What are the common use problems of tungsten electrode?
Because of its high melting point and good high temperature performance, tungsten is the best material for electron emission and the best choice for arc starting electrode of argon arc welding. The earliest argon tungsten welding electrode is pure tungsten electrode, but the electron escape work of pure tungsten electrode is relatively high, at about 4.52eV, it is not easy to arc under the condition of small and medium current. So behind all of electron emission materials research is to reduce the electronic work function, which is the earliest use of doped tungsten electrode materials of thorium tungsten, is mixed with 1-2% in tungsten oxide thorium, the mixed oxide thorium, can effectively enhance the electron emission ability of the tungsten electrode, the electronic work function to reduce to 2.63 eV, so far, Thorium tungsten electrode is also the most widely used tungsten electrode material. But thorium is a radioactive material. Although thorium is relatively low in radioactivity, and the amount of radiation is even lower when the tungsten coating is used, it does not conform to the current idea of advocating environmental protection.
Thorium tungsten after all the study of electrode material is around to avoid radioactive hazard, again on the electron emission properties of infinite close to or even greater than that of thorium tungsten materials to study, on the research of this material, China is a walk in the forefront of the world, in the 70 s invented the cerium tungsten electrode materials experts in our country, in the 80 s lanthanated tungsten electrodes are widely used in European market, The Soviet Union also pioneered the use of yttrium tungsten electrodes for argon arc welding from that era. Cerium tungsten, lanthanum tungsten and yttrium tungsten are the electrode varieties developed by material experts in different countries to replace thorium tungsten electrode. International Standard Organization formulated ISO684 standard as early as 1984, which covers the composition, color code, appearance, packaging and so on of these tungsten electrode varieties in a broad range. Our national standard on tungsten electrode was formulated in 2015 and released GB/T31908-2015, which was implemented on June 1, 2016. As tungsten resources are China's superior resources, so now more than 90% of the international categories of tungsten materials are produced in China.
Existing brands of tungsten electrode have their own advantages and disadvantages: Thorium is all-round comprehensive properties of tungsten electrode, tungsten, but radioactive, cerium tungsten electrode arc starting performance is the best, but the bearing ability of the large current is poorer, lanthanum tungsten electrode burning resistance ability is better, but in the preparation of lanthanum tungsten materials, such as low content WL15 (gold) head of lanthanum tungsten not easy arc starting, and high levels of WL20 (blue) materials processing performance fell sharply, not easy molding, The cost is high. The advantage of yttrium tungsten electrode (WY20) is that the arc column is strong, which has an advantage in the case of high melting depth requirements. However, yttrium material is easy to volatilize at high melting temperature, which leads to poor welding sustainability. Pure tungsten and zirconium tungsten electrodes are suitable for AC welding only. There may be no arc in DC welding.
