US1930408A - Production of metal castings - Google Patents

Description

Oct. 10, 1933. R, w, BAILEY ,4

PRODUCTION OF METAL CASTINGS Filed March 16, 1953 :s Sheets-Sheet 1 INVENTOR Richaird W. Bailey ATTORNEY Oct. 10, 1933. R. w. BAILEY ,408

PRODUCTION OF METAL CASTINGS Filed March 16, 1933 3 Sheets-Sheet 2 INVENTOR Richard W. Bailey ATTORNEY Oct. 10, 1933. R, w. BAILEY PRODUCTION OF METAL CASTINGS Filed March 16, 1933 3 Sheets-Sheet 3 INVENTOR Patented Oct. 10, 1933 1,930,408 PRODUCTION OF MIETAL CASTINGS Richard William Bailey, Hale, England, assignor to Associated Electrical Industries Limited and English Steel Corporation Limited, companies Great Britain Application March 16,

1933, Serial No. 661,126,

and in Great Britain October 31, 1931 Claims.

This invention relates to the production of metal castings and more particularly to the production of ingots cast in metal moulds, though it is not limited to this purpose.

The object of the invention is to provide an improved method whereby the cooling effect of the mould upon the casting may be varied and controlled.

According to the invention molten metal is poured in a metal mould formed with one or more spaces within the walls thereof, and a comparatively low melting point metal or a fusible salt is caused to flow upwardly into said space or spaces and withdrawn therefrom when desired, whereby to vary the conductivity of the walls of the mould and regulate at will the cooling effect on the casting during and/or after the pouring of the molten metal.

The low melting point metal or fusible salt may be admitted to the space or spaces in the walls of the mould by any suitable means andbne means which is suitable for use in connection with a low melting point metal is described in my copending United States application, Serial No. 551,769, filed July 18, 1931. Wheremore than one space is provided in the walls of the mould low melting point metal may be supplied to one of the spaces and a fusible salt supplied to the other space or spaces if desired, or the same material may be supplied to all the spaces. The admission of a low melting point metal, or fusible salt to the spaces within the walls of the mould may be independently controlled.

The thermal conductivities of the space or spaces in the walls of the mould may be reduced when free of low melting point metal or fusible salt is introduced into such space or spaces by breaking up the space or spaces into compartments by a yielding filling of a material, preferably metal, capable of withstanding the conditions obtained. For example asbestos, packed refractory material or thin corrugated sheet metal with corrugations runnifig in the vertical dirction or sheet metal having corrugations running circumferentially and perforated to permit the ready flow of the low melting point metal or fusible salt in the gap when desired, may be employed.

Although the present invention is capable of independent employment it is very advantageous ly applied to the production of metal castings wherein a low melting point metal or fusible salt is introduced into the gap formed between the casting and the walls of the mould by contraction of the casting and/or expansion of the walls of the mould. The space or spaces within the walls of the mould may communicate with the interior of the mould and/or with each other so that low melting point metal or a fusible salt may be admitted to one of the spaces and pass from thereto the other space. As an example, when casting an ingot where it is desired to support the solidified outer shell ofthe ingot to prevent axial cracks or other defects, low melting point metal may be admitted to the gap between .the casting and the walls of the mould shortly after pouring is commenced. The low melting point metal will rise in the gap, but unless the mould or parts adjacent to the space in the walls thereof are heated beforehand it will solidify on entering said space, or perhaps in passing through the aperture from the interior of the mould to said space, and thereby be prevented from flowing into the space. After the completion of pouring, the low melting point metal is maintained in the interior of the mould until the outer part of the ingot has solidified to a suflicient depth to permit of the removal of the support w oh the low melting point metal affords to the ingot. The thickness of the inner or those portions of the walls of the mould between the interior of the mould and the space within the walls is made sufficient to provide adequately for the solidification of the outer part of the ingot to the requisite depth before the level of the low melting point metal in the gap immediately surrounding the ingot islowered. The good thermal connection between the ingot andthe inner portions of the walls of the mould obtained by means of the low melting point metal results in heating up the inner portions of the walls so that the low melting point metal, can ,fiow into the spacewithin the walls without solidifying. The level of the low melting point metal in both spaces may now be varied to bring about complete solidification of the ingot in the direction from the bottom to the top.

In some cases the low melting point metal or fusible salt may be introduced in the form of a solid prior to pouring the casting. The solid is melted by the heat of the casting so that the liquefied metal or salt will rise in the gaps to the desired height and at the desired rate to control the-cooling as required. Such a method of introducing low melting point metal'in solid form to the interior of a mould is described in U. S. Patent No. 1,923,000, dated August 15, 1933, in connection with the production of metal castmgs.

In the accompanying drawings Figs. 1, 2 and 3 show somewhat diagrammatically three different types of ingot moulds that may be used in practicing the method.

Fig. 4 is a sectional elevation of a preferred constructional form of an ingot mold that may be used.

Fig. 5 is a cross-sectional plan view of the mould shown in Fig. 4 taken on the line A-A of Fig. 4.

Fig. 6 is a sectional elevation of the lower part of the mould shown in Fig. 4 taken on the line B-B of Fig. 5.

Fig. 7 is a fragmentary sectional elevation of the mould taken on the line C-C of Fig. 5.

Referring to the drawings, the ingot mould illustrated in Fig. 1 comprises a body portion or outer wall 1 of cast steel united to a base portion 10, and is furnished with an interior cast-iron liner or sleeve 2 spaced somewhat from the body portion or outer wall 1 to provide an annular space or gap 3. The mould is equipped with a feeder head 4 of refractory material. When the ingot 5 has been poured and solidification occurs, a gap 6 is formedbetwe'en the surface of the ingot and the interior surface of the liner 2. Low melting point metal, such as lead or another fusible substance, may be admitted through an inlet '7 provided in the mould base 10 to occupy the whole or some part of the gap 6. A separate inlet 7' may be provided for admitting the same or a different substance to the gap 3.

In the construction shown in Fig. 2, the space or gap 3 is provided in the upper part of the mould only, the lower part of the mould 1 being made solid of cast steel. The liner 2 does not extend to the base 10 of the mould but is supported on a ledge 8 formed on the lower portion 1 of the mold. An outer sleeve 1 of caststeel forms the outer .wall of the upper portion of the mould and is supported on the outwardly extending flange 8. An inlet '7 is provided communicating with the interior of the mould,'and a further inlet 7* may be provided for the annular gap 3.

In the arrangement shown in Fig. 3, an intermediate liner 9 of cast-iron for example is disposed between the inner cast steel wall 2 and outer cast steel wall 1 of the mould. The wall 2 is formed integrally with the base 10 and lower portion 1" of the mould. The sleeve 9 and the wall 1 are supported on an outwardly projecting flange 8* formed on the lower portion 1 of the mould. The sleeve 9 and walls 2 and 1 are spaced apart to provide annular gaps 3 and 3. As in the arrangement shown in Fig. 2, an inlet 7 communicates with the interior of the mould and separate inlets '7' and Ta may be provided for the annular spaces 3 and 3 respectively between the intermediate liner 9 and the inner wall 2 and outer wall 1 respectively.

Referring to the arrangement shown in Figs. 4, 5, 6 and 7, the mould illustrated is for producing cylindrical ingots and consists essentially of two concentric cylinders, an inner cylinder 2 of cast iron and an outer cylinder 1 of cast steel, which are mounted on and clamped to a bottom plate 10. As shown in Figs. and "I, the outer cylinder 1 is secured to the bottom plate by means of six shackles'll engaging lugs 24 formed at the lower end of the cylinder 1 and, as will be seen from Fig. 4, the inner cylinder 2 is clamped to the bottom plate 10 by means of six bolts 12 engaging lugs 13 formed in'the bottom plate 10 and passing through holes formed in a securing plate 14 which bears upon the upper end of the cylinder 2. Between the heads of the bolts 12 and the lugs 13 are interposed strong compression springs 15 which allow for expansion of the inner cylinder 2 by becoming further compressed when the mould expands due to heat. The space or gap 3 between the inner cylinder 2 and the outer cylinder 1 has disposed therein strips or sheets 16 of corrugated metal, such as corrugated iron. The strips of corrugated iron 16 assist in insulating the cylinder 2 from the outer cylinder 1 and prevent the circulation of currents of air in the gap 3 Vertical channels are provided between the strips 16 to facilitate the passage of lead into and out of the gap 3. A refractory feeder head 4, comprising a cast iron or steel shell lined with refractory material 26 is seated on the plate 14. As shown in Figs. 5 and 6, an inlet 7 is provided in the mould base l0 which communicates with the interior of the mould, and this inlet serves for the introduction or withdrawal of lead in a molten state or other fusible material to or from the interior of the mould. The inlet 7 may conveniently be connected to a lead melting pot from which lead can be forced into the mould under pressure. The inlet 7 may be heated electrically in a known manner to maintain the lead in a molten state when necessary.

A pipe 17 is disposed exteriorly of the mould and communicates at one end with an inlet 19 which, as shown in Fig. 6, communicates with the space 3 between the inner and outer cylinders 2 and 1 respectively. and at its other end with an inlet 20 communicating with the interior of the mould. The pipe 17 is adapted to be heated by electrical means, or it may be allowed to 0001 if required. The conductor for supplying electric current to the pipe 17 is denoted at 18.

Instead of supplying low melting-point metal from outside the mould, this may be provided within the mould. Thus a slab of lead 28 of sufficient volume to fill the gap produced between the ingot and the inner mould wall 2 when the ingot solidifies, and sufficient just to float the ingot may be placed in a recess 27 formed in the base 10 of the mould before the pouring is commenced. This slab of lead 28 is protected from the molten metal by a steel plate 21 covering its surface, and a steel slab 22 is disposed on the central portion of this plate to protect it from the stream of molten metal during pouring.

Before the pouring is commenced, the pipe 1'7 connecting the interior of the mould to the space 3 is kept cool so that lead therein is maintained in a solid condition, preventing flow in the pipe.

As the steel is cast into the mould, the lead slab 28 melts and the molten lead rises in the gap formed between the ingot and the mould by the contraction of the ingot and/or the expansion of the mould, thus supporting the newly formed ingot skin and at the same time enabling heat to be transferred rapidly to the inner mould wall 2. On account of the different densities of steel and lead, the height to which the latter rises will be of the order of .7 of the height of the steel. The dimensions of the inner mould wall 2 are such that this height is suflicient 'to enable a suitable thickness of ingot shell to solidify and when this stage has been reached, the lead 28 is drawn out of the gap through the inlet 7 and into the lead melting vessel. When the mould is drained in this manner, the ingot sinks to the bottom of the mould and consequently a space is formed at the top of the mould between the conical portion of the ingot head and the feeder head 4. The large air gap thus formed acts as a heat insulator and retards the further cooling of this portion of the head.

The ingot 5 may now be cooled slowly from the bottom upwards at asuitable rate by admitting lead into the mould from the lead vessel, and if the connecting pipe 17 is heated, a passage will be provided for molten lead between the gap 3 and the gap between the casting and the wall 2, and consequently the lead will rise equally in the two gaps. The effect of this is to provide a path for the flow of heat from the in ner cylinder 2, which is at a high temperature, to the outer wall 1 which is relatively cool, and also to provide a similar path from the ingot 5 to the inner mould wall 2. In this manner heat is transferred comparatively rapidly from the ingot to the outer mould wall 1 up to the point where lead ceases to fill gaps, and above this point comparatively slowly owing to the high temperature of the inner mould wall, its inability to transmit heat rapidly to the outer mould wall on account of the gap 3 and the presence of the normal gap between the ingot and the inner wall 2 solidification of the ingot must therefore take place upwards rather than inwards. When the lead has attained a sufficiently high level it is drained off from both gaps into the containing vessel.

I claim:

1. A method of producing metal castings, comprising pouring molten metal into a mold, introducing into upwardly extending cavities in the side walls of the mold a liquid material of good heat conductivity having a melting point lower than that of the metal being cast, and varying the level of the liquid material in the cavities to vary the thermal conductivity of different parts of the mold walls from the inside to the outside of the walls, to regulate the cooling of the casting.

2. A method of producing metal castings, comprising pouring molten metal into a mold, introducing into upwardly extending cavities in the side walls of the mold, during the pouring of the metal, a liquid material of good heat conductivity having a melting point lower than that of the metal being cast, and varying the level of the liquid material in the cavities to vary the thermal conductivity of different parts of the mold walls from the inside to the outside of the walls, to regulate the cooling of the casting.

3. A method of producing metal castings, comprising pouring molten metal into a mold, introducing into upwardly extending cavities in the side walls of the mold of a fluid metallic substance having a melting point lower than that of the metal being cast and varying the level of said fluid metallic substance in the cavities to vary the thermal conductivity of different parts of the mold walls; to regulate the cooling of the casting.

4. A method of producing metal castings, comprising pouring molten metal into a mold, introducing into upwardly extending cavities in the side walls of the mold a liquid material of good heat conductivity, introducing into other upwardly extending cavities in said side walls outwardly of said first cavities a liquid material of good heat conductivity, and varying the level of the liquid material in the cavities to vary the thermal conductivity of diirerent parts of the mold walls from the inside to the outside of the walls to regulate the cooling of the casting.

5. A method of producing metal castings, com prising pouring molten metal into a mold, permitting the poured metal to partially solidify, in-

troducing between at least a part of the solidified surface of the metal and the side walls of the mold fluid substance having a melting point lower than that of the metal being cast, introducing into upwardly extending cavities in the side walls of the mold a liquid material of good heat conductivity, varying the level of the fluid substance in the mold to vary the thermal connection between the casting and the walls of the mold, and varying the level of the liquid material in the cavities to vary the thermal conductivity of different parts of the walls of the mold from the inside to the outside of the walls, to regulate the cooling of the casting.

RICHARD WILLIAM BAILEY.

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