EP0605030B1 - Compression molded, noble metal-containing explosive and its use - Google Patents

Abstract

It is known per se to add metal powders to explosives, in order to obtain a certain conductivity so that electrostatic charges can be conducted away. It was necessary, however, to dispense with the achievement of a galvanic conductivity, since a high metal content considerably reduces the power of the explosive. By admixing a small proportion of rare metal platelets (1) to a binder (3) and to explosive grains (2), a homogeneous mixture can be obtained which, after pressing to give mouldings, is galvanically conductive. In addition to an explosive sample, a process for the preparation thereof and a preferred use are claimed. <IMAGE>

Description

The present invention relates to a metal-containing explosive body formed by pressing.

It is known (CH -A5- 462 688) to mix ammonium nitrate explosive with mineral oil and metal powder with the aim of reducing its sensitivity to electrostatic charges. Such explosives are mainly used in civil engineering and are usually filled into boreholes.

Metallic fibers are used for the mechanical reinforcement of explosive charges (US Pat. No. 3,960,049), which likewise achieves a certain conductivity.

It is also known (FR-A- 2 003 626) to cause explosive charges made of pressed nitrocellulose fibers to be heated and thus initiated by means of solid electrical lines.

In all cases, only a relatively low specific conductivity and no actual galvanic line is achieved.

It is therefore an object of the invention to provide an explosive which is a good conductor of electricity and which has high performance and handling safety.

Compared to other known high-performance explosives, the speed of detonation may only be slightly lower; Likewise, the function of the explosives must be guaranteed in the military temperature range from -35 ° C to + 63 ° C.

Furthermore, a preferred use of the explosive is to be shown.

The present object is achieved in that an electrically conductive structure consisting of ductile precious metal platelets is provided in the explosive, which platelets form galvanically conductive bridges around the explosive grains with a conductivity of at least 5 S m / mm 2.

The noble metal platelets mentioned in the patent claim are commercially available and are referred to in metallurgy as "tinsel".

In the unpressed state, a mixture of explosive grains and "tinsel" is not electrically conductive. Surprisingly, however, the explosive grains are plated during the pressing process and thereby form a reliably acting electrically conductive structure even with a small proportion of precious metal.

An explosive according to the invention permits novel designs of electrically fired ammunition bodies, in which no or only slightly functional electrical connection lines are necessary. In addition, the handling security of the systems increases due to the metal coating of the explosive grains.

The information according to claim 2 allows the selection of particularly suitable platelets.

Alternatively, gold, according to claim 3, can be used, albeit with higher economic outlay.

The hardness values specified in claims 2 and 3 are measured according to BRINELL and ensure sufficient ductile behavior on commercially available explosive grains; they are thus properly clad when pressed.

Best results were achieved with platelets of the same size, according to claim 4.

Platelets according to claim 5 are preferred, which are also commercially available.

In terms of a selection, the dimensions mentioned in claim 6 apply.

Surprisingly, the desired conductivity is already achieved by the small volume fractions listed in claim 7.

The method according to claim 8 is characterized by its particular simplicity and can be very easily integrated into existing manufacturing processes.

The use according to claim 9 ensures a flawless, distortion-free and delay-free transmission of the ignition signal without the Joule heat noticeably heating the explosive.

Although an explosive body according to the invention has only a slight reduction in performance compared to non-conductive explosives, this can be combined, in particular due to economic considerations, with conventional further high-performance explosive charges.

The subject matter of the invention is explained in more detail below with the aid of drawings.

Fig. 1

eine schematische Darstellung des leitenden Gefüges in einem galvanisch leitenden Sprengstoffkörper,

Fig. 2

eine Tandem-Hohlladung mit der Zündsignalübertragung dienenden galvanisch leitenden Sprengstoffkörpern.

Show it:

Fig. 1

1 shows a schematic representation of the conductive structure in a galvanically conductive explosive body,

Fig. 2

a tandem shaped charge with the galvanically conductive explosive bodies serving to transmit the ignition signal.

• 1. Beispielsweise Herstellung eines galvanisch leitenden Sprengstoffkörpers
  • 1a. Mischungskomponenten:
    Handelsüblicher Sprengstoff (Octogen, Klasse C; Firma DYNO, Norwegen) wird mit handelsüblichen Silberplättchen (Silber-Flakes; Firma DORAL, Vétroz, Schweiz) und handelsüblichem Bindemittel (Binder Octastit VIII L; Firma DYNO, Norwegen) zu leitfähigem Sprengstoff verarbeitet.
  • 1b. Mischungsverhältnisse:
    86,7 Gew.-% Sprengstoffkörner mit einer Kristalldichte von 1,903 g/cm³ werden mit 10,7 Gew.-% Silberplättchen mit einem Durchmesser von 40 µm und einer mittleren Dicke von 0,4 µm und mit 2,6 Gew.-% Bindemittel verwendet.
  • 1c. Verfahrensschritte:
    In einem ersten Schritt werden die Silberplättchen mit dem Binder in einem Mischer durch einen üblichen Rührer miteinander homogen vermischt. In einem zweiten Verfahrensschritt wird das mit Silberplättchen beladene Bindemittel in einem Trommelmischer auf die Sprengstoffkörner aufgebracht und getrocknet. In diesem Zustand ist die Mischung nicht leitfähig.
    Anschliessend wird der Sprengstoff in einer bekannten Pressform (vgl. EP -A1- 0 296 099) in seine Rohform gepresst; jetzt ist der derart erzeugte Körper galvanisch leitend.
• 2. Messergebnisse
  Zylindrische Sprengstoffpresskörper von 21 mm Durchmesser und 15 mm Länge wurden untersucht. Dabei wurde festgestellt, dass der als relevant zu betrachtende Durchgangswiderstand bei Kontaktflächen von 5 mm² und einem Kontaktabstand von 10 mm unterhalb von 3 Ohm liegt.
  Die Detonationsgeschwindigkeit übersteigt 8370 m/s.
  In bezug auf die Druckfestigkeit der Presskörper konnten keine wesentlichen Unterschiede zu nicht leitenden Körpern festgestellt werden.
• 3. Empfindlichkeit
  Reibempfindlichkeit (gemessen mit Apparat PETERS): Bei 8 kg Belastung wurde keine Wirkung erzielt; bei 10,8 kg wurde ein Knistern festgestellt; bei 12,0 kg Belastung entstanden "Anbrenner".
  Funkenentladungsempfindlichkeit (gemessen mit Apparatur GRD):
  Bei 18 mJ Funkenenergie war keine Wirkung ersichtlich; bei 56 mJ wurden sehr schwache "Anbrenner" feststellbar. Schlagempfindlichkeit (Fallhammerprüfung nach KOENEN und IDE):
  Bei 25 cm Fallhöhe war keine Wirkung vorhanden; bei 30 cm Fallhöhe wurden "Anbrenner" feststellbar.
• 4. Thermische Stabilität
  DSC/TG-Messungen (Differential Scanning Calorimetry/Thermo Gravimetry):
  Die DSC/TG-Kurven decken sich mit denjenigen von nicht leitendem Sprengstoff, dh. der Zusatz von Silber beeinflusst die thermische Zersetzung nicht.
• 5. Edelmetallanteil im Sprengstoff
  Ein für technische Anwendung geeigneter spezifischer Widerstand von 3 x 10⁻⁴ Ωcm wurde mit einem Anteil von 2% Silber am Gesamtvolumen erzielt. Mit 1% Volumenanteil Silber resultierte ein spezifischer Widerstand von 10 x 10⁻⁴ Ωcm; mit 3 Volumen-% Silber wurde, ein solcher von 0,18 x 10⁻⁴ Ωcm erreicht.

The illustration in FIG. 1 is a drawing converted from a scanning microscope image. With 1 precious metal platelets are designated which plate explosive grains 2. The cavities between the individual explosive grains 2 are partially filled with binder 3.

• 1. For example, production of a galvanically conductive explosive device
  • 1a. Mix components:
    Commercial explosives (Octogen, class C; DYNO, Norway) are processed with commercially available silver flakes (silver flakes; DORAL, Vétroz, Switzerland) and commercial binders (Binder Octastit VIII L; DYNO, Norway) to form conductive explosives.
  • 1b. Mixing ratios:
    86.7% by weight of explosive grains with a crystal density of 1.903 g / cm³ are mixed with 10.7% by weight of silver plates with a diameter of 40 µm and an average thickness of 0.4 µm and with 2.6% by weight Binder used.
  • 1c. Process steps:
    In a first step, the silver plates with the binder are homogeneously mixed with one another in a mixer using a conventional stirrer. In a second process step, the binder loaded with silver flakes is applied to the explosive grains in a drum mixer and dried. The mixture is not conductive in this state.
    The explosive is then pressed into its raw form in a known press mold (cf. EP-A1-0 296 099); now the body created in this way is electrically conductive.
• 2. Measurement results
  Cylindrical explosive compacts with a diameter of 21 mm and a length of 15 mm were examined. It was found that the volume resistance to be considered relevant for contact areas of 5 mm² and a contact distance of 10 mm is below 3 ohms.
  The detonation speed exceeds 8370 m / s.
  With regard to the compressive strength of the pressed bodies, no significant differences to non-conductive bodies could be determined.
• 3. Sensitivity
  Sensitivity to friction (measured with PETERS apparatus): No effect was achieved with a load of 8 kg; crackling was noted at 10.8 kg; at 12.0 kg load "burners" were created.
  Spark discharge sensitivity (measured with GRD equipment):
  No effect was evident at 18 mJ spark energy; very weak "burners" were found at 56 mJ. Impact sensitivity (drop hammer test according to KOENEN and IDE):
  At a height of 25 cm there was no effect; "Burners" were found at a fall height of 30 cm.
• 4. Thermal stability
  DSC / TG measurements (Differential Scanning Calorimetry / Thermo Gravimetry):
  The DSC / TG curves coincide with those of non-conductive explosives, ie. the addition of silver does not affect the thermal decomposition.
• 5. Precious metal content in the explosives
  A specific resistance of 3 x 10⁻⁴ Ωcm suitable for technical applications was achieved with a share of 2% silver in the total volume. With 1% by volume silver, a specific resistance of 10 x 10⁻⁴ Ωcm resulted; with 3% by volume of silver, one of 0.18 x 10⁻⁴ Ωcm was achieved.

• 5a. Gold-Plättchen im Sprengstoff
  Eine alternative Ausführung mit im Handel erhältlichen Goldplättchen (Gold-Flakes; Firma DEMETRON, Hanau, Deutschland), in handelsüblichem Sprengstoff (Octogen C, Firma DYNO, Norwegen) und einem entsprechenden Bindemittel (Octastit VIII L), wurde untersucht.
  In 80,2 Gew.-% Sprengstoff, mit einer Kristalldichte von 1,903 g/cm³ wurden 17,4 Gew.-% Goldplättchen, mit einem mittleren Durchmesser von 7,8 µm, bei einer mittleren Dicke von 0,4 µm, mit 2,4 Gew.-% Binder vermengt.
  Der in analoger Weise hergestellte Sprengstoffkörper wies einen spezifischen Widerstand auf, der bis zu 25 % höher war als im Ausführungsbeispiel mit Silber. Demzufolge, wurde aus praktischen und wirtschaftlichen Gründen diese Variante nicht weiterverfolgt.

Similar relationships apply to other precious metals.

• 5a. Gold tokens in the explosives
  An alternative version with commercially available gold flakes (gold flakes; DEMETRON, Hanau, Germany), in commercially available explosives (Octogen C, DYNO, Norway) and a corresponding binder (Octastit VIII L) was investigated.
  In 80.2% by weight of explosive, with a crystal density of 1.903 g / cm³, 17.4% by weight of gold platelets, with an average diameter of 7.8 µm, with an average thickness of 0.4 µm, were mixed with 2 , 4 wt .-% binder mixed.
  The explosive body produced in an analogous manner had a specific resistance which was up to 25% higher than in the exemplary embodiment with silver. As a result, this variant was not pursued for practical and economic reasons.

• 6. Anwendungsbeispiel
  In Fig. 2 ist eine Tandem-Hohlladung dargestellt, welche galvanisch leitende Sprengstoffkörper verwendet, um den Hohlladungsstrahl störende elektrische Verbindungsleitungen zu eliminieren. Damit konnte gleichzeitig der konstruktive Aufbau gegenüber dem Bekannten vereinfacht werden: Ein Gehäuse 10 ist in an sich bekannter Weise partiell durch ein Teil 10' einer Doppelhaube gebildet. Im Innern befindet sich frontseitig ein als Kalotte ausgebildetes, gegenüber dem äusseren Teil 10' der Doppelhaube durch einen Luftspalt isoliertes, weiteres Teil 11 der Doppelhaube. Die Doppelhaube dient in bekannter Weise einer Aufschlagkontaktierung, d.h. der Initiierung des Zündsignals.
  Eine frontseitige Auskleidung ist auf einem elektrisch leitenden Sprengstoffkörper 13, eine Frontladung, formschlüssig aufgesetzt. Gegenüber dem Gehäuse 10 ist der Sprengstoffkörper 13 durch eine Isolations- und Zentrierbüchse 16 beabstandet. Rückseitig befindet sich am Sprengstoffkörper 13 ein erster Zünder 14, welcher mit einer Vorladung 15 versehen ist und in einer Isolationsscheibe 17 zentral gehalten ist.
  Eine Dämmbüchse 18, aus Kunststoff, dient der Schockisolation und ist im Raum unterhalb des Sprengstoffkörpers 13, in an sich bekannter Weise vorgesehen. Über eine Verbindungsleitung 19 ist ein zweites inneres, kalottenförmiges Teil 20 einer weiteren, zur ersten parallel geschalteten Doppelhaube mit einem Verbindungsflansch 21 zentriert. Eine heckseitige Auskleidung 22 liegt auf einer Hauptladung 23; am Kegelstumpf der Auskleidung 22 ist ein weiterer elektrisch leitender Sprengstoffkörper 24 aufgesetzt, der durch einen hier nicht dargestellten elektrischen Kontakt mit einer in einer inerten Linse 25 zentrierten Verstärkungsladung 27 (Booster) galvanisch verbunden ist. Eine zusätzliche Heckladung 26 umschliesst die inerte Linse 25 in ihrem Endbereich.
  In einem Leitwerkflansch 29 wird ein üblicher Zünder 28 mit Zündgenerator eingesetzt und durch ein hier nicht dargestelltes Leitwerk einsatzfähig.

Relatively hard alloys such as silver / copper alloys with 2% by weight copper or generally base metals have proven even less successful.

• 6. Application example
  2 shows a tandem shaped charge which uses galvanically conductive explosive bodies in order to eliminate electrical connecting lines which disrupt the shaped charge beam. At the same time, the structural design could be simplified compared to the known: A housing 10 is partially formed in a manner known per se by a part 10 'of a double hood. On the inside there is a further part 11 of the double hood, which is designed as a spherical cap and is insulated from the outer part 10 'of the double hood by an air gap. The double hood is used in a known manner to make contact, ie to initiate the ignition signal.
  A front lining is positively placed on an electrically conductive explosive body 13, a front load. Compared to the housing 10, the explosive body 13 is spaced apart by an insulation and centering sleeve 16. On the back of the explosive body 13 there is a first detonator 14, which is provided with a precharge 15 and is held centrally in an insulation disk 17.
  An insulating sleeve 18, made of plastic, is used for shock insulation and is provided in the space below the explosive body 13 in a manner known per se. A second inner, dome-shaped part 20 of a further double hood connected in parallel to the first with a connecting flange 21 is centered via a connecting line 19. A rear lining 22 lies on a main load 23; A further electrically conductive explosive body 24 is attached to the truncated cone of the lining 22 and is electrically connected to an intensifying charge 27 (booster) centered in an inert lens 25 by an electrical contact (not shown here). An additional rear load 26 encloses the inert lens 25 in its end region.
  A conventional igniter 28 with an ignition generator is used in an empennage flange 29 and can be used by an empennage not shown here.

The structural design and the components used here are known as such; The use of galvanically conductive explosive bodies means that the ammunition body is more powerful than comparable constructions, since no disruptive metal parts or connecting lines influence the shaped charge jets in their sensitive areas.

Of course, the subject of the invention is not limited to military applications; it can be combined in simple and very compact combinations with electrical and electronic circuits, particularly in safety technology. The conductivity, which is 10³ better than that of graphite-containing explosives, ensures a high level of functional reliability of such constructions.

Claims (10)

1. A compression-moulded, metal-containing explosive, characterised in that an electrically conductive structure comprising ductile noble-metal laminae (1) is provided in the explosive, the said laminae (1) forming galvanically conductive bridges, having a conductivity of at least 5 S m/mm², around the explosive grains (2).
2. An explosive according to claim 1, characterised in that the noble metal is silver or a silver alloy and has a hardness of not more than 32 kg/mm².
3. An explosive according to claim 1, characterised in that the noble metal is gold or a gold alloy and has a hardness of not more than 20 kg/mm².
4. An explosive according to claims 1 and 2, characterised in that the laminae (1) have defined geometric shapes and sizes.
5. An explosive according to claim 4, characterised in that the laminae (1) have a spherical or cylindrical shape.
6. An explosive according to claims 2 and 5, characterised in that the laminae (1) have a diameter of 5 µm to 100 µm and a thickness of 0.05 µm to 10 µm.
7. An explosive according to claims 1 to 5, characterised in that the proportion of noble-metal laminae (1) in the explosive is 1 vol.% to 3 vol.%.
8. A process for the preparation of an explosive according to any one of claims 1 to 7, characterised in that in a first process step the noble-metal laminae are homogeneously mixed with a binder in a first mixer, in that in a second process step the binder is applied to the explosive grains and dried in a second mixer, and in that a press is then filled with the explosive grains and the explosive is compressed into its crude form.
9. A use of the explosive according to claim 1 in a piece of ammunition for at least partially forming a pole of a signal and/or explosive train.
10. A use of the explosive according to claim 9 in a precision explosive charge, the said explosive being positively surrounded by at least one further high-powered explosive charge.

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