Oxygen-free copper (OFC) or oxygen-free high thermal conductivity (OFHC) copper is a group of wrought high-conductivity copper alloys that have been electrolytically refined to reduce the level of oxygen to 0.001% or below. [1] [2] Oxygen-free copper is a premium grade of copper that has a high level of conductivity and is virtually free from oxygen content. The oxygen content of copper affects its electrical properties and can reduce conductivity. [3] [ unreliable source? ]
Oxygen-free copper is typically specified according to the ASTM/UNS database. [4] The UNS database includes many different compositions of high conductivity electrical copper. Of these, three are widely used and two are considered oxygen-free:
Oxygen-free high thermal conductivity (OFHC) copper is widely used in cryogenics. OFHC is produced by the direct conversion of selected refined cathodes and castings under carefully controlled conditions to prevent contamination of the pure oxygen-free metal during processing. The method of producing OFHC copper ensures an extra high grade of metal with a copper content of 99.99%. With so small a content of extraneous elements, the inherent properties of elemental copper are brought forth to a high degree. In practice the oxygen content is typically 0.001 to 0.003% with a total maximum impurity level of 0.03%. These characteristics are high ductility, high electrical and thermal conductivity, high impact strength, good creep resistance, ease of welding, and low relative volatility under ultra-high vacuum. [5]
Conductivity is generally specified relative to the 1913 International Annealed Copper Standard of 5.8×107 S/m. Advances in the refining process now yield OF and ETP copper that can meet or exceed 101% of this standard. (Ultra-pure copper has a conductivity of 5.865×107 S/m, 102.75% IACS.) Note that OF and ETP coppers have identical conductivity requirements. [6]
Oxygen plays a beneficial role for improving copper conductivity. During the copper smelting process, oxygen is deliberately injected into the melt to scavenge impurities that would otherwise degrade conductivity. [7]
There are advanced refining processes such as the Czochralski process than can achieve impurity levels below the C10100 specification by reducing copper grain density. [8] [9] [10] [11] At this time, there are currently no UNS/ASTM classifications for these specialty coppers and the IACS conductivity of these coppers is not readily available.[ citation needed ]
For industrial applications, oxygen-free copper is valued more for its chemical purity than its electrical conductivity. OF/OFE-grade copper is used in plasma deposition (sputtering) processes, including the manufacture of semiconductors and superconductor components, as well as in other ultra-high vacuum devices such as particle accelerators. In any of these applications, the release of oxygen or other impurities can cause undesirable chemical reactions with other materials in the local environment. [12]
The high-end speaker wire industry markets oxygen-free copper as having enhanced conductivity or other electrical properties that are supposedly advantageous to audio signal transmission. In fact, conductivity specifications for common C11000 (ETP) and higher-cost C10200 oxygen-free (OF) coppers are identical; [13] and even the much more expensive C10100 has only a one-percent higher conductivity—insignificant in audio applications. [13]
OFC is nevertheless sold for both audio and video signals in audio playback systems and home cinema. [13]
High-electrical-conductivity coppers are distinct from coppers deoxidized by the addition of phosphorus in the smelting process. Oxygen-free phosphorus-containing copper (CuOFP) is typically used for structural and thermal applications where the copper material will be subject to temperatures high enough to cause hydrogen embrittlement or more exactly steam embrittlement. Examples include welding/brazing rods and heat exchanger tubing. [14]
Copper alloys containing oxygen as an impurity (in the form of residual oxides present in the metal matrix) can be embrittled if exposed to hot hydrogen. The hydrogen diffuses through the copper and reacts with inclusions of Cu2O, forming H2O (water), which then forms pressurized water steam bubbles at the grain boundaries. This process can cause the grains to be forced away from each other and is known as steam embrittlement (because steam is produced, not because exposure to steam causes the problem).
CuOFP has been selected as corrosion-resistant material for the overpack of spent nuclear fuel in the KBS-3 concept developed in Sweden and Finland to dispose of high-level radioactive waste in crystalline rock formations.
Beryllium copper (BeCu), also known as copper beryllium (CuBe), beryllium bronze, and spring copper, is a copper alloy with 0.5–3% beryllium. Copper beryllium alloys are often used because of their high strength and good conductivity of both heat and electricity. It is used for its ductility, weldability in metalworking, and machining properties. It has many specialized applications in tools for hazardous environments, musical instruments, precision measurement devices, bullets, and some uses in the field of aerospace. Beryllium copper and other beryllium alloys are harmful carcinogens that present a toxic inhalation hazard during manufacturing.
Cupronickel or copper–nickel (CuNi) is an alloy of copper with nickel, usually along with small quantities of other elements added for strength, such as iron and manganese. The copper content typically varies from 60 to 90 percent.
In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge in one or more directions. Materials made of metal are common electrical conductors. The flow of negatively charged electrons generates electric current, positively charged holes, and positive or negative ions in some cases.
Brazing is a metal-joining process in which two or more metal items are joined by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal.
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. The tin increases the corrosion resistance and strength of the alloy, while the phosphorus increases its wear resistance and stiffness.
Monel is a group of alloys of nickel and copper, with small amounts of iron, manganese, carbon, and silicon. Monel is not a cupronickel alloy because it has less than 60% copper.
Hydrogen embrittlement (HE), also known as hydrogen-assisted cracking or hydrogen-induced cracking (HIC), is a reduction in the ductility of a metal due to absorbed hydrogen. Hydrogen atoms are small and can permeate solid metals. Once absorbed, hydrogen lowers the stress required for cracks in the metal to initiate and propagate, resulting in embrittlement. Hydrogen embrittlement occurs in steels, as well as in iron, nickel, titanium, cobalt, and their alloys. Copper, aluminium, and stainless steels are less susceptible to hydrogen embrittlement.
Glass-to-metal seals are a type of mechanical seal which joins glass and metal surfaces. They are very important elements in the construction of vacuum tubes, electric discharge tubes, incandescent light bulbs, glass-encapsulated semiconductor diodes, reed switches, glass windows in metal cases, and metal or ceramic packages of electronic components.
C41100 Lubaloy is a wrought copper alloy that is composed mainly of copper and zinc. Lubaloy possesses many favorable characteristics making it, and other types of brass, a popular choice in manufacturing. It is a source material in many processes including the creation of electrical components and bullet-making. There are both positive and negative health effects that are associated with the use of this material.
Copper has been used in electrical wiring since the invention of the electromagnet and the telegraph in the 1820s. The invention of the telephone in 1876 created further demand for copper wire as an electrical conductor.
2014 aluminium alloy (aluminum) is an aluminium-based alloy often used in the aerospace industry.
Steam and water analysis system (SWAS) is a system dedicated to the analysis of steam or water. In power stations, it is usually used to analyze boiler steam and water to ensure the water used to generate electricity is clean from impurities which can cause corrosion to any metallic surface, such as in boiler and turbine.
1050 aluminium alloy is an aluminium-based alloy in the "commercially pure" wrought family. As a wrought alloy, it is not used in castings. Instead, it is usually formed by extrusion or rolling. It is commonly used in the electrical and chemical industries, on account of having high electrical conductivity, corrosion resistance, and workability. 1050 alloy is also sometimes used for the manufacture of heat sinks, since it has a higher thermal conductivity than other alloys. It has low mechanical strength compared to more significantly alloyed metals. It can be strengthened by cold working, but not by heat treatment.
1060 aluminium alloy is an aluminium-based alloy in the "commercially pure" wrought family. It is fundamentally very similar to 1050 aluminium alloy, with the difference coming down to 0.1% aluminium by weight. However, while both 1050 and 1060 are covered by the same ISO standard, they are covered by different ASTM standards.
5154 aluminium alloy is an alloy in the wrought aluminium-magnesium family. As an aluminium-magnesium alloy, it combines moderate-to-high strength with excellent weldability. 5154 aluminium is commonly used in welded structures such as pressure vessels and ships. As a wrought alloy, it can be formed by rolling, extrusion, and forging, but not casting. It can be cold worked to produce tempers with a higher strength but a lower ductility. It is generally not clad.
5454 aluminium–magnesium alloy is an alloy in the wrought aluminium-magnesium family. It is closely related to 5154 aluminium alloy. As an aluminium-magnesium alloy, it combines moderate-to-high strength with excellent weldability. Like 5154, 5454 aluminium is commonly used in welded structures such as pressure vessels and ships. As a wrought alloy, it can be formed by rolling, extrusion, and forging, but not casting. It can be cold worked to produce tempers with a higher strength but a lower ductility. It is generally not clad.
5456 aluminium–magnesium alloy is an alloy in the wrought aluminium-magnesium family. While it is closely related to 5356 aluminium alloy, it is used in structural applications, like most other aluminium-magnesium alloys, and not as filler for welding. As a wrought alloy, it can be formed by rolling, extrusion, and forging, but not casting. It can be cold worked to produce tempers with a higher strength but a lower ductility. It is susceptible to exfoliation corrosion when held at temperatures above 65 °C (150 °F) for extended periods of time.
6005A aluminium alloy is an alloy in the wrought aluminium-magnesium-silicon family. It is closely related, but not identical, to 6005 aluminium alloy. Between those two alloys, 6005A is more heavily alloyed, but the difference does not make a marked impact on material properties. It can be formed by extrusion, forging or rolling, but as a wrought alloy it is not used in casting. It cannot be work hardened, but is commonly heat treated to produce tempers with a higher strength at the expense of ductility.
6262 aluminium alloy is an alloy in the wrought aluminium-magnesium-silicon family. It is related to 6162 aluminium alloy, but sees much more widespread use. It is notably distinct from 6162, and most other aluminium alloys, in that it contains lead in its alloy composition. It is typically formed by extrusion, forging, or rolling, but as a wrought alloy it is not used in casting. It can also be clad, but that is not common practice with this alloy. It cannot be work hardened, but is commonly heat treated to produce tempers with a higher strength but lower ductility.
The International Annealed Copper Standard (IACS) is a standard established in 1914 by the United States Department of Commerce. It is an empirically derived standard value for the electrical conductivity of commercially available copper.
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