Alloy 625 welding procedure test failure 4

[DefenderJ]

I have run a welding procedure test to ASME IX. Details:
2" sch 40 pipe butt weld with GTAW using an alloy 625 filler wire. 5G positon, max interpass 150°C

It has failed the tensile test: failure in weld metal - values 750 to 800 MPa.
The parent material Alloy 625 grade 2(SB-444) is specified with minimum UTS of 827MPa.

Speaking to the filler wire supplier they would expect a minimum of 730MPa.

Speaking to someone else, they have found alloy 625 all weld metal to have UTS < 800MPa.

Can anyone provide a solution to getting an alloy 625 procedure to pass?
Thanks

 

[metengr]

DefenderJ;
I am not really sure what your problem is in this application. You are butt welding Inconel 625 to itself, using an Inconel 625 filler wire. In some cases, the weld metal can either be undermatched or overmatched to the base material being joined. This depends on the fabrication histroy of the base material, and code of construction requirements. Please read Section IX, QW-153 for accpetance criteria of tensile tests.

 

[jrupert24]

I have some data from a few years ago and we were getting 123ksi-125ksi (848 MPa) with ERNiCrMo-3 filler and that was on some thicker plate. Not much higher than the minimum. Its seems like you are very close to passing. Since your tensile specimens will be much thinner than mine, I would suspect that there may be some issues with how the lab is preparing the samples. I would actually look into how the lab is preparing the tensile specimens. 625 work hardens on the surface from machining operations and it might be possible that the lab may need to prepare the specimens in a slightly different way. Also the surface finish may need to be reviewed along with the edge prep of the specimen. I would make another piece and plan on visiting the lab.

Otherwise you might want to try another heat of 625 or another manufacturers 625.

 

[DefenderJ]

Metengr,
Thank you for your reply. I had referred to QW153.
I saw that QW153.1(c) may be applicable.
However, I was thrown by the use of "applicable section allows".

Please could you explain a little further how I can use this to validate my procedure?

Also, for the minimum specified UTS of the weld metal - is it as simple as taking this directly from the manufacturers datasheet?

Much apppreciated,
John

 

[metengr]

DefenderJ;
First off, Section IX is a service code book that supports other code book sections or for other industries other than boiler and pressure vessel.

Knowing this, there are occasions where an undermatched filler metal may be used in the design of a weld joint. Undermatched refers to the tensile trength of the filler metal that is lower than the base material being joined. In this case, if the undermatched tensile strength of the filler metal is met (using published values) AND it is understood that the filler metal is undermatched in tensile strength in comparison to either base metals being joined AND the code of construction does not prohibit a filler metal that is undermatched for use in a weld joint, this is considered a qualified WPS.

 

[DefenderJ]

Metengr,

Thanks again for your help with this.

Regarding finding out whether the code prohibits this approach - can you provide guidance on where to look in ASME VIII?

 

[weldtek]

DefenderJ,
I'm not sure what brand of consumables you're using, but, if by chance Special Metals is the one, they have an excellent technical department. If not, I'd call them anyway.

 

[metengr]

DefenderJ;
What is the application of this weld procedure? Is it a pressure boundary weld, attachment weld for internal baffle, etc?

 

[DefenderJ]

Weldtek - thanks for that advice, I will speak to them. (the consumable used was from Westbrook welding alloys)

Metengr - it is an expansion bellows weld on a heat exchanger (replacement bellows), so it is part of the pressure boundary.

I have also been advised to selectively choose a batch of filler wire that has high strength.

Cheers

 

[weldtek]

DefenderJ,
I'm not familiar with Westbrook Alloys. Are they an actual manufacturer, a repackager, or just a distributor?
I've had issues with consumables from repackagers. I've also had quality issues with certain 'Brand' name consumables, but, I've never had issues with products from Special Metals, and when I needed some assistance they were very responsive.
I use their nickel based alloy consumables almost exclusively. I say almost, because on a rare occasion I've had to use an alternate due to availability, but, I never use repackaged consumables.

 

[stanweld]

While the ERNiCrMo-3 filler metals can readily meet the tensile requirements of the Solution Annealed Alloy 625, meeting the higher strength Annealed grade is another story. You will have to search and be be highly selective in your filler metal purchase.

Can you manufacture the bellows from the Solution Annealed grade? Can you redesign the bellows for the lower strength filler metal? You can readily qualify the WPS per ASME IX using the lower strength grade of 625.

 

[DefenderJ]

Weldtek,
Westbrook are "repackagers", as you suspected.
I think I'll stick with the better known companies in future, such as Special Metals. I spoke to the special metals technical department who were very helpful - they didn't have a direct answer but gave me a lead to someone else.

This guy's solution was to qualify with either a weaker parent or a stronger filler but maintain the same P number / F number. Once the PQR is qualified the material can be changed in the WPS as long at the numbers are the same. This appears to be the same as Stanweld is suggesting (thanks Stanweld).

I will either go for solution annealed (Grade 2) alloy 625 as stanweld suggests or use something like 622 filler as the quoted UTS is 10ksi higher than 625 filler.

 

[pradipgoswami]

HiDefenderJ,

The specified Min UTS of SB 444, Gr-2(Soln Annealed),alloy N06625 is 690 Mpa or 100 Ksi. The Min UTS same alloy SB 444,Gr-1(Annealed) is 827Mpa or 120Ksi. If the tensile test results are 750-800 Mpa, then it passes Sec-IX requirements of SB 444, Gr-2 alloy.

Specified Min UTS of ER-NiCrMo-3(matching 625 filler)is 760Mpa or 110 Ksi.What was the CMTR values of this consumable? What was the Fe level in the the CMTR and on the failed coupon.

If the design requirements calls for SB 444 Gr-1 material to be used only, then the only AWS Spec which can match this strength level is ERNiCrMo-19.This filler have same level of Ni and Cr as ErNiCrMo-3, but Mo is higher 20% as against 9% (625 alloy) and very low Fe(1% max).
A change of filler wire might help.

Thanks

Pradip Goswami
Welding Engineer/Specialist
Ontario Power Generation Inc.
519-5872201,Ext-3107