Boiler Tig Rods

[05hwy28]

Hello all,

What TIG rods are acceptable for welding our Steel boilers? ER70S-2 and ER70S-6 come up the most in chaski threads, but after talking to our tig welder who works in the steam industry, he wants to weld our boiler up with ER90. This is the first I have heard of this tig rod... I've looked up very limited info on ER90S-B3 and mostly on sales sites / pdfs which do say it is a PV welding rod. Is this rod okay for our boilers?

FYI: We are using all the correct PVQ materials and specs Marty has listed here before... SA516-70 plate, SA106B Seamless pipe, SA105 couplings, SA36 stays

[BClemens]

ER70 is formulated for mild steel as opposed to an alloy like 4140. The ER90 is intended for alloy steels containing chrome and nickel so the alloy is less ductile - more rigid. ER70 is fine for boiler plate and actually the more ductile the less stress in the completed weld bead and heat affected zone. A boiler has built in or designed in rigidity so does not need an alloy (containing chrome) welding rod. I would say that ER90 would be more prone to crack in a mild steel weld joint than ER70.

bc

[05hwy28]

BC,

Thank you for your reply. I came to a similar conclusion and we are going with ER70 rods. We are taking boiler parts to our welder tomorrow!

[Marty_Knox]

One of the guidelines that I was taught is to use filler metal as close to the base metal as you can. I use a lot of SA516-70, which is 70,000# tensile strength. The ERS70-2 is the best match.