Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B7/00—Shotgun ammunition
  • F42B7/02—Cartridges, i.e. cases with propellant charge and missile
  • F42B7/04—Cartridges, i.e. cases with propellant charge and missile of pellet type
  • F42B7/046—Pellets or shot therefor
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49712—Ball making

Definitions

• the present invention relates to a method of manufacturing steel projectiles, such as balls, for hunting cartridges as a substitute for traditional lead shots.
• the invention also relates to steel projectiles and cartridges obtained by the method.
• the load of a cartridge consists of spherical balls with not only a tolerance on the diameter of about 0.1 mm, but still a tight tolerance on the weight to ensure a reproducible ballistic behavior and ensure a constant loading of the cartridge which is done by volumetric measurement.
• the steel balls must undergo a surface treatment such as copper plating, addition of graphite, etc., in order to avoid any agglomeration of the charge which could be detrimental to good dispersion.
• the hardness should be as low as possible and not exceed 110 HV 10 surface and 100 HV 10 heart.
• - granulation with water a jet of steel is cast BOUS a jet of water at high pressure or directly into a tank.
• the size of the particles obtained is variable (from 1 to a few millimeters according to the technique), but the common characteristic of these is the irregular, non-spherical shape of the product;
• Steam granulation this process, developed in particular by Mintek (South Africa), uses a jet of water vapor, which makes it possible to avoid a too violent mechanical disturbance of the metal jet. This type of process involves the appearance of a size dispersion due to the absence of sphericity, which leads to the loss of part of the production.
• a hash system of the liquid metal flow is for example dispersed on a turntable before being subjected to the final granulation with water or steam.
• the wire used is of the ULC type, for example with a carbon content of 0.02% C.
• This type of thread is very expensive and very little available, if we consider the quantities to be produced in the field of hunting cartridges.
• the advantage of the yarn is that the utilization efficiency of the production is 100%. In flat steels, mild steels are much more available, including different thicknesses, which therefore correspond to different ball diameters. Unfortunately, part of the production is also unusable in this case, given the falls.
• powder metallurgy To manufacture some metal parts, generally complex shape is used powder metallurgy. It consists of compacting the powder in a mold and subjecting the assembly to a sintering operation at high temperature.
• Some tungsten carbide spheres are particularly prepared by this technique. From iron powder, it is conceivable to examine the possibility of obtaining extra-mild steel balls by a compaction / sintering process.
• WO-A-00/44517 discloses a projectile and a related manufacturing process of relatively high carbon steel (up to 1.5% C), produced by water atomization and annealed softened in a non-oxidizing atmosphere with a controlled dew point, at a temperature of between 600 and 1200 ⁇ C, to make it suitable for ballistic use.
• Softening results mainly from surface decarburization, preferably with an average Knoop surface hardness of less than 225 (Vickers surface hardness at least greater than 130).
• the present invention aims to provide a solution that does not have the disadvantages of the state of the art.
• the invention aims to provide a treatment from a current steel grade to obtain a final hardness less than 100 HV 10.
• an object of the invention is to provide this treatment to obtain a low hardness on steel balls, evenly over their entire volume (heart).
• An additional object of the invention is to eliminate a certain propensity for ricochets, usually inherent to steel projectiles.
• An additional object of the invention is to allow the manufacture of balls having a good sphericity.
• a first object of the present invention relates to a method of manufacturing a steel or iron projectile for a hunting cartridge or sporting shot in order to give it a hardness of between between 40 HV 10 and 110 HV 10 at room temperature, preferably between 40 HV 10 and 85 HV 10, characterized at least by the following successive steps:
• liquid metal whose carbon content is between 0.8 and 4.0% C by weight, preferably between 0.8 and 2.0, is used. % C by weight;
• the liquid metal is cast in a granulation process with water or steam to obtain spheroidal steel particles
• said particles are subjected to a thermal treatment for softening the solidified metal by graphitization while remaining in the ferritic domain;
• these particles are optionally subjected to a surface coating treatment.
• the softening heat treatment comprises at least the following successive steps:
• said metal is annealed for approximately 3 minutes from the ambient temperature to a temperature greater than
• said steel is cooled with water, preferably with boiling water, at a rate of at least 20 ° C./sec until it reaches room temperature; - is carried income said metal, under non-oxidizing atmosphere or slightly reducing type HNX to a temperature below 700 0 C, preferably below 65O 0 C; said metal is maintained under the aforementioned atmosphere at this latter temperature for a period of between 1 and 6 days, preferably between 1 and 4 days. Maintaining the method of the invention in a non-oxidizing atmosphere is mandatory to avoid decarburization of the processes of the state of the art.
• the metal further comprises, expressed by weight, maximum 0.4% Mn, between 0.1 and maximum 2.0% Si, maximum 2.0% A1, maximum 0.04% P, maximum 0 , 04% S, maximum 1% of other alloying elements, the balance consisting of iron and usual impurities.
• Silicon or aluminum in appropriate amounts confer a complementary inoculant effect insofar as they both increase the precipitating force of the graphite, thus reducing the graphitization time, without the presence of residual cementite.
• the granulation step with water or steam is performed in the presence of a surfactant.
• the granulation step with water or steam is preceded by a step of hashing the flow of liquid metal.
• the step of hashing the flow of liquid metal is performed by means of a turntable.
• the turntable is a plate made of a material that is not wetted by the liquid steel such as zirconia, alumina, boron nitride or syalon.
• the turntable is a perforated tray.
• the granulation step with water or steam is replaced by a sintering step from iron powder.
• the granulation step with water or steam is replaced by a step of manufacturing -mechanical, from wire or sheet.
• a second subject of the present invention relates to a spheroidal projectile or steel ball, comprising a carbon content of between 0.8 and 2.0% by weight and a hardness with a core of less than 100 HV 10. preferably 85 HV 10, carried out by the aforementioned method.
• said projectile has a carbon content of between 1.2 and 1.8% C by weight.
• the projectile is provided with a surface coating to prevent agglomeration of the load.
• a third object of the present invention relates to a hunting or sports shooting cartridge comprising a load of steel balls as described above.
• FIG. 1 represents micrographic sections of steel balls respectively before and after decarburization treatment of the steel according to the state of the art.
• FIG. 2 shows micrographic sections respectively before and after treatment thermochemical similar to that of the invention in the case of a eutectoid steel.
• Figure 3 shows micrographic sections respectively before and after thermochemical treatment similar to that of the invention in the case of hypereutectoid hot rolled steel (1.2% by weight).
• Figure 4 shows micrographic sections respectively before and after thermochemical treatment where the tempering temperature is 700 0 C, in the case of hypereutectoid steel (1.5% C by weight).
• FIG. 5 represents micrographic sections respectively before and after thermochemical treatment according to the invention in the case of a hypereutectoid steel (1.5% by weight), the tempering temperature being 65O 0 C.
• the state of the art consists of softening by annealing under a decarburizing atmosphere of a common steel such as hypereutectoid steel (for example 1.5% C by weight), consisting of supersaturated carbon ferrite (Fe3C cementite).
• the mechanism is a decarburization of the outer layer of the ball due to the diffusion of carbon on the surface of the ball where it combines with oxygen for form carbon dioxide that escapes into the atmosphere.
• hardness values are expressed in Vickers hardness, the measurement method being well known to those skilled in the art (see for example EN ISO 6507-1 standard).
• this specific treatment makes it possible to manufacture a new product, made from recoated liquid steel.
• the granulation is preferably carried out with steam added with a specific surfactant.
• a perlitic steel of eutectoid composition (0.8% by weight) was annealed to bring it into the austenitic range.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Heat Treatment Of Articles (AREA)
• Powder Metallurgy (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Soft Magnetic Materials (AREA)
• Metal Extraction Processes (AREA)

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• 2006
  • 2006-06-16 BE BE2006/0329A patent/BE1017170A3/fr not_active IP Right Cessation
• 2007
  • 2007-05-21 ES ES07719212T patent/ES2336150T3/es active Active
  • 2007-05-21 AT AT07719212T patent/ATE448464T1/de active
  • 2007-05-21 US US12/302,968 patent/US8356555B2/en not_active Expired - Fee Related
  • 2007-05-21 WO PCT/BE2007/000048 patent/WO2007143800A1/fr active Application Filing
  • 2007-05-21 DE DE602007003221T patent/DE602007003221D1/de active Active
  • 2007-05-21 EP EP07719212A patent/EP2029957B8/de not_active Not-in-force

Non-Patent Citations (1)

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