US1946451A - Production of metal castings - Google Patents

Description

3 Sheets-Sheet l I NVENT OR Richard W. Bailey 4% R. W. BAILEY & Ga X ATI' ORNEY Feb. 6, 1934.

PRODUCTION OF METAL CASTINGS Filed April 12, 1932 R. w. BAILEY ION Feb. 6, 1934.

3 Sheets-Sheet 2 FiI Sd April 12, 1932 Feb. 6, 1934. R w. BAILE 3,946,451

PRODUCTION OF METAL CASTINGS Filed April 12, 1932 3 Sheets-Sheet 3 INVENTOR Richard W. Bailey ATTORNEY Patented Feb. 6, 1934 UNITED STATES FATE PRODUCTION OF METAL CASTINGS Richard William Bailey, Hale, England, assignor, by direct and mesne assignments, of one-half to.

Associated Electrical Industries Limited, a

Application April 12, 1932, Serial No. 604,818, and in Great Britain April 22, 1931 12 Claims.

This invention relates to the production of metal castings and has for its object to construct improved cores for use in producing hollow or tubular castings. The invention is especially useful in manufacturing hollow ingots of steel but is not limited to such use.

In making hollow metal castings the spaces within the mould which are to be wholly or in part surrounded by cast metal are frequently occupied by cores. These cores, as the metal cast round them cools down and contracts, must either be removed, broken up or be composed of a material which is more or less readily com pressible in order to prevent undue stress being developed in the casting as it cools. For example, in the case of a cylindrical or prismoidal tubular metal in'got having an axial core, it is necessary that the axial core shall be capable of being removed, broken up or reduced in crosssectional dimensions. By this means the forces which would otherwise be occasioned between the core and the ingot as the latter cools are obviated or reduced to a safe magnitude. In casting ingots, especially of steel, it is desirable that the core should be made of metal where it makes contact with the cast metal of the ingot so that such cast metal shall be as free as possible from non-metallic impurities which might be taken up from the core.

According to the present invention a collapsible or compressible metal core is provided for use in producing hollow metal castings which is constructed partly of metal parts which will not melt at the highest temperatures to which the core is to be subjected and partly of another metal or alloy of a comparatively low melting point or another easily fusible material. Space is provided to which some or all of the latter metal or alloy can flow away when liquefied and the other metal parts of the core are so arranged that they can then move relatively to each other in a manner to cause a reduction in the cross-sectional dimensions of the core when necessary. In some cases the liquefied parts of the core may be arranged to flow into the space formed between the inner surface of the mould and the outer surface of the casting due to contraction of the latter as it solidifies and the expansion of the mould.

In producing hollow steel ingots, for example, the core may be composed of steel or cast iron parts combined with lead or other easily fusible parts. The proportions and arrangement of these parts are such that at a suitable interval of time after the outer and inner regions of the ingot have solidified to a desired depth at any given level or axial position in the ingot the lead parts of the core will melt and remove the constraint from the other parts which, owing to the extent of the solidification of the cast metal at the outer and inner regions of the ingot, is no longer required.

The accompanying drawings illustrate somewhat diagrammatically and by way of example various manners of carrying out the invention in practice.

Fig. 1 shows in vertical cross-section a mould for casting a hollow or tubular ingot of cylindrical or prismoidal external form.

Fig. 2 shows in horizontal cross-section a portion of one form of the composite metal core of a mould such as that shown in Fig. 1.

Figs. 3, 4, 5, '7 and 8 illustrate various alternative methods of supporting the constituent parts m of the mould core.

Fig. 6 represents a mould for casting a hollow cylindrical casting or ingot which is closed or solid at its upper end.

Figs. 9 and 10 show in sectional elevation and in plan respectively a construction of a cap for the upper end of a mould core, as used in the arrangement illustrated in Fig. 6.

Referring to Fig. 1, a mould base-1 constructed of steel or cast-iron is formed at its central portion with a well portion 2. A mould body 3 rests on the base portion 1 and carries at its upper end a refractory head i of normal construction. The mould is provided with a core comprising a central steel pillar 5 which may be solid or hollow in construction and rests in a recess formed in the well 2. The pillar 5 is surrounded by segmental blocks 6 of steel or cast iron which are spaced from the pillar 5 by a filling or distance piece 7 made of'lead or other low melting point metal or alloy. The composite core is held to the base 1 by virtue of its own weight, but if necessary a bolted connection or other fastening may be provided between the pillar 5 and the base portion 1. The segments 6 are spaced so that the gaps 8 between them are not sufiiciently wide to permit metal to pass from the ingot during the casting process, but they will permit the segments to close in on the central pillar 5 when the low melting point metal 01' alloy melts away, the number of segments 6 being sufiicient to enable the necessary reduction in cross-sectional dimensions to occur.

In some cases the lead or other low melting point metal or alloy when molten may be allowed to remain in the mould and may even be augmented by more lead or the like introduced into or already within the mould at the time of casting, as described in my applications for U. S. patents. Serial No. 551,769, filed July 18, 1931 and Serial 5 No. 575,628, filed November 17, 1931, or the low melting point metal may be permitted when fused to flow out of the mould through a suitable outlet or into spaces provided in the mould or in the core into which the metal to be cast does not penetrate. If this low melting point metal is of greater density than the segmental blocks 6, it will tend to fioat the, blocks unless this is otherwise prevented. In the arrangement shown in Fig. 1, the central pillar 5 may be provided with means for retaining the segmental blocks in position. One such suitable arrangement comprises a collar fitting over the upper end of the pillar 5 and held in position against the top of the core by means of a cotter passing through the pillar.

In the arrangement shown in Fig. 2 a hollow central pillar 5 is provided and the segmental blocks 6 are held in position by lead or other low melting point metal or alloy '7 until it becomes molten.

spaced apart so that between adjacent blocks, a

gap 8 is left of insufiicient width for the metal being cast to enter and prevent the collapse or movement inwards of the blocks. A wider gap 8 may be employed provided that the gap is filled with a. low melting point metal or alloy. In such an arrangement the face of the low melting point metal or alloy exposed to the cast metal must be dressed with a suitable material to pro- 85 tect it from the immediate heating and dissolving action of the cast metal when contact is first made. In the casting of steel for example, a gap 8 having a width of 6th of an. inch will not permit any appreciable entry of the metal during 40 casting. The side faces of the blocks are formed 'With grooves of approximately semi-circular cross-section which, when the blocks 6 are assembled, provide a substantially cylindrical recess which is filled with low melting point metal 46 or alloy 9.

In forming the core, the metal or alloy is cast into each separate ring of blocks to form unitary annular elements. The cylindrical portions. 9 thus serve to register the segmental blocks 6 60 and hold them in position. By constructing the recesses between the segmental blocks so that the diameter thereof varies throughout its length, for example so that the. diameter increases towards the centre of the blocks as shown in Figs. 7 and 8, or so that one or more local enlargements are provided in the groove, a keyed construction of core ring is obtained which remains as a unitary construction during transit and erection, there being no tendency for the blocks to slide relatively to one another.

One convenient method of constructing a core ring of this type consists in spacing a ring of blocks 6 as a mould, concentric with a core corresponding to the pillar 5 but somewhat larger 68" in diameter, so that, after allowing for contraction, such a core section may be passed freely over the pillar 5. Low melting point metal or alloy is then cast into the space between the ring of blocks 6 and the core thereby uniting the 70 blocks and forming a unitary core ring for the mould The mould core may then be built up by superposing a number of such rings. On the top of the core, as shown in Fig. 1 is disposed a refractory head 10. In building up the core 76 of such sections,-thin intervening layers or rings The segmental blocks 6 are 26 of low melting point metal or alloy may be disposed between adjacent sections. This construction permits longitudinal contraction of the core to accompanying the cooling of the ingot.

In the method of supporting core sections 6 as represented in Fig. 3, connecting pieces or members 11 of low melting point metal or alloy are employed. In this arrangement the 'pillar 5 is formed with a number of axial grooves or castellations 12 of the cross-section shown, and the connecting pieces are in the form of strips or bars of low melting point metal or alloy having a cross-section as shown, with an enlargement 13 between the two enlarged endswhich serve to space the blocks 6 from the pillar 5 in addition to the spacing provided by the end enlargements.

The supplementary spacing action provided by these enlargements 13 continues some time after the enlargements 11 have melted. Low melting point metal or alloy may alternatively occupy the whole of the space 15 between the blocks 6 and the core 5.

In the arrangement of core shown in Fig. 4, the outer segmental pieces .6 are of substantially T cross-section, each of said tpieces having an enlargement 18 at the end of the central limb 16. The parts 16 and 18 engage with a T groove 17 in the central pillar 5, the segmental pieces 6 being spaced from the pillar 5 by low melting point metal or alloy in the form of strips 15.

Fig. 5 shows a further arrangement wherein the segmental pieces 6 are held in relation to the pillar 5 by connecting members 19 of low melting point metal or alloy. The connectors 19 are made from metal strips'which register with bulb ended grooves 12 in the pillar 5, being keyed therein by cores 14 of low melting point metal or alloyor of other metal, such as iron or steel in the form of rods. Rods 20 perform a similar function, the segmental pieces 6 being 115 spaced'from the pillar 5 by low meltingpoint metal or alloy 15.

Fig. 6 represents a mould for a hollow cylin drical casting or ingot which is closed or solid at its upper end. The pillar 5 is flanged at its lower end whereby it is bolted to the base 1 of the mould by means of bolts 21. The bolt heads are covered over by a plate 22 which supports the rings of segmental blocks 6 constituting the compressible core. mounted a hemispherical end comprising a base plate 23 of sheet metal, such as sheet steel, and a sheet metal hemispherical portion 24 suitably attached thereto. The space between these parts is filled with a low melting point metal or alloy 330 which maybe cast in before the base and hemispherical portions are joined. Suitable venting arrangements may be provided. In the construction shown, a vent tube 25 leads from the interior of the hemispherical end near the container wall to the outside. In the arrangement shown in Fig. 6 this vent leads to the space between the segmental pieces 6 in the upper core ring and the pillar 5. The vent tube prevents the development of excessive pressure within the conr40 tainer by allowing any molten metal within the At the top of the core is 125 1. A mould core comprising metal parts which will not melt at the highest temperature to which the core is subjected, spaced apart by metal parts of a comparatively low melting point. i

2. A mould core for use with a mould in the production of hollow metal castings, said mould core comprising metal parts which will not melt at the highest temperature to which the core is subjected, and metal parts of a comparatively low melting point maintaining said metal parts in spaced relationship, said composite core having spaces adapted to receive the low melting point metal parts of the core when liquefied and permit other metal parts to move relatively to each other to reduce the cross-sectional dimensions of the core.

3. A compressible metal mold core comprising a steel column, a plurality of superposed annular steel parts disposed around said colunm and lead parts holding said steel parts in spaced relation.

4. A mould core for use in a mould for the production of hollow metal castings comprising castiron segmental blocks assembled around a steel column and spaced radially therefrom and circumferentially in relation to each other, by lead distance pieces.

5. A mould core comprising a central pillar, a plurality of superposed annular elements each comprising a plurality of segmental blocks, and lead key pieces retaining said segmental blocks in circumferential relationship around said central pillar.

6. A mould core structure comprising a central pillar surrounded by segmental blocks arranged circularly, and superposed one above the other,

the whole structure being united by a lead filling occupying the interstices between the parts.

.7. A mould core structure, comprising a central pillar and a plurality of ring elements superposed around said central pillar, each ring element comprising a plurality of segmental cast-iron blocks and lead elements binding said blocks together in spaced relationship.

8. A mould core structure comprising a central pillar a plurality of core annular elements superposed around said central pillar, and rings of lead separating said annular elements from one another.

9. A compressible mould core comprising a steel column provided with longitudinal T-shaped slots, a plurality of T-shaped segmental pieces slidably fitting said T-slots and spaced from one another and from the column by lead distance pieces.

10. A mould core comprising a cylindrical steel column having longitudinally bulb-sectioned grooves therein, and. segmental steel blocks provided with longitudinal key-ways held in spaced relationship around and radially from said column by lead keys engaging said key-ways and we said bulb-sectioned grooves.

11. A compressible mould core comprising a central pillar and a plurality of ring elements superposed around said pillar, each of said ring elements constructed of a plurality of spaced seg- 195 mental blocks interlocked by lead keys fitting corresponding grooves longitudinally cut in the radial surfaces of the blocks and varying in width throughout their length.

12. A compressible mould core comprising an steel cylindrical column surrounded by a plurality of superposed ring elements of steel segmental pieces held in spaced relationship by lead distance pieces, and surmounted by a hemispherical cap of sheet metal enclosing a hemispherical mass of lead.

I RICHARD WILLIAM BAILEY.

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