US2388974A - Method for casting metal - Google Patents

Description

Nov. 13,1945 R. K. HOPKINS METHOD FOR CASTING METAL Filed May 20, 1944 2 Sheets-Sheet 1 Nov. 13, 1945. R. K. HOPKINS 2,388,974

METHOD FOR CASTING METAL Filed May 2O, 1944 2 Sheets-Sheet 2 Rabenf w m n r In: @22 1 a 2 Patented Nov. 13, W45

METHOD FGR CASG METAL Robert K. HopkinsJNew York, N. Y., asslgnor to The M. W. Kellogg Company, New York, N. 3., a corporation of Delaware Application May 20, 1944, Serial No. 5365711 10 Claims.

The present invention relates to a method for casting articles.

One object of the present invention is to provide a new and improved casting method.

Another object is to provide a new and im- I proved method for casting a tubular article having a closed end.

A further object is to provide a new and improved method for casting a vessel or shell with a dished or convex h'ead.

In the electric fusion process of making ingots, current is discharged across a flux submerged gap to create a metal fusing zone in and around said gap. At the same time, solid metal ingredients are fed into the fusing zone according to the desired analysis of the metal to be produced.

Another object of the present invention is to provide a new and improved method .for casting articles according to the electric fusion process above described.

In accordance with certain aspects of the present invention, an outer mold is provided conforming to the outer shape of the shell or vessel to be cast, and having a bottom end wall. Metal isfirst produced and cast in the bottcm of the outer mold by the electric fusion process above described. As the casting metal is produced and deposited inthe outer mold, the inner mold oi the shell to be cast is built up progressively from the center radially outwardly and upwardly by the use of mold sections or blocks. At the same time, the mold assembly is desirably rotated about a substantially vertical axis to equalize the dis-- tribution of the metal deposited in the mold space. In this manner, solidification of the metal deposited in the mold space and the composition of said metal can be effectively controlled to form a sound headed shell casting having the fished physical and metallurgical character- Various other objects, features and advantages of the invention will be apparent from the following particular description, and from an inspection of the accompanying drawings, in which:

Fig. l is a vertical diagrammatic section of a mold set-up for carrying out the initial stages of the castingmethod of the present invention;

Fig. 2 is a section of the mold set-up taken on line 2-2 of Fig. 1, but on a reduced scale; and

Figs. 3, 4 and 5 are vertical diagrammatic sections of the mold set-up similar to that of Fig. 1, but showing later successive stages respectively of the casting method of the present invention.

The invention is shown in the drawings applied to a method of making a tubular member with an end wall, and more specifically to a method of casting a vessel with a domed or bowl-shaped end wall orhead, such as a pressure vessel or autoclave. However, it must be understood, that as far as certain aspects of the invention are concerned, this invention is applicable to the casting of articles of various shapes, especially sym-' metrical ones, and maybe employed, as for example, in the manufacture of gun tubes, solid or hollow shafts and flanged articles such as manways.

Referring to the drawings, there is provided an outer mold it, which conforms with the outer sh'ape of the vessel to be cast, and which is shown with a bowl-shaped floor ll defining the outer contour of the convex head or end wall of the vessel. This mold it is shown symmetrical with respect to the vertical axis and circular in internal cross-section. The contour of the mold floor ii is sh'own substantially as a, segment of a,

sph'ere, but as far as certain aspects of the invention are concerned, this contour may be of any desired configuration.

To permit repeated use of the mold l0, this mold is made of metal having high heat conductivity such as copper, and is hollowed to allow a suitable, cooling medium such as water to be circulated th'erethrough. The mold Hi is advantageously sectionalized, and for that purpose is shown comprising a floor section 82 and separate wall sections 53 stacked on the sides of the floor section, and coniointly defining with the floor section a mold unit having the necessary internal casting form. Although the mold sections l2 and it are not shown with inlet and outlet connections for the circulating cooling liquid, it must be understood that these are provided and connected into the hollows of said sections in any suitable manner.

During the initial stages of the casting operation, the bottom center section ifiof theinner mold i5 defining the innercurved periphery of the vessel to be cast is disposed in casting position in the lower central part of the outer mold Ill, and is spaced from the bottom of said outer mold .by a distance corresponding to the thickness of the vessel head to be cast. This inner mold section it may be supported in casting position in the interior oi the outer mold ill in anysuitable manner, as for example bya series of wires or cables i1, and is shown provided with an outer casting surface is extending substantially parallel to or concentric with the mold floor ll. However, in

- cate, aluminum silicate or glass.

accordance with certain aspects of the present invention, this outer casting surface may directionally vary with respect to the surface of the mold floor H, to produce a head or end wall of varying thickness on the vessel to be cast. i

The inner mold section I6 is desirably made of a construction which will permit its repeated use. For that purpose thi inner mold section It is made of metal having high heat conductivity such as copper, and is hollowed to permit circulation of a cooling medium such as water therethrough; Inlet and outlet connections 22 and 23 on this inner mold section [8 are connected to inlet and outlet manifolds 24 and 25 respectively, desirably through flexible hose connections.

Although the inner mold section It is shown as made of one annular piece, thi mold section may be made into segments which are bolted or otherwise fastened together to form a single annular unit. Such fastening means should not be disposed in any position which will destroy the continuity-of the lower mold surface N or the outer peripheral surface of the mold section It.

For producing and depositing casting metal of the desired analysis in the interior of the outer mold Ill, the inner mold section [6 is provided with a central aperture 2'! in'which centrally extends a consumable electrode 28. Electrode 28 has its lower end submerged in-a layer of flux 30, and is spaced at this end from the molten deposited metal 3! by a flux submerged gap 32 through which electric current is discharged to create a metal fusing zone in and around said gap. To produce the necessary current discharge across the gap 32, the electrode 28 and the mold deposited casting metal 3! are connected in the same circuit. The necessary electrical connection to the deposited casting metal M can be effected through the metal walls of the outer mold III, as for example, through a stationary brush contact 33.

The electrode 28 contains at least some of the ingredients of the casting metal to be produced. Other ingredients may be fed in granular, pellet or pulverulent form into the metal fusing zone created'in and around gap 32. For feeding the, fluent metal ingredients into the metal fusing zone, electrode 28 may be tubular, and the into maintain the current discharge gap 32 substantially constant in length. The upward movement of the electrode 28 may be efiected by,

mounting said electrode with its feeding means on a suitable carriage 38 movable vertically, as for example, through cables or feed screws (not shown).

While metal is being produced and deposited in thecenter of the inner mold l0 through the electrode 28, any number of other electrode 3! may be employed (four being shown) on the outside of said inner mold section according to the size of the vessel to be produced. These outer electrodes 31 may have their lower ends submerged in the flux 30, and operate in conjunction with fluent metal ingredients as does the center electrode 28, to produce and deposit metal on the outside of the inner mold section 8.

As the metal is being produced and deposited in the outer mold In in the manner indicated, mold l0 and the inner mold section l6 are slowly rotated in unison with respect to the electrodes 31 in order to effect even distribution of the deposited metal in said outer mold. The mold assembly may be rotated in any suitable manner.

For example, it may be supported on a platform 40 which is secured to a verticalshaft 4i driven through a worm and worm wheel drive (not 40 form a continuation of the center inner mold gredients may be fed into the fusion zone through the hollow of the electrode. Electrode 28 may be continuously formed from a skelp as it is bein consumed.

As the electrode metal is consumed, the electrode 28 is fed downwardly by any suitable means, indicated diagrammatically by the feed rolls 34, to maintain the gap 32 substantially constant in length.

The flux layer 30 floats out impurities in the metal and conserves the heat in said metal. This flux layer 30 may be of any suitable composition well-known in the metallurgical art, and may, for example, comprise silicates or components of silicates, such as magnesium silicate, calcium sili- Since the metal producing operation is initiated with the electrode 28 close to the bottomof the outer mold I0 during the first stages of operation, and since the metal 31 produced and deposited in the-outer mold gradually rises during the operation, it is necessary to move the electrode upwardly to keep it spaced from the rising. level of metal 3|. The downward feeding of the electrode28as it isconsumed, and the upward movement of said electrode to compensate for rise in the level of the 'depositedmetal 3| are correlated section l6, and is connected to the manifolds 24 and 25 of the water circulatin system through appropriate hose connections. While the second mold section 45 is being set in casting position, the metal producing operation of the electrodes 31 may be temporarily discontinued, but it is desirable to have their operation continue during this mold assembly phase as long as they are positioned away from t e first inner mold section l6 by a distance sufllciently great to permit the second inner mold section 45 to be lowered easily into proper casting position without interference from said electrodes 31.

The inner mold section 45 is annular in shape, and fits snugly around the center mold section IS. The outer peripheral surface of the center mold section i8 is desirably inclined or conical, and the inner periphery of the second outer mold section 45-is of corresponding conical configuration to mate snugly with said outer peripheral mold surface. The second inner mold section 45 will thereby seat snugly over and around the first inner mold section It, andwill be retained in fixed casting position shown in Fi 3 by the inclined or conical interengaging surfaces of said mold sections, so that no additional support for the second mold section is necessary.

With the second mold section 45 supported in casting position shown in Fi 3, the outer elecstantially constant in length.

assae'ra outwardly to an approximate position B close to and on the outer side of the prospective position of the third inner mold section as to be later' added to the inner mold assembly. While the electrodes 37 are moved radially outwardly, they are also moved upwardly to keep apace with. the rising level of the deposited metal at, so that the current discharge flux submerged gaps below said electrodes respectively are maintained sub- When the depmited metal 35 reaches the lower outer annular corner of the second inner mold section 65, the third inner annular mold section 48 of hollow copper construction is added to the inner mold assembly as shown in Fig. 4, and in a manner similar to that described in connection with the addition of the second mold section t5, and said mold section 68 is connected to the manifolds 2d and of the water circulating system through appropriate hose connections. During this mold assembly stage, the metal producing operations of the electrodes 3; maybe temporarily discontinued, but these operations are de-' sirably continued as long as enoughspace is available to set the third inner mold section d8 into proper casting position without interferin with said operations.

- During the stages of the process when the cylindrical portion of the vessel til is being cast, the inner mold sections 52 for this portion are also cylindrical in shape, and are stacked one on top of the other. During this stage of the casting operation, the electrodes 31 are moved merely vertically in the mold space substantially midway between the sides thereof.

It should be noted that during the process of casting the shell 5! as described, a layer of highly superheated metal is continuously maintained in the upper section of the deposited metal. The

highly superheated metal serves to feed the shrinking solidifying metal beneath it and thereby serves to continuously hot-top the metal as it is progressively cast. In this manner, a shell cast- I ing is produced which is sound and substantially By the time the third inner mold section $8 is ready .to be set into casting position, the portion of the deposited metal 3! underneath the first inner mold section It may be solidified, so that the cable supports H for said mold section may be dispensed with.

. After the third inner mold section d8 has been set into proper casting position, the metal producing operations of the electrodes 37 are continued or resumed, and said electrodes are moved upwardly and radially from the position B to the approximate position C shown in Fig. 4 in a manner and for the purpose similar to that already described in connection with the movement of these electrodes from position A to B shown in Fig. 3.

The two component movements of each electrode bl radially and upwardly from position A to B shown in Fig. 3 may be made simultaneously, so that by the time the deposited metal ill reaches the lower outer annular corner oi the second inner mold section 45, these electrodes will be in position B; However, as far ascertain aspects of the invention are concerned, the electrodes 31 may be moved only vertically from the position A, while the first and second-inner mold section It and d5 alone are set in casting position, and then after the deposited metal M has reached the lower outer annular corner of the second inner mold section 55, the elevated electrodes may be moved in one step radially outwardly to position B in preparation for the assembly attachment of the third innermoldsection d8. Similarly, the electrodes 31 may be moved from position B to position C in two distinct steps during the phase of operation shown in Fig. 4.

If the movement of the electrodes 37 is eflected simultaneously upwardly and radially outwardly, said electrodes are always maintained substantially midway oi the horizontal width of the mold space between the outer and inner molds Ill and I5. If the electrodes 31 are moved step by step as described, the electrode positions A, B, C, etc. will be substantially midway of the horizontal width of the mold space.

After the deposited metal 3! reaches the lower annular corner of the third inner mold section 48,

homogeneous throughout its entire length.

As many changes can be made in the above method and apparatus, and many apparently widely difi'erent embodiments of this invention can be made without departing from'the scope of the claims, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A process of casting a vessel with an end wall, which comprises the steps of depositing molten metal in an outer mold having side and bottom walls, and progressively assembling an inner core in and correlatively to said outer mold from the center of said outer mold radially outwardly and upwardly as the level of the deposited metal rises, to form between the mold and the core a mold space defining the walls of the vessel to be cast, and to extend progressively said mold space radially ahead and above the rising level of the deposited metal.

2. A process of casting a vessel with a convex end wall, which comprises depositing molten metal in an outer mold having a cup-shaped mold cavitywith a dished floor, and assembling an inner core in said outer-mold step by step from the center of said outer mold radially outwardly and upwardly as the level of the deposited metal rises, to form with said outer mold a cup-shaped mold space dished at one end, and to extend progressively said mold space radially ahead and above the rising level of the deposited metal.

3. A process of casting a vessel with a convex end wall, which comprises mbling an inner core radially outwardly'and upwardly in an outer mold having a cup-shaped cavity with a dished floor, to form with said outer mold a mold space conforming with the shape 01' the end wall of the vessel to be cast, and to extend progressively said mold space radially outwardly and upwardly, and depositing molten metal in said mold space through its outer extended section after each inner mold assembling step.

4. A process of casting, comprising producing and depositing molten metal in an outer cupshaped mold by the current discharge action of one or more flux submerged electrodes, and progressively assembling an inner core in said outer mold correlatlvely with respectto said outer mold as the level of deposited metal increases, to extend the mold space defined between said molds progressively ahead oi the deposited metal.

5.-A process of making a vessel with a convex end wall, which comprises assembling an inner core radially outwardly and upwardly in an outer mold having a cup-shaped cavity with a dished floor, to form with said outer mold a mold space conforming with the shape 0! the end wall or the vessel to be cast, and to extend progressively said mold space radially outwardly and upwardly, and producing and depositing molten metal in said mold space alter each inner core assembling step by the current discharge action or one or'more flux submerged consumable electrodes extending in the outer extended peripheral section '0! said mold space.

8. A process oi casting a hollow article, comprising depositing metal in amold, assembling a core progressively and correlativeiy with respect to said mold as the amount oi deposited molten metal increases, to extend progressively the mold space defined betweed said mold and said core aheadoi the deposited metal, and rotating said mold and said core in unison as metal is being deposited in said space to sheet substantially? equal distribution oi the deposited metal in said mold sp ce.

'1. A process or casting, comprising depositing molten metal in an outer cup-shaped mold, and progressively assemblins an inner core in said outer mold correlatively with respect to said outer mold as the level of deposited metal increases, by adding annular core sections into snug peripheral embracing engagement with previously assembled inner annular core sections, whereby the mold space defined between said mold and core sections extends progressively ahead of the deposited metal.

in said outer mold by adding annular core sections into snug peripheral embracing engagement with previously assembled inner annular core sections, whereby the mold space defined between said mold and core sections extends progressively ahead of the deposited metal, said core sections having curved surfaces opposite said outer mold tioor blending into one substantially continuous surface which extends substantially parallel to said outer mold floor.

9. A process 01' making a vessel with a convex end wall, which comprises depositing molten metal in a mold space between an outer mold and a partially completed inner core containing a peripheral annular section, adding an annular core section snugly around said last-mentioned annular core section when the molten metal in said space reaches a substantially predetermined level in said space. to extend progressively the mold space radially outwardly, and repeating said inner core assembling operation each time the level or the molten metal reaches a substantially predetermined level with respect to the last-assembled inner core section.

10. A process of making a vessel with a convex end wall, which comprises producing and depositing molten metal by the current discharge action of one or more tiux submerged electrodes in a aaprocessofcastingavesselwlthaconvcx' end wall, which comprises depositing molten metal in an outer cup-shaped mold with a dished curved door. and as the level or deposited metal increases, progressively assembling an inner core mold space between an outer mold and a partially completed inner liquid-cooled core containing a peripheral annular section, adding an annular liquid-cooled core section snugly around said lastmentioned annular core section when the molten metal in said space reaches a substantially predetermined level in said space to extend progressively the mold space radially outwardly, repeatins said inner core assembling operation each time the level of the molten metal reaches a substantially predetermined level with respect to the last-assembled inner core section, and rotating said inner core and outer mold while the metal is being produced and deposited in said mold space deposited metal in'sald space.

to elect substantially uniform distribution r the i ROBERT K. HOPKB lS.

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