GB1605234A

GB1605234A - Fragmentation casing for a shell warhead or other ammunition

Info

Publication number: GB1605234A
Application number: GB3471576A
Authority: GB
Original assignee: Diehl GmbH and Co
Current assignee: Diehl Verwaltungs Stiftung
Priority date: 1975-09-06
Filing date: 1976-08-20
Publication date: 1985-06-05
Also published as: NL7609706A; DE2539684C1; IT1067547B

Description

(54) A FRAGMENTATION CASING FOR A SHELL, WARHEAD OR OTHER AMMUNITION (71) We, DIEHL GMBH & Co., formerly known as Diehl, of Stephanstrasse 49, 8500 Ntirnberg, Germany, a Kommanditgesellschaft organised under the laws of the Federal Republic of Germany, the present personally responsible Partner being Siiddeutsches Metall-Kontor GmbH. do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a fragmentation casing for a shell, warhead or other ammunition, in which preformed fragments are held in a matrix of metal, which is disintegratable by detonation of an explosive charge which is arranged inside the fragmentation casing.

In German Patent Specification No.

2,322,728 it has already been proposed to produce fragmentation casings of the aforesaid kind in that preformed fragments are introduced in layers into a framework of metal powder which supports them, and are pressed and sintered together with the metal powder to a projectile-shaped, tube-shaped or shellshaped fragmentation casing in such a way that extending before the preferably singlelayer fragmentation jacket consisting of the preformed fragments, at least inwardly, towards an explosive charge, is a fine-pored sinter jacket which is compressible under the effect of the detonation wave arising upon the detonation of the explosive charge.

Already known through German Offenlegungsschrift No. 1,943,472 is a fragmentation warhead having preformed fragments, in which the fragments are combined by sintering into a supporting component part which forms the warhead jacket, or at least a part of the same. In this connection provision is made for filling spaces, possibly remaining free between the fragments, with a specifically light material, such as aluminium or plastics material.

Furthermore, in German Patent Specification No. 2,536, 308 it has been proposed to cast around fragments, filled for example into a circular-ring-shaped, lattice-like hollow cylinder, with a metal matrix and thus to provide a fragmentation casing which is insertable into a projectile or can be assembled with remaining projectile parts into a projectile.

In the case of both production processes for the fragmentation casings, the fragments that are to be embedded into the matrix are subject to a more or less severe heating extending over a certain period of time, upon the sintering-in, possibly up to 13000C, depending on whether a light metal sinter matrix or whether a sinterable heat-treatable steel is used for this. Even upon casting-around of the fragments with light metal the fragments depending on the alloy components - are heated to about 500 to 8000. Fragments made of normal steel lose, in this respect, their hardness and penetration effectiveness. On account of this unavoidable heating of the fragments, a hard material has been used for the fragments, i.e. a material which upon heating remains hard or in which the temperature limit at which it loses its hardness and strength lies above the processing and after-treatment temperature of the matrix.

Such a material is, for example, tungsten carbide; however, this is not only very expensive, but also difficult to work.

The problem underlying the present invention is to make a choice of material and to find a production process which makes possible the use of cheaper materials with the same penetration effectiveness of the embedded fragments and of the matrix when disintegrated into individual particles, in which connection the production process should be simple, i.e. executable with equipment which is customary in sintering or casting technology.

According to the invention, there is provided a fragmentation casing for a shell, warhead or other ammunition, in which preformed hardened or heat-treated fragments of steel or alloy steel are held in a matrix of metal which is disintegratable by detonation of an explosive charge arranged inside the fragmentation casing, said holding of the fragments in the matrix being effected by sintering or casting of the matrix, and the material of the steel or alloy steel fragments and the material of the matrix being such that (having regard to the temperature at which, having regard to the material of the matrix, the said sintering or casting can be carried out) the heating of the matrix necessary for the sintering or casting is able to serve also as a treatment or treatment step for hardening or heat treatment of the fragments.

A particularly advantageous solution is seen in producing the fragments from a hothardening, namely a martensite - hardenable, steel, in embedding these in soft state into the matrix and in hardening them through the heat occurring upon sintering-in or castingaround of the fragments. A heat treatment of the matrix effects a re-tempering of the fragments.

As sinter material there can serve - depending on the purpose and on the fragment material - a light metal alloy on an Al-Cu-Mg or Al-Cu-Zn basis or a sinterable steel alloy, for example made of heat-treatable steel, and as casting alloy preferably an Al-Cu-Ti-Fe alloy.

Through suitable matching of the material for the fragments, on the one hand, and for a sinter or casting matrix, on the other hand, as well as through a possibly multi-stage, oscillating heat re-treatment of the fragmentation casing, an end product of high effectiveness can be achieved which is not only simpler to produce, but above all is also substantially cheaper.

In the accompanying drawings, which illustrate by way of example, embodiments of the invention: Fig. 1 shows a side view of a projectile body; Fig. 2 is a longitudinal section of the portion shown at II in Fig. 1 and shows fragments sintered into a matrix; Fig. 3 is a longitudinal section of the portion shown at III in Fig. 1 and shows a modified arrangement with fragments held in a wire cage and cast around by a metal matrix; and Fig. 4 shows a working diagram for the heat treatment of fragments, more specifically of a fragmentation casing, in a sintering process, which may be used in the production of the projectile shown in Figure 1.

Referring to Figures 1 and 2 of the drawings, a projectile body 1, formed as a fragmentation casing, has, as shown in Figure 2, fragments 2 (which may be for example spherical or cylindrical) embedded into a matrix 3 of sinter material. This fragmentation casing 2, 3 encloses an explosive charge 4.

In the arrangement shown in Fig. 3, the fragmentation casing has spherical fragments 5, which are held in a lattice basket 6 in the form of a hollow cylindrical annulus and are cast around with a metal matrix 7. This fragmentation casing 5, 6, 7 likewise encloses an explosive charge 4.

Serving as material for the production of the fragments 2 or 5 is preferably alloyed steel which can in the soft state easily be worked into the desired geometrical fragment shape, for example into spheres, cylinders or the like and subsequently hardened or re-tempered, for example in accordance with the diagram constituting Fig. 4. Also for the matrix 3 or 7 there can be used a suitable steel alloy, preferably a heat-treatable steel, into which the fragments 2 are embedded by sintering and which subsequently, i.e. with the fragmentation casing 2, 3 sintered, is tempered by a heat treatment. In this way the matrix is given not only the necessary strength for the absorption of the axial and radial forces which occur upon the discharge, but also the toughness and hardness which is necessary in order to achieve an optimum penetrating capacity not only of the embedded, preformed fragments 2, but also of the matrix 3 subdivided into individual splinters.

Upon the use of a steel alloy for the matrix 3, the heating necessary for the hardening of the fragments 2 is effected upon the sintering process itself. If, on the other hand, a light metal sinter or casting alloy is used as the material for the matrix 3 or 7, then the fragments 2 or 5 are embedded preferably already pre-hardened into the matrix 3 or 7.

The heat which occurs upon the sintering-in or casting-around in such case effects for the fragments 2 or 5 merely an annealing or retempering of the fragment material.

The heat treatment to be applied is governed largely by the respective choice of material for the fragments 2 or 5 and the matrix 3 or 7, more specifically, the material matching.

Examples of the material matching and of the respective heat treatment are explained in more detail later on. In each case the heating of the fragments 2 or 5, ensuing upon the sintering-in or casting-around of the fragments 2 or 5, is a treatment step which is necessary for the hardening or tempering thereof.

As a first example there will be described the production of a fragmentation casing by sintering of preformed fragments into a matrix of iron powder, more specifically steel powder. Usable as the material for the matrix is, for example, a heat-treatable steel with 0.26 to 0.6 per cent by weight C, which is hardened and tempered after the sintering.

There can serve as fragment material, a generally used steel which is hardenable by heat treatment, for example a Cr-steel with 6% Cr, or a tool steel, structural steel or heavy-duty die steel. A martensite-hardening nickel steel with, for example, 18% Ni, 8% Co, 5% Mo as well as possibly 0.45 Ti and 0.1 Al, remainder Fe, i.e. a steel which is hot-hardening, has, in particular, also proved to be suitable.

Upon the sintering-in of the fragments into the matrix, the fragments are heated for several hours up to about 12800. In this connection, spheres of Cr-steel are completely annealed, others need in each case a differentiated heat treatment, as is known by itself for the hardening of the respective kinds of steel. If, on the other hand, fragments made of hot-hardening steel are used, then a martensite formation is achieved by quenching of the sintered fragmentation casing in an oil, air or hot bath and subsequent annealing for 30 minutes at 200"C.

For the grain refining of the fragmentation material it can be necessary or expedient, subsequent to the sintering or quenching process, to insert prior to annealing, additionally an intermediate stage hardening by possibly repeating heating to 5500 to 800" and subsequent quenching.

Upon use of high-speed steel for the fragments and iron powder, more specifically steel powder, for the sinter matrix, the working pattern may provide for instance for the following production steps: Production of the fragments from high-speed steel; Pickling of the fragments as well as coating with a separating layer, for example with oxides, which prevents any agglomeration of the fragments with the matrix upon the sintering; Pressing of the fragments into the powdery steel matrix; Sintering of the matrix and heating of the fragments to 12500 to 13200C; Cooling of the fragmentation casing in air or hot bath storage at about 3500C for 2 hours; or instead of this, annealing, possibly repeated twice, at 5800C in each case for about 1h to 1 hour.

As a second example, there will be described the sintering of preformed steel fragments into a light metal matrix on an aluminium basis.

Serving as matrix material is, for example, an Al-Cu-Mg-or Al-Cu-Zn-alloy hardenable by hot and/or cold age-hardening. Such an alloy may consist, for example, of 0.2 - 4.9% by weight Cu or about 1.6% by weight Cu 0.2 - 1.8 by weight Mg or about 0.3 by weight Si 0.2 - 1.1 by weight Mn or about 2.5 by weight Mg possibly 0.2 - 0.8 by weight Si or about 5.6 by weight Zn remainder Al or about 0.2 by weight Cr Remainder A Al The sintering temperature is, in this connection, abut 550 to 6000C; the sintering process extends over about 1 to 2 hours.

From these sintering conditions two alternatives emerge for the fragment material: 1) the fragments of steel are pressed-in, hardened and tempered or further hardened by the sintering temperature, or 2) the fragments consist of a hot-hardening steel and are not further altered or else retempered by the sintering process.

A steel of the first-mentioned kind consists, for example, of: 5.0% Cr, 1.3% Mo, 0.5% V, Remainder Fe.

It can be processed soft-annealed, be hardened by heating to 10100C and quenching in air. Prior to the sintering-in, the fragements are if necessary annealed a first time at about 550"C for three hours. Then the fragments are pressed into the sinter powder and sintered-in at about 570 - 580"C for two hours. The heating of the fragments upon the sintering represents the final annealing process of the fragment material.

If, on the other hand, the fragments are produced from a steel of the kind mentioned under (2), for example the already mentioned Ni-Co-Mo (18, 8, 5) steel, then a substantial part of the hardening ensues upon the sintering process itself.

Upon use of a semi-austenitic dispersionhardening steel, the age-hardening temperature of which lies at 370" to 5930C, the sintering and age-hardening can be carried out in one operation. In this connection, an elastic limit of up to 183 kp/mm2 is achieved.

The work cycle of the sintering and hardening process with the use of high-speed steel - consisting of, for example, 0.8% C, 6.5% W, 5% Mo, 2% V, 4.3% Cr, remainder Fe - for the fragments and aluminium for the sinter matrix can be subdivided in accordance with Fig. 4 into several, chronologically consecutive, steps. In this connection, the broken-line curve shows an alternative in the sintering and the heat re-treatment. In both instances the fragments are intitially preheated (a) and heated in a salt bath to a temperature of about 1280"C (b). Then a quenching (c) is effected, namely in accordance with the work step shown in solid lines, in oil at room temperature. After a pre-cleaning phase (d), the fragments are, in a further work step (e), annealed, namely at about 560"C for about 1 to 2 hours, whereupon, after cooling has been effected (f), the fragments are subjected to a pickling and drying process (g), in order to rid the surface of the fragments of scale and other residues. Then the fragments are embedded and pressed into the aluminium powder and then, in a final work phase (h), sintered at a temperature of about 580"C, within about 2 hours, into the matrix. The heating acting, in this respect, on the fragments represents a second heat treatment step effecting a tempering of the fragments. After a cooling subsequent thereto and hot age-hardening of the fragmentation casing, for example about 15 hours at 120 - 140"C - or cold age-hardening at room temperature over about 30 days - the fragments have the properties, necessary to achieve adequate penetration effect, with regard to hardness, strength and toughness and the light metal matrix has the strength necessary for the absorption of the axial and radial forces occurring upon the firing of the projectile provided with the fragmentation casing produced in this way.

Instead of quenching the fragments in oil, these can be cooled, subsequent to the hardening (b) in the salt bath, at about 240"C in a hot bath (i). Then, after pickling and drying (k), there is immediately effected the pressing of the fragments into the Al matrix and sintering-in (1) in accordance with the material requirements, for example again over 2 hours at about 580"C. After a cooling of the already sintered fragmentation casing in the hot bath and age-hardening (about 1 hour) (m) as well as subsequent further cooling (n) to room termperature there is effected once more a re-tempering consisting of at least a single, preferably a repeated, heating phase (o) to about 580"C.

In a comparable way there is effected prehardening and heat after-treatment of the fragments if these are - for example, embedded in accordance with Fig. 3 into an annular hollow cylindrical cage 6 - cast around with an aluminium casting alloy, consisting, for example, of about 4.5% Cu, 0.2% Ti, 0.4% Fe, remainder Al. In this connection, temperatures comparable with the sintering process occur and thus also approximately the same hardening cycles in the material structure both of the fragments and of the matrix. The working pattern may be for instance as follows: Production of the fragments from softannealed high-speed steel. Hardening of the fragments by heating to 1200 up to 13100C and quenching in oil, air or in the hot bath at about 350"C for 2 hours, filling of the fragments into the hollow cylindrical annular fragment support, placing, suspension or forming of the fragment support together with fragments into a casting mould and casting-around of the same with a light metal casting alloy.

Cooling of the casting matrix - preferably at about 350"C in the hot bath. Single to double annealing respectively for about 1M2 to 1 hour as far as shortly below the softening point of the casting alloy.

If, instead of steels of the aforesaid kind, medium-alloyed chromium-, molybdenum-, or vanadium-steels are used for the production of the fragments, then the preceding hardening of the fragments should be dimensioned in accordance with the hardening temperature of the respective kind of steel, likewise the heat after-treatment of the finished fragmentation casing. Depending on the diameter or size of the fragments, the wall thickness of the matrix enclosing the fragments, the matrix material and finally the projectile calibre, a different heat treatment is necessary in order to impart to the fragments the necessary hardness and strength, without making them so brittle that they burst upon target impact. In the same way or the way already mentioned earlier, through the heat after-treatment the strength or disintegration capacity and penetration effectiveness of the matrix or of the particles arising from it upon the disintegration is also controllable.

Through suitable matching, an optimum penetration effectiveness corresponding to the target to be combatted can be achieved through a material matching and heat treatment of the fragmentation casing, produced by sintering-in or casting-around of steel fragments.

WHAT WE CLAIM IS: 1. A fragmentation casing for a shell, warhead or other ammunition, in which preformed hardened or heat-treated fragments of steel or alloy steel are held in a matrix of metal which is disintegratable by detonation of an explosive charge arranged inside the fragmentation casing, said holding of the fragments in the matrix being effected by sintering or casting of the matrix, and the material of the steel or alloy steel fragments and the material of the matrix being such that (having regard to the temperature at which, having regard to the material of the matrix, the said sintering or casting can be carried out) the heating of the matrix necessary for the sintering or casting is able to serve also as a treatment or treatment step for hardening or heat treatment of the fragments.

2. A fragmentation casing as claimed in Claim 1, wherein the matrix is disintegratable upon the detonation of the explosive charge, and along with release of the embedded fragments, into individual particles of defined shape, size and penetrating capacity.

3. A fragmentation casing as claimed in Claim 1 or 2, wherein the fragments are embedded in the matrix to be enclosed thereby from the outside and the matrix is of a light metal or a light metal alloy or sintered iron or steel.

4. A method of producing a fragmentation casing of the construction set forth in Claim 1, wherein the fragments are embedded in a soft state in the matrix and are held in the matrix by heating the matrix to cause sintering or casting of the latter, said heating serving also as a treatment or treatment step for hardening of the fragments.

5. A method of producing a fragmentation casing of the construction set forth in Claim 1, wherein the fragments are embedded in a hard state in the matrix and are held in the matrix by heating the matrix to cause sintering or casting of the latter, said heating serving also as a treatment or treatment step for tempering of the fragments.

6. A method of producing a fragmentation casing of the construction set forth in Claim 1, wherein the fragments are of a hot-hardening, namely a martensite-hardenable, steel, are embedded in a soft state into the matrix, and are hardened only through heating effected upon sintering-in of the fragments.

7. A method of producing a fragmentation casing of the construction set forth in Claim 1, wherein the fragments are of a material hardenable by heating and subsequent quenching in oil, air or water and are introduced hard or soft into the matrix, are heated through the heating ensuing upon sintering-in into the matrix or upon castingaround with a metal casing forming the matrix and undergo hardening upon a subsequent quenching of the matrix.

8. A method of producing a fragmentation casing of the construction set forth in Claim 1, wherein the matrix is of sinterable light metal alloy powder on an aluminium basis, into which the fragments are sintered-in at about 600"C and which is hardened and/or tempered through a subsequent heat after-treatment to the strength necessary for absorption of accelerative and rotational forces exerted on the fragmentation casing upon firing.

9. A method as claimed in Claim 8, wherein the matrix consists of a Al-Cu-Mg or Al-Cu-Zn alloy which is hardened after sintering through hot and/or cold agehardening and which, after sintering-in of the fragments has been effected, is hardened by quenching of the matrix in oil, air or water and subsequent hot age-hardening - about 15 hours at 1200 - 140"C - or cold age-hardening about 30 days at room temperature - to the necessary strength values.

10. A method of producing a fragmentation casing of the construction set forth in Claim 1, wherein the matrix is an aluminium casting alloy, with which the fragments or a lattice cage receiving them are cast around and which is hardened through a heat after-treatment serving simultaneously for the hardening or tempering of the fragments.

11. A method as claimed in Claim 10, wherein the aluminium casting alloy consists of 4.5% by weight Cu, 0.2% Ti, 0.4% Fe, remainder Al.

12. A method of producing a fragmentation casing of the construction set forth in Claim 1, wherein the matrix consists of a sinterable heat-treatable steel which after sintering is hardened by quenching thereof, if necessary with simultaneous hardening of the fragments, and is tempered to the necessary strength in a tempering process serving for grain refinement.

13. A fragmentation casing when made by a method in accordance with any one of Claims 4 to 12.

14. A fragmentation casing, substantially as hereindescribed with reference to the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. they burst upon target impact. In the same way or the way already mentioned earlier, through the heat after-treatment the strength or disintegration capacity and penetration effectiveness of the matrix or of the particles arising from it upon the disintegration is also controllable. Through suitable matching, an optimum penetration effectiveness corresponding to the target to be combatted can be achieved through a material matching and heat treatment of the fragmentation casing, produced by sintering-in or casting-around of steel fragments. WHAT WE CLAIM IS:

1. A fragmentation casing for a shell, warhead or other ammunition, in which preformed hardened or heat-treated fragments of steel or alloy steel are held in a matrix of metal which is disintegratable by detonation of an explosive charge arranged inside the fragmentation casing, said holding of the fragments in the matrix being effected by sintering or casting of the matrix, and the material of the steel or alloy steel fragments and the material of the matrix being such that (having regard to the temperature at which, having regard to the material of the matrix, the said sintering or casting can be carried out) the heating of the matrix necessary for the sintering or casting is able to serve also as a treatment or treatment step for hardening or heat treatment of the fragments.

accompanying drawings.

15. A method of producing a fragmentation casing, substantially as hereindescribed with reference to the accompanying drawings.