Phosphor bronze

Phosphor bronze is a member of the family of copper alloys. It is composed of copper that is alloyed with 0.5–11% of tin and 0.01–0.35% phosphorus, and may contain other elements to confer specific properties (e.g. lead at 0.5–3.0% to form free-machining phosphor bronze). Alloyed tin increases the corrosion resistance and strength of copper, while phosphorus increases its wear resistance and stiffness. These alloys are notable for their toughness, strength, low coefficient of friction, and fine grain. The phosphorus reduces the viscosity of the molten alloy, which makes it easier and cleaner to cast and reduces grain boundaries between crystallites. It was originally formulated by the Belgian Georges Montefiore-Levi. Phosphor bronze is used for springs, bolts, bushings and bearings, electrical switches with moving or sliding parts, dental bridges, the reed component of organ pipes and various other products or assemblies where resistance to fatigue, wear, and corrosion are required (e.g., ship's propellers in a marine environment). Phosphor bronze comes in a wide array of standard alloys, including nonferrous spring alloys, free-machining phosphor bronze and bearing bronze. The combination of good physical properties, fair electrical conductivity, and moderate cost make phosphor bronze, available in standard round, square, flat, and special format wire desirable for many springs, electrical contacts, and a wide variety of wire forms where the desired properties do not require the use of more expensive beryllium copper. Phosphor bronze (94.8% copper, 5% tin, 0.2% phosphorus) is also used in cryogenics. In this application, its combination of fair electrical conductivity and low thermal conductivity allows the making of electrical connections to devices at ultra low temperatures without adding excessive heat. Oxygen-free copper can be alloyed with phosphorus (CuOFP alloy) to better withstand oxidizing conditions. This alloy has application as thick corrosion-resistant overpack for spent nuclear fuel disposal in deep crystalline rocks.