welding in monsoon period

Dear Sirs,
I'd like to ask you an opinion about a problem we have had in india
some month ago.
We have welded some sheets of ASISI 430 with an electrode of 309 and
we have obtained several cracks in the thermal alterate zone. After a
lot of expensive analisys, qualified laboratories says us that the
problem is due to the strong humidity of the monsoon period (???) that
generate a classic hydrogen inter-grain rupture.
Really in india people doesn't weld in the monsoon period? It is
possible??
Or it is just a fake answers because these (expensive)
laboratories really doesn't know the real cause of the cracks?
Thanks
Reply to
stefano.marinaretti
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Highly probable. I don't cast aluminium in humid conditions as the molten metal absorbs hydrogen from the atmosphere and causes problems. You'll have to control the environment where you are welding.
AWEM
Reply to
Andrew Mawson
I can't comment on the Monsoon but it is certainly verboten to weld wet pipelines for the reason you state.
Cheers,
Bruce (bruceinbangkokatgmaildotcom)
Reply to
Bruce In Bangkok
I guess condensing humidity would cause wetness on the metal surface.
Reply to
Phil
Who spec-ed the 430? What is the application? Sometimes 430 can act as a duplex, making welding difficult.
As for hydrogen sensitivity you bet, nitrogen sensitivity is the usual killer though.
Matt
Reply to
matthew maguire
The composition of the 430 is this:
C 0,063 Si 0,401 Mn 0,311 P 0,013 S
Reply to
stefano.marinaretti
(snip)
Here's what I know about 430;
High chrome low carbon SS (14-18 Cr), good mechanical/physical properties, corrosion resistant to organic acids, very dilute salt solutions, and laughs at nitric acid... It also stands up to destructive heat scaling to 1550F.
When welded it is susceptible to grain growth with loss in ductility and toughness and is not recommended for welded sections that may be exposed to shock and/or vibration.
Because of it's resistance to chemical attack and heat oxidation resistance it is often used in oil burners, heat exchanger flues, combustion chambers (oil & gas) and annealing furnaces.
When ductility problems arise for the intended use Type 430Ti is often recommended.
The structure "should" be ferrite (except the 309 and the transition part of it).
The grain size in the HAZ is most likely the problem and I'll have to check some to see if I have anything about hydrogen contributing to grain growth???? But high heat input can cause grain growth with martensitic stainless.
Anyway I looked at some Alcan (old) data and some USS (really old) data on welding 430 (I don't have a lot of docs here at the house), and found that 430 can be spot, seam, and pulsation welded along with arc welded. All documents note that consideration for grain growth should be given. None of the docs give specific electrode recommendations.
I might assume that someone chose 309 because it is recommended for welding 416SS (a lower chrome, cheaper SS used for shafting) in a low hydrogen process (which, I think, has more to do with the sulphur in the 416 than anything else).
I also see by your chemistry above that the material is well below the max for C, Si, Mn, P and I can't believe how low the sulpher is in this day and age.... Is this the test analysis or the producers numbers?
Hydrogen embrittlement cracks usually are inter-grain as stresses cause a failure (the failure is chemical/mechanical), but so can coarse grain cracks in low alloy steel or martensitic stainless (the failure is due to energy input/mechanical).
If the cracks are in the HAZ and not the transition zone the Nitrogen/duplex steel problems are out of the question (regarding my prior message).
The lab could be right, but without knowing all the procedures involved (weld parameters) it's not certain. AND unless there has been a significant time lapse or operation at an elevated temperature the sample should still have some hydrogen contained in it. Hydrogen migration to the air can take many months at room temperature.
I'm not sure that if I knew more about your process and problem, that I could help more.
Best wishes and good luck, Matt
Reply to
matthew maguire
Are you using any pre-heat, interpass temperature control, and post-heat (soak times)? Heat treatment or annealing may need to be included after you double check your welding process.
Reply to
TinLizziedl

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