Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
(OP)
Trying to decide between 100% Argon and 100% Nitrogen for the backing gas. We are working in the 1/4~1/2 inch range of BM thickness, 1~6 inch diameter.
I would like opinions drawn from actual experience, and if the requirements differ for the two alloys.
We will do damming and purge gas oxygen testing of course.
.
I would like opinions drawn from actual experience, and if the requirements differ for the two alloys.
We will do damming and purge gas oxygen testing of course.
.
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"





RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
Nitrogen is not an inert gas. Highest quality and minimum heat tint will be attained using argon gas for the root purge on all grades of austenitic stainless steel.
My feeling on the subject is simple. If you can afford the price differential between carbon steel and austenitic stainless steel and optimum properties and corrosion resistance is needed, you can afford to use argon to protect the root surface from oxidation.
Best regards - Al
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
Best regards - Al
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
My research is also telling me argon, but I am up against a spec that mandates nitrogen.
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
You will be using N2 in the weld gas correct?
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
No, argon for the shielding gas. I guess my real question is whether nitrogen can be absorbed into the molten metal.
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
Tried to copy paste from a paper "Guidelines for the fabrication of Duplex Stainless Steels" by the International Molybdenum Association but unable.
They recommend Argon backing gas with up to 3% Nitrogen for the more highly alloyed Duplex Stainless Steels.
While the addition of Nitrogen increases electrode wear, the addition of Helium partly offsets that.
Hope that helps,
Cheers,
DD
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
Not necessarily
Look here on page 7 and 8.
http://www.outokumpu.com/SiteCollectionDocuments/D...
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
Ferrite was measured on metallographic sections, and agree reasonably well with magnetic measurements made in the shop. Spec is 35~60% α, the same for all welding processes.
α content:
1- Root weld - 60% α
2- Root HAZ - 30% α
3- Cap weld - 35% α
4- Cap HAZ - 65% α
No deleterious phases observed.
Conclusions:
a) 1&2 tell me that I do not need nitrogen in the backing gas, and that heat input could be higher.
b) 3&4 present a dilemma. If I increase heat input and/or interpass temp I risk having too little ferrite in the weld, but I need slower cooling to keep α from going too high in the HAZ.
Comments, advice?
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
I am stuck as to how to tackle the cap pass problem. No deleterious phases observed, so there is scope to increase heat if necessary.
.
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
RE: Duplex S31803 vs. S32205 - Purge Gas for GTAW Pipe Welding
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"