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Coinage Cladding Alloy and Processing for Making Coinage Cladding Alloy
Patent Number: 10,513,768
Abstract
A coinage cladding alloy for coinage includes nickel present in an amount from 5 wt. % to 7 wt. %, based on a total weight of the coinage cladding alloy; zinc present in an amount from 21 wt. % to 29 wt. %, based on the total weight of the coinage cladding alloy; manganese present in an amount from 12 wt. % to 16 wt. %, based on a total weight of the coinage cladding alloy; copper; an electrical conductivity from 2% International Annealed Copper Standard (IACS) to 3% IACS; and a color comprising a yellowness vector b* that is from 2 to 10, based on a CIE L*a*b* color space and determined in accordance with ASTM Standard E308-15 (2015).
Patent Description
The US Mint charged NIST with more cost effect 5 and 25 cents coins. Currently, commercial cupronickel C71300 alloy is not cost effective to produce 5 cent coins. C77000 is a commercial ternary alloy of Cu, Ni, and Zn possessing similar properties of C71300 but cost approximately 20% less to produce. The US Mint charged NIST to: (1) Modify the testing of ternary C77000 ternary alloy to match the properties of C71300; (2) Modify the existing C99750T quaternary alloy consisting of Cu, Ni, Zn, and Mn to match the properties of C71300, creating a material costing 40% less to produce; and (3) Modify the existing C99750S quaternary alloy consisting of Cu, Ni, Zn, and Mn to create a low conductivity alloy for use as the cladding material for the 25 cent coin.
Features
In addition to the decrease in cost, the decreased electrical conductivity and increased cladding layer thickness widens the required tolerances in final coin thickness and conductivity (of each layer and overall), improving the acceptance rate of final coin products in terms of their composite electrical behavior.