Alloys or metallic compositions – Tin base – Antimony – or bismuth containing
Reexamination Certificate
1998-12-21
2001-03-06
Jenkins, Daniel J. (Department: 1742)
Alloys or metallic compositions
Tin base
Antimony, or bismuth containing
C420S561000
Reexamination Certificate
active
06197253
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a lead-free and cadmium-free alloy and method for making the same. More particularly, the invention is directed to a lead- free and cadmiumn-free casting alloy for making, for example, jewelry, statuary, hardware, or other cast objects including ornamental pieces and the like.
Description of the Related Art
In the alloy casting art for making pieces such as hardware, jewelry, statuary, or other ornamental pieces, it is advantageous for the casting alloy to have certain desirable properties and/or characteristics. Such properties include, but are not limited to: (1) a hypo-allergenic quality, (2) a non-toxic quality, (3) low temperature castability, (4) traceability (e.g., to its source by its composition), (5) reduces wear and tear on molds (e.g., an alloy that extends the life of a black rubber mold over 60-100 castings, preferably indefinitely), (6) crimpable without breakage, (7) polishable to a high gloss finish or luster, (8) tarnish resistant, (9) quick to solidify (e.g., exhibits a spin time shorter than that of conventional lead-pewter alloys on a centrifical casting machine), (10) high fluidity (ie., fluidity or flow sufficient to fill a mold without porosities, but sufficient to avoid flash formation—excess liquidus alloy that has crept between adjacent essentially flattened portions of mold halves creating an essentially flat undesirable flange circumscribing the cast piece or portion thereof), (11) dross or slag resistant (ie., does not form rust, dirt, oxides, heat streaking or the like on the surface of the molten alloy), (12) consistently reproducible castability (e.g., which is essentially free of voids and porosity defects), and (13) usable with a black rubber mold.
Unless otherwise indicated, the percentages recited below are by weight, based on the total weight of the alloy. U.S. Pat. No. 3,870,513 discloses a white metal alloy (i.e., an alloy having a tin content of at least about 90%) comprising 90.5-92.5% tin, 2.9-3.1% antimony, 1.4-1.6% cadmium and 3.3-3.7% lead. This alloy is neither lead or cadmium free. As these metals are known to be toxic, such an alloy does not provide one or more of the aforementioned desirable properties and/or characteristics.
U.S. Pat. No. 4,758,407 discloses lead-free and cadmium-free tin- and tin/antimony-based solder alloys. The non-toxic tin-based solder composition comprises 92.5%-96.8% tin, 3.0-5.0% copper, 0.1-2.0% nickel and 0.0-5.0% silver. The non-toxic tin/antimony-based solder composition comprises 87.0-92.9% tin, 4.0-6.0% antimony, 3.0-5.0% copper, 0.0-2.0 nickel and 0.0-0.5% silver. These compositions are typically used for plumbing applications, wherein the solders are exposed to potable water. These alloys are not free of copper.
U.S. Pat. No. 4,806,309 discloses a lead-free solder composition for soldering plumbing joints. The lead-free solder composition comprises approximately 90% to 95% tin, approximately 3% to 5% antimony, approximately 1% to 4.5% bismuth, and approximately 0.1% to 0.5% silver.
U.S. Pat. No. 5,435,857 discloses a soldering composition for soldering components in electronic and microelectronic circuitry. The composition consists essentially of an alloy comprising tin, indium, antimony, silver and in the range of about 0.0% to about 10.5% bismuth.
U.S. Pat. No.5,256,370 discloses a low melting point solder alloy comprising tin, silver and indium. The disclosed alloy is typically used in automated soldering operations. This alloy is lead-free. In the embodiments disclosed within this patent, the alloy contains from about 70% to about 92% tin, from about 1% to about 5% silver and from about 4% to about 35% indium. A preferred composition contains about 77.2% tin, about 2.8% silver, and about 20% indium.
U.S. Pat. No. 5,229,070 discloses a low temperature-wetting solder paste which comprises a mixture of first and second solder powders. The first solder is formed predominantly (at least 90%) of tin. The second powder is formed of a tin alloy containing indium or bismuth and has a melting temperature less than the first solder powder. This patent does not disclose suitability of such alloy paste for making jewelry, statuary or other ornaments.
U.S. Pat. No. 5,538,686 discloses a lead-free solder alloy of tin, indium and zinc (e.g., in a Sn-In-Zn weight ratio of 86:5:9) to which bismuth and/or antimony may be added. The alloy is directed to uses in industrial processes such as formation of interconnects and packaging of electronic devices.
The various desirable characteristics of a castable alloy include, but are not limited to: the lowest achievable liquidus temperature (e.g., of at least about 340° F., such as from about 340° F. to about 450° F., preferably about 340° F. or lower), readily fills molds (e.g., at a temperature from about 380° F. to about 425° F.) without voids, porosities, flash, dross or slag formation, burnout, heat streaking and the like.
An alloy essentially free of one or more of zinc, nickel, iron, lead, cadmium, silver, copper and aluminum is sought to avoid various toxicity and other problems associated with these metals when incorporated into an alloy for use in the casting art. To date, applicants are unaware of any lead-free and cadmium-free alloy which advantageously provide the above-noted desirable properties and characteristics.
Further, none of the aforementioned patents disclose an alloy which provides the above-noted desirable properties and/or characteristics of an alloy suitable for casting hardware, jewelry, statuary, filigree and other ornamental pieces. Therefore, there exists a need for such an alloy and for a method for making such an alloy which provides essentially all the aforementioned desirable properties and/or characteristics.
SUMMARY OF THE INVENTION
The invention is directed to a castable alloy for use in making hardware, jewelry, statuary, filigree, and/or other ornamental pieces which satisfies at least a plurality of the above-noted desirable properties and/or characteristics. The alloy is essentially free (e.g., at most, having only trace amounts) of zinc, nickel, iron, lead, cadmium, and aluminum. Further, the alloy is essentially free of copper and silver to the extent that the sum of any copper and any silver does not exceed about 0.5%.
As used herein, for example, the term “essentially free” with respect to lead (i.e., “lead-free”) means that the alloy or solder contains, at most, trace amounts of lead. As a guideline to the meaning of “essentially free of lead,” see Federal Specification QQ-S-571E Interim Amendment 5 (ER) Dec. 28, 1989, paragraph 3.2.1.1.1, as approved by the Commissioner, Federal Supply Service, General Services Administration (lead should not exceed 0.2%). Of course, “essentially lead-free” also includes lead concentrations at or below 0.2%. For use in utensils such as flatware, forks, knives, spoons, plates, cups, other kitchenware, and the like, “essentially lead-free” means not to exceed about 0.02% (in lead content) or not to exceed the current maximum allowable lead content in such items (as set forth by the appropriate U.S. governmental agency in 1998).
Further, as described in column 2 of aforementioned U.S. Patent No. 4,806,309, a solder composition prepared according to the following percentage proportions by weight: tin-95%, antimony-3%, bismuth-1.5%, and silver-0.5%—was subjected to elemental analysis. The elemental analysis indicated that the above-noted alloy contained the following percentage proportions by weight of other elements: lead-0.060%, arsenic-0.036%, copper-0.034%, nickel-0.0066%, iron-0.0060%, cadmium-less than 0.005%, and indium-less than 0.003%. Additionally, because the detection limit for gold, aluminum and zinc was 0.005% or less of the methods used (as disclosed in U.S. Pat. No. 4,806,309), the alloy is said to be free of each of these metals
Thus, for example, the above-noted composition of tin-95% (balance), antimony-3% (3.2% detected), bismuth-1.5% (1.49% detected) and silver (0.48% detected) would be considered to be “essent
Broomfield Allen
Morrissey Everett George
Banner & Witcoff , Ltd.
Coy Nicole
Jenkins Daniel J.
LandOfFree
Lead-free and cadmium-free white metal casting alloy does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lead-free and cadmium-free white metal casting alloy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lead-free and cadmium-free white metal casting alloy will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2453780