US2530854A - Casting apparatus - Google Patents

Description

J. B. BRENNAN CASTING APPARATUS Filed March 19, 1946 INVHVTOR.

JOSEPH B.BRENNAN ATTORNEYS Nov. 21, 1950 Patented Nov. 21, 1950 UNITED STATES PATENT OFFICE CASTING APPARATUS Joseph B. Brennan, Cleveland, Ohio Application March 19, 1946, Serial No. 655,511

2 Claims. I

This invention relates to the making of metallic Wire, rod, strip and the like and particularly to the formation of metals into such shapes directly from the molten metal.

Wire, rod, strip and the like are ordinarily produced by expensive and relatively slow rolling or drawing processes or in the case of rods and some of the soft metals by extrusion at extremely high pressures through dies. Both types of processes require very expensive equipment and the many operations required add greatly to the cost of the finished product. It is the general object of my invention to provide a method and apparatus for making such shapes wherein the shapes are formed directly from the molten metal thus eliminating the many rolling and drawing steps or the expensive extruding operation heretofore required.

Briefly, a preferred form of my invention comprises a crucible heated by electricity or by other means within a pressure chamber such crucible and pressure chamber being preferably of the type disclosed in my Patent 2,371,604, issued March 20, 1945, wherein molten metal contained within a crucible is forced under pressure through a passageway the temperature of which passageway can be controlled with a reasonable degree of accuracy. The passageway terminates in a cooling zone wherein the metal is solidified, the passage through the cooling zone being of a shape to form the molten metal into the desired figuration. This cooling zone as distinguished from an ordinary extrusion die is of considerable length with the result that the metal enters into the cooling zone while molten and while still in the molten state is caused to assume the desired cross-sectional shape. As the metal moves along it is gradually cooled becoming plastic and then solid before its discharge. Preferably, substantial pressures are employed in order to improve the character of the metal produced by my method but these pressures are far below those required for the usual extrusion processes. To avoid interruption of the operation of the apparatus a pressure trap is provided for charging the crucible with molten metal.

My method in one sense may be considered-as a continuous pressure casting method wherein the molten metal may be continuously fed into a mold, permitted to solidify in the mold and the solidified metal continuously withdrawn therefrom. The method is especially adapted for the production of wire, the production of rods having shapes similar to shapes produced by present day extrusion methods, the production of tubing, and

the production of strip. My method contemplates that in the manufacture of material designed for some services it will be desirable to subject the wire, rod, tubing or strip produced to further mechanical reduction as by rolling or drawing particularly in instances where it is important to have high strength in the ultimate product or where very fine wires or thin strips are desired. However, for many purposes my method will produce metal suitable for use without further treatment.

It is one principal object of my invention to provide an apparatus capable of pressure working and densifying a metal while in motion and at the same time insuring that the metal so worked will continuously issue from such apparatus in the form of wire, rod, tubing or strip of uniform size and shape.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

In the drawings, Figure 1 is a central vertical cross-section through a preferred form of apparatus illustrating such apparatus in somewhat diagrammatic form and Figure 2 is an enlarged longitudinal cross-section view of the cooling zone through which the metal flows and in which the metal solidifies prior to emergence therefrom.

A preferred form of apparatus may include a pressure chamber and crucible constructed generally in accordance with my Patent 2,371,604 aforesaid, and preferably comprising a cylindrical pressure chamber l0 having a bottom portion II and a top closure member l2 securely bolted thereto as by bolts l4 and I5 respectively, gaskets I6 and I! being employed to provide tight joints.

The molten metal to be discharged under pressure is contained in a crucible indicated generally at l8 and supported within the pressure chamber in any convenient manner as by rails l9 resting on upstanding bosses 20 extending from the bottom member ll of the chamber. The crucible is provided with a lining 2| of refractory material which is preferably selected so that it will have little if any damaging effect upon the quality of the metal even though it may be dissolved therein to a slight extent. For example, in conjunction with the melting of aluminum, a lining of aluminum oxide is preferred. A conduit 22 also including a refractory liner communicates with the open bottom end of the crucible and with the cooling chamber 23 where the casting process takes place.

The crucible may be heated by any convenient means such as by induction heating or the resistance heating coils indicated diagrammatically at 24. To control the temperature of the metal during its passage through the discharge conduit 22 separate heating coils 25 and 26 are employed. Preferably, the heating current for these coils is independently controllable so that the temperature of the crucible, the temperature of the initial portion of the discharge conduit and the temperature of the end portion of the discharge conduit may be individually controlled and maintained at the desired temperatures. The heating effect of the several coils may be regulated by means of conventional rheostats or other similar devices not shown.

While the metal may be melted in the crucible it is more convenient to melt the metal in another furnace and supply the molten metal to the crucible so that the crucible can be intermittently charged with molten metal without interrupting the discharge of metal under pressure therefrom. To this end, I have provided the charging mechanism associated with the upper portion of the pressure chamber which is not herein shown but which is fully disclosed in my aforesaid patent. For the present, let it suiilce to say that when the crucible l8 has been filled with molten metal the charging valve 21 may be closed and gas under pressure admitted into the pressure chamber surrounding the crucible by opening a valve 29. After such has been once done, the aforesaid charging mechanism permits recharging of the crucible without releasing the gas pressure within the pressure chamber and by this means molten metal may be discharged continuously from the crucible without the necessity of interrupting the operation in order to replenish the supply of metal within the crucible.

The metal under pressure is discharged through the conduit 22 into the discharge zone indicated generally at 33. It is in this zone that the metal is given its desired shape and where the solidification takes place. This may be termed thecooling, casting or extruding unit and comprises a passageway or die 29 which has the cross-sectional shape for a portion of its length of the ultimate product, in the present example, a round wire being illustrated and which is provided with a flared portion 30 of taper preferably corresponding to the rate of shrinkage of the metal as it cools in passing therethrough. The temperature of the passage 29, 30 is controlled by a bath of a molten material having a melting point suitable for the purpose. In con- Junction with the production of aluminum wire, I prefer to employ a bath of molten lead indicated at 3|; the lead being heated by a, suitable electric heating coil 32. The molten lead provides a means for accurately controlling the temperature in the cooling zone and avoiding abrupt changes in temperature. By this means, the temperature can be controlled and correlated with the speed of discharge so that the molten metal flowing through the passage will congeal and become plastic and then solid after it has been given the desired cross-sectional shape but before it is discharged from the end of the pas- It will now be evident that when the molten metal is forced through conduit 22 into passageway 29, 30 the metal as it flows through the flared portion 30 will gradually cool and because the taper of such flared portion is in accord with the rate of shrinkage of the metal as it cools, the velocity of the metal at any section longitudinally along the flared portion 30 will be constant. In this way the acceleration of the particles of the metal relative to one another will be minimum and therefore such particles will be compacted together to densify the metal while the metal is in motion. By the time the metal reaches the straight portion 29 it has cooled to an extent such that the outer skin thereof is solid although still somewhat plastic but the core thereof will yet be molten whereby such molten core being under pressure will expand such outer shell against the straight section of the passage 29. In this way, the wire, rod, strip and the like so formed is accurately maintained to size. Thus, the only difference in size between the final product and the size of the passage 29 will be what little shrinkage occurs in the cooling of the metal from the temperature of the solid condition at the region 33 in passage 29 to room temperature. In my method and apparatus I prefer the wire, rod, or strip or the like besolid throughout its cross-section prior to emergence from the cooling zone whereby shrinkage is minimized and such final product as it issues from the passage 29 will much better hold its shape and can be handled without danger of distorting the same. In Figure 2 the metal in molten condition is indicated by the horizontal dash lines 34 and in solid condition by the inclined uniformly spaced section lines 35. As shown in Figure 2 the metal is completely solidified throughout its cross-section prior to emergence from the cooling zone.

In operation the pressure within the pressure chamber must be correlated with the cross-section, size and shape of the passagewa 29, 30 so that the metal will be forced through at the desired speed; likewise the speed of the metal and the temperature and length of the passageway must be correlated so that the metal will be properly cooled and emerge from said passage in a solid condition.

While I have shown but one form of apparatus for applying pressure to molten metal, it is to be understood that other types of apparatus may be used with equal facility as for example, a pump may be directly connected to the conduit 22 or a reservoir containing molten metal may be placed well above the passageway 29, 30 so that the head of metal will give the desired pressure.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In apparatus for making elongated metal articles, the combination of an elongated die aas ezm articles, the combination of an elongated die formed with a passage therethrough including contiguous portions of tapered and uniform cross-section, the smallend of such tapered portion joining such uniform portion between the ends of said die, means connected to said die operative to force molten metal through such passage from the large end of such tapered portion, cooling means on said die surrounding such passage having a heat transfer capacity such that a partially solidified skin is formed on the metal when it reaches the juncture of such tapered and uniform portions whereby as the metal flows through such uniform portion the pressure in the molten core retains the skin in 6 engagement with the wall of such uniform portion and that the entire cross-section of themetal is solidified prior to its emergence from said die. such tapered portion being of taper corresponding with the rate of shrink of the metal as it is forced through said die and cooled thereby.

JOSEPH B. BRENNAN.

REFERENGES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 770,130 Trotz Sept. 13, 1904 2,128,943 Hudson Sept. 6, 1938 2,131,307 Behrendt Sept. 27, 1938 2,26%288 Betterton et al Dec. 2, 1941 2,363,695 Ruppik Nov. 28, 1944 2,371,604 Brennan Mar. 20, 1945 FOREIGN PATENTS Number Country Date 14,078 Great Britain July 21, 1894

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