US2312830A - Method of making drawn, pressed, or stamped cupped objects of metals and alloys - Google Patents

Description

METHOD OF MAKING DRAWN, PRESSED, 0R STAMPED CUPPED OBJECTS OF METALS AND ALLOYS Filed Feb. 8, 1941 March 2 1943. B E. [-iLDRED 2,312,830

7 A Md 1NVENTOR. BY mac m M HTTORNEYS menial Mar. 2, 1943 UNITED STATES, PATENT OFFICE lVIETHOD OF MAKING DRAWN, PRESSED, OR STAMPED CUPPED OBJECTS OF METALS AND ALLOYS Byron E. Eldred, Scarsdale, N. Y., assignor to Co nfi tinuous Casting Corporation, New York, N. Y., a corporation of Delaware Application February 8, 1941, Serial No. 378,024

6 Claims.

or eliminate waste, by utilizirg sliced castblanks from which the object can be directly cupped by drawing, pressing or stamping the sliced cast blank without the necessity of preliminarily mechanically working-the casting be- I fore making cupped objects from the cast metal or alloy. I

- Other.v objects of the invention will be set forth in the following description and drawing which illustrate a preferred embodiment thereof. The annexed drawing is 'an elevation of a sliced disc of material from which the metal object is directly cupped by drawing or pressing or stamping or otherwise mechanically working the cast material.

The final body which .is thus drawn or pressed or otherwise worked to cup-shape may have a height which greatly exceeds the diameter thereof. It may be a cartridge case of munitions brass, containing approximately 70% of copper and 30% of zinc.

According to the present method of making I cartridge cases and other cupped containers or objects, the first operation is to cast abrass bar which is known in the trade as a sheet bar. This sheet bar is not a draw-casting and it has, as cast, an irregular crystal structure. The surface of this bar is first scalped or overhauled in.

order to remove surface imperfections,- and this cast bar is then rolled into a sheet or plate of suitable thickness. The density. of the metal material is increased bythis working and by annealing said metal material. A suitable final grain structure is obtained inthe sheet, or plate, by the recrystallization which results from this working and annealing. Discs of the required size are then punched from this rolled and annealed sheet orplate. These discs are then' cupped and drawndn a series of consecutive operations, by well-known methods. It is necessary frequently to anneal the partially-formed article between the various stages of cupping and drawing the same into final shape. The usual methods result in approximately of scrap in the process of manufacturing the disc blank, which is then used for the successive forming operations. Since the usual expense of rolling the cast metal into sheet or plate form is approximately ninety dollars per ton, the scrapping of this large percentage of the metal, after said metal has been rolled into sheet form, is a source of great loss, because the scrap metal which has received costly working must be returned to the melting furnace.

According to my invention, the disc blankswhich can be used immediately in the initial cupping and subsequent forming operations, are

produced directly from theoriginal casting by a simple cutting operation, thus eliminating the expensive rolling operation and greatly reducing the percentage of scrap metal which must be remelted. In addition to a large saving in cost of manufacture, the final product is produced with the usual and desired fine grain structure.

While the invention relates particularly to the production of cupped drawn containers which are closed at one end thereof and which are open at the other end thereof, and which are made of copper or copper base alloys, the in ention also includes the utilization of all metals and alloys.

According to my method, a continuous drawcasting is made of the metal or alloy, by the ing.

method described in U. S. Patent No. 1,868,099 dated July 19, 1932, and U. S. Patent No.

2,135,465 dated November 1, 1938. The resultant product is generally. described in U. S. Patent No. 2,048,733,'dated July 28, 1936.

Referring to the annexed diagrammatic drawing, the crystals in the draw-casting are either parallel to the longitudinal axis of the casting, as indicated by the arrow A, or else said crystals can be inclined in one or in both directions to said longitudinal axis, as indicated by.

the arrows -B and C. These crystals are large macro-crystals although there may be a small percentage of micro-crystals at the edge of the draw-casting. 1,.

The draw-casting which is thus made is preferably a cylindrical bar whose diameter is equal to the diameter of the sliced disc blank which is used in the initial cupping operation. The invention is not limited to any particular'crosssectional shape or dimension of the draw-cast- If the draw-castings are cylindrical, the cylindrical bars are then sliced into discs by means of saws or cutting wheels or the like. The cuts are made in planes which are perpendicular to the longitudinal axis of the cylindrical bar. In general, the draw-castings are cut along planeswhich are perpendicular to their longitudinal axes. The direction in which the metal passes through the draw-casting mold is parallel to the longitudinal axis of the drawcasting. If thin and sharp saws are used, the sliced blanks retain their original crystal formation. The temperature of the casting is not raised sufficiently during said slicing to change the crystal formation. It required, these discs may be smoothed or polished or milled to accurate diameter or thickness, but without substantially disturbing the original crystal formation.

Sliced blanks of this type are shaped into the final articles, by well-known methods. The blank is first cupped, and the partially formed article is treated in stages by cupping and drawing dies. The partially formed article is annealed between stages, whenever required. During these forming operations, the density of the metal remains substantially the same as in the original casting and in the original sliced blank.

\ The result of this mechanical working and annealing is to change the original macro-crystal structure to a final micro-crystal structure which is the same as if the metal bar had been rolled and annealed in the usual manner, prior to cutting out blanks therefrom.

The cast disc and sliced blanks are made of ductile metal which has been formed progressively from one end face of the sliced blank to the other face. I have discovered that when a draw-casting of the type above mentioned is cut transversely under proper conditions, the sliced discs retain their original high density and they are substantially free of intercrystalline stress and intracrystalline stress. Since such sliced discs are of uniform structure throughout, they have high ductility and uniformity. Since the draw-casting may have any desired crosssection, the invention is not limited to a sliced blank of disc shape. I

More than the usual number of stamping, drawing or cupping operations can be performed uponthis blank, before it is necessary to anneal the partially shaped blank. Indeed, it appears that successful annealing requires that a certain degree of stress and strain should 'be established in the mass of the metal, before using heat treatment for'relieving such stress. This heat treatment recrystallizes the metal or alloy.

plish the usual successive reductions, I can per form a greater number of successive passes without annealing the blank.

. in a claim or claims, I include pressing, stamping and, generally speaking, all operations whereby a metal blank is cupped by mechanical operation without substantially heating the same. It

will be noted that the thickness of the blank is less than its lateral dimension. As an example of the invention, and without limiting the invention to said example, the sliced disc blank which is shown in the drawing may have a height or thickness of 0.5 inch and a diameter of eight inches, in making a cartridge casing for ammunition. The crystals'of said disc are substantially macro-crystals, substantially all of which make an angle of less than 90 with the longitudinal axis of the disc, The angles of these macro-crystals with said longitudinal axis preferably do not exceed 45'. These macro-crystals may be arranged in two series, in each of which the axes of the crystals are parallel to each other. The axes of the respective series may make opposite'angles of 45 or less, with the longitudinal axis of the sliced blank.

Referring to the annexed diagrammatic drawing, the crystals in the draw-casting may be orientated either parallel to the main axis of the casting or at an angle thereto, it being desirable for the bestembodiment of the invention to progressivelyform the casting by suitable established heat flow so that a like crystalline structure of large macro-crystals, free from inter and intra crystalline stress, will result. The angle between the crystal and the main axis of the blank should be less than 90 and at any angle less than 90"-. v

Becauseof the remarkably high ductility of the metal discs of the invention, greater than usual working of the metal is found desirable before the first annealing takes place. Such ad- 1 ditional primary working in some instances may require one or more special forming dies to provide greater than usual reduction in the initial forming steps, or it may be desirable to use the regular dies and to carry the, work forward to a greater extent before the first annealing operation, thus establishing a breaking down of the macro-crystal structure with the establishment of the apparently required stress before heat treatment which will bring about recrystallization, providing the desired uniform micro-crystal structure required for further working as established in regular practice. When, by initial working and heat treatment, therequired microcrystal structure is =established, the subsequent reduction steps in the forming operation with the usual annealings'are proceeded with. the

metal being of like structure to that which is produced'from discs punched from rolled plates. When I refer to annealingdntermecliate the cupping and drawing stages, the invention is not The final product, due to the mechanical workmy invention, but it is' clear that numerous changes and omissions can be made without departing from'its spirit.

limited to annealing after each stage. The annealing is performed only when it is necessary to relieve internal stress and bring about recrystallization into micro-crystalline structure.

In some cases it may be found that the base" portion of the cupped drawn shape recived too little work in processirigto readily recrystallize on annealing. In such cases the blank or disc may be cut thicker and of smaller diameter and on the primary operation be'pressed in a die to increase its diameter or thin out its base.

If desired, the base part of the partially formed article, after the first stage, or after any other In order tolldefine the scope of 'theclaims, whenever I refer to the operation of cupping stage or stages, can be subjected to compression and lateral outward flow, without simultaneously mechanically working'the upstanding wall of the partially formed article, or without mechanically cross-section from a draw-casting of metal amenable to cupping operations and having a major proportion of macro-crystals, the thickness of the blank being less than its lateral dimension and substantially all of said macro-crystals forming an angle of less than 90 with the longitudinal axis of said sliced blank, then cupping and drawing said blank in a series of stages to the desired final shape, annealing the partially formed article intermediate said stages, and recrystallizing the material into substantially uniform microcrystalline structure by said mechanical operations and said annealing, so that the final article has said micro-crystalline structure.

2. A method of making a cupped metal article which consists in slicing a blank from a drawcasting of metal amenable to cupping and drawing operations and which has a major proportion of macro-crystals so that the thickness of the blank is less than its lateral dimension, and sub-' stantially all of said macro-crystals form an angle of less than 90 with the longitudinal axis of said sliced blank, .then cuppingand drawing said blank in a series of stages to the desired final shape, annealing the partially formed article intermediate said stages, and recrystallizing the material into substantially uniform micro-crystalline structure by said mechanical operations and said annealing, so that the final article has said micro-crystalline structure, said blank being cupped and drawn into final shape without suberation and annealing the blanks, whereby to es tablish a uniform micro-crystalline structure throughout the finished product.

4. The method of making a cupped articl of a metal amenable to cupping and drawing operations which comprises melting said metal and draw-casting it into a cylindrical bar of the'diameter equal to the diameter of the disc blank to be used in the initial cupping operation, slicing said bar in a direction substantially perpendicular to the axis thereof into 'disc blanks, then cupping said disc blanks. in cupping and drawing 1 dies, and annealing the blanks in such manner as to establish the desired micro-crystalline structure in the finish-ed product.

5. The method of making a cupped articl of brass which comprises melting the brass and draw-casting it into a cylindrical bar of the diameter equal to the diameter of the disc' blank to be used in the initial cupping operation, said draw-cast cylindrical bar having a preponderance of macro-crystals having angles less than 90 to the axis of the bar, slicing said bar in a direction substantially perpendicular to the axis thereoi into disc blanks without substantially raising the temperature thereof and while'maintaining the original crystal formation of the bar, then cupping said disc blanks in cupping and drawing dies in stages, and annealing the blanks eration, said draw-cast cylindrical bar having a preponderance of macro-crystals having angles less than to the axis of the bar, slicing said bar in a direct-ion substantially perpendicular to the axis thereof into disc blanks by sharp thin saws without substantially raising the tempera- BYRON E. ELDRED.

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