Copper Alloy

What Is Copper Alloy?

Copper alloy (copper alloy) is an alloy formed by adding one or more other elements to pure copper as the matrix. Pure copper is purple-red, also known as red copper. Commonly used copper alloys are divided into three categories: brass, bronze, and cupronickel.

Introduction

Brass is a copper alloy with zinc as the main additive element. It has a beautiful yellow color and is collectively referred to as brass. Copper-zinc binary alloy is called ordinary brass or simple brass.

Brass with more than three yuan is called special brass or complex brass. Brass alloys containing less than 36% zinc are composed of solid solution and have good cold working properties.

For example, brass with a zinc content of 30% is often used to make bullet casings, commonly known as bullet casing brass or seven-three brass.

Brass alloys with a zinc content between 36% and 42% are composed of solid solutions and the most commonly used is the six-four brass with 40% zinc.

In order to improve the performance of ordinary brass, other elements such as aluminum, nickel, manganese, tin, silicon, lead, etc. are often added.

Aluminum can increase the strength, hardness and corrosion resistance of brass, but reduce its plasticity. It is suitable for marine condensers and other corrosion-resistant parts.

Tin can improve the strength of brass and its corrosion resistance to seawater, so it is called naval brass and is used for ship thermal equipment and propellers.

Lead can improve the cutting performance of brass; this kind of free-cutting brass is often used as parts of clocks and watches.

Brass castings are often used to make valves and pipe fittings. The explosion-proof crescent wrench for fire hydrants commonly used in ships is made of brass and aluminum.

species

Cupronickel

A copper alloy with nickel as the main additive element. The copper-nickel binary alloy is called ordinary cupronickel; the cupronickel alloy with elements such as manganese, iron, zinc, and aluminum is called complex cupronickel.

Industrial copper-nickel alloy is divided into two categories: structural copper-nickel alloy and electrical white copper-nickel alloy. Structural white copper is characterized by good mechanical properties and corrosion resistance, and beautiful color. This kind of cupronickel is widely used in the manufacture of precision machinery, eyewear accessories, chemical machinery and ship components.

Electrical white copper generally has good thermoelectric properties. Manganese copper, constantan, and test copper are manganese-nickel alloys with different manganese content. They are used to manufacture precision electrical instruments, varistors, precision resistors, strain gauges, thermocouples, etc.

brass

Brass is an alloy composed of copper and zinc. If it is only composed of copper and zinc, it is called ordinary brass. Brass is often used to make valves, water pipes, connecting pipes for internal and external air conditioners, and radiators.

If it is a variety of alloys composed of two or more elements, it is called special brass. Such as copper alloys composed of lead, tin, manganese, nickel, iron, and silicon. Special brass is also called special brass. It has high strength, high hardness and strong chemical resistance. The mechanical properties of cutting are also outstanding.

Brass has strong wear resistance. The seamless copper tube drawn from brass is soft and has strong wear resistance. Brass seamless pipes can be used for heat exchangers and condensers, cryogenic pipelines, and subsea transportation pipes. Manufacture of sheets, bars, bars, pipes, casting parts, etc. The copper content is 62%～68%, the plasticity is strong, and it is used to manufacture pressure-resistant equipment.

According to the different types of alloying elements contained in brass, brass is divided into two types: ordinary brass and special brass.

Brass used for pressure processing is called deformed brass. Brass is a copper alloy with zinc as the main additive element. It has a beautiful yellow color and is collectively referred to as brass.

Copper-zinc binary alloy is called ordinary brass or simple brass.

Brass with more than three yuan is called special brass or complex brass.

Brass alloys with a zinc content of less than 36% are composed of solid solution and have good cold working properties. For example, brass with a zinc content of 30% is commonly used to make bullet cases, commonly known as bullet case brass or seven-three brass.

Brass alloys with a zinc content between 36% and 42% are composed of solid solutions and the most commonly used is the six-four brass with 40% zinc.

In order to improve the performance of ordinary brass, other elements such as aluminum, nickel, manganese, tin, silicon, lead, etc. are often added. Aluminum can increase the strength, hardness and corrosion resistance of brass, but reduce its plasticity. It is suitable for marine condensers and other corrosion-resistant parts.

Tin can improve the strength of brass and its corrosion resistance to seawater, so it is called naval brass and is used for ship thermal equipment and propellers.

Lead can improve the cutting performance of brass; this kind of free-cutting brass is often used as watch parts.

Brass castings are often used to make valves and pipe fittings.

bronze

Bronze is the earliest alloy used in my country and has a history of more than 3,000 years.

Bronze originally refers to copper-tin alloy, and later copper alloys other than brass and cupronickel are called bronze, and the name of bronze is often prefixed with the name of the first major additive element. Tin bronze has good casting performance, anti-friction performance and good mechanical performance. It is suitable for manufacturing bearings, worm gears, gears, etc. Lead bronze is a bearing material widely used in modern engines and grinders.

Aluminum bronze has high strength, good wear resistance and corrosion resistance. It is used to cast high-load gears, shaft sleeves, and marine propellers. Phosphor bronze has high elastic limit and good conductivity, and is suitable for manufacturing precision springs and electrical contact components. Beryllium bronze is also used to make non-sparking tools used in coal mines and oil depots.

Beryllium copper is a supersaturated solid solution copper-based alloy with good mechanical properties, physical properties, chemical properties and corrosion resistance; powder metallurgy production is aimed at tungsten steel, high carbon steel, high temperature resistant super hard alloy molds when electrical corrosion is required , Due to the large loss and slow speed of ordinary electrodes, tungsten copper is an ideal material. Flexural strength ≥667Mpa.

Pure copper

High-quality red copper has high purity, fine structure and extremely low oxygen content. No pores, trachoma, looseness, excellent electrical conductivity, suitable for electro-etching molds, after heat treatment process, the electrode has no directionality, suitable for fine punching and fine punching.

Reference parameters: Cu≥99.95%O<003 Conductivity≥57ms/m Hardness≥85.2HV

classification

There are three classification methods for copper alloys:

• By alloy

According to the alloy system, it can be divided into unalloyed copper and alloyed copper. Unalloyed copper includes high-purity copper, toughened copper, deoxidized copper, oxygen-free copper, etc. Traditionally, people refer to unalloyed copper as red copper or pure copper. It is called red copper, and other copper alloys belong to alloy copper. my country and Russia divide copper alloys into brass, bronze and cupronickel, and then divide the alloy series into small ones in the big category.

• By function

Divided by function, there are copper alloys for electrical and thermal conductivity (mainly unalloyed copper and microalloyed copper), copper alloys for structure (almost all copper alloys), and corrosion-resistant copper alloys (mainly tin brass, aluminum brass) , Various non-white copper, aluminum bronze, titanium bronze, etc.) wear-resistant copper alloys (mainly complex brass containing lead, tin, aluminum, manganese and other elements, aluminum bronze, etc.), free-cutting copper alloys (copper-lead, copper- Tellurium, copper-antimony alloys), elastic copper alloys (mainly antimony bronze, aluminum bronze, beryllium bronze, titanium bronze, etc.) damping copper alloys (high manganese copper alloys, etc.), artistic copper alloys (pure copper, simple single copper, etc.) Tin bronze, aluminum bronze, cupronickel, etc.). Obviously, many copper alloys have multiple functions.

• Material forming method

According to the material forming method, it can be divided into cast copper alloy and deformed copper alloy. In fact, many copper alloys can be used for both casting and deformation processing. Generally, deformed copper alloys can be used for casting, but many cast copper alloys cannot be deformed such as forging, extrusion, deep drawing, and drawing. Cast copper alloys and deformed copper alloys can be subdivided into casting copper, brass, bronze and cupronickel.

application

Electrical industry

Power transmission

A large amount of high-conductivity copper needs to be consumed in power transmission, which is mainly used for power wires and cables, bus bars, transformers, switches, plug-in components, and connectors.

In the process of wire and cable power transmission, electrical energy is wasted in vain due to resistance heating. From the perspective of energy saving and economy, the world is currently promoting the “”best cable cross section”” standard. The popular standard in the past, simply from the perspective of reducing the investment in one installation, in order to minimize the cross-section of the cable, to determine the minimum allowable size of the cable in order to avoid dangerous overheating at the rated current required by the design. Cable laid according to this standard, although the installation cost is low; but in the long-term use process, the resistance energy consumption is relatively large. The “”Best Cable Cross Section”” standard takes into account the two factors of one-time installation cost and power consumption, and appropriately enlarges the cable size to achieve the purpose of energy saving and the best comprehensive economic benefits. According to the new standard, the cable cross-section is often more than doubled than the old standard, and the energy saving effect of about 50% can be obtained.

In the past period of time in my country, due to the short supply of steel, considering that the proportion of aluminum is only 30% of copper, measures have been taken to replace copper with aluminum in overhead high-voltage transmission lines that hope to reduce weight. Underground cables. In this case, compared with copper, aluminum has the disadvantages of poor conductivity and larger cable size, which pales in comparison.

For the same reason, it is also a wise choice to replace the old aluminum winding transformer with an energy-saving and efficient copper winding transformer.

Motor manufacturing

In motor manufacturing, copper alloys with high conductivity and high strength are widely used. The main copper parts are the stator, rotor and shaft head. In large motors, the windings need to be cooled by water or hydrogen, which is called dual water internal cooling or hydrogen cooling motors, which requires a large length of hollow wire.

Electric motors are a large consumer of electrical energy, accounting for about 60% of the total electrical energy supply. The accumulated electricity cost of a motor is very high. Generally, the cost of the motor is reached within 500 hours of initial operation, which is equivalent to 4 to 16 times the cost within a year, and can reach 200 times the cost during the entire working life. A small increase in motor efficiency can not only save energy, but also obtain significant economic benefits. The development and application of high-efficiency motors is currently a hot topic in the world.

Because the energy consumption inside the motor mainly comes from the resistance loss of the winding; therefore, increasing the cross-section of the copper wire is a key measure for the development of high-efficiency motors. Compared with the first developed high-efficiency motors and traditional motors, the use of copper windings has increased by 25-100%. The U.S. Department of Energy is funding a development project to produce motor rotors using copper-cast technology.

Communication Cable

Since the 1980s, due to the advantages of large current-carrying capacity of optical fiber cables, copper cables have been continuously replaced on communication trunk lines, and their applications have been rapidly promoted. However, a large amount of copper is still needed to convert electrical energy into light energy and the lines input to users. With the development of the communications industry, people are increasingly dependent on communications, and the demand for optical fiber cables and copper wires will continue to increase.
Residential electrical wiring

With the improvement of people’s living standards in our country, home appliances are rapidly spreading, and the residential electricity load is increasing rapidly. As shown in Figure 6.6, the residential electricity consumption in 1987 was 26.96 billion kWh (l kWh = 1 kilowatt? hour), and it soared to 113.1 billion kWh in 1996, an increase of 3.2 times. Nevertheless, there is still a big gap compared with developed countries. For example, in 1995, the per capita electricity consumption in the United States was 14.6 times that of my country, and Japan was 8.6 times that of my country. my country’s residential electricity consumption will continue to develop greatly in the future. It is expected that from 1996 to 2005, there will be an increase of l. 4 times.

electronics industry

The electronics industry is an emerging industry, and in the course of its flourishing development, new steel products and new application areas have been continuously developed. Its application has developed from electric vacuum devices and printed circuits to microelectronics and semiconductor integrated circuits.

Electric vacuum device

Electric vacuum devices are mainly high-frequency and ultra-high-frequency launch tubes, waveguides, magnetrons, etc. They require high-purity oxygen-free copper and dispersion-strengthened oxygen-free copper.

Printed circuit

The copper printed circuit uses copper foil as the surface and is pasted on the supporting plastic board; the circuit wiring diagram is printed on the copper plate by photographing; the redundant part is removed by etching to leave the interconnected circuit. Then, punch holes in the connection between the printed circuit board and the outside, insert the terminals of the discrete components or other parts, and solder them on this port, so that a complete circuit is assembled. If immersion plating is used, all joints can be welded at one time. In this way, for those occasions that require fine layout of circuits, such as radios, televisions, computers, etc., the use of printed circuits can save a lot of wiring and fixed circuit labor; therefore, it is widely used and requires a large amount of copper foil to be consumed. In addition, various copper-based brazing materials with low price, low melting point and good fluidity are needed in the circuit connection.
integrated circuit

The core of microelectronics technology is integrated circuits. Integrated circuit refers to a micro-miniature circuit that uses semiconductor crystal material as the substrate (chip) and uses special process technology to integrate the components and interconnections that make up the circuit inside, on or on the substrate. This kind of microcircuit is thousands of times smaller in size and weight than the most compact discrete component circuit in structure. Its appearance caused a huge revolution in computers and became the basis of modern information technology. The ultra-large-scale integrated circuits that have been developed can make hundreds of thousands or even more than one million transistors on a single chip area smaller than Xiaomu’s nails. The internationally renowned computer company IBM (International Business Machines Corporation) has used copper instead of aluminum in silicon chips as interconnect lines, and has made breakthrough progress. This new type of copper-based microchip can achieve a 30% performance gain, and the line size of the circuit can be reduced to 0.12 microns, which enables the number of integrated transistors on a single chip to reach 2 million. This is the application of ancient copper metal in the latest technology field of semiconductor integrated circuits, creating a new situation .

Lead frame

In order to protect the normal operation of the integrated circuit or hybrid circuit, it needs to be packaged; and during packaging, a large number of connectors in the circuit are led out of the sealed body. These leads are required to have a certain strength, and constitute the supporting framework of the integrated package circuit, which is called a lead frame. In actual production, for high-speed mass production, the lead frame is usually continuously stamped on a metal strip in a specific arrangement. Frame materials account for 1/3 to 1/4 of the total cost of integrated circuits, and the amount is large; therefore, there must be a low cost.
Copper alloys are inexpensive, have high strength, electrical conductivity and thermal conductivity, and are excellent in processability, brazing and corrosion resistance. Through alloying, their performance can be controlled in a wide range, which can better meet the performance of the lead frame. Requirements, it has become an important material for lead frames. It is currently the most used material of copper in microelectronic devices.

Transportation industry

Ship

Due to good seawater corrosion resistance, many copper alloys, such as aluminum bronze, manganese bronze, aluminum brass, gunmetal (tin-zinc bronze), white steel, and nickel-copper alloy (Monel) have become standard materials for shipbuilding. Generally, copper and copper alloy account for 2 to 3% of the weight of warships and merchant ships.

The propellers of warships and most large commercial ships are made of aluminum bronze or brass. Each propeller of a large ship weighs 20-25 tons. The propellers of the Queen Elizabeth and Queen Mary aircraft carriers each weigh 35 tons. “Admiral” gunmetal is commonly used for the heavy tail shaft of large ships, and the same material is used for the tapered bolts of the rudder and propeller. Steel and copper alloys are also used extensively in engine and boiler rooms. The world’s first nuclear-powered commercial ship used 30 tons of cupronickel condenser tubes. Aluminum brass pipes are used as large heating coils for oil tanks. There are 12 such oil storage tanks on 100,000-ton ships, and the corresponding heating system is quite large. The electrical equipment on the ship is also very complicated. Engines, motors, communication systems, etc. almost entirely rely on copper and copper alloys to work. The cabins of large and small ships are often decorated with steel and copper alloys. Even for wooden boats, it is best to use steel alloy (usually silicon bronze) screws and nails to fix the wooden structure. Such screws can be mass-produced by rolling.
In order to prevent the ship’s hull from being fouled by marine organisms and affecting navigation, copper coating is often used for protection; or copper-containing paint is used to solve the problem.

In World War II, in order to prevent German magnetic mines from attacking ships, an anti-magnetic mine device was developed. A copper strip was attached around the steel hull, and electric current was applied to neutralize the ship’s magnetic field. Does not detonate mines. Since 1944, all Allied ships, a total of about 18,000, have been equipped with this demagnetization device and have been protected. Some large battleships require large amounts of copper for this purpose. For example, one of them uses copper wire to be 28 miles long and weighs about 30 tons.

car

The copper used in automobiles is 10-2I kilograms per car, which varies with the type and size of the car. For small cars, it accounts for about 6-9% of its own weight. Copper and copper alloys are mainly used in radiators, brake system pipelines, hydraulic devices, gears, bearings, brake friction linings, power distribution and power systems, gaskets, and various joints, accessories and trims. Among them, the radiator is the most used steel. Modern tube-belt radiators are welded with brass strips to form radiator tubes, and thin copper strips are bent to form heat sinks.
In order to further improve the performance of copper radiators and enhance its competitiveness against aluminum radiators, many improvements have been made. In terms of material, trace elements are added to copper to increase its strength and softening point without loss of thermal conductivity, thereby reducing the thickness of the strip and saving the amount of steel used; in terms of manufacturing process, high frequency is used. Or laser welding copper tubes, and using steel brazing instead of lead-contaminated soft soldering to assemble the radiator core. The results of these efforts are shown in Table 6.2. Compared with brazed aluminum radiators, under the same heat dissipation conditions, that is, under the same pressure drop of air and coolant, the new copper radiator is lighter in weight and significantly smaller in size; Coupled with the good corrosion resistance and long service life of steel, the advantages of copper radiators are even more obvious. In addition, for the sake of environmental protection, vigorously promote and develop electric vehicles, the amount of steel used for each vehicle will be doubled.
railway

The electrification of railways requires a lot of copper and copper alloys. Over 2 tons of special-shaped copper wires are required for each kilometer of overhead conductors. In order to increase its strength, a small amount of copper (about 1%) or silver (about of%) is often added. In addition, the motors, rectifiers, control, braking, electrical and signal systems on the train all rely on copper and copper alloys to work.

aircraft

The navigation of the aircraft is also inseparable from copper. For example, the wiring, hydraulic, cooling and pneumatic systems in the aircraft need to use copper materials, the bearing retainers and landing gear bearings are made of aluminum bronze pipes, the navigation instruments use antimagnetic steel alloys, and many instruments use broken copper elastic elements and so on.

light industry

Light industrial products are closely related to people’s lives, with a wide variety of varieties. Because of its good comprehensive properties, copper can be seen everywhere. Here are just a few examples:

Air conditioner and freezer

The temperature control function of the air conditioner and the refrigerator is mainly realized by the evaporation and condensation of the copper tube of the heat exchanger. The size and heat transfer performance of the heat exchange heat transfer tube determine to a large extent the efficiency and miniaturization of the entire air conditioner and refrigeration device. The special-shaped copper pipes with high thermal conductivity are used in these machines. Utilizing the good processing performance of steel, we develop and produce radiator tubes with inner grooves and high fins, which are used to manufacture heat exchangers in air conditioners, refrigerators, chemicals and waste heat collection devices, which can enable new heat exchange. The total thermal conductivity of the heat exchanger is increased to 2 to 3 times that of ordinary tubes and 1.2 to 1.3 times that of ordinary low-fin tubes. It has been used in China, which can save 40% of copper and reduce the volume of heat exchanger by 1/ 3 or more.

Clock

Most of the working parts of the clocks, timers and devices with clock mechanism produced are made of “”clock brass””. The alloy contains 1.5-2% lead, which has good processing properties and is suitable for large-scale production. For example, gears are cut out of long extruded brass rods, flat wheels are punched out of strips of corresponding thickness, brass or other copper alloys are used to make engraved clock faces, screws and joints, and so on. A large number of cheap watches are made of gunmetal (tin-zinc bronze) or plated with nickel silver (white copper). Some famous big clocks are made of steel and copper alloys. The hour hand of the British “Big Ben” uses a solid gunmetal rod, and the minute hand uses a 14-foot-long copper tube.

A modern watch factory, using copper alloy as the main material, using presses and precise mold processing, can produce 10,000 to 30,000 watches per day at a very low cost.

papermaking

In the current information-changing society, paper consumption is huge. The surface of the paper looks simple, but the papermaking process is very complicated. It requires many steps and uses many machines, including coolers, evaporators, beaters, paper machines, and so on. Many of these components, such as various heat exchange tubes, rollers, percussion rods, semi-liquid pumps and wire mesh, are mostly made of steel alloys.

For example, the Fourdrinier paper machine used will spray the prepared pulp onto a fast-moving mesh cloth with fine meshes (40-60 mesh). The mesh cloth is woven from brass and phosphor bronze wires. Its width is very large, generally over 20 feet (6 meters), and it is required to be completely straight. The mesh cloth moves on a series of small brass or copper rollers, and when the paper pulp sprayed on it passes through, moisture is sucked out from below. The net vibrates at the same time to bond the small fibers in the pulp together. The mesh size of a large paper machine is very large, which can reach a width of 26 feet 8 inches (8.1 meters) and a length of 100 feet (3 0.5 meters). Wet pulp not only contains water, but also contains chemicals used in the papermaking process, which is very corrosive. In order to ensure the quality of paper, the requirements for the mesh material are very strict. Not only must it have high strength and elasticity, but also must be resistant to pulp corrosion, and copper alloys are fully competent.

print

In printing, copper plates are used for photo-engraving. The polished copperplate is sensitized with photosensitive emulsion, and then photographed and imaged on it. The exposed copper plate needs to be heated to harden the glue. In order to avoid thermal softening, copper often contains a small amount of silver or arsenic to increase the softening temperature. Then, the plate is etched to form a printed surface with uneven dot patterns.
In the automatic typesetting machine, the layout of the brass font block is used to make the pattern, which is another important use of copper in printing. The font block is usually leaded brass, and sometimes copper or bronze is also used.

medicine

In the pharmaceutical industry, all kinds of steaming, boiling, and vacuum devices are made of pure copper. In medical equipment, zinc cupronickel is widely used. Copper alloy is also a common material for spectacle frames, etc.

Construction industry

Because r copper water pipe has many advantages such as beautiful and durable, convenient installation, safety and fire prevention, health care, etc., it has a significantly superior price-performance ratio compared with galvanized steel pipes and plastic pipes. In residential and public buildings, water supply, heat supply, gas supply, and fire sprinkler systems are increasingly favored by people and become the current preferred materials. In developed countries, copper water supply systems already account for a large proportion. The Manhattan Building in New York, USA, which is known as the sixth tallest building in the world, only uses 60,000 feet (1 km) of copper pipes for the water system. In Europe, steel pipes for drinking water are consumed very much. The consumption of copper pipes for drinking water in the United Kingdom averages 1.6 kg per person per year, and 0.2 kg in Japan. Because galvanized steel pipes are prone to corrosion, many countries have explicitly banned them. Hong Kong banned its use as early as January 1996, and Shanghai also implemented it in May 1998. It is imperative for my country to promote the use of copper pipe systems in housing construction.

aerospace

Recently, some materials with higher critical temperature have been discovered, called “”high-temperature superconducting materials””. Most of them are composite oxides. One of the earlier discovered and well-known is the lead-containing copper-based oxide (YB2 Cu3 O7), which has a critical temperature of 90K and can work at the temperature of liquid nitrogen. However, materials with a critical temperature near room temperature have not yet been obtained; and these materials are difficult to make into large objects, and the current density that they can pass to maintain superconductivity is not high enough. Therefore, it has not been applied in strong current situations, and further research and development are needed.
In aerospace technology, rockets, satellites and space shuttles, in addition to microelectronic control systems and instruments, instrumentation equipment, many key components also use copper and copper alloys. For example, the inner village of the combustion chamber and thrust chamber of a rocket engine can be cooled by the excellent thermal conductivity of steel to keep the temperature within the allowable range. The combustion chamber lining of the Ariane 5 rocket is made of copper-silver-combined gold. 360 cooling channels are processed in this lining, and liquid hydrogen is introduced for cooling when the rocket is launched.
In addition, copper alloy is also a standard material for bearing members in satellite structures. The solar wing panels on satellites are usually made of an alloy of copper and several other elements.

Casting process

The crystallization characteristics of copper alloys of various compositions are different, the casting properties are different, and the casting process characteristics are also different.

• 1. Tin bronze: The crystallization characteristic is a large crystallization temperature range and a wide solidification area. In terms of casting performance, the fluidity is poor, shrinkage is easy to occur, and it is not easy to oxidize. The characteristic of the process is that the thick wall parts adopt directional solidification (sequential solidification), and the complex thin wall parts and general thick wall parts adopt simultaneous solidification.
• 2. Aluminum bronze and aluminum brass: The crystallization characteristic is that the crystallization temperature range is small, and it is the characteristic of solidification layer by layer. In terms of casting performance, fluidity is good, concentrated shrinkage is easy to form, and it is easy to oxidize. The process feature is that the aluminum bronze pouring system is bottom injection type, and the aluminum brass pouring system is open type.
• 3. Silicon brass: The crystalline characteristic is between tin bronze and aluminum bronze. The best casting performance (in special brass). The process is characterized by sequential solidification process, mid-injection gating system, and small size of the dark riser

Physical properties

• (1) Excellent physical and chemical properties. Pure copper has excellent electrical and thermal conductivity, and copper alloys have excellent electrical and thermal conductivity. Copper and copper alloys have high corrosion resistance to the atmosphere and water. Copper is a diamagnetic substance.
• (2) Good processing performance, good plasticity, easy to cold and hot forming; cast copper alloy has good casting performance.
• (3) It has some special mechanical properties such as excellent anti-friction and wear resistance (such as bronze and some brass), high elastic limit and fatigue limit (such as beryllium bronze, etc.).
• (4) Beautiful color 2. (Red copper)
  Pure copper is a rose-red metal, and the surface becomes purple after a copper oxide film is formed on the surface, so industrial pure copper is often called red copper or electrolytic copper. The density is 8-9g/cm² and the melting point is 1083°C. Pure copper has good electrical conductivity and is widely used in the manufacture of wires, cables, brushes, etc.; it has good thermal conductivity and is often used to manufacture magnetic instruments and meters that must be protected from magnetic interference, such as compasses and aviation instruments; it has excellent plasticity and is easy to heat Pressure and cold pressure processing can be made into copper materials such as tubes, rods, wires, strips, strips, plates, and foils. There are two types of pure copper products: smelted products and processed products. See Table 1 and Table 2, respectively.

Casting process

The crystallization characteristics of copper alloys of various compositions are different, the casting properties are different, and the casting process characteristics are also different.

• 1. Tin bronze: The crystallization characteristic is a large crystallization temperature range and a wide solidification area. In terms of casting performance, the fluidity is poor, shrinkage is easy to occur, and it is not easy to oxidize. The characteristic of the process is that the thick wall parts adopt directional solidification (sequential solidification), and the complex thin wall parts and general thick wall parts adopt simultaneous solidification.
• 2. Aluminum bronze and aluminum brass: The crystallization characteristic is that the crystallization temperature range is small, and it is the characteristic of solidification layer by layer. In terms of casting performance, fluidity is good, concentrated shrinkage is easy to form, and it is easy to oxidize. The process feature is that the aluminum bronze pouring system is bottom injection type, and the aluminum brass pouring system is open type.
• 3. Silicon brass: The crystalline characteristic is between tin bronze and aluminum bronze. The best casting performance (in special brass). The process is characterized by sequential solidification process, mid-injection gating system, and small size of the dark riser

Physical properties

• (1) Excellent physical and chemical properties. Pure copper has excellent electrical and thermal conductivity, and copper alloys have excellent electrical and thermal conductivity. Copper and copper alloys have high corrosion resistance to the atmosphere and water. Copper is a diamagnetic substance.

 

• (2) Good processing performance, good plasticity, easy to cold and hot forming; cast copper alloy has good casting performance.

  Copper alloys have medium strength, and the tensile strength of industrial pure copper in the annealed state is about 240 MPa. Through solid solution strengthening, work hardening, precipitation hardening (including metastable decomposition), grain refinement and dispersion strengthening, the strength of copper alloys can be improved. Cold working can be used alone to harden the alloy, or it can work together with precipitation hardening or metastable decomposition to achieve strengthening.

• (3) It has some special mechanical properties such as excellent anti-friction and wear resistance (such as bronze and some brass), high elastic limit and fatigue limit (such as beryllium bronze, etc.).

 

• (4) Beautiful color

Pure copper is a rose-red metal, and the surface becomes purple after a copper oxide film is formed on the surface, so industrial pure copper is often called red copper or electrolytic copper. The density is 8-9g/cm² and the melting point is 1083°C. Pure copper has good electrical conductivity and is widely used in the manufacture of wires, cables, brushes, etc.; it has good thermal conductivity and is often used to manufacture magnetic instruments and meters that must be protected from magnetic interference, such as compasses and aviation instruments; it has excellent plasticity and is easy to heat Pressure and cold pressure processing can be made into copper materials such as tubes, rods, wires, strips, strips, plates, and foils. There are two types of pure copper products: smelted products and processed products.

• (5) Machinability

Generally, the machinability of copper alloys is poor, and the addition of lead, sulfur, tellurium and other elements can improve the machinability of copper alloys. According to the machinability, deformed copper alloys can be divided into 3 categories:

1. Free-cutting alloys with machinability above 70%, including free-cutting copper containing lead, sulfur or tellurium, free-cutting brass, various lead brasses, and bronze and zinc cupronickel with a lead content of about 2%;
2. Medium machinability alloys with 30%～60% machinability, including brass with 60%～85% copper, bronze and zinc cupronickel with 1% lead;
3. Difficult-cutting alloys with machinability below 20%, including low-zinc brass, zinc-nickel alloy, tin bronze, copper-nickel alloy and beryllium bronze, etc. (Generally, the machinability of free-cutting brass is 100% for comparison).

• (6)Stress relaxation resistance

Pure copper has poor resistance to stress relaxation. Adding soluble elements that can increase the softening temperature of copper or the atomic size of copper can increase the resistance to stress relaxation of copper. Beryllium bronze, cupronickel and zinc cupronickel 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 ability, the maximum use temperature of copper alloys is about 200°C. Brass with low resistance to stress relaxation can only be used to make parts slightly higher than room temperature. Beryllium bronze and ternary copper-nickel alloys with tin, silicon, aluminum or zinc are resistant even at the highest temperature commonly used in devices. The stress relaxation capacity is still quite high.