US3293708A - Method of centrifugally casting flanged tubular members - Google Patents

Description

Dec. 27, 1966 F. w. FRUITMAN 3,293,708

METHOD OF CENTRIFUGALLY CASTING FLANGED TUBULAR MEMBERS Filed March 4, 1964 FIG-1 28 15 29 FIG-2 FIG-3 INVENTOR.

FRANK W. FRUITMAN ATTORNEYS United States Patent 3 293,708 METHOD OF CENTRIFUGALLY CASTING FLANGED TUBULAR MEMBERS Frank W. F ruitman, Arlington, Va., assignor to The Black Clawson Company, Hamilton, Ohio, a corporation of Ohio Filed Mar. 4, 1964, Ser. No. 349,798 14 Claims. (Cl. 22-2005) on the inner surface so that the finished casting has a compact grain structure free of voids or centerline cavities. Simultaneously with the production of these improved grain structures the chemical make-up of the molten metal may be changed, fior example, to eliminate or reduce impurities therein.

In addition, this invention has special relation to the method and apparatus disclosed in the copending United States application of Walter E. Rojecki, Serial No. 198,256, filed May 28, 1962, now abandoned, for Paper Machinery, and assigned to same assignce as the present application. In the practice of the invention of the above copending application, a tubular mold or core case is provided with sealed ends and one or more transverse baflles mounted therein with their outer peripheries spaced radially from the inner surface of the mold. The bafiles thus divide the interior of the mold into at least one flange chamber and a main chamber which are interconnected only by the passages formed between the baffle and the inner surface of the mold. While the mold is being rotated at high speed, a predetermined amount of molten metal is poured into the mold, and then the main chamber is connected to a source of gas pressure so that a portion of the molten metal is forced into the flange chamber through the passage. The rotation and pressurization of the mold are maintained until the metal solidifies, thus creating a tubular casting having "an integral internal flange for each flange chamber.

It is an important object of this invention to provide an improved and simplified apparatus and method for the production of centrifugally cast tubular members having internal flanges integrally formed thereon during the casting operation, and in particular to provide a method which achieves in a simplified manner the same end product as the method in the aforesaid copending application.

Another object of this invention is to provide apparatus for and a process of centrifugally casting a tubular member having internal flanges at either end thereof wherein the molten metal is caused to flow from a pressure chamber of the mold into one or more flange forming chamber's without the use of apparatus for pressurizing the entire mold, and further to provide such a process which is greatly simplified and thus produces a consistently high quality casting at a substantial saving in ultimate cost.

A further object of this invention is to provide a process for centrifugally casting a tubular member wherein the grain structure of the metal has substantially fewer voids or cavities between the solidified grains or dendrites, so that the resulting tubular member is substantially Patented Dec. 27, 1966 stronger, than similar products heretofore made by centrifugal casting processes.

A still further object of this invention-is'to provide a process for centrifugally casting a tubular member in such a manner that solidification commences at the outer surface of the tubular member and proceeds radially inwardly to the inner surface, rather than commencing from both the inner and outer surfaces of the tubular member as in present processes, so that center-line voids or cavities caused by shrinkage of the metal during solidification are eliminated from the central area of the tubular member.

Another object of this invention is to provide a process for centrifugally casting a tubular member which includes the use of a slag material for increasing the compaction of the grain structure as well as for chemically reacting with the molten metal to change or eliminate undesirable impurities or'chem'ical elements'therein, and particularly to provide such a process wherein the slag reacts with impurities in the molten cast iron, e.g., to reduce substantially the sulphur content of the molten cast iron.

A further object of this invention is to provide a process of the aforesaid type for producing a tubular casting having at least one integral internal flange by using a mold which is open at one or both ends for improved cooling of the casting, and particularly to provide such a process wherein a mass of a fluid material is utilized to create the head required for forcing the molten metal from the main chamber into the flange chamber.

Still further objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings:

FIG. 1 is a sectional view through casting apparatus in accordance with the invention for performing the method of the invention; 7

FIGS. 2 and 3 illustrate schematically the successive steps of the method of the invention in conjunction with the apparatus shown in FIG. 1; and

FIG. 4 is a schematically sectional view taken essentially along the line 44 of FIG. 3.

Referring to the drawing, wherein a preferred embodiment of the invention is illustrated, FIG. 1 shows casting apparatus including a tubular core case 10 supported on and rotated by the drive rollers 11 which engage the drive bands 13 extending circumferentially around the outer surface of the case 10. The core case 10 has end plates 15 and 16 secured to'each end thereof by bolts 17 which extend through a suitable aperture in the plates and into the tapped bores 18 in the case 10. Axially extending flanges 19 are provided on the outer periphery of the end plates 15 and 16 for overlying engagement with the ends of the core case 10 to resist the centrifugal forces acting on the case 10 when it is rotated at high speed.

Each of the end plates 15and 16 has an axially inwardly extending boss 20 with a relatively large opening 21 therethrough for connecting the interior of the case 10 to the atmosphere. The bosses 20 each have an expendable partition member or baffle 22 mounted on the innermost end thereof by the bolts 23. These partition members are formed of heat resistant material which is preferably frangible to facilitate breakage and removal from the interior of the finished casting, as will be explained. For example, each of the baflle's 22 may be cast of ceramic material such as baked foundry core sand, a baked mixture of silica sand and calcined gypsum, a baked mixture of silica sand and Portland cement or a baked mixture of .magnesite or other basic refractory material. In addition, these baflies can also be made of metal alloys, e.g., steel, depending on the temperature and the particular requirements ofa specific casting operation. If the presence of the baffles in the finished casting is not undesirable, the baffle may be constructed of a metal which will be fused to the cast material during the casting operation and thus form an integral part of the finished product.

The entire inner surface 24 of the core case 10, as well as the'inner end faces 25 of the end plates 15 and 16, are preferably covered with a liner 26 of suitable refractory material so that these components can withstand the heat encountered when the molten metal is poured into the core case 10. The liner 26 may be fabricated conventionally of molding sand for insertion within the core case, or it may be a coating which is applied to the various surfaces after the core case has been assembled. To aid in the dissipation of heat and moisture from the core case 10, it may be desirable to perforate the case in accordance with conventional practice.

The baffles 22 divide the interior of the core case 10 into a central pressure chamber 27, and a pair of flange chambers 28 and 29 which extend between the outer side surfaces 30 of baflles 22 and the inner surface of the liner 26 on surfaces 25 of the adjacent end plates and 16, respectively. The chambers 27, 28 and 29 are interconnected solely by the annular passages 31 between the entire outer periphery of each baflle 22 and the inner surface of the liner 26 so that the molten metal will flow from the central chamber 27 to the flange chambers 28 and 29. The flange chambers 28 and 29 are vented to the atmosphere by a plurality of passages 32 and 33, respectively, so that gases will not be trapped therein to obstruct the flow of metal thereinto. Also the passages 32 and 33 may be connected to a vacuum which increases the pressure differential between the flange and central chambers 27, 28 and 29 to facilitate flow of the molten metal 40 into the flange chambers 28 and 29.

An importantfeature of this inventionlies in the improved process for forming a tubular member having integral internal flanges at each end thereof. The process includes pouring a predetermined amount of molten metal 40 from the movable ladle device 36 into the central chamber 27 of the core case 10 while it is rotating at a predetermined speed, in a manner substantially identical to that described in the aforesaid copending application. Thus the molten metal is distributed over the entire inner surface 41 of the liner 26 in the case 10 under action of centrifugal force, and at this stage of the process the molten metal will have assumed a configuration similar to that represented in FIG. 2, wherein the grooves 42 are formed by the peripheral edges of the baffles 22.

After the pouring of the metal 40 is completed, a fluid or molten material 45 which has a specific gravity equal to or less than that of the molten metal and is substantially inert with respect to the molten metal is poured through the spout 46 into the pressure chamber 27. This material becomes evenly distributed, due to the centrifugal forces acting thereon, over the inner surface of the metal in the pressure chamber 27, and since it is equal to or lighter in weight than and non-reactive with the metal 40 there is no tendency of the material 45 to mix with the molten metal 40. On the other hand, when the material has a specific gravity slightly less than the metal 40, the centrifugal force acting on this molten metal and material tends to maintain segregation thereof.

The material 45 has a predetermined volume and height so that the force or heat acting thereon exerts a force on the molten metal 40 which forces a portion of the metal through the passages 31 into the flange chambers 28 and 29 to create the flanges 47. The amount of pressure or force which must be exerted by the molten material 45 during this step of the process is dependent on the size of the core case 10 and the various conditions present in each particular casting operation. That is, the size of the casting being made, the specific gravities of the metal 40 and material 45, as well as the height of the material, the speed of rotation of the core case 10 and the centrifugal force being exerted on the molten metal 45 are considerations which must be evaluated in determining the volume of the molten material. This force must be sufficient to force the molten metal through the annular passages 31 into the flange chambers 28 and 29 but less than that which will reduce the thickness of the metal in the pressure chamber 27 to less than the radial dimension of the passage 31 so that molten material 45 will not flow into the flange chambers 28 and 29. Thus if a material is used which has a specific gravity equal to that of the metal, the inner diameter of the tubular shaped mass of molten material would be equal to the inner diameter of the flanges, and if the specific gravity of the material used is decreased, the inner diameter of the material becomes less than the inner diameter of the flanges.

The fluid or molten material 45 used to create the force to cause metal to flow into the flange chamber can be a slag, salt, ceramic or metallic compound whose specific gravity in the molten state is equal to or less than that of the molten metal. The material must not be reactive with the molten metal, and preferably is frangible in the solid state to facilitate removal from the casting. Another preferred feature of the material 45 which facilitates removal thereof is a coeflicient of contraction on cooling which is less than that of the metal 40 so that the material separates cleanly from the metal casting during cooling. If the solidification temperature of the fluid material 45 is less than the metal 40, the fluid material 45 may be drained, syphoned or decanted away from the solidified casting 40 prior to solidifying thereof thus facilitating removal of the material 45.

By way of example, suitable materials 45 are the metalliC slags Fe O -SiO NaFeCl U O -SiO Pb203SiO2, and LiO-SiO These examples are intended for illustration purposes only, and numerous other compounds and mixtures can be used without departing from the scope of the invention. The specific gravity of these materials can be varied by changing the ratio of the metallic radical to the silicate radical, for example, in lead slag the volume lead oxide Pb O can be increased or decreased with respect to the silicate SiO to vary the specific gravity thereof. Also the specific gravity can be varied by changing the type of metal oxide in the slag, for example, uranium or lead slags, U O -SiO or Pb O -SiO can be used for higher specific gravities, whereas lithium slag, LiO-SiO can be used for a lower specific gravity. As an example, lead silicate slags which are non-reactive with bronze can be used for centrifugally casting bronze shapes. Application of a vacuum to the vents 32 and 33 will permit use of a wider range of lower specific gravity materials or smaller volume of these materials.

Furthermore, it is within the scope of this invention to use a solid or semi-solid material in lieu of the molten material 45. Thus a semi-fluid granulated material which has a density less than the specific gravity of the molten metal and is nonreactive therewith could be utilized to effect the flow of metal into the flange chambers. Consequently, the term fluid material 45 as used in this specification is intended to include such solid and semisolid materials which are capable of substantially carrying out the functional requirements set forth above.

After the material 45 is added, the rotation of the core case 10 is maintained until the metal 40 solidifies. To remove the finished casting, the end plates 15 and 16 are separated from the core case 10 and the finished casting so that the battles 22 remain in the tubular core case 10. The separation of the baffles 22 from the bosses 20 may be accomplished by removing the screws 23 or by disintegrating the baffles 22 in the areas around these screws. Next the casting is removed axially from the case 10, and the baflles 22 and material 45 may then be removed by disintegration or machining depending on the type of materials used.

While only a preferred embodiment of the apparatus has been shown and specifically described, it is within the scope of this invention to provide numerous other embodiments for carrying out the herein described inventive method for producing centrifugal castings having one or more internal flanges therein. It should be apparent that numerous expedients may be utilized by one skilled in the art to mount the baflles used to separate the flange and pressure chambers.

Similarly, the material used in constructing the bafiles 22 may vary widely depending upon the particular requirements of the specific casting operations to be carried out thereby. Materials other than metals 40 may be cast in accordance with this process so long as they are capable of changing from a liquid state to a solid state in response to a change in temperature or chemical action. Thus while the invention is particularly applicable to the casting of metals, and has been so described, other materials can be similarly cast without departing from the scope of the invention.

The illustrated embodiment of the mold produces an integral internal flange on each end of a tubular member, but it is within the scope of the invention to place these internal flanges at any point on the inner surface of the tubular member by merely appropriately positioning the baffles 22 in the molds. For example, if the baflles 22 Were placed in the central portion of the mold with a space therebetween' suitably vented to the atmosphere and the metal 40 and material 45 poured into suitable chambers on the outer sides of these baffles, an internal flange intermediate the ends of the tubular member could be formed. In a similar manner, the bafiles 22 can be used to form several flange chambers in the mold so that a plurality of flanges can be formed at various points on the inner surface of the tubular member.

The casting which is produced by the above described process has a hollow cylindrical body with one or more integral internal flanges therein (see FIG. 3). The metallurgical grain structure of the casting is substantially identical and indistinguishable throughout including the junc ture between the flanges 47 and the tubular portion thereof. The slag and other light impurities collect on or near the innermost surfaces of the casting, that is, on the inner peripheral surface of the flange and on the inner surface of the tubular portion where they can be easily removed by machining, if desired.

Since no welding operation is required, the casting is not subjected to high local temperatures which can cause distortion, and it is produced at a much lower cost since the flange does not have to be produced separately. It therefore follows that the inner surface of the tubular body does not require machining prior to welding to remove the slag and other impurities from the area to be welded, as would be required to weld a flange as a separate component to a centrifugally cast body. Also metals and other materials which are not suitable for welding can be formed easily into a tubular body having internal flanges therein by the present process. When a flange having a relatively thick axial dimension is desired, an appreciably stronger juncture with the body is attained by this process since a flange of this type could not be welded along the entire surface of contact with the body.

Thus a simplified process for forming a tubular member having one or more internal integral flanges and including all of the advantages of the aforesaid copending application has been provided. The casting apparatus need no longer be air tight, and as a result expensive and undesirable rotary connections need not be provided for the end plates. Since both ends of the core case are open, the material 45 and the metal 40 can be supplied through the same opening 21 or through opposite ends, as desired. This process produces a casting of consistently high quality since the mold need not be pressurized and the ends thereof are open thus facilitating cooling of the casting.

Another important feature of the invention is the improved grain structure which is produced and, as will be seen, this grain structure can be produced in centrifugally cast products which do not have internal flanges. The molten material 45 acts against the inner surface of the liquid metal and thus pressurizes this liquid metal to compress or squeeze the grains or dendrites, together, as these grains are transformed from a liquid to a semisolid or plastic state and then to a solid state. This action is similar to that which takes place in a forging action, and tends to eliminate the bridging effect of the grain structure growth so that cavities will not form during solidification of the metal.

Since the molten material is still liquid after the metal has solidified it acts as a continuous pressure medium during the entire period of solidification so that the compression forces are present at all times. The resulting product has fewer cavities or voids and is denser material with less sponginess than the normal centrifugal casting. It thus is stronger and is better suited for use in pressure vessels and is less likely to fail from fatigue. For example, this greater density will increase the thermal conductivity of the resulting product so that when it is used as a drier cylinder for a paper machine, it will be able to contain higher heating pressures, usually steam.

As is well known, in the conventional centrifugal casting processes the metal initially solidifies adjacent the outer surface and this solidification proceeds radially inwardly. Shortly thereafter, the solidification commences on the inner surface and proceeds radially outwardly. As the last portion of the liquid metal betweenthe inner and outer surfaces reaches the solid state, cavities are formed in this area in a random manner since there is no further liquid metal to fill the voids or cavities which occur as the metal shrinks due to solidification. These cavities are called centerline cavities and inherently Weaken the end product.

In addition to creating a pressure or force to compact the grain structure during solidification, the molten material acts as a heat sink to effect uniform cooling from the outer surface to the inner surface. That is, when a molten material which has a melting point lower than that of the metal being cast, the solidification proceeds from the outer surface of the metal radially inwardly to the inner surface thereof since the molten slag or material maintains the inner surface in a liquid state due to the heat present in the molten material. Since the molten material and metal have substantially different melting points, all of the metal will be solidified prior to the commencement of solidification of the slag. As indicated, it may be that this molten material will be removed prior to solidification.

By using a particular slag or other molten material having a chemical reactiveness for a particular element in the metal, it is possible to remove or change the chemical makeup of the finished casting. For example, when casting cast iron, the removal of sulphur is very desirable since it tends to make the resulting casting very brittle. The following example demonstrates the manner in which this sulphur is reduced:

Example Using a small mold, a tubular casting having an average diameter of 8 inches was made by pouring Percent Silicon 2.00 Sulphur 0.088

The slag consisted of barium fluoride and barium chloride in equal molecular amounts. Although this slag is neutral, barium has an aflinity for sulphur.

The resulting casting showed that the silicon content was 1.87%, and sulphur 0.031%. Thus 64% of the sulphur in the molten metal was removed as a result of this process. Silicon, phosphorous, or other impurities could be similarly removed by using slag materials which have an afiinity for the element which is to be removed. Furthermore, to insure that the slag absorbs the desired element, rather than the metal absorbing element from the slag, the slag must be higher on the electromotive force table than the metal.

Thus it is seen that by selecting proper materials for the slag, the actual composition of the molten metal can be changed as desired. The chemical action between the slag and molten metal is facilitated by the pressure between the slag and molten metal as created by the centrifugal force during rotation of the mold. These forces provide an autoclave or bath action which forces the interfaces of these molten bodies together under high pressures and temperatures to improve the efii-ciency and extent to which the chemical reactions take place. This autoclave action is well known in other and different processes and structures, but has never been utilized in the centrifugal casting or tubular members as disclosed herein.

As indicated above, the slag acts as a heat sink during the casting process, and an important advantage thereof is the uniform distribution of heat in the molten metal, as well as the uniform rate of cooling thereof. This creates a homogeneous grain structure throughout the casting reasonably free of cold or hot spots, and thus has a uniform thermal conductivity. As a result, a better quality paper machine drier roll can be produced thereby. This uniform cooling also prevents the formation of hard and soft spots in the finished casting thereby permitting machining of the casting with greater speed and high quality.

While the methods herein described, and the form of apparatus for carrying this method into effect, con,- stitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and form of apparatus, and that changes may be made in either without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A method of casting a tubular member having at least one internal flange, comprising the steps of pouring a predetermined quantity of molten metal into a tubular mold having the interior thereof separated by baffles into pressure and flange forming chambers interconnected only by an annular passage between the outer periphery of the bafiies and inner side walls of said mold, rotating said mold about its axis at a speed suflicient to cause said molten metal to assume a uniform thickness over the inner side walls of said mold, pouring a predetermined volume of fluid material having a specific gravity not greater than that of said metal in said pressure chamber to force a predetermined volume of said molten metal from said pressure chamber through said passage into said flange forming chamber, correlating said speed of rotation and the volume of said material so that the thickness of said metal on said inner surface is at least equal to the radial dimension of said passage, and maintaining said rotation until said metal solidifies so that said metal in said pressure chamber forms a tubular member having an integral internal flange thereon in each said flange forming chamber.

2. A method of casting :a tubular member having at least one internal flange, comprising the steps of pouring a predetermined quantity of molten metal into a tubular mold having the interior thereof separated by bafi les into pressure and flange forming chambers interconnected only by an annular passage between the outer periphery of the baflies and inner side walls of said mold, rotating said mold about its axis at a speed suflicient to cause said molten metal to assume a uniform thickness over the inner side walls of said mold, pouring a predetermined volume of fluid material having a specific gravity substantially equal to that of said metal and being non-reactive with said metal into said pressure chamber to force an equal volume of said molten metal from said pressure chamber through said passage into said flange forming chamber, correlating the volume of said fluid material with the radial dimension of said passage so that the thickness of said metal on said inner surface is at least equal to the radial dimension of said passage, and maintaining said rotation until said metal solidifies so that said metal in said pressure chamber forms a tubular member having an integral internal flange thereon in each said flange forming chamber.

3. A method of casting a tubular member having an internal flange, comprising the steps of placing a predetermined quantity of molten material into a tubular mold having the interior thereof separated by baffle means into pressure and flange forming chambers interconnected by an annular passage between the outer periphery of the baffle means and inner side walls of said mold, rotating said mold about the longitudinal axis at a speed sufficient to cause said molten material to assume a uniform thickness over the inner side walls of said mold, then placing a liquid having a specific gravity not greater than that of said metal in said pressure chamber to force a predetermined amount of said molten material from said pressure chamber through said passage into said flange forming chamber, correlating said speed of rotation and the volume of said material so that the thickness of said material on said inner surface is at least equal to the radial dimension of said passage, and maintaining said rotation until said material solidifies so that said material forms a tubular member having an integral internal flange in each said flange chamber.

4. A method of casting a tubular member having at least one internal flange, comprising the steps of placing a predetermined quantity of molten metal into a mold having an interior chamber separated into pressure and flange forming chambers connected only by an annular passage adjacent the inner surface of said mold, rotating said mold at a speed sufficient to cause said molten metal to assume a uniform thickness over the inner surface of said mold, then placing a fluid material having a specific gravity not greater than that of said metal and being nonreactive With said metal in said pressure chamber of said rotating mold to force a predetermined amount of said molten material from said pressure chamber through said passage into said flange forming chamber, correlating sai-d speed of rotation and the volume of said material so that the thickness of said metal on said inner surface is at least equal to the radial dimension of said passage, said material having a coeflicient of contraction during cooling which is greater than that of said metal to facilitate removal of said material from the tubular member.

5. A method of casting a tubular member having at least one internal flange, comprising the steps of pouring a predetermined quantity of molten metal into a tubular mold having a partition therein separating the interior thereof into a central chamber and a flange forming chamber connected only by an annular passage formed between the outer periphery of said partition and the inner surface of said mold, rotating said mold at a speed sufficient to cause said molten metal to assume a uniform thickness over the inner surface of said mold, then placing a molten material having a specific gravity less than that of said molten metal into said central chamber to force a predetermined amount of said molten material from said pressure chamber through said passage into said flange form: ing chamber, and maintaining said rotation until said metal solidifies so that the metal adjacent said inner surface forms a tubular member and the metal in said flange forming chamber forms an internal flange on the tubular member.

6. A method of casting a tubular member having at least one internal flange, comprising the steps of pouring a predetermined quantity of molten metal into a tubular mold having a partition therein separating the interior thereof into a pressure chamber and a flange forming chamber connected only by an annular passage formed between the outer periphery of said partition and the inner surface of said mold, rotating said mold at a speed sufficient to cause said molten metal to assume a uniform thickness over the inner surface of said mold, then placing a molten material having a specific gravity not greater than that of said molten metal into said pressure chamber to force a predetermined amount of said molten material from said pressure chamber through said passage into said flange forming chamber, correlating the speed of rotation with the weight of said material so that the thickness of said metal on said inner mold surface is at least equal to the spacing between said partition and said surface, and maintaining said rotation until said metal and said material solidify so that the metal adjacent said inner surface forms a tubular member and the metal in said flange forming chamber forms an internal flange on the tubular member, said material being of a type which is easily frangible when solidified for facilitating removal from the tubular member.

7. A method of casting a tubular member having at least one internal flange, comprising the steps of pouring a predetermined quantity of molten metal into a tubular mold having a partition therein separating the interior thereof into a pressure chamber and a flange forming chamber connected only by an annular passage formed between the outer periphery of said partition and the inner surface of said mold, rotating said mold at a speed sufficient to cause said molten metal to assume a uniform thickness over the inner surface of said mold, then placing a molten material having a specific gravity not greater than that of said molten metal into said pressure chamber to force a predetermined amount of said molten material from said pressure chamber through said passage into said flange forming chamber, and maintaining said rotation until said metal and said material solidify so that the metal adjacent said inner surface forms a tubular member and the metal in said flange forming chamber forms an internal flange on said tubular member, said material having a coeflicient of contraction during cooling which is greater than that of said metal to separate said material from the tubular member.

8. A method of casting a tubular member having improved grain structure comprising, the steps of pouring a predetermined quantity of molten metal into a tubular mold having a central chamber therein, rotating said mold at a speed suflicient to causesaid molten metal to assume a uniform thickness over the inner surface of said mold, then placing a molten material having a melting point lower and a specific gravity less than that of said molten metal into said central chamber to compact said molten metal during solidification, said material acting as a heat sink to cause solidification of said metal to proceed from the outer surface of said metal radially inwardly to the inner surface thereof to eliminate centerline cavities in the finished casting, said heat sink effecting substantially uniform distribution of heat in said metal and uniform cooling thereof to create a more homogeneous grain structure throughout the tubular member, and maintaining said rotation until said metal solidifies so that the metal forms a tubular member having an improved compacted grain structure.

9. A method of casting a tubular member having improved strength and a denser grain structure comprising, the steps of pouring a predetermined quantity of molten metal into a tubular mold having a central chamber therein, rotating said mold at a speed sufficient to cause said molten metal to assume a uniform thickness over the inner surface of said mold, then placing a molten slag having a melting point lower and a specific gravity less than that of said molten metal into said central chamber to compact said molten metal during solidification to force the same against the walls of said mold for greater precision in the outer dimensions of the tubular member so that less machining is required, said slag acting as a heat sink to cause solidification to proceed progressively from the outer surface of said metal radially inwardly to the inner surface thereof to compact said metal and form a denser finished casting, and maintaining said rotation until at least said metal solidifies so that said metal forms a tubular member.

10. A method of casting a tubular member comprising, the steps of pouring a predetermined quantity of molten metal into a tubular mold having a central chamber, rotating said mold at a speed sufficient to cause said molten metal to assume a uniform thickness over the inner surface of said mold, then placing a molten material having a specific gravity less than that of said molten metal into said central chamber, said material being chemically reactive with certain elements in said metal to change the chemical content thereof, said rotation of said mold creating a pressure between the interfaces of said material and molten metal for cooperation with the temperature of said molten metal to raise the efficiency of the reaction between said material and said metal, and maintaining said rotation until said metal solidifies so that the metal forms a tubular member having a composition different from the molten metal as poured into said chamber.

11. A method of casting a tubular member comprising, the steps of pouring a predetermined quantity of molten metal having impurities therein into a tubular mold having a central chamber, rotating said mold at a speed suflicient to cause said molten metal to assume a uniform thickness over the inner surface of said mold, then placing a molten material having a specific gravity less than that of said molten metal into said central chamber, said material being chemically reactive with said impurities and being higher in the electromotive series than said metal so said impurities combine with said slag, said rotation of said mold creating a pressure between the interfaces of said material and molten metal for cooperation with the temperature of said molten metal to raise the efliciency of the reaction between said material and metal, and maintaining said rotation until said metal solidifies so that the metal forms a tubular member having a composition different from the molten metal as poured into said chamber.

12. A method of casting a tubular member comprising, the steps of pouring a predetermined quantity of molten metal having impurities therein into a tubular mold having a central chamber, rotating said mold at a speed sufiicient to cause said molten metal to assume a uniform thickness over the inner surface of said mold, then placing a molten material having a specific gravity less than that of said molten metal into said central chamber, said rotation of said mold being suflicient to cause said material to assume a uniform thickness on the inner surface of said metal, said material being chemically reactive with said impurities and being higher in the electromotive series than said metal so said impurities combine with said slag, maintaining said rotation until said metal solidifies so that the metal forms a tubular member having a composition different from the molten metal as poured into said chamber, and removing said material with said impurities therein from said metal to thus produce a tubular member of increased quality.

13. A method of casting a tubular member comprising, the steps of pouring a predetermined quantity of molten cast iron having sulfur impurities therein into a tubular mold having a central chamber, rotating said mold at a speed suflicient to cause said molten metal to assume a uniform thickness over the inner surface of said mold, then placing a molten barium salt slag material having a specific gravity less than that of said molten metal into said central chamber, said rotation being sufiicient to cause said slag to form a uniform inner layer over the inner surface of said metal so that said sulfur combines with said slag in said inner layer thus removing at least a portion of said sulfur impurities from said molten metal, and maintaining said rotation until said metal solidifies so that the metal forms a tubular member of increased quality;

14. A method of casting a tubular member having at least one internal flange comprising, the steps of pouring a predetermined quantity of molten metal into a tubular mold having a partition therein separating the interior thereof into a central chamber and a flange forming chamber connected only by an annular passage formed between the outer periphery of said partition and the inner surface of said mold, rotating said mold at a speed suificien-t to cause said molten metal to assume a uniform thickness over the inner surface of said mold, then placing a molten material having a melting point lower and a specific gravity less than that of said molten metal into said central chamber to force a predetermined amount of said molten material from said pressure cham- 20 ber through said passage into said flange forming chamber and to act as a heat sink to eflect solidification of said metal in said central chamber to proceed progressively from the outer surface inwardly to the inner surface to eliminate centerline cavities therein, and main- 12 taining said rotation until said metal solidifies so that the metal adjacent said inner surface forms a tubular member of compact grain structure and the metal in said flange forming chamber forms an internal flange on the tubular member.

References Cited by the Examiner UNITED STATES PATENTS 743,077 11/ 1903 Hemptinne 2265 1,817,012 8/1931 Merle 2265 2,107,513 '2/ 193 8 Swoger 2265 2,248,693 7/1941 Barscherer 22212 2,853,755 9/1958 Beyer 222005 3,004,314 10/1961 Beyer 222005 3,077,013 2/1963 Dishman 22'200.5 3,181,210 4/1965 Montgomery 2265 3,201,829 8/1965 Cox et al. 2265 FOREIGN PATENTS 568,929 7/ 1958 Belgium.

725,601 3/ 1955 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examiner.

Claims (1)

1. A METHOD OF CASTING A TUBULAR MEMBER HAVING AT LEAST ONE INTERNAL FLANGE, COMPRISING THE STEPS OF POURING A PREDETERMINED QUANTITY OF MOLTEN METAL INTO A TUBULAR MOLD HAVING THE INTERIOR THEREOF SEPARATED BY BAFFLES INTO PRESSURE AND FLANGE FORMING CHAMBERS INTERCONNECTED ONLY BY AN ANNULAR PASSAGE BETWEEN THE OUTER PERIPHERY OF THE BAFFLES AND INNER SIDE WALLS OF SAID MOLD, ROTATING SAID MOLD ABOUT ITS AXIS AT A SPEED SUFFICIENT TO CAUSE SAID MOLTEN METAL TO ASSUME A UNIFORM THICKNESS OVER THE INNER SIDE WALLS OF THE SAID MOLD, POURING A PREDETERMINED VOLUME OF FLUID MATERIAL HAVING A SPECIFIC GRAVITY NOT GREATER THAN THAT OF SAID METAL IN SAID PRESSURE CHAMBER TO FORCE A PREDETERMINED VOLUME OF SAID MOLTEN METAL FROM SAID PRESSURE CHAMBER THROUGH SAID PASSAGE INTO SAID FLANGE FORMING CHAMBER, CORRELATING SAID SPEED OF ROTATION AND THE VOLUME OF SAID MATERIAL SO THAT THE THICKNESS OF SAID METAL ON SAID INNER SURFACE IS AT LEAST EQUAL TO THE RADIAL DIMENSION OF SAID PASSAGE, AND MAINTAINING SAID ROTATION UNTIL SAID METAL SOLIDIFICES SO THAT SAID METAL IN SAID PRESSURE CHAMBER FORMS A TUBULAR MEMBER HAVING AN INTEGRAL FLANGE THEREON IN EACH SAID FLANGE FORMING CHAMBER.

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