Electric arc or TIG?

[MedicineEng]

Dear All:
I confess my little knowledge on welding issues and that is why I would like to ear from you.
My problem is the following:
I need to ask my workshop guys to make some weldings in 904L for some pipelines. The issue is regarding the option of welding: electric arc or TIG? Which are the advantdges and disadvantges of each method?
I know that TIG is much cleaner and makes the weldings much nicer, besides, doesn't affect much the properties of the metal. Since these lines are going to transport corrosive products, it is important to choose the method that least degrades the chemical/mechanical resistance of the material.

Thanks a lot for your help.

PR

 

[metengr]

PR;
If you are going to transport corrosive products, I would suggest using a combination of GTAW (TIG) for the weld root and SMAW (arc) for the balance of welding. You could go all GTAW, depending on the size (OD and wall thickness) of your piping system.

The reason for going with the GTAW root is to provide a butt weld joint that can pass radiographic examination (RT). We routinely use GTAW/SMAW for pipe welding.

As far as advantages with GTAW, the heat input is localized and you have no chance of slag entrapment in the weld root versus SMAW. The benefit of SMAW is weld deposition rate in comparison to GTAW.

 

[arto]

see:

http://www.alleghenyrodney.com/pages/products/PDF/al904l.pdf

http://www.avestapolarit.com/upload/AST/docs/AST 904L.pdf

http://www.asttube.com/upload/AST/docs/ast_techpaper_dubaia.pdf