Shielding Gases for Duplex 75/25 Ar/CO2 ??????

By pipewelder_1999 (****)

Date 09-04-2008 13:56

I recently spoke to someone who was having trouble welding some 2205 with GMAW using 2209 filler AND 75/25 Argon/CO2 . I 1st suggested that their problem was related to the gas. I have welded this and qualified procedures with various gas mixes for short circuit, spray and pulsed but never used anything with that much CO2. My suggestion was based on what I have done and NOT what I have tried and tested so I may have led him wrong.

I have reviewed various manufacturers literature and can find nothing indicating that as a gas mixture to use.

What would using this gas do to the properties of the weld metal ? I strongly suggested thay contact someone in the materials department to verify this is OK however again, I may be wrong.

Any information is appreciated.

Gerald

By Stephan (***)

Date 09-04-2008 14:33

Gerald,

I do not want to line-jump by using the information which I have received once by the appreciated js55.

Thus I truly hope that he will step into this topic personally, since there is probably no one better than himself to explain this.

But dividing the CO2 content of 25% by the number of "10" would fit much better...

Best regards,
Stephan

By pipewelder_1999 (****)

Date 09-04-2008 14:37

That is what I have found. Highest being 95/5 Ar/CO2

By Stephan (***)

Date 09-04-2008 15:03

Gerald,

this is what my information is as well!

And as I said, this came directly from Jeff(!) and don't want to repeat myself about his expertise! :-)

Best,
Stephan

By DaveBoyer (*****)

Date 09-05-2008 04:41

Have You checked Ed Craig's website?

By pipewelder_1999 (****)

Date 09-05-2008 15:52

I havent recently but I think I will go back and look through it.

By Sean

Date 09-11-2008 13:05

A 75/25 shielding gas has far too much CO2 for this material and this welding process. If you were using FCAW this gas would be fine.

I've haven been able to find an article I had regarding the effect of shielding gases for DSS; however, for GMAW you could use a 98 Ar 2O2 or CO2. There are also a number of tri-mixes with a bit of nitrogen that are designed for use with GMAW on DSS. The nitrogen improves corrosion properties. More than 5% CO2 or O2 creates lots of negative metallurgical issues with the alloying agents in stainless steels. I won't go into the details. Most of the industrial gas suppliers have a trade name mix for duplex that usually contain Ar/He/N2 or Ar/He/N2/CO2.

On a side note, in one of my discussions with Chuck Meadows a few years ago, he suggested that if we wouldn't be doing a lot of work with Duplex, the FCAW process should be a lot more forgiving for this material than GMAW.

They should also keep an eye on their heat input and watch out for contamination if they are doing any carbon steel work in the vicinity.

Sean

By js55

Date 09-11-2008 19:20 Edited 09-11-2008 20:58

The advice thus far is good. With DSS you have to keep the oxidizing and carburizing gases low while still finding a way to assist broadening the penetration pattern of Ar and perhaps adding a little heat with CO2 and wetting as with O. Tri mixes have been used with great success but the complaint I have with them is expense.
Nitrogen is only used when you wish to influence the phase balance since it is a strong austenite stabilizer and can also cause the formation of Cr nitrides if overused especially if the austenite ends up high and considerable nitrogen is trapped in the remaining Cr heavy ferrite.
Let me add the question, what kind of trouble are they having?

By pipewelder_1999 (****)

Date 09-12-2008 03:11

Welder Appeal is all I know. I had told them that I was highly confident that the issue was related to the gas.