PHOSPHOR BRONZE-Steel Bronze-Carbobronze-C94400
Copper-base alloys with low phosphorus content, originally called steel bronze when first produced at the Royal Arsenal in Vienna. It was 92–8 bronze deoxidized with phosphorus and cast in an iron mold. It is now any bronze deoxidized by the addition of phosphorus to the molten metal. It may or may not contain residual phosphorus in the final state. Ordinary bronze frequently contains cuprous oxide formed by the oxidation of the copper during fusion. By the addition of phosphorus, a powerful reducing agent, a complete reduction of the oxide takes place. Phosphor bronzes have excellent mechanical and cold-working properties and low coefficients of friction, making them suitable for springs, diaphragms, bearing plates, and fasteners. In some environments, such as salt water, they are superior to copper. Phosphor bronzes have been known by many trade names, including Duraflex, a hard-rolled strip and wire product for springs; Carbobronze, hard-drawn tubing and rod for bearings; Corvic, a spring grade with a tensile strength of 95,000 lb/in2 (655 MPa) and an electrical conductivity of 42% that of copper; and Telnic, a 1% nickel, 0.5 tellurium, 0.2 phosphorus grade. So-called white phosphor bronze is not a bronze, but a 72% lead, 15 phosphor tin, 12 antimony, 1 copper alloy.
Standard wrought phosphor bronzes are designated C50100 to C54800. Tin, which ranges from as much as 0.8 to 11% depending on the alloy, is the principal alloying element, although leaded alloys may contain as much lead (4 to 6%, for example) as tin. Phosphorus content is typically on the order of 0.1 to 0.35%; zinc, 0 to 0.3 (1.5 to 4.5% in C54400); iron, 0 to 0.1; and lead, 0 to 0.05 (0.8 to 6 in leaded alloys). The principal alloys were formerly known by letter designations representing nominal tin content: phosphor bronze A, 5% tin (C51000); phosphor bronze B, 4.75 tin (C53200); phosphor bronze C, 8 tin (C52100); phosphor bronze D, 10 tin (C52400); and phosphor bronze E, 1.25 tin (C50500). Phosphor bronze E, being almost 99% copper, is one of the leanest of these bronzes in the way of alloying ingredients and is used for electrical contacts, pole-line hardware, and flexible tubing. Its electrical conductivity is about half that of copper, and it is readily formed, soldered, brazed, and flash-welded. Thin, flat products have tensile yield strengths ranging from about 12,000 lb/in2 (83 MPa) in the annealed condition to 75,000 lb/in2 (517 MPa) in the extra-spring temper. More highly alloyed C54400 (4% tin, 4 lead, and 3 zinc, nominally) is about one-fifth as electrically conductive as copper, has good forming characteristics, and has 80% the machinability of C36000, a free-machining brass. Its ultimate tensile strength ranges from about 48,000 lb/in2 (331 MPa) in the annealed condition to 100,000 lb/in2 (690 MPa) in the extra-spring temper. Uses include bearings, bushings, gear shafts, valve components, and screw-machine products. An alloy C94400, which has been called a phosphor bronze, is suitable for sand castings and centrifugal castings. The nominally 81% copper, 11 lead, 8 tin alloy is 10% as electrically conductive as copper and, as sand-cast, has a typical ultimate tensile strength of 32,000 lb/in2 (221 MPa) and a tensile yield strength of 16,000 lb/in2 (110 MPa). It matches the machin-ability of C54400 and is used mainly for bushings and bearings.

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