1.1 Protection gas selection
In the welding process, the protection of gas as a protective medium and gas medium, the quality of welding has a very important impact. So the choice of gas protection needs to be changed flexibly according to many factors.
Argon gas is one of the most common protective gases in modern TIG welding. Because argon is heavier than air, it is more stable and difficult to disperse, in the process of use, which is advantageous to the welding work, usually used in the butt welding and vertical welding. Because the ionization potential of argon is lower than that of helium, under the same arc length, the arc voltage of argon is lower and the heat produced by argon arc welding is lower than that of helium arc welding. According to this kind of characteristic, the Argon Arc welding arc is easy, can control the welding arc point temperature very well, has the good inhibition to the overheating tendency which the aluminum and the aluminum alloy easily produces. At the same time, Argon has excellent cathode crushing effect, it is easy to fracture the oxide film produced in the welding of aluminum and aluminum alloy, it is suitable for the welding of aluminum and aluminum alloy. Aluminum and aluminum alloy tig welding to the purity of argon gas requirements are high, the argon purity is not less than 99.9%, but the current market sales of argon gas purity generally can meet this requirement.