US1982762A - Method for casting metallic annuli - Google Patents

Description

' 1934- N. F. s. RUSSELL ET AL METHOD FOR CASTING METALLIC ANNULI 2 Sheets-Sheet 1 Filed Jan. 10, 1934 mVENTbRs v rman Z 5. Emsscli fieafienb/f azalggezzzezg, M19444? A TTORNE Y.

3934* N. F. s. RUSSELL El AL METHOD FOR CASTING METALLIC ANNULI 2 Sheets-Sheet 2 Filed Jan. 10, 1934 I I I IWIJI I I I I I 1 INVENTORS Mrinan 15: fiusscll fiederic/i aLm g'eizez g.

ATTORNEY.

Patented Dec. 4, 1934 PATENT o v v 1,982,762 METHOD roa CASTING METALLIC ANNULI Norman F. S. Russell and Frederick C. Langenberg, Edgewater Park, N. 1., assignors to United States Pipe and Foundry Company, Burlington, N. J., a corporation of New Jersey Application January 10, 1934, Serial No. 706,036

2 Claims.

Our invention relates to that method of casting metallic annuli such as pipes and, particu'- larly, cast iron pipes, in molds formed of compacted non-conducting and refractory materials such as green sand molds or molds of a more permanent character designed for repeated .use and made up of a mixtureaof materials which, on being baked at proper temperatures, will form a hard sinteredmass. 'Asheretofore practiced, a considerable amount of adherence occurs between the casting formed in such molds and por-' tions of the mold surface, with the result that the surface of the casting is liable to be undesirably rough and-with the further result that the mold surface is impaired and roughened and either entirely ineffective for subsequent use or so defectively effective as to produce in subsequent uses more defective pipes or annuli. It has been attempted to improve the character of the casting and increase the life of the moldby spraying the inside of the-mold with a liquid vehicle charged with finely divided mold coating material so as to form a coating, which, after the drying of the vehicle, is hard and compact, but our experience is that coatings so'applied are apt to rather increase than diminish the liability to form rough castings and defective molds. It has also been attempted to increase the smoothness of the casting and the durability of the mold by dusting, so to speak, the inside,

of the mold with finely divided mold coating material, generally, by shaking a bag of loose material containing the finely divided coating material over the mold but while this method of coating the mold' does, in certain cases, produce an appreciable improvement in the smoothness of the casting, it cannot be relied upon to fill up thedepressed surfaces which occur in all molds of the character in question or to prevent adherence between the portions of the mold substance proper and the casting which brings about roughness in the casting and injury to the mold;

The object of our invention is to-provide certain improved steps in theapplication of a coating to molds of the kind in-question and in the 1 casting ofthe metal in contact with the coated mold which will result in a substantial elimination of the danger of adherence between the mold surface and the casting and in the production of an exceptionally smooth casting and its withdrawal from the mold with aminimum of injury to the mold and we have discovered that by progressively directing against contiguous portions of the molda jet of a dry carrier gas charged with dry finely-divided particles of mold FFIcE pressed portions of themold sur smooth inner surface flush with face and form a or entirely submerging the more elevated portions of the mold and that by casting the molten metal in a so coated mold, little or no adherence takes place between the metal of the casting and the materials making up, the mold proper and that such particles of the finely divided coating material as may adhere to the casting are, for the most part, easily brushed ofi so that the resultant casting is remarkably smooth and free from adherent material and that, .at

the same time,

the avoidance of adherence between the materials of the mold proper and the casting permits the withdrawal of the casting with the. least possible injury to the mold surfrom the mold face so that the useful life of the mold is materially increased, that is, it is made possible to cast a greater number of annuli-in a mold coated in the manner which we have has heretofore been practicable.

The coating of finely divided indicated than dry coating material deposited on the mold by the jet of dry carrier gas is distinctly hydroscopic and where j the atmosphere is charged with considerable water vapor there is a liability for the coating to lose its dry character by absorbing a considerable amount of water, the presence of which in the'coating is highly detrimental as during the casting operation it is converted into steam which produces a rough and pitted surface on the casting and may even result in blow holes in the casting. It is necessary, therefore, that the casting should take place while the coating of finely divided dry coating material is sensibly dry and this is most effectively and satisfactorily insured by casting the metal in the prepared mold fairly promptly after the mold and before the coating has come sensibly wet, although it is in case the coating has become coating of the had time to bealso practicable, sensibly wet, to

drive off'the excess moisture by'heat.

In our Patent Number 1,949,433, granted March 6, 1934, we have described and claimed our invention whichconsists, generally speaking, in depositing a coating of finely divided rot dry coating material upon the surface of an externally cooled metallic pipe of a jet of carrier gas charged mold by means with finely divided dry mold coating material directed progressively against contiguous ar eas of the mold of coating material.

until'the so treated mold surface is coated also made up, to a considerable degree, of films of the carrier gasadhering to the dry particles The essential function of the so applied coating in the case of externally cooled metal molds'is to effect such a retardation in heat transfer from the molten metal to the 'mold as will result in the formation of what is generally known as a chill on the outer surface of the pipe or annulus but our method asdescribed in our said former patent'also lends itself very effectively to the formation of a pipe casting which is not only free from chill .but

I has also an entirely novel structure in that the resulting pipes are essentially made up of an outer zone consisting preponderantly of compacted interlaced dendrites of ferrite and/or pearlite without unified directional tendency and an innerzone of graphitic formation free from dendritic formations, the resultant pipe being entirely machineable, highly resistant to impact shocks and in other respects a decided improvement 'upon pipes as heretofore manufactured, particularly those made by the centrifugal process; This-new pipe structure forms the subject matter of our co-pending application, Serial Number 652,160.

' In the case of pipes cast in molds made up of compacted, non-conducting and-refractory'materials, there is no liability for the formation of a chill and the pipe structure throughout is graphitic but, as heretofore cast, such pipes were very liable to have a roughened exterior surface of adhering particles or portions of the material making up the mold and the roughened surface of the pipe seriously impaired both the shock resisting capacity and tensile strength of the casting and we have found that by coating the mold in the manner which we have described and casting the pipe .in contact with the dry coating we not only increase the life of the mold the inner surfaceof the mold a considerably greater amount of the finely divided dry coating material per unit of area than was desirable or indeed'practicable in the case of metal molds. -This is, no doubt, to 'a; large/extent, true becausei'of the irregular surface to which the coating is applied and because our method of applying the coating progressively fills up the' depressed portions of the mold in the course of forming a smoothcoating and it is also no doubt true that the irregular surface to which the coating is applied forms a better anchorage for. the coating, rendering it less liable to flake off or to be displacedby the impact of the molten metal upon it. The quantity of coating material applied should be such as will fill up and level off the depressed portions of the mold and 'come at least substantially flush with the higher portions and preferably even the highest portions of the mold surface should be covered by the coating though not to any considerable depth.

Whilein the case of metal molds, t e preswith a thin coating of the finely divided dry coating material which coating, for the best results; is

ence of occluded films-of the carrier gas as a constituent portion of the coating plays a not' unimportant part in the effectiveness of the coating and it is, therefore,-desirable to pourthemolten metal in the mold as soon as possible after the coating is deposited upon it, in the case'of sand molds or-the like the presence of the occluded films of carrier gas in the make-upof the coating, whilewe believe it to be advantageous, is by no means as important as in the case of the metal molds and it is, therefore, practicable to coat the molds considerably before the time at which the metal is poured into them before casting and even to coat the mold before it is connected with the centrifugal machine incases where the pipe is to be cast centrifugally.

While our invention is particularly useful as used in connection with the centrifugal casting of pipes or annuli, it is also usefully adapted for pit casting in which case, of course, cores are used to define the inner surface'of the pipe.

It will be understood from what we have said that our invention consists in applying to a pipe mold formed of compacted non-conducting refractory materials a coating of loosely adherent and loosely coherent particles of finely divided dry coating material by progressively directing against consecutively contiguous portions of the mold a, jet of a dry carriergas. charged with finely divided particles of dry coating material and then pouring molten metal in contact with the sensibly dry coating deposited upon the surface of the mold and preferably, though not exclusively, in carrying out these method steps in connection with centrifugal casting of metallic annuli such as pipes.

Withregard to the character of the coating material to be applied tothe mold surface as described,ipretty much any finely divided mold coating material can be used which will not when exposed to the temperatures brought about by its contact with the molten metal, notably adhere to the casting or to the materials of which the mold proper is made. Finely divided ferro-silicon is well adapted for our uses as are also finely divided particles of sea coal, foundry talc, graphite, powdered anthracite, silica flour. In an application of the coating by means of a jet of carrier gas, it is necessary that the should impart to the finely divided particles of dry coating material with which it is charged, suflicient energy to cause these particles to impact against the mold surface while at the same time the volume and velocity of the jet of carrier gas must beso regulated that the gas itself will not impact against the mold surface with sufflcient energy to blow away the particles of coating material deposited on the surface and built up into a coating upon the surface.

Where a stationary mold is used as in the pit casting of pipes, the molten metal is poured in the usual manner and where the annuli-are cast centrifugally the metal may be poured into the mold in any convenient way.- 1 Thus, the metal may be poured progressively through a runner into a relatively retractable mold as described,

for example, in the de Lavaud Patent 1,398,008

of November 22, 1921, or a dump trough charged with molten metal may be introduced into the mold and tilted to discharge its contents more or less simultaneouslyalong the length of the mold as, for example, is described and shown in the patent to Millspaugh, 1,686,624 of October- 9, 1928, or, again, the metal may be charged into the spigot end of the mold which is preferably slightly tilted upward from the horizontal and permitted to distribute itself throughout the length of the mold by gravity as, for example, is described in the patent to Moore, 1,471,052 of October 16, 1923.

With regard to the application of the coating of finely divided dry coating material to the mold surface all that is necessary is that a jet of a dry carrier gas, charged with the finely divided dry particles of coating material should be so progressively directed against the portions of the mold to be coated as to progressively deposit upon contiguous areas of said surface a continuous coating of a finely divided dry coating material in suflicient amount to fill up and level oil" the depressed portions of the mold surface and produce a loosely adherent and loosely coherent smooth coating which will effectively prevent the metal being cast from entering the depressed portions of the mold surface and from impacting, in the casting and making adherent therewith the more elevated portions of the mold surface. Many forms of carrier gas jet and of appliances for effecting such relative movement between the jet and the mold as may be necessary to effect a continuous coating of the mold may be used and we do not wish to be understood as confining ourselves to the use of any particular form of jet or to any of the appliances for effecting such relative shifting of the jet with respect to the mold as will bring the jet consecutively into operative relationship with the contiguous portions of the mold surface to be coated.

It will be understood that,vwhere the cast pipe is to be withdrawn from the mold longitudinally,

that the pipe should be formed without any beading on its spigot end if the advantage of our invention with regard to the repeated use of the mold is to be secured, as the withdrawal in this manner of a pipe having a beaded end would necessarily destroy the mold, although, even with pipes of this kind, the advantage of our invention in securing a smooth surface on the casting with consequent increase of strength would be fully availed of.

Where pipesare 'cast in green sand molds or the like and where it is desirable that such molds should be re-used, it is advisable that the cast pipe should be withdrawn from the mold vertically to diminish, as far as possible, the friction between the cast pipe and the mold surface but where the mold is of a semi-permanent character, it is quite practicable and generally most convenient to withdraw the cast pipe horizon' tally as the semi-permanent mold is quite capable of resisting the friction of the pipe.

As an aid to the understanding of our improved method we have illustrated in the drawings forming part of this specification apparatus well adapted for the practice of our improved method and, referring now to these drawings,

Figure 1 is a sectional elevation taken through the center line of the pipe mold of a centrifugal pipe casting apparatus adapted for the practice of my improved method, with certain parts shown in non-sectional elevation.

Figure 2 is a cross section on the line 2--2 of Fig. 1.

Figure 3 is a cross section on the line 3-3 of Fig. 1.

Figure 4 is an elevation taken through the center line of a pipe mold of an apparatus designed to facilitate the coating of a sand lined mold preparatory to the insertion of the coated mold in a centrifugal pipe casting machine, cer-' tain parts of the mold supporting apparatus being shown in section.

Figure 5 is a fragmentary sectional view, taken on the line 5-5 of Fig. 4, illustrating an offsetting of the delivery nozzle with regard to the carrier gas conduit to which it is attached.

Figure 6 is a cross sectional view on the line 6-6 of Fig. 4.

Figure 7 is a cross sectional view on'the line 7--7 of Fig. 4, and I Figure- 8 is a diagrammatic and greatly enlarged sectional view .of the inner surface of a sand lined mold to which a coating of finely divided dry coatingmaterial has-been applied in accordance with our improved method.

Referring first to Figuresl to' 3 inclusive, A indicates a reciprocating carriage supported on suitable guide-ways or tracks indicated at A by means of wheels A. A A indicate pedestals supported on the carriage. These pedestals support parallel shafts B, B, to which are attached mold supporting rolls, one pair of which, indicated at B B are formed with V-shaped surfaces, indicated at b b and one pair of which, indicated at B B are formed with cylindrical surfaces, as indicated at b b. C, C, are yokes upon which are supported rollers, as indicated at C C These yokes are pivotally secured to one side of the carriage as indicated at C and" are detachably secured to the other side of the carriage, as indicated at C C D, D indicate gear wheels secured to one end of the carriage and driven by a motor D supported on the carriage. E indicates a cylinder and piston connected, as indicated at E to reciprocate the carriage A. F indicates a stationary support for a pouring ladle indicated at F and for a runner adapted to deliver molten metal to the moldand indicated at F. F indicates a cylinder and piston for tilting the ladle F. G indicates a conduit extending along and supported upon the runner F and terminating in a jet nozzle G adapted to deliver a jet of a carrier gas charged with particles of finely divided dry mold coating material outward against the surface of the pipe mold supported upon the mold A. The'conduit G is connectedwith what we may call a gun indicated at G, into which is delivered through a pipe nozzle indicated at G a jet of a carrier gas from a reservoir of gas under pressure not shown, G indicating a pressure gauge and G a valve. H indicates a feeding device adapted to feed finely divided dry mold coating material to a hopper H from which the mold coating material is fed into the gun G The structure of the feeding apparatus is not shown in detail but, as diagrammatically indicated. is similar to that described in the patent to Hunt and Arnold, 1,939,703, of December 19, 1933, and the jet nozzle G so far as indicated and as preferably constructed, is similar to that described in the application of Hunt and Arnold, Serial Number 640,257, filed October 29, 1932.

J indicates the shell or flask of a sand lined pipe mold, the sand lining being indicated at J The shell J as indicated consists of a metal cylinder having a bell shaped end indicated at J to the outer endof which is secured a flange ring indicated at J to which is bolted, as indicated at J a-driving ring J having gear teeth J to which is bolted a ring K extending over' the end of the mold J to a depth which will bring its inner edge flush with the inner edge of the pipe casting formed in the mold.

In Fig. 4, L is a laterally adjustable platform supported on guide-ways L and adjusted thereon by means of screws L L, which are gear connected as indicated at N, N, to a, shaft N which can be rotated as by means of a crank N. The platform supports pedestals L L, which, in turn, support shafts L L to which are secured mold supporting rollers, as indicated at L L and L, L. One of the shafts L is rotated through a chain belt L by a motor L. J v

is a metal pipe mold flask lined with sand as indicated at J and in other respects similar to the mold shown in connection with Figures 1 to 3. M is a carriage supported on a track M by means of the wheels indicated at M and, as

for finely divided shown, reciprocated on said track by a motor M chain drive connected as indicated at M to a shaft or axle to which the supporting wheels M are attached. 0, O, are pedestals supported on the carriage M and-supporting a tapering tubular support indicated at 0 which, in turn, supports the carrier gas tube indicated at G, to the end of which is attached a nozzle G The tube G is connected to the delivery end of a gun G which, together with a feeding device dry coating material indicated atH and the hopperH, are supported on the carriage M, the gun in this case-having its nozzle G connected by a hose G to a source of air under pressure, not shown.

In case the apparatus is to be used with molds of large diameter, it is advisable to connect the nozzle G to the conduit G by means of an offsetting connection g as indicated in Fig. 5.

In Fig. 8, a portion of the sand mold J is indicated and projecting portions of the sand are indicated at P with I, the depressed portions of the surface indicated at P while, we have indicated at Q the finely divided dry coating material filling up the depressions P and forming a smooth surface slightly above the projecting portions P.

In the operation of the casting machine as shown in Figs. 1 to 3, the mold shell J lined with sand as indicated at J is lowered into the casting machine having the gear J on its driving ring J engaged with the gearing D, D and its circular tracks J and J resting on the rollers B B and B B The carriage A which during the insertion of the mold J is at its greatest distance from the runner support F, is then moved toward the support and over the runner F until the spout at the end of the runner registers with the bell end of the mold. Carrier gas isthen admitted to the gun G as by opening the cock Giand finely divided'dry coating material is fed to the gun by the feeding device H, H

with the effect of delivering a jet of carriergas charged withdry finely divided mold coating material through the nozzle G against the surface of the mold J which previously has been set in rotation. Molten metal is fed to the runner F from the ladle F and as it is delivered to the mold through the spout of the runner the carriage A is progressively retracted with the result that there is delivered upon the surface of the sand mold a coating of finely divided dry coating material upon which, as it is progressively formed, molten metal is progressively delivered so that at the completion of the outward motion of the carriage A the cast pipe is formed in the coated mold. The rate at which the finely divided dry coating material is delivered to the carrier gas in the gun and by the Jet nozzle to the sand mold is such as to fill up the depressions P in Fig. 8 and, in effect, to submerge the projecting portions P and form a smooth and approximately level surface, as indicated at Q in Fig. 8, with the result that the casting as formed upon the smooth surface of the finely divided dry coating material forming a loosely coherent and loosely adherent inner surface of the sand mold and a casting is formed characterized by great surface smoothness and the absence of adherent portions of the sand mold and not only is the surface of the pipe" smoother than has heretofore been the case but,

by reason of the smooth outer surface, the pipe is materially stronger than is the case with similar pipes having a more or less roughened exterior surface.

Where the sand mold is of a semi-permanent character and the casting formed without a bead upon its spigot end, the cast pipe can be extracted from the mold while the mold is in the machine as by removing the core indicated at R and withdrawing the casting as is the common practice in machines of the general character indicated in which an externally cooled metallic mold forms a permanent part of the machine after which the mold may be reconnected and a new casting formed as above described and so on until the mold requires replacement but in cases in which a green sand mold or the like is used or in which a bead is formed on the spigot end of the mold, the mold should be withdrawn from the casting after each casting operation and where no bead is formed on the spigot end a casting may be withdrawn after the mold is removed from the machine under conditions which will have as little tendency as possible to injure the surface of the sand mold so that it may beagain coated and used.- a

Where a centrifugal casting machine of a different type from that illustrated in Figs. 1 to 3, is used, or when, for any'reason, it is advisable that the sand mold should be coated with a finely divided dry mold coating material before it is inserted in the casting machine, the coating may be applied to the sand mold in any convenient way, as, for example, is shown in Figs. 4 to '7. In this apparatus the circular shell or flask J with the sand coating J is placed on the supporting rolls L L and L L and set in rotation by the motor L and the chain belt L actuating the shaft L during the insertion of the mold in the machine. The carriage M is, of course, retracted .and, after the mold is in position and. in rotation, an air jet is supplied to the gun 6* through the nozzle G and finely divided dry coating material fed to the gun by the feeding apparatus indicated at H, H As a result, a jet of carrier gas charged with the dry finely divided coating material issues from the nozzle G and the carriage M is then progressively moved toward the rotating mold by the.

that a helical band 01' dry coating material with overlapping edges is deposited upon the surface of the sand mold progressively until the entire surface has its depressed portions filled up and a level surface formed by the coating material.

The lateral adjustment provided for the platform L by means of the threaded rods I.- and the mechanism for actuating them is tor the purpose of permitting an adjustment of the mold position with regard to the jet nozzle which will bring about the best results in the deposition of the coating and permit the use or the apparatus for the coatingoi molds of quite dif- Ierent internal diameters. After the mold has been properly coated, it is, of course, withdrawn from the coating apparatus and placed in position for the casting of a pipe where the casting is to be centrifugal in a centrifugal casting machine and where a bead cast pipe is to be formed in proper position and connection with such appliances as are used for bead castings.

It must be understood that the mechanisms which we have illustrated and, described are simply illustrative of mechanisms well adapted for use in the operation of our improved method which is, in no sense, limited to the use of any particular mechanical device for carrying it into eifect.

Having now described our invention, what we claim as new and desire to secure. by Letters Patent, is:

1. In the casting of metallic annuli in molds formed of compacted, non-conducting and reiractory materials, the method steps which con sist in depositing upon the inner surface of the so constructed mold a loosely adherent and loosely coherent coating 01' finely divided dry coating material by progressively directing against consecutive portions of the mold to be coated a jet of a dry carrier gas charged with dry finely divided particles of mold coating material, then pouring molten metal in contact with the dry depositing upon the inner surface of the mold a coating of loosely adherentand loosely coherent finely divided dry mold coating material by progressively directing against contiguous portions of the mold surface a jet of a dry carrier gas chargedwith finely divided dry particles of mold coating material, then pouring molten metal into the so coated-mold and centrifugally distributing said metal into the form of an annulus and, after the metal has set, withdrawing the annular casting from the lined mold flask in the direction parallel to the axis of the mold.

' NORMAN F. S. RUSSELL.

FREDERICK C. LANGENBERG.

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