Phosphor bronze is a member of the family ofcopper alloys. It is composed ofcopper that isalloyed with 0.5–11% oftin and 0.01–0.35%phosphorus, and may contain other elements to confer specific properties (e.g.lead at 0.5–3.0% to formfree-machining phosphor bronze). The tin increases the corrosion resistance and strength of the alloy, while the phosphorus increases its wear resistance and stiffness.[1]
Phosphor bronze alloys are notable for theirtoughness,strength, lowcoefficient of friction, and finegrain. The phosphorus reduces theviscosity of the molten alloy, which makes it easier and cleaner tocast and reducesgrain boundaries between crystallites. It was originally formulated by the BelgianGeorges Montefiore-Levi and the German Karl Künzel.[2][3]
Phosphor bronze is used forsprings,bolts,bushings,bearings, electrical switches with moving or sliding parts,dental bridges, the reed components of organ pipes, ship'spropellers, and various other products or assemblies where resistance to fatigue, wear, and corrosion are required.[4][5]
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 wire (available in standard round, square, flat, and special formats) desirable for many springs, electrical contacts, and a wide variety of wire forms where the desired properties do not require the use of the more-expensiveberyllium copper.[5]
Phosphor bronze with 94.8%copper, 5%tin, and 0.2%phosphorus is also used incryogenics. In this application, its combination of fairelectrical conductivity and lowthermal conductivity allows the making of electrical connections to devices at ultra-low temperatures without adding excessive heat.[6]
Oxygen-free copper can be alloyed withphosphorus (CuOFP alloy) to better withstand oxidizing conditions. This alloy has application as thick corrosion-resistant overpack forspent nuclear fuel disposal in deep crystalline rocks.[7]
Magnetic tape was first used to record computer data in 1951 on theEckert-MauchlyUNIVAC I. TheUNISERVO drive recording medium was a thin metal strip of 0.5-inch-wide (12.7-millimetre)nickel-plated phosphor bronze. The recording density was 128 characters per inch (198 micrometre/character) on eight tracks at a linear speed of 100 in/s (2.54 m/s), yielding a data rate of 12,800 characters per second. Of the eight tracks, six were data, one was aparity track, and one was a clock, or timing track. Making allowance for the empty space between tape blocks, the actual transfer rate was around 7,200 characters per second. A small reel of mylar tape provided separation from the metal tape and the read/write head.
Phosphor bronze is preferred overbrass forcymbals because of its greater resilience, leading to broader tonal spectrum and greatersustain.
Phosphor bronze is one of several high-copper-content alloys used as a substitute for the more-common "yellow" or "cartridge" types ofbrass to construct the bodies and bells of metalwind instruments. Examples of instruments constructed using high-copper alloys occur among members of thebrass instrument family (trumpets,flugelhorns, andtrombones) and one member of thereed instrument family,saxophones. In addition to the distinctive appearance provided by the reddish-orange hue of high-copper alloys, they are purported by some instrument designers, sellers, and players to provide a broader harmonic response spectrum for a given instrument design. TheYanagisawa 902/992 model saxophones (pictured) have bodies of phosphor bronze, in contrast to the brass 901/991 models.
Someinstrumentstrings foracoustic guitars,mandolins, andviolins are wrapped with phosphor bronze. Someharmonicareeds are made of phosphor bronze, such as those bySuzuki Musical Instrument Corporation and Bushman Harmonicas.[8]
The reed component of reed-typeorgan pipes is usually made of phosphor bronze owing to its high wear resistance and low deformability under conditions of constant vibration when producing sound.[9]
Somesnare drums are constructed with phosphor bronze.
Sometambourine jingles are made of phosphor bronze.
Further increasing the phosphorus content leads to the formation of a very hard compound, Cu3P (copper phosphide), resulting in abrittle form of phosphor bronze, which has a narrow range of applications.
Around 2001, theOlin Corporation developed another alloy for use in electrical and electronic connectors which they referred to as "phosphor bronze".[10] Its composition was as follows:
When assessed in strictlymetallurgical terms it is not a phosphor bronze, but a form of iron-modified tinbrass.
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