GTAW

[dropthepuck]

Why is a purge or backing gas not necessary when welding carbon steel using the gtaw process but is necessary when welding higher chromes. Is it the chrome content?en

 

[metengr]

dropthepuck;
Yes.

 

[SJones]

Well yes, plus the different effects of oxidising carbon steel and stainless steel. The stainless steel is more dependent upon maintaining a 'pristine' surface for such things as corrosion performance than is carbon steel. A heavily scaled stainless steel won't perform very well in corrosive media.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[strider6]

You need the back purging to avoid the oxydation of the welding that in certain environments can lead to higher or non expected corrosion.
Above a certain content of Cr in the material, if i remember well 5%, you always need the back puring.

Strider

http://www.corrosionist.com