Tungsten Electrode and Shielding Gas in TIG Welding

Tungsten electrode has high melting point, high boiling point, high strength, low thermal conductivity and low high temperature volatile and other good property, so it is often as a non-consumable electrode applied in welding field. Pure tungsten electrode has poor electron emission performance doped with rare earth rare earth to improve electrode property. Rare earth doped tungsten electrode has good electron emission performance and long service life. Besides, it is easy to arcing.

During welding, shielding gas is a protective medium of weld region but it is a gaseous medium of arcing. Therefore, physical and chemical property of protection gas will not only affect the protective effect, will also have some impact on the arcing ignition, welding process stability and quality of arcing.

For TIG welding (tungsten inert gas welding), there are three kind of shielding gas, including argon, helium and mixture gas. Among these shielding gas, the most widely used is argon. Argon is an inert gas. It does not react with welding metal and not soluble in the metal as well. Besides, the density of argon is heavier than air, and specific heat capacity and thermal conductivity smaller than air, so it can effective protect the molten metal from air, oxygen, nitrogen, hydrogen and other harmful elements effect. These features make argon showed good performance in welding process. It not only can play a good protective effect, but it can to stabilize the arc.

Helium is also an inert gas. It has good cooling effect, so the arc energy density is large and arc column is small and focused, while the weld joint has good penetration rate. But helium has high ionization potential, big thermal conductivity, so during the welding arc is more difficult and the energy loss is large. In generally, it is used for nuclear reactor cooling rods and large thickness aluminum alloy welding.

Mixture gas includes a certain proportion of two kind of inert gas, including argon-hydrogen mixed gas and argon-helium mixed gas. During the welding process, mixture gas in favor of increasing thermal power of arc, increasing the weld joint penetration rate, improving production efficiency.

• < Prev
• Next >