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copper and copper alloys

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a brief description about copper and copper alloys. their applications.

Published in: Engineering

copper and copper alloys

  1. 1. Introduction Copper : Copper is non-polymorphous metal with face centered cubic lattice (FCC, Fig. 1). Pure copper is a reddish color, zinc addition produces a yellow color, and nickel addition produces a silver color. Melting temperature is 1083 °C and density is 8900 kg.m-3, which is three times heavier than aluminum. The heat and electric conductivity of copper is lower compared to the silver, but it is 1.5 times larger compared to the aluminum. Fig. 1. FCC lattice Properties:  High electrical conductivity  High thermal conductivity  High corrosion resistance  Good ductility and malleability  Reasonable tensile strength Pure copper electric conductivity is used like a basic value for other metals evaluation and electric conductivity alloys characterization. The pure metal alloying decreased its conductivity . Physical properties of copper:  Crystal structure FCC  Atomic number 29  Atomic weight 63.546  Density (g.cm-3) 8.933  Melting point (oC) 1084.62 Coppers mechanical properties depend on its state and are defined by its lattice structure. Copper has good formability and toughness at room temperature and also at reduced temperature. Increasing the temperature steadily decreases coppers strength properties. Also at around 500 °C
  2. 2. the coppers technical plastic properties decrease. Due to this behavior, cold forming or hot forming at 800 to 900 °C of copper is proper. Cold forming increases the strength properties but results in ductility decreasing. In the as cast state, the copper has strength of 160 MPa. Hot rolling increases coppers strength to 220 MPa. Copper has a good ductility and by cold deformation it is possible to reach the strength values close to the strength values of soft steel. a) temperature influence on tensile strength, yield value and ductility b) change properties due to the cold forming Fig. 3. Copper mechanical properties
  3. 3. Effect of various alloying elements Classification of copper and copper alloys: Copper and copper alloys are designated according to the Copper Development Association (CDA):  Wrought alloys (C100-C799)  Cast alloys (C800-C999) Copper alloys are identified by the Unified Numbering System (UNS) which categorizes families of alloys based upon their elemental make-up. Wrought products range from UNS C10000 through UNS C79999; cast products are assigned numbers between UNS C80000 and UNS C99999.
  4. 4. UNS alloy designation Unalloyed Copper: Copper in its pure, unalloyed state is soft, provides high electrical and thermal conductivity and has excellent corrosion resistance. There are various grades of unalloyed copper which differ in the amount of impurities they contain. Oxygen free grades are used for high conductivity and ductility. Cu-0xygen phase diagram
  5. 5. As cast oxygen free Cu Hot worked Hot-worked oxygen free copper exposed to H2 at 850oC/0.5h
  6. 6. Brasses: Brasses are alloys made from copper and zinc, they exhibit good strength and ductility and are easily cold worked, properties which improve with increased zinc content up to 35%. Brass coloration ranges from red to golden yellow, depending on the amount of zinc the alloy contains.Gilding Metal, Commercial Bronze, Jewelry Bronze, Red Brass and Cartridge Brass are common names given to brass alloys with specific zinc contents. Brasses containing between 32% and 39% zinc exhibit excellent hot working characteristics but limited cold workability. Brasses containing more than 39% zinc, such as Muntz Metal, have high strength and lower ductility at room temperature than alloys with less zinc. Brasses are known for their ease of fabrication by drawability, high cold- worked strength and corrosion resistance. Brasses are routinely blanked, coined, drawn and pierced to produce springs, fire extinguishers, jewelry, radiator cores, lamp fixtures, ammunition, flexible hose and the base for gold plate. Cu-Zn phase diagram
  7. 7. Tin Brasses: Tin Brasses are alloys made from copper, zinc (2% to 40%) and tin (0.2%-3%). This family of alloys include admirality brasses, naval brasses and free-machining tin brasses. These alloys are used to made high strength fastners, electrical connectors, springs, corrosion resistant mechanical products, marine hardware, pumps shafts and corrosion resistant screw machine parts. They provide increased corrosion resistance. They possess good hot forgeability and good cold formability. These materials have moderate strength, high atmospheric and aqueous corrosion resistance and excellent electrical conductivity. Cu-Tin alloy phase diagram
  8. 8. Silicon Bronzes: Silicon Bronzes are part of the subgroup of high-strength brasses. They contain less than 20% zinc and upto 6% silicon and are solid solution strengthened. Silicon red brasses are used for valve stems where corrosion resistance and high strength are critical. Included in this category are the silicon red bronzes, which are similar to silicon red brasses except for their very low concentrations of zinc. They are used to make bearings, gears and intricately shaped pump and valve components. Cu-Silicon phase diagram Nickel Silvers: Nickel Silvers, also called nickel brasses, are alloy containing copper, nickel and zinc. Though they do not contain silver, they have an attractive silver luster, moderately high strength and good corrosion resistance. They are used to make food and beverage handling equipmentt, decorative hardware, electroplated tableware, optical and photographic equipment and musical instruments.
  9. 9. Copper Nickel: Copper Nickel alloys contain anywhere from 2% to 30% nickel, are highly corrosion- resistant and thermally stable. The addition of iron, chromium, niobium and/or manganese can improve their strength and corrosion resistance in steam and moist air. They are used to make electrical and electronic products, tubes for condensers in ships, on offshore platforms and in power plants, and various other marine products including valves, pumps, fittings and sheathing for ship hulls. Phosphor Bronzes: Phosphor Bronzes, or tin bronzes as they are sometimes called, contain between 0.5% and 11% tin and 0.01% to 0.35% phosphorous. Tin increases their corrosion resistance and tensile strength, phosphorus increases wear resistance and stiffness. They have super spring qualities, high fatigue resistance, excellent formability and solderability. TABLE : Compositions & Properties of the More Common Copper Alloys
  10. 10. Aluminum bronzes: Aluminum Bronzes contain 6% to 12% aluminum, up to 6% iron and nickel and provide high strength and excellent corrosion and wear resistance. Solid solution strengthening, cold work and precipitation of an iron rich phase contribute to these characteristics. High aluminum containing alloys can be quenched and tempered. Aluminum bronzes are used in marine hardware, shafts and pump and valve components for handling seawater, sour mine waters, nonoxidizing acids, and industrial process fluids. They are also used as heavy duty sleeve bearings and machine tool ways. Aluminum bronze castings have exceptional corrosion resistance, high strength, toughness and wear resistance. They also exhibit good casting and welding characteristics. Cu-Al alloy phase diagram Effect of Al on mech. Properties
  11. 11. Speciality copper alloys: Specialty Copper Alloys, based, for example, on the copper-nickel-silicon and copper-nickel-tin systems provide unique combinations of properties due to their intrinsic precipitation hardening capability. Their high strength coupled with good formability, thermal stability and electrical conductivity make them appropriate to use them in electrical and electronic connectors and hardware. As we have seen, copper and its alloys constitute a broad range of chemical compositions and are employed widely in applications that enable and enhance our everyday lives. Each application makes effective use of copper’s attributes: strength, conductivity, color, formability, joinability and thermal stability.
  12. 12. Coppers Metals which have a designated minimum copper content of 99.3%or higher. High Copper Alloys For the wrought products, these are alloys with designated copper contents less than 99.3% but more than 96% which do not fall into any other copper alloy group. The cast high copper alloys have designated copper contents in excess of 94%, to which silver may be added for special properties. Brasses These alloys contain zinc as the principal alloying element with or without other designated alloying elements such as iron, aluminum, nickel and silicon. The wrought alloys comprise three main families of brasses: copper-zinc alloys; copper-zinc-lead alloys (leaded brasses); and copper-zinc-tin alloys (tin brasses). The cast alloys comprise four main families of brasses: copper-tin-zinc alloys (red, semi-red and yellow brasses); "manganese bronze" alloys (high strength yellow brasses); leaded "manganese bronze" alloys (leaded high strength yellow brasses); copper- zinc-silicon alloys (silicon brasses and bronzes); and cast copper-bismuth and copper- bismuth-selenium alloys. Ingot for remelting for the manufacture of castings may vary slightly from the ranges shown. Bronzes Broadly speaking, bronzes are copper alloys in which the major alloying element is not zinc or nickel. Originally "bronze" described alloys with tin as the only or principal alloying element. Today, the term is generally used not by itself but with a modifying adjective. Forwrought alloys, there are four main families of bronzes: copper-tin- phosphorus alloys (phosphor bronzes); copper-tin- lead-phosphorus alloys (leaded phosphor bronzes); copper-aluminum alloys (aluminum bronzes); and copper-silicon alloys (silicon bronzes). The cast alloys have four main families of bronzes: copper-tin alloys (tin bronzes); copper-tin-lead alloys (leaded and high leaded tin bronzes); copper-tin-nickel alloys (nickel-tin bronzes); and copper- aluminum alloys (aluminum bronzes). The family of alloys known as "manganese bronzes," in which zinc is the major alloying element, is included in the brasses, above. Copper- Nickels These are alloys with nickel as the principal alloying element, with or without other designated alloying elements. Copper- Nickel-Zinc Alloys Known commonly as "nickel silvers," these are alloys which contain zinc and nickel as the principal and secondary alloying elements, with or without other designated elements. Leaded Coppers These comprise a series of cast alloys of copper with 20% or more lead, sometimes with a small amount of silver, but without tin or zinc. Special Alloys Alloys whose chemical compositions do not fall into any of the above categories are combined in "special alloys."
  13. 13. Standard Chemical Composition Limits The composition limits in this listing of Standard Designations for Copper and Copper Alloys are presented according to the following numerical convention, wherever practicable. Constituent Convention For Expressing Composition Limits Copper Nos. C10000 - C15999 (wrought) and C80000 - C81199 (cast): Copper XX.XX Alloying elements and impurities: 1/10 and over .XX 1/100 and less than 1/10 .0XX 1/1000 and less than 1/100 .00X less than 1/1000 .000X Copper Alloy Nos. C16000 - C79999 (wrought) and C81300 - C99999 (cast): Copper XX.X Alloying elements and impurities: 6/10 and over .X 1/10 and less than 6/10 .XX
  14. 14. Constituent Convention For Expressing Composition Limits Copper Nos. C10000 - C15999 (wrought) and C80000 - C81199 (cast): 1/100 and less than 1/10 .0X 1/1000 and less than 1/100 .00X less than 1/1000 .000X Temper designation: Temper designation of copper alloys was developed by the American Society for Testing and Materials (ASTM). The designation system uses codes, consisting of a letter, indicating general temper, and additional numbers and letters, specifying the temper parameters:  O – annealed: O10…O82 – various degrees of annealing; OS005…OS200 – annealed to a specific grain size;  M - as manufactured: M01…M45 – manufactured by a specific method;  H – cold worked: H00…H14 – various degrees of cold work (hardness); H50…H86 – cold work in specific process; HR01…HR50 – cold work followed by stress relief; HT04…HT08 – cold work followed by strengthening heat treatment;  T - heat treatment followed by rapid cooling: TB00 – solution treatment; TD00…TD04 – solution treatment followed by cold work; TF00 – solution treatment followed by precipitation hardening; TL00…TL04 – precipitation hardening followed by cold work;
  15. 15. TR00…TR04 – precipitation hardening followed by cold work and stress relief; TH00…TH04 – solution treatment followed by cold work and precipitation hardening; TM00…TM008 – combination of cold work by rolling and precipitation hardening; TQ00…TQ75 – hardening by quenching;  W – welded: WM00…WM50 – as welded; WO – welded and annealed; WH00...WH01 – welded and cold worked; WR00…WR01 – welded, cold worked and stress relieved.

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