An alloy based on copper with a certain amount of other elements added.Copper alloy has medium strength, easy processing, better fatigue resistance, beautiful color, and good conductivity, thermal conductivity and corrosion resistanceHeavy non-ferrous metalsAn important branch of materials.Copper alloys are widely used in various industrial sectors. Its output is only second to steel and aluminum, and it is the third largest alloy category in metal materials.
Copper alloy has good electrical and thermal conductivity, medium mechanical properties and highchemical stabilityThe cutting performance is poor.The properties of various copper alloys vary greatly with the type and amount of alloying elements added.
Electrical conductivity
Copper alloys are good electrical conductors.The conductivity of pure copper is 100%~103% IACS (see copper for the definition of IACS).The addition of any solution alloy element will reduce the conductivity of copper. The reduction of unit atomic concentration mainly depends on the influence of alloy elements on copper lattice, and increases with the increase of the addition amount in the solution range.
color and lustre
Copper has a beautiful rose red color. With the addition of zinc, aluminum, nickel and other alloy elements, its color changes to golden yellow and silver white, so it can be used to make various decorations and coins.
strengthCopper alloy has medium strength, and the tensile strength of industrial pure copper in annealing state is about 240MPa.The strength of copper alloys can be improved by means of solution strengthening, work hardening, precipitation hardening (including metastable decomposition), grain refinement and dispersion strengthening.Cold working can not only be used to harden the alloy alone, but also can work together with precipitation hardening or metastable decomposition to achieve strengthening.
Adding any solid solution alloy element to copper will improve the strength of copper. The strengthening degree of unit atomic concentration on copper shear modulus is related to the difference between the added element and the atomic size of copper.
MachinabilityGenerally, the machinability of copper alloys is poor. Adding lead, sulfur, tellurium and other elements can improve the machinability of copper alloys.According to the cutting performance,Wrought copper alloyIt can be divided into three categories: (1) those with machinability of more than 70%Free cutting alloy, including free cutting copper containing lead, sulfur or tellurium, free cutting brass, all kinds of lead brass, bronze and zinc white copper containing lead about 2%, etc;(2) Medium machinability alloy with machinability of 30%~60%, including brass with copper content of 60%~85%, bronze and zinc white copper with lead content of about 1%;(3) Hard to cut alloys with machinability below 20%, including low zinc brass, zinc white copper, tin bronzeCopper nickel alloyAnd beryllium bronze, etc. (generally compared with 100% machinability of free cutting brass).
Stress relaxation resistance
The stress relaxation resistance of pure copper is poor, and the addition of soluble elements that can increase the softening temperature of copper or whose atomic size differs greatly from that of copper can improve the stress relaxation resistance of copper.Beryllium bronze, white copper and zinc white copper have the best stress relaxation resistance, followed by tin bronze and tin brass, followed by silicon bronze, and ordinary brass has the worst stress relaxation resistance.In terms of stress relaxation capacity, the maximum service temperature of copper alloy is about 200 ℃.Brass with low stress relaxation resistance can only be used to make parts slightly higher than room temperature, beryllium bronze and tin, silicon, aluminum or zinc ternaryCopper nickel alloyEven at the highest temperature commonly used by devices, its ability to resist stress relaxation is still quite high.[1]
classification
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According to the types of alloy elements added, copper alloys can be divided into brass, bronze and white copper.Brass is a copper alloy with zinc as the main alloy element;White copper is a copper alloy with nickel as the main alloying element;Bronze is a copper alloy other than brass and white copper.In order to be consistent with international standards, the Chinese national standard GB 11086-89 divides copper and copper alloys into copper, copper zinc alloy (brass), copper tin alloy (bronze), copper aluminum alloy, copper nickel alloyCu Ni Zn alloy(nickel silver) and special copper alloys.At present, the original classification method is still used in industry.In addition, copper alloy materials can also be divided into copper solder, superplastic copper alloy and functional copper alloy according to their applications and properties.
purpose
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Some brass, bronze and white copper are widely used to manufacture automotive radiators, heat exchangers and components of various industrial devices that need to pass through or along metal quickly to conduct heat.Brass, some bronzes and white copper are used in the manufacture of condensers, pipes, valves and other gas transmission liquid systems that need corrosion resistance.Special copper alloys, such as copper brazing filler metal, superplastic copper alloy, are used to make various devices through superplastic forming, and functional copper alloys are used to make coins, decorations, musical instruments, etc.In addition, various copper alloys are also indispensable materials for the machinery industry, which are used to process various mechanical parts such as springs, fasteners, pads, etc.
example
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Copper beryllium alloy
Copper beryllium alloy is a supersaturated solid solution copper base alloy, which is a non-ferrous alloy with good combination of mechanical properties, physical properties, chemical properties and corrosion resistance. After solution and aging treatment, it has high strength limit, elastic limit, yield limit and fatigue limit equivalent to special steel, and also has high conductivity, thermal conductivity, high hardness and wear resistance,With high creep resistance and corrosion resistance, it is widely used in manufacturing various mold inserts, replacing steel to make molds with high precision and complex shapes, welding electrode materials die-casting machines, injection molding machine punches, wear-resistant and corrosion resistant workpieces, micro electric brushes, mobile phone batteries, computer connectors, various switch contacts, etc. It is an indispensable important industrial material in the national economic construction.
1) Chemical composition of copper beryllium alloy
The chemical composition and mechanical properties of copper beryllium alloy are shown in the table:
2) Characteristics of copper beryllium alloy
① Copper beryllium alloy is a supersaturated solid solution copper base alloy with good mechanical, physical and chemical properties. The alloy density is 8.3 g/cm, conductivity ≥ 18% IACS, thermal conductivity ≥ 105 w/m · k (20 ℃), non-magnetic, hardness 36 ～ 42 HRC.After solution aging treatment, it has high strength, wear resistance, heat resistance, cold resistance, elastic limit and fatigue limit, small elastic hysteresis, no spark when hit, and is easy to weld and braze.
② Copper beryllium alloy has excellent corrosion resistance in atmosphere, fresh water and sea water. The corrosion resistance rate in sea water is (1.1~1.4) × 10 mm/year, and the corrosion depth is (10.9~13.8) × 10 mm/year.After corrosion, the strength and elongation of the alloy have no change.In sulfuric acid medium, the annual corrosion depth is 0.0012~0.1175 mm in sulfuric acid with concentration less than 80% (room temperature), and the corrosion is slightly accelerated when the concentration is more than 80%.
3) Heat treatment process of copper beryllium alloy
① Solution treatment: the beryllium copper workpiece is heated to 800 ℃~815 ℃, and kept at constant temperature for 2~3 h, so that beryllium is completely dissolved in copper, forming a uniform distribution state.
② Quenching process: after being discharged from the furnace, the workpiece is cooled rapidly in water so that beryllium atoms can not diffuse in time to form an oversaturated state.
③ Aging treatment: heat the supersaturated workpiece in the vacuum heat treatment furnace to a lower aging temperature of 340 ℃± 5 ℃. Because the supersaturated state is unstable, additional beryllium atoms diffuse and precipitate in a short distance. After holding for 2-3 hours, the excess beryllium and copper precipitated will reach balance, and the mechanical performance at this time will be significantly improved.
4) Application of copper beryllium alloy
Copper beryllium alloy has excellent usability and processing properties.Commonly used for manufacturingZinc base alloyThe inner inserts, die centers, die casting punches, hot runner cooling systems, heat transfer nozzles, integral cavities of blow molding molds, wear plates, etc. of die-casting molds, drawing molds for stainless steel utensils, and plastic injection molding molds.It is also used to manufacture various elastic elements such as diaphragms, bellows, spring tubes, springs, etc.[2]
brief history
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Copper alloy is one of the oldest metal materials.According to the cultural relics unearthed in Egypt and West Asia, forged natural copper pieces appeared around 6000 BC;In 5000 BC, bronze ware was used.In the first century BC, the people living near the coast of the Black Sea used zinc ore to add copper to make brass.In the 16th century, E. Eberner, an Englishman, proposed to produce brass by adding zinc directly to copper.
In the Shang Dynasty 1200 BC, China was able to reasonably use four metals, namely gold, copper, tin and lead. Bronze (copper tin alloy) smelting and casting technology has reached a mature stage.In the first century BC, the Western Han Dynasty began to use zinc bearing ores to refine brass.3. During the Eastern Han Dynasty and the Three Kingdoms in the 4th century, the "personal" recorded in Zhang Yi's book Guangya was one of the white copper (copper zinc nickel alloy).4. In the 5th century, alchemists in the Northern and Southern Dynasties were able to use calamine, that is, zinc carbonate ore, to directly add copper to produce brass.In the Ming Dynasty, zinc was directly added into copper nickel alloy to make zinc white copper, which was exported to Europe and later imitated by Germany. Some people abroad mistakenly named it German silver.
At the end of the 19th century, with the mass production of aluminum, aluminum bronze began to come out.In the 1920s, M.G. Corson, an American, and O. Dahl, a German, developed beryllium bronze with high strength and good conductivity, and developed new varieties of precipitation hardening in copper alloys.In the mid-1970s, J.T. Plew, an American, developed a metastable decomposition copper nickel tin alloy that was used in industry and had similar properties to beryllium bronze on the basis of previous studies.
