Super dry information, in-depth analysis of the difference between oxygen-free copper and red copper, brand comparison, chemical performance comparison, thermal performance comparison, casting process
1. Red copper (T1, T2, T3)
Red copper is industrial pure copper. Because it has a rose red color and an oxide film is formed on the surface, it turns purple, so it is generally called red copper. The copper content is 99.5~99.95%. It is copper containing a certain amount of oxygen, so it is also called oxygen-containing copper. Sometimes also seen as copper alloy. The main grades of ordinary copper are T1, T2, and T3, which are used to make conductive materials, high-quality copper alloys, and copper-based alloys.
2. Oxygen-free copper (TU0, TUI, TU2)
That is, pure copper does not contain oxygen or any deoxidizer residue, but in fact it still contains very trace amounts of oxygen and some impurities. According to the oxygen content and impurity content, oxygen-free copper is divided into TU1 and TU2. The purity of TU1 reaches 99.97%, the oxygen content is no more than 0.003%, and the total impurity content is no more than 0.03%; the purity of TU2 reaches 99.95%, the oxygen content is no more than 0.005%, and the total impurity content is no more than 0.05%.
3. Red copper/oxygen-free copper series grades
01. With foil
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02.Plate
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03.Pipe
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04.Bar
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4. Chemical composition comparison
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5. Thermal performance comparison
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6. The difference between red copper and oxygen-free copper
01. Differences in use
(1) Purposes of red copper: T1 and T2 are mainly used for conductive, thermal conductive and corrosion-resistant components, such as wires, cables, conductive screws, shells and various conduits, etc. T2 is mostly used in the aviation industry. T3 is mainly used as a structural material, such as making electrical switches, washers, rivets, nozzles and various conduits, etc. It is also used in some conductive components.
(2) Usage of oxygen-free copper: It is mainly used for parts of electric vacuum instruments, and is widely used in bus bars, conductive strips, waveguides, coaxial cables, vacuum seals, vacuum tubes, transistor components, etc.
Differences in quality characteristics
(1) Quality characteristics of red copper: At 20°C, the density of 99.999% processed pure copper is 8958kg/m3, the density of cast electrolytic refined copper is 8300~8700kg/m3 (the average value can be 8500kg/m3), and there is no gas in the cast state The density of electrolytic refined copper is 8850~8930kg/m3 (the average value can be 8920kg/m3), and the density of C11000 and C12500 is 8890kg/m3.
(2) Quality characteristics of oxygen-free copper: At 20°C, the shrinkage rate of oxygen-free copper during solidification is 4.92%, and the density is 8.94g/cm3.
Magnetic difference
(1) Magnetism of red copper: Red copper is a diamagnetic material with a magnetic susceptibility of -0.085×10-6 at room temperature. Temperature has little effect on its magnetic susceptibility. If ferromagnetic impurities (especially iron) are insoluble in copper, the copper will become ferromagnetic.
(1) Magnetism of oxygen-free copper: Oxygen-free copper is diamagnetic, with a magnetic susceptibility of -0.085×10-6 at room temperature.
7. Process performance
Copper
1. Smelting and casting process performance:
Use reverberatory furnace melting or power frequency cored induction furnace melting; use copper molds or iron molds for casting. During the smelting process, gas sources should be reduced as much as possible, and calcined charcoal should be used as a flux, and phosphorus can also be used as a deoxidizer. The casting process is carried out under nitrogen protection or covering with soot. The recommended casting temperature is 1150-1230°C and the linear shrinkage rate is 2.1%.
2. Molding process performance:
It has excellent cold and hot processing properties and can be processed by various traditional processing techniques, such as drawing, rolling, deep drawing, bending, coining and spinning, etc. During thermal processing, the heating medium atmosphere should be controlled to make it slightly oxidizing. Thermal processing temperature is 800-950℃.
3.Welding process performance:
It is easy to solder and braze, and can also be used for gas shielded welding, flash welding, electron beam welding and gas welding, but it is not suitable for contact point butt welding and submerged arc welding.
4. Cutting and grinding process performance:
The machinability of red copper is 20%.
Oxygen-free copper
1. Smelting and casting process performance:
Oxygen-free copper is mainly smelted using power frequency cored induction furnaces. In order to ensure the quality of oxygen-free copper, "concentrate sealing" must be achieved, that is, the raw material must be electrolytic copper containing w (Cu) > 99.97% and w (Zn) < 0.003%. During smelting, attention must be paid to reducing the source of gas, and Use calcined charcoal to cover, and trace amounts of phosphorus can also be added as a deoxidizer. The ingots are cast using a semi-continuous casting process under nitrogen protection or soot coverage. The casting temperature is 1150-1180℃.
2. Molding process performance:
Oxygen-free copper has excellent cold and hot working properties and can be stretched, rolled, extruded, bent, punched, sheared, spun, upsetting, forged, forged, threaded, knurled, wound, and has great forgeability. The best is 65% of forged brass. Thermal processing temperature is carried out at 800-900℃.
3.Welding process performance:
It is easy to perform fusion welding, soft soldering, brazing, gas shielded tungsten arc welding, and gas shielded metal arc welding. Its oxygen fuel gas welding performance is good. Shielded metal arc welding and most resistance welding methods are not recommended.
4. Cutting and grinding process performance:
The machinability of oxygen-free copper is 20% of that of free-cut brass HPb63-3.
8. Smelting of oxygen-free copper
Strictly distinguish, oxygen-free copper should be divided into ordinary oxygen-free copper and high-purity oxygen-free copper. Ordinary oxygen-free copper can be smelted in a power frequency iron core induction furnace, while high-purity oxygen-free copper should be smelted in a vacuum induction furnace.
When using semi-continuous casting, the refining process of the melt in the melting furnace and holding furnace can be independent of time constraints. Continuous casting is different. The quality of molten copper not only depends on the refining quality of the smelting furnace and holding furnace, but more importantly, it also depends on the stability of the entire system and process.
In order to prevent the melt from being contaminated, oxygen-free copper smelting generally does not use any additives for smelting and refining. The surface of the molten pool is covered with charcoal and the reducing atmosphere formed is a commonly used smelting atmosphere.
Induction electric stove
Induction furnaces for smelting oxygen-free copper should have good sealing properties. Smelting oxygen-free copper should use high-quality cathode copper as raw material. To smelt high-purity oxygen-free copper, high-purity cathode copper should be used as raw material. If the cathode copper is dried and preheated before entering the furnace, moisture or humid air that may be adsorbed on its surface can be removed.
When smelting oxygen-free copper, the thickness of the charcoal layer covering the surface of the molten pool in the furnace should be double that of smelting ordinary pure copper, and the charcoal needs to be updated in time. Although charcoal covering has many advantages, such as heat preservation, air isolation and reduction, it also has certain disadvantages. For example, charcoal easily absorbs moist air and even directly absorbs moisture, thus becoming a channel through which liquid copper may absorb a large amount of hydrogen.
Charcoal or carbon monoxide have a reducing effect on cuprous oxide, but are completely ineffective against hydrogen. Therefore, charcoal should be carefully selected and calcined before being added to the furnace. During the smelting, transfer, heat preservation and entire casting process, complete protection of the melt is a necessary condition for the production of oxygen-free copper.
In many modern oxygen-free copper smelting and casting production lines, not only the smelting, but also the drying and preheating of the charge, the transfer launder, the pouring chamber, etc. are fully protected. Some modern large-scale oxygen-free copper production lines use generator gas as protective gas, while most gas generators use natural gas as raw material.
A method of manufacturing protective gas commonly used abroad is: first burn natural gas with relatively low sulfur content and 94% to 96% methane with theoretical air, and use nickel oxide as the medium to remove hydrogen. The resulting gas is mainly composed of Composed of nitrogen and carbonic acid gas. Then, the carbonic acid gas is turned into carbon monoxide by using hot charcoal to obtain an oxygen-free gas containing 20% to 30% carbon monoxide and the remainder being nitrogen. In addition to generator gas, gases such as nitrogen, carbon monoxide or argon are also used as dielectric materials for oxygen-free copper melt protection or refining.
8. Vacuum melting
Vacuum smelting is the best choice for smelting high-quality oxygen-free copper. Vacuum melting can not only greatly reduce the oxygen content, but also greatly reduce the content of hydrogen and certain other impurity elements.
When smelting in a vacuum medium frequency coreless induction furnace, graphite crucibles and high-purity cathode copper or remelted copper that have been refined twice are often used as raw materials. Packed into the furnace together with the copper cathode, it also includes flake graphite powder for deoxidation. In fact, deoxidation is mainly carried out through the carbon in the graphite crucible material. The amount of carbon consumed can be calculated. For example, 1 kg of copper consumes 100 g of carbon. Experience shows that the higher the oxygen content in the copper liquid at the beginning, the faster the deoxidation reaction proceeds in the early stages of smelting.
The oxygen content of oxygen-free copper obtained through vacuum smelting can be lower than 0.0005%, or even lower than 0.0001% to 0.0003%. In fact, only when copper is smelted and cast under a certain degree of vacuum, it is possible to obtain castings that are completely free of oxygen and other gases. Therefore, the vacuum degree of the vacuum furnace used to produce copper materials for electronic tubes should be above 10-6.
