US1972945A

US1972945A - Apparatus for and process of casting metals

Info

Publication number: US1972945A
Application number: US492253A
Authority: US
Inventors: Lars G Nilson
Original assignee: Individual
Current assignee: Individual
Priority date: 1930-10-30
Filing date: 1930-10-30
Publication date: 1934-09-11
Anticipated expiration: 1951-09-11

Description

sept. 11, 1934. L. G. NILSON 1,972,945

APPARATUS FOR AND PROCESS OF CASTING METALS Filed Oct. 30. 1950 5 Sheets-Sheet l Sept. 11, 1934. 1 G. NlLsoN APPARATUS FOR AND PROCESS OF CASTING METALS 1950 3 Sheets-Sheet 2 Filed Oct. 30.

Fig

INVENTOR Sept. 11, 1934. L. G. NlLsoN APPARATUS FOR AND PROCESS OF CASTING METALS Filed 0G13. 50 1930 5 SheecS-Sheetl 3 INVENTOR Fig. 14.

Patented sept. 1,1, 1934 UNITED STATES PATENT OFFICE APPARATUS FOR AND PROCESS F CASTING METALS 8 Claims.

This invention relates to improved methods and means for producing metal castings and more especially castings made through the use of permanent or semi-permanent molds. The process and appliances therefor are particularly well suited to the production of castings of metals having high temperature melting points, as iron, steel, nickel, copper, bronze, etc.

My invention contemplates the provision of l0 means for overcoming many of the difficulties which prevail today-in the art of casting metal. It may be pointed out that under the customary methods of producing castings, the temperature of the pouring metal must be high in order that it may run freely and reach the most remote corners of the mold. Inasmuch as early solidica-` tion takes place in the restricted sections of the mold, shrinkage defects usually occur. With high temperature pouring conditions moreover the cooling is necessarily slow, particularly with sand molds, and results in coarse grain. This invention discloses a method and apparatus wherein it is feasible to form castings under conditions where the metal is at a relatively very low temperature, above the plastic or semi-fluid state,

practically eliminating shrinkage defects.

An important aim of the invention is the making of castings having smooth surfaces, which are free from scale and true to form, irrespective of their size. Anadded object is to effect negrained structure, as compared with castings produced by the more usual-methods, together with freedom from blow-holes, inclusions and other defects. A still further object is to bring about economy in manufacture and greater uniformity in product.

In the carrying out of my invention, I employ a mold or die having separable portions which may be constructed .of metal alone, or a combination 40 of metal and refractory materials. The mold when joined, i. e., when closed on itself, is plunged into a properly prepared molten metal bath to a depth below its dross surface portion, after which it is opened to allow entry of the molten material. The mold is then quickly closed, lifted with its contents out of the bath, opened after the necessary time has elapsed to permit the metal to freeze and the casting ejected.

While in its broad aspects a like procedure employing metal molds was used many years ago for casting soft metals, I have devised and incorporated therein certain features designed to effect greater speed in casting, higher precision and uniformity and economy in manufacture in order to render the method more suited to present-day high-temperature requirements and needs. To characterize the improved process I have termed it dip-casting. l

Briefly described, the method of making `ldipcastings according to my improved process in- 60, cludes means for shielding the exterior surfaces of the mold for their protection against early deterioration, the freezing yof metal thereto and also to avoid undue loss of heat from the bath as the result of excessive chill from the mold. It includes combinations of permanent and porous cores to allow the casting of intricate shapes and also means for accelerating, retarding or otherwise controlling the cooling of one portion of the mold or casting'relative to another, thereby facilitating perfection of castings as to form and quality. These and other equally important features of novelty, such as means for controlling the temperature of the casting metal Within a desired low range for the prevention of undue shrinkage in cooling, are pointed out With particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention and the advantages possessed by it, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described various embodiments` of nrv invention.

In the drawings: v 'Y Fig. 1 is a view in sectional elevation of one form of divided mold construction with co-operating elements, which I may employ.

Fig. 2 is a view in sectional elevation of a divided mold construction suited to the casting of ring blanks.

Fig. 3 is a. view in sectional elevation ofa divided mold construction embodying a waterjacketed metal core.-

Fig. .4 is a 4view in sectional elevation of a divided mold employed in combination with a sand core.

' Figs. 5 and 6 are views in plan andsectional elevation respectively of a water-jacketed divided mold designed for the casting of ingots.

Fig. 7 is a view in sectional elevation of a waterjacketed divided mold designed for the simulta neous production of two billets.

Fig. 8 is a. view in sectional elevation of a waterjacketed divided mold designed for the simultaneous production of four billets or ingots.

Figs. 9, 10 and llvare views inplan, sectional side, and sectional front elevation, respectively, of a dipping tank."

Figs. 12 and 13 are views in plan and elevation respectively, of a tilting table designed to pro- 110 vautomatic operation.

mote-circulation of molten metal in the dipping Figs. 14 and 15 are views in plan and elevation respectively of a construction suited to the production of castings under automatic or semi- Fig. 16 is a view in side sectional elevation showing the position ef lthe refractory on the divided mold and Fig. 17 is a front view of the same.

Figs. 18 and 19` are views in side sectional and.

front elevation, respectively, of refractory tiles or blocks show-method kof attaching same. to the mold. l

Fig. is a plan view and Fig. 21 isa view in sectional elev'ation of an electric arc heating device y which may be employed in combination with the dipping tank of Figs. 9, 10 and 11 for the purpose of raising the temperature of the metal '-therein.

Figs. 22' and 23 are views illustrating the location of shrinkage cavities under different methods of casting.

Referring to Figfl, the Asepar'alcale- *parts 1, 2

of Aa. metal mold or die, which t closely togethery far as possible the mold itself which is sub- 'merged in a molten metal bath 9 contained in a crucible 10, as shown in section.

Preliminary to the use of the apparatus of Fig.k 1, the moldl should be preheated, beforeinserting in the bath, tosa degree sufcient to insure its freedom from-moisture. It -will however be understood that the mold will always be at an elevated temperature after the production of cast' ings is under way. In the process of forming the castings the closed mold is inserted in the metal v9 in such manner that the recessed portion 4 will be well belowl that surface region of the bath 9 where 'dross may be expected to be present. Then the `mold is opened by means' of the

tongs

5, 6 whereupon the molten metal has free access t its relatively cool inner surfaces and parting faces. A slight amount of metal will immediately freeze thereon to form a thin coating of solid metal, whereupon the mold is again closed to retain an amount of liquid metal sufiicient to entirely ll the recess 4. y As the next step, the mold is withdrawn fromthe-bath, leakage of metal therefrom .being eifectually prevented by the thin chilled coating "of solid metal at' the parting-faces 3 welding together. After a proper interval -of time has elapsed so as to permit freezing of the metal in the cavity 4, the mold is opened and the casting ejected.

In Fig. 2 I show in sectional elevation a mold of somewhat more complex form, which is designed for the casting of ring blanks. Referring to Fig. 2, an annular metal mold portion 11 mounted upon a metal carrying arm 12 having lugs 13,

\ 14 which are secured to such mold portion 11 at points 180 apart, coacts with an annular metal mold portion 15 mounted upon a metal supporting arm 16 which has lugs 17, 18.v which are secured to the portion 15 at points likewise 180 apart.

` The two

mold portions

11 and 15 arey so positioned relative to each other that when they are in contact there is an annular region 19 formed which is designed for receiving molten metal in the y the cooling fluid so as to cause it to shrink away process of casting. Surrounding the mold portions lland 15 respectively and aportion of the carrying arms 12 and 16 therefor, are refractory coatings 20, 21. whichpcoact at parting faces designated as 22, 23. The supporting arms 12 and 16 are connected with an operating mechanism, not shown, by means of which the

mold portions

11 and 15 are brought together or separated.

'I'he process of forming a casting through the use ofthe constructioni shown in Fig. 2 is entirely similar to that described in connection with the construction of Fig. l.

In Fig. 3 I show in sectional elevation a divided permanent moldarrangement, which is designed for casting a cylinder having one closed and one open end, in combination with a metal core which is water-jacketed to control temperature. Referring to Fig. 3, a tubular'metal cylinder 24 which is closed at one endend has a vent eccentrically disposedfat the other, surrounds a-concentrically disposed pipe 26. passing through its end and connecting to a source of water supply not shown. 'The cylinder `24 and. pipe 26 unite to form' a vwater-jacketed core. The divided

mold portions

27, 28 are attached-to

operating arms

29, 30.

Mold portions

27, 28,

Aoperating arms

29, 3 0, and thatJ portion of the core 24 which is exterior to the mold are lagged with refractory material 33.- The space between the cylinder 24 and the divided

metal portions

27 and 2,8 receives the 105 casting metal. 'I'he parting faces of the mold are indicated at 34.

The cylinder 24 and pipe 26 are supported by outside means, not shown, the lattery being connected at its upper end to a source of fluid supply in such manner vthat the fluid passes through pipe 26 into cylinder 24 at its lower end, thence up and abcutpthe annular space between such cylinder 24 andthe outside walls of the pipe 26 as indicated bythe arrows to emerge through the vent 25, which is connected to a drain system not shown. The supporting means for the cylinder 24 andthepipe 26 are-in fixed relation to the mold operating means so that such cylinder shall properly seat when the mold is closed. i

The operation of the appliance of Fig. 3 is similar to that of the appliances of Figs. 1 and 2, except that when the mold is closed after receiving its metal the cylinder 24 is iiushed inwardly by from the casting for the purpose of facilitating the ejection ofthe latter.`

Under some conditions it is desirable to use cores of sand or the like and inFig. 4 I show in sectional elevation a divided mold arrangement which employs a core in combination with a suction device, the latter for the dual purpose of holding the cor'e in place during the forming of the castings and to draw off gases formed when the casting metal strikes such core, Referring to Fig. 4,

mold portions

35, 36, secured to operating

arms

29, 30, have,interiorly a sand core 37 which is socketed at its lupper end into a metallic tubular head 38 supported by outside means not shown, the mold and core coacting to provide a space 29 designed for the casting of a conventional type automobile piston. The bore 40 of the tubular head 38 is connected to a vacuum pump system, not shown, in such manner that the core 37 is` held in place by suction. Operating

arms

29, 30, 145 the exterior surfaces of the

mold portions

35, 36 and the tubular core Ihead 38, are lagged with refractory material 33. The parting faces are indicated at 41. s

The operation of forming castings by means of 1'50 the mold of Fig. 4 is similar to those previously described, the supporting means for the tubular head 38 having a fixed relation to the mold operating means so that the core 37 shall b`e in proper position when the mold is closed.

In Figs. 5 and 6 I show in plan and sectional elevation respectively a water-jacketed divided mold designed for the casting of ingots. Referring to Figs. 5 and 6, in which Fig. 6 represents a section along the line A-B of Fig. 5, extended hollow divided

mold portions

42, 43 are fastened to, at their respective end regions, and supported by, tubular operating

arms

46, 47, 48 and 49 which serve also for the ingress and outlet of a cooling fluid which passes through the

interiors

44 and 45 of the

respective mold portions

42 and 43. For example, mold portion 42 has fluid ingress and outlet through

arms

46 and 48 respectively, while mold portion 43 has corresponding fluid ingress and outlet through arms 47 /and 49 respectively. Lagging 33 of refractory material is applied to cover the whole exterior portion of the mold and those portions f the tubular arms whichwould contact with the molten metal in the process of forming a casting.

It will be noted, in connection with the construction disclosed in Fig. 6, that the refractory material is so disposed that when the mold is closed the refractory in effect forms a part of the mold itself and determines the thickness of the casting, 51 designating here the parting faces. Conical holes 50 along the vertical parting lines serve to facilitate escape of surplus metal as the mold is closed.

It is practicable by the method of my invention to produce more than one casting in a single operation and in Fig. 7 I show a view in sectional elevation of one end of a divided mold designed for casting billets or slabs consisting of

hollow mold portions

52, 53 fastened to and supported by operating

arms

29, 30. It will be understood that additional similar pairs of operating arms are required where the cast object is of considerable length, as in the case of slabs, etc. 56 is a partition, preferably of metal and coated with a refractory material 56a, which is secured to and supported by a member 57 in such manner that it will be central to the mold when the latter is closed. The partition 56 runs longitudinally to provide similar

interior regions

58, 59 for the reception of molten metal. A tubular connection 54 giving access to the hollow interior of the mold portion 52 provides for the ingress of a cooling uid while a similar tubular connection, not shown, providesfor the egress of such fluid. In like manner the tubular connection 55 provides for the ingress of cooling fluid to the hollow interior of mold portion 53 while a similar tubular connection, not shown, provides for the egress of such fluid. v33 is the refractory. It will be clear that the operation of forming castings through the use of the construction of Fig. 7 differs in principle in no Way from those previously described.

The construction shown in Fig. 7 combining the jacketed system, for rapid cooling, offers a peculiar advantage in that due to the cooling taking place more rapidly at one region of the cast body than another quite some control over the loof the mold portion 60 provides for ingress, while a similar tubular connection at the other end provides for egress. Similarly, the tubular connection 63 provides for ingress of the cooling fluid at one end of the hollow interior of the mold portion 61, while a similar tubular connection, not shown, provides for egress. 64 is a partition of cruciform shape, preferably of metal and coated with a refractory 64a, while is secured to andl supported by a member 65 and runs centrally throughout the mold to provide four

spaces

66, 67, 68, 69 for the reception of the casting metal. 33 is the protective refractory. The method of forming castings by the construction shown in Fig. 8 differs in no way from those previously described with a like advantage as in the construction of Fig. 7 with regard to the localization of impurities by control of the cooling conditions.

While in connection with Fig. 1 I have shown the liquid casting metal as contained in a crucible I do not limit myself to such construction as it will be apparent that the container of the metal to be cast may have many forms. I may point out that the high speed production of castings of good quality calls for many precautions being taken notonly to insure luniform temperature of the liquid metal, but also that it be homogeneous in character. To this end I have devised a so-called dipping tank which has many advantages, as is disclosed in connection with Figs. 9, 10 and 11, showing plan, part sectional side and part sectional front elevation respectively.

Referring rst to Fig. 10, which represents a sectional side elevation along the line C-D-E-F of Fig. 9, a metal container or tank 72 having lifting lugs 73 and a pouring lip 74 is lined on the inside with refractory material 75 and contains liquid casting metal brought thereto by means of a ladle or other convenient method. A partition 76 arranged as shown is provided to divide the dipping tank into two

portions

77, 78. The metal in one of these portions 78 has its surface protected by flux or slag 79 to prevent oxidation or undue radiation while the metal in the other portion 77, is free of surface flux and is designed to receive the mold. To provide for free passage of metal between the two portions of the dipping tank the partition 76 is cut out at its lower crners as indicated at 80, 81 in Fig. 11, which is a. front sectional elevation along the line G-H of Fig. 10. A pipe loop 82 for circulating a cooling medium is provided as shown, this being for the purpose of maintaining the liquid metal at a temperature sufficiently low to obviate undue shrinkage in the finished casting.l

In the use of the dipping tank illustrated in Figs. 9, 10 and 11, it is highly important that the liquid metal be held at a uniform temperature in dipping space 77 and this is best met by DIO- Viding means for insuring free circulation. To this end I have designed a tilting table upon which the dipping tank just described may be mounted in pedestal bearingsnot shown, is fitted at or near either `end with

eccentrics

87 and 88 which vare keyed at with respect to each other. A

connecting rod 89 engages at one end with ecf' centric`87 and at the other end with a spherical bearing bushing 91, which is secured to the table A83 by means of a pin 92 having a head 93. Similarly, a connecting rod 90 engages at one end with .eccentric 88 and at the other with a spherical bearing. bushing 94 secured to the table 83 by* means cfa pin 95 having a head 96. The connecting

rods

89 and 90 are attached 'at points 90? apart in a horizontal plane with respect to the center of the table 83. Since the

eccentrics

87 and 88 are also spaced 90 apart,

as described, it follows that vwhen the shaft 86 is rotated clockwise, as designated bythe arrow in Fig. 13, there results a series of four vertical oscillations ofthe table 90 apart which produces a true gyratory motion of the liquid metal in the tank 72as illustrated by the arrows of Fig. 9.

My invention lends itself well for mass production of castings under automatic or semi-automatic operation and in Fig. 14 I show in plan and in Fig. 15 in elevation a-multiple-head turret casting machine for this purpose in combination with a dipping tank similar to that illustrated in Figs. 9, 10 and 11. It will be understood that the design of the casting machine can be varied many Ways, particularly with regard to the operation mechanisms. In order not to confuse the description of the main invention, the

' casting machine is represented diagrammatically.

Referring to Figs. 14 and 15, a pedestal 100 supports a turret 101 having extensions 102, supporting operating heads 103 terminating in

molds

104, 105, 106, 107, 108, 109. As will be seen, each mold may in turn be brought into position for immersion in the tank 72, the control of the turret, operating heads and molds being eifected by mechanical, hydraulic, pneumatic or electrical meansior a combination of several or all. In the position shown, mold 104 is ready to dip, 105 is in a position to drop its casting, which latter may be conveyed off by suitable means, while

molds

106, 107, 108 and 109 are open to inspection, the insertion of new cores, etc.

I have pointed out in this specification that my improved process for the making of castings includes means for shielding the exterior surfaces of the mold for'its protection against early deterioration, freezing of metal thereto and to obviate too rapid loss of heat from the molten contents and I haveY described in this connection the preferred constructions of using the refractory material toward these ends. In connection with the construction of Fig. 1 the refractory material completely surrounds the mold when the latter is closed for the purpose of taking up the molten material. In Figs. 5 and 6 a construction is disclosed in which the refractory forms part of the closed mold and in Figs. 16 and 17 I show this method of construction in greater detail.

Referring to Figs. 16 and 17, Fig. 16 shows a view in section of a mold joint similar to that of Figs. 5 and 6 While Fig. 17 is a view in elevation wherein the divided mold portions are designated as 42, 43, as before, and 33 is the refracvThis refractory is formed so that when the mold is closed there is presenteda series of conical holes 50 extending part way through such refractory and serve for the purpose of facilitating the escape of surplus liquid metal as the mold is closed. The use of refractory material as a parting face promotes the making of castings true toy size as there is no tendency of the liquid metal to chill on such refractory. When the parting faces are of metal, as for example in the construction shown in Figs. 1 and 3, the thickness o f the casting will vary with the thickness of the chilled lrr formed on such faces. Allowance for this may be made in designing the mold, but absolute uniformity of size of the castings will depend to an extent upon the skill and judgment of the operator.

' It is important that the refractory be of considerable mechanical strength combined with such minimum thermal conductivity as will prevent molten metal adhering thereto.` Such refractory may be a mixture of graphite, fire clay, asbestos fibre and the like. Although the refractory can be applied over the mold and its cooperating parts while in a plastic state, pieces of reinforcing material such as nichrome or other heat-resisting metal should be interspersed therein. It is frequently desirable to apply such rey fractory in segments or blocks, providing means for attachment as shown in Figs. 18 and 19. Referring to Figs. 18 and 19 in which 18 is a side sectional view and 19 a front view, the outer wall section of a mold or die 110 to which tiles or segments of refractory material 111, 112 are, attached by means of screws 113 is shown, the refractory being countersunk to receive the screw heads 114. Also,cthetsegments 111, 112 have, as shown, grooves about their outer edges so that when assembled there is provided a dove-tail opening 115 between adjacent segments. This dove-tail opening and the undercut countersinking for the screw heads should be filled with an elastic refractory cement. The segments 111, 112 are preferably constructed with reinforcement consisting of short pieces" of .heat-resisting metal 116 imbedded therein.

In connection with the use of the dipping tank illustrated in Figs. 12 and 13, it may be advisable under some circumstances to provide means for maintaining the temperature of itsl liquid contents constant, or for the purpose of increasing such temperature. This can be done in various ways, through the use of electric resistance, electric arc, gas or oil-fired devices. For the purpose I preferably employ an electric arc heating unit, as illustrated in Figs. 20 and 21, wherein Fig. 20 is a plan and Fig. 21 a sectional elevation view of a unit designed to fit over the reservoir portion 78 ofthe dipping tank 72 of Figs. 9, 10 and 11. Referring specifically to Figs. 20 and 21, a body 118 of refractory material having an inner arched dome based upon a metal frame 119 is provided with guide bushings 120 of heat resistant material through which project carbon electrodes 121. The electrodes 121 are so positioned that when connected to source of power supply and an arc is struck, such arc will be at the focal point of the arched dome, the latter being designed to be approximately parabolic in shape, so that the maximum heat will be reiiected downward. The bushings 120 are cored to provide 145 inner annular spaces 122, as shown, to permit of water or other cooling. i fixed bail 123 having an eye 124 is provided to .permit ready handling of the heating unit.

For a more complete Aunderstanding of my nu l process and the advantages to be gained by it, it is important to consider the transition changes accompanying the solidication of molten metal. If the cooling is slow the ensuing crystal structure is of large grain size which is conducive to weakness. Moreover the structure is variable as to composition, that portion of the casting which has solidified last usually carrying the unavoidable metal impurities in concentrated form. All substances expand when heated and contract upon cooling. In liquids the volumetric change is greater than in solids. It therefore follows that if a liquid metal can be poured into a mold at a temperature near its freezing point, the tendency for shrink cavities to form,will be much less than when pouring takes place at high temperatures. Accompanying solidication there is volume expansion or contraction. In cast iron, for example, solidication causes expansion. If the metal has been poured at too high a temperature the contraction in the mold may exceed the expansion which occurs in solidif'lcation, thus causing shrink holes. Under the usual conditions of forming castings the pouring temperature must necessarily be high. In my dip-casting method such temperature however may be quite low, as pointed out.

While the melting of the metal is no part of my invention I would point out that the temperature of the furnace must be high enough so that all the ingredients of the bath are thoroughly melted and amalgamated. Also, that all reactions are completed before the molten metal is poured into the dipping tank. Generally a temperature which satisfies these sequirements is too high to avoid harmful shrinkage. Therefore, as a preliminary to casting and dipping I reduce the temperature of the metal. For example with reference to the dipping tank of Figs. 9, 10 and 11 I employ the pipe loop 82 for circulating a cooling medium. This is a more desirable method of reducing temperature than the common one of dissolving scrap and the like, which introduces oxides and causes inhomogeneity. The temperature is reduced to a point, experimentally determined, which is dependent upon the composition of the metall and the size, shape and nature of the castings to be made. In this connection it will be noted that I provide means for heating as Well as cooling the metal in the dipping tank of Figs. 9, 10 and 11.

The molds which I employ have refractory coatings on their exterior surfaces. When such molds are immersed in the bath, at a depth where clean and homogeneous metal is to befound, upon opening, the metal will rush in from all sides filling up the space betweenthe parted mold portions almost instantaneously. As the metal encounters the comparatively cold surfaces of the mold interior it will chill on the respective faces in the form of a thin solidified sheet. The mold should then be closed quickly, before the heat fromthe bath proper causes redissolving of such chilled metal. If the timing is correct, this chilled metal protects the faces of the mold from eddies andV erosive action as the surplus metal is squeezed out. Upon closing of the mold a seal is provided as the solidified sheets meet at the parting faces, and due to these welding together they retain the correct amount of metal.

It has been indicated that divided molds used in connection with a liquid metal bath have been used hitherto. However, such molds were unprotected by a refractory and it was necessary to let them remain inthe bath until they reached approximately the bath temperature, otherwise the mold itself would be coated upon its exterior surfaces with metal which would prevent its being opened later for the ejection of the casting. When protected by refractory material, the mold will remain at a much lower temperature than when unprotected, while at the same time it is protected from erosive action. In fact, it would be practicable by the use of refractory protection and adequate cooling to employ a copper mold for the making of steel castings under my process.

`It will thus be seen that by my improved method the metal flows without restriction and from many directions, having only a short distance to travel. These advantages, combined with the lower pouring temperature and possibility of cooling from all surfaces largely eliminates the possibility of shrinkage cavities. If such occur, and this is at times unavoidable, they are vto be looked for in the central interior of the casting where the harmful effects are least, instead of near or at the surface region. This is well illustrated in connection with Figs. 22 and 23 showing a cast body having a massive portion 125 combined with an extension of smaller section 126. With reference to Fig. 22, 127 represents shrinkage cavities which may be expected under the usual process employing a sand mold, While 128 of Fig. 23 represents a single cavity of small size, located much more favorably as far as harmfulness is concerned, which may occur under the dip-casting method.

In some cases it is desirable to employ means for keeping the mold relatively cool,'where the castingis large in size relative to the mold itself. For such purpose I prefer to employ a jacketed mold as described, in connection with the construction disclosed in Figs. 6, 7 and 8. Such means for controlling the temperature of the mold are alsofapplicable in the control of the cooling of the casting itself, and offers a method of localizing the segregation as indicated in the discussion of the construction disclosed in Figs. 7 and 8. Here the means described causes the segregation to locate in the vicinity of a surface, which can be readily planed away, resulting in less loss than would occur through the cropping necessary under the usual methods of casting ingots.

It is important in the case of ingots or billets that cavities of all kinds be' guarded against. I therefore may employ compression at times, par- 12 ticularlyin combination with the construction illustrated in Figs. 5 and 6. The operation of forming a casting using power compression is as follows:v The mold is lightly closed and after a short period has been allowed to intervene to permit of 130 formation of a ratherthick shell on the mold parting faces, an elastic follow-up pressure is applied by means of the operating arms. 'Ihis is carried out by means of pneumatic, hydraulic or electrical means or the like, to compress the casting as fast as the contraction or expansion of the metal allows.

Under some conditions, especially for the mass production of small commercial castings, the interior of the mold faces may have inserts of a refractory for the purpose of retarding the cooling of thin sections of the castings; or the entire matrix may be lined with a refractory. However. such refractory should be hard and wear resisting, of the nature of fused quartz, graphite-cruciblematerial and the like, which are not easily destroyed by coming in contact with hot liquid metal.

Under the dip-casting process as described, castings can be made equal in surface finish to drop forgings and practically equal thereto in 150 strength; with the further advantagesthat the', metalbathcomprising separable'parts including'v process is applicable to intricate shapes, and to materials not suiilciently malleable for forging.

apparent tothose skilled in the art that changes may be made inthe modes of operation and forms v of apparatus disclosed without departing from I the spirit of my invention', and that certainfeatures of the invention may sometimes be usedv without a' corresponding use of other features.

I claim:

1. The process of casting metalsofhigh melt--V ing pointwhich comprises submerging] a cooled separable moldin a liquid metal bath', opening the `submerged mold to receive the' metal,l conducting heat from the liquid metabwithin the.V mold to the mold at a relatively ,quiclrratel to causejsolidification of the metal within the mold,- whilehindering flow ofV heat to themoldf from "metal surrounding the mold to prevent solidifica-.`

`tion of the metal exterior tothe mold, closingA the;

mold, and withdrawing the mold from-the bath."

" 2:. The process of casting metals of highj`x nelt`l ing point which comprises submerging ii/. cooled:y j'separable mold in a liquid metal ,batir'o'perfxingV 'the submerged mold-tojreceive themetal; conducting heat from` the liquidlmetal within-the 1jK '.moldqto the mold vat a-rela'tively' quicleratefby r4 3;Tihelpr'ocessof ,casting v'metals"eflliighfl eltf ing' point which comprisessubmerging}a cooled separable mold .in a liquid: ymetal -.bth,f} opening" l the submerged mold .to yreceiv'e.l th'ef'metal, con"- themold exteriorly thereof to prevent c'oollnggan'd'l` solidification exteriorly of the mold', and withdrawing the mold from the bathD 5. A mold structure for submersion in a molten -getherjto form a' closed chamber, means con- Lnectedito the mold partsvwhereby'the mold may beflower'ed into a metalvbathfand whereby the 4,mold 'structure lmay be'jclned to allow metal to f iiow"y thereinto lwherebythee mold structure may be closed ytoi'solategmetal 4.within the mold 100 si;rticture means 'tucoolthe` interior surface of .said vin'etal-members,y fand-'heat-insulating means metal members and adapted to'be brought toc vgether to form a. closed'chamber, means connected/to the mold .partswhereby the mold structure'` may be lowered into'fa-metal 'bath and whereby (the: mold structure may be opened to allow.- metal to .flow-thereinto and whereby the frommolten metal' surrounding saidjmold structure to said mold vstructure to permitthe mold structure in cooled conditionf to vcause solidification of metal within the lsaine -without substan-v tial cooling of molten metal exterior thereto.

. A mold structure fo'vi` submersion in a molten (metal bath comprisingseparable parts including metal members' and adapted-*to be brought tol k'll-,ffAgmol'd structure forlsubmersion in a metal 1.05 bath comprising-separable parts'including metal lmembers and adapted togbe brought together to entirely f covering thef anterior surfaces of said form aaclosed chamber, means connected with thc'mold-parts wherebythe'mold structure may be 1,,clllilftvv into a metal'bathfand whereby the 110 A. olds'tructuremay'be opened vto allow metal to flow thereintojand Wherebythemold structure beclDSd to. isolate metal therein, and refractorymaterialfentirely covering the outside surn parting, 'stu'aces between thel mold parts.v

8.'.(A moldjstructure for submersion in a metal v 1i comprising separable parts' including metal mbers'andadapted to .be brought together to. formia'fzclosed chamber, meansconnected with 120 theml'djparts whereby .the moldfstructure may lowered into-a metal vbath whereby `the mold-'structure may be .opened to allow metal to flow threinto' and whereby' the mold structure may/.be closedto. isolate l metal therein, re- 125 factoryl material entirely. covering vthe outside surfaces. ofsaid metal members and -forming the Y parting surfacesv between the moldpar'ts, and tgegane' to supply cooling iluid to said metal mem 'vLARs:o. NrrsoN. 13

fcesiofrsaidmetal members and forming the v