US2912728A

US2912728A - Casting method and apparatus

Info

Publication number: US2912728A
Application number: US565372A
Authority: US
Inventors: Edmund Q Sylvester
Original assignee: Griffin Wheel Co Inc
Current assignee: Griffin Wheel Co Inc
Priority date: 1956-02-14
Filing date: 1956-02-14
Publication date: 1959-11-17
Anticipated expiration: 1976-11-17
Also published as: BE560855A; FR1185661A; GB856208A

Description

Nov. 17, 1959 Q. SYLVESTER CASTING METHOD AND APPARATUS Filed Feb. 14, 1956 IIIIHHH 'M, ll

INVENTOR.

United States Patent CASTING METHOD AND APPARATUS Edmund Q. Sylvester, Lake Forest, 11]., assignor, by mesne assignments, to Grilfin Wheel Company, Chicago, Ill.,

a corporation of Delaware Application February 14, 195.6, Serial No. 565,372

2 Claims. (Cl. 22-69) This invention relates to the casting of metal and more particularly to the casting of wheels by forcing molten metal such as steel under pressure into a mold. The present application is a continuation-in-part of my copending applications Serial No. 236,324, filed July 12, 1951, now Patent No. 2,738,370,.and No. 299,071, filed July 16, 1952,.now abandoned.

An object of the invention is to prevent slag from forming in a pouring tube which is lowered into a ladle of the molten metal to afford passage to the mold gate.

Another object of the invention is to prevent solidification of the molten metal in the tube under certain conditions by subjecting the chamber containing the ladle to sub-atmospheric pressure until the metal in the tube is lowered to the bottom thereof.

Still another object of the invention is to remove entrapped and absorbed gases fromthe molten metal in a ladle by subjecting such molten metal to sub-atmospheric pressure prior to pouring of themetal into a mold.

A further object of the invention is to minimize the breaking stresses imposed upon a pouring tube during the introduction of such tube into a ladle of molten metal and while the tube is held therein for the pouring of molten metal therethrough into an associated tilted mold.

The foregoing and other objects and advantages of the invention will become apparent from a consideration of the following specification and accompanying drawing, the latter being a central vertical sectional view of a novel apparatus by which the invention may be practiced.

Describing the invention in detail, the casting apparatus comprises a mold generally designated 2, said mold being described in the above mentioned copending application No. 236,324. The mold comprises a cope 4 and a drag 6 defining a casting cavity 3, preferably in the form of a standard freight car wheel as illustrated, said cavity comprising a hub section .10 conforming to the hub of a wheel. The cope 4 also comprises a riser cavity 12 open to the atmosphere and communicating with the cavity 8 at the highest point thereof for a purpose hereinafter described.

The drag 6 comprises a gate 14 extending linearly from the hub section 14) of the mold cavity dorwnwardly to the bottom of the drag which is seated on the upper surface of a flange 16 on the upper end of a pouring tube 18. The flange 16 is mated with the drag 6 along upwardly tapering surfaces at 243 which are preferably conical.

The mold may be formed of any suitable material having self-sustaining properties, for example, carbon or copper. It is preferred to use a mold constituted of preformed refractory blocks of non-metallic material, such as graphite.

The tube 18 is described in copending application No. 236,324 and is diagrammatically illustrated in the drawing, said tube extending through a complementary sealed opening of a cover 22 supporting a tapered ring 24 which is preferably positioned between the flange 16 and the cover 22 although it will be understood that, if desired,

2. the flange 16 and ring 24 may be formed as a single integral structure. I

As mentioned in said copending application No. 236,- 324, the tube 18 may be formed of segments of ceramic tubing, bonded end to end, and surrounded by a tube of baked ceramic material, such as foundry sand containing a phenolresin binder. The latter tube is surrounded by a steel tube which supports a layer of wire mesh around which is a layer of high temperature cement. This con- .Struction of the tube 18 is necessitated by the high repeated or continuous temperatures that it must withstand during immersion into the molten metal, and as a result the tube 18 is frangible and must be handled with care.

The gate 14 is inclined with respect to the vertical and the tube 18 is vertically positioned so that an internal passage 25 of the tube communicates with the gate 14. As illustrated, when the mold drag 6 is mated with the flange 16, the mold 2 is automatically tilted so that the riser 12 is positioned at the highest point of the casting cavity 8.

The tube 1 8 is introduced and immersed in abath 26 of molten metal suchv as steel or other molten material within a ladle 28. Introduction of the tube into the metal is accomplished by maintaining the tube vertical while lowering same into said metal. In this fashion, bending forces which could crack the tube are avoided. Likewise, the tube is maintained in a vertical position While immersed in the molten metal, so that buoyancy forces exerted by the metal upon the tube are transformed into compressive stresses which the tube is best able to withstand. The bottom of the ladle is preferably provided with a well 3b to accommodate the end of the pouring tube 18 without excessive waste of the molten metal 26. The ladle is preferably provided with feet 32 and is positioned centrally of a chamber 35 by a plurality of ribs 34 therein. The cover 22 is preferably provided with an insulation pad 36 above the ladle 28 and is seated on an annular resilient sealing gasket 37 affording a substantially air-tight seal between the chamber 35 and the cover 22. The cover is releaseably clamped against the gasket 37 by conventional clamps 38.

In pouring a casting, the ladle 28, filled with molten metal, is lowered into the chamber 35 as by a crane (not shown), and the cover 22 with the tube 18 assembled therewith is lowered to the position shown. At this point in the cycle, the chamber 35 is subjected to a vacuum by reducing pressure in line 40 to subatmospheric value at which the metal in the tube 25 is lowered. The pressure in line 40 and chamber 35 may be held constantat said subatmospheric value to avoid drawing air from the tube passage 25 through the molten metal 26, or it may be varied to keep the metal moving up and down in the tube to prevent solidification of the metal in the tube while still avoiding the drawing of air from the tube through the molten metal 26.

With the tube passage 25 cleared of the molten metal, either by depressing the level of the metal in the tube or by keeping the metal in motion by alternating the pressure and thus preventing any possibility of said metal solidifying in the tube, the cover 22 is clamped by the clamps 38. it may be noted that this clamping of the cover 22 is facilitated by the fact that subatmospheric pressure in the chamber 35 has caused the cover 22 to compress the gasket 37; however, if .desired, the cover 22 may be clamped prior to lowering of pressure in the chamber 35.

Reduction of pressure within the chamber 35 also serves to degassify the molten metal in the ladle by removing entrapped gas bubbles and absorbed gases from said metal. By placing a gas tight cover over the top of the pouring tube, the pressure in the tank may be further reduced to degassify the molten metal in the ladle by .Patented Nov. 1 7, 1 955 removing entrapped gas and absorbed gases from said metal.

After the vacuum refining treatment is completed, if such a treatment is used, and all of the equipment is in the pouring position, the vacuum in the tank is raised to atmospheric pressure. The chamber 35 is then subjected to superatmospheric pressure of a magnitude sufficient to force the molten metal 26 through the tube passage and gate 14 into the mold cavity 8. As the mold cavity is filled with said molten metal all air in the mold cavity is forced by the metal to the opening 12 which is at the highest point of the mold cavity to accommodate escape of the air to the atmosphere.

When the mold cavity 8 has been filled and the riser opening 12 has almost been filled, a plunger 42 is actuated by any convenient means such as those described in copending application No. 236,324 to a closed position of said plunger whereat a seat 44 of the plunger mates with a complementary seat 46 at the upper end of the gate 14 to close the gate, whereupon pressure in the chamber is exhausted to atmospheric pressure.

The mold 2 may then be removed and another mold 2 may be positioned with its gate 14 in communication with the tube passage 25 as shown in Figure 1. If desired, the chamber 35 may be subjected to a vacuum as above described to depress the molten metal level in the tube passage 25 after each moldhas been poured; however, ordinarily this is not necessary after the first mold has been poured because of residual heat in the tube, because the molds subsequent to the first mold are preferably poured in rapid succession and because subsequent degassification may not be necessary. If any delay is encountered between molds, as, for example, to make minor mechanical repairs, the chamber 35 is preferably evacuated to depress the molten metal level in the tube passage 25 and to maintain the metal in degassified condition as heretofore described.

It may be noted that the distance shown between the plunger seat 44 and the gate seat 46 when the plunger is in open position as illustrated, is substantially less than the distance between the plunger seat and the upper surface 48 of the hub section 10 of the mold cavity 8. This arrangement reduces to a minimum the pumping action of the plunger 42 on the molten metal within the mold cavity 8 to minimize any tendency of the molten metal to be forced out of the riser opening 12 as the plunger 42 is actuated from its open position to closed position, whereat the seats 44 and 46 are mated to close the gate 14.

It may also be noted in this connection that although only one riser opening is illustrated in the drawing, preferably a plurality of such riser openings are utilized d], as, for example, three of such openings equidistantly spaced for each other around the longitudinal axis of the plunger 42.

It will be understood that the arrangement of the mold 2 and tube 18 as well as the arrangement of the plunger 42 may be utilized in a system wherein the molten metal 26 is poured into the casting cavity 8 by other means than a pressure system such as above described as, for example, by means of a vacuum system connected to the cavity 8.

I claim:

1. A method of casting comprising the steps of mating the gate of a mold with the exposed end of a pouring tube immersed in molten metal located in a sealed chamber, positioning a stopper with a downwardly facing seat within the casting cavity of the mold so that the mating seats of the stopper and gate are spaced from each other a distance less than the distance between the stopper seat and the overlying mold surface, developing subatmospheric pressure in the chamber to depress the level of the metal in the tube, and then developing superatmospheric pressure to force the metal through the tube into the mold until said cavity is filled, followed by moving the stopper to interengage said seats to cut oif communication between the cavity and the tube.

2. Casting apparatus comprising a sealed chamber, a molten metal ladle within such chamber, an air space between such ladle and the walls of the chamber, a pouring tube vertically extending through the cover of the chamber and into said ladle, means for developing subatmospheric and superatmospheric pressures in said chamber, a mold seated in tilted position with respect to the horizontal upon the end of the tube remote from the ladle so as to be readily removable and replaceable by an empty mold, said mold having a casting cavity with a gate in communication with said tube, having a riser opening connected to a high point of said cavity and having a plunger for effecting closure of the gate and thereby terminating flow of metal into the casting cavity.

References (Iited' in the file of this patent UNITED STATES PATENTS 969,539 Kitchen Sept. 6, 1910 1,026,733 De Buigne May 21, 1912 1,029,565 Wetherill et al June 11, 1912 1,153,220 Grey Sept. 14, 1915 1,360,655 Lukomski Nov. 30, 1920 1,599,624 Stern Sept. 14, 1926 1,913,945 Morris et a1 June 13, 1933 2,018,586 Wetherill et 'al Oct. 22, 1935 2,082,588 Menetrey June 1, 1937 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,912,728 November 17, 1959 Edmund Q. Sylvester It is hereby certified that error appears in the -printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 20, for "Patent N00 2,738,370" read Patent No, 2,8A7f/39 column 4, line 2, for "spaced for" read spaced from Signed and sealed this 24th day of May 1960.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Commissioner of Patents Attesting Oflicer