Welding Nickel Alloys & Interpass Temperature

[Dlew]

What impact does interpass temperature has in welding of nickel alloys?
What are the recommendations?

[ivani1]

Low interpass temperature is recommended for nickel alloys.
API 582 should be a good reference in this case.
Check out which Ni alloy are you dealing with.
Recommendation is between 150 - 200 C.

[mechcolor]

Based upon the material P-number, API 582 enlists the recommended value of interpass temperature.
For your specific case, just check P-number and refer.

[Dlew]

My interest is towards the non-compliance of ensuring maximum interpass during welding of nickel alloys.
We are dealing with Inconel 625.

[octane]

P-number is 43 for Inconel 625 and the maximum interpass tempearature as listed in API 582 is 175 C.
Checked and verified from 2023, 4th edition I have.

My interest is towards the non-compliance of ensuring maximum interpass during welding of nickel alloys.
We are dealing with Inconel 625.

[Dlew]

Thanks but in case if that is not complied with, what could actually happen, and how to then rectify?
Would non-compliance be detrimental?

[mechcolor]

Alright, got that.
See higher interpass temperature or loose control would eventually result in:
1. Liquation cracking
2. Loss of corrosion resistance (Cr depleted grain boundaries)
3. Excessive residual stress

[Dlew]

Correct, thanks.
Now what control should we be having in place?
Welder & company seems to be in a hurry to finish the welds and go.
We do not have dedicated QC team in place to monitor all this.
What do you recommend? We perform random testing ourselves, and let them re-do the welds?

Alright, got that.
See higher interpass temperature or loose control would eventually result in:
1. Liquation cracking
2. Loss of corrosion resistance (Cr depleted grain boundaries)
3. Excessive residual stress

[ben]

Now these are some of the practical difficulties which the EU faces when controlling the welding at site.
Compliance with qualified WPS requires a 3rd party or site QC team to be in place. And they need not only to be having WPS documentation only but over and above, the specifications which are required to be followed.
Think compliance with ASME IX created WPS is one thing for qualification side but having your own controls in place mandatory for long service life of weldments is another (API 582, company's specifications etc.).

[Dlew]

Ben, that was exactly what I was looking forward to better understand and implement. Qualification of a welding procedure with all essential variables is one thing. You see interpass temperature is not even an essential variables, won't force pre-qualification but it would significantly impact the weld once it is in service. And here we need to have control over and above what WPS /PQR ask for. Thanks.