Carbon dioxide CO2: stable chemical properties, no combustion, no combustion-supporting, can decompose CO and O at high temperature, has certain oxidation property to metal. It can liquefy, absorb a lot of heat when liquid CO2 evaporates, and solidify into solid CARBON dioxide, commonly known as dry ice. CO2 CO2 can be used as protective gas when welding, if CO2 gas protective welding and CO2+O2.CO2+Ar mixed gas protective welding.

Argon: Inert gas, chemically inert, does not interact with other elements at room temperature and high temperature. In argon arc welding, plasma welding machine cutting is as a protective gas gas mechanical protection.

Oxygen O2: colorless gas, combustion auxiliaries, very active at high temperature, combine with various elements, when welding, oxygen into the molten pool will oxidize metal elements, play a harmful role. In welding and combustible gas mixed combustion, can obtain extremely high temperature, used for welding and cutting, such as oxygen-acetylene flame, hydrogen-oxygen flame, and argon, carbon dioxide and other proportional mixing, can be mixed gas welding.

Acetylene C2H2: commonly known as calcium carbide gas, less soluble in water, soluble in alcohol, a large amount of easy acetone, mixed with air and oxygen to form an explosive mixture of gas, burning in oxygen to produce 35,000 ℃ high temperature and strong light. Acetylene is commonly used in oxyacetylene flame welding and cutting.

Hydrogen H2: can be burned, inactive at room temperature, very active at high temperature, can be used as a reducing agent for metal ores and metal oxides. During welding, it can dissolve in liquid metal in a large amount, which is easy to form pores when cooled. Hydrogen can be used as a reducing protective gas during welding and mixed with oxygen for combustion, which can be used as a heat source for gas welding.

Nitrogen N2: Chemically inactive, it can combine directly with hydrogen and oxygen at high temperatures. Entering the pool during welding is harmful. Basically does not react with copper, can be used as a protective gas. Nitrogen arc welding, nitrogen as a protective gas, welding copper and stainless steel, nitrogen is often used for equal arc cutting, as an outer protective gas.