Copper
Brass is pure industrial copper. Due to its reddish-pink color and the fact that its surface turns purple after the formation of an oxide film, it is generally called red brass or copper.
It is a copper alloy that contains a certain amount of oxygen, also known as oxy-copper, and can sometimes be considered a copper alloy.
Red copper has excellent electrical and thermal conductivity and is extremely malleable. It is easy to be processed by hot or cold pressure, and is widely used in the manufacture of products that require good electrical conductivity, such as wires, cables, electric brushes and special EDM copper for electric spark.
Copper has the second highest electrical conductivity and thermal conductivity after silver and is widely used in the production of conductive and heat-conducting materials.
Copper has good resistance to corrosion in the atmosphere, seawater, certain non-oxidizing acids (hydrochloric acid, dilute sulfuric acid), alkalis, saline solutions and a variety of organic acids (acetic acid, citric acid), and is used in industry chemical .
In addition, copper has good weldability and can be made into various semi-finished products and finished products through cold or hot plasticity processing.
In the 1970s, copper production exceeded the total production of other types of copper alloys.
Classification of Nature
Copper is named for its red-purple color. It is not necessarily pure copper, and sometimes a small amount of deoxidizing element or other elements are added to improve the material and performance, so it is also classified as a copper alloy.
Copper materials can be divided into four categories based on their composition: ordinary copper (T1, T2, T3), oxygen-free copper (TU1, TU2 and high-purity vacuum oxygen-free copper), deoxidized copper (TUP , TUMn) and special copper with a small amount of added alloying elements (arsenic copper, tellurium copper, silver copper).
Copper has the second highest electrical conductivity and thermal conductivity after silver and is widely used in the production of conductive and heat-conducting materials.
Copper has good corrosion resistance in the atmosphere, seawater, certain non-oxidizing acids (hydrochloric acid, dilute sulfuric acid), alkalis, saline solutions and a variety of organic acids (acetic acid, citric acid).
Common copper alloys are classified into three categories: brass, bronze, and white copper.
Copper Performance
Property classification:
Copper is a relatively pure type of copper and can generally be regarded as pure copper with good electrical conductivity and ductility, but lower strength and hardness. Purple copper has excellent thermal conductivity, ductility and corrosion resistance.
Trace impurities in purple copper have a serious impact on the electrical conductivity and thermal conductivity of copper.
Titanium, phosphorus, iron, silicon and other elements can significantly reduce electrical conductivity, while cadmium, zinc and other elements have little effect.
Sulfur, selenium, tellurium and other elements have little solid solubility in copper and can form brittle compounds with copper, which has little effect on electrical conductivity, but can reduce processing plasticity.
Purple copper has good resistance to corrosion in the atmosphere, seawater, certain non-oxidizing acids (hydrochloric acid, dilute sulfuric acid), alkalis, saline solutions and a variety of organic acids (acetic acid, citric acid) and is used in industry chemical.
In addition, purple copper has good weldability and can be made into various semi-finished products and finished products through cold or hot plasticity processing.
In the 1970s, production of purple copper exceeded the total production of other types of copper alloys.
Physical properties:
Trace impurities in purple copper have a serious impact on the electrical conductivity and thermal conductivity of copper.
Titanium, phosphorus, iron, silicon and other elements can significantly reduce electrical conductivity, while cadmium, zinc and other elements have little effect.
Oxygen, sulfur, selenium, tellurium and other elements have little solid solubility in copper and can form brittle compounds with copper, which has little effect on electrical conductivity, but can reduce processing plasticity.
When common purple copper is heated in a reducing atmosphere containing hydrogen or carbon monoxide, the hydrogen or carbon monoxide readily reacts with copper oxide (Cu 2 O) at the grain boundary to produce high-pressure water vapor or gas carbon dioxide, which can cause copper to rupture.
This phenomenon is commonly known as copper “hydrogen disease.”
Oxygen is harmful to the solderability of copper. Bismuth or lead form low-melting eutectics with copper, causing copper to become brittle when hot; while brittle bismuth forms a film-like distribution at the grain boundary, causing cold brittleness of copper.
Phosphorus can significantly reduce the electrical conductivity of copper, but it can improve the fluidity of copper liquid and welding properties. Adequate amounts of lead, tellurium, sulfur and other elements can improve machinability.
The tensile strength of room temperature annealed purple copper plates is 22-25 kgf/mm 2 elongation is 45-50% and Brinell hardness (HB) is 35-45.
The thermal conductivity coefficient of pure copper is 386.4 W/(m·K).
Forms
Copper is widely used in more applications than pure iron. 50% of the copper is electrolytically purified to pure copper for use in the electrical industry.
The copper used here must be very pure, with a copper content greater than 99.95%, and a very small amount of impurities, mainly phosphorus, arsenic, aluminum and others, which can significantly reduce the electrical conductivity of copper.
It is mainly used to manufacture electrical equipment such as generators, buses, cables, switches, transformers, as well as heat transfer equipment such as pipeline heat exchangers, solar heating devices, flat plate collectors and other heat-conducting materials.
The oxygen in copper (easily mixed with a small amount of oxygen during copper refining) has a large impact on electrical conductivity.
Copper used in the electrical industry must generally be oxygen-free copper. Additionally, impurities such as lead, antimony and bismuth will prevent copper crystallization from bonding together, causing hot brittleness and affecting the processing of pure copper.
This high-purity copper is generally refined by electrolysis: impure copper (i.e. raw copper) is used as the anode and pure copper is used as the cathode, with copper sulfate solution as the electrolyte.
When the current passes, the impure copper on the anode gradually melts and the pure copper precipitates on the cathode. Copper refined in this way can have a purity of up to 99.99%.
Purple copper is also used in the production of short-circuit rings for motors, induction heaters, high-power electronic components, wiring terminals, and other components.
Purple copper is also used in furniture and decorations such as doors, windows and handrails.
Brass
Brass is an alloy composed of copper and zinc. If it is composed of just copper and zinc, it is called common brass.
If it is composed of more than two elements, it is called special brass, such as copper alloys composed of lead, tin, manganese, nickel, lead, iron and silicon.
Brass has strong wear resistance. Special brass, also known as special alloy brass, has high strength, great hardness, strong resistance to chemical corrosion and excellent mechanical properties for cutting processing.
Seamless copper tubes made of brass have soft texture and strong wear resistance, and can be used in heat exchangers, condensers, low-temperature pipelines, submarine transportation pipes, and in the manufacture of sheets, bars, rods, tubes and castings, etc.
The copper content in brass ranges from 62% to 68% and has strong plasticity, making it suitable for manufacturing pressure-resistant equipment.
Brass can be classified into two categories: common brass and special brass, based on the type of alloying elements present in it. The brass used for pressure processing is called deformation brass.
1. Common Brass
(1) Room temperature microstructure of common brass
Ordinary brass is a binary alloy of copper and zinc, and its zinc content varies greatly, resulting in a significant difference in its microstructure at room temperature.
According to the Cu-Zn binary phase diagram (Figure 6), the microstructure of brass at room temperature can be divided into three types: brass with zinc content below 35%, which consists of a single-phase α solid solution at temperature environment and is called α-brass; brass with zinc content ranging from 36% to 46%, which consists of a two-phase (α+β) microstructure at room temperature and is called (α+β) brass (two-phase brass); brass with zinc content greater than 46% to 50%, which consists only of β-phase microstructure at room temperature and is called β-brass.
(2) Pressure processing properties
Single-phase α brass (from H96 to H65) has good ductility and can withstand cold and hot working. However, single-phase α brass is prone to medium-temperature brittleness during hot working such as forging, and the specific temperature range varies with the zinc content, generally between 200℃ and 700℃.
Therefore, the temperature during hot work must be above 700°C. The main reason for the medium-temperature brittleness in the α-phase region of the Cu-Zn alloy system is that there are two ordered compounds, Cu3Zn and Cu9Zn, in the α-phase region of the alloy, which undergo ordered transformation during medium temperature. -heating to a low temperature, causing the alloy to become brittle.
Furthermore, harmful impurities such as lead and bismuth exist in small quantities in the alloy and form low-melting point eutectic films distributed at grain boundaries, causing intergranular fracture during hot working. Practice has shown that adding traces of cerium can effectively eliminate brittleness at medium temperatures.
Two-phase brass (from H63 to H59) consists of α and β phase solid solution based on the electronic compound CuZn. The β phase has high ductility at high temperatures, while the β' phase (ordered solid solution) at low temperatures is hard and brittle. Therefore, brass (α+β) must be hot forged.
β brass with zinc content greater than 46% to 50% is hard and brittle and cannot be processed under pressure.
(3) Mechanical properties
Due to the difference in zinc content, the mechanical properties of brass vary. Figure 7 shows the curve of the mechanical properties of brass varying with the zinc content. For α brass, as the zinc content increases, both σb and δ increase continuously. For brass (α+β), the room temperature resistance increases continuously until the zinc content increases to about 45%.
If the zinc content increases further, the brittle R phase (a solid solution based on the compound Cu5Zn8) appears in the microstructure of the alloy and the strength decreases drastically. The room temperature plasticity of brass (α+β) decreases with increasing zinc content. Therefore, copper-zinc alloys with a zinc content of more than 45% are of no practical value.
2. Special Brass
In order to improve the corrosion resistance, strength, hardness and machinability of brass, a small amount of tin, aluminum, manganese, iron, silicon, nickel, lead and other elements (generally 1% to 2%, some up to 3% to 4%, and extremely rare up to 5% to 6%) are added to the copper-zinc alloy to form a ternary, quaternary or even quinary alloy, which is called complex brass or special brass.
(1) Zinc equivalent coefficient
The microstructure of complex brass can be calculated based on the “zinc equivalent coefficient” of the elements added to the brass. Because adding a small amount of other alloying elements to copper-zinc alloys generally just shifts the α/(α+β) phase region in the Cu-Zn phase diagram to the left or right.
Therefore, the microstructure of special brass is generally equivalent to the microstructure of ordinary brass with increasing or decreasing zinc content.
For example, the microstructure of adding 1% silicon to the Cu-Zn alloy is equivalent to the microstructure of the alloy with 10% more zinc in the Cu-Zn alloy.
Therefore, the “zinc equivalent” of silicon is 10. Silicon has the highest “zinc equivalent coefficient”, which significantly shifts the α/(α+β) phase boundary in the Cu-Zn system toward the side of copper, greatly reducing the α phase region. The “zinc equivalent coefficient” of nickel is a negative value, which expands the α phase region.
(2) Properties of special brass
The α and β phases in special brass are multi-element complex solid solutions, which have a greater strengthening effect than simple Cu-Zn solid solutions in ordinary brass.
Although the zinc equivalent is the same, the properties of multi-element solid solutions and simple binary solid solutions are different. Therefore, a small amount of multi-element reinforcement is one way to improve the properties of the alloy.
(3) The microstructure and deformation properties of various commonly used special deformation brasses.
Lead Brass: Lead is not actually soluble in brass, but exists as free particles distributed at grain boundaries. There are two types of lead brass based on its microstructure: α and (α+β). Due to the harmful effect of lead, α-leaded brass has low hot plasticity and can only undergo cold deformation or hot extrusion. Lead brass (α+β) has better plasticity at high temperatures and can be forged.
Tin brass: Adding tin to brass can significantly improve the heat resistance of the alloy, especially its ability to resist corrosion in seawater, therefore tin brass is also called “naval brass”. Tin can dissolve in the copper-based solid solution, providing strengthening of the solid solution. However, as the tin content increases, the brittle r phase (CuZnSn compound) may appear in the alloy, which does not lead to plastic deformation of the alloy.
Therefore, the tin content in tin-plated brass is generally in the range of 0.5% to 1.5%. Commonly used tin brasses include HSn70-1, HSn62-1 and HSn60-1. The first is an α alloy with high plasticity and can undergo cold and hot pressure processing. The last two alloys have a two-phase microstructure (α + β), and a small amount of the r phase is often present, with low plasticity at room temperature, and can only undergo deformation in the hot state.
Manganese brass: Manganese has a relatively high solubility in brass in the solid state. Adding 1% to 4% manganese to brass can significantly improve the alloy's strength and corrosion resistance without reducing its plasticity. Manganese brass has a microstructure (α+β). Commonly used manganese brasses include HMn58-2, which has good deformation properties under cold and hot conditions.
Iron brass: In iron brass, iron precipitates as rich iron phase particles, which serve as nucleation sites and refine grains, and can also prevent the growth of recrystallized grains, thereby improving the mechanical and processing properties of the iron. turns on. The iron content in ferrous brass is usually less than 1.5%, and its microstructure is (α + β), with high strength and toughness, good plasticity at high temperatures and deformability in the cold state. The commonly used grade is Hfe59-1-1.
Nickel Brass: Nickel and copper can form a continuous solid solution, significantly expanding the α phase region. Adding nickel to brass can significantly improve the alloy's corrosion resistance in the atmosphere and seawater. Nickel can also increase the recrystallization temperature of brass and promote the formation of finer grains.
HNi65-5 nickel brass has a single-phase α structure and has good plasticity at room temperature. It can also be deformed in the hot state, but the lead impurity content must be strictly controlled, otherwise the hot workability of the alloy will be severely degraded.
3. Main chemical composition of brass
| Note | Chemical composition | ||||||
| QB | GB/JIS/UNS | Ass | Pb | Zn | Faith | Sn | Total impurities |
| C2501 | JIS C3501 | 60.0-64.0 | 0.7-1.7 | REM | <=0.2 | Fe+Sn<=0.4 | – |
| Chapter 3601 | JIS C3601 | 59.0-63.0 | 1.8-3.7 | REM | <=0.3 | Fe+Sn<=0.5 | – |
| Chapter 3602 | JIS C3602 | 59.0-63.0 | 1.8-3.7 | REM | <=0.5 | Fe+Sn<=1.2 | – |
| Chapter 3603 | JIS C3603 | 57.0-61.0 | 1.8-3.7 | REM | <=0.35 | Fe+Sn<=0.6 | – |
| Chapter 3604 | JIS C3604 | 57.0-61.0 | 1.8-3.7 | REM | <=0.5 | Fe+Sn<=1.2 | – |
| Chapter 3605 | JIS C3605 | 56.0-60.0 | 1.8-3.7 | REM | <=0.5 | Fe+Sn<=1.2 | – |
| Chapter 3771 | JIS C3771 | 57.0-61.0 | 1.8-3.7 | REM | Fe+Sn<=1.0 | – | |
| 360 | ASTM C36000 | 60.0-63.0 | 2.5-3.7 | REM | <=0.35 | Remained | |
| H62 | H62/JIS C2800 | 60.5-63.5 | <=0.08 | REM | <=0.15 | – | <=0.5 |
| H65 | H65/JIS C2700 | 63.5-68.0 | <=0.03 | REM | <=0.1 | – | <=0.3 |
| H68 | H68/JIS C2600 | 67.0-70.0 | <=0.03 | REM | <=0.1 | – | <=0.3 |
| H63 | H63 | 62.0-65.0 | <=0.08 | REM | <=0.15 | – | <=0.5 |
| H90 | H90 | 88.0-91.0 | <=0.03 | REM | <=0.1 | – | <=0.2 |
| H96 | H96 | 95.0-97.0 | <=0.03 | REM | <=0.1 | – | <=0.2 |
| H62F | H62F | 60.0-63.0 | 0.5-1.2 | REM | <=0.2 | – | <=0.75 |
| HPb59-1 | HPb59-1 | 57.0-60.0 | 0.8-1.9 | REM | <=0.5 | – | <=1.0 |
| HPb58-2 | – | 57.0-59.0 | 1.5-2.5 | REM | <=0.5 | – | <=1.0 |
4. Mechanical Properties of Brass
| Note | Processing bar properties | Processing Yarn Performance | |||||
| state | Tensile strength | Elongation rate (%) | Toughness | state | Tensile strength | Elongation rate (%) | |
| HPb63-3 | S(H) | >=490 | >=3 | – | S(H) | 390-610 | >=3 |
| >=450 | >=8 | – | 390-600 | >=3 | |||
| >=410 | >=10 | – | 390-590 | >=4 | |||
| S(H) | >=390 | >=10 | – | A2 (1/2h) | 570-735 | – | |
| >=360 | >=14 | – | |||||
| H62F | S(H) | >=380 | >=12 | – | A2 (1/2h) | 390-590 | >=8 |
| 390-590 | >=10 | ||||||
| >=340 | >=15 | – | 370-570 | >=12 | |||
| 350-560 | >=15 | ||||||
| HPb59-1 HPb58-2 HPb58-3 |
S(1/2h) | >=450 | >=8 | – | A2 (1/2h) | 390-590 | – |
| >=420 | >=10 | – | 360-570 | – | |||
| >=390 | >=12 | – | S(H) | 490-720 | – | ||
| >=370 | >=16 | – | 400-640 | – | |||
| H62 H63 |
A2 (1/2h) | >=370 | >=15 | – | M(0) | >=335 | >=18 |
| >=315 | >=26 | ||||||
| >=300 | >=36 | ||||||
| A2 (1/2h) | >=410 | – | |||||
| >=355 | >=7 | ||||||
| >=335 | >=15 | ||||||
| >=335 | >=20 | – | Y1(3/4H) | 540-785 | |||
| 390-685 | |||||||
| 350-550 | |||||||
| S(H) | 685-980 | ||||||
| 540-835 | |||||||
| 500-700 | |||||||
| H65 | S(H) | >=390 | – | – | M(0) | >=325 | >=18 |
| >=295 | >=28 | ||||||
| >=275 | >=38 | ||||||
| A2 (1/2h) | >=400 | – | |||||
| >=375 | >=7 | ||||||
| >=350 | >=15 | ||||||
| M(0) | >=295 | >=40 | – | Y1(3/4H) | 490-735 | – | |
| 490-785 | – | ||||||
| 470-670 | – | ||||||
| S(H) | 635-885 | – | |||||
| 490-785 | – | ||||||
| 470-670 | – | ||||||
| H68 | A2 (1/2h) | >=370 | >=15 | – | M(0) | >=355 | >=18 |
| >=395 | >=30 | ||||||
| >=275 | >=42 | ||||||
| >=315 | >=25 | – | A2 (1/2h) | >=390 | – | ||
| >=345 | >=10 | ||||||
| 310-510 | – | ||||||
| >=295 | >=30 | – | Y1(3/4H) | 490-735 | – | ||
| 345-635 | – | ||||||
| 310-510 | – | ||||||
| M(0) | >=295 | >=45 | – | S(H) | 685-930 | – | |
| 540-835 | – | ||||||
| 490-685 | – | ||||||
| C3501 | – | – | – | – | 0 | >=295 | >=20 |
| 1/2H | 345-440 | >=10 | |||||
| H | >=420 | – | |||||
| Chapter 3601 | 0 | >=295 | >=25 | – | 0 | >=315 | >=20 |
| 1/2H | >=345 | – | >=HV95 | H | >=345 | – | |
| H | >=450 | – | >=HV130 | H | >=345 | – | |
| Chapter 3602 | F | >=315 | – | >=HV75 | F | >=365 | – |
| Chapter 3603 | 0 | >=315 | >=20 | – | 0 | >=315 | >=20 |
| 1/2H | >=365 | – | >=HV100 | 1/2H | >=365 | – | |
| H | >=450 | – | >=HV130 | H | >=450 | – | |
| Chapter 3604 | F | >=335 | – | >=HV80 | F | >=420 | – |
| Chapter 3605 | |||||||
| Chapter 3771 | F | >=315 | >=15 | – | F | >=365 | >=10 |
| 360 | A2 (1/2h) | >=450 | >=8 | – | A2 (1/2h) | 420-600 | – |
| >=410 | >=12 | – | 375-590 | – | |||
| >=390 | >=18 | – | 360-550 | – | |||
| H | >=490 | – | – | H | 520-735 | – | |
| >=450 | – | – | 440-710 | – | |||
| >=420 | – | – | 410-610 | – | |||
| H90 H96 |
S(H) | >-=265 | >=4 | – | S(H) | 470-800 | – |
| 400-720 | – | ||||||
| >=245 | >=6 | – | 380-620 | – | |||
| M(0) | >=205 | >=35 | – | M(0) | >=315 | >=32 | |
| >=250 | >=38 | ||||||
| >=230 | >=45 | ||||||
Classification of copper and copper products
1.1 Classification based on the form of existence in nature
Native copper: copper content is above 99%, but reserves are extremely scarce;
Copper oxide ore: also rare;
Copper sulfide ore: copper content is extremely low, generally around 2-3%.
two . Classification based on production process
Copper concentrate: ore with the highest copper content selected before smelting.
Blister copper: product obtained after smelting copper concentrate, with a copper content between 95-98%.
Pure copper: copper with a content greater than 99% obtained after pyrometallurgical refining or electrolysis. Pyrometallurgical refining can produce pure copper with a purity of 99-99.9%, while electrolysis can make the purity of copper reach 99.95-99.99%.
3 . Classification based on main alloy elements
Brass: copper-zinc alloy;
Bronze: copper-tin alloy, etc. (except zinc-nickel alloy, alloys with other elements added are called bronze);
Cupronickel: copper-cobalt-nickel alloy.
4 . Classification based on product shape: copper tubes, copper bars, copper wires, copper sheets, copper strips, copper bars, copper sheets, etc.
