Types and characteristics of mixed gases in welding

Common gas mixtures are as follows: 1. The advantages of Ar+He argon are very stable arc combustion and minimal spatter. The advantages of helium gas are high arc temperature, large heat input of base metal and fast welding speed. Using argon as the matrix and adding a certain amount of helium, the advantages of both can be obtained. When welding large thickness aluminum and aluminum alloy, the use of Ar+He mixture gas can improve the weld penetration, reduce the porosity and increase the productivity. When the thickness of the plate is 10-20mm, He with a volume fraction of 50% is added. When the plate thickness is greater than 20mm, HE with volume fraction of 75% ~ 90% is added. When welding copper and copper alloy, Ar+He mixture gas can improve the wettability of welding seam and improve the quality of welding seam. The proportion of HE is generally 50% ~75%(volume fraction). 2, Ar+H2 Adding H2 to argon can increase the arc temperature and increase the heat input of the base metal. For example, when TIG arc or plasma arc welding stainless steel, in order to improve the welding speed, the volume fraction of 4% ~ 8%H2 is often added in argon. Using the reducibility of Ar+H2 mixture gas, it can be used to weld nickel and its alloys to suppress and eliminate CO pores in nickel welds. However, the added H2 content (volume fraction) must be less than 6%, otherwise it will lead to the formation of hydrogen pores. When N2 is added to Ar, the temperature of the arc is higher than that of pure argon. It is mainly used for welding copper and copper alloys. Compared with Ar+He mixed gas, this kind of mixed gas has the advantage of more N2 sources and lower price. The disadvantage is that the welding spatter, and the weld surface is rough, welding process also accompanied by a certain amount of smoke. 4, Ar+O2 mixed gas has two types: one containing O2 (volume fraction) is low, 1% ~ 5%, used for welding stainless steel; The other one has a higher content of O2 (volume fraction), up to more than 20%, and is used for welding low carbon steel and low alloy structural steel. The phenomenon of arc cathode spot instability (cathodic drift) can be overcome when pure argon is used to weld stainless steel by adding 1% O2 in pure argon. Drift: cathode arc itself has rapid and viscosity, for ferrous metals, because they had not magnesium oxide film on the surface of the aluminum alloy density, in the process of welding, arc is always looking for metal oxide point on the microcosmic surface gathered themselves together, and as a result of the arc jumping and viscosity, cause arc discontinuous, also can produce arc offset, namely cathode drift, leading to the instability of arc. Adding a certain amount of oxygen, the metal surface will be oxidized during welding to ensure the stability of welding arc. 5, Ar+CO2 is widely used in welding carbon steel and low alloy structural steel, can improve the impact toughness of the weld metal and reduce the splash. 6. Ar+CO2+O2 can be used to weld low carbon steel and low alloy structural steel, which has good effect on weld forming, joint quality, droplet transition and arc stability.铜焊丝,Copper Welding Rods,铝焊丝,aluminium welding wire,镍焊条,Nickel electrode,药皮焊条,Flux Coated Brazing Welding Rods