Quality impact due to shield gas purity for welding

[PAN]

Refer to ASME II SFA 5.32, minimum argon purity is 99.997%.
- What are the quality impacts in case of use lower purity (99.9% or 99.95%)?
- Please advise me about some technical references for the subject.
Thanks in advance...

PAN

 

[stanweld]

Increased porosity, increased potential for hydrogen cracking, decreased ductility to name a few quality related problems in welds.

 

[metengr]

You can Google shielding gas purity effects for technical information. There is information and numerous papers on this topic.

 

[PAN]

I have read a book "Welding Essentials - Questions and Answers" by William Galvery and Frank Marlow. The book describes about welding grade argon with minimum purity of 99.95%.

I intend to use filler metal SFA 5.18, should I use minimum gas purity 99.997% per SFA 5.32? Is it mandatory requirement?

Some experienced personnel in my company comment that the requirement of SFA 5.32 is not practical in the oil and gas industries.

 

[stanweld]

SFA 5.32 is not mandatory unless required by Contract specifications. Acceptable workmanship quality can be obtained using 99.95% purity Argon shielding gas with carbon steel welding filler metals under SFA 5.18 provided you do not require very low temperature impact property requirements.