US2190536A - Method of manufacturing hollow articles from metals - Google Patents

Description

Patented Feb. 13, 1940 UNITED STATES PATENT OFFICE METHOD OF MANUFACTURING HOLLOW ARTICLES FROM METALS Drawing. Application November 23, 1937,

Serial No. 178,143. In Germany November 6,

This invention relates to the manufacture of hollow bodies, in particular cartridge cases, shell cases and the like, from metals, especially nonferrous metals. As is well known, such cases are made from circular discs which are shaped in I numerous pressing and drawing stages.

The usual method is tostamp the circular discs from a sheet of metal. The raw material has to pass through many stages before it is converted into the form of a sheet. The metal must be melted and cast, the ingots must be milled and then hot rolled and pressed and cold rolled. The discs are then stamped out and annealed. Only when this has been done, can theactual work of cold shaping be begun. The actual manufacturing costs of the circular discs are considerably increased owing to the amount of waste produced. The weight of the waste formed during the stamping is at least equal, under ordinary conditions, to the weight of the finished discs. In most cases it is greater.

Now, it has previously been proposed to form the discs by sawing rolled or pressed and drawn bars instead of by stamping the discs out of sheet metal. In this way it is true that the waste produced in stamping the discs out of the sheet metal is avoided, but this advantage is off-set by the disadvantage that, in pressing these heavy bars, 25 to 40% of waste is produced. In the extrusion press alone, a waste of 25 to 35% must be reckoned on, in the case of bars of the large diameter which are here in question, to which must also be added the dead heads lost in casting, the loss by burning and so forth which may amount to from to%. This method of operation therefore has no advantage, over the method of manufacture from rolled sheets, especially when the cases are made of non-ferrous metals,

and therefore the method has not come into practical use.

According to the present invention, the circular discs which are used as the starting material for 1 Claim. (01. 29-13) the like. The shaping of the discs as well as the necessary annealing between the shaping stepsensures that the material undergoes recrystallisation in the course of the process which has been found by experience to be advantageous.

Particularly good results are obtained if a copper-zinc alloy containing about 72% copper is employed, with which additional substances which make the grain finer, such as nickel, iron or lead are alloyed, and if the cast bars are cooled down rapidly after casting. I

In order to avoid roughening the surface of the discs having a cast structure when they are being shaped, it is advisable to carry out the first shaping or deformation step either at room temperature or at an elevated temperature which is below the usual hot working temperature. It is also desirable to effect very high degrees of deformation followed by recrystallisation annealing at relatively low annealing temperatures in the various stages in order to obtain a final productof which the quality is equal to that produced from sheet metal.

Usually the cast bars will have the same diameter as the circular discs which are subjected to the shaping operations are to possess. -In general it is not necessary to remove the casting skin by turning, because this skin is in any case removed during the ordinary course of manufacture of the case. If, however, removal of the skin is required, then the diameter of the cast rod must obviously be correspondingly greater.

It is possible by means of the new process to manufacture cartridge and like cases with a considerable saving of metal and work. There is the further advantage that the alloys, for example of copper and zinc, may contain a larger amount of foreign materials than is otherwise permissible since with the new process no hot deformation, which is impaired by the presence of foreign substances, is necessary; as, when the usual methods are employed, it is practically impossible to manufacture sheets from east ingots solely by cold deformation. Therefore, the copper-zinc alloys may contain larger amounts of lead and phosphorus than would otherwise be allowable.

The main advantage of the new process is in the entire elimination of all rolling Work and the costs thereof, as well as the avoidance of the waste which is occasioned in the manufacture of rolled plates and the stamping of the discs from these plates.

1 claim:

The process of producing cartridge cases w r ni to the form of cartridge cases and zinc-copper alloys comprising casting a bar of 58 with annealing treatments, the temperature of the alloy in the first drawing operation being below the usual hot-working temperature of the alloy and the first drawing operation performing a high degree of deformation to avoid roughening 5 the surface of the articles.

KARL STAIGER.