NICKEL BRONZE-leaded nickel-copperA name given to bronzes containing nickel, which usually replaces part of the tin, producing a tough, fine-grained, and corrosion-resistant metal. A common nickel bronze containing 88% copper, 5 tin, 5 nickel, and 2 zinc has a tensile strength of 48,000 lb/in2 (330 MPa), elongation 42%, and Brinell hardness 86 as cast. When it is heat-treated or age-hardened, the tensile strength is 87,000 lb/in2 (599 MPa), elongation 10%, and Brinell hardness 196. Small amounts of lead take away the age-hardening quality of the alloy and lower the ductility. But small amounts of nickel added to bearing bronzes increase the resistance to compression and shock without impairing the plasticity. A bearing bronze of this nature contains 73 to 80% copper, 15 to 20 lead, 5 to 10 tin, and 1 nickel. In the leaded nickel-copper, which contains 1% nickel, 1 lead, 0.2 phosphorus, and the balance copper, a nickel phosphide is dispersed in the alloy by heat treatment, giving a machinability of 80% that of a free-cutting brass. The tensile strength is 85,000 lb/in2 (586 MPa), elongation 5%, and electric conductivity 55% that of copper.
For decorative bronze parts, nickel is used to give a white color. In the hardware industry, the old name Chinese bronze was used for these white alloys. At least 10% nickel is needed to give a white color. This amount also gives corrosion resistance to the alloy. When more than 15% nickel is used, the bronzes are difficult to machine unless some lead is added. Hardware and plumbing fixtures of these alloys do not require plating.
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