US2544678A - Apparatus for the manufacture of iron shot - Google Patents

Description

March 13, 1951 R. R. HANCOX ETAL APPARATUS FOR THE MANUFACTURE 01-" IRON sno'rs 2 Sheets-Sheet 1 Filed July 23, 1948 FIG.

INVENTORS: ROBERT R. HANCOX GEORGE L. TUER. JR. J. STUTZMAN MILO BY a ATTORNEYS.

March 13, 1951 R. R. HANCOX EIAL 2,544,678

APPARATUS FOR THE MANUFACTURE OF mom sno'rs Filed July 23-, 1948 2 Sheets-Sheet 2 FIG 2.

INVENTORS: ROBERT R. HANCOX EORGE L. TUERJR MILO J. STUTZMAN Maw- Patented Mar. 13, 1951 APPARATUS FOR THE MANUFACTURE OF IRON sno'r Robert R. Hanco-x, Kansas City, Mo., George L.

Tuer, Jr., Cleveland Ohio, and Milo J. Stutzman, Kansas City, Mo., assignors to Olin Industries, Inc., East Alton, 111., a corporation of Delaware Application July 23, 1948, Serial No. 40,276

' 4 Claims. I

This invention relates to the manufacture of "shot and more particularly the manufacture of iron shot useable as the projectile charge of shot shells, but also for other purposes, such as shot peening, cleaning of castings, and granite cutting.

Commercial shot aS used in shot gun shells or cartridges have heretofore consisted of lead or lead alloys in spite of various disadvantages to which lead shot are subject. Such shot are usually manufactured by dropping the molten metal from the perforations in the bottom. of a pan or riddle at top of a shot tower. During the fall through air, the globules assume a spherical shape, solidify asshot having av diameter roughly dependent upon the size of the perforations. of the riddle, and are finally collected in a quenching medium such as water. Because of a unique combination of physical properties, lead can be fabricated into a round shot of a desired size so efficiently and economically by the method described that it has not proved commercially feasible to fabricate shot of other desirable, but more dimcultly workable, metals such as iron- In general, iron shot may be formed by one of two methods, namely, the method of. form, ing drops of molten metal and allowing them to fall into a quenching medium, and the method of. casting. For mass production of the sizes of shot encountered in shot shells, the technique of casting is prohibitively expensive. Various dropforming methods, including subdividing a falling stream of molten metal by means of a heater member, atomizing, and the perforated crucible method similar to that used in the making of. lead shot, have been used heretofore in the attempted manufacture of iron pellets or shot. The

particles so produced consist of spheres, sphe-' roids discs, dumb-bells, and pear-shaped particles, or even irregular shaped particles with little uniformity in size. In some instances, only of shot formed by atomizing was found to be useable for ammunition. In prior methods for making ferrous shot wherein an aperturedmember or drop pan was utilized to subdivide the molten metal, it has been found that the apertures of said member very rapidly eroded or washed away so as to effect a disadvantageous change in the size of the stream passed. Unlike the practice of making lead shot, the size of orifices in a drop pan cannot be depended upon to control the size of shot formed of ironbecause the iron wets the material surrounding the orifice.

A principal object of this invention, therefore,

2 is to provide an apparatus for producing ferrous shot.

Another object is to provide an improved apparatus for producing on a large scale iron shot, a large proportion of which are of useable sizes. Another object is to provide an apparatus for producing iron shot of good spherical configuration. Other objects and advantages will be apparent from the following description and: accompanying drawing, in which:

Figure 1 is a schematic elevational view, partly in cross section, of a preferred embodiment of the invention;

Figure 2 is a schematic elevational view, partly in section, showing. a modified form of the apparatus of Figure 1;

Figure 3 is a plan view of the foraminous member used in the apparatus; and

Figure 4 is a fragmentary view, in section, of themember of: Figure 3.

In accordance with the present invention, iron shot having a favorable regularity of shape and ahigh uniformity of size; are. produced by interposing, in the path of fall of. a stream of molten metal, a moving screen whose active area is constituted of substantially more open spaces than of closed (solid) substance. Indeed it is preferable that the. openings in. the screen occupy at least 65% of the overall active area of the screen. By active area is meant that portion of the screen. which, in normal operation, will be interposed: in. the path of falling molten metal. The molten metal may be dropped from a ladle, furnace, or crucible, situated at an elevation above the screen.

After the stream of molten metal. passes through the screen, it is subdivided into particles which have the. desired volume. The particles are then deposited in a quenching bath, through which, in the course of further fall, they assume their final near-spherical shape and are set. The quenching. bath may be in the form of a spray or pool. of water or any other cooling liquid, with or without antioxidants, and should. be maintained' at or slightly above room temperature. above F., the sphericity of the shot decreases about 5% for each 20 F. rise in temperature of the bath, but bath temperatures down to nearly freezing produce satisfactory results.

The material of which the screen is made is preferably bibulous or bibulous-covered, although satisfactory results are attainable with non-bibulous screens if a layer of water or other cooling liquid is. maintained on the screen at th region which traverses the path of the falling molten metal. Consistent with the strength necessary to withstand the impact of the molten metal, without too much sacrifice of open area, textile fabric screens may be used. Bibulous screens formed of other fibers, such as ramie, synthetic textiles, asbestos, and the like, may be used. Wire or plastic strands covered with bibulous material supply means, such as a ladle (whichmay be a H small induction furnace) or a perforated crucible or pot, a continually cooled foraminous member of the type described herein for subdividing the molten metal'stream into molten shot, and a means for quenching and collecting the shot. In the fall from the furnace, the molten metal stream will break up into globules, due to the influence of surface tension. These globules are subdivided, upon meeting the screen from which they emerge, into banana" shapes. Surface tension acts upon the tiny bananas to subdivide them into spheres and near-spheres before they set.

The shot-making apparatus of Figure 1 includes means for dropping molten metal, such as the ladle having a lip 2. Disposed in a horizontal or inclined plane below the lip 2 is a rotatable foraminous member 3 constructed of fabric or wire mesh having an open weave of a suitable mesh size. A suitable foraminous member 3 may be in the form illustrated in Figure 3 and consists of a circular-piece screen, the individual wires of which are covered with cotton. Alternatively, cotton mesh, or lacquered, enameled, or otherwise thermally insulated wire mesh may be used. The Screen 3 may be pierced by a hole t in order that the plate may be centrally mounted for rotation. Mounted upon the end of the vertical shaft 5 by any means, such as a combinationof washers and nut 6, the screen is driven by a suitable means, such as electric motor' '3 through shaft 5. A hoop 8 may be provided to hold the screen taut. Disposed below the screen 3 is a vessel i0 containing a quenching liquid H, such as water or any other suitable coolant, to a suitable depth for receiving and solidifying the falling shot 12 formed at the screen. In order that the member 3 be continually cooled, the cotton covering of the screen is kept well wet with liquid at all times. To accomplish this, a pip 13 terminating in nozzle 14 is so placed that portions of the cotton covered screen utilized for the subdivision of falling metal are alternately subjected first to the stream of cooling liquid issuing from nozzle l4, and then to the stream of molten metal, so that the screen is wet when the metal strikes it. The water is vaporized as the hot metal strikes it, thus providing an insulating blanket of live steam between the molten metal and the screen.

In the alternative form of apparatus shown in Figure 2, the screen 23, corresponding to the screen 3 of the previous embodiment, is situated below the surface of the quenching medium in tank (0. Otherwise, the parts are identical with those previously described save that the water supply pipe 13 and its nozzle M are omitted.

In the manufacture of iron shot for use in shot 4 gun shells, it is desirable to produce as high a yield as possible within the size range of 0.055 to 0.157 inch in diameter. The present invention produces advantageous yields of properly shaped shot within the size range just indicated. For example, utilizing the apparatus shown in Figure 2 with th screen one quarter of an inch under the surface of the quench bath, molten ingot iron poured at a temperature of 3100 F. through an atmosphere of air from an elevation of about 18 inches above the screen 23, yielded 70% (of the input metal) within the size range indicated above and of good sphericity. In this operation the screen was a cotton-covered wire screen having 10 mesh per lineal inch (mesh 0.077 inch square, filament diameter 0.018 inch) and moving at a lineal velocity (at the mean. radius of impact) of 1.6 feet per second. Thev rate of pour was between and grams per:

second.

As another exemplary operation, utilizing the apparatus shown in Figure 1 with a 'I-mesh cloth. screen, rotating on an axis inclined 26 away from vertical, a yield of 80% within the size range aforesaid and of good sphericity was achieved. In this instance, the distance between, the crucible lip and the scrcen (point of impact) was 8 inches and there was a distance of 30- inches between the screen and the surface of the. quench bath. The iron was poured at the rate. of 157 grams per second and at a tempera-- ture of 3100 F. The screen was moving at a. velocity of 3.2 feet per second at the mean radius. of impact.

When, other things remaining the same as in the last example, the screen-to-quench distance; was reduced to 6 inches and the rate of pour reduced to 144 grams per second, the yield was 80%, but the average size of the resultant shot increased. Experience indicates that, as the distance between the screen and the surface of thequench bath is increased (other variables re-- maining the same), the average size of the resultant shot decreases, but sphericlty improves..

With the screen less than about 6 inches abovethe surface of the quench bath, the results are; less satisfactory from the standpoint of both good By reducing the inclination of the screen to- 15, providing a space of two feet between the-- screen and the quench bath, and maintaining.

other factors substantially the same as indicated in the paragraph next above, the yield was 81% with the average size of the shot reduced.

In addition to the yields indicated in the ex'-- amples given above, there are appreciable quantities of shot of good sphericity, but whose size is outside the range of 0.055 to 0.157 inch. Such shot are suitable for other purposes than use in shot shells.

For shot shell purposes, but not for some other purposes, it is preferable to employ iron as pure as commercially feasible and relatively free of carbon. To facilitate the shot formation from such iron, it is preferable to elevate the tempera ture thereof to above 2800 F. before pouring from the ladle. The rate of pour is so controlled as to keep the concentration of globules (below the screen) low enough that the likelihood of col lision between them (with resultant formation of dumb-bells) is minimized.

In general, the greater the ratio of open area to obstructed area (filament) of the active portion of the screen, the higher the yield of shot of good sphericity.

The depth of the liquid in tank [0 is thirty inches or more or, in any case, sufficient to solidify the globules of metal before their fall is obstructed by the bottom or by other shot on the bottom.

In the embodiment of Figure 1, where the screen is situated above the surface of the quenching bath, the cooling liquid must be fed at a rate sufficient to keep the bibulous screen soaked or saturated. Where a bibulous screen is used, the velocity of movement is not of great importance-indeed the screen is moved only to assure that the increment of screen, exposed to the molten iron at any instant, is cool and wet.

While the invention has been described with particular reference to the manufacture of iron shot for use as ammunition projectiles, it is to be understood that the apparatus may be used with other metals, and to make shot for other purposes. Each different metal requires some adjustment of the several variables and likewise the optimum sizing of the shot.

From the foregoing description those skilled in the art should readily understand the invention and recognize that it accomplishes its ob- ,iects. While several examples have been given for the purpose of il ustration, it is to be distinctly understood that the invention is not limited to the details thereof.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. Ap aratus of the kind described comprising, in combination, supply means for maintaining a supply of molten metal and for discharging a stream thereof. a screen arranged below said supply means and in the path of a stream of molten metal falling from said supply means. said screen having substantially more than half its active area occupied by open spaces, means for moving said screen transversely of the path of the stream of molten metal falling from said supply means, and a quench tank arranged to receive particles falling from said scree 2. Apparatus of the kind described comprising, in combination, supply means for maintaining a supply of molten metal and for dis'charginga stream thereof, a screen arranged below said supply means and in the path of a stream of molten metal falling from said supply means, means for moving said screen transversely of the path of the stream of molten metal falling from said supply means, a quench tank arranged to receive particles falling from said screen, said screen having at least sixty-five per cent of its area open, and said screen having at least the outer increments of its constituent strands composed of bibulous material, and means for wetting said bibulous material with liquid coolant.

3. Apparatus of the kind described comprising, in combination, supply means for maintaining a supply of molten metal and for discharging a stream thereof, a screen arranged below said supply means and in the path of a stream of molten metal falling from said supply means, means for rotating said screen in a direction transversely of the path of a stream of molten metal falling from said supply means, and a quench tank arranged to receive particles falling from said screen, said screen having at least sixtyfive per cent of its area open.

4. Apparatus of the kind described comprising a screen composed of strands, said strands having at least their outer increments composed of bibulous material, means for supplying a stream of molten metal to the upper surface of said screen, means for moving said screen transversely of the path of a stream falling from said supply means, and means for continually wetting the bibulous material with liquid coolant,

ROBERT R. HANCOX. GEORGE L. 'I'UER, JR. IVIILO J. STUTZMAN.

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

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