US2274580A

US2274580A - Production of metal castings

Info

Publication number: US2274580A
Application number: US300874A
Authority: US
Inventors: Bailey Richard William
Original assignee: English Steel Corp Ltd; Metropolitan Vickers Electrical Co Ltd
Current assignee: English Steel Corp Ltd; Metropolitan Vickers Electrical Co Ltd
Priority date: 1938-10-26
Filing date: 1939-10-23
Publication date: 1942-02-24
Anticipated expiration: 1959-02-24

Description

Feb. 24, 1942.

R, w. BAILEY PRODUCTION OF METAL CASTINGS Filed Oct. 23, 1939 2 Sheets-Sheet 1 w z y \x \KOF A.

. T 6 7 Halflj v RICHARD ww i vflmfiam ATTORNEYS Patented Feb. 24, 1942 2,274,580 PRODUCTION OF METAL CASTINGS Richard William'Bailey, Hale,'England, assignor to Metropolitan-Tickers Electrical Company Limited, London, a company of Great Britain, and English Steel Corporation Limited, Sheffield, England, a company of Great Britain Application October 23, 1939, Serial No. 300,874 In Great Britain October 26, 1938 9 Claims. This invention-relates to, the production of hollow metal castings, and particularly, though not exclusively to the production of hollow in- 7 guts of steel.

- An object of the invention is to increase the amount of liquid metal which is frozen around the core by the extraction of heat from said metal into the core.

Another object of the invention is to provide means for coolingthe interior surface of a hollow casting beyond thatarising from the thermal capacity of the core of the mould.

The invention provides for removing the heat absorbed by the core by the use of a heat carrier such as a gas or liquid which is caused to pass through the core, or by a solid ,body which, after being heated, can be removed from the core and replaced by a fresh cool body.

I The invention may be carried out in practice in many different ways. For example, when air is employed as the carrier, a duct or ducts may be provided extending through the solid metal part of the core and mould base. A flow of air 2 through the duct may be caused by means of a fan, or by a natural draught, or by the action of a jet of air or steam. In the case of a hollow ingot, which wouldfbe cast with its bore and core vertically, the cooling air duct may advantageously extend from'the base of the mould" to the top of the core, the air entering at'the bottom and leaving at the top by reason of the natural draught. The" draught may be augmented by a chimney-like extension of the core,

and either or both the chimney and the inlet tovthe core duct may be shaped or flared to assist the draught if desired. The surface of the cooling duct in the core may be ribbed, or otherwise extended to increase the cooling action of the air, and the ribbing or the surface may be varied or graded so as to vary the cooling in pillar to'the shaft. The bore in the pillar may be cylindrical or tapered, or of other suitable form, as also the shaft, was tograduate the cooling and cause it to diminish as the'top of the ingot is approached. Means are provided for removing the shaft when this has beenheated by the heat radiated from the pillar and replacing it with a cold shaft, which may be either of the same or different form in order to vary the any desired manner, for example by causing it 1 todiminish as the distance from the bottom of the ingot increases.

Where water cooling is employed water may be passed through the cooling duct or ductsjin the core, or it may be allowed to evaporate under the heat extracted from the core, loss by evaporation beingmade up.-

Where a solid body is used as-a carrier it may .be in the form of a metal bar or shaft of cast iron, steel or copper, for example, which is located in a bore in a central portion or pillar of the core. The shaft may advantageously extend to about the level of the refractory head of the mould. Heat will then be radiated from the cooling effect of the core. An appreciable gap may be provided between theshaft and the bore of the pillar so that air can be circulated between the pillar and the shaft.

Additional air or water cooling, or both, may be arranged by providing ducts through the shaft through which air or water is circulated. In some cases the gap between the shaft and the pillar may be arranged to be filled by a low melting point metal, the lower end of the hole in the pillar being connected to a conduit through which the moltenmetal may be introduced and removed, the principle of action and operation being similar to that described in the specification of United States Letters Patent No.

1,946,450,- granted February 6, 1934.

The invention is applicable to the production of hollow ingots in a mould having a core which is arranged to yield easily and exert little or no bursting load on the cast metal around the core.

For example in such a case the coremay con-" sist of a comparatively thin metal shell which has sufficient thermal capacity to freeze quicklya layer of liquid metal outside of it and which at the same time would itself be heated to nearly the temperature of the frozen layer, and in becoming plastic would offer little or'no resistance to compression by the ingot and be able easily to contract with the ingot on cooling. .Insuch a case the surface of the core-in contact with the cast metal may become fused, but the core still remain intact and be able to retain a cast metal round it in shape although it might become bonded with the casting. If desired bonding of the shell with the casting may be prevented by a suitable dressing of the shell surface. The shell-may\be a plain cylinder, or it may be cor rugated'or fluted parallel to the axis so as to increase its flexibility. r Such a core may be made in one piece as a pipe, or may be formed by wrapping a thin sheet so that its sides overlap and tacking or. joining the overlapping sides. in some suitable manner, as by spot welding for example. In applying the present invention to such a case the interior of the shell would be cooled by a gaseous, liquid or solid carrier as 'hereinbefore described. Advantageously a-solid' cooling mass would be provided within the shell of a size and shape offering no restraint to the contraction ofthe shell, and the action of the cooling mass might be augmented by gaseous cooling by the circulation of air for example. The cooling mass would be in position at the time of casting so as to be immediately available for cooling purposes and after it had become heated could be removed and replaced by another cooling mass so as to continue the extraction of heat and consequent cooling of the shell.

In an alternative application of the invention the shell may be situated on the outside of a hollow cylindrical pillar, there being a gap between the two in which a low melting point metal, for example lead, is situated, or it may be introduced. The purpose of this low melting point metal is to improve the thermal conductivity between the casting and the pillar, and also to counterbalance the force acting upon the shell from the head of liquid metal in the ingot. The interior of the pillar may, then be subjected to cooling by a gaseous, liquid or solid carrier as hereinbefore described.

In order that the invention may be clearly understood several constructions of mould for carrying out the invention will be described by way of example withreference to the accompanying drawings in which Figs. 1,2 and '4 are sectional elevations of constructions embodying the invention for casting hollow metal ingots, whilst Fig. 3 'is a sectional view to an enlarged scale of a detail of Fig. 2.

Referring first to Fig. l, the body of the mould is indicated at I being mounted on a base 2. A hollow core 3 of tubular form ismounted within the mould engaging at its lower end with the base 2, said core having sufficient thermal ca-' pacity to freeze quickly a layer of the ingot surrounding it and becoming plastic s'o as to ofler only small resistance to contraction of the ingot as hereinbefore indicated. A refractory head 4 may, in the usual manner, be arranged above the body I. It will be seen that the tubular core 3 provides a duct which extends from the base 2 to 'the top of the core and the base} is provided with a central aperture 5 in alignment with the core 3 whereby a heat carrier or cooling medium may enterthrough said, aperture 5 and pass up-.

forced circulation may be obtained and may be disposed either to force the fluid through the passage or to induce the movement thereof from the top of the passage; .The aperture 5 may be fiared'as indicated to assist the natural draught whilst for the "same purpose the core 3 may be extended upwardly above the mould to provide a chimney.

Insteadof employing an or water as the heat carrier the latter may be constituted by a solid I member, such as a metal bar 8 of cast iron, steel or copper for example, which is located within I the core 3'. This bar 8 is suspended from a supporting. beam 8, which is mounted by packing blocks I8 upon the refractory head 4, by means metal into the mould, will take up from the core 3 heat which the latter has absorbed from the 10 poured metal and which is radiated to the bar. When the temperature of the bar 8 has risen to an appropriatedegree said bar is extracted from the core and may be replaced by a further cold bar whereby further heat can be extracted from the casting, and. this process may be continued according to requirements.

As shown in Fig. 1 the bar 8 and core 9 may be so shaped that the gap therebetween varies along the core, for example increases progressively from the bottom of the bar upwardly, whereby heat will be extracted at a greater rate from the lowerparts of the ingot than t e upper parts so that the ingot will be cooled wardly as is desirable. For obtaining the control of heat flow in the manner above indicated the bar 8 may be taperedor stepped as also may the inner surface of the core 3. The bars such as 8 which are inserted in turn within the core will have shapes whereby the desired distribution of heat extrac 0 tion along the core is obtained during the different stages of the cooling.

If desired, when employing a solid heat car rier, such as the bar 8, a fluid heat carrier may also be passed through the core 3, and. to this end an appreciable gap,'as indicated at I3, may be arranged between the bar and core to provide the requisite passage for the fluid, which may conveniently be air under natural or forced draught as hereinbefore indicated. As will be appreciated, where the bar 8 is employed as the heat'carrier without a -fluid heat carrier, the apertured base 2 may be replaced by a' solid base. Additional air or water cooling, or both, may be arranged if desired by providing ducts within the to extract heat from said bar.

of the kind in which the core includes a thin shell which is adapted to be compressed upon contraction of the ingot during cooling. mm. 2 'the body of the'mould is'again indicated at I being mounted on a base 2 and supporting a refractory head 4. The core comprises a hollow pil1ar2l which registers at its lower end with-an opening surrounds the pillar 20 forms the outer surface of the core. Cooling of the core maybe obtained in any of the ways described with reference to Fig. 1', as for instance by a solid bar 8 located in The pillar 28 is secured in place by means of a clamping bolt 22 threaded into a cross-bar 23 which extends across the pillar 20 and engages at its two ends with respective projecting ledges, one of which appears at 24 formed on the inner surface of the pillar. At its lower end the bolt 22 extends through a second clamping bar 25 which engages at its ends with the underside'of the base 2 on opposite sides of the orifice 5, the clamping 1 7'0 being completed by a nut 26. The pillar 20 will be stayed to the top of the head 4.

In the construction illustrated the upper part bar 8 through which air or water is caused to flow I 5 in the base 2, and a thin metal shell 2I which core 20, cooled by natural or forced air currents.

' by radiation over .the space within the shell 2| at-this part of the pillar is filled with'a heat insulating material 23. The shell 2| is'arranged with sufficient thermal capacity to freeze quickly a layer of liquid metal surrounding it, but will itself at the same time be heated nearly to .the temperature of the freezing layer so as to become plastic and thereby offer little or no resistance to compression by tract with the ingot as-the latter coolsi The shell may be a plain cylinder or it may be corrugated or fluterf parallel to its axis so as to increase its flexibility. The shell may .be made in one piece in the manner of a pipe or .may be formed by wrapping a thin sheet so that its sides overlap and tacking or joining the overlapping sides in any suitable manner, for example by seam welding.

The heat may be transferred to the pillar for extraction by the heat carrier'within the latter the gap 29 which is provided between the shell 2| and pillar 20. Alternatively, said gap 29 may contain a low melting point metal or alloy, conveniently lead,.whereby .the

filled by a low meltingpoint metal or alloy to improve the heat conduction to the solid heat carrier.

An example of the above kind is shown in Fig. 4 in which the mould comprises a body and a 'solid base 2 on which is mounted a hollow core the ingot and will thus be able'easily to conthermal conductivity between the shell 2|, and

therefore the casting, and the pillar 20 will be improved and said metal or alloy will counterbalance the force acting upon the shell 2| due to the hydrostatic pressure of liquid metal within the ingot.

Preferably the lead or other low melting point metal or alloy may be run into the space 29.

during the pouring of the ingot and the height of lead within the shell 2| may be controlled as desired thereby'to provide a pressure on the shell counterbalancing the pressure of the metal in trically heated outlet pipe32Qwhich extends into proximity to the bottomof the'pot and is con- 'nected with an orifice 33 in the wall of the pillar 20. The pot,3|l is provided with a pipe 34 which is connected with a suitable source of compressed air or other gas represented by a gas cylinder 35 having a regulator valve 36. By this means admission of pressure from the cylinder 35 to the pot 30 .will cause the molten lead within the latter to-flow through the pipe 32 into the annular space 29'between the shell 2| and core 20 thereby to regulate pressure within the shell and also surface the mould and to regulate the heat flow from the 3. A bar 8 is fixed and centred within said core as inthe arrangement of Fig. 1. The base 2 is formed with a well 50 below the core and said well is connected by an electrically heated pipe 53 with a melting pot 54 mounted in a furnace v55 and from which molten lead is adapted to be forced into the well by means of compressed air' from an air cylinder 56 under control of a valve 51 similarly to the arrangement shown in Fig. 2. In operation, the valve 51 is adjusted so as to cause the molten lead to flow into the space between the bar 8 and core poured, theoperation being similar to that dee scribed in United States Patent specification No. 1,946,450. When it is desired to replace the bar 8 by another banthe lead may be run back into the pot 54 the newbar substituted and the lead forced back into space 58. I

I claim:

1. For making a hollow metal casting, a mould having a hollow core, a removable solid body disposed in the space within said core and removable from the latter during the formation of thecasting, said body being adapted to to take up from the said. core heat received by the latter from the casting, and an outer surface on said body; different parts of which surface are spaced from respectively adjacent parts of the boundary of said space by distances which vary along the core so that different rates of cooling of the casting are obtainable at difierent parts thereof along the core. F u

2: For making ahollow metal casting, a mould having an aiierturedbase, a hollow core open at both ends and registering at one end with surfaces of the mould base "surrounding the part of which is spaced from. the adjacent inner v surface of said hollow core so that such spaced apart surfaces of the core and removable solid body define. a passage extending through the the heat flow from the ingot in the manner he fore indicated. The height of lead within the shell 2| may be estimated by means of a pressure gauge 31 registering the pressure of air within the pot 30.

Fig. 3 illustrates the preferred construction of the lower part of the core. In this arrangement the pipe 32 is welded into theorifice 33, as indicated at 38. The lower end of the shell 2| is welded to the pillar 20 as indicated at 39 with an interposed annular packing piece Ml. Suitable ployed, the gaps between said mass and the in ner surface of the core may be arranged to be core from t e base to the other end thereof.

3,. For making a hollow metal casting, a mould having an apertured base, a hollow core open at both ends and registering at one end with surfaces of the mould base surrounding the aperture in the latter, and aremovable solid-body disposed within said core and removable from the latter during the formation-of the casting, said body having an outer surface at least part of which is spaced from the adjacent inner surface of said hollow core so that such spaced apart surfaces of the core and removable'body define a passage extending through the'core from the base to the other endthereof, and in combination therewith means for causing a fluid heat carrier to flow through said core from one end to the other packing 4| is provided between the base 2 and f able from the latter during thevformation of the casting, said body being. adapted to take up from said core heatfabsorbed by the'slatter from the casting and i'ncombination with said mould,

3, as indicated at 58 to progressively, higherlevels as the ingot means for inserting in the path of heat flow from the casting to said solid body a low melting point heat conductor and means for controlling the -latter from the'casting, surrounding said pillar a yieldable shell of, sheet metal spaced from said pillar, and a low melting point metallic heat con ductor disposed between said shell and pillar,

together with means for controlling at will the length of the core along which said metallic heat conductor is present between said shell and pillar.

6. For making a hollow metal casting, a mould having disposed therein a core comprising a hollow pillar upstanding from the base of the mould, a removable solid body disposed within said pillar and removable from the latter during the formation of the castin said body being adapted to take up heat from said pillar, and a yieldable shell of sheet metal surrounding and spaced from said pillar, a conduit for introducing a liquid low melting point heat conductor between said shell inserting within said core a solid body having comparatively high heat capacity and being at a temperature materially below that of the cast metal, maintaining the solid body in said core for and pillar, and means for controlling the height of the level of said heat conductor shell.

'7. A process for making'hollow ingots, comwithin said prising-- casting the metal around a hollow core,

a predetermined period of time, with its walls substantially spaced at all points from the walls of the core, t'o'eflfect extraction of heat from said ingot by convection and radiation at a rate comparable to the loss of heat at the outside of the ingot, to thereby preclude segregation adjacent either the' inner or outer surfaces of the ingot, removing said solid body and replacing it with a second solid body similar to but being at a lower temperature than the removed body, and extracting further heat from the ingot.

8. The process set forth in claim '7, together with the further step of introducing a fluid into the space between said body and said core for accelerating heat transfer from said ingot to said body.

9. For making a hollow ingot, a mould having a hollow, comparatively thin-walled core, means for removably supportingwithin said core a solid body of comparatively high-heat capacity, with its external walls substantially spaced at all points from the internal walls of the core, and being operable to extract heat from the ingot at a rate comparable to the rate at which heat is dissipated from the exterior of the mould, and having an external diameter at least as great as the radius of the internal wall of the core.

RICHARD WILLIAM BAILEY.