US2195809A - Continuous casting - Google Patents

Description

April 1940- J. o. BETTERTON ET AL 2,195, 09

CONTINUOUS CASTING Filed June 22, 1956 2 Sheets-Sheet 1 INVENTQRS fme dfieiler/azz BYfian/f I'Paian 'K/ ATTORNEY April 2, 1940. J. o. BETTERTON ET AL CONTINUOUS CASTING Filed June 22, 1936 2 Sheets-Sheet 2 #5 2% an m uv INVENTOR Jesse d flellerion yfidH/f ATTORNE Patented Apr. 2, 1940 UNITED STATES PATENT OFFICE}.

2,195,809 oou'rmoous ons'rmc Jesse 0. Bctterton, Metuchen, and Frank F. Poland, Highland Park, N. J., assignors to American smelting and Refining Company, New York, N. Y., a corporation of New Jersey Application June 22, 1936, Serial No. 86,600

12 Claims. (01. 22-2001) This invention relates to the art of continuous effectively solves the problem thereby permitting casting of non-ferrous metals, particularly copcopper and copper alloy shapes of indefinite per and copper alloys, and provides certain imlength to be continuously cast at rates which are provements in that art whereby metal shapes definitely commercial.

of indefinite length may be produced on a com- Investigations and experiments have clearly 5 mercial scale in a truly continuous manner. indicated and demonstrated that mold friction While the invention will be described with refand gas entrapment can be overcome or conerence to the continuous casting of copper or trolled to the extent prerequisite for successful copper alloys, it will be understood that the continuous casting if certain factors or condiprinciples thereof are, for the most part, 'applitions are fully appreciated and observed. That 10 cable to the casting of other non-ferrous metals some of these factors or conditions are more or and alloys whichpresent problems similar to less independent while others are closely interthose encountered in continuously casting coprelated with other factors with respect to the per or its alloys. manner in which the several factors, by their The concept of continuously "casting non-ferproper observance, contribute to the desired re- 15 rous metals such as copper andcopper alloys, sult, will be apparent as the description proceeds. that is, by supplying the molten metal from a These factors and conditions, the importance and reservoir to one end of a diefor mold'having correct observation of which have been amply solid metal in the other end which serves .as a and repeatedly confirmed in actual practice, may

30 plug and to which the molten metal welds as be summarized as follows: go it solidifies accompanied by withdrawal of the 1. Proper preliminary preparation of the copper cast shape at a rate substantially equal to that or copper alloy. of solidification, is indeed an old one and various 2. Introduction of the moltel metal into the and sundry processes and apparatus have been mold in a manner avoiding turbulence of the 5 proposed for its fulfillment. metal therein.

However, whenit is attempted to pursue these I 3. Avoidance of a deep head of molten metal prior art teachings in practice one immediately on that in the mold. finds them fraught with difficulties and obstacles 4. Provision of a mold of proper design in for the satisfactory solution of which one searches which at least the inner surface thereof that their sponsors teachings in vain. Chief among contacts the molten and freshly solidified copper 30 these difliculties and obstacles are: physical uncomplies with certain requirements.

soundness of the cast metal both internally (pip- 5. Proper control of the intermediate zone ing, gas pockets, and other defects caused by which is hereinafter defined and described. accumulation or entrapment of gas) and ex- Before entering into the detailed discussion ternally (cracked, checked or otherwise defective and explanation of the several factors enumer- 5 surface); breakage of the cast shape resulting ated above, it may be said that continuous castin losses due to the breakage itself and othering processes may be roughly classified with rewise highly undesirable because of damage to spect to the manner or method by which at least the apparatus and exposure of the workmen to the major portion of the heat is withdrawn 0 danger by reason of runouts of the molten metal from the molten metal to effect its solidifica- 40 which all too frequently accompany breakage tion as: (a) lateral cooling, that is, by extracof the casting; and the inability or failure of tion of the heat through the mold wall and (b) such proposals, insofar as any of them do prolongitudinal cooling, that is, by extraction of duce any sound metal, to do so as a truly conthe heat through the previously solidified coptinuous and satisfactory commercial operation. per. Naturally there may be said to be a third Generally speaking, investigation has shown class in which substantial heat extraction is that the inability of the prior art processes and accomplished both laterally and longitudinally. apparatus to produce sound castings in a truly However, this is really a matter of degree, since, continuous manner and on a satisfactory comas a practical matter, there is always at least mercial scale may be attributed, either directly some small amount of heat extracted longitudi- 5 or indirectly, to two things: entrapment of gas na ly in any lateral cooling p ss and v in the solidified metal and friction between the v r A c r ly, i seems better r the s k die or mold and th m t l, Th t; i venof clarity to classify all the processes as (a) tion by providing a modus operandi which or (b) according to whether a major portion of 5' eliminates the former and minimizes the latter. the heat or more) is extracted laterally or longitudinally in effecting solidification of the copper. For reasons that will become apparent as the description proceeds, the present invention contemplates a process in which lateral cooling is employed although observance of many of the factors yields improved results in longitudinal cooling processes as well.

For a better understanding of the invention and the roles played by the several factors mentioned, it may be pointed out that all commercial processes for casting copper must deal with metal containing gases, it being well known and generally acknowledged in the art that liquid copper in contact with a gaseous atmosphere will have some gas dissolved or occluded therein. In addition, the tensile strength of copper at temperatures approaching its melting point is very low and hence copper just as it solidifies is extremely fragile. Further, the surface tension of molten copper is low.

Turning now to the various factors already set forth and which are listed without regard to order of importance, the first to be considered is the preliminary preparation of the copper which consists essentially in rendering it substantially gas-free, oxygen-free prior to its introduction into the mold.

It will be remembered that the continuous 'casting process contemplates continuously leading the molten copper from a supply thereof into one end of a suitable mold, the other end of which is closed by previously solidified copper, and causing the molten copper so introduced to solidify and weld to the previously solidified copper, the resulting cast shape of indefinite length being continuously withdrawn from the mold. In other words, the molten copper is formed into a moving column and as one end thereof is solidified and continuously withdrawn. the other end of the moving column is replenished with molten copper.

Now as the copper solidifies, the gases dissolved therein are liberated from the freezing copper and pass into the intermediate zone (hereinafter treated in detail) so that it might seem, at first glance, that castings closely approaching pure cupper in density could be continuously produced merely by freezing the metal from the bottom upward. Unfortunately for the art, the problem is not so simply solved if casting speeds sufficiently high to place the operation on a satisfactory commercial plane are to be continuously maintained. 0ft repeated runs have conclusively demonstrated that failure to effect a substantial degasification of the copper prior to its introduction into the mold invariably invites breakage of the casting with its attendant losses as well as unsoundness in whatever cast shape is obtained.

The contribution which prior degasification of the copper makes to the success of the continuous casting operation is no doubt due in a large measure to the fact thatthe liberation of the gases occurs at the freezing line of the metal in the mold which is the very place where the newly solidified copper exhibits its maximum degree of fragility. Hence, the clear indication is that the less gas there is liberated at this delicate zone, the less chance for gas entrapment or for stresses and strains to be set up incident to gas movement. Further, deoxidation of the copper prevents oxidation and consequent roughening of the interior or the inner surface of the mold, which as hereinafter shown is of carbon, thus reducing mold friction and minimizing surface imperfections in the, casting which otherwise would result from the roughened surface.

The treatment of the copper preparatory to introducing it into the mold may be effected in accordance with usual refining practise by first blowing it with air until the hydrogen and sulphur are expelled as completely as possible and then poling the resulting low set copper to a point where cast samples will have a density of at least 8.50. The resulting copper, though commercially gas-free, still contains a small amount of oxygen (less than 0.01%) and this is removed n any suitable manner as by incorporating small but sufflcient amounts of a metallic deoxidizer therein. Phosphorus is an efficient deoxidizer and if used is preferably employed in a manner which imparts to the copper an approximate residual phosphorus content of from 0.001% to 0.005%. The copper so prepared being substantially gas-free, oxygen-free is now suitable for introduction into the mold. It will, of course, be understood that if it is desired to cast copper alloys instead of copper, the necessary alloy constituents for the particular alloy desired may be incorporated in the prepared cooper prior to introducing the metal into the mold.

The second factor enumerated above is that of introducing the molten copper into the mold in such manner that turbulence of the metal therein is avoided. This factor is closely related to the extremely fragile nature of the freshly cast or newly solidified copper, it having been found that breakage of the newly cast shape is greatly aggravated when copper is introduced in a manner imparting turbulence to the metal in the mold.

While various methods and means will, no doubt, occur to those skilled in the art for maintaining the metal in the mold in a quiescent state, one manner of introduction that has proved entirely satisfactory in actual practise is to introduce the prepared molten copper into the receptacle or reservoir in which the mold is mounted at a point sufilciently remote from the mold that turbulence of the metal incident to its introduction into the reservoir will have subsided before the mold entrance is reached.

Failure to observe this factor in introducing the molten copper is to invite breakage of the casting and consequent interruption of the continuity of the process. Furthermore, cessations in operation occasioned by breakage of the casting are, of course, of a much more serious nature than a simple discontinuance of the casting process but even to practise the latter to avoid breakage when adding copper to the receptacle would mean loss or delay each time in the subsequent starting up period as will hereinafter be apparent.

The third factor to be considered is that of avoiding a deep head of metal on that in the mold, which factor is probably closely related to both the low surface tension of the molten copper and the low tensile strength or fragility of the newly solidified copper.

It has been observed that whenever a deep head of metal is present above the copper undergoing solidification in the mold, there is a marked tendency of the casting to emerge from the mold with a rough, checked or cracked surface and even to break entirely in two.

Considering the fragile nature of the freshly solidified copper and the low surface tension of the molten copper, the explanation of the checked or cracked surface may be that the hyaioaaoo drostatic pressure exerted by the head of metal above the mold causes the molten and solidifying copper therein to-spread out and that with an excessive head of molten copper above the mold for the diameter of the particular casting there is produced such a degree of friction between the mold and metal as to cause a slipping between the crystals of the copper before same are thoroughly set through complete freezing. However, the exact cause or explanation of such defects is immaterial, it being a fact that whenever the depth or head of molten copper becomes excessive for the diameter of the rod being cast, the imperfections hereinbefore noted result.

The working range of the depth or head of metal may be said to vary from such depth .as will fill the mold without turbulence, as the minimum, to such depth as will just fall to produce the imperfections noted, as the maximum. A safe working rule is to maintain the head of molten copper above the mold between the approximate limits of one inch minimum to six inches maximum as same has been found in practise to fulfill the requirements for any diameter casting produced bythe continuous process.

The fourth factor concerns the provision of a suitable mold, experience having shown that for at least that surface of the mold which contacts the copper in the vicinity where solidification of the copper is effected, particular care must be exercised both in the selection of the material therefor and in the preparation of same.

Because of the low surface tension of molten copper, it tends to flow into any surface imperfections such as cracks, pores or other irregularities in the interior mold wall and by solidifying therein to produce fins or other irregularities in the casting which, by reason of the increasedfriction between the copper and the mold, lead to fracture of the casting. It should be mentioned in this connection that friction between the mold wall and the newly solidified copper must be maintained at the lowest feasible minimum or failures in the process will inevitably result by reason of the low tensile strength of the newly solidified copper.

In view of what has just been said it will be clear that the interior surface of the mold which contacts the molten and newly solidified copper should beas mechanically perfect as it is possible than 20% with pore spaces of 40 microns maxicommercial results particularly in a process such as that of the invention which employs lateral cooling.

In continuously casting copper, the molten copper must, of course, be cooled from the liquid to the solid phase. The initial ,cooling extracts the superheat from the metal thus reducing its temperature to the melting point and further cooling, by extracting its latent heat of fusion,

to herein as the intermediate zone and the extent of the intermediate zone, that is, the distance between two parallel planes defining same (one plane wholly in the molten phase and the other wholly in the solid phase) is referred to in the present description and appended claims as the depth" of said zone.

While experts may perhaps differ as to the actual physical condition of the copper in this intermediate zone, same is not of importance in view of actually observed results which show the intermediate zone to be the zone of gas entrapment. Numerous specimens of cast copper prove conclusively that as themetal freezes, the gases dissolved therein are liberated incident to the solidification of the metal and pass into the intermediate zone. If the intermediate zone is properly controlled as herein provided, sound castings may be continuously produced at rates which are definitely commercial; if it is not so controlled failure ensues.

As hereinbefore indicated, the present invention contemplates lateral rather than longitudinal cooling, that is, the extraction of heat from the copper in order to solidify same is accomplished laterally through the mold wall. This is significant because while it has long since been proposed, the obstacles which it presented to "commercial adaptation were apparently considered insuperable by those in the field as witnessed by the later advent into the casting art of the longitudinal cooling principle. Results obtained by the present invention, however, show that if the factors heretofore discussed are observed and the intermediate zone regulated or controlled as next disclosed, sound copper castings can be continuously produced at commercial rates materially above the inherently limited production of any known longitudinal cooling process.

It has been found that if the intermediate zone is at all times maintained such that the crystals of the cast copper are disposed radially, that is, a structure in which the crystals are inclined in predominating numbers at an angle of 45 or more to the axis of the billet or rod, such inclination being upward from thecircumference of the cast shaped toward the freezing surface of the copper, sound castings can be continuously produced indefinitely, there being no entrapment of gases if the intermediate zone is so maintained as to produce such radial crys tallization.

The production of only sound copper castings through control of the intermediate zone to maintain radial crystallization whereby no gases become entrapped may perhaps be explained on the basis that in a lateral cooling process the copper next adjacent the mold wall through which the heat is extracted will be the first to solidify while that nearest the center of the mold will be the last to solidify. This means, then, (assuming a vertically disposed mold) that with lateral cooling the freezing line will be of a V- shaped nature as contrasted to a horizontal freezing line in a normal, longitudinal cooling process. From this it appears reasonable to conclude that when entrapment of gases occurs it is because the inclination of the V-shaped freezing line is so steep that the gases passing into the copper in the intermediate zone as they are liberated from the freezing metal, cannot escape before the copper in the intermediate zone is itself frozen. This view can be and is supported by actual observation inasmuch as the crystal structure of copper indicates the direction of heat flow during the freezing process.

Stated in a somewhat different manner, it has been definitely established that to insure the continuous production of a sound casting, the intermediate zone must be maintained below a maximum depth. While this maximumdepth may vary somewhat with difl'erent metals, it has been found that for copper, the intermediate zone must be restricted to a depth not greatly in excess of the diameter of the casting if entrapment of gas is to be avoided. It is, however, a safe working rule, for other non-ferrous metals or alloys because, even though the depth may be increased for some (e. g., those containing no gas or which can be completely degasifled by preliminary treatment), it has been found in actually casting various alloys that the operation can be continuously conducted at commercial speeds by I employing the diameter" 'rule.

The maintenance of a radial crystal structure, or control of the intermediate zone within a sufficiently shallow depth, has been found to be a function of cooling or heat extraction and the process of the invention conclusively demonstrates that in order to obtain high casting speeds or rates which are so much desired, a rapid cooling or solidification of the copper must be effected in order to maintain the proper intermediate zone. In fact, given proper observance of the other factors set forth, there is every indication that the only limitation, other than die friction, upon the casting speed (rate of withdrawal of the casting from the mold) is that of the rate of heat extraction. In other words, the casting speed can be said to depend upon how quickly the heat from the molten copper can be withdrawn through the mold wall and dissipated. The pertinency of the proper mold construction and provision for its vigorous cooling in this connection will, accordingly, be apparent.

A feature not heretofore separately discussed but which is closely related to the control of the intermediate zone and the successful conduct of the process, is the proper control of the casting speed. It is perhaps clear in view of what has already been said that the casting speed is dependent upon the rate of cooling and, hence, must not be so great as to deepen the intermediate zone past its maximum depth. However. there are other facts worthy of specific mention with regard to initiation of the operation. It has been found in practice that the full, commercial casting speed must he arrived at only by slow, gradual increments and without any sudden jerking of the casting being withdrawn and that when the higher speed is once attained the continuous withdrawal of the casting must be accomplished in a steady, uninterrupted manner. If this is not observed, breakage of the rod will result by reason of the low tensile strength of the newly solidified copper in the mold.

Further, in initiating the casting operation the rate of cooling must be adjusted with respect to the casting speed and the two correlated in order to attain the higher commercial speed desired. One of the most important reasons for this resides in the fact that if the full cooling rate is employed at such time when the casting speed is necessarily low, there is real danger of the copper freezng-above the opening leading from the reservoir of copper into the mold thus causing the casting to break as same continues to be withdrawn from the mold. On the other hand, if the intermediate zone is permitted to exceed its maximum depth through insuffcient cooling, gas entrapment, attended by the production of unsound metal or breakage of the casting, will result.

While the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself and the manner in which it may be practised will be-more readily understood by reference to the following description taken in connection with the accompanying drawings, in which Fig. 1 represents, diagrammatically, a type of casting furnace and related assembly which may be employed in practising the invention, the view showing the casting furnace in longitudinal section;

Fig, 2 is an enlarged sectional elevation of the mold illustrated in Fig. 1, showing the details of the mounting of the mold in the casting furnace and the cooling arrangement therefor;

Fig. 3 is a view similar to that of Fig. 2 showing the cooling jacket for the mold in a lowered position;

Fig. 4 is a sectional plan view taken on the line 4-4 of Fig. 2;

Fig. 5 is a section elevation of a somewhat different type of mold from that shown in Figs. 2 and 3.

Like reference characters denote like parts in the several figures of the drawings.

Referring to Fig. 1, It indicates generally a casting or holding furnace having side walls, end walls I! and I4, bottom l6 and roof l8 and an arch 2| extending transversely across the furnace near the charging end thereof. A charging port 22 is positioned in the roof I8 while burner opening 24 and flue 26 are provided in end walls I! and II, respectively. The bottom of the furnace and the side and end walls to a position above the metal line 28 of the furnace have a carbon lining 30. A charging spout or ladle 32 communicates with the interior of the furnace at its firing end while a normally closed tap hole (not shown) leads from the interior of the furnace to spout 34 at the flue end of the furnace.

The mold IS in which the copper is continuous'ly cast is mounted in an inverted cup-shaped holder 38 which in turn is positioned and secured in the floor of the furnace by suitable means, such as bricks ill and refractory cement, at a point remote from that at which the molten metal is charged to the furnace [0. A variable screw 42 equipped with control wheel 44 is supported by brace 46 and connected to water jacket ll for adjusting the latter with respect to the mold 36. Adjustable grooved rolls 66 for withdrawing the cast billet or rod 62, die SI and reel 66 are appropriately indicated.

Referring to the detail drawings, particularly Figs. 2 and 3, it will be seen that the mold 36, which is constructed from the special grade of dense graphite hereinbefore specified, is countersunk in and mounted flush with the top of the holder 38. A look nut 58 secures the mold in the holder. Completely surrounding mold 36 is the relatively thick-walled water jacket 48 made from a metal of high heat conductivity such as forged copper and provided with water inlet 60 and outlet 62. v

To insure a close fit between water jacket and mold when the former is in its uppermost position as shown in Fig. 2, as for normal full speed operation, but at the same time to provide for ready lowering of the jacket as shown in Fig. 3, as for less cooling when initiating the operation, both water jacket and the thin-walled portion of the mold are slightly tapered as indicated in the drawings thereby permitting them to be adjusted with respect to each other by raising or lowering the jacket by turning the screw-42.

Below the mold 36 and secured in place by any suitable means (not shown) is mold extension 64 shown as comprising two half sections 66, 68 yieldably joined by an ordinary bolt and spring arrangement as illustrated in Figs. 2 and 4. Each section of the mold extension is provided with a water inlet 16 and an outlet 12. The mold extension is appropriately of copper and has a graphite liner I4.

Fig. 5 shows a somewhat different type of mold 16 and water jacket 18, the former having a wider bore above the freezing zone than does the mold shown in Figs. 2 and 3 and the jacket is shown as tightly shrunk on the mold although it is obvious that the water jacket and mold may be made adjustable with respect to each other in the manner illustrated in Figs. 2 and 3. Otherwise the constructions are essentially the same. In all three figures, the intermediate zone is diagrammatically indicated by reference character 66, 62 being the solidified casting and 82 the fully liquid metal.

Employing apparatus such as just described, the invention may be practised as follows: the copper after being brought to the commercially gas-free state and deoxidized, which may be accomplished in the manner hereinbefore disclosed, is charged to the casting furnace or reservoir In via port 22 through the deep bed of carbon 84 which is preferably pre-ignited charcoal of low sulphur content as is also the layer 86. The copper in the furnace l6, which is kept in a fully liquid state by a burner (not shown) positioned, in the opening 24, is maintained at a proper level, that is one at which the'head of metal above that in the mold 36 is'not excessive, by appropriate additions from time to time. It is to be noted that turbulence of the copper in the mold 36 is avoided by positioning the mold in the floor of the furnace at a point remote from the charging end of the furnace. A plug extending upwardly into the mold and which is appropriately the last part of the casting from a previous run prevents the copper from being exited through the mold during the initial charging of the furnace before the casting operation is started.

In starting up, cooling water is circulated through the water jacket to solidify the copper in the mold and weld it to the rod 62 which is slowly withdrawn from the mold by rotation of the grooved rolls 66, it being understood that said rolls may be adjustable to each other for accommodating castings of diiferent diameters and that either roll may be power driven in. a known manner as by a variable speed motor coupled to a speed reducer and under a suitable rheostat control.

To bring the casting speed up to full commercial operation, the casting is steadily withdrawn at gradually increased rates simultaneously with increased cooling of the mold for the reasons heretofore explained. Different means may be employed for correlating the rates of cooling and withdrawal during this period. With a mold such' as is shown in Fig. 5 where the water jacket is tightly shrunk on the mold, it is best accomplished by regulating the rate at which water is circulated through the jacket. In an assembly such as that shown in Figs. 2 and 3, it is preferably accomplished by starting the operation with the jacket in a lowered position as illustrated in Fig. 3 and gradually raising it into. closer proximity to the mold wall as the rate of withdrawal of the casting increases until it at last snugly fits the mold wall and exerts its maximum cooling efllciency at which time the casting speed will be at full, commercial rate. One advantage of the adjustable water jacket is that the same vigorous flow ofwater can be maintained through it at all times as the rate of cooling is controlled by simply altering the space between jacket and mold as illustrated.

From the mold 36 in which the proper intermediate zone is maintained as before explained and the copper solidified, the casting is withdrawn through the mold extension 64, which being in sections, yieldably interconnected as shown, is self-adjusting to the rod produced by the particular sized bore of the mold being employed. Inasmuch as the formation of the casting is, and must necessarily be, performed in the mold 36 if sound copper castings are to,be obtained, the water-cooled mold extension is not absolutely necessary. However it is highly desirable as a safety precaution as it precludes runouts in event of breakageof the casting and it also serves to prevent oxidation of the hot casting which would otherwise occur as it issues from the mold, the metal being and remaining bright as it emerges from the mold extension, thus dispensing with any necessity for pickling operations.

It may be here noted that while the mold 36, or at least the inner surface thereof in the case of a composite mold, is made-from the special grade of dense graphite previously mentioned, ordinary grades of graphite may be used to line the mold extension as the copper has already passed through its molten and critically fragile state by the time it enters the mold extension. In this same connection it will be observed that as a matter of terminology the word mold" is used to denote the apparatus in which the physical solidification of the copper is effected to clearly distinguish it from any similar structure in which this delicate operation is not performed such as the "mold extension herein which does, however, cool the hot casting.

Passing from the mold extension and through the rolls 50, the casting 52 may be disposed of as desired in manners well known to the art. For example, it may be drawn through adie 54 or a series of dies and wound onto reel 56 or it may be severed by a suitable saw arrangement into desired lengths as it emerges from the rolls 50 as may well be the case in casting, say, three inch billets.

It will be understood that various modifications and changes in the construction of equipment as well as variations in the details of operation thereof may be indulged in or practised without departing from the invention. Some are shown in the drawings and others will, of course, occur to those skilled in the art. As to the former, it may be said that in constructing the mold shown in Figs. 2 and 3 it may be made with a straight bore except for a slight inward taper extending upwardly from the water jacket to the mouth of the mold, this taper being approximately one quarter of an inch per foot. When heated to operating temperature, expansion reduces the taper so that the mold oifers a substantially straight-walled bore to the copper passing therethrough.

Fig. 5 illustrates a mold with an enlarged opening which in practise apparently offers some advantages in casting rod of small diameter by facilitating gas escape and minimizing agitation of the copper in the intermediate zone incident to gas movement. on the other hand, due to the offset in such a mold immediately above the intermediate zone, greater care must be taken in correlating the rates of cooling and withdrawal particularly when starting up to avoid "freezing the apparatus.

Also while the mold wall should be as thin as possible to facilitate the high and rapid cooling rate demanded if the intermediate zone is to be properly controlled at full commercial casting speeds, a much thicker graphite lining may be employed in the mold extension. Also instead of having one relatively long multiple-pieced or even one-pieced mold extension, two or more shorter ones can be employed.

. It may also be pointed out that in the particular type of mold mounting illustrated in the drawings, the sides of the holder 38 taper outwardly and downwardly which construction makes for ease in dismounting same when this becomes .necessary. Further, by reason of the mold being of graphite, it is well in practise to maintain a reducing atmosphere in the space within the holder where the mold is exposed to prevent oxidation of same.

That copper can be continuously cast at commercial rates through the use of the invention has been amply demonstrated. For example, using a mold having a straight bore of one inch and a mold wall only one quarter of an inch thick around which was shrunk a water Jacket three inches long through which water was circulated at the rate of 70 pounds per minute, a casting speed of 20 inches per minute was easily maintained with the production of sound, dense, one-inch diameter copper rod of a specific gravity exceeding that 01' rolled annealed copper, being over 8.93, the specimens of the rod so tested showing a specific gravity of at least 8.95. In a somewhat similar run on copper-bronze, a casting speed of approximately 30 inches per minute was successfully maintained. As to the truly continuous nature of the process, little need be said further than that rod approximately half a mile in length has been cast without a single break and that up to the point when the operation was finally voluntarily shut down, sound, dense rod was being continuously withdrawn. It may be mentioned that that particular run was started on copper and finished on copper bronze,

the change being effected without interrupting the continuity of the casting process.

It has already been indicated that in addition to copper the principles of the invention are applicable to copper alloys and other nonierrous metals or alloys thereof, the continuous casting of which offers problems of a similar nature to those encountered in continuously casting pure copper. Among those which have already been successfully cast in accordance with the invention are: aluminum, copper-tin-tellurium, copper-silicon-tellurium, copper-nickel, copper-silicon, phosphor-copper, zinc-copper and alumimum-copper.

The castings produced in accordance with the present invention possess numerous advantages, many of which exist by reason of the radial crystal structure of the product. Thus, in rolling and annealing, the structure produced is one in which the crystals are random and equiaxed in orientation thereby producing in the product uniform forming qualities in all directions which is highly desirable in the production of articles with a rounded periphery. This is a definite advantage over a longitudinal crystal structure wherein the crystals are large and are oriented in a uniform plane and direction and retain such directional orientation even when rolled and annealed.

Of particular importance among the new results attainable by the process of the invention is the production of a new metallurgical product comprising copper and 0.001% to 0.005% phosphorus having a density of 8.93 or more 8.95 being common in practise) and possessing a radial crystal structure, that is, one in which the crystals are inclined in predominating numbers at an angle of at least 45 to the longitudinal axis of the casting; such product having been found to possess unexpected properties which render it markedly superior to any other copper product heretofore known for a host of uses. Such product can be readily cast in accordance with the invention, the proper phosphorus content being supplied when deoxidlzing the copper prior to casting.

What is claimed is:

1. The process for casting non-ferrous metals and alloys which comprises degasifying same. maintaining the metal in its degasifled state and confining it as a moving column, cooling to the column such that, at the rate of casting employed, the intermediate zone is no greater than the minimum cross-sectional dimension of the column and radial crystallization of the metal as it solidifies is eii'ected, and maintaining the metal in the column in a quiescent state by continuously feeding additional degasified metal thereto without turbulence.

2. The process for continuously casting copper and copper alloys which comprises refining same to render itcommercially gas-free and deoxidized. establishing a moving column of the refined metal under substantially atmospheric pressure. withdrawing heat laterally from the moving column at such rate that the depth of the inter mediate zone is less than the minimum crosssectional dimension of the column and the metal solidifies with a radial crystal structure, and replenishing the supply of turbulence to the moving column of metal.

3. In a continuous casting process for nonferrous metals and alloys in which solidification of the metal is efi'ected by laterally cooling a .moving, vertical column thereof, said column beapplying lateral refined metal without I molten metal disposed above the column and from which the column is replenished, that improvement which consists in maintaining the head of the metal above the column below an approximate maximum depth of six inches throughout the casting process, whereby surface imperfections in the cast shape are avoided.

4. The process according to claim 3 characterized in that metal is added to the supply above the column without imparting turbulence to said column and while maintaining the movement thereof.

5. The process for casting copper and its alloys which comprises continuously supplying the metal to be cast to one end of a jacketed mold, continuously circulating a cooling fluid through said jacket at a rate suflicient to maintain the intermediate zone at a depth substantially no greater than the shortest cross-sectional dimension of the mold cavity and to solidify the metal with a predominantly radial crystal structure, and continuously withdrawing the fully solidified casting from the other end of said mold.

6. The process for casting nonferrous metals and alloys which comprises continuously supplying molten metal to a vertically disposed mold, continuously withdrawing solidified metal from said mold, and continuously extracting heat from the metal laterally to the direction of movement of the metal at a rate such that the intermediate zone between the metal in its molten and solidified states is constantly maintained at a depth not substantially greater than the diameter of the casting.

7. The process for casting aluminum which comprises continuously supplying molten aluminum to a vertically disposed mold, continuously withdrawing solidified aluminum from said mold, and continuously extracting heat from the aluminum laterally to the direction of movement of the aluminum at a rate such that the intermediate zone between the aluminum in its molten and solidified states is constantly maintained at a depth not substantially greater than the diameter of the casting.

8. In a process for casting copper and copper alloys in a continuous manner by laterally extracting heat from a moving, vertical column of the molten copper or copper alloy, the improvement which consists in so correlating the rates of cooling and of movement of the column that the intermediate zone between the molten and solidified states of the copper or alloy is maintained at a depth not substantially greater than the diameter of the moving column.

9. In the process according to claim 8, the improvement that consists in continuously replenishing the metal of the column without turbulence thereto and while continuing its movement.

10. The process for continuously casting nonferrous metals and alloys which comprises supplying the molten metal to the upper end of a vertically-disposed mold, extracting from the molten metal through the mold wall at least a part of the heat required to be dissipated for full solidification of the metal while maintaining the intermediate zone between the metal in its molten and fully solidified states wholly within the confines of the mold and at a depth not substantially greater than the minimum cross sectional dimension of the casting, and withdrawing the fully solidified casting out of the lower end of the mold.

11. The process for continuously casting copper and its alloys which comprises supplying the molten metal to the upper end of a verticallydisposed mold, continuously forming the molten metal into a fully solidified casting wholly within the confines of the mold by laterally cooling the same and while constantly maintaining the intermediate zone between the metal in its said fully molten and fully solidified states at a depth substantially no greater than the minimum cross sectional dimension of the casting, and withdrawing the fully solidified casting from the lower end of the mold.

12. The process for continuously casting nonferrous metals and alloys which comprises confining the molten metal as a moving column, and transforming same into a moving column of fully solidified metal prior to emergence from confinement by extracting substantially all of both the superheat and the latent heat from the molten metal in a common path of heat fiow transversely to the direction of movement of the column, the intermediate zone in the column being constantly maintained at a depth substantially no greater than the minimum cross sectional dimension of said column.

JESSE O. BETIERTON. FRANK F. POLAND.

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