The Story of Tungsten Industry: A Centennial Journey of Tungsten Wire Again

This article is selected from the first prize work of the Science Popularization Essay Campaign of the China Tungsten Industry Association, titled "A Hundred Year Journey of Tungsten Wire Resurrection". The author is Miao Bing, a senior engineer at the Tungsten Wire Factory of Zigong Cemented Carbide Co., Ltd. Chengdu Branch.

The fine wire made by forging and drawing pure tungsten bars is tungsten wire.

The appearance of tungsten wire

The first appearance of tungsten filament was the filament used for incandescent lamps.

In 1903, Hungarian scientists heated carbon filaments in halogen oxide vapor containing tungsten with hydrogen to high temperatures, completely replacing the carbon with tungsten, thus producing tungsten filament bulbs. The tungsten filament prepared by this method has severe brittleness.

In 1904, A.Just and F. Hannaman used a carbon free binder to mix with tungsten compounds, then extruded into wires, and then heated in hydrogen to reduce to metal. The tungsten wire produced by this method is very brittle, but its light efficiency is much better, replacing carbon wire, osmium wire, and tantalum wire for making light bulbs.

Tungsten wire preparation process

In 1909, Coolidge of General Electric Company in the United States obtained tungsten billets through powder metallurgy, and then used mechanical processing to produce tungsten wires with ductility at room temperature, laying the foundation for the tungsten wire processing industry and also laying the foundation for powder metallurgy. However, this "ductile" tungsten filament still exhibits significant brittleness after the bulb is ignited.

In 1917, Perth invented tungsten wire that remained "undeformed" at high temperatures. At first, he used a refractory crucible to calcine WO2 while preparing pure tungsten. He accidentally discovered that the tungsten wire spiral made of tungsten powder reduced from this WO2 was mysteriously no longer sagging after recrystallization. Subsequently, after 218 repeated experiments and verification, he finally discovered that potassium and sodium silicate were added to tungstic acid (WO2 · H2O), and the tungsten wire was prepared through reduction, compression, sintering, processing, etc. After recrystallization, it formed a fairly coarse grain structure, which was neither soft nor anti sagging. This was the earliest non sagging tungsten wire. The discovery of Perth laid the foundation for the production of non sagging tungsten wire, and to this day, the United States still refers to non sagging tungsten wire as "218 tungsten wire" to commemorate Perth's significant discovery.

The production process of modern tungsten wire has been improved more than a hundred years ago, but the basic principle has not changed. The improvement results are mainly reflected in the further improvement of the high temperature resistance and mechanical properties of tungsten wire. For example, adding 0.5%~3% thorium or cerium into tungsten wire to make tungsten thorium wire or tungsten cerium wire can reduce the work function of tungsten wire, and adding 3%~5% rhenium to make tungsten rhenium filament has better anti fracture effect.

The use of tungsten wire

1.One hundred years as the king of light sources

Tungsten has a high melting point (3410 ℃) and low vapor pressure, making it an ideal material for electric light sources. Since the invention of non sagging tungsten wire in 1917, the vast majority of tungsten wires have been used to make various lighting filaments, electrodes for gas discharge lamps, argon arc welding electrodes, and heating elements for vacuum evaporation plating. With the improvement of the power industry and people's living standards, electric lighting is becoming increasingly popular around the world, and tungsten wire, as a light source for electric lighting, has also experienced its high light moment.

The emergence of LED has changed the dominance of tungsten wire as a light source. According to the research data of the United States Department of Energy on the life cycle of lighting products in 2012, the average total energy consumption during the production, transportation and use of LED lamps is only 1/4 of that of incandescent lamps.

In order to promote energy conservation, emission reduction, and address climate change, most countries and regions have issued "no white orders" since 2012, gradually prohibiting the production and sale of incandescent lamps. At this point, tungsten wire has withdrawn from the general lighting industry.

2. Tungsten wire regains its vitality

Micro steel wires are widely used in fields such as textiles, mechanical wire ropes, and cutting lines. However, with the development of industrial technology and the improvement of material performance requirements, the shortcomings of difficult processing and low strength of micro steel wires have gradually emerged.

With further research on tungsten wire, scientists have found that compared to micro steel wires, tungsten wire has characteristics and advantages such as higher strength, finer tensile diameter, and better flexibility. Therefore, it has gradually been used to replace micro steel wires in recent years.

Textile industry

Replacing fine stainless steel wire with tungsten wire in the production of anti cutting gloves can increase the cutting level by more than 2 levels. Tungsten wire, which is twice thinner than stainless steel wire, can have a strength of more than twice that of stainless steel wire; And tungsten wire can be processed into extremely fine wires, up to 3 μ m. It can make the finished labor protection gloves more excellent in softness, improve the protection level, and wear more comfortable and flexible. In cutting resistant situations, it provides high protection for workers' hands while also providing a flexible user experience.

Anti cutting gloves

Photovoltaic industry

In the production of monocrystalline silicon in the photovoltaic industry, wire ropes need to work at high temperatures of 1000-1200 ℃. The service life of wire ropes made of stainless steel wire is only 2-4 times, while wire ropes made of tungsten wire can reach more than 40 times, greatly improving equipment utilization and product quality, and reducing product costs.

At present, the sales specifications of mainstream enterprises' diamond thread are 35-38 μ The m-line is the main line, but it should be directed towards 35 μ The exploration of wire diameters below m will involve the conversion of busbar materials. Relatively speaking, tungsten wire has advantages such as high toughness, extremely fine machinability, and good cutting performance, with a larger space for fine wire. The trend of replacing tungsten wire for photovoltaic cutting is becoming increasingly evident.

Diamond wire structure for silicon wafer cutting

Medical field

In the medical field, ultrafine tungsten wire has become the preferred material for the production of micro mechanical wire ropes used in modern surgical robots, mainly due to its fatigue resistance and excellent tensile strength. Manufacturing diameter 0.5mm, 19 × The 37 structure silk rope needs to use fine threads with a diameter of only 0.0127mm, which is only one-fifth the fineness of hair and almost invisible to the naked eye. Thanks to the excellent flexibility and wear resistance of tungsten, this has created a miracle for innovative surgical applications. On the contrary, if such robotic medical devices use stainless steel wire ropes, their service life will be greatly shortened, and the likelihood of surgical failure will also increase.

This tungsten wire rope can also be used to drive the movement of human arms, elbows, and wrists. By using tungsten wire ropes to drive the skeletal muscle movements of surgeons, rather than being driven by the doctor's own body as usual, the robot can reduce the burden on doctors and prevent them from feeling tired and tired after performing multiple surgeries.

Glass field

In cold regions, heating devices for car glass are essential. A heating wire made of fine tungsten wire is placed in a glass interlayer. Due to the fine tungsten wire, it will not obstruct the field of view, and the tungsten wire has a small expansion coefficient. After being electrified and heated, it will not cause glass breakage, and the heating is fast, which can quickly achieve the goal of defrosting and snow removal.

Industrial testing field

Industrial scopes can be said to be a branch of non-destructive testing or a specialized testing technology. Industrial endoscopes are mainly used in fields such as aerospace, construction, agricultural machinery, and healthcare. Due to its special size design, industrial scopes allow us to easily and accurately observe the internal surface structure or working state of the object without damaging the surface of the object being tested. Tungsten wire flexible tube is a tungsten wire outer woven mesh for industrial scopes, super wear-resistant, with a general diameter of about 5.2mm and a working length of 1200mm. It has an insertion scale and is waterproof, and can be widely used in heavy machinery processing industries such as mechanical processing and automotive engines.

Using an industrial endoscope to inspect automotive engines

Tungsten wire, which has gone through a hundred years of history, once warmed our homes, illuminated our roads, and also decorated our cities with colorful colors. Today, it has completed its historical mission as a light source, gradually fading out of the lighting stage; But in new fields such as textiles, photovoltaics, healthcare, and glass, it is embarking on a new glorious journey with its stronger and more resilient characteristics.

Note: This article is reprinted from: Chinese Tungsten Industry Academic Journal (if there is any infringement, please contact us promptly to delete it)