temperature control being shown somewhat diagrammatically;

Fig. 2 is an enlarged central section through the die portion of Fig. 1 and along the line 2-2 of Fig. 3, with lubricant supply and die temperature control shown diagrammatically;

Fig. 3 is a sectional view along the lines 3-3 ofFigs.2and4;

Pig. 4 is a sectional view along the line 4-4 of .Fis-3:

ly controlling the temperature of the molten metal'in thereservoir in accordance with a predetermined temperature of metal passing to the' die;

Fig. 7 is a section similar to Fig. 3 showing a modified form of die for forming shapes directly from molten metal.

In the apparatus illustrated in Figs. 1 to 6, a reservoir I0 is provided for receiving and holding molten metal before it is fed to the casting apparatus. Such. a reservoir will be supported upon suitable building structure (not shown) and supplied with molten metal from a ladle handled by an overhead crane, or by any other suitable apparatus. The. reservoir i0 is o! such capacity that a body of metal is held ina substantially quiet state and at a substantially constunt temperature for feeding to the 'casting apparatus. The device of Figs. i to 6 illustrates apparatus for casting slabs and where such slabs are of normal heavy section, such as 2 to 6 inches thick and 12 to 36 inches wide or wider, the reservoir In would hold to `80 tons or more of metal to provide the. highest quality of cast metal. l y

The reservoir illustrated comprises a steel or cast iron shell provided with an inner refractory lining Il adapted to stand the heat of the metal in the reservoir for long periods of time without substantial deterioration, or objectionable effect upon the metal in the reservoir. For instance, if molten steel is to be handled, `the lining might be of chrome brick. If the metal in the reservoir` is to `be held at a carefully determined temperature and if skulls in the reservoir are to be avoided, sorneheating means should be provided therefor. In the form shown an induction coil I2 is built into the reservoir protected by a heat protecting refractory layer I3 between the coil and the inner lining and preferably having also outside of the coil a heat insulating layer Il next to the shell. The reservoir may also be provided with an overflow spout (not shown) 'near the top so that upon an accumulation of slag in the reservoirthe level of the metal therein may beraised and the slag run off through the spout.

Suitable openings are provided for removing metal from the bottom of the reservoir lil. A mainopening lileading to the casting apparatus is closed by the usual stopper I6 which is manipulated by `the stopper handle I1. Also preferably an auxiliary or emergency outlet I8 is provided in the bottom of the reservoir closed by the stopper Il which may be manipulated by the handle 2li. If for any reason the reservoir must be emptied other than through the opening l5, the outlet Il is available through which the metal in the reservoir might be passed to another ladle or toa series of molds if necessary to discontinue the operations through the continuous casting apparatus.

The metal passes from the feed reservoir I0 through a passage 2| to the casting apparatus. This e is preferably lined also with a refractory lining and preferably also supplied with a separate electric induction heating coil 22 supplied from a suitable source of current. This will insure that the passage 2i remains open at all times.

The diecasting apparatus is indicated generally at 23 and comprises an upper chamber portion '2l adapted to be connected to the passagerway 2i to receive metal from the reservoir l0.

Below this is the die portion 25 where the initial solid skin is formed on the metal. Again below this is the die portion 26 for the further solidiflcation of the metal on its passage therethrough. At the mouth of the die is theporticn 21 whichis somewhat restricted so as to provide ametal working eect and `to protect the metal farther back in the die from any` pull exerted by the extracting apparatus. This pcrtlonalso helps to keep the shape centered in the die. A pair of pinch rolls for extracting is indicated somewhat diagrammatically at 2l, it being understood that. these will be provided with a suitable drive and with means for varying the position of therolls on opposite sides of the slab of metal passing. between them. Suitable structural framework (not shown) will be provided for supporting the die casting apparatus.

Where the passageway 2l leads to the upper chamber oi' the die casting apparatus, a structure is preferably provided enabling an 'inspection of 'the flow of metal into the die so .that the operator may determine both the level of the metal in the dieand the temperature of the flowing metal. To this end an upwardly extending passageway 29 is provided at 'this upper end with a suitable inspection window 30 adapted to withstand the high temperatures present. Through this window the temperature of the metal may be read by an optical pyrometer if desired or a light sensitive cell may be placed there as indicated at 3i for the purpose of automatically regulating the temperature of the metal in the reservoir in accordance with the temperature or the met-a1 sowing to the die. A suitab1e control circuit for this purpose is indicated in Fig. 6 and will be hereinafter more fully explained.

Preferably the die casting apparatus is connected with the metal reservoir and associated parts in a manner to be detached if necessary.

To this end the case 32 housing the passage connected with the ,reservoir i0 is provided with outwardly extending anges 33 at the lower end, which anges are bolted at 34 to brackets 35 of the casing 36 surrounding chamber 24. 'Ihis die portion preferably has a refractory lining 31.

The die casting portion 25 comes in contact with the molten metal during the formation of the-first outer skin. This die portion has water passages 25a through which a stream .of water is continuously passed for the pllIpOse of chilling the die to whatever extent may be desirable.

Between the

die portions

25 and 26 a machined joint 38 may be provided, or a gasket of suitable material, for instance asbestos, may be inserted there. These two die portions are secured together by their anges as by the use of bolts 39, clamps or the like. One of the novel features of my invention is the provision of a. liner 40 in this upper portion of the die where the molten metal rst cornes in contact with the inner walls thereof. This liner must be a good heat conductor and have good refractory characteristics and should have little chemical action upon the metal in contact with it. Preferably also for long life it should be highly resistant to abrasion of the molten metal. Quite a number of materials are suitable for this liner, among them tungsten carbide, silicon carbide, graphite, graphite in copper, graphite and carborundum, carborundurn alone, chrome brick, chrome copper alloys, nickel copper alloys, suchas InconeP' with or Without metallic oxide additions, high chrome steels. Monel metal with or Without chromic oxide, Monel metal with graphite, and similar materials. I prefer to make this liner dil, as thin as is consistent with long life so that the heat conductivity therethrough to the cooled copper Wall will be suiiicient to i'orm a skin on the metal.

I find that the surface qualities of the metal may be varied according to the choice of the type of liner et. For instance a graphite and carborundum liner will give a rough texture to the surface while Monel metal or tungsten carbide liners give a smooth surface.

The die portion 2e may be of one or more sections. -As illustrated I have shown one section split alonga vertical plane into two halves which are machined and bolted together by their ilanges 28e. This die portion is provided 'with water cooling passages 28a. The metal-contacting inner faces ofthe copper walls 28h ii' desired may be formed of graphite in copper so as to harden land increase the life of the inner' surface of this portion of'the die.

While not absolutely necessary to the practical operation oimy die casting operation, I prefer to supply at the exit end of the die the metal constricting portion 21. As shown here, this is preferably of a harder material than the die portions 26. For instance this might be of a harder copper than the rest of the die or preferablywould be of chrome nickel steel or the like and provided the substantially solidiiied metal is pulled out of the die as for instance by the pinch rolls 2B. This prevents any ltearing of the semi-solidified metal in the upper portion of the die.

'I'he die

portions

26 and 21 may be secured together as by their outwardly extending end flanges and by bolts 4i.

Preferably means is provided for so controlling the ow of water through the water cooling pas;-`

sages of the die as to provide a constant rate of cooling of the-metal as it passes through the various portions of the die. If this is done the physical characteristics of the solidified metal will be held constant because of the constant cooling characteristics throughout the length of the die as the metal progressively passes therethrough. To this end I have indicated Asomewhat; diagrammatically in Fig. 2, a. manner of sectionalizing the water cooling of the die and the automatic control of the temperature of each section. To. this end the

cooling passages

25a, 26a, and 21a. are supplied with a cooling medium such as water or the like fromsources 42, and discharge is at 43. Preferably each of these die cooling sections is provided with means for controlling the iiow of cooling medium in response to the temperature of the die walls so as to maintain constant casting conditions. A thermostatic valve 44 is operated by a solenoid 45 which is controlled by a relay 46- which in turn is responsive to the thermostat pyrometer 41 having a pyrometer element embedded in the Wall of the die. A suitable power source is connected at 48 for operating the thermostatic valve and the arrangement of the f parts is such that if the temperature of the pyrometer element 41 rises above a predetermined point, the valve 44 will be opened to admit more cooling medium to the cooling passages, and upon the pyrometer dropping below the predetermined high point the solenoid l5 will be deenergized permitting the valve dfi to return to a predetermined minimum setting. Other speciiic arrangements of the control system for thecooling medium will occur to those skilled in this art and any suitable system is within the scope of my invention.

A suitable control system for holding the metal in the reservoir i@ at a substantiallypconstant temperature is shown' in Fig, 6 where the electric.

furnace high frequency'coil i2 is indicated diagrammatically as being supplied with current of high voltage and `highfrequency from a `suitable source 49. In the supply line` for coll l2 is a relay SII having a contact `Sila and a contactor arm lIlb controlled by` the relay coil. The `contact. `50a is shown diagrammatically and willbe one suitable for the current and voltage handled. When the `control `circuit comes from the secondary, of a transformer connected with a suitable source of alternating current. A rectifier `Il provides a direct current between the conductors Il and 56.

` The line 56 is connected through lines `ITI and 58 so as to energize the coil of :relay `and I8 is 'connected with the anode B2b of the triode. The

cathode 52e isconnected through 'resistance 59 and line GII with line `B and slalso connected through line i I and resistance 62 with the line 55;

Between lines 5I and 6I` is connected the vari-` able resistance i3.A The line B4 connects line Bly and the other terminal of the light sensitive cell IIb. By suitably varying the aperture of the light sensitive cell and the adjustment ofrthejvariable resistance 63, the `cellmay be set to energize the circuit whenthe temperature' of the metal ilowing into the die castingapparatus drops below a pre-` determined point yso as to close theirelay Il and the other hand, if to provide high frequency current'to the coil I2 until the temperature `of the `metal flowing into the die casting apparatus passed a predetermined nigh point at which time the iight sensitive een would be energized and arranged to break contact at relay il `instead of making contact as illustrated in Fig. 6. It will be understood'of coursel that two light sensitive cells might be supplied.

one to cut ofi' the supply of current'to coil I2 if the metal passed abovea predetermined high;

be indirect, that is, from the metal being cast through the die wall to the cooling medlunn Most i metalsshrinkor contract whencooled. This rei suits in a Vdrawingaway of the metalvfrom the cooling walls of the die leavingan air gap across i which heat transfer is greatly retarded.

`It has `been assumed, also, that one faced with the dilemma of the air gap between the cool- I ing walls and ,thehot` metal (as mentioned above) with consequent loss of heat transfer, or die walls which are arranged to bein close contact `with the hot'metal with consequent friction so great I tively high thermalfconductivity so as to mi and keep nlled along the length of the die the shrink- At the same time, this material maybe so selected that it has `lubricating vproper-ties even at the temperature of,` steel iustbelow thesolidus.

Graphite is such a material.` Thus thermal conductivity is increased and friction reduced.

Here Q representsthe quantity of heat passing `through a material of area A and thickness d and having a coeilicient of thermal conductivity K in `the time t, where the opposite faces of the material are subject to temperatures Ti and T: respectively.` t i The coemcient K" for graphite approaches that `of steel at high temperatures just after solidifying. Therefore. if graphite illls the space left by contraction of the first-formed steel skin away from the die wall, the `transfer of heat from the `metal to the wall will continue at almost the same .mately one-ilftiethof the graphite.I 1

Another effect 1 of my improvedA` method and apparatus is an increaseduniformity in the cast metal. Without the use of my improved apparatus the contraction of the 'metal from `the walls supply current to the high frequency coil I2.` 0n` of the idie'leaves the metal in contact with the ydesired the cell might be set` walls at some point and out ofcontact at other points; giving aY very irregular and nonuniform I age cavity caused bythe cooling of the cast metal.

cooling effect with resultant inequalities and imperfections in the metal and very seriously aifect.. ing the life of the die:`

For all of the various reasons previously set forth herein such as loss of heat conducting contact between the metaland the die, hre cracks in the I find that the above named Vfilling materials are best introduced between the metal and the die wall ina nnely divided or powdered form either dry or carried by asuitable vehicle. Hereafterin the specification and claims, the use of i the term powdered" doesk not necessarily refer the first skinhasformed onthemetal and I' desire to include all suitable materials which will withstand the high `temperatures met with at this point and yet which will accommodate itself to the interstices and changing movements between the skin of the metal and the die walls and which will maintain substantially continuous heat conducting contact between the congealing metal and the die walls.

Where' steel is being continuously ast in my novel apparatus I find graphite is particularly applicable because it readily conforms to the interstices between the metal skin and the inner walls of the die. and it has very high heat conductivity. Furthermore the graphite isaI good black body and absorbs heat from the steel vat high temperatures and conducts this heat to the die walls without reecting back upon the steel much of the heat received. The graphite has the additional merit that it contributes -to a smooth surface on the cast steel, remains on the cast steel as a protective film while it cools, and protects the die from heat otherwise radiated from the lsteel'which would produce re cracks and deterioration of the die walls.

After the first thin skin has formed on the metal and it shrinks away from the die wall, if an air gap is present as in the prior art, the thin skin is insuiiicient to support the interior molten mass and the pressure of molten metal above it. The skin is thus subject to distortion and may rupture. Also, if conductivity between the new skin and the cooler die wall is broken by the air gap, the skin is reheated from the molten interior and may remelt in spots causing bleeding. This will produce surface defects and possibly a spongy center. My vinvention supplies a plastic material which lls this space where the air gap was in the prior art between the thin skin and die wall. 'Ihis plastic material maintains thermal conductivity between the metal and die so as to prevent reheating of the skin, and supports the thin skin so as to prevent distortion and rupture.

Any suitable means may be provided for applying the self-accommodating die lining film hereinafter designated lubricant Some oi the materials may be suitably applied by the .use of a power driven screw as illustrated diagram matically in Fig. 2. Here a spiral screw 65 is housed in a cylindrical casing 65 supplied with lubricant material from a source 6l and the screw is driven through gears 68 operated from a variable speed motor 69. This will supply lubricant under pressure to the conduits 1G, the pressure being varied by varying the speed of motor 69. One arrangement of these conduits is shown in the drawings but other arrangements may be used so long as the lubricant is fed to all sides of the cast piece under suiiicient pressure to enter the spaces between the cast piece and the die wal s.

For other lubricants a plunger pump may be used having a bypass opening at a predetermined pressure so that the pump may be run to supply lubricant at any desired pressure. Other materials may be supplied from reservoirs of lubricant vunder pressure such as that supplied from a power driven plunger or. compressed air to supply the lubricant through suitable conduits l to the die. Certain of the lubricants may be mixed with glycerine or other suitable liquid to give them sufcient fluidity.

One form of passageway which I have conceived as suitable for applying the lubricant graphite is illustrated in Fig. 5 Where a groove 'H extends substantially continuously around the inner face of the die wall and is supplied at spaced points vthrough conduits l2 in the die walls connected with the pressure conduits 'lli heretofore described. In such a construction suficient connections l2 are provided to maintain a continuous supply of graphite about the inner periphery of the die at each point selected. The

pressure on the lubricant will be so regulated that at the point 13, Fig. 5, the skin formed onl the solidifying metal 14 will ,not be deformed to any great extent. In other words the graphite will form substantially a continuation of the inner face of the-die at this point and a small lm will be carried alongside the metal as indicated at 15 lling the interstices between the metal and the die wall. This view is somewhat distorted to illustrate the formation of the lubricant lm between the. cast piece and the die wall. As shown in the various views all of the lubricant passages will preferably be arranged with smooth curves so as not to interrupt the ow of the lubricant.

To protect from oxidation the metal flowing from the reservoir I0 through the passage 23 to the die casting apparatus, I may supply to the upper end of the die casting apparatus a suitable gas under pressure as at the connection 16, Fig. 1.

Suitable gases for this purpose are for instance hydrogen. nitrogen, carbon monoxide, carbon dioxide and others which will occur to those skilled in this art. These gases may simply be inert gases as nitrogen or may have a reducing eiect as hydrogen. In the case of nitrogen, oxidation of the molten metal previous to its solidiiication would simply be prevented. In the case of hydrogen not only would this same eiect be produced but any small amounts of metallic oxides present in the upper portion of the die casting apparatus would be reduced. This prevents` the formation of oxides in the die casting apparatus which would have a bad effect upon the physical characteristics of the metal and also upon the surface characteristics of the cast metal and the die walls.

The gas supplied at source 'l5 may be under sulcient pressure to create considerable hydrostatic pressure in the upper portion of the die so as to aid in the passage of the metal through the die and to give a compressing eiect upon the cast metal so as to refine the grain structure thereof. I believe it is novel to act upon the one end of the cast piece with gas under pressure while pulling the other end oi the cast piece as by the pinch rolls 2B and lubricating the passage of the metal through the die. I thus powerfully urge the cast piece through the die without tearingthe metal.

The gas supplied from source 'it may be placed under suicient pressure to bubble through the opening it as the stopper i6 is manipulated and of suicient head to bubble up through the metal in reservoir tti to exert a cleaning eect upon the metal in the reservoir. For instance if hydrogen gas or carbon monoxide were thus passed upwardly through the reservoir it would have a tendency to clean oxides from the metal.

The gas supplied in the upper portion of the die casting apparatus may be of sumcient pressure to pass downwardly between the metal and the inner walls of the die, thus continuously protecting the surface of the solidifying metal from chemical action or from oxidation. At the same time if the gas were hydrogen it would not detract greatly from the heat conductivity between the metal and the die as hydrogen is high in heat conductivity. At the same time this gas under pressure between the metal skin and the Walls of the die would tend to have a lubricating eect, that is it would reduce friction between the metal and the die. A reducing or non-oxidizing gas may be introduced at one or more of the conduits 10 in place of or in addition to the lubricant. i n i A suction pump may be attached at 16 instead of the gas supply. This would create a vacuum in thelupper portion of the `die with consequent removal `of oxygen and variation in characteris-a` i n be any cavity in the center it would be closed tics of cast metal. y

Nothing has been said in detail with regard to the pinch rolls 28 or other apparatus to take care of the metal after it leaves the die as such apparatus is `well known. Generally there would be suitable guides and other'rolls to handle the metal after it passes from the die castingapparatus.

I do notrestrict myself to either partially ori from the die; My process may be operated either way but it is entirely feasible if the metal section is not too thick to have the metal strip substan` tially completely solid when it emerges from the 20 die.` The length yof the die may be varied to obtain the result desired. l Y

While my description has been limited chiefly to the'casting of steel in the form of aslab in `a. vertically arranged die, I desire it understood that I do not limit myself to any of these particulars.

" My improved process and apparatus may be used a for continuously casting other metals and other sections and with the die in various positions.

For instance, in Fig. 1 Ihave roughly illustrated a die section similar to Fig. 3 and having aninner die space for castings, rail section which in practical operation would be slightly over size'so as to permit a nal rolling operation to exact size.

Y. The lubricant supply means is diagrammatically illustrated at 'll and performsthe same function as the similar parts previously described.

The walls of die portion 26 will be shaped according to the characteristics of the metal being cast, always bearing in mind thatif the metal 40 does not shrink enough to allow space for the lubricant illm, then the die walls will `flare outwardly enough to provide-such a space.

In use, the process is started by placing a metal bar substantially of the cross section of the die exit end in the die with its projecting end-between the pinch rolls. Such a bar might be heated to weld with the metal iirst cast,or would carry projections at 'its inner end adapted to bond with the cast metal. Metal flow is then initiated bymanipulating stopper I6 and, after" allowing time for the first lpoured metal to unite with the starter bar, the pinch rolls are started. t

'I'he speed of the pinch rolls is regulated as desired and the level of the metal in the die` controlled by manipulating stopper I6 as advised byf the conditions observed through the inspection window.l i e t i n 4 My improved method f and apparatus may -be operated intermittently or continuously. The lato ter gives greater uniformity in the cast metal.

It results from the use ofthe above` described l process and apparatus that metal may be continuously cast on a1commercial scale with very high quality as -to-internal physical characteristics and surface characteristics of the castmetal.`

Theprotection afforded thewalls of the die gives i cast for an indefinite length of time because I` have overcome those difficulties which heretofore caused stoppage after comparatively short lengths had been cast. A t

Where themetal cast is steel it has few or none `of the defects `heretofore found in usual casting methodsf For instance `there is no pipe in the `steel becausefthe center ofthe cast section is n continuously open to an unlimited supply of metal `at all times until itis'congealed. The 'center is 5 protected against oxidation and if there should and welded bythe constricted exit end 2l of the die. Blow-holes arereducedito a minimum or.

entirely eliminated because ofthe quick freezing `10` of the metal Yand the preventionr of oxidation of the metal so'that any small `holes if formed will be welded together at `the exit end of the die. A very fine crystal `structure results from the fast freezing which makes for small crystals and the 15 uniform n casting conditions provide yuniform crystal structure throughout the length of the metal strip. Because of the close control of the temperature of the metal throughout the entire y process the steel may becast from a mushy state 20 just above the solidus if desired, thus further reducing the freezing time. The fast freezing'lprovided gives little chance rforsegregation and the constant progress of the freezing zone gives auniform distribution of whatever ingredients settle 25 out. Non-metallic inclusions are practically l There is no checking or cracks in the skin ofthe cast metal because of the smooth lubricated walls and the uniform movement during freezingprevents stresses inthe skin;` The constricted die 3" endi21 prevents the pull of rolls 28 tearing-the metal in die portion 26. There are no scabs from splashes during pouringbecause the mold is filled slowl7;and uniformly without much dropping of metal and the upperportion `of the die is hot '4u enough to remelt splashes if any occur.

It should `be clearly understood that if the metal does not shrink sufficiently to provide space for efficiently introducing the vself-accommodating die lining material, then the die walls will be so 4,; proportioned as to providethe requisite space. This may also be the case if the die is made long enough to have the metal fullyl solidified `at its exit from the diei During the latter part of the passage of metal through Such a die, the shrink- 5u age may be very small. `Here again the die walls will be shaped to permit introduction of the plastic die liningmaterial, regardless of the shrinkage ofthe cast metal.` i

There is good authority for `the theory that 55 considerable relative movement takes place `between a die and metal cast init. 'There is expansion and contraction of the die walis'due t0 i the effect ofthe hot metallupon they colder walls. `'Ihere is expansion and contraction of the con- U0 `gealing metal also, because `wherever it touches a cold wall it will immediately shrink away only to later expand outwardly due to reheating or due `to the ferrostatic pressure `of thestill molteninterior even when the skin is ofsubstantial thick- 65 ness. p My invention for the rst time supplies `material between the skin'and die adapted to ll all these interstices no matter how they vary so ,y that the skin of the congealing metal is supported and protected andthefwalls of the die are kept from directcontact withthe hot metal so i that the walls are not galled or abraded or subjected to fire-cracks and hot metal can not stick `to the wall. i

In certain of the claims applicant has defined .passing metal through said die, said die being the die lining material as facilitating the casting of the metal in the die. By this term facilitating" applicant means to cover material which supports the tender skin on the metal against sagging and rupture, which maintains suilicientheat conductivity between therskin and die wall to prevent reheating and remelting of the skin and maintains continuous -progressive cooling, which improves and protects the metal surface, which protects the die surface, or which may lubrlcate the passage of the metal through th What I claim is:

1. Apparatus of the class described comprising a die having a passage therethrough, means for passing molten metal into one end of said passage, said 'die having walls surrounding said passage and adapted to remove heat from said metal to i'orm a solid skin thereon within said passage, a refractory heat-conducting liner on said walls at the entrance end of said passage in contact with said molten metal for forming a rst skin thereon, said liner ending at that point where the rst skin has formed, whereupon said metal shrinks away from the walls of said die passage, and means for thereafter lling the lnterstices between said metal skin and die walls with a heat-conducting material.

2. Apparatus as in claim 1 wherein said filling material has lubricating properties. A

3. The method of continuously casting metal comprising continuously passing metal through a hollow chilled die at a velocity permitting said die to congeal said metal from a molten to at least a partially solid state and filling the space between said congealing metal and said die with a finely divided solid material capable of remain ing solid during the casting operation and capable of accommodating itself to the lnterstices between the .cast metal and die wall.

4. Apparatus of the class described comprising a die having a passage therethrough, means for passing metal through said die, said die being constructed to conduct heat away from said passage at a rate sufficient to form a solid skin on said metal at theexit end of said passage when substantially molten metal is fed to the entrance end of said passage, the relation between said congeallng metal and said die being such that there is a space between said metal and die at the point where the rst skin is formed on the surface of the metal, and means for supplying to said space at said point a powdered material facilitating the casting of the metal in said die.

5. Apparatus as in claim 4 including means for supplying to said space a gas for protecting saidl powdered material against deterioration.

6. Apparatus of the class described comprising a substantially rigid die having a passage therethrough, means for passing metal through said die, said die being constructed to conduct heat away from said passage at a rate suicient to form at least a, solid self-supporting skin on said metal at the exit end of said passage when molten metal is fed to the entrance end of said passage, means for supplying a graphitic compound between said die and the metal passing i through it at a point where a skin has formed on said metal insufficient alone to support the body of molten metal it encloses, said lining supporting said skin and hence the column of metal, and said lining maintaining heat-conducting contact between said skin and die.

7. Apparatus of the class described comprising a die having a passage therethrough, means for constructed to conduct heat away from said passage at a rate sufiicientto format least a solid skinx'on said metal at the exit endof said passage when substantially molten metal is fed to the entrance end oi' said passage, and means for supplying between said skin and die, at points spaced on said die, finely divided solid material facilitating the casting of the metal'in said die and adapted to nil all spaces between saidfskin and die,l said last named means being adapted to vary the pressure at said spaced points, whereby the pressure on said material may be coordinated with the position and condition of the solidifying metal in the die.

- the entrance end of said passage, there being a groove in the inner wall of said die located at a point where a skin has formed on said metal, and means for supplying a fiowable graphitic compound to said groove.

9. The method oi' continuously casting metal comprising continuously passing metal through a hollow chilled dielat a velocity permitting said die to congeal said metal from a molten to at least a partially solid state whereby the metal forms an outer skin from contact with said die during the iirst portion of its passage therethrough, and thereafter continuously supplying between said skin and die a iinely divided solid material capable of remaining solid during the casting operation and capable of accommodating itself to the lnterstices between the cast metal and die wall, whereby to protect the walls of said die from abrasion and galling, and to protect the surface of the congealing metal from run-outs and abrasion.

li). In the method of casting metal continuously comprising feeding molten metal from a reservoir through a substantially gas-tight passageway to one end oi a die which is open at both ends, while chilling the metal in said die and 'drawing it out the other end of said die, the step of supplying .to said passageway a gas under sum cient pressure to cause some of it to pass into the molten metal in said reservoir.

li. Apparatus of the class described comprising a die having a passage therethrough, means for passing molten metal into one end of said passage, said die having walls surrounding said passage adapted to remove heat from said metal to form a solid skin thereon within said passage whereupon said metal shrinks away from the walls of said die passage, and means positioned between the zone where said skin is normally formed and the exit end of said die to fill the interstices' between said metal skin and die walls with a readily conformable material for supporting the solidied surface of the metal being casty surface and said walls from substantially the congealing sone to the exit end of Asazidiiiewith readily conformable material for supporting the solidified surface of the cast metal away( n'om the die walls and for facilitating the movement t of the metal out of the die.` i 13. Apparatus ot the class described compris lng a die having a passage therethrough, for passing lmolten metal intoone end of said passage, said die having walls surroundingsaid ing a die having a passage therethrough, means for passing molteameminto one end or nid passage, said die having walls surroimding said e adapted to remove heat from said metal to form a solid skin thereon within saidpassage,

there being ports through said die walls and communicating with the interior of said die between the zone where said `skin is formed and theexit end orsaid die, and means for supplying to said ports a non-liquid lubricating material.

15. In the ymethod of continuously casting. metal which consists of continuously feeding molten metal to one end of a hollow chilled die at a velocity permitting said die to congeal at least the outer surface of the metal `within the die', and continuously removing the chilled metal at the exit end of the die. the step comprising continuously introducing a non-liquid lubricating material between the vcongealed surface of the metal and the'wall of the die from the zone where said congealed surface normally forms to the exit end of the die.

NORMAN P.