CA2498306A1 - Lead-free composition and method of manufacturing lead-free projectiles and projectile cores therewith - Google Patents

Abstract

A composition and method of manufacturing a lead free, high density matrix that may be used as a replacement for lead in those instances where lead is used, but its toxicity is undesirable. The composition comprises meta.I particles of at least two different metals combined with a non-toxic liquid binder, and is particularly useful in manufacturing lead-free projectiles such as shot, jacketless bullets and bullet cores for jacketed bullets.

Description

LEAD-FREE COMPOSITION AND METHOD OF MANUFACTURING LEAD-FREE

FIELD OF THE INVENTION
The present invention relates to lead-free compositions suitable for replacing lead in those instances where lead is used The invention also relates to projectiles, particularly leac~free shot, bullet cores and solid jacketless bullets and method of manufacture therewith.
BACKGROUND OF THE INVENTION
In the past, projectiles for hunting and target shooting have been manufactured using lead or lead alloys due to the high density, malleability and low melting points of these materials.
However, the toxicity of lead has resulted in recent government restrictions against lead shot for hunting, and particularly for hunting waterfowl. It should also be noted that many indoor shooting ranges are being shut-down due to lead contamination. This is happening in Canada as well in the United States and Europe.
In the past, thousands of tonnes of lead was released into environment each year. The lead shot would deposit itself in the bottom of lakes, ponds and wetlands. Geese and ducks would therefore ingest these lead pellets and cause these birds to die from lead poisoning. It is estimated that thousands of waterfowl die from lead poisoning every year.
In order to reduce the impact of lead on the environment, many governments have restricted the use of lead shot and lead-cored bullets. A nationwide ban on the use of lead shot for hunting waterfowl was implemented in the United States in 1991. Canada implemented a set of regulations requiring the use of non-toxic shot in all areas of Canada for hunting most migratory game birds by September l, 1999.
Canada and the United Staxes have approved several types of non-toxic shot including steel, bismuth, tungsten-iron, tungsten-polymer, tungsten-matrix, and tungsten-nickel-iron.
Steel shot is the most common and affordable of the non toxic shots. However, the density of steel is 7.9 glcc versus 11.2 glcc for lead Steel shot does not have the malleability of lead therefore require special barrels and chokes in order to shoot this type of shot without damaging the barrels.
Bismuth is about 85 percent as dense as lead. Bismuth, on the other hand, is Less abundant than lead and may be toxic to waterfowl as recently reported by Canadian scientists.
Tungsten-iron shot, tungsten-nickel-iron shot, and tungsten-polymer shot have good ballistics but the raw materials are expensive and their methods of manufacturing are also expensive.
United States Patent No. 5,831,188 (Amick) describes the manufacture of tungsten-iron shot This particular type of shot is as hard as steel and Like steel, tends to penetrate through game with a reduced energy transfer, and can damage the barrels of some older shotguns.
Additionally, tungsten-polymer shot described in United States Patent No.
6,216,598 (Godfrey Phillips), have a lower density of that of lead, thus making the shot inferior than Lead shot.
United States Patent No. 6,527,880 (Amick) describes the manufacture of tungsten-nickel-iron shot. This shot is expensive to manufacture and is as hard or perhaps harder than steel shot. The use of this shot will damage older types of shotguns.
Examples of lead-free bullets have been described in United States Patents No.
5,616,642 (West, et al), 6,090,178 (Benini), and 5,399,187 (Mravic, et al). While the bullets described in these documents are typically constructed of lead-free metal particles, the bonding element is either a metallic binder or a polymer binder or both. Polymer binders are usually in powdered form and must be heated in order to be injected in an injection machine. The risk of some metal particles and powdered polymers separating during the injection process is quite high.
The separation of metal particles from metallic binders or metal particles from polymer binders will cause problems in density variance within the part and also weak spots within the part due to the metal particles not bonding to the binder or binders. This is especially true if a rotary type press is utilized in the forming of parts such as shot, jacketless bullets, and bullet cores. This is more evident when such parts are formed with metal particles consisting of two or more different metals with or without a binder.
Vibrations due to the normal operation of a rotary press will cause metal particles and binders to segregate and creating the problems previously mentioned.
In the light of the known deficiencies of materials currently used for manufacturing lead free, non-toxic projectiles, there exists the need for a new material having properties comparable of those of lead.
SUNiNIARY OF THE INVENTION
Accordingly, it is an object ofthe present invention to provide an improved lead-free composition suitable far use in those apphcarions where lead is traditionally used. Another object of the invention is to provide a method for manufacturing lead-free projectiles using such a composition.
According to one aspect of the present invention, there is provided a lead-free composition comprising of metal particles of at least two different metals and a non-toxic liquid binder, wherein the liquid binder having a su~ciently low viscosity be thoroughly mixed with the metal particles.
Such a composition is particularly useful in manufacturing projectiles and projectile cores, such as non-toxic shot, lead-free bullets cores, and jacketless bullets_ However, it is also envisioned that such composition may be used in applications other than ballistics, such as wheel weights, weights used in balance scales, and useful as a lead replacement for lead typical x-ray protecting vests.. Also, this composition may be used in the insulation of nuclear reactors.
The viscosity of the liquid binder ranges from about 25 KU to about 150 KU, although the preferred viscosity ranges fram 80 to about 85 KU. The liquid non-toxic binder which are suitable for the composition of the present invention include molasses, corn syrup, liquid honey, maple syrup, dissolved sugar in a non-toxic medium, and any combination thereof Molasses was found to be particularly preferred.
The metal particles which may be used in the composition may comprise of two or more metals including tungsten, tungsten carbide, Ferro-tungsten, iron, tin, copper, brass, bronze, zinc, aluminum, nickel, bismuth, and molybdenum.
The ratios of metal to liquid border used in the present invention range from 10:1 to about 150:1 in parts by weight metal particles to parts by weight liquid binder, and depends upon the metals used However, a ratio of 90 parts metal particles to 1 part liquid binder is advantageously used in the preferred method of manufacturing non-toxic shot, when manufacturing bullet cores and solid, jacketless bullets, a ratio of 85 parts metal particles to 1 part liquid binder is used for the preferred embodiment.
The typical size of the metal particles used in the present invention ranges from approximately 5 to 45 microns in diameter. A metal particle size range of about 10 microns is preferred for non-toxic shot, while the preferred particle size range for non-lead bullet cores and jacketless bullets is about 20 to 45 microns.
According to a second aspect of the present invention, there is provided a method of manufacturing lead-free projectiles and cores used in bullet manufacturing comprising the steps of mixing metal particles of at least two different metals and a non-toxic liquid binder to form a matrix, molding the matrix under pressure in a molding apparatus to form a molded projectile or projectile core and heating the non-toxic liquid binder to form a f nished lead-free projectile or projectile core upon cooling down to at least 90 degrees Fahrenheit.
A variety of means are available for molding the matrix into the required form. Accordingly, any apparatus for molding may be used However, rotary or single tablet pressing machines, have been found to be particularly useful.
The non-toxic liquid hinder used in the above method may be molasses, corn syrup, maple syrup, liquid honey, sugar dissolved in a medium, and any combination thereof.
In the case molasses, the matrix formed with the metal particles should be dried, in order to allow any volatile liquids to evaporate. It is then preferred for the relatively dry matrix to be granulated by means of a roller compactor and milling machine.
When manufacturing non-toxic shot using the method of the present invention, the matrix is typically molded in a rotary press to form shot having a density ranging from approximately 9.5 glee to about 14.8 glee and the preferred to be 12.6 glee. The hardness of such shot ranges from about 4 Bh to about 20 Bh on the hardness sca.le_ In one embodiment of the method for manufacturing non-toxic shot, the liquid binder within the matrix is heated following removal of the shot from the shot molding apparatus.
When manufacturing projectiles and projectile cores, the finished projectiles and cores may be plated with a metal selected from the group consisting of copper, tin, zinc, copper alloys, nickel, and chrome.
Instead of plating the manufactured projectiles, the projectiles may be sintered in the manner known in the art.
When manufacturing lead-free bullet cores using the method of the present invention, the matrix is generally pressed within a bullet core-forming die or mold and heated to farm a bullet core having a density ranging from 3 glee to about 15 glee and the preferred density being 11.2 glee. The hardness of such bullet cores ranges from about 5 Bh to about 2Q Bh on the hardness sca.Ie. The bullet core may be seated inside a bullet jacket and point-formed in the usual manner.
When manufacturing solid, jacketless, lead-free bullets using the method of the present invention, the matrix is typically pressed in a bullet forming die and heated to form a bullet having a density ranging from 5 glee to about 15 gicc, and preferably from 8 glee to 11 glee.

In this method, the liquid binder within the matrix may be heated prior to removal of the bullet from the die, or following of the bullet from the die.
When manufacturing non-toxic shot and solid jacketless bullets using the inventive method, the molding pressure will vary depending upon the particular application for the projectile or core produced However, the applied force typically ranges from about 700 pounds to about 95 tonnes. Lower applied force is typically used in making shot while a higher applied force is required for making jacketless bullets.
The liquid binder within the matrix is generally heated to temperatures ranging from I00 degrees Fahrenheit to about 495 degrees Fahrenheit for a duration ranging for about 1 minute to about 100 minutes. In certain preferred methods of manufacturing shot, jacketless bullets, the optimal heating time is about 35 minutes at about 480 degrees Fahrenheit In all methods, the manufactured parts must be totally cooled to at Least 90 degrees Fahrenheit before usage_ BRIEF DESCRIPTION OF DRAWINGS
Embodiments of the present invention will be further described, by way of example, with reference to the accompanying drawings, in which:
Figure I is a diagrammatic cross-sectional view of a shot molding apparatus;
Figure 2 is a diagrammatic cross-sectional view of a finished shot using the method of the present invention;
Figure 3 is a diagrammatic cross-sectional view of a matrix core of the present invention being seated into a bullet jacket;
Figure 4 is a diagrunmatic cross-sectional view of a matrix core of the present invention seated inside a bullet jacket;
Figure 5 is a diagrammatic cross-sectional view of a solid, non jacketed bullet being formed with the matrix material of the present invention; and Figure 6 is a diagrammatic cross-sectional view of a finished solid bullet produced using the method of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In order to overcome the disadvantages of the known lead-free materials and methods for manufacturing lead-free projectiles and projectile cores, the inventor of the present invention has developed a novel lead-free composition and a method for manufacturing lead-free projectiles and projectile cores using the novel composition.
'The novel composition typically comprises lead-free metal particles of at least two different metals having densities greater than .1 g/cc and a non-toxic liquid binder.
These materials are mixed in ratios which are defined by the requirements of a particular application, such as to produce shot, bullet cores, and jacketless bullets or other projectiles.
Metal articles which are particular useful are as following, tungsten, tungsten carbide, ferro-tungsten, iron, tin, copper, brass, bronze, zinc, aluminum, nickel, bismuth, and molybdenum.
When compared to the size of the metal particles used for manufacturing bullets cores and bullets, the size of the metal particles used for the manufacturing of shot is significantly smaller. This reflects the relatively small size of shot and the requirement for the metal particles to compact tightly. The preferred size of the metal particles used for manufacturing shot is about 10 microns, whereas a range from 20 to about 4S microns for bullets and for bullet cores.
It is also to be understood that the non toxic liquid binder has a sufficiently low viscosity that the liquid binder can be thoroughly mixed with the metal particles. Some examples of the non-toxic liquid binder which may be used to manufacture the projectiles of the present invention include, molasses, corn syrup, maple syrup, liquid honey, sugar dissolved in a medium, although combinations thereof may also be used in some embodimeats.
The norr toxic liquid binder which is especially preferred for the purposes of this invention is molasses.
The viscosity of the non-toxic liquid binder may range from approximately 25 Krebs Units (KU) to approximately 150 KU. The preferred viscosity is between 80 to 85 ICU.
Heavier or larger particles may require a more fluid liquid binder, which may require the addition of a thinning agent. Thinning agents such as water or ethanol are not required for the preferred embodiments of the invention, it is to be understood that addition of suitable thinning agents to the liquid binder in order to increase its fluidity is also provided by the present invention.
The relative amount of metal particles to liquid binder in the novel composition depend largely upon the particular metals and liquid binders) being used. For instance, tungsten, iron and tin particles may be mixed with the liquid binder in a completely different ratio compared to copper, tungsten and tin particles.
Advantageously, the ratios of the metal particles to the non-toxic liquid binder used in the present invention range from i0:1 to about 150:1 in parts by weight metal particles to parts by weight liquid binder, and depend upon the metals used The preferred non-toxic shot has a ratio of 90 parts metal particles to 1 part liquid binder, and the preferred bullet cores and jacketless bullets have a ratio of 85 parts metal particles to 1 part liquid binder.
In an example of the method of manufacturing shotgun shot, the metal particles and non-toxic liquid binder are mixed together to form a matrix in a particular weight ratio such that the required density is achieved.
Example 1- Three hundred and eighteen grams of tungsten powder, 114 grams of tin powder, 22 gcaxns of iron powder were mixed with 5 grams of molasses having a temperature of 72 degrees Fahrenheit. The matrix was dried and roller compacted and then granulated The granulated matrix was then transferred to the hopper of a rotary press and #
6 shot was then pressed using a molding pressure of 2100 pounds. The shot was heated to about 480 degrees Fahrenheit for about 30 minutes and attained a density of 12.6 glcc. The shot was assembled in a shotgun shell, and fired The resulting pattern was found to be similar to lead. It must be noted that the shot was totally cooled before it was assembled into ammunition.
In certain embodiments, the finished shot may be plated with copper, zinc, chrome, or nickel. The shot is generally plated using standard electroplating processes that are known in the art Also, the shot may be sintered using methods known in the art.
During the manufacturing process, the hardness or brittieness, of the shot can be controlled by adjusting the time and heating temperature, by changing the molding force, and changing the ratio of the liquid binder.
In an example of a method of manufacturing lead-free bullet cores, metal particles and a non-toxic liquid binder are mixed together to form a matrix in ratios specific to the properties of a desired product. T he metal particle/Iiquid binder matrix is forced in a core forming die or mold and compressed The core is heated and the liquid binder within the core is hardened. The hardened core is seated inside a bullet jacket, following by finishing of a bullet using a point forming die. In order to control the weight of each individual core, the formed cores are inserted in a swaging die having at least one extrusion hole.
This procedure is well known in the art. However, the required force needed to swage a formed core will be slightly more than the initial core forming force.
Below is an example of the bullet core manufacturing process;
Example 2- Two hundred and sixty three grams of tungsten powder, 114 grams of tin powder, 77 grams of iron powder, and 5.3 grams of molasses having a temperature of 72 degrees Fahrenheit were mixed The matrix was left to dry for about 1 hour,roller compacted and then granulated. The resulting granulation was placed in a hopper of a rotary press and core blanks were pressed at a molding pressure of 6.5 tonnes. The resulting cores attained a density of 11.1 glcc. The care blanks were placed in a core swaging die and precise cores were formed These cores were placed inside a J-4 jacket, seated and point formed The resulting bullets were loaded into ammunition and fired. The accuracy was comparable to Lead cored bullets. It is to be noted that the bullet cores were totally cooled down before being seated into the bullet jackets. The heating temperature in this example was 175 degrees Fahrenheit.
In an example of the method of manufacturing solid, jacketless bullets which are lead free based, metal particles and a liquid binder are mixed together to form a matrix using ratios specific to the properties of the desired product. Following mixing of these materials, the matrix is forced inside a die or mold having the shape and size of the desired bullet. If the bullet is to be plated, the un-plated bullet must be slightly undersize in order to accommodate the plating. The matrix is then compressed. The liquid binder within the matrix may be heated during the molding phase or heated after the bullet is removed from the molding apparatus. It should be noted that the liquid binder hardens after the bullet has cooled down to about 90 degrees Fahrenheit.
Example III- Three and eighty-six grams of copper powder, 45 grams of tin powder, 23 grams of tungsten powder were mixed in 5.3 grams of molasses having a temperature of 72 degrees Fahrenheit. The matrix was left to dried for about 1 hour, roller compacted and granulated. The granulation was dumped inside the hopper of a rotary press and the matrix was pressed into 9MM bullets with a force of 10.5 tonnes. Each resulting bullets weighed about 100 grains and attained a density of 9 g/cc. The bullets were heated for 35 minutes at a temperature of 480 degrees Fahrenheit. After cooling, the bullets were loaded into ammunition and fired It was noted that none of the bullets fractured during firing and accuracy was comparable to lead The preferred heating temperature ranges from 100 degrees Fahrenheit to about 490 degrees Fahrenheit for a duration ranging from 1 minute to about 100 minutes. In the preferred method of manufacturing shot, and solid, jacketless bullets, the optional heating time is about 35 minutes at about 480 degrees Fahrenheit. A preferred heating condition used in the method of manufacturing certain bullet cores is about 120 degrees Fahrenheit for 20 minutes and cooled to at least 90 degrees Fahrenheit.
The lead free shot manufactured according to the present invention will advantageously have a density from approximately 9.5 g/cc to about i 4.8 g/cc. However, it is preferable that the density is slightly higher than the density of lead or approximately 12 g/cc.
The bullet cores will also typically have a density close to the specific gravity of lead, and similar malleability.

Accordingly, the density of the bullets cores of the present invention generally have a density ranging from 3 g/cc to about 1 S g/cc, and optimally about 11 g/cc.
In regards to solid, jacketless bullets, the density may range from S g/cc to 1S glcc, although the preferred bullets have a specific gravities very close to that of lead, or approximately 11.2 g/cc.
With reference to the drawings, preferred embodiments of the methods of manufacturing non-toxic shot, bullet cores and solid jacketless bullets will be described in further detail.
In the method of manufacturing non-toxic shot of the present invention, non-lead metal particles 6 and non-toxic liquid binder 5 are mixed together to form a matrix The matrix is then forced via injection or~.fice 3 into a die or molding apparatus 1 having an array of shot cavities 2 cut or drilled therein (figure 1). The non-toxic binder in the matrix in then heated until the binder hardens. The shot 4 may remain within the molding apparatus 1 during the heating process, or the shot 4 may be removed from the molding apparatus 1 prior to heating of liquid binder 5. The resulting finished shot 4 comprises a dense matrix of metal particles and solidified liquid binder after cooling to about 90 degrees Fahrenheit {Figure2).
The finished shot 4 may also be plated with metal such as copper, zinc, tin, nickel, and chrome. Instead of plating, the finished shot 4 may be sintered according to the methods known in the art.
In the method of manufacturing lead-free bullet cores of the present invention, non-lead metal particles 6 and non-toxic liquid binder are mixed together to form a matrix. In the preferred embodiment, a specific amount of the matrix is placed in a core seating die 9 and compressed between an external punch 7 and an internal punch 8. The bullet care 1 I is seated directly inside a metal bullet jacket IO using the core seating die 9 {figure 3).
Alternatively, the bullet core 11 may be swaged separately in a core swaging die having at least one extrusion hole. The required swaging pressure will normally exceed the forming initially needed to form the bullet. The swaged core is seated inside a metal bullet jacket IO
in a separate step. The non-toxic liquid binder S in the matrix is heated, and the resulting bullet is point-formed using a point-forming die. In another embodiment of this method, the non-toxic liquid binder 5 within the matrix of the bullet core 1 I may be heated after the point-forming process. In either case, the heated binder solidifies after the bullet core is cooled to about at least 90 degrees Fahrenheit.
In an example of manufacturing solid, jacketless, lead-free bullets of the present invention, lead-free articles 6 and non-toxic liquid binder S are mixed together to form a matrix in a specified ratio_ Following mixing, the matrix is placed inside a bullet-forming die 12 and compressed by external punch T and internal punch 8' {figure5)_ It is to be understood that the external punch T and internal punch 8' are distinct from external punch 7 and internal punch 8 used for the forming of bullet cores 1 l, and are selected based on the desired shape and size of bullet 13. The non-toxic liquid binder 5 within the matrix of bullet 13 may be heated during the molding step, or after the bullet 13 is removed from the bullet-forming die 12. If the bullet is to be heated during the molding step, it is recommended that bullet 13 is cooled to at least 90 degrees Fahrenheit before removal from bullet-forming die 12.
The foregoing are exemplary embodimerns of the present invention and a person skilled in the art would appreciate that modifications to these embodiments may be made without departing from the scope and spirit of the invention.

Claims (16)

1. A lead-free composition comprising of metal particles of at least two different metals and a non-toxic liquid binder selected from the group consisting of molasses, corn syrup, maple syrup, liquid honey, sugar dissolved in a medium, or a combination thereof, having a sufficiently low viscosity to be thoroughly mixed with the metal particles.

2. The composition according to claim 1, wherein the metal particles include two or more of the metals selected from the group consisting of tungsten, tungsten carbide, ferro-tungsten, iron, tin, copper, brass, bronze, zinc, aluminum, nickel, bismuth, and molybdenum.

3. The composition according to claims 1 and 2, wherein the liquid hinder has a viscosity ranging from 25 KU to about 150 KU.

4. The composition according to claims 1 and 2, wherein the liquid binder has a viscosity ranging from about 80 to 85 KU.

5. The composition according to any one of claims 1 to 4, wherein the metal particles and the non-toxic liquid binder are mixed in a ratio from about 10:1 to about 150:1 in parts by weight particles to parts by weight liquid binder.

6. Use of the composition according to any one of claims 1 to 5 for manufacturing projectiles, projectile cores, wheel weights, weights for balance scales, insulation far nuclear reactors, or as a lead replacement material in x-ray protecting vests.

7. A method of manufacturing lead-free projectiles and cores utilized in projectile manufacturing comprising the steps of:

mixing metal particles of at least two different metals and a non-toxic liquid binder selected from the group consisting of molasses, corn syrup, maple syrup, liquid honey, sugar dissolved in a medium, or combination thereof to form a matrix.
molding the matrix under pressure in a molding apparatus to form a molded projectile or projectile core, and heating the liquid binder to form a finished projectile or projectile core, and cooling the lead-free projectile or projectile core to at least 90 degrees Fahrenheit.

8. The method according to claim 8, wherein the molding apparatus is a rotary or single stage tablet press machine.

9. The method according to claim 7, wherein the matrix is granulated by means of a roller compactor.

10. The matrix according to any claims 7 to 9, wherein the heating is conducted at a temperature ranging from 100 degrees Fahrenheit to about 495 degrees Fahrenheit for a duration ranging from about 1 minutes to about 100 minutes, and is performed following removal of the molded projectile or projectile core from the molding apparatus, or within the molding apparatus prior to removal.

11. The method according to any one of claims 7 to 10, wherein the metal particles and non toxic liquid binder are mixed in a ratio of about 10:1 to about 150:1 in parts by weight metal particles to parts by weight non toxic liquid binder, and the metal particles range from approximately 5 microns to approximately 45 microns in diameter.

12. The method according to any one of claims 7-11, wherein the molding pressure ranges from approximately 700 pounds to approximately 95 tonnes, and the projectile formed is lead-free shot having a density ranging from approximately 9.5 g/cc to approximately 14.8 g/cc.

13. The method according to any one claim 7 to 12, wherein the molding pressure ranges from approximately 700 pounds to approximately 95 tonnes, the molding apparatus is a bullet-core molding apparatus, and the projectile formed is a bullet-core having a density ranging approximately 3 g/cc to approximately 15 g/cc.

14. The method according to claim 13, further comprising the steps of seating the bullet core inside a bullet jacket and point-forming to produce a bullet, wherein the seating is performed separately following the molding step, or simultaneously with the molding step by molding the matrix within the bullet jacket.

15. The method according to any claim 7-14, wherein the molding pressure ranges from approximately 700 pounds to approximately 95 tonnes, the molding apparatus is a bullet molding apparatus, and the projectile formed is a solid, jacketless, lead-free bullet having a density ranging from approximately 5 g/cc to 15 g/cc.

16. Lead-free shot, bullet cores or solid, jacketless bullets comprising the composition according to any one claims 1 to 5, or manufactured according to the method as defined in any one of claims 7 to 15.