DE102013016736A1 - Multilayer running systems with improved thermal conductivity and rigidity - Google Patents

Abstract

The present invention describes multilayer running systems which increase the stiffness and cadence of the runs at the same or slightly increased weight. The layers are characterized by the fact that from inside to outside, the thermal conductivity remains constant or increases, so that no layer has an insulating effect.

Description

It is currently known that runs are mainly made homogeneously from metal alloys, in particular steels (iron alloys) and nickel alloys. Runs must generally withstand the pressure of the propellant charge and have sufficient rigidity for adequate accuracy. This can be achieved, inter alia, by high wall thicknesses. As the wall thickness increases, both the maximum pressure that the barrel can withstand and the stiffness increase due to the increased diameter increase. However, these advantages are counteracted by the weight of the barrel, which should be as low as possible in order to enable good handling of the weapon. It is therefore advantageous to increase the diameter of the barrel without at the same time to increase its weight significantly or better not at all. In special cases, this is done by composite runs with a layer system of different materials. Examples of this are runs, which have a pulled core with a thin wall and are wrapped with fiber composites, such. In the patents CA 2284893 C and WO 2011146144 A2 shown. Usually, carbon fiber composites (CFRP) with a resin matrix based on epoxides are used. Since CFRP materials usually have a higher specific tensile strength than steels and nickel alloys, the wound running system can save weight compared to homogeneous metal runs. The disadvantage of these systems is their low temperature stability, which limits their use in semi-automatic and fully automatic weapons to a few shots or is only possible if the temperature of the barrel permanently do not exceed temperatures of 100 ° C and in particular no temperatures above 200 ° C. to reach. Other runs, which consist of different materials are the smooth-tube guns, which z. B. in Abrams and Leopard II tanks are used. These barrels have an insulating outer layer that serves thermal management and, unlike the wound barrels, has no direct impact on the mechanical integrity of the running system. An alternative form of multilayer composite run is in patent US 2011/0113667 A1 shown. The rigidity of the barrel is increased by an outer shell and to provide the gap with a light filling matrix. Unfortunately, that's in patent US 2011/0113667 A1 system shown massive deficiencies, since the filling materials described are poor heat-conducting, so form heat build-up and the heaves warped under heat load. A use of the system in fully and semi-automatic weapons is not possible because the cadence would have to be reduced for a permanent use.

The present patent "Multilayer Running System with Improved Thermal Conductivity and Stiffness" addresses these problems in terms of thermal properties, through the use of innovative combinations of materials that enable targeted thermal management while maintaining low cost. So it is possible to use the presented multi-layer running systems for semi and fully automatic weapons. The running system consists of a core, in the simplest case turned down to minimum wall thickness steel barrel, which is surrounded by a metallic sleeve. The space between the sleeve and core is filled with a chemically setting material (matrix), which produces a frictional connection between the sleeve and core. This has the advantage of increasing the rigidity of the barrel through the increased diameter of the system to allow for more accurate shots. In the simplest case, the matrix is based on cement, gypsum, waterglass or mixtures of these materials which are provided with additives for adapting the thermal conductivity, the linear thermal expansion coefficient and the modulus of elasticity.

Non-metallic compounds with a thermal conductivity between 20 and 9000 W / m · K are suitable for adjusting the thermal conductivity, such as diamond, boron nitride, carbon nanotubes, silicon carbide, graphite, graphenes, graphene nanoplates, but highly conductive metals such as gold, silver, platinum, rhodium , Tungsten, copper or aluminum or correspondingly conductive alloys and metal-matrix compounds of them. These supplements should be in a range of between 1 to 90 percent by weight and percent by volume, but preferably in the range of 2 to 20 percent by volume. Here are particularly material forms with a high aspect ratio of at least 1: 5 (width / diameter to length), but better 1:50 and in particular over 1:50 to prefer, so fibers and whiskers such. As in boron nitride, carbon nanotubes and silicon carbide, since they are more easily overlapped by the ability to form thermal bridges.

To adjust the thermal expansion are used in particular calcium carbonate and calcium oxide in crystalline, semi-crystalline or amorphous form as well as aluminosilicate compound such. But not exclusively Feldspäte, in just these forms. To adjust the coefficient of thermal expansion, preference is given to powders having a particle size of not more than 100 μm, preferably less than 100 μm, and more preferably in the range from 5 to 0.05 μm. In contrast to the additions for the adjustment of the thermal conductivity, the additives for the thermal expansion can have a low aspect ratio. Boron nitride can be used as a supplement to this connection at the same time Increase of the thermal conductivity and the thermal expansion coefficient serve.

The pourable matrix mixtures based on cement, gypsum and water glass are placed in the intermediate space of the sleeve and core and curing there. As an alternative to chemical bonding, matrix materials in powder form can be placed in the intermediate space of sleeve and core and pressed. The separate preparation of the matrix shell by the above-mentioned production methods is possible, as well as the production of a sintered matrix shell, as long as it meets the requirements mentioned in claims 4, 5 and 8. In this case, the parts are pressed into each other and / or produced by different temperatures of the core and matrix coat a sufficiently large slip, which makes it possible to add the components. Upon reaching the same temperature, the parts form a frictional no longer releasable connection. According to the aforementioned method, the outer jacket sleeve is applied. If the matrix jacket has sufficient rigidity, so that there is an increase in the rigidity of the running system in comparison with a full-metal run, the jacket sleeve can be dispensed with. This is u. a. in the sintered matrices on the basis of boron nitride and silicon carbide possible, as described in the section "Examples".

In addition to providing a positive connection between the core and outer shell without reducing the heat conduction to the outer surface of the system for cooling, the matrix jacket serves to increase the specific heat capacity of the system. The increased heat capacity allows a slower heating of the running system compared to pure metal runs, which in turn allows a higher firing frequency (cadence). Cement, gypsum, and waterglass-based matrices have a nearly twice the specific heat capacity of steels, allowing the cadence to increase by at least a factor of two. Also, the outer mantle may help if the material is chosen appropriately, e.g. B. consists of aluminum.

With a suitable choice of materials and layer thicknesses, increases in the stiffness and heat capacity of the running system are possible by factors between 12 to 14, but mostly in the range of factors 2 to 7, with at the same time only a minimal increase in weight (usually less than 20%). The exact values depend on the thickness and materials of the layers and the comparative run. The above-mentioned running systems generally allow an improvement in the accuracy by at least a factor of two while simultaneously increasing the cadence by a factor of two, usually even by a factor of 4. It can also be emphasized here that the duration of use is increased if the cadence is not completely exhausted , If, for example, the maximum cadence is increased by a factor of 4, but only twice the cadence is fired, it can be fired twice until the critical temperature at which the run fails. This is because the heat energy that can be taken to run to failure is increased by the layer system and is proportional to the product of cadence and firing time. Accordingly, either cadence or duration of fire or cadence and duration of fire can be increased.

However, the increased diameter of the barrel and the materials used cause both the surface area to volume ratio to be lowered and the heat storage capacity of the system to be increased. This leads to a lower cooling efficiency of the system, which can optionally be countered by a suitable surface structure (vulgo cooling fins), which increases the surface to an extent as the surface-to-volume ratio is lowered and the heat capacity is increased. In most cases, the surface must be increased by a factor of 3 to 4, d. H. in a cylindrical run with triangular structuring, setting an edge of length 3-4 on the triangle base of length 1. In this context, the relevant only the ratio and not the absolute size, so that the increase in the surface is preferably done by a microstructuring.

The runs thus produced are particularly useful in fully and semi-automatic weapons such. B. rifles and cannons. But also in repeating rifles and shotguns they have advantages through the increased accuracy of the shots. In thermally highly loaded single fire systems such as mortars they allow higher firing sequences and longer operating times.

Examples

Standard matrix mixtures pourable

• 90% vol. Gypsum or cement with 10% vol. Carbon nanotubes (CNTs)
• Thermal conductivity ≈ 65 to 90 W / m · K depending on the purity and type of CNTs (multi- or singlewall)
• Thermal expansion coefficient ≈ 9 ppm / K
• 85% vol. Portland cement, 5% vol. Gypsum, 10% vol. Carbon nanotubes
• Thermal conductivity ≈ 67 W / m · K
• Thermal expansion coefficient ≈ 9 ppm / K
• 85% vol. Portland cement, 10% vol. Boron nitride, 5% vol. Carbon nanotubes
• Thermal conductivity ≈ 78 W / m · K
• Thermal expansion coefficient ≈ 11
• 85% vol. Portland cement, 5% vol. Calcium carbonate, 10% vol. Carbon nanotubes
• Thermal conductivity ≈ 67 W / m · K
• Thermal expansion coefficient ≈ 12.5
• 55% Portland cement, 35% water glass, 10% vol. Carbon nanotubes
• Thermal conductivity ≈ 67 W / m · K
• Thermal expansion coefficient ≈ 6

Pressed matrix

• Diamond dust thermal conductivity between 500-1800 W / m · K depending on diamond content and pressing aids

Sintered matrix

• Silicon carbide thermal conductivity between 80-350 W / m · K depending on porosity and sintering degree boron nitride thermal conductivity between 500-1800 W / m · K depending on porosity and degree of sintering

Metal-ceramic matrix

• Boron nitride with 40% aluminum thermal conductivity between 800-1200 W / m · K, depending on the porosity and thermal conductivity of the aluminum alloy used

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• CA 2284893 C [0001]
• WO 2011146144 A2 [0001]
• US 2011/0113667 A1 [0001, 0001]

Claims (10)

Running systems characterized in that they consist of several layers of different materials and the heat conductivity increases from inside to outside per layer or remains constant, so that from inside to outside no layer with low thermal conductivity follows a layer with higher thermal conductivity. Multilayer running systems characterized in that all layers can be used permanently above 100 ° C, without losing mechanical stability and weigh no more than 50% than a comparable fully metallic runs. Running systems characterized in that they consist of a metal or metal-ceramic core with barrel bore (core) and have at least one further non-metallic layer (matrix cladding), but preferably two further layers. In the case of three layers inside is the core, followed by the matrix cladding and the outer cladding, which may be metallic or a metal matrix material. Multilayer running systems characterized in that the above-mentioned matrix shell material has a thermal conductivity between 2 and 400 W / m · K, but preferably between 20 and 100 W / m · K and particularly preferably has a thermal conductivity which is greater than or equal to that of the core. Multilayer running systems characterized in that the matrix cladding which follows the core is chemically or physically bonded and contains at least one of the following materials: boron nitride, silicon carbide, copper, aluminum, gold, silver, carbon nanotubes, graphite, graphite nanoplates, beryllium oxide, diamond, Aluminum nitrides, platinum, rhodium, palladium. Silicon, magnesium, brass, tungsten or alloys of said metals or metal-ceramic composites of said materials. Multilayer running systems characterized in that the second layer around the core has a specific heat capacity greater than or equal to that of the core and the specific heat capacity of the system is greater than that of a comparable fully metallic barrel. Multilayer running systems, characterized in that, if there are more than two layers in the system, the layer or layers increase the rigidity of the system by at least 10% compared to the core. Multilayer running systems characterized in that the thermal expansion coefficients of the layers differ by no more than a factor of 2.5, but preferably less differ from each other. Multilayer running systems characterized in that the outermost layer may have a surface structure which serves to increase the passive heat transfer to the environment. Multilayer running systems characterized in that cadence or duration of fire or cadence and duration of fire are increased.