Oxygen content of oxygen-free copper rods and control of extrusion tailing defects
1. Oxygen-free copper 1. Overview No. 1 and No. 2 oxygen-free copper plates TU1 and TU2 are copper containing very little oxygen. They have the characteristics of high purity, high electrical conductivity and high thermal conductivity, and have no "hydrogen disease" or very little "hydrogen disease". sick". Oxygen-free copper with extremely low phosphorus content has good sealing properties with glass, good processing performance, weldability, corrosion resistance and cold resistance. Oxygen-free copper is mainly used for parts of electric vacuum instruments, and is widely used in busbars, conductive strips, waveguides, coaxial cables, vacuum seals, vacuum tubes, transistor components, etc. 2. Physical and chemical composition of oxygen-free copper TU1, copper content: 99.97, total impurity ≤ 0.03 TU2: Copper content: 99.97 or more, total impurity ≤ 0.05 ① Oxygen-free copper thermal performance melting point: 1082.5~1083℃. Thermal conductivity: 391W/(m·℃) at 20℃. Specific heat capacity: 385J/(kg·℃) at 20℃. ②Quality characteristics of TU1 oxygen-free copper: At 20℃, the shrinkage rate of oxygen-free copper during solidification is 4.92%, and the density is 8.94g/cm³. ③Electrical properties of oxygen-free copper: The conductivity is g=101.4% IACS at 20℃, annealed at 700℃, and measured after 30 minutes. The resistivity is ρ=0.0171μΩ·m at 20℃. ④ Magnetic properties of oxygen-free copper: Oxygen-free copper is diamagnetic, with a mass magnetic susceptibility of -0.085×10-6m3/kg at room temperature. ⑤ Chemical properties of oxygen-free copper Anti-oxidation properties: The oxidation rate of copper increases significantly at high temperatures, and it oxidizes slowly in the atmosphere and at room temperature. Corrosion resistance: Oxygen-free copper is resistant to corrosion in the atmosphere, pure fresh water, and seawater with low flow rates. It also has good resistance to non-oxidizing acids, but it is resistant to oxidizing acids, wet ammonia, wet halogens, sulfides, and Solutions containing ammonium ions have very low corrosion resistance. ⒊ Oxygen-free copper thermal processing specifications Oxygen-free copper thermal processing and heat treatment specifications are: annealing temperature: 375 ~ 650℃. Hot processing temperature: 750 ~ 875℃. ⒋ Mechanical properties of oxygen-free copper ⑴ Mechanics specified in oxygen-free copper technical standards Performance According to the regulations of GU/T14953-1994, the wire rod repeated bending performance test standard is: a wire rod with a diameter of not less than 0.3mm is subjected to repeated bending tests after hydrogen annealing, and the number of bending tests is not less than 10 times. ⑵ Mechanical properties of oxygen-free copper at room temperature and various temperatures ① Hardness: Room temperature hardness: HBS35~45 (M state), HBS85~95 (Y state). ②Tensile properties: The tensile properties of TU2 copper plate at room temperature are: σb=350~390MPa, δ=3%~5% (Y state) σb=220~235MPa, δ=45%~55% (M state) ③Impact properties: Impact toughness: αKU=1560～1760kJ/㎡④Torsion and shear properties: Shear strength: τ=210MPa (Y state): τ=150MPa (M state) ⑤Fatigue properties: The high cycle fatigue strength limit is : TU2 plate, cold deformation 50%. The number of cycles is 108 cycles, σD=119MPa. ⑥Elastic properties: Elastic modulus: E=117.2GPa. Shear modulus: G=44.1GP At present, with the development of high-tech fields such as vacuum electronic devices, electrical, and microelectronics in my country, the market demand for oxygen-free copper is increasing, and the requirements for materials are also increasing. The higher. How to produce high-quality oxygen-free copper (TU0, TU1) to meet market demand is a major issue faced by copper processing companies. 2. Main factors affecting the quality of oxygen-free copper 1. Main factors ① Quality of raw materials ② Influence of oxygen ③ The production of sealed oxygen-free copper in smelting equipment follows the process principle of "concentrated materials, sealing, and refining" and strictly controls the quality of raw and auxiliary materials. , Strict process systems and operating procedures, and adopting effective detection methods to improve the quality of oxygen-free copper are currently feasible and effective control methods in the production of oxygen-free copper. 2. Factors affecting the oxygen content of oxygen-free copper and its control. Oxygen content is a very important indicator of oxygen-free copper materials. There are many factors that affect the oxygen content of oxygen-free copper. The following are the main influencing factors and control measures: (1) ) There is indeed a large difference in the copper oxygen content of the raw material cathode (minimum 3ppm, maximum 90ppm). The production of high-quality (TU0, LC1011, TU1) oxygen-free copper has high requirements on raw material cathode copper, and high-purity cathode copper should generally be used. (2) Melt covering and protection 2.1 Melt covering charcoal is the best covering agent for oxygen-free copper smelting. Charcoal covers the surface of the melt, which not only prevents oxygen and air absorption, but also has a good deoxidation effect. The deoxidation reaction of charcoal is: Cu2O +C=2Cu+ COCu2O + CO =2Cu + CO2 The quality of charcoal has a great influence on the deoxidation effect of the melt. Various types of charcoal were analyzed and the results are shown in Table 2. White carbon burned from oak and other wood should be used as the deoxidizer for oxygen-free copper. In addition, charcoal should be calcined (500℃~800℃) and should not be left for a long time. It should be used immediately after baking. 2.2 Gas protection: Inert gas (nitrogen) is introduced into the smelting furnace and holding furnace (nitrogen should also be introduced into the head of the holding furnace) to isolate the air, prevent oxygen and air inhalation, and reduce charcoal loss; During the transfer process of molten copper, the melt flow rate in the launder is fast and fluctuates greatly. The liquid surface is easily exposed when using a solid covering agent. Inert gas (nitrogen) or coal gas should be used for protection. (3) Sealing At present, there is a certain gap between domestic oxygen-free copper smelting equipment and foreign countries. The key lies in sealing technology. For example, more than 99% of C10200 oxygen-free copper ingots produced by imported oxygen-free copper furnace groups (sealed well, using only non-calcined ordinary charcoal) have an oxygen content below 10 ppm, while those produced by other domestic equipment (using calcined charcoal) The oxygen content of C10200 oxygen-free copper ingot is less than 90% below 10ppm. This shows how critical the equipment sealing condition is to controlling the oxygen content of oxygen-free copper ingots. (4) Refining and deoxidation Generally speaking, even for high-purity cathode copper, the basic oxygen content is mostly above 10ppm. To meet the needs of some customers for oxygen-free copper with an oxygen content below 5ppm, refining and deoxidation must be performed. In addition to using high-quality calcined charcoal for deoxidation treatment, an appropriate amount of Cu-P alloy is added for deoxidation to ensure the oxygen content requirements of oxygen-free copper. In addition, in order to further achieve the deoxidation effect, an oxygen-free copper melt deoxygenation technology has been developed in recent years-introducing carbon monoxide and nitrogen into the furnace through breathable bricks, using the reducing effect of carbon monoxide to achieve the elimination of oxygen in the copper liquid. removal purpose. (5) Ingot heating In order to meet the user's requirements for the oxygen content of oxygen-free copper, the surface of the oxygen-free copper ingot needs to be prevented from oxygen infiltration during subsequent processing. During the heating process of oxygen-free copper ingots, the heating temperature and heating time need to be controlled. 2.2 Gas protection: Inert gas (nitrogen) is introduced into the smelting furnace and holding furnace (nitrogen should also be introduced into the head of the holding furnace) to isolate the air, prevent oxygen and air inhalation, and reduce charcoal loss; During the transfer process of molten copper, the melt flow rate in the launder is fast and fluctuates greatly. The liquid surface is easily exposed when using a solid covering agent. Inert gas (nitrogen) or coal gas should be used for protection. (3) Sealing At present, there is a certain gap between domestic oxygen-free copper smelting equipment and foreign countries. The key lies in sealing technology. For example, more than 99% of C10200 oxygen-free copper ingots produced by imported oxygen-free copper furnace groups (sealed well, using only non-calcined ordinary charcoal) have an oxygen content below 10 ppm, while those produced by other domestic equipment (using calcined charcoal) The oxygen content of C10200 oxygen-free copper ingot is less than 90% below 10ppm. This shows how critical the equipment sealing condition is to controlling the oxygen content of oxygen-free copper ingots. (4) Refining and deoxidation Generally speaking, even for high-purity cathode copper, the basic oxygen content is mostly above 10ppm. To meet the needs of some customers for oxygen-free copper with an oxygen content below 5ppm, refining and deoxidation must be performed. In addition to using high-quality calcined charcoal for deoxidation treatment, an appropriate amount of Cu-P alloy is added for deoxidation to ensure the oxygen content requirements of oxygen-free copper. In addition, in order to further achieve the deoxidation effect, an oxygen-free copper melt deoxygenation technology has been developed in recent years-introducing carbon monoxide and nitrogen into the furnace through breathable bricks, using the reducing effect of carbon monoxide to achieve the elimination of oxygen in the copper liquid. removal purpose. (5) Ingot heating In order to meet the user's requirements for the oxygen content of oxygen-free copper, the surface of the oxygen-free copper ingot needs to be prevented from oxygen infiltration during subsequent processing. During the heating process of oxygen-free copper ingots, the heating temperature and heating time need to be controlled.
