ER80SNi1 filler metal

By js55

Date 11-15-2011 22:46

You're preheating to 400 (ostensibly for the 1045) and cookin the thing. What's your hydrogen concerns?

By AceMet

Date 11-15-2011 22:58

My concern is the higher strength filler metal with the lack of the LowHi shielding from a coated electrode. So you think I am being too fussy? I appreciate the feedback. I just don't see an advantage or even good reason to use 80,000 psi filler metal when the base metal is dead soft. The risks seem to out weigh the benefits.

By Lawrence (*****)

Date 11-16-2011 04:30

Solid wire GMAW is as Lo-Hi as is possible to accomplish.

By DaveBoyer (*****)

Date 11-16-2011 04:46

I agree with You, but I do see His point that there is nothing to be gained by overmatching the A106 pipe with 80KSI filler.

By Tyrone

Date 11-16-2011 11:29

AceMet,
You should talk to the Engineer to determine why he/she is specifying 80k filler. They may have just wanted a high safety factor "just in case".
Tyrone

By js55

Date 11-16-2011 12:40

1045 is a 90ksi material. The filler a min spec 80. The carbon steel a min spec 60. The nickel steel filler will demonstrate greater toughness and ductility and perhaps absorb cooling stresses. It spreads the strength transition out across the entire weld cross section as opposed to an abrupt transition at the fusion line of the nickel/1045 interface. The mechanicl logic is not unlike a similar mechanical logic used when B3 filler is utilized for dissimilars between P22 and P91. You will also get higher carbon dilution from the 1045 into a carbon filler than you will with the nickel filler. Not only would htis increase the crack sensitivity of the carbon filler, but the nickel filler provides ductility to accomodate any carbon migration.
Not saying this is what the engineer had in mind, but it is a few thoughts anyway.
Is it overengineered? Maybe. But it wasn't hard to find some logic.

By ozniek

Date 11-16-2011 13:18

Hi AceMet

I interpret your statement "non code weld" to mean that this welding procedure is not qualified. Am I correct? If it is qualified, then the "powers that be" have obviously tried this out through procedure tests, and found good results, in which case you may wonder why it is being done, but changing it will not really be an option. At any rate, here is my thinking as to why they may be going this way:

A significant problem with this weld will be root cracking, because the carbon pick-up from the AISI 1045 will make a standard E7018 root deposit rather brittle, and the shrinkage stresses experienced in the first run or two will be high compared to the throat thickness of the deposit. By using the GMAW (presuming it is dip transfer) you will minimise the dilution with the base metal. (Possibly from around 50% for SMAW root, to around 25% for GMAW root, where the dilution from the AISI 1045 side will be half of the total dilution, assuming the same amount of penetration on both sides of the joint.) The ER80S-Ni 1 fillers are designed for improved toughness, (Normally used in impact test applications, and also often in applications where CTOD testing is to be done.) so they should have a better chance of surviving the excessive shrinkage stresses in the root run.

Once you have survived the biggest failure potential in the weld (the root) you will then turn to a filler and process that will give acceptable results once PWHT'ed. (The E7018)

I have not done any calcs to verify that the ER80S-Ni 1 will have a suitable toughness given the expected dilution, but my gutt feel is that it should do the trick. (Hopefully the welding engineer that specified this filler has done the calcs, or has experience doing this weld.)

Let us know how the job went, so that we can see if this was a good strategy.

Regards
Niekie