US2843897A - Mold for the casting of non-ferrous alloys - Google Patents

Description

July 22, 1 958 A. F.BAUER ETAL 2,843,897

MOLD FOR THE CASTING oF NoN-FERRoUs ALLoYs Filed oct, 16, 1952 2 `:shams-sheet 1 INVENTOR FILFRED F. BQUER B CHARLES ACK l A I; l ATTCRNEY July 22, 1958 A. F. BAUER ETAL 1 uom 4FOR THE' CASTING oF NoN-FERRoUsALLoYs Filed oct. 1e, 1952 v n 2 Sheef,s sheet 2 w u e@ m www I HLFRED F. BQUER BY CHARLES ACK we f ATTQRNEY v United States MOLD FUR THE CASTENG @F NON-FERRUS ALYLYS Alfred F. Bauer and Charles Pack, Toledo, tibio, assignors, by mesne assignments, to National Lead Cornpany, New York, N. Y., a corporation of New Jersey Application October 16, 1952, Serial No. 315,128

7 Claims. (Cl. 22.-l29) This invention relates to the working of non-ferrous alloys in dies, and more particularly light metal alloys.

For certain purposes itis required that a piece be forged rather than die cast, because of improvement in characteristics obtained `by the forging operation. Aluminum will be discussed as a main example, but the invention is also applicable to magnesium, brass, bronze, and zinc. In the case of aluminum it has heretofore been necessary to use substantially pure aluminum. The slug to be forged has been cut from bar stock. This is costly, and in an emergency, bar stock becomes scarce. The forging operation has been carried out in a series of successive forging steps to bring the piece to final desired contiguration and dimension. The resulting product is relatively costly, and does not have the strength which it would have if it were possible to use aluminum alloys containing small amounts of other metals, typically copper and silicon.

The primary object of the present invention is to generally improve the production of non-ferrous forgings, and to overcome the foregoing dtliculties and disadvantages.

With this object in View it has been found possible to first cast the slug which is to be forged. This slug is heated to a desired forging temperature, and then forged in a single forging step tothe desired final configuration. The forging step is preferably performed in a fully enclosed die, by means of a plunger which is forced into the die cavity under enormous pressure. The parts are so arranged relative to the shape of the piece as to cause a substantial dow of metal which improves the strength of the forged piece.

In the Lforegoing process difficulty arises because of a wide variation in the strength of the finished pieces when tested. Variations as large as may be found despite precautions taken as to the uniformity of the alloy used.A In studying the matter it was found that there may be considerable difference in the grain size and character of the metal in the cast slug itself, even before reaching the forging step. It was further found that the differences in the slug could arise from a number of factors, such as the manual ladling ofthe molten metal into the open-topped die cavities, for in one case the ladle might contain a higher content of dross or impurities than in another. The top part, say one third, of the slug, may be cut olf, but this is a troublesome operation, and not always successful.

In accordance with the present invention, the slug is cast in a die having a constricted gate of substantial height above the die cavity. This gate may be made funnel-shaped for increase of Volume at the top, and in any event forms a space in which dross and impurities may collect Iby otation, thus insuring that the body of the slug itself contains pure alloy. lnasrnuch as the slugs are to be turned out in large quantity,` the die is preferably a permanent die which` may be used repeated-ly. However, further di'iculty then arises by reason of shrinkarrasar Patented July 252, 1958 age. The gate is preferably necked at the slug to facilitate severance, and this leads to solidification at the gate before the larger volume slug has solidified. The subsequent solidiiication of the slug may be accompanied by shrinkage and consequent change in characteristic of the metal.

In accordance with the present invention the die surfaces in contact with the slug are made of metal, but the die surfaces in contact with the gate are made of a refractory material of low heat conductivity. Thus the cooling of the gate is retarded relative to the cooling of the slug, and the metal in the gate is maintained in liquid condition so that it flows downward gravitationally to make up for any shrinkage at the slug, which then solidifies as a uniform solid body of metal.

To accomplish the foregoing general objects, and other more specific objects which will hereinafter appear, the invention resides in the casting and forging of non-ferrous alloys in dies, as hereinafter described in the following specication, and sought to be dened in the following claims. The specification is accompanied 'by drawings, in which:

Fig. 1 is a perspective view of a cast slug and gate as removed from the permanent die;

Figs. 2 and 3 are sections through a simplified die, with the die shown closed `in Fig. 2 and open in Fig. 3;

Fig. 4 is a plan View of a permanent die embodying features of my invention;

Fig. 5 is a section taken approximately in the plane of the line 5--5 of Fig. 4;

Fig. 6 is a transverse section taken approximately in the plane of the line 6-=6 of Fig. 4;

Fig. 7 indicates the separation of the slug from the gate;

Fig. 8 schematically represents the heating of the slug before forging;

Fig. 9 is a schematic vertical section showing a heated slug placed in the forging die; and

Fig. 10 is a similar section after operation of the forging plunger.

Referring to the drawing, and more particularly to Figs. 2 and 3, the molten metal is cast in a die cavity l2 to form a biscuit-shaped slug. The die cavity is largely closed at the top by means of upper mold portions ld and 16, to form a gate which is relatively constricted at 18 adjacent the Cavity, but which may, for convenience, be expanded or funnel-shaped thereabove as shown at 2l). The molten metal is readily poured into the funnel-shaped gate 2t), and after solidication of the mold parts ld and 16 may be pulled apart sidewardly relative to the base portion 22 of the die, as shown in Fig. 3. This clears the top of cavity l2, and permits upward removal of the slug 24. The gate portion 26 may be seized and pulled directly out of the mold. The cast piece looks somewhat as shown in Fig. l, except that it would not have the bevel 28 near the upper portion of the slug.

The base portion ZZ of the die is made of metal, usually steel, for long wear and to accelerate cooling of the cast metal. However, the upper die portions ld and 'lo are preferably made of a refractory material having poor heat conductivity. One example is talc in solid form. ln this way the metal in the gate remains liquid and tends to move downward to make up for any shrinkage taking place in the body of the slug, so that the effect of shrinkage is limited to the gate Where it is of no consequence.

InV Figs. 2 and 3 the die structure has been simplified for clarity, but a practical form `of die is illustrated in Figs. 4, 5 and 6 of the drawing. The main difference is that the refractory parts 3d and 32 of the die are protectively mounted in metal carriers 34 and 36. These carriers are slidable on the metal base portion 38 of the die, so that the cover portions slide with a metal-to-metal bearing.

More specifically, the base portion 38 may be provided with fixed guide tracks 40 and 42. These are secured to the sides of the base portion, as indicated by the screws in Fig. 6. The carriers 34 and 3o are channeled to receive the tracks 40 and 42, thus holding them against lateral and upward movement. The upper parts of the tracks 40 and 42 are cut away at the center, as indicated at 41 in Fig. 4.

The carriers 34 and 36 are recessed or cut away to receive the refractory parts 30 and 32, as will be clear from the drawing. The part 30 is anchored in carrier 34 by means of clamps 46, and the part 32 is held in carrier 36 by means of clamps 48. Moreover, the side edges preferably diverge outwardly, as is clearly shown in Fig. 4, thus effectively locking the refractory inserts 30 and 32 against movement in longitudinal direction. In Fig. it will be seen that a thinned part 50 of carrier 34 underlies the insert 30, and that similarly a thinned part 52 of carrier 36 underlies insert 32. This is important in order to provide a metal-to-metal sliding contact between the movable and stationary parts of the die. These underlying parts 50 and 52 are preferably shaped to form a part of the periphery of the main cavity rather than a part of the gate, because it is desired to decelerate cooling at the gate. Thus the elevation of the sliding surface is lowered, relative to Figs. 2 and 3, but the plane of separation between the talc and the steel is not. It then becomes convenient to bevel the edge of the carrier inwardly, as shown at 54 in Figs. 5 and 6, which in turn produces the bevel shown at 28 in Fig. 1. This is anyway desirable in order to make it easier to fit the slug within the cavity of the forging die, as later explained.

The permanent die for casting the slugs may be mechanically operated. This may be done in a number of ways, and detailed mechanism is not shown herein, but it will be noted that carrier 34 is provided with a cam follower roller d0 (Fig. 5) received in the cam track 62 of an operating member 64. Similarly carrier 36 is provided with a cam follower roller 66 received in a cam track 63 of a movable member 70. The members 64 and 70 may be moved transversely, and the cam tracks so shaped `as to thereby slide the carriers 34 and 36 together, as shown in Fig. 4, or to move them apart (as shown ln the more schematic Fig. 3). ln practice the operator closes the die, ladles molten metal into the funnel-shaped opening until the latter is nearly filled, and waits a suitable time for solidification. A number of dies may be provided so that the process may be made continuous without loss of time during solidication. After a suitable interval the die is opened and the slug and gate removed from the die, whereupon it is again closed and filled.

At another station the gate is severed from the slug. This may be done by machining, or even by breaking, but in practice it is preferred to employ a shearing or clipping machine, the` blades of which come together forcibly and separate the slug from the gate. The sepa* ration is schematically shown in Fig. 7. The gates are, of course, reme'lted for further use, while the slugs are sont on to the forging press.

T he slugs are heated immediately prior to forging, and this step is merely indicated by Fig, 8. Any One of a number of types of heater may be employed, either of the gas furnace type or of the high frequency or induction type. inthe case of aluminum the slugs are heated to a temperature range approximately 700 to 800 F. and more closely from 720 to 780 F. With a gas-heated oven automatically moving table may be used, `and the motion of the slug through the `oven then is so timed as to produce the desired temperature. The temperature should not be too high because portions of the slug may be rather liquid, and although the slug could be shaped readily in the forging die, the operation would not be 4 a true forging operation in that it might not change the crystal structure from the cast crystal structure to a forged crystal structure having substantial elongation of thecrystals. This is desired because of the improved characteristics and strength. On the other hand, the temperature of the slug cannot be too low, not only because excessive force will be required to work the metal, but what is even more important, because the metal may crack under the forging pressure as evidenced by numerous small fissure lines.

Of course, with another alloy the best temperature may be quite different. For example, with brass the slug should be heated to approximately 1300 to 1350 F.

The forging step is schematically shown in Figs. 9 and l0. The forging die comprises a stationary portion 72 and a movable portion 74 separating on a parting plane 76. With the die open the operator places a slug 78 in the die cavity 80. At this time the forging plunger 82 is retracted downward, as shown. A daub of lubricant is preferably applied to the slug. One satisfactory lubricant is a colloidal mixture of oil and graphite. The die is closed, as shown in the drawing, and the slug 78 is preferably so dimensioned, in relation to the quantity of metal needed and the shape of the die cavity, as to permit closing of the die without forging the slug, although in some cases a small bit of initial deformation may be caused by closing of the die itself. An upper plunger is shown at 84, `but this acts as a fixed part of the die, it being solidly backed at its upper end, as shown at 86.

To forge the slug, the lower or forging plunger 82 is raised under enormous pressure, say 100,000 lbs. per sq. inch. Thus for even a small piece, say two inches outside diameter, a large hydraulic cylinder, say 16" in diameter, may be subject to a pressure of say 1200 pounds per square inch, to produce the enormous force needed. This causes the metal of the slug to ow and to assume the shape of the die cavity, as shown by the change from Fig. 9 to Fig. 10 of the drawing. It will be understood that the quantity of metal in the slug is at least slightly in excess of that needed for the forged piece, thus insuring the production of a solid forging. Any excess metal may How outwardly on the parting plane in the form of flash, and an overflow passage for the reception of flash is preferably provided, as indicated at in the drawing.

If the forging is piston-shaped or cup-shaped, or, as in the present case, doubly cup shaped back-to-back, the

ow of the metal is such that the grain follows the con-v figuration of the piece, there being elongation axially in the skirt portion, elongation radially in the flat portion, and elongation on a curve at the junction therebetween. This is even better than elongation which is all axial as would be the case if the piece were machined from a solid piece of forged bar stock, apart from the extra cost of such an extensive machining operation.

The pinion 92 and rack 94 facilitate ejection of the forged piece. The forging ram 82 is retracted before opening the die. When the die opens the forged piece remains with the upper or ejector part 74 of the die. After the die has been opened the pinion 92 may be operated to force the combined ejector and core 84 downward, thus pushing the forged piece out of the upper die. This mechanism, and ancillary mechanism for stripping the forged piece from the ejector core 84, are more fully disclosed in a lcompanion application Serial No. 322,404, filed November 25, 1952, now Patent No. 2,759,380, granted August 21, 1956. A preferred form of press to receive the die is disclosed in a companion application Serial No. 322,456, filed November 25, 1952, now Patent No. 2,780,117, granted February 5, 1957.

The parting face of the die and the resulting fin are preferably located at the largest diameter of the piece. Thus the iin is easily removed by a separate trimming operation in a suitable trimming die, following which the forged piece may be finished by appropriate machinis forged after heating, but this does not introduce diiiv culty such as arises with hot forging of steel, for in hot forging steel the metal must be heated to a white heat, with consequent formation of scale. The aluminum slug may be forged at a relatively low temperature which does not introduce any problem of scaling or oxidation.

The forging operation may be completed in a single step in a single die, and is therefore rapid and inexpensive. The resulting forgings are suiciently uniform to meet comparatively rigid specifications, and this results largely from the uniformity of the grain structure and other characteristics of the metal in the cast slug. The latter in turn'are kept uniform by the procedure here taught, in accordance with which the cooling of the newly cast slug is relatively accelerated, while the cooling of the gate is relatively retarded, so that the gate effectively functions to receive dross, gases, and other impurities by simple floatation, and further functions to supply molten metal as needed to make up for shrinkage in the slug cavity.

lt is believed that the present improvement in the combined casting and forging of non-ferrous alloys in dies, as well as the advantages thereof, will be apparent from the foregoing detailed description. It will also be apparent that while the invention has been shown and described in preferred form, changes may be made within the scope of the invention, as sought to be defined in the following claims. It will be understood that the reference in the claims to heating the slug to desired temperature before forging the same is not intended to exclude the possibility of forging a slug at room temperature when dealing with a metal or alloy sufiiciently soft, ductile or plastic to be satisfactorily forged without preliminarily heating the slug. Differently expressed, the desired temperature to which such an alloy is heated is the ambient temperature.

What is claimed is:

l. A permanent mold for the casting of pure and solid slugs of non-ferrous alloy for subsequent heating and forging to desired configuration, said permanent mold comprising die portions which are all permanent and relatively movable to free the slug and gate leading thereto, the die surfaces at the slug being made of metal, and the die surfaces at the gate being made of a permanent refractory material in order to retard cooling of the gate and being relatively separable to free the gate and to afford repeated molding operations by means of the same die surfaces at the gate as well as at the slug.

2. A permanent mold for the casting of pure and solid slugs of non-ferrous alloy for subsequent heating and forging to desired configuration, said permanent mold comprising die portions which are all permanent and relatively movable to free the slug and gate leading thereto, the die surfaces at the slug being made of metal, the die surfaces at the gate being made of a permanent refractory material in order to retard cooling of the gate and being relatively separable to free the gate and to afford repeated molding operations by means of the same die surfaces at the gate as well as at the slug, said die surfaces at the gate being disposed over said slug and being of substantial height relative to the slug, in order to provide a gate of substantial height relative to the slug.

3. A permanent mold for the casting of pure and solid slugs of non-ferrous alloy for subsequent heating and forging to desired configuration, said permanent mold comprising a base portion made of metal and having formed therein an open-topped cavity corresponding to the desired slug, and a cover portion made of a permanent refractory material of poor heat transfer characteristic, and having formed therein a gate leading to the cavity, said `cover portion being made of parts which are movably mounted relative to the base portion, in order to free the gate and slug for removal from the cavity, and in order to afford repeated molding operations by means of the same die portions at the gate as well as at the slug.

4. A permanent mold for the casting of pure and solid slugs of non-ferrous alloy for subsequent heating and forging to desired configuration, said permanent mold comprising a base portion made of metal and having formed therein `an open-topped cavity of elementary shape corresponding to the desired slug, and a cover portion made of a permanent refractory material of poor heat transfer characteristic, and having for-med therein Y `a funnel-shaped gate of substantial height relative to the cavity and leading to the cavity, said cover portion being made of two separable parts arranged to move apart to free the funnel-shaped gate `and to expose the cavity, and in order to afford repeated molding operations by means of the same die portions at the gate as Well as :at the slug.

5. A permanent mold for the casting of pure and solid slugs of non-ferrous alloy for subsequent heating and forging to desired configuration, said permanent mold comprising a base portion made of metal and having formed therein an open-topped cavity of elementary shape corresponding to the desired slug, and a cover portion made of a permanent refractory material of poor heat transfer characteristic, and having formed therein a funnel-shaped gate of substantial height relative to the cavity and leading to the cavity, said cover portion being made of two separable parts slidably mounted on the base portion and arranged to move apart to free the funnel-shaped gate and to expose the cavity so that the cast piece may be seized by the gate and pulled upward from the cavity, said permanent refractory parts being protectively mounted in metal carriers, and `said carriers providing a metal to metal sliding contact with the base portion.

6. A permanent mold for the casting of pure and solid slugs of non-ferrous alloy for subsequent heating and forging to desired configuration, said permanent mold comprising a base portion madel of metal and having formed therein an open-topped cavity, and .a cover portion made of a permanent refractory material of poor heat transfer characteristic, and having formed therein a gate leading downward to the cavity, there being two refractory parts protectively mounted in two metal carriers, said carriers being slidably separable on top of the base portion with a metal to metal contact to free the slug and gate, the cavity for the slug being formed by the metal base and carriers, and the cavity for the gate being formed by the refractory material, said cover portion being made of two separable parts slidably mounted on the base portion and arranged to move apart to free the gate and to expo-se the cavity so that the cast pieces may be seized by the gate and pulled upward from the cavity.

7. A permanent mold for the casting of pure and solid `slugs of non-ferrous alloy for subsequent heating and forging to desired configuration, said permanent mold comprising a base portion made of metal and having formed therein an open-topped cavity, and a cover portion made of a permanent refractory material of poor heat transfer characteristic, and having formed therein a .gate leading downward to the cavity, said gate being of substantial height relative to the cavity and being greatly constricted at the cavity, said cover portion having two refractory parts protectively mounted in two metal carriers, said carriers being slidably separable on top of the base portion with a metal to metal Contact to free the slug and gate, the cavity for the slug being formed by the metal base and carriers, and the cavity for the gate being formed by the refractory material, said carriers being arranged to move apart to free the gate and to expose the cavity so that the cast pieces may be seized by the gate and pulled upward from the cavity.

References Cited in the file of this patent UNITED STATES PATENTS Seidel Jan. 19, 1909 Hixon June 30, 1914 Armstrong July 10, 1923 Vaughan Oct. 18, 1927 10 8. Eyermann June 12, 1928 Handler Dec. 17, 1935 Nutt Dec. 22, 1936 Dusevoir June 2, 1942 Brauchler July 13, 1943 Payne Feb. 15, 1949 Soffel Mar. 7, 1950 FOREIGN PATENTS i Great Britain July 29, 1926

Images