Q: What is tungsten electrode?
A: Due to the characteristics of tungsten, it is very suitable for TIG welding and other similar electrode materials. Adding rare earth oxides to metal tungsten to stimulate its electronic work function, so that the welding performance of tungsten electrodes can be improved: the arc starting performance of the electrode is better, the stability of the arc column is higher, and the electrode burn rate is smaller.
Tungsten electrode is used for TIG welding. This is a tungsten alloy bar made by mixing 0.3%-5% of rare earth elements such as cerium, thorium, lanthanum, zirconium, yttrium, etc. in the tungsten matrix through powder metallurgy. The diameter is from 0.25 to 6.4mm, and the standard length is from 75 to 600. The most commonly used specifications are diameters of 1.0, 1.6, 2.4 and 3.2. The shape of the electrode tip is an important factor for TIG. When using DCSP, the electrode end needs to be ground into a sharp shape, and its tip angle varies with the application range, electrode diameter, and welding current. Narrow joints require a smaller tip angle. When welding very thin materials, A low current, needle-like smallest electrode is used to stabilize the arc, and a proper ground electrode can ensure easy arc ignition, good arc stability and proper bead width. When welding with AC power supply, there is no need to grind the electrode end, because when the proper welding current is used, the electrode end will form a hemispherical shape. If the welding current is increased, the electrode end will become bulb-shaped and may melt and contaminate the molten gold.
With the development and expansion of applications of inert gas shielded welding with tungsten electrodes, the research on tungsten electrodes has become more and more in-depth. In plasma arc welding, cutting and non-melting argon arc welding, thorium tungsten electrodes were used in the past, but due to the radioactive effect of thorium (the radiation dose is 3.60×105 Curie/kg), it will harm human health and pollute the environment Therefore, a cerium tungsten electrode with a cerium oxide content of 2 to 4% is used instead of a thorium tungsten electrode. In direct current argon arc welding, the cerium tungsten electrode is easy to start the arc, and the electrode burns less, and the welding current density is allowed to be higher than that of thorium tungsten; while in AC argon arc welding, the burn loss of the cerium tungsten electrode is larger than that of the thorium tungsten electrode. , The allowable range of welding current selected for the cerium tungsten electrode is smaller than that of the thorium tungsten electrode.
Thorium tungsten electrodes are easy to operate and work well even under overload currents. There are still many people using this material, and it is regarded as part of high-quality welding. Even so, people are gradually turning their attention to other types of tungsten electrodes, such as cerium tungsten and lanthanum tungsten. Because the thorium oxide in the tungsten thorium electrode produces a small amount of radiation, some welders are reluctant to approach them.

Q: What is Tungsten?
A:Tungsten is a metal element, the element symbol is W, it has high hardness, high melting point, and is not corroded by air at room temperature; its main purpose is to manufacture filaments, high-speed cutting alloy steel, super-hard molds, and also used in optical instruments and chemical instruments. China is the world’s largest tungsten storage country.
The atomic number of tungsten is 74, the relative atomic mass is 183.85, the atomic radius is 137 picometers, and the density is 19.35 grams per cubic centimeter. It belongs to the VIB group of the sixth period (the second longest period) of the periodic table. Tungsten is mainly a hexavalent cation in nature, and its ion radius is 0.68×10-10m. After smelting, tungsten is a silver-white shiny metal with extremely high melting point, high hardness, low vapor pressure, low evaporation rate, and relatively stable chemical properties.
The tungsten-copper alloy (10%-40% copper) and tungsten-silver alloy manufactured by powder metallurgy have the good electrical and thermal conductivity of copper and silver and the wear resistance of tungsten. Therefore, it becomes a very effective contact material for manufacturing working parts such as knife switches, circuit breakers, and spot welding electrodes. The composition is 90%-95% tungsten, 1%-6% nickel, 1%-4% copper high specific gravity alloy, and the alloy with iron instead of copper (-5%), used to make top The rotor of the instrument, the airplane, the counterweight that controls the rudder, the radiation shield and the feed basket of the radioisotope, etc.
Electric vacuum lighting materials: Tungsten is used in electronic tube production, radio electronics and X-ray technology with tungsten wire, tungsten ribbon and various forged components. Tungsten is the best material for white woven filament and spiral filament. The high working temperature (2200-2500℃) guarantees high luminous efficiency, while the small evaporation speed guarantees the long life of the filament. Tungsten wire is used to manufacture direct heating cathodes and grids of electronic oscillating tubes, cathodes of high-voltage rectifiers and indirect cathode heaters in various electronic instruments. Tungsten is used as the counter cathode and cathode of X-ray tubes and gas discharge tubes, as well as the contacts of radio equipment and the electrodes of atomic hydrogen welding torches. Tungsten wires and tungsten rods are used as heaters for high-temperature furnaces (3000°C). Tungsten heaters work in hydrogen gas, inert gas or vacuum.
Tungsten compounds: Sodium tungstate is used in the production of certain types of paints and pigments, as well as in the textile industry for fabric weighting and mixing with ammonium sulfate and ammonium phosphate to make fire-resistant fabrics and waterproof fabrics. Also used in the manufacture of metal tungsten, tungstic acid and tungstate, as well as dyes, pigments, inks, electroplating, etc. Also used as a catalyst. Tungstic acid is used as a mordant and dye in the textile industry and as a catalyst for the production of high-octane gasoline in the chemical industry. Tungsten disulfide is used as a solid lubricant and catalyst in organic synthesis, such as the preparation of synthetic gasoline. When tungsten ore is processed, tungsten trioxide can be obtained, and then tungsten trioxide is reduced by hydrogen to prepare tungsten powder, which is widely used as raw material for tungsten materials and tungsten metallurgical materials.
In aviation and rocket technology, as well as other sectors that require high thermal strength of machine parts, engines and some instruments, tungsten and other alloys for melting metals (tantalum, niobium, molybdenum, rhenium) are used as heat-strength materials.

Q: What is plasma spray?

A: Plasma Spray, one of the thermal spray process, is used for surface treatment and protection.

In this process, the temperature can reach above 10,000℃ and the plasma is produced between anode and cathode. Suitable powder is injected into the plasma jet. The powder particles are melted and propelled onto the workpiece surface.
The advantages of plasma spray are listed as below:
* corrosion protection
* wear resistance
* clearance control – abrasives and abradables
* heat and oxidation resistance
* temperature management
* electrical resistivity and conductivity

Plasma spray has several variations. It could be divided by plasma jet generation (DC plasma , induction plasma or RF plasma), plasma forming medium (gas-stabilized plasma,water-stabilized plasma and hybrid plasma) and spraying environment(atmospheric plasma spraying (APS), controlled atmosphere plasma spraying (CAPS), variations of CAPS, and underwater plasma spraying).

It is one of the most flexible process and many powders can be applied to different base materials.

With the development of plasma spray technology, it can offer a wide selection of coating materials.
Plasma is widely used for Gas turbines, combustion hardware, printing rolls for laser engravings, industrial diesel engine piston rings, down hole tools, oil and gas products.

Q: What are the advantages of plasma spray coating?

A: The principle of the plasma spraying process is to change the surface properties of the material, use a certain heat source to heat the sprayed material to a molten or semi-melted state, blow it into tiny particles, and spray it onto the surface of the base material through island velocity airflow to form a various coating processing methods. Plasma spraying not only has the same size as other spraying methods, but also has the advantages of unlimited part size, wide base material, small processing edge, and spray strengthening of the surface of ordinary base parts.

1.The substrate is not heated, the parts are not deformed, and the heat treatment state is not changed.
Since the parts are not charged during spraying and the base metal does not melt, although the temperature of the plasma flame is high, the energy is very concentrated. The axial temperature gradient of the plasma arc is very large. Generally, the temperature rising of the parts does not exceed 200 ℃, so the parts will not deform, which is very beneficial for the repair of thin-walled parts, slender rods and some precision parts. Since the heat treatment properties of the base metal will not change below 200°C, some high-strength steels can be sprayed.

2. There are a wide range of materials that can be sprayed, and there are many types of coatings.
Due to the high temperature of the plasma flame, various spraying materials can be heated to a molten state, so there are a wide range of materials available for plasma spraying, so that spray coatings with various properties can be obtained, such as wear-resistant coatings, thermal insulation coatings layer, high temperature oxidation resistant coating, insulating coating, etc. In terms of the wide range of coatings, oxygen-acetylene flame spraying, electric arc spraying, high frequency induction spraying and explosive spraying are not as good as plasma spraying.

3. The process is stable and the coating quality is high.
Each process parameter of plasma spraying can be controlled quantitatively, the process is stable, and the coating reproducibility is good. In plasma spraying, the flying speed of particles in the molten state can reach 180-480m/s or even higher, which is much higher than the particle flying speed of oxygen-acetylene flame powder spraying of 45-120m/s. The molten particles are fully deformed when they collide with the parts. The coating is dense, and the bonding strength with the substrate is high. The normal bonding strength of the plasma sprayed layer on the base metal is usually 30 to 70 MPa, while the oxygen-acetylene flame spraying is generally 5 to 20 MPa. Since the atmosphere can be controlled by changing the gas during plasma spraying, the oxygen or nitrogen content in the coating can be greatly reduced.

Q: What are the uses of molybdenum in coating industry?

A: In recent years, the LCD (Liquid Crystal Display), PDP (Plasma Display Device) and other planar display electrodes and wiring materials like molybdenum alloy targets have attracted more and more attention. In TFT-LCD, the gate electrode is a key component, which was mainly used as the gate electrode material with Cr/AL. With the large scale and high precision of flat display, the demand for the specific impedance of the material is higher than that of previous. Besides, the specific impedance and membrane stress of chromium is only one half of molybdenum, and it is harmful to the environment and health due to the production of hexavalent Cr during etching. As a result, more and more companies are switching to Mo/AL as grid electrode materials, so the demand for molybdenum targets is increasing.
Molybdenum targets can be used with other target materials in sputtering or other technological conditions, which are widely used in semiconductor wiring, medical treatment, mechanical processing and solid lubrication.
Another important application of molybdenum in coating industry is spraying. The surface spraying molybdenum on the surface of the piston ring, bearing, extrusion equipment, engine block and turbine components can improve the wear resistance.

Q: Why refractory metals are used in the high temperature furnaces?

A: Refractory metals such as tungsten, molybdenum are ideal for high temperature furnaces due to their outstanding properties:
• Temperature up to 2800°C in vacuum or protective atmospheres
• Low vapor pressure
• Low thermal expansion
• High mechanical and thermal stability
• Excellent uniformity

Q: What is Ion implantation ?

A: Ion implantation is a material engineering process by which ions of a material are accelerated in an electrical field and impacted into another solid. This process is used to change the physical, chemical, or electrical properties of the solid. Ion implantation is used in semiconductor device fabrication and in metal finishing, as well as various applications in materials science research.
Ion implantation equipment typically consists of an ion source, where ions of the desired element are produced, an accelerator, where the ions are electrostatically accelerated to a high energy, and a target chamber, where the ions impinge on a target, which is the material to be implanted. Thus, ion implantation is a special case of particle radiation. Each ion is typically a single atom or molecule, and thus the actual amount of material implanted in the target is the integral over time of the ion current. This amount is called the dose. The currents supplied by implanters are typically small (microamperes), and thus the dose which can be implanted in a reasonable amount of time is small. Therefore, ion implantation finds application in cases where the amount of chemical change required is small.

Q: Which material is suitable for resistance welding?

A: Resistance Welding includes Resistance Spot Welding (RSW), Resistance Seam Welding (RSEW), and Projection Welding (PW). Resistance welding uses the application of electric current and mechanical pressure to create a weld between two pieces of metal. Weld electrodes conduct the electric current to the two pieces of metal as they are forged together.
Tungsten copper, tungsten and molybdenum are chosen for this application for their certain properties.

Q: What is the application of tungsten rhenium wire?

A: Tungsten rhenium wire can be used as charge wire for creating charges for positive and negative, which is employed in digital printers, air cleaners and electrostatic separators.
Tungsten rhenium wires can be also used as heating wire in E-guns and E-tubes.
For thermocouple wire measuring temperature up to 2,200 degree, tungsten rhenium wire serves in the industry due to its good properties in high temperature. This material is also common in the probe needle and TCD filaments.

Q: Why use tungsten rhenium wire as probe pin?

A: Tungsten rhenium has good conductivity, and ductility. It can transport good signal for detecting LCD and LED.