US3010166A - Mold for casting operations - Google Patents

Description

Nov. 28, 1961 J. H. s. SKONING 3,0 0,1

MOLD FOR CASTING OPERATIONS Filed Aug 4, 1958 3 Sheets-Sheet l I mam... 12

ATTORNEY Nov. 28, 1961 J. H. s. SKONING 3,010,166

. MOLD FOR CASTING OPERATIONS Filed Aug. 4, 1958 3 Sheets-Sheet 2 Ja /V 11; 6; ko/w/ve INVENTOR.

Nov. 28, 1961 J. H. s. SKONING MOLD FOR CASTING OPERATIONS 5 Sheets-Sheet 3 Filed Aug. 4, 1958 da /v E 5. SKON/NG,

INVENTOR.

United States Patent 3,010,166 MOLD FOR CASTING OPERATIONS John H. S. Skoning, 6310 Rodgerton Drive, Los Angeles 28, Calif. Filed Aug. 4, 1958, Ser. No. 753,000 7 Claims. (Cl. 22-193) This invention relates to an improved mold for casting of metals, and to the process of producing such mold.

The invention more particularly relates to the means for and method of precision casting of metals.

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' fidelity master pattern P, including the gating system An object of my invention is to provide a new and novel type of mold for thecasting ofmetals, which mold enables a foundry to obtain a casting therefrom of accurate dimensional precision and high finish with great sav-v ings in the use of the mold body materials, as well as expediency of time in the casting art.

Another object is to provide a novel mold for precision metal casting whereby the time heretofore required for firing the mold is reduced to a A further object is to provide a novel mold whereby dimensional accuracy of the cast object may be controlled, and likelihood of cracks in the molded or cast object is eliminated. g

A still further object is to provide a novel inorganic shell mold which will not pick up carbon or foreign material during the casting process, and in which the back-up material may be used repeatedly, and whereby the time of firing the mold may be materially reduced.

Other objects, advantages and features of invention may appear from the accompanying drawings, the subjoined detailed description, and the appended claims.

The accompanying drawings are intended to disclose in a simple form, the manner and method of compositionally building up a mold for the precision casting of metals in accordance with my invention, and in a form I at present deem preferable, and in which:

FIGURE 1 is a longitudinal sectional view of a drag member and one half of a master pattern supported on a plate, with the pattern overlaid with a coating of covering material;

FIGURE 2 is a view analogous to FIGURE 1, but with back-up material tamped against the overlaid material, and with the pattern portion removed;

FIGURE 3 is a longitudinal sectional view of the apparatus after removal of the coating covering material from the flask and after locating the pre-fired monolithic back-up material on the pattern, illustrating the space formed between the pattern and said back-up material by the removal of the coating covering; 7

FIGURE 4 is a longitudinal sectional view of the apparatus illustrating the space between the said pattern portion and the back-up material as filled with slurry;

FIGURE 5 is a longitudinal sectional view illustrating the relative position of a core spaced from the slurry after setting thereof;

FIGURE 6 is a longitudinal sectional view of thecope half of the mold as produced in accordance with the present invention;

FIGURE 7 is a longitudinal sectional view of the assembled mold, including the core, ready for metal pour- FIGURE 8 is a top plan view thereof; and

FIGURE 9 is a side elevational view of one form of casting formed by the process and apparatus of the present invention. '1'

For purposes of illustration and ease of description of my novel mold and method for casting operations, I have selected apattern configuration whioh is-r'elatively simple as a casting. The apparatus embodies a core" -1 -,"-a drag. 2 and a cope 3. Thepattern P is' preferably-"a high fidelity pattern, either mounted'on a matchplate"4,' 4'

and registration means, to an extent of approximately to /2 inch, with a material that will, when hardened, be sufficiently firm to withstand the ramming of sand or asuitable .back-up material, as shown in FIG. 1. Such a 'material may be a calcium sulphate type of plaster, or a cast resinous type compound material, and the extent of the thickness thereof over the pattern parts is obviously optional to those versed in the art.

In the event calcium sulphate is used for a pattern covering material, the master pattern portions should have applied thereto a suitable .parting material, such as petroleum jelly or other suitable parting material. The exterior of this plaster cast is coated with a suitable material, such as ordinary orange shellac which acts to prevent the back-up material from adhering to the plaster covering material,

A flask' 5, 5 is then placed around the coated high fidelity pattern, and a down gate 6, and riser 6' for slurry pour is provided; and tile 7', 8 is placed in proper position to provide for a downga-te 7 and a riser 8 for metal pour. In the event that tile is not employed, an oversize, loose piece (not shown) is used, allowing to inch of clearance for slurry pour (in a manner similar to the material covering the pattern) so as to provide a space for slurry to line the down gates and risers.

The mold is now, in a conventional manner, rammed up with a back-up material 9, 9' preferablyhaving the characteristics of the refractory material described and claimed in my eo-pending application filed December 6, 1957, Serial Number 700,976. I

The pattern and the loose pieces forming the down gate and riser passageways are then withdrawn, and the calcium sulphate covering materialis then removed by stripping the same from the rammed back-up material, leaving voids in such rammed back-up. In the event that a snap flask is employed, the rammed back-up material is laid on a suitable refractory slab and placed in a kiln where it is fired to approximately 1500 F. to 1800 F. to suitably cure such monolithic back-up shape. A similar procedure is followed in the drag piece of the mold; and such monolithic back-up shapes are allowed (after firing) to cool to room temperature. I p

The fired and cooled monolithic back-up shapes thus formed are then placed upon the high fidelity pattern, as shown in FIG. 3, and which pattern after its previous removal from the rammed hack-up material has been thoroughly cleaned and properly lubricated, forms a void a between the said fired back-up material and the pat tern P to receive the'slurry pourlll, 10 in the void a which was occasioned by removal-of the calcium sulphate covering material; f The calcium sulphate plaster material is preferably removed as a unit'-or in one piecefand it may then be subsequently placed in another flask, and reused to sup port-the back-up mate'nial'that' is again rammed against the plaster element, -theremova1 of which forms the void toreceive'the s-lurrypour' 10, 10 after the back-up materiallias beenfired, i V 1 "The slurry 10, 10 maybe of any suitable orthosilicate bonded 'high refractorybodied material, or a'phosphate bonded material of a similar nature, or of any'other material'fgenenally known" to those skilled in the art adaptable for 'useasslurr'yf Such slurry is then poured,

the ing'ate '6 (FIG. 8)": It will be noted that when the 3 mold is entirely filled with this slurry, as in FIG. 4, that the slurry will rise in the riser slurry gate 6'; thereby to indicate that the void between the pattern and the rammed back-up and fired monolithic shape or material 9, 9', defined by removal of the calcium sulphate covering material (shown in FIG. 3), has been filled.

The slurry material is preferably so accelerated (with suitable materials known in the art) that a firm gelatin, or set, of the slurry will be accomplished in the matter of a minute, or a fraction thereof, and when the slurry has se the mold is ready to be stripped. The molds should be carefully stripped on some suitable stripping device, so as not to damage the slurry face by a possible irregular or non-tangential extraction.

In the event an onthosilicate type of slurry is utilized, the alcohol contained therein is immediately ignited, so as to burn off any excess alcohol and thereby eliminate cracking which may result from normal evaporation.

By igniting the alcohol in the set slurry immediately after it has been removed, as above described, the gelatin or set of the slurry is accelerated and a very fine craze finish is induced on the slurry gelatin. Such craze finish materially enhances permeability.

The cope and drag flasks 5 respectively are then assembled, as shown in FIG. 7, with the core member 1 in position and the mold parts are maintained in proper register with each other by such registration means, preferably shown as a dowel 11 and a cavity 12 at each corner of the mold parts. The mold is now placed in a kiln and fired to approximately l500 F. to final cure. The composite mold can be poured hot or after being cooled to room temperature, and is now ready to receive the molten metal in the down-gate 7 to fill the cavity 13 to form the casting 14 shown in FIG. 9.

After a sufficient quantity of metal has been poured, the metal casting 1'4 and its gating system frozen, the mold is carefully separated. The tile in the downgates and risers, and/or the slurry formed downgate and risers, whichever are used, permits the ready extraction of the casting 14 from the mold, without damage to the mold, providing however, there is formed no mushroom head on the downgate or riser by pouring of an excess amount of molten metal.

The casting 14 may be easily and quickly removed from the readily friable slurry 10' which separates from the back-up material 9, 9' upon extraction of the casting 14 from the mold.

My novel mold may, in the main, be used over and over again in casting metal objects from the same pattern. In the event any slurry remains adhered to the back-up material after any one use, it may be readily removed by wire brushing or by a light sand blast. The slurry ingate and riser are cleaned out, and the fired back-up is replaced in the flask, in the event a snap fiask has been used; otherwise the fired back-up will still be adherent to its metal flask. The matchplates with the pattern portions thereon are placed in position, new slurry pour shapes are made, and the formed and fired back-up monolithic shapes are used over and over again, as in the process described above. v a

After multiple usage, deterioration or damage to the fired back-up monolithic shape, the material forming same may be crushed in a suitable hammer mill or crusher, screened, chemically bonded and again remolded. The material used in forming the back-up, in essence, becomes a fixed investment embodied in the process.

By the use of my novel composite mold, I obtain many advantages over molds heretofore used, and among which is that of dimensional stability or precision of the resultant casting. This I am able to obtain because the control of a relatively thin section of slurry is greatly enhanced over the attemptto control a thick section thereof; and on subsequent burn out of the mold, corner differential heating is reduced to a minimum.

By the use of a thin skin section of the slurry mern+ ber, I provide for permeability, employing the fine particle-size materials which results in an ultra-high finish on the casting metal. This obviously is not obtainable by the use of a thick mass of this type of slurry. The rammed up back-up monolithic shape, being formed of coarse grain size material, provides exceedingly high permeability of the mold.

Further, due to the inorganic nature of the slurry or facing material, it will not pick up carbon or foreign material during the casting process.

High economies in the casting of metal objects are obtained by the use of my novel process and composite mold, in that the greater bulk of my mold is formed of back-up material 9, 9 which after firing may be used again and again without further ramming or firing, and thereafter may be crushed, screened and chemically bonded for use as it was initially.

This re-use of the monolithic shape cuts down the kiln time of firing the mold for subsequent usage, because initially approximately 10 hours or a longer period of time is required to fire and cure the back-up material because of the massiveness thereof, while by the use of my invention only a small surface and thin skin of slurry is required to be cured, this taking much less time.

Emissivity, or heat exchange, for rapid chilling of certain casting bodies that call for chill effect to produce a fine grain are obtained by employing in the ram up back-up monolithic, various materials, such as stainless steel shot, grain properly sized silicon carbide, boron carbide, or like dense bodied materials that have a high convection of heat. As indicated, to those versed in the art, this composite mold is not intended entirely to be directedat the multiplicity of chemical constituents involved, but is more directed at a composite build up of a mold body directed at specific prescription to meet a given requirement. These molds obviously can be poured at high mold temperature in the nature of the conventional 1500 F. to 1800 F., or they can be cooled to room temperature and poured, which in the general run of ferric alloys produces a better grain structure and characteristically higher physicals.

I claim:

1. A method of making precision castings in a cavity defined by spaced apart cope and drag portions of a mold which method consists of applying to each portion of a master pattern a relatively thin coating of a covering material which, when hardened, is configured on one side to conform precisely to the outline of the pattern and is sufficiently firm to withstand the ramming of a backup material thereagainst; stripping the conformed covering material from each of the said pattern portions, and placing the configured covering materials in a flask; ramming back-up material around the covering material; removing the covering material; firing the back-up material; replacing the fired back-up material on the pattern whereby a space is defined by the removed covering material, filling said space with a slurry material; removing the pattern; firing the slurry material with the back-up material locating the cope above the drag portion of the mold; and then filling the cavity between the fired slurry portions defined at least in part by the removed covering materials with molten metal to be cast.

2. A process as set forth in claim 1 in which the covering material is a calcium sulphate type of plaster.

3. A process as set forth in claim 1 in which the covering material is of a cast resinous type compound material.

4. A process as set forth in claim 1 in which the slurry material is an orthosilicate bonded high refractory bodied material.

5. A process as set forth in claim 1 in which the slurry material contains "alcohol and is accelerated to quickly set, andexcessalcohol therein is immediately burned off.

6'. A process as set forth in claim 1 in which the covering material is removed. as a unit, to form'a void in a body of rammed back-up material to accommodate a slurry materifi in such void.

7. A method of making precision castings from a master pattern which consists of applying to each portion of the master pattern a relatively thin coating of a covering material and thereafter hardening same, which portions when hardened, are sufficiently firm to Withstand the ramming of a back-up material thereagainst; stripping the hardened coating shapes from the pattern portions; then placing each of said coating 10 shapes in a flask; ramming a back-up material around each of said coating shapes, removing said coating shapes from the back-up material and firing the backup material; replacing the fired back-up material on the master pattern whereby a space is provided between each pattern portion and said back-up material portion corresponding to the volume previously occupied by the coating form shape, filling said space with a slurry material; removing the master pattern; firing the slurry material locating the cope and drag portions of the mold in a flask; and then filling the cavity between the fired slurry portions defined at least in part by the removed covering materials with the metal to be cast.

References Cited in the file of this patent UNITED STATES PATENTS 779,979 Walter Jan. 10, 1905 805,144 Kuller Nov. 21, 1905 2,303,092 Raphael Nov. 24, 1942 2,491,096 Feagin Dec. 13, 1949 2,734,243 Lips Feb. 14, 1956 2,873,493 Thomson et al. Feb. 17, 1959

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