The application of gas plays a major role in the process of welding. While the ability to cut and heat relies heavily on acetylene, a wide variety of gases are used as shielding gases for welding.
Shielding gas prevents other gases in the atmosphere from reducing the quality of the welding process. Shielding gas also has an impact on several other aspects of the process, including welding torch travel speed and the quality of the weld deposit in finished form.
The type of shielding gas used depends on the arc welding method being performed and the material being welded. In order to meet the shielding gas needs of a particular application, gases are often times formulated into special blends. Some elements commonly used in these specialty gas combination's include oxygen, nitrogen, hydrogen, argon, and carbon dioxide.
Argon
The third most common gas in the Earth's atmosphere, argon is heavier than air and has a low thermal rate of conductivity. These qualities enable argon to provide solid arc welding stability and penetration. Argon is also an inert gas, which allows it to be used without impacting the composition of the welded metal.
As a shielding gas, argon is used on its own for gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW) on nonferrous metals such as aluminum and copper. It is also used in combination with other elements for GMAW and flux-cored arc welding (FCAW) projects involving the joining of steel.
Oxygen
The addition of Oxygen in shielding gases for GMAW projects can enhance arc stability. It can also improve the fluidity and wetting characteristics of weld puddles by reducing surface tension. When used in conjunction with carbon dioxide and argon, oxygen can also provide versatility to joining certain types of carbon steel.
Hydrogen
Used primarily on austenitic and duplex stainless steels, hydrogen is known for improving the weld puddle fluidity and cleanliness of surfaces. When added in small amounts to argon, it can also provide excellent weld bead appearance and improve the travel speeds of GTAW projects involving austenitic steels by as much as 25 percent.
Nitrogen
This gas can improve weld penetration and arc stability of austenitic and duplex stainless steels. Additionally, it is used as a shielding gas additive to increase the mechanical properties and pitting resistances of super-austenitic and super-duplex stainless steels. Nitrogen also provides good root protection for metal when used with 10 percent hydrogen.
This is just a small overview of some benefits shielding gases provide to the welding process. For more information check out online course on eVersity :http://eversity.co/elearning/Shielding_Gas.aspx
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