Nano Tungsten Copper Electrode Research

The granularity and uniformity of tungsten and copper powder has an effect on tungsten copper electrode sintering, and the decreasing granularity will improve the comprehensive properties of materials, such as the density, the hardness, the electric and thermal conductivity. Theoretically, powder metallurgy (PM) uses metal powder (or metallic oxide powder) as raw materials, after compacting and sintering, the granularity of powder is coarser. Compared with PM, nano tungsten copper has higher surface energy, which atoms move by higher interfacial energy, shrink the small pores in sintering process and in case of the diffusion of pores. Therefore, nano tungsten copper research is beneficial for the densification at lower temperature.

Although the process of nano tungsten copper is similar to the traditional PM, which can be divided into preparation, compacting and sintering, due to the characteristic of nano particle, there are some differences between them. Overall, the most widely used process of nano tungsten copper main are Sol-Gel method, Metal Alloying (MA), Mechano-Thermo-chemical Process, spray drying and so on.

Metal Alloying (MA), uses high energy ball milling for tungsten copper mixed powder grinding, achieves the nano powder (the granularity is about 20nm-30nm). Then compacts the blank by the nano powder and sintering in hydrogen atmosphere at 1000℃, nano tungsten copper with high related density can be achieved.

The so-called sol - gel (Sol-Gel) is the use of compounds with high chemical composition as the precursor in the liquid phase under these uniformly mixed materials, hydrolysis and condensation reactions to form a stable transparent sol in solution sol particles by aging between slow polymerization to form a three-dimensional network structure of the gel, the gel network between full solvent loses fluidity to form a gel. After drying, sintering and solidifying, sol can be produced with molecular or nano substructure. At the academic front, some researchers succeed in preparing MoW and CuW high-performance powder. However, this kind of process has some shortcomings, such as the content of water vapor and impurities is difficult to control in the process of hydrogen reduction, which these problems will influence the later sintering process.

Mechano-Thermo-Chemical process, uses ammonium paratungstate and copper nitrate as raw materials to prepare a mixed solution, and then spray drying the mixed solution to obtain a metal powder mixture through a rotary atomizer and the subsequent drying process of the precursor, the precursor of combustion, the formation of tungsten copper W-Cu composite oxide powder, then milled oxide powder and two-step hydrogen reduction, thereby preparing nano-tungsten-copper composite powder.

Tungsten Copper Electrode — Chemical Co-precipitation

Tungsten copper is a kind of psudoalloy, which is composed of W with body-centered cubic structure (bcc) and Cu with face-centered cubic (fcc) structure and they are immiscible or not forming intermetallic compound. It not only has high hardness, high strength, low coefficient of thermal expansion and excellent wear resistance and corrosion resistance of W, but also has excellent electrical conductivity, thermal conductivity and plasticity, which can be widely used in some electrical contact materials or electrode materials. Generally, the basic process is: mixing → forming → infiltration, sintering → post-processing.

But tungsten copper electrode fabricated by conventional process, regardless of liquid-phase sintering or solid-phase sintering, the relative density of tungsten copper products produced will lower than 98% because of the wetting angle and the insoluble W in liquid Cu. Although the heating process and re-pressing or re-sintering can remarkably improve this situation, the cost is increasing and the overall efficiency is decreasing. Furthermore, in the sintering process will happen inevitably growth of tungsten grains, which would make it difficult to meet the performance of the market demands tungsten copper electrode material now.

In order to improve the sintering density of tungsten copper electrode and other tungsten copper composite materials, relevant researchers use activated sintering by adding additives. However, the activator can significantly improve the density of tungsten-copper alloy, it will also have some effects on the electrical and thermal conductivity, which is not suitable for the occasions has high demands on electrical and thermal conductivity. So chemical co-precipitation of copper tungsten nano composite powder prepared by reduction combined with hydrogen, by pressing and sintering process to obtain a high-performance compact tungsten copper alloy electrodes become a new hotspot.

The definition of chemical co-precipitation is that in solution mixing materials with different chemical compositions were prepared precursor precipitate mixture added a suitable precipitating agent, then the precipitate is dried or calcined, to thereby obtain the corresponding powder particles. It has two advantages, one is a nano-powder materials can be obtained directly by chemical composition homogeneous solution in a variety of chemical reactions, and the other is easy to prepare small particle size and distribution of nano-powder materials.

The experiment use ammonium tungstate, copper sulfate pentahydrate and concentrated nitric acid as raw materials. The specific operation of concentrated nitric acid in a copper nitrate solution was added with stirring, and then the mixed solution was added a solution of ammonium tungstate, a magnetic stirrer in the chemical co-precipitation reaction; After 1h the reaction solution was removed and the precipitate was placed in a muffle furnace firing 2h, to obtain tungsten copper composite oxide powder; after reduction by hydrogen obtained tungsten copper composite powder; then the tungsten-copper composite powder is extruded to form a green with a certain density and strength, ultra-fine grain was finally sintered tungsten copper alloy products.

Tungsten copper powder is polygon and the granularity is between 30nm – 50nm. Cu into a network-like structure of the W particles are bonded together in an approximation polygon and evenly distributed. This is because the raw material for preparing tungsten-copper composite powders of tungsten and copper salt solution, the distribution of the particles in the solution itself more evenly in the strong magnetic stirring effect, will make the precursor powder to retain the basic solution mixed state molecular level. And calcination and hydrogen reduction process in low temperature effectively inhibited the growth W grains. In addition, the initial structure of the powder is the oxides of tungsten and copper, their mutual isolation is not conductive to the growth of tungsten oxide particles, but is beneficial for evenly dispersed tungsten copper composite powder. From the fracture morphology, W grain evenly distributed in the Cu phase, forming larger dimples around, Cu phase has continuous web-like distribution along with the W grains. From the structure, with the increase in the sintering temperature, tissue distribution is more uniform, the porosity is also decreased. From the properties of alloy, Tungsten-copper composite compacts during sintering two-phase distribution, effective at power-conduction electron-average running speed increases, the conductivity also increases; complete copper network-like structure decrease the contact area of coarse W grains, which is difficult to form necking and beneficial for thermal conduction.

Tungsten Copper Contact Tip

Tungsten copper contact tip is a kind of welding consumables and it is generally located in the end of welding torch, which play a role in delivering welding wire. According to the hole shape, it can be divided into round, square, ellipse, triangle and so on. Common used materials for contact tips include pure copper, brass, beryllium copper, chromium zirconium copper, beryllium cobalt copper, etc.

In the resistance welding process, not only requires the contact tip has good electrical conductivity, but also required at high temperatures still has high strength, wear resistance and corrosion resistance to electrical properties. In practical, the contact tips use pure copper and beryllium copper, which have poor wear resistance and during welding process will easily spatter adhesion. It cause clogging of the tip or the wire and the contact tip bonding, which make the contact tip failure. Furthermore, replacing contact tip frequently will affect the welding performance and decrease the overall efficiency. Compared with pure copper, chromium zirconium copper and beryllium cobalt copper has higher hardness and better wear resistance at room temperature. But it has fewer sources, relatively complex process and higher cost.

Tungsten copper has both advantages of W and Cu, which not only has higher hardness, but also has excellent wear resistance, galvanic corrosion and higher softening temperature. Whether as the electrical resistance welding electrode with special requirements for the stress or as the contact tip used in arc welding, tungsten copper material has a great advantage, which is an important role of the electrical processing and welding occasion. Tungsten copper contact tip is sintered by tungsten and copper composite powder and the tungsten skeleton uniformly distributed in the copper matrix. When the temperature exceeds the melting point of copper, tungsten skeleton liquid copper can stick as a huddle and constitute a good conductor of heat passage, so tungsten skeleton area overheating does not occur in the process.

Theoretically, the room temperature strength of metal depends on two basic factors: one is binding force of metal atom, the other one is the resistance to dislocation motion. Common by increasing resistance to dislocation movement to improve the strength and work hardening methods are split out strengthened. However, these methods the effect of increasing temperature decreases until it disappears, and some rely precipitates precipitation hardening copper alloy, when raised to a certain temperature, the precipitate into the matrix meet again, so that a sharp decline in the strength of the material. By comparison, tungsten copper material does not has phase change, recrystallization phenomena at high temperature and the physical and chemical properties are stable.

The experiments show that 70W-Cu has higher hardness and better electrical conductivity than beryllium cobalt copper, and its softening temperature is twice more than beryllium cobalt copper, so as for flash butt welding electrode wear or require a higher arc welding contact tip applies quite well. In addition, in the process of vertical welding, when the thickness of the weldment 22-28mm, wire diameter φ2.4mm, 2.8mm the pore size of the contact tip, tungsten copper contact tip and chromium copper contact tip after welding has a great difference in wear. Tungsten copper welding contact tip at 20m, the circular aperture can remain unchanged, ensure the continue welding; The chromium copper welding contact tip about 2m, circular conductive mouth to occur due to poor abrasion resistance unilateral eccentric, expand the aperture and are unable to continue welding. Overall, tungsten copper contact tip has higher hardness, better thermosetting, wear resistance, excellent arc ablation resistance, anti-adhesion, which is a kind of contact tip materials with a broad application prospect.

Elkonite Tungsten Copper

Elkonite tungsten copper is a kind of alloy that has high density, high hardness, high strength and good corrosion resistance. Tungsten copper is suitable for embedded block, contacts, galvanic corrosion electrode and so on.

Grade	Class	Content(%wt)	Hardness	Conductivity(%IACS)
Elkonite10055	1W3	55W, 45Cu	70HRB	49
Elkonite10068	3W3	68W, 32Cu	83HRB	42
Elkonite10070	5W3	70W, 30Cu	88HRB	42
Elkonite10075	10W3	75W, 25Cu	92HRB	38
Elkonite10080	30W3	80W, 20Cu	98HRB	34
Elkonite10250	TC5	50WC, 50Cu	94HRB	45
Elkonite10256	TC10	56WC, 44Cu	100HRB	42
Elkonite10270	TC20	70WC, 30Cu	37HRC	30

1W3, 3W3 generally used as embedded block for flash welding and butt welding, which has higher requirement of conductivity and malleability. These materials can also be used for welding (as a spherical electrode) for low-conductivity ferrous metals such as stainless steel;

5W3, TC5 is suitable for light projection welding and other low-pressure welding;

10W3 is suitable for most of flash welding, light electric upsetting, electric forging die, and seam welding inserts;

TC10 used for mass production of solder bumps where the weld pressure is set relatively high. Non-ferrous metal processing and low carbon steel electric forging rough This material is commonly used as a stamped surface, cross-welding large diameter wire and bar;

TC20 is extremely hard and hard to be machining, which has been widely used in electric upsetting and electroforming.

Tungsten Copper Heat Sink Application

Tungsten copper heat sink has high hardness, excellent conductivity, low CTE and good hermeticity, which plays an important role in mechanical support, radiating passage, signal transmission, chip protection and so on. So tungsten copper heat sink has many applications, such as plate heat exchanger, electronic radiator, integrated circuit, microwave component and CPU the occasions with high requirement to hermeticity and radiating.

Used for plate heat exchanger

Tungsten copper heat sink for plate heat exchanger forms high-voltage circulating structure by vacuum welding of contact points. And the circulation structure makes the hot and cold fluid in the plate heat exchanger produce strong turbulence and achieves high heat transfer effect.

Used for electronic radiator 

Tungsten copper heat sink used for electronic radiator is also called as tungsten copper radiator, which can take heat away and cool down without external power supply.

Used for microwave component 

Working in the microwave band (frequency 300 ~ 300000 MHz) of the device, known as microwave components. Microwave devices can be divided into microwave oscillators (microwave sources), power amplifiers, mixers, detectors, microwave antennas, microwave transmission lines according to their functions. Tungsten copper heat sink used for microwave component plays an important role in mechanical support and heat conductivity, which is one of the important parts of microwave system.

Used for CPU

CPU will produce a lot of heat when it is working, if not timely disseminate the heat out, it is easy to lead to poor computer operation, or even burn the CPU. Tungsten copper heat sink used for CPU can cool it down and keep working stability.

Used for integrated circuit 

Tungsten copper heat sink for integrated circuit connects the required transistors, resistors, capacitors and inductors and other components and wiring, made in a small or a few small pieces of semiconductor chips or dielectric substrate, and then packaged in a tube, the circuit has become the desired micro-structure; it combines all components as a whole in structure and promote the development towards miniaturization, low power consumption.

Tungsten Copper Heat Sink Proportion

Tungsten copper heat sink has both advantages of W and Cu, such as high hardness, high strength, excellent conductivity and wear or corrosion resistance. According to different content of W and Cu, tungsten copper heat sink proportion or grades mainly include W70, W75, W80 and W85, and different proportion has some differences in properties.

W70

Tungsten copper W70 heat sink belongs to refractory metal and has excellent mechanical strength and anti-arc ablation capability so that it can be used for vacuum contacts, transformer switch and some electrical forging industries.

W75 

With the perfect arrangement of W and Cu, tungsten copper W75 heat sink provides a best way to solve the deformation in some small precision machining. And with the development of large scale integrated circuit and high power electronics, tungsten copper composite material has been widely used in electronics and heat sink materials.

W80

Tungsten copper W80 heat sink is composed of 80% W and 20% Cu so that high hardness and melting point characteristics of tungsten are more obvious. Common materials could not work at such high temperature (even more than 3000℃), tungsten copper takes advantage of Cu evaporating taking away heat so that the whole temperature will decrease.

W85 

Tungsten copper W85 materials play an important role in military field. It can not only be used as rocket, missile and other components with high temperature and high-speed airflow ablation, such as gas vane, spray tube, throat insert, nose cone, but also can be used as EFP linear of armor piercing, nozzle of range-extended, orbit material for electromagnetic gun.

Tungsten Copper Powder Injection Molding Research

Based on conventional molding process and combines plastic molding industry technology, PIM (Powder Injection Molding) has excellent applicability in some tungsten copper products with small size and complex shape or structure. So we study from mixing, injection, degreasing, sintering and several key process of tungsten copper powder injection molding, and analyze and summarize the advantages of the process and the defects.

The first is the selection of the binder and the preparation of mixture. Binders can reduce caking of the powder, which has good flowability, and plays the role of maintaining the shape of the body until degreasing sintering. Thus the choice of the binder is injection molded in a key ring, it should meet the deformation and cracking does not occur before the product sintering defect, and easy to be removed. Now more use thermoplastic or some polymers as binders, such as paraffin, stearic acid, HDPE, EVA and so on. In the process of mixing, paraffin and stearic acid are liquid phase, which does not destroy the nature of the binder. In addition, wherein the order of addition of powder and a binder is the final state of the blank has a certain influence. The next is granulating, and select particles about 2-3mm for injection molding.

Many parameters of injection molding should be perfectly controlled, such as the temperature, the pressure, the speed and so on. Theoretically, in the process of injection molding, the temperature and pressure are the largest influencing factors of molding properties. In order to press tungsten copper powder mixture into the mold cavity, the temperature inside the injection machine must be high enough so that moderate viscosity mixing, the two-phase does not separate. For injection pressure (to overcome the flow mixing cavity flow resistance, provide filling speed and compaction of the melt) and speed in the experiment demonstrated that there is an optimal match range, pressure and speed should not be too large or too small. From the figure above, we can also find the optimum temperature range for injection, injection pressure and speed. Since the injection process to fill the cavity is more complex, many parameters must be well controlled, once appear unreasonable control can cause a variety of defects. We introduce some common defects and the corresponding solutions: 1. Under-injection, it refers to the injection process feed can not fill the mold cavity, the corresponding solution is three-pronged approach from the injection temperature, feeding quantity and viscosity of the feed itself causes analyzed; 2. The pores, it is the most common type of defect, the corresponding method is to pay attention to whether the injection and mixing of air entrainment and make adjustments, check the injection speed, the injection pressure, etc; 3. Unstable quality, it should be considered that whether the powder is uniform and the segregation with the binder.

Tungsten Copper Power Properties Test

Tungsten copper powder properties itself will directly affect the final performance of tungsten copper products so that the test of tungsten copper powder raw material becomes vital. At present, laser particle size analysis, transmission electron microscope, differential scanning calorimetry are the main test methods, next we will introduce and analyze them by theory and working principle.

Laser particle size analyzer judges the size of particles by distribution (ie, scattering spectra) by the diffraction space or scattered light particles. The method combines Fraunhofer with Mie scattering theory, when a bunch of laser irradiation wavelength λ in the small spherical particles of a certain size, the beam encounters a barrier, diffraction and scattering phenomenon will occur. Generally, when the particle size is less than 10λ, the main phenomenon is scattering, while the particle size is greater than or equal to 10λ, the main phenomenon is diffraction.

The most widely used laser particle size analyzer currently usually uses 500-700nm wavelength laser as a light source, which test particles size above 5μm is relatively accurate. For particle size of less than 5μm by Mie theory is mathematically corrected, which means that for the sub-micron or nano-scale particles have a certain measure of error. In addition, theoretical model of laser particle size analysis is based on spherical particles and mono-disperse condition, and thus for the particle shape and particle size distribution will have a greater impact on the final results of particle size analysis. The more irregular shape of particle, the wider particle size distribution, the final error will be greater. For tungsten-copper composite powders, the water as a dispersant and add ethanol for grinding, after 30 minutes of ultrasonic cleaning in distilled water dispersion of particle size analysis.

Next, we introduce transmission electron microscope (TEM), which is a kind of high-powered high-resolution microscope. Compared with common optical microscope, it uses electromagnetic field as lens and was widely used in super-fine grain, aggregates and some nano-scale material testing. Furthermore, since the electron beam penetration is weak, so the specimens for electron microscopy of ultrathin sections shall be made about a thickness of about 50nm, which require ultra-microtome machining. For tungsten-copper powder, the thickness is more than 100nm, if the sample is required and the powder milled sample was dissolved in ethanol, in an ultrasonic cleaning after the suspension of the dispersed drops in the electron microscope with a copper medium carbon film, powder morphology was observed after drying.

Finally, thermal analysis, which refers to a change in endothermic or exothermic reactions that take place through the heating and cooling process and the quality of the material, the components was analyzed and identified substance. It includes that differential scanning calorimetry (DSC), which measuring thermal transitions within the material and relevant to the relationship between temperature and heat flow. The shape of the melting peak on DSC curve reflects the particle size distribution; the information can be drawn melting enthalpy crystallinity. Themogravimentric analysis (TGA) records that temperature changes and the time the sample quality, measurable by TGA analysis of injection molding material at different temperatures of weight loss situation, and in order to determine the heating rate of heat degreasing.

Tungsten Copper Used in Vacuum Switch

Tungsten copper composite material has high hardness, high melting point, high strength and sweating property so that it can be widely used in high temperature, military fields, aeronautics and astronautics, vacuum switch, electronic packaging, EDM electrode and so on. Here we highlight tungsten-copper composite material in vacuum switch electrical aspects. Theoretically, vacuum switch is a kind of pressure in the vacuum system for the protection of the automatic controller, small size, excellent performance, stability, ease of maintenance and long service life. It can be widely used in various industrial automation environments, such as water utilities, petrochemicals, railways, military, pipelines, ships and so on.

When the vacuum pressure is greater than the set point, the controller will automatically cut off the circuit, signals, to ensure the normal operation of the system. When the pressure in the system is higher or lower than the safe pressure, pressure sensor immediate action within the controller, the controller makes contact on or off, the device stops working; When the pressure within the system to a safe pressure range of the device, the pressure sensor inside the controller reset immediately, the contacts within the controller turned on or off, the device is working properly. In order to adapt some high-voltage as well as vacuum switch electrical demand, related researchers developed special vacuum switch of tungsten copper. It can be perfectly adapt to flammable, explosive, high temperature and low temperature, moisture, corrosive environments, and gradually dominate the high-voltage (6-35V) grid and electrification equipment.

Tungsten copper composite materials require extremely low gas containing impurities (such as oxygen O2, N2 gas, etc.), it requires the use of a low gas content of raw materials and special process (high temperature sintering, vacuum infiltration, vacuum degassing, etc.) prepared. n these vacuum tungsten copper contact materials, in addition to conventional grades, the proportion of copper tungsten contact material has also developed a number of high-low tungsten copper tungsten copper, tungsten W is usually its content> 85%, such as W-10Cu, W-15Cu, etc., when asked tungsten copper material used in the case of low value when the closure, which can also add some other low melting point metal (such as antimony Sb, bismuth Bi, tellurium Te).

In contrast, there is a high copper content (60% -90%) of tungsten copper alloy, wherein W-70Cu Tungsten copper alloy products have been tested and Vickers hardness reaches1100MPa and 80% -85% IACS of high conductivity, and at 600 ℃ can still maintain a high hardness and conductivity, stable performance. Therefore, It also gradually replace some of the precious metal contacts (such as silver contacts, etc.), which significantly reducing the cost of the contact material. Overall, with the application of tungsten-copper composite materials more widely, for its new tungsten copper alloy materials research is also developing, such as tungsten copper with gradient structure, nano-crystalline tungsten copper, tungsten copper deformation processing, tungsten copper used in vacuum, tungsten copper with high or low content of tungsten, which replace the conventional materials in EDM, micro electronics, high temperature, military fields gradually. However, there are some problems of tungsten copper products in china, includes less high-end products, low utilization, the research and production are disjoint.

Tungsten Copper Contact for Air Breaker

Tungsten copper contact for air breaker is an important component in low-voltage distribution network and electric drive system, which can prevent it from overloading based on contacting and breaking circuit.When the general overload circuit, the overload current can not make the electromagnetic release of action, but can make the heat element to produce a certain amount of heat, to promote the bimetal heating up bending, push the lever to hook and lock release, the tungsten copper The main contact breaking, cut off the power. When the line short-circuit or serious overload current, short-circuit current exceeds the instantaneous trip setting current value, the electromagnetic release to produce a large enough suction, the armature to attract and hit the lever, so that the hook around the shaft seat rotation and lock release, The buckle under the action of the reaction force spring will be three main contact breaking, cut off the power.

According to different applications, tungsten copper air breaker can be divided into main contact, auxiliary contact and alarm contact.

Main contact: In the event of a serious overload or short circuit fault, the coil in series with the main circuit will produce a strong electromagnetic attraction to the armature to attract the top of the open hook, so that the main contact disconnected. When the power supply voltage returns to normal, it must be re-closed to work, which achieves the pressure loss protection;

2. Auxiliary contact: It is the circuit breaker main circuit point, a mechanical linkage on the mechanical contact, mainly for the circuit breaker sub-state display, connected to the circuit breaker control circuit through the circuit breaker of the separation, the implementation of related electrical control or interlock;

3. Alarm contact: Mainly used for the circuit breaker load overload short circuit or other fault free tripping.

Tungsten Copper Contact for SF6 Breaker

Tungsten copper contact for high-voltage breaker is kind of oil-free switchgear that uses SF6 gas as arc quenching medium and insulating medium. It has better performance in arc extinguish and insulation than oil circuit breaker and has high requirement of application, management, operation of SF6. So it main used for the voltage level of 110kv.

It composed of porcelain column structure: It also known as blocks, a plurality of identical unit interrupters and pillar insulators can be used to form the circuit breakers of different voltage levels. The circuit breaker consists of three independent single-phase and one hydraulic, electrical control cabinet. Each phase consists of two pillars of porcelain sets of four interrupters (fracture) in series. In each pillar porcelain top of the unit is equipped with two unit interrupter, 120 ° angle V-shaped arrangement, the two parallel capacitors are arranged horizontally.

Tank structure: Using the advantages of box-type multi-oil circuit breaker, the circuit breaker and the transformer together, compact structure, anti-seismic and anti-fouling ability. It is generally three-phase split-type, single-phase from the base, insulated porcelain casing, current transformers and single-break interrupter with the shell composition. Each phase is equipped with a hydraulic mechanism and a control cabinet which can be operated individually and can be operated in three phases by means of electrical control.

Characteristic

1. As insulating gas, SF6 has many advantages, is colorless, tasteless, non-toxic, non-flammable inert gas and has performance in cooling arc. Especially cooling effect under high arc temperature;

2. The chemical effect of SF6 gas itself is very stable, and has a very high dielectric strength;

3. Blocking effect: give full play to the effect of air blowing arc, interrupter small size, simple structure, breaking current, arc time is short, breaking capacitor or inductor current without re-ignition, over-voltage;

4. Long electrical life: 50kA full capacity of continuous breaking up to 19 times, the cumulative breaking current up to 4200kA, maintenance cycle is long, suitable for frequent operation;

5. Good sealing performance: SF6 gas has lower water content, arc chamber, resistance and pillar into separate air separation, on-site installation without opening, after installation with automatic connection; installation easy maintenance, and to prevent dirt and moisture Into the circuit breaker inside.

Tungsten Copper Contact for Electronic

Tungsten copper contact for electronic has excellent wear and corrosion resistance and mainly used for controlling electron motion in vacuum, air or solid. So it has a wide range of application, such as electronic components, connectors, semiconductor discrete devices, electro-acoustic devices, laser devices, electronic display devices, optoelectronic devices, sensors, power supplies, switches and other electronic chemical materials and parts.

1. Wedge-type Contact: By the use of double-headed bolt sets of spring pressure in the conductive seat on the pairs of contact and wedge-shaped contact block composition, the general wedge-shaped contact block as a moving contact. When the moving contact is contacting with the static contact, the contact surface will be cleaned by the friction. Its high electric stability, self-cleaning effect, increase the number of contacts and wedges may increase the rated current, but also increased the size of the horizontal, so the assembly is difficult;

2. Insert-type Contact: Static contact is composed of multiple trapezoidal fingers. There are two types of flexible conductive sheet and non-flexible conductive sheet. A flexible conductive piece of the socket, a finger on the groove, groove embedded in the insulating sleeve, into the coil spring, in order to ensure that the finger on the conductive rod pressure, the other end of the spring ring support, along the conductive rod (moving contact) around to adjust the touch finger position slightly.

China's electronic components production has accounted for more than 39% of the world. The major products include capacitors, resistors, electro-acoustic devices, magnetic materials, piezoelectric quartz crystal, micro-motor, electronic transformers, printed circuit boards. So tungsten copper contact for electronic also has a lot of the demands. With the expanding scale of China's electronic information industry, the Pearl River Delta, Yangtze River Delta, the Bohai Bay region, part of the central and western regions of the four major electronic information industry base initially formed. These areas of electronic information enterprise concentration, the industry chain is more complete, with considerable size and supporting capacity. However, there are some problems in electronic components industry, such as excess low-end products, and high-end products mainly rely on imports; lack of core technology, low product profits; inadequate investment for technology development.

Tungsten Copper Used for Vacuum High-voltage Switch

Tungsten copper composite materials have widely used in electrical contacts, high voltage switches and breakers, especially in high voltage SF6, air / oil medium, large current circuit breaker. Recent years, with the rapid development of vacuum high-voltage switch, the contact materials have some innovation correspondly. Compared with other contacts, vacuum contact materials have higher requirements. Except the normal properties of switches, due to the surface of contact is particular clean, which will be easier welded in the air. So based on high resistance to weld, it also needs higher welding resistance, higher anti-electric erosion, low cut-off current and low content of gas. And tungsten copper excellent properties can perfectly meet the needs of high-voltage switch contacts.

From compression molding, for tungsten copper sheet contacts, CIP (Cold Isostatic Pressing) has good forming performance, but it has higher equipment investment and lower material utilization. The mechanical molding should be noted that the gap of molding tools and tungsten powder granularity. The smaller gap will cause the difficulties in stripping; the larger gap will make tungsten powder scratch the mold and produce the cracks on the surface of compact. From sintering process, porous tungsten skeleton sintered is the key process of tungsten copper manufacturing. High-temperature sintering is easy to remove impurities and ensure the electrical conductivity and the gas content meet the requirements. In addition, during the sintering process also need to consider the tungsten powder particle size, size distribution and pressing density. Too low temperature will increase the porosity and reduce the density and hardness of products; too high temperature will reduce the content of Cu and the electrical conductivity decrease. Overall, choose pure tungsten powder as raw material, mechanical molding, sintering furnace hydrogen reduction, hydrogen protection copper infiltration process to produce high-pressure vacuum switch tungsten copper material, it has high strength of porous W skeleton, low gas content, Cu has network-like distribution, tungsten copper matrix bonded tightly.

Cu Content Effect on Tungsten Copper Liner

Tungsten copper liner is considered as the heart of ammunition, which not only has high hardness, high strength and low coefficient of thermal expansion of W, but also has good plasticity and excellent thermal and electrical conductivity of Cu. Compared with single metal liner, this kind of composite liner has many advantages, such more reasonable energy conversion and absorption mechanism, fuller utilization of chemical energy, better performance in armor, lower cost, a broader application prospect and so on. With the production technology and process innovation, dense liner gradually is replaced by powder liners.

Since tungsten copper powder liner has high density, good ductility, deep penetration, less plugging and other advantages, it has been play an important role in shaped charge and some military fields. But in the process of tungsten copper liner, with the increasing temperature, Cu loss is always an inevitable problem. Cu loss will reduce the density and strength of materials. Related researchers based on pressure pressing, sintering temperature and time factors on the rate of variation of copper analyzed, and summed up the impact of copper and relative density on jet liner properties for the preparation of tungsten-copper powder liner offers theoretical basis. The experiments show that he rate of copper sintered samples with the pressing pressure increases with increasing sintering time and sintering temperature decreases, Cu loss is opposite. This is due to:

1. The pressure increases effectively narrows the distance of W grains, which reduces the Cu loss from the inside and slows internal material Cu particles outward evaporation rate;

2. The increasing pressure enlarges the contact area of Cu surface that the original Cu particles have a larger free energy in the melting process is easier and the adjacent Cu particles fuse to form larger particles. And it reduces the volatile rate of fine particles at high temperature that the content of Cu remained stable. Therefore, the content of Cu impact on the jet penetration is significant less than the relative density, but plays an important role in the stability of the jet. The smaller the rate of copper loss, the liner jet penetration is more stable.

Tungsten Powder Granularity Effect on Armor Capability of Tungsten Copper Liner

In recent years, tungsten copper is one of the most outstanding materials for the liner. Liner is the key part of shaped charge, which quality directly determines the penetration and armor capability of warhead blast. Compared with conventional liner, the powder liner has many advantages, such as high density, excellent thermal conductivity, good elongation, flexible composition ratio, better moldability and so on. Penetrating analysis based on fluid dynamics theory, it can be avoided to a large extent from the phenomenon of blocking pestle to form a longer and stable jet. Tungsten powder shape, size and size distribution can have a significant impact on the powder compaction and sintering process and the final product performance, thus affecting the performance liner shaped and penetration depth.

The experiment uses mixed - pressing sintering process, and put the compacting liner blank into high-temperature tube furnace, after 70min gradually warmed to 750℃ and holding 20min. Then use instantaneous electric detonator at the top of the midpoint detonating the static penetration power experiment. From the uniformity of powder liners isometric high radial position analyses, its runout and wall thickness substantially unchanged. The density distribution is analyzed in the axial direction, typically the maximum density at the top of the bottom of the minimum density, a decreasing trend was up and down. Detecting the use of Archimedes powder liners green density can be found in between 45-62μm tungsten powder particle granularity, with the decrease of tungsten powder particle size, density and relative density of the compact tungsten-copper powder liner and sintered density showed a trend of increasing. While maintaining the same quality with sub-fractions, process, particle size and other conditions of 60 ° tungsten powder copper shaped the static penetration test can be found with the decrease of the particle size of tungsten powder, powder liner break a depth showed an increasing trend and a significant improvement in the performance of armor.

Tungsten Copper Plasma Component Technology Breakthrough

Recently, French Atomic Energy Commission (CEA) / Institute of magnetic confinement fusion (IRFM) researchers announced a good news: Institute of Plasma Physics, Chinese Academy of Sciences has made key progress in the development of two types of tungsten copper heat load (HHF) test module towards plasma components (W / Cu-PFC) test. Tungsten copper towards plasma component mainly refers to perforated tube. Tungsten copper perforated tube is one of the parts of vertical divertor target plates, and the divertor has been playing an significant role in magnetic confinement fusion reactor.

The main role of divertor is that the interaction between plasma and materials processing separated in two chambers and separates the resulting doping source and the main plasma. In general, it uses High heat load irradiation for the divertor properties testing, which is an important criteria to evaluate the quality of tungsten copper perforated tube. Tungsten copper not only has high melting point, high strength, low coefficient of thermal expansion, low sputter rate, low retention and excellent wear and corrosion resistance, etc., which is recognized as the most suitable for future nuclear fusion reactor plasma-facing materials. Tungsten copper perforated tube is first to drill on tungsten block, followed by brazing or hot isostatic pressing (HIP) block and other technology tungsten chromium zirconium copper pipe connected. Since it has symmetry in structure, can relief the thermal stress concentration and eliminate the stress point so that it can withstand high thermal loads irradiation.

Tungsten copper perforated tube fabricated by HIP has well combining face and without any obvious cracks, but the wall thickness of the circumferential unevenness in the HIP process of collapse and cracking phenomenon occurs. This time, the Chinese Academy of Sciences has made a major breakthrough in the manufacture of technology in the international community for the first time to achieve mass production of tungsten copper PFC, tungsten plasma interaction to carry out a comprehensive study under the conditions of long-pulse high parameters and provides an excellent platform. According to IREM researchers report relevant results: W / Cu perforated tube (Mono-block) No. 4 block modules withstand 1,200 times 10MW / m2 and 300 20MW / m2 radiation heat load; No. 5 tungsten block withstood 500 10MW / m2 and 500 20MW / m2 radiation heat load beyond the International Thermonuclear Experimental Reactor ITER to 20MW / m2 radiation heat load 300 requirements. In addition, W / Cu plates (Flat type) module FT1 to withstand 102 times 10MW / m2,102 times 15MW / m2 and 302 times 20MW / m2 radiation heat load; Tablet Module FT2 withstood 302 times 10MW / m2,102 times 15MW / m2 and 102 times 20MW / m2 radiation heat load. Irradiation results far beyond the flat module 5 MW / m2 in the ITER design requirements, refresh the W / Cu plate member is known recording HHF tests. This also proves that the advanced nature of the plasma connecting tungsten copper PFC technology to some extent.

Tungsten Copper Contact — Ultrasonic NDT

Tungsten copper contact is also known as tungsten copper electrical contact or tungsten copper contact tip, which is a kind of psudoalloy that consist of W and Cu two kinds metals of immiscible and without the formation of intermetallic compounds. Consequently, it not only has high hardness, high melting point, high strength, low coefficient of thermal expansion and excellent wear resistance and corrosion resistance of W, but also has perfect electrical and thermal conductivity and plasticity of Cu. And it has been played an important role in some high-voltage switch, breaker, and instrument components.

Currently, preparation of tungsten copper contacts is mainly used in PM (powder metallurgy) technology, the corresponding method used for the performance testing, such as the density, the hardness, the strength, the tensile strength and micro-structure, etc., will have some damages on the integrity of tungsten copper products and lead to failure. And these tools to test for products in large quantities can only do a certain proportion of sample, which is difficult to have some representation. If the unqualified tungsten copper contacts undetected used in actual production is likely buried security risk, both for production or personal safety is extremely unfavorable. So the relevant researchers use Non-destructive testing techniques to measure and evaluate the mechanical properties of tungsten copper related products.

Ultrasonic NDT (Non-destructive Testing) is a kind of process that ultrasound can penetrate deep into the use of a metallic material, by entering a cross-sectional another cross-sectional; edge reflection occurs at the interface characteristics of the parts to check for defects. When the ultrasonic beam from the surface of the part by the probe pass to the metal inside encounter defects and Part underside of the reflected wave occurs, respectively, form a pulse waveform on the screen, based on these pulse waveforms to determine the location and size of the defect. Compared with other detecting methods, Ultrasonic NDT has many advantages, such as:

1. Ultrasound has perfect penetration ability, low transmission loss and the probing depth of up to several meters;

2. High sensitivity, it can be found with the diameter of the air-based reflectance 0.1-1mm equivalent reflector;

3. Accurate positioning, to assume the shape and the size are also more accurate;

4. Convenient in operation and it is suitable for the most materials;

5. The entire testing process will not cause environmental pollution, no harm to the human body completely.

Nano Tungsten Copper Composite Material

Nano tungsten copper composite material is also known as ultra-fine tungsten copper composite material, which compared with common grain tungsten copper, has better mechanical and chemical properties, such as high density, high hardness, high strength, excellent wear and corrosion resistance and perfect thermal and electrical conductivity, etc. Its granularity usually between 1nm -100nm and the nano grain has several characteristics is given as follow:

1. Small size effect: When the coherence length or penetration depth dimension and the wavelength of light particles, de Broglie wavelength and other physical characteristics of the superconducting state of a considerable size or less, crystal periodic boundary conditions will be destroyed, the density of atoms near the surface of the particle layer of amorphous nano-particles reduced, resulting in characteristic sound, light, electricity, magnetic, thermal, mechanical and other changes in the new physical properties;

 2. Surface effect: With the decreasing grain size, the ratio of surface atoms and total atoms of nano tungsten copper grains is dramatically increasing and the binding energy of grain is correspond increasing, which changes the properties of nano grains;

 3. Quantum size effect: When copper tungsten particle size down to a certain size, the electron energy levels near the Fermi level from continuous to discrete energy and transformation. During the existence of discrete energy level occupied molecular orbital, at the same time there are also contrary to occupy the lowest molecular orbital, and the spacing between the high and low rail level with the smaller diameter of the nano particles increased;

 4. Macroscopic quantum tunneling effect: Electrons have wave-particle duality and the ability to penetrate the barrier, known as the tunnel effect. Macroscopic quantum tunneling effect will be the basis for future microelectronics, electronics, or it further establishes the limits of miniaturization existing microelectronic device;

 5. Coulomb blockade and quantum tunneling: In nano scale dimensions, the charging and discharging process is not continuous, filled with an electron energy required is called the Coulomb energy blockage. In such a small system of single-electron transport behavior is known as Coulomb blockage effect, if the two quantum dots connected by a junction, a single quantum dot electrons through the energy barrier to another quantum dot is the quantum tunneling.

Nano tungsten copper composite material has better performance in thermal properties, magnetic properties, optical properties, the super-conducting properties, catalytic properties and so on. From the thermal properties, at extremely low temperatures, the thermal resistance of tungsten copper nano particle is almost zero; from magnetic properties, nano grain will enter super-paramagnetic state when it exceeds a certain threshold and shows high coercivity; from optical properties, nano particle quantum size effect is more significant, in the optical performance of the wide-band receiver, the dispersion obtain some special optical properties; and the super-conducting transition temperature of nano tungsten copper grain increases as the decreasing granularity. In addition, from catalysis nature, as the particle size decreases the reactivity significantly increased under appropriate conditions capable of catalyzing the breakage H-H, C-H, C-C, C-O chemical bond and so on.