Overview of arc welding; Compared with other common welding methods, because the arc welding (if not marked, the following below: argon arc welding, instead), the splash during the welding process is reduced, and good welding formation can be obtained. Because the welding current of argon arc welding is small, the welding heat input is small, and the residence time of the weld in the sensitive temperature area is short during welding, so the weld usually has better corrosion resistance and stable mechanical properties. At the same time, due to the heat input is small, the deformation caused by welding is small. When an inert gas such as argon is used for protection, the alloy elements of the welding wire are not oxidized and burned, and almost all can be transferred to the weld. However, argon itself has no effect of deoxygenation and dehydrogenation, and the cleaning requirements for welding parts are very strict before welding, otherwise the welding quality will affect the welding. For the description of using argon and / or helium gas as the protective gas in argon arc welding, see the protective gas and Helium gas; For the description of reducing gas in argon arc welding, see "argon arc welding"; Description of the oxygen added in argon arc welding: Tungsten has high melting point and low high temperature volatility, which is an ideal material for non-consumption electrode, which can be in high temperature state for a long time in the inert gas atmosphere. However, when oxygen is present, both the tungsten matrix and the addition are ablated to varying degrees, even if only 1% oxygen is present, only a few minutes can cause the visible umbrella called the tungsten ring and the diameter of the tungsten matrix above the tungsten ring is significantly reduced. The addition abates faster and causes the composition change on the surface. The addition component inside the high temperature tungsten pole spreads outward only limited. When the added component from the interior is not enough to maintain the necessary amount, the arc starts unstable and even makes the arc becomes more difficult than the normal situation. The oxide deposited in the extreme part of the tungsten ring can fall off into the melt pool, change the weld composition and then affect the performance of the welding joint. Burning serious tungsten pole can lead to local damage into the molten pool and cause tungsten sandwich. As mentioned above, argon itself does not deoxylate, and an unreasonable addition of additional oxygen may enter the weld. With the increase of oxygen content in the weld joint, it can affect the performance of the welded joint, especially its toughness. It may also affect the strength, plasticity, thermal fragility, cold fragility and aging hardening. In addition, dissolved oxygen will react with carbon to increase the tendency of stomata, and react with beneficial elements to cause burn damage and then affect the specific properties of the welded joint. tag: The welding protection characteristics of argon arc welding need to use protective gas in the welding process to isolate the atmosphere and prevent atmospheric influence. At the same time, the protective gas also has the function of improving the arc characteristics and improving the welding efficiency. Different composition and proportion of protective gas depend on factors such as cost and effect. In general, due by economic factors in conventional working conditions, argon is mostly used as a protective gas in argon arc welding, which has the advantage of higher heat input for helium in some certain working conditions, and nitrogen or hydrogen will be added in some specific cases. However, oxygen is not harmful to the tungsten pole due to its oxidation properties