Intermitent Slag on 321S/S

[vanci]

I can't seem to figure out where occasional slag is coming from. I am continuously welding 321 S/S tube at 40ipm, 50-55amps, and using helium and argon for shielding gas. The slag only appears every 20-40 feet, is sometimes 3-5 droplets or a short soid layer. I am asuming it is contamination of some type but can't find what is causing it. Also, this condition does not exist at 30ipm and 40 amps. Any ideas would be helpful.

Thanks

 

[metengr]

It is not slag because I am assuming you are using the gas metal arc welding process (MIG), which would not form slag. Are you seeing this visually in the weld puddle? Are you performing RT or UT of the welded tubes to conclude you have defects?

 

[EdStainless]

Ok, how about we call it 'oxide weld inclusion'?

Weld defects with both oxides and gas holes are not uncommon in 321. They are both related to the alloy itself. The Ti added for stabilization makes these issues much more likely.

The trick in 321 is not preventing the issue, itis making sure that it is spread out and in small enough pieces that it doesn't matter. I presume that the reason you are seeing it at the higher weld current is that the weld solidifies more slowly and the impurities have a chance to gather into larger formations.
In my experience 321 is more sensitive to cleanliness than other stainless grades. This includes the edges, near surfaces, gases and everything. Minor fluxuations in weld current, torch height, or travel speed will make the situation worse.
That said, some heats of 321 are just a bear to weld.

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