Welding S355NL2 for a special requierments project.

[metaleng123]

Hello everyone,

I have to write a welding tehnology for some parts that must be guaranteed at -60(-76 F). To give you some information, there will be both butt welds and fillet welds and the thickness will range between 10-20 mm( 0.39" - 0.78"). I usually weld this type of material(PNo.1) without any preheat. Considering the fact that this project has some special requierments should i take more precautions and add preheating?

Best regards,
S

 

[kingnero]

I've seen them fail on hardness criteria more than once when trying without preheat, so yes, probably so.
Depends (a lot) on base metal carbon equivalent, filler material and heat input.

What exactly must be guaranteed at -60 °C / -76 °F ? Water tightness? Geometry? Hardness values? Impact values? ...

 

[metaleng123]

Thank you for taking the time to answer to my thread.
Impact values must be guaranteed at -60 °C / -76 °F. I dont have the exact chemical comp yet but the carbon equivalent will be max 0.33,filler material will be E 8018-G and heat imput will range between 1.8 - 2.12 kJ/mm.

 

[DVWE]

You should look into using a nickel based electrode for meeting those impact properties.

E8018 or 8016-C1 will give you 27 Joules at -60C

E8018 or 8016-C2 will give you 27 Joules at -75C

Reference is ASME Section II, Part C, SFA 5.5, Table 4. There are many options listed in this table. I listed 2 for you.

The devil is in the details; she also wears prada.

 

[kingnero]

@ metaleng123:
I suppose you are talking about 27J as impact value?
I'm not sure what the "2" means at the end of the steel designation, but S355NL only has guaranteed impact values up to -50°C (27J longitudinal). How will you guarantee the behaviour at -60°C of the base metal?
EN 10025-3 states max. CE = 0.43 for S355NL.
And that's rather on the heavy side, those HI values...


@ DVWE:
Ni-based (muchos Ni %) or Ni-alloyed (few Ni %)?
Ni-based seems overkill, as many "standard" fillers will happily provide 27J at -40°C, and when tested they are often much better.
Can't say from the top of my head, but 27J @ -60°C should still be able to find without resorting to Ni-based fillers.
Doesn't really matter if the base metal doesn't provide this quality though, as impact testing needs to be done in both weld metal as base metal (according to ISO qualification procedure).

 

[DVWE]

kingnero,

No mucho Ni.

These electrodes are between 2% and 4%

but 27J @ -60°C should still be able to find without resorting to Ni-based fillers.

I don't agree with you on that point, as even 7018-1 is only tested down to -45C for 27 Joules.



The devil is in the details; she also wears prada.

 

[kingnero]

Yes, I concur with Ni-alloyed. Should've made that clearer in my previous post.

 

You are indeed looking at a nickel-bearing electrode classification.

Not to be pedantic, but impacts are never guaranteed. Welding in QA terms is a special process that requires a lot of other activities including procedure qualification, performance qualification, NDE, etc, that taken together provide a level of assurance, not certainty. Welding engineering is not just a matter of selecting appropriate materials.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[metaleng123]

@kingnero:
From what i understand the client's official order is for 27J @ -45 because due to API they couldn't place the order for 27J at -60( this is what the QA manager told me, don't know the exact details). What i am trying to do is to take as many precautions as possible to ensure the desiered material structure. I was thinking i could add preheating and maybe perform a welding test that i can get some impact test samples out of. Also, what HI would your recommend?

 

[kingnero]

Some testing beforehand is a good idea. These are standardised tests, in the form of procedure qualifications. Retain a decent materials or welding engineer, because this seems trivial but really isn't. Randomly adding preheat isn't going to help with impact values (!). Randomly taking impact samples isn't going to tell you much about the weld either, as there are weld material impact tests, HAZ impact tests, base material impact tests, transverse, longitudinal and through-thickness direction to take samples from, ...

A "special requirements" project deserves special attention, or when based on crowd surfing sourced info and it goes tits up, what are you going to tell your client?

Also, I'd like to see the conditions in which those heat input values are taken. I'd say you're on the high end of the scale, based on my "best practices" and the situation that I have visualized in my head; a butt weld in position PA (1G) will require about 1/3 of your minimum value for the root pass, for a wide (weaving) multi layer weld vertical up you're good to go. But then your impact values will go down again...

 

[metaleng123]

Thank you all for all of your responses.

I have one more problem. In this project there is also a weld combining AISI 4130 with S355NL/P355NL2 ( fillet weld, s= 25 mm, a=7). I have PQRs for this kind of weld using E12018-G-H4 and ER 100S-G, but the problem is that this part is working in H2S so NACE MR0175 says that the contet of Ni is limited to max. 0.99%. The question would be: what type of filler material would you choose( Impact test T=-60 27J, Ni<1%)? E 8018G can't be used because it's Rm is 672 MPa while 4130's is 688-800 MPa.

 

[CWEng]

You don't have to match the strength of the higher strenght member in dissimilar strenght joints in all the codes I've welded to. If you meet the strength of the S355NL while welding it to 4130, you should be fine.