Copper alloy refers to an alloy formed by adding one or several other elements to pure copper. The classification of copper alloys is quite easy to understand. There are many colors of copper alloys, and non copper copper copper alloys have different colors. Copper alloys mainly have colors such as purple, yellow, and blue.

1、 Classification

Classification of copper alloys: by color

1. Brass: Refers to alloys based on copper and zinc, which can be further divided into simple brass and complex brass. Complex brass is also named nickel brass, silicon brass, etc. with the third component;

2. Bronze: refers to copper based alloys other than copper nickel and copper zinc alloys, mainly including tin bronze, aluminum bronze, and special bronze (also known as high copper alloys);

3. White copper: refers to copper nickel alloy;

4. Purple copper: refers to pure copper, with main varieties including oxygen free copper, purple copper, phosphorus deoxidized copper, and silver copper.

Classification of copper alloys: by alloy series

1. Non alloy copper: Non alloy copper includes high-purity copper, tough copper, deoxygenated copper, oxygen free copper, etc. Traditionally, people refer to non alloy copper as purple copper or pure copper, also known as red copper.

2. Other copper alloys belong to alloy copper. China and Russia classify alloy copper into brass, bronze, and white copper, and then classify them into smaller alloy systems within the larger category.

Classification of copper alloys: by function

1. Copper alloys for conductive and thermal conductivity mainly include unalloyed copper and microalloyed copper.

2. Copper alloys for structural use: almost all copper alloys are included.

3. Corrosion resistant copper alloys: mainly tin brass, aluminum brass, various non white copper, aluminum bronze, titanium blue, etc.

4. Wear resistant copper alloys: mainly complex brass, aluminum bronze, etc. containing elements such as lead, tin, aluminum, manganese, etc.

5. Easy cutting copper alloys: copper lead, copper tellurium, copper antimony and other alloys.

6. Elastic copper alloys: mainly include antimony bronze, aluminum bronze, beryllium bronze, titanium bronze, etc.

7. Damping copper alloy: high manganese copper alloy, etc.

8. Art copper alloys: pure copper, brass, tin bronze, aluminum bronze, white copper, etc.Classification of copper alloys: classified by material formation method

1. Casting copper alloy: Casting, can also be used for deformation processing.

2. Deformable copper alloy: Deformable copper alloy can be used for casting.

3. Cast copper alloys and deformed copper alloys can be further subdivided into cast copper, brass, bronze, and white copper.

2、 The role of alloying elements

The entry of trace elements into copper is inevitable. Due to the different characteristics of the elements, they can be insoluble in copper, insoluble in trace amounts, soluble in large amounts, and infinitely miscible. The solubility decreases sharply with temperature, and there is a complex phase transition in the solid phase. Therefore, the impact on the properties of copper varies greatly.

3、 Alloying elements

The influence on the conductivity of copper alloys

1. Hydrogen

Hydrogen does not form hydrides with copper, and its solubility in liquid and solid copper increases with temperature, especially in liquid copper where it has a high solubility. When copper solidifies, hydrogen forms pores in the copper, leading to the brittleness of copper products. In solid copper, hydrogen exists in a proton state, and its electrons fill the S-layer orbitals of copper atoms, forming a proton type solid solution. Although pure hydrogen has little effect on the performance of copper, it is harmful to copper and copper alloys. Oxygen containing copper will produce cracks when annealed in hydrogen. Various elements have varying effects on the solubility of hydrogen in copper. Among them, elements such as Ni and Mn increase solubility, while elements such as P and Si decrease solubility. This can be achieved by reducing melting time, adjusting composition, controlling the hydrogen content in the furnace charge, and covering the surface of the melt with charcoal to reduce the hydrogen content in copper.

2. Oxygen

Oxygen is inevitable in the production process of copper, and its impact is also very important. In copper, except for a very small amount of solid solution, it exists in the form of Cu2O. The oxide of copper is insoluble in copper, forming a Cu+Cu2O eutectic structure distributed at grain boundaries. The eutectic reaction is: L oxygen content 0.39%---- α With an oxygen content of 0.01%+Cu2O, the oxygen content in hypoeutectic copper is directly proportional to the eutectic content, and can be accurately measured by comparing it with standard images under a microscope.

The influence of oxygen on the properties of copper and alloys is complex, and trace amounts of oxygen have little effect on the conductivity and mechanical properties of copper. Industrial copper has a high conductivity because oxygen, as a cleaning agent, can remove many harmful impurities from copper and enter the slag in the form of oxides. Especially, it can remove elements such as arsenic, antimony, bismuth, etc. Copper containing a small amount of oxygen can have a conductivity of 100% to 103% IACS, High purity copper, such as 6N copper, has a relatively low resistance value under deep cooling conditions.

The oxygen content in copper used in electronic vacuum components should be strictly controlled. The reason is that electronic vacuum devices need to be encapsulated in hydrogen gas, and the presence of hydrogen in copper can lead to hydrogen disease, causing device damage in high vacuum environments.

When melting copper and copper alloys, deoxidation should generally be carried out, with deoxidizers such as phosphorus, boron, magnesium, etc. added in the form of intermediate alloys. Phosphorus is the most effective deoxidizer, but the residual amount of phosphorus should be strictly controlled because it can strongly reduce the conductivity of copper and alloys.

3. Antimony, bismuth, sulfur, tellurium, selenium

These elements have extremely low solid solubility in copper and are basically insoluble in copper at room temperature. They exist in the form of metal compounds, distributed at grain boundaries, and have little effect on the conductivity and thermal conductivity of copper. However, they seriously deteriorate the plastic processing performance of copper and alloys, and their content should be strictly controlled. National standards stipulate that they should not exceed 0.005%; Due to the excellent cutting performance of copper containing these elements, it has also been applied in the engineering and technical field. For example, chromium copper can be used as a contact for vacuum switch circuit breakers to prevent adhesion of switch contacts during circuit breaking. The bismuth content in bismuth copper can reach up to 0.5% to 1.0%; Copper tellurium alloy containing 0.15% to 0.5% tellurium can be used as high conductivity, easy to cut oxygen free copper, and can be processed into precision electronic components. As a special purpose copper alloy, these elements can be added, but its processing technology is special, and methods such as sleeve extrusion, cold extrusion, casting, and powder metallurgy can be used.

4. Arsenic and boron

Arsenic has a high solid solubility in copper, with a content of up to 6.8% to 7.0% in solid solutions. Arsenic strongly reduces its electrical conductivity and thermal conductivity in copper and is generally added as a modifier, especially valuable for brass condenser alloys. In the past century, the use of condenser pipes in thermal power plants and ships has shown that brass containing 0.1% to 0.15% arsenic can prevent dezincification corrosion of brass, The fatal problem of early leakage in brass condenser tubes has been solved, so various material standards require the addition of arsenic. Experience has shown that HSn70-1 condenser tubes without arsenic often experience leakage accidents within the first 2-3 years of use. After adding arsenic, the service life can be increased to 15-20 years, which is known as a significant technological advancement in copper alloy research. The reason why arsenic can prevent dezincification corrosion of brass is that many studies have shown that arsenic can reduce the electrode potential of copper, thereby reducing the tendency for electrochemical corrosion. Due to the pollution of arsenic oxide in the environment and its harmful effects on human health, factories that melt alloys should have specialized environmental protection and protective measures; Arsenic should be added as an intermediate alloy, and the arsenic content in the arsenic copper intermediate alloy can reach 15% to 30%.

Boron has a low solid solubility in copper and is generally used as a deoxidizer. The residual boron can refine the grain size, and the modification effect found is very significant. Adding 0.01% to 0.04% boron to arsenic containing brass alloys simultaneously has a better feature of preventing zinc removal corrosion of brass. Boron oxide is an excellent covering agent for copper alloy melting and has been widely used. Boron is also commonly added to copper welding materials to prevent oxidation of the welding metal.

5. Phosphorus

As the temperature decreases, the solid solution of phosphorus in copper rapidly decreases, reaching 0.6% at 300 ℃ and 0.4% at 200 ℃. The phosphorus dissolved in copper significantly reduces its conductivity, and the conductivity of the soft band containing P0.014% is 94% IACS. The conductivity with P0.14% is only 45.2%. Phosphorus is the most effective and cost-effective deoxidizer. In trace amounts, it can improve the fluidity of the melt, improve the weldability, corrosion resistance, and softening temperature of copper and alloys. Therefore, phosphorus is a valuable additive element for copper and alloys, containing P0.015% to 0.04% phosphorus copper alloy. It is widely used in the production of building water pipes, refrigeration and air conditioning heat pipes, and ship seawater pipes; Low phosphorus copper alloy plates and strips are widely used in the electronics and chemical industry, and low precision copper alloys are also widely used in copper strips for integrated circuit lead frames; Phosphorus copper alloy with eutectic composition is an excellent welding material. High copper alloy has superplasticity at 580-620 ℃ and can be hot extruded into 3-5mm welding wire. It is an important material for welding copper and copper alloys, steel, and copper parts.

6. Lead

Lead is insoluble in copper and has a low solubility in copper alloys, forming a fusible eutectic structure with copper. Copper with lead content ranging from 0% to 38% in liquid form is immiscible with copper liquid, forming a monocrystalline structure during solidification; In solid state, lead is distributed in a elemental state in copper, and can be distributed within grains and at grain boundaries. In copper alloys containing lead, lead at grain boundaries can be transferred into the grains during phase transformation or recrystallization. Lead has no significant effect on the conductivity and thermal conductivity of copper and alloys, but it can improve their machinability. Lead particles are also solid, which is the desired soft phase for bearing materials. Therefore, lead containing copper and alloys are valuable easy to cut materials and bearing materials, and are more popular in the market due to their low cost. Lead containing brass is widely used, with smaller lead particles and more uniform distribution, resulting in better performance. Lead containing copper and alloys can be used as cast or processed under pressure. Lead brass is single-phase at high temperatures (above 500 ℃) β， Excellent thermal processing performance, able to withstand large thermal deformation, and at room temperature, it is a phase and a+ β During cold deformation, the deformation resistance is high and the plasticity is poor. Excessive processing rate can cause cracks in the alloy material.

With the development of science and technology, the lead content of conventional lead brass has increased from 0.8% to 2.5% to over 5%. New types of lead containing copper, brass, bronze, and white copper are constantly being developed. It should be pointed out that lead containing copper alloys have strong adaptability to raw materials and can be directly produced using recycled copper, which is very important for copper processing enterprises.

6. Lead

Lead is insoluble in copper and has a low solubility in copper alloys, forming a fusible eutectic structure with copper. Copper with lead content ranging from 0% to 38% in liquid form is immiscible with copper liquid, forming a monocrystalline structure during solidification; In solid state, lead is distributed in a elemental state in copper, and can be distributed within grains and at grain boundaries. In copper alloys containing lead, lead at grain boundaries can be transferred into the grains during phase transformation or recrystallization. Lead has no significant effect on the conductivity and thermal conductivity of copper and alloys, but it can improve their machinability. Lead particles are also solid, which is the desired soft phase for bearing materials. Therefore, lead containing copper and alloys are valuable easy to cut materials and bearing materials, and are more popular in the market due to their low cost. Lead containing brass is widely used, with smaller lead particles and more uniform distribution, resulting in better performance. Lead containing copper and alloys can be used as cast or processed under pressure. Lead brass is single-phase at high temperatures (above 500 ℃) β， Excellent thermal processing performance, able to withstand large thermal deformation, and at room temperature, it is a phase and a+ β During cold deformation, the deformation resistance is high and the plasticity is poor. Excessive processing rate can cause cracks in the alloy material.

With the development of science and technology, the lead content of conventional lead brass has increased from 0.8% to 2.5% to over 5%. New types of lead containing copper, brass, bronze, and white copper are constantly being developed. It should be pointed out that lead containing copper alloys have strong adaptability to raw materials and can be directly produced using recycled copper, which is very important for copper processing enterprises.

8. Zinc, tin, aluminum, nickel

The common feature of these four elements is their high solid solubility in copper, which is 39.9%, 15.8%, and 9.4%, respectively. Nickel is infinitely miscible and forms a continuous solid solution with copper, with a wide single-phase region. They can significantly improve the mechanical and corrosion resistance properties of copper, but both reduce its conductivity and thermal conductivity. Compared with other metal materials, nickel still belongs to excellent conductivity and thermal conductivity materials. They form precious alloys with copper, which can be divided into brass, bronze, and white copper alloys, building the foundation of a large alloy system, These alloys have excellent comprehensive properties. For example, brass has high strength, wear resistance, corrosion resistance, high thermal conductivity, and low cost; Bronze has high strength, wear resistance, and corrosion resistance; White copper has excellent resistance to harsh water quality and seawater corrosion, all of which cannot be replaced by other metal materials.

9. Rare earth elements

Rare earth elements are generally almost insoluble in copper, but a small amount of rare earth metals, whether added alone or in a mixed form, are beneficial to the mechanical properties of copper, and have little effect on its conductivity. These elements can form high melting point compounds with impurities such as lead and bismuth in copper, forming small spherical particles uniformly distributed within the grains, refining the grains and improving the high-temperature plasticity of steel. Adding 0.008% mixed rare earth elements to copper can significantly improve its process performance; When less than 0.1% Y is added, the mechanical and process properties of copper are improved; The mechanical properties, conductivity, and anti softening temperature of copper alloys containing 0.01%~0.15% La are superior to Cu-0.15Ag alloys, and have been applied in industry.

10. Refractory metals and other metals

Tungsten, molybdenum, niobium, uranium, plutonium and other elements are almost insoluble in copper, while titanium, zirconium, chromium, cobalt and other elements are slightly soluble in copper. However, they all refine copper grains to varying degrees, increase their recrystallization temperature, neutralize the harmful effects of some fusible impurities, and are beneficial for improving high-temperature plasticity.

Copper alloys containing small amounts of zirconium (Cl5000, C15100, C18100), cobalt (C17110, C17500), and chromium (C18400, C18200, C18500) have been applied in industry and have become excellent electrical materials.

Article source: Internet

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