Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B12/00—Projectiles, missiles or mines characterised by the warhead, the intended effect, or the material
  • F42B12/72—Projectiles, missiles or mines characterised by the warhead, the intended effect, or the material characterised by the material
  • F42B12/74—Projectiles, missiles or mines characterised by the warhead, the intended effect, or the material characterised by the material of the core or solid body
  • F42B12/745—Projectiles, missiles or mines characterised by the warhead, the intended effect, or the material characterised by the material of the core or solid body the core being made of plastics; Compounds or blends of plastics and other materials, e.g. fillers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B12/00—Projectiles, missiles or mines characterised by the warhead, the intended effect, or the material
  • F42B12/72—Projectiles, missiles or mines characterised by the warhead, the intended effect, or the material characterised by the material
  • F42B12/74—Projectiles, missiles or mines characterised by the warhead, the intended effect, or the material characterised by the material of the core or solid body

Definitions

• This invention relates generally to projectiles and more particularly to a lead free, ferromagnetic projectile.
• U.S. Patent Nos. 2,995,090 and 3,193,003 disclose frangible gallery bullets made of iron powder, a small amount of lead powder, and a thermoset resin. While substantially lead free, a drawback of these bullets is a density significantly less than that of a lead bullet.
• U.S. Patent No. 4,881,465 discloses a shot pellet made of lead and ferrotungsten, while U.S. Patent Nos. 4,850,278 and 4,939,996 disclose a projectile made of ceramic zirconium.
• U.S. Patent No. 4,005,660 discloses a polyethylene matrix which is filled with a metal powder such as bismuth, tantalum, nickel, and copper. Yet another frangible projectile is made of a polymeric material which is filled with metal or metal oxide.
• U.S. Patent No. 4,949,644 discloses shot made of bismuth or a bismuth alloy.
• bismuth is in short supply and considerably more expensive than lead.
• U.S. Patent No. 5,088,415 discloses a plastic covered lead shot. However, this shot material still contains lead, which upon backstop impact, will be exposed to the environment. Plated lead bullets and plastic coated lead bullets are also in use, but they have the same drawback, on target impact the lead is exposed creating difficulty in disposing of spent bullets. None of the prior bullets noted above has proved commercially viable, either due to cost, density differences, difficulty of mass production or difficulty of disposal. Accordingly, there remains a need for a projectile for target shooting ranges or for hunting use which is substantially lead free, performs ballistically similar to lead and facilitates reclamation of target backstops and range soil.
• a second object of the invention is for the projectile to have ballistic performance similar to lead.
• a third object of the invention is for the projectile to be easily removed from the shooting range soils and backstops.
• the projectile is a sintered composite having one or more, high density constituents selected from the group consisting of tungsten carbide, tungsten, ferrotungsten, cemented tungsten carbide alloys and carboloy (a tungsten carbide-cobalt sintered alloy, typically containing from 3% to 13% by weight cobalt) , and a second, lower density constituent selected to be a metallic matrix material such as tin, zinc, iron, nickel, cobalt and copper.
• the second constituent is a plastic matrix material such as a phenolic, epoxy, dialylphthalate, acrylic, polystyrene, polyethylene, or polyurethane.
• an effective amount, typically more than 50% by weight, of the projectile constituents are ferromagnetic.
• the composite projectile may contain a filler metal such as iron powder or zinc powder.
• the bullet of the invention comprises a solid body having a density of at least about 9 grams per cubic centimeter (80 percent that of pure lead) and a yield strength in compression greater than about 31 MPa (4500 psi) .
• constituents may be added in small amounts for special purposes such as enhancing frangibility. If iron is one constituent, the addition of carbon results in a brittle microstructure after a suitable heat treatment. Lubricants or solvents can be added to enhance powder flow properties, compaction properties and ease die release.
• ferrotungsten is ferromagnetic and has a density greater than that of lead.
• a ferrotungsten containing composite is economically feasible for projectiles and, by metallurgical and ballistic analysis, can be alloyed in proper amounts under proper conditions to become useful for a lead free bullet.
• FIG. 1 is a bar graph of densities of powder composites.
• FIG. 2 is a bar graph of the maximum engineering stress attained under compression with the powder composites.
• FIG. 3 is a bar graph of the total energy absorbed during compressive deformation to 20% strain or fracture.
• FIG. 4 is a bar graph showing the maximum stress at 20% compressive deformation.
• FIG. 5 is a bar graph showing the total energy absorbed in 20% compressive deformation or fracture of the bullets of FIG. 4.
• the bullet must closely approximate the recoil of a lead bullet when fired so that the shooter feels as though he is firing a standard lead bullet.
• the bullet must closely approximate the trajectory, i.e. exterior ballistics, of a lead bullet of the same caliber and weight so that the practice shooting is directly relevant to shooting in the field with an actual lead bullet.
• the bullet must not penetrate or damage the normal steel plate backstop on the target range and must not ricochet significantly.
• the bullet must remain intact during its travel through the gun barrel and while in flight.
• the bullet must not damage the gun barrel.
• the cost of the bullet must be reasonably comparable to other alternatives.
• the lead free bullet In order to meet the first two requirements, the lead free bullet must have approximately the same density as lead. This means that the bullet must have an overall density of at least 80% that of lead or 9 grams per cubic centimeter.
• the third requirement not penetrating or damaging the steel backstops at target shooting ranges, dictates that the bullet must either (1) deform at stresses lower than that sufficient to penetrate or severely damage the backstop, (2) fracture into small pieces at low stresses or (3) both deform and fracture at low stress.
• a typical 158 grain lead (10.3 gm, 0.0226 lb.) .38 Special bullet has a muzzle kinetic energy from a 10.2 cm (4 inch) barrel of 272 joules (200 foot pounds) and a density of 11.35 gm/cm 3 (0.41 pounds per cubic inch). This corresponds to an energy density of 296 joules/cm 3 (43,600 inch pounds per cubic inch).
• the deformable lead free bullet in accordance with the invention must absorb enough of this energy per unit volume as strain energy (elastic plus plastic) without imposing on the backstop stresses higher than the yield strength of mild steel, about 310 MPa (about 45,000 psi) in order for the bullet to stop without penetrating or severely damaging the target backstop.
• the fracture stress of the bullet must be below the stresses experienced by the bullet upon impact with the target backstop and below the yield strength of mild steel.
• the bullet of the invention may be coated with metal or plastic or jacketed in a conventional manner to protect the barrel.
• ferromagnetic materials are those metals, alloys and compounds of the transition (iron group) , rare-earth and actinide elements that, below the Curie temperature, have atomic magnet moments tending to line up in a common direction. These materials are characterized by a strong attraction to other magnetized materials.
• the weight percent of the ferromagnetic component is at least that effective to impart the sintered fragments of a spent projectile with ferromagnetic capability.
• the particles are then separated from the sand or other environment using magnetic separation techniques.
• the reclaimed projectile fragments can be further processed to separate the ferromagnetic constituent from the projectile matrix and any coating or jacket.
• separation may include mechanical crushing or grinding, or for polymer matrix, burning or chemically dissolving the matrix.
• Suitable ferromagnetic constituents for the high density first component include ferrotungsten and cemented tungsten carbide alloys having a ferromagnetic addition.
• Ferrotungsten is generally understood to be a tungsten base alloy that includes iron having a tungsten content by weight of from about 70% to about 85%.
• the carbon content of the ferrotungsten is less than about 0.6%.
• any tungsten base alloy containing iron that exhibits ferromagnetism is included.
• the ferrotungsten is present in a weight percent above about 50% and preferably from about 70% to 90% is preferred.
• suitable ferromagnetic constituents for the lower density second component include iron, nickel and cobalt. Iron is most preferred due to its low cost. Preferably, the iron is present in an amount of from about 10% to about 30% by weight.
• the metal matrix bullets in accordance with the preferred embodiments of the present invention are fabricated by powder metallurgical techniques. For the more frangible materials, the powders of the individual constituents are blended, compacted under pressure to near net shape, and sintered. If the bullets are jacketed, compacting and sintering can be done in the jacket or the bullets could be compacted and sintered before insertion into the jackets. If the bullets are coated, they would be coated after compacting and sintering.
• the proportions of the several powders required for a desired density is different than that calculated by the rule of mixtures because of the inability to eliminate all porosity. Porosity is compensated for by an appropriate increase in the amount of the higher density constituent, typically tungsten, ferrotungsten, carboloy, tungsten carbide or mixtures thereof. The optimum mixture is determined by the tradeoff between raw material cost and bullet performance.
• the bullets may be made by the above process or alternatively, compacted into rod or billet shapes using conventional pressing or isostatic pressing techniques. After sintering, the rod or billet could then be extruded into wire for fabrication into bullets by forging using punches and dies as is done with conventional lead bullets. Alternatively, if the materials are too brittle for such fabrication, conventional fabrication processes could be used to finish the bullet.
• the frangibility of the composite bullet can be enhanced through various processing steps.
• An optional heat treatment to embrittle the matrix enhances frangibility after final shape forming. For example, an iron matrix bullet having a carbon addition could be embrittled by suitable heat treatment.
• a tin matrix bullet could be embrittled by controlled tempering at a temperature where partial transformation to alpha tin occurs. Typically, this temperature is from about 375°C to about 575°C. This method can provide precise control of the degree of frangibility.
• a third method to enhance embrittlement is by selecting impurity additions such as bismuth in a copper matrix composite.
• the bullet may be heated to a temperature range where the impurity collects preferentially at grain boundaries.
• frangibility can be controlled by suitably varying the sintering time and/or sintering temperature.
• the composite projectile has a thermoplastic or thermosetting plastic matrix
• the metallic powders and polymer powders are blended as described considering mass and density requirements.
• the mixture is then formed into the final part by any conventional process used in of polymer technology such as injection molding, transfer molding.
• the composite bullets of the invention are preferably jacketed or coated with a soft metallic or plastic coating.
• the coatings is preferably tin, zinc, copper, brass or plastic.
• One suitable ferromagnetic jacket material is iron.
• plastic coatings are preferred.
• the plastic matrix and the coating are the same polymer.
• Plastic coatings may be applied by dipping, spraying, fluidized bed or other conventional plastic coating processes.
• the metallic coatings may be applied by electroplating, hot dipping or other conventional coating processes.
• Frangible plastic matrix composite bullets were made of tungsten powder with an average particle size of 6 microns. Iron powder was added to the tungsten powder at levels of 0, 15, and 30 percent by weight. After blending with one of two polymer powders, phenyl formaldehyde (Lucite) or polymethylmethalcrylate (Bakelite) which acted as the matrix, the mixtures were hot compacted at a temperature within the range of from about 149°C to about 177°C (300°F-350°F) and a pressure of about 241 MPa - 276 MPa (35-40 ksi) into 3.18 cm (1.25 inch) diameter cylinders which were then cut into rectangular parallelepipeds for compression testing and drop weight testing. In all, six (6) samples were made as shown in Table I below:
• Figure 1 shows the densities attained with metal matrix composites made of tungsten powder, tungsten carbide powder or ferrotungsten powder blended with powder of either tin, bismuth, zinc, iron (with 3% carbon) , aluminum, or copper.
• the proportions were such that they would have the density of lead if there was no porosity after sintering.
• the powders were cold compacted into 12.7 mm (half-inch) diameter cylinders using pressures of 690 MPa (100 ksi) . They were then sintered for two hours at appropriate temperatures, having been sealed in stainless steel bags.
• the sintering temperatures were (in degrees Celsius) 180, 251, 350, 900, 565, 900 respectively.
• Figure 2 shows the maximum axial internal stresses attained in the compression test.
• Figure 3 shows the energies absorbed up to 20 percent total strain (except for the copper tungsten compact which reached such high internal stresses that the test was stopped before 20 percent strain was achieved) . All of the materials exhibited some plastic deformation. The energy absorptions in the compression test indicate the relative ductilities, with the more energy absorbing materials being the most ductile.
• Figure 4 shows, for comparison, a lead slug, two standard 38 caliber bullets, and two commercial plastic matrix composite bullets tested in compression.
• Figure 4 shows that maximum stresses of the lead slug and lead bullets were significantly less than those of the plastic bullets. However, all were of the same order as those attained by the metal matrix samples in the iron free plastic matrix samples.
• Figure 5 shows the energy absorption for these materials. Values are generally less than that of the metal matrix samples shown in Figure 3 and much higher than that of the frangible plastic matrix samples.
• the ferromagnetic materials of the invention also can find utility in articles used to direct an explosive charge such as shaped charge liners and cones in oil well fields.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• General Engineering & Computer Science (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Hard Magnetic Materials (AREA)
• Liquid Crystal (AREA)
• Luminescent Compositions (AREA)
• Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)

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• 1995
  • 1995-10-02 EP EP95935118A patent/EP0787277A4/de not_active Withdrawn
  • 1995-10-02 WO PCT/US1995/012267 patent/WO1996012154A1/en not_active Ceased
  • 1995-10-02 CA CA002202632A patent/CA2202632A1/en not_active Abandoned
  • 1995-10-17 ZA ZA958771A patent/ZA958771B/xx unknown
  • 1995-10-17 IL IL11564795A patent/IL115647A0/xx unknown

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