WELDING WITH ER2209 WITH GMAW ON DUPLES STAINLESS STEELS

[Fizza453]

I have to qualify a procedure using ER2209 with GMAW on Duplex Sianless Steel. Any advice please? like back purging, use of sheilding gas, interpass temperature limit?
We have to qualify procedure on 10 mm thick plate, Section IX permits 1.5 to 20 mm base metal thickness range in this case. The production joint is to be made on 3 mm plate. Our client insists on the use of GMAW instead of GTAW with arguments that GMAW is a low heat input process.
Does high speed make GMAW a low heat process?

Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN

 

[Duwe6]

ASME IX does not allow twice the coupon thickness for GMAW procedures at that thickness, unless your actual process is "hot" enough that the deposition mechanism never goes into the Short-Circuiting-Transfer mode. Non-short circuit on 2205 is very unlikely. However at 0.5"/13mm of coupon thickness, ASME does allow that standard twice coupon thickness.

Nitrogen is an alloying element for duples stainless, and makes the weldmetal stronger.

Back purge should be used, 100% Argon, or 2% Nitrogen and 98% Ar.

Shield gas should be either 98% Argon and 2% Carbon Dioxide, or 97%-Ar + 2%-CO2 + 1% Nitrogen.

Short-circuiting GMAW is a very "cold" process, GTAW is the "hottest" process for total heat input.

Interpass temperature should be 100°C, maximum.

"Cold", lumpy weld beads are preferred. A thin, small root bead is almost guaranteed to crack before the next layer can be applied. Never stop welding until the weld groove is filled at least halfway up.

 

[Fizza453]

Duwe6

Yes for GMAW Short Circuiting Mode, QW-403.10 and QW-404.32 put limit on base metal and weld metal qualification thickness if coupon is less than 13 mm thk.

What if we use 100% argon for both back purging and shield?

Nitrogen is an alloyong element for the weldmetal, what role CO2 plays when used in shielding gas in 2% with 98% argon?

Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN