SE470211B - Methods of adding exothermic reactive metal additives to explosives and explosives prepared accordingly - Google Patents

Description

.ÅÉIS -: 1 c: permit. Examples of ductile metals are aluminum, titanium and nickel. Although the term mechanical alloys denotes a co-milled or co-rolled product consisting of two or more metals, the term is not completely irrelevant because even at least heavy metals, ie metals heavier than iron which form molten phase alloys with each other are usually not dissolved in each other other than within relatively narrow temperature ranges and outside these precipitate in the form of fine adjacent crystals. The mechanical alloys have in principle the same type of microstructure as such melt phase alloys, with the difference that they are obtained in finely divided form.

When grinding or rolling together the components included in a mechanical alloy, you first get a crushing of the constituent particles which gives an increasingly fine-grained product which, however, after a particle minimum begins to form agglomerates as fine particles of the constituent materials begin baked together into composite particles. Although these composite particles will initially be crushed, if no special measures are taken, a gradual welding between the components included in the agglomerates will take place as the temperature in the aggregate rises to the welding temperature of the components.

Through this mutual welding, you thus get a successive material build-up of increasingly harder and larger and more difficult-to-crush particles, which also results in a successive material build-up on the inside of the grinding equipment.

In the present new field of application for certain specific mechanical alloys, it is definitely not desirable to effect any such local welding between the particles within the mechanical alloy, however, an agglomerate formation is desirable within certain limits. The welding must be avoided because it is the energy additions that are obtained when the components included in the mechanical alloy react exothermically with each other to form a melt phase alloy which we wish to use. In order to be able to make the greatest possible use of the new field of application of the mechanical alloys according to the invention, it is therefore important to produce these mechanical alloys with the least possible welding between the particles contained therein and comprising two or more metal components and possibly carbon. forming common melt phase alloys react exothermically with each other. The property that we in accordance with the invention wish to utilize in the mechanical alloys is thus the close contact of the various components with each other, while the combustion of the explosive gives the heat supplement which in turn starts the exothermic alloy reaction between the components in the mechanical alloy and this alloy reaction. thus in turn provides an energy supplement whose size depends on the components included in the mechanical alloy. The mechanical alloys are obtained in the form of granules which can have an average diameter of up to a few mm (1-2 mm) and a particle size of the sub-components contained therein of 1-5 μm.

As already indicated, the mechanical alloys in question in connection with the present invention must not be welded to any great extent. To prevent this from happening during the grinding or rolling process, certain specific additives can be added which form a liquid or solid material film over at least one of the particles of the constituent materials.

As such additives can be used certain alcohols, esters, amino fatty acids, glycols and waxes. These additives generally have to be chemically reactive, with at least one of the components included in the mechanical alloy. A good example of such an additive is stearic acid, which together with, for example, aluminum gives aluminum stearate and thus gives a very good protective film on, for example, aluminum. For the additives it also applies that these must be compatible with the explosives contained in the final "Dü- u .n _13 CD FJ ... s ... kx so the product. The amount of additives of the kind indicated above which must be added in the preparation of the The mechanical alloys used in accordance with the present invention will of course vary somewhat with respect to the type of additive, but it should generally not exceed 1% by weight based on all the components included in the mechanical alloy.The amount of maladditive must, however, to the greatest possible extent is minimized because its presence means that the metal components are separated by a thin material film which complicates the formation of the exothermic melt phase alloy formation.

In addition to the addition of additives of the type discussed above, the welding between the particles included in the mechanical alloys can be limited at least to some extent by the milling or rolling together taking place during continuous cooling.

A second way of preventing or at least limiting the welding between the metal particles in a mechanical alloy is to carry out the grinding or rolling in an inert grinding liquid such as water, glycols or possibly oils. In some cases the grinding or rolling may need to be carried out in a shielding gas (eg N2) atmosphere. From the finished mechanical alloy, the grinding fluid can then be removed by extraction. The use of a grinding liquid therefore does not have to exclude the addition of the grinding additives discussed above in the form of stearic acid. The use of grinding fluid and / or shielding gas atmosphere can be safety requirements in the production of such mechanical alloys that can easily give rise to fire or explosions.

The present invention thus relates to a new area of use for so-called mechanical alloys of the type defined above, namely as energy additives in explosives where, by being responsible for specific metal additives of the type described in SE-A-9003724-3 and SE-A-9003723 Which during the combustion of the explosive 478 QH give rise to exothermic temperature-increasing intermetallic alloy reactions.

Of the above-mentioned patent applications, the former describes the principles of these exothermic intermetallic alloy reactions in connection with explosives, while the second application relates to the same effects in rocket and ramjet fuels.

These two older patents describe how, by selecting suitable metal reactants involved in the explosive during their combustion, exothermic intermetallic alloy reactions can be produced which provide significant energy additions to the explosive combustion. Whether the combustion takes place as detonation or deflagration is irrelevant. In addition to the choice of metal reactants, these patents state as a requirement that these metal reactants must be atomized and in intimate contact with each other in the explosive. It is precisely this atomization and intimate contact between the constituent metal reactants that can be obtained by utilizing mechanical alloys.

The mechanical alloys not only offer metal particles of u-size they also provide access to metal mixtures consisting of several metal particles of this size which are rolled together into granules where the metal particles that are to react exothermically and intermetallically with each other during the explosive combustion also lie in principle at atomic distances from each other.

In the above-mentioned earlier patent applications, reference is made to such intermetallic alloy reactions which result in borides, aluminides, silicides, alloys comprising alkaline earth metals and carbides.

The last group of carbides becomes particularly interesting in connection with the present invention. Admittedly, it can be pointed out that a certain carbide formation is usually obtained in the combustion of an explosive substance using the carbon contained in the explosive, but with the present invention and the use of the The mechanical alloys are given completely new possibilities in that carbon in the form of graphite or carbon black can be included as one component in the mechanical alloy. The second component can then be, for example, aluminum. Because the mechanical alloys can be manufactured in optional proportions, the invention makes it possible to utilize the energy supplement from the exothermic aluminum-carbide formation reaction. Just as in connection with the above-mentioned older patent applications, it is mainly the metals titanium, boron, zirconium, nickel, manganese and aluminum and thus also carbon which are interesting in connection with the present invention and in this context with the addition that this is in form of mechanical alloys.

Examples of some explosives whose effect can be enhanced in the manner characteristic of the invention are HMM, RDX, PETN, TATB, NTO, HNS, TAGN, NIGU, guanidine nitrate, TNT and nitrocellulose.

Abbreviations commonly used in the industry and in industry: RDX = hexogen I HMX = octogenic HNS = hexanitrostilbene PETN = pentyl or pentaerythritol tetranitrate TATB = trinitroaminotrinitrobenzene NTO = 3-Nitro-1,2,4-Triazole-5-One TNT = triotamine TAGN NIGU = nitroguanidine In addition, all binders of both energetic and non-energetic type that are relevant in the context of explosives can be included.

All of the metal combinations defined in the above-mentioned older patent applications can also be actualized in connection with the present invention. In addition, carbon 7 4-70 2 ”i” í is also added here, which can really be seen here as an additional of the metals in question in this context for the formation of mechanical alloys.

In the above-mentioned older patent applications, the use of carbon is also mentioned as a component that is exothermically reactive in this context, but it refers to the carbon chemically bound in the explosive, which may be considered to be something completely different.

Borides Metal combinations, also mentioned in previously discussed older Swedish patent applications, may be relevant in connection with the present invention Alkaline earth metals Barium plus either, bismuth or tin.

Magnesium plus tin Calcium plus aluminum Strontium plus aluminum Beryllium plus aluminum Boron plus magnesium, carbon, silicon, titanium, zirconium, chromium, molybdenum, tungsten or manganese.

Aluminides Aluminum plus copper, calcium, boron, titanium or zirconium, chromium, manganese, iron, cobalt, nickel, palladium and platinum.

Carbides Carbon plus beryllium, calcium, strontium, barium, boron, aluminum.

Silicides Silicon plus calcium, carbon, titanium, zirconium, hafnium, chromium, molybdenum and nickel.

Furthermore, small additions of substances or alloys from the lanthanide group and / or the metal hafnium can be added to catalyze the alloying reaction according to the invention.

The present invention has been defined in the appended claims and it will now be further elucidated with the following more detailed reasoning.

Intermetallic Explosives (Theory and Practice) By calculating the effect of mixing with intermetallic reactants in high energy explosives, these mixtures will show a deteriorating theoretical energy yield as the amount of explosive decreases.

To exemplify this we can see the system RDX / Mn / Al. (Hexogen / Manganese / Aluminum) RDX (Hexogen) contains a total of 1360 kcal / kg in energy, by adding (replacing) 40% of RDX with the alloy metals Manganese and Aluminum, the total energy effect of the mixture will be reduced to 866 kcal / kg.

The same applies to boron and zirconium.

The alloy reaction Zr + 2B has a total energy of 690 kcal / kg, a 40% mixture gives a reduction of the system to 1092 kcal / kg.

Despite this, experimental results show that the effect of explosive mixtures with elements of alloy metals of the kind mentioned above gives an increased impact effect on e.g. steel plate. This fact can be explained in two ways: - In theoretical calculations, no account will be taken of the time factor. The time factor for exothermic alloy reactions can give 4 470 211 favorable effects on breakthroughs, ie because metal combinations are present in and after the detonation zone, these will affect the temperature in the same, and increase the so-called residual effect.

- Metal combinations of type Mn / Al, B / Ti (Boron / Titanium etc. react in the detonation zone under normal conditions with reactants from the explosive, ie form oxides and carbides. This results in alloy reactions being largely absent. It is therefore important that the metals By having mechanically processed the metals together in advance, the condition is obtained to react the alloy reaction in the detonation zone and as a post-reaction.

By testing these systems the following results can be mentioned. The test method has been illustrated in the accompanying sketch where l is an electric detonator, 2 a dam in the form of a wooden block, 3 a test body of the explosive mixture to be tested, 4 a steel plate and 5 a wooden support.

In the investigation, test pads (3) with a diameter of 0 22 mm and a length of approx. 20 mm have been used. The initiation has been done with an electric detonator (1) type VA. The steel plate (4) used has a thickness of 8 mm.

Test blasting with hexal, ie 70% RDX and 30% Al, does not give an impact during the test, only crack formation in the plate is obtained. While a mixture of 50% RDX and Mn / Al mixture produces breakthroughs with a diameter of about: 4 mm.

Claims (10)

aim: to f ° PATENT REQUIREMENTS 1. In the case of explosive mixtures in which the energy exchange during their combustion by detonation or deflagration is increased by an intermetallic alloy reaction between reactants contained in the explosive mixture in the form of two or fls in a distributed form and in intimate contact with each other metal components involved in the explosive which as a final product gives a boride, an aluminide, a silicide, a zirconium-nickel alloy, an alloy containing at least one alkaline earth metal or a metal carbide and where this intermetallic alloy reaction is started by the explosive combustion and then runs more or less parallel to this without energy addition from it but during the release of energy characterized in that at least one of the constituent metal components is a ductile metal, i.e. it is malleable in the normal state and that all the constituents in the intermetallic alloy reaction are supplied as granules made from said metal. all components by rolling together or grinding fine particles thereof into a so-called mechanical alloy produced under such conditions that welding between the components contained therein is avoided as far as possible. 2. A method according to claim 1, characterized in that all components included in the intermetallic alloy reaction are supplied in the form of granules of these components made of mechanical alloy containing up to 2% by weight but preferably only up to 1% by weight of one with at least one of the components contained therein chemically reactive additive which during the production of the mechanical alloy prevented a local welding between particles of the various components. / l 117 Û Zäll 3. A method according to either of claims 1 or 2, characterized in that the components included in the intermetallic alloy reaction are supplied in the form of granules of a mechanical alloy with particle sizes up to 1 mm and in which sub-particles of the various components of the order of 1- 10 um. 4. A method according to any one of claims 1-3, characterized in that for the intermetallic alloy reaction a mechanical alloy comprising Bor and Titanium (B / Ti) is added. 5. A method according to any one of claims 1-3, characterized in that for the intermetallic alloying reaction a mechanical alloy comprising manganese and aluminum (Mn / Al) is added. Method according to either of Claims 1 to 3, characterized in that the actual mechanical alloy is produced by dry milling with the possible addition of grinding additives such as stearic acid, in which case corresponding to a maximum of 2% by weight of the grinding material and preferably a maximum of 1% thereof. 7. A method according to any one of claims 1-5, characterized in that the grinding is carried out as wet grinding in an inert grinding liquid. An explosive composition prepared according to the method of any one of claims 1 to 7 comprising at least one explosive and at least two atomized and in intimate contact with each other metal components involved in the explosive selected from a group comprising carbon, boron, aluminum, manganese, silicon, zirconium and nickel and alkaline earth metals characterized in that the metal components include at least one ductile metal, ie a metal which is malleable in the normal state and said metal components are included in the form of granules of so-called mechanical alloys of said metal components where the granules are composed of rolled or ground finer particles of respective metal components with the least possible welding between the particles. / í 4170 2 ”il Explosive composition according to claim 8, characterized in that the mechanical alloy comprises Boron and Titanium or manganese and aluminum. Explosive composition according to either of Claims 8 and 9, characterized in that at least the particles of one of the components contained in the granules of the mechanical alloy are covered by a liquid or solid film which during the production of the granules prevented a welding between the granules constituent finer particles.