Weldability 1.4418 to AISI 316 1

[XL83NL]

Ive got a martensitic steel (X4 CrNiMo 16-5-1 | wst 1.4418), which is to be welded to AISI 316.

I couldnt find a UNS nr or AISI designation for 1.4418, Im having a hard time determining weldability and filler metal selection (if possible). API RP 582 is of little help.

I was able to find that 1.4418 is a high strength steel
Wall thicknesses and diameter are small (dia around 1/2", 3-4 mm wall thickness). Service is 200 bar(g), 450 C, hydrogen/nitrogen gasmixture or liquid oil.
Any ideas on weldability and filler metal selection (and/or possible PWHT)?

 

[metengr]

I reviewed the literature on this low carbon, martensitic stainless steel. It does appear to have good weldability. To join this material to the 316 stainless steel, I would use either 309 or Inconel (Ni-base) filler metal. What I would do is to butter the martensitic stainless steel with elevated preheat first. Once this is completed, PWHT the buttered martensitic stainless steel at the recommended temperature of 580 to 590 deg C (around 1075 - 1100 deg F), per the literature. After PWHT, complete the remainder of the weld joint with 309 or Inconel using minimum preheat and keep the interpass temperature below 350 deg F. No PWHT is required.

Second comment is to qualify a WPS using the above approach.

 

[XL83NL]

thanks metengr for your professional opinion. I didnt review the weldability part of the pdf yet.
now that Ive done (also read this one), im questioning the necessity of buttering/PWHT (assuming that by buttering you mean the same principle as cladding, i.e. a means to create a transition layer like in a black-white connection) for a 3-4 mm thick part.
given the material thickness of the 2 parts to be joined (by means of one full pen circ butt weld), I can see the benefit (and a parallel to B31.3) for preheating any weld prep to say 150-200 C, but why the buttering and PWHT?

 

[metengr]

XL83NL;
After reviewing the technical brochure on the martensitic/austenitic stainless steel, the recommendation in the technical brochure was to perform a tempering operation (e.g. to reduce residual stresses and to soften the base metal HAZ). This tempering is similar to a PWHT. So, instead of subjecting the entire weld coupon with the 316 stainless to the recommended PWHT, you first deposit a butter layer only across the weld prep side of the martensitic stainless steel and PWHT. Once this operation is completed, the 316 stainless steel material would be welded as though it was being welded to either 309 or Inconel (depending on your filler metal selection) over the martensitic weld prep surface (there is no interface other than you PWHT'd one side of the coupon). If you believe a PWHT is unnecessary, try completing a weld coupon without buttering and with buttering and se how the mechanical properties (tensile and bends testing) turn out.

 

[XL83NL]

thnx again metengr, for the helpful reply. I have no experience with such high strength martensitic stainless steels, so Ill go with your advice as a first.

 

[metengr]

XL83NL;
I have one more recommendation for your consideration; try a weld coupon using straight 316L electrode with minimal preheat, no buttering nor PWHT (as described in the first brochure). Being an austenitic filler metal the 316L weld joint will possess low strength but so will the 316 stainless steel tube in comparison to 1.4418 base material. For the wall thickness you described this may work. Again using a weld coupon will be cheap insurance and assure you have done your due diligence.

 

[XL83NL]

thnx metengr. do you reckon visual exmiantion of this coupon suffices (perhaps wghen possible followed/preceded by a hydrotest)? adding more NDE would porbably as expensive as when doing preheating and PWHT+buttering.

 

[metengr]

XL83NL;
Yes, I would recommend as a minimum visual inspection. Your project peaked my interest when one of the brochures stated 316L as a possible electrode, presuming lower strength of the weld region is acceptable. However, when I did a brief check using the Delong diagram the use of 316L filler metal places the dilution zone of the weld region in a less than desirable mixed phase region with little ferrite content, which means hot cracking can be possible. So, this was my way of recommending a weld coupon demonstration to pin point what will work best for you because you just never know for sure. One good thing is the carbon content is low for the 1.4418 base material, which relates to hardness and hardenability concerns in the weld region.

 

[Guest102023]

I think you should call in a welding engineer. By the sound of it you are a mechanical who has been ordered to wade into the metallurgical deep end.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[XL83NL]

Which is why I orientate here first. Yes Im a mechanical, not an IWE, but do have some background on welding.
Just not that familiar with this material. The literature and practice I know of don't usually deal with these configurations (they're more on thicker stuff).
I have enough info at first hand to make a plan forwards (which probably is to ask for the part to be made of 316 instead of the X4CrNiMo16-5-1).

 

[wegm]

for some extra information you may have a look at this link

http://www.weldinguide.com/gdanastasiadis/viewtopic.php?f=2&t=4

 

[XL83NL]

What's the use of that link, wegm?

 

[DekDee]

Had to weld some 316 nozzles to the outside of some large pump casings made from CA6NM quite a few years back.
The recommended procedure from the Sandvik welding engineering department in Sweden was exactly what metengr has proposed.
Butter the CA6NM, PWHT , machine the surface, drill the hole then weld the 316 nozzles on.
Can't remember the exact filler materials used but remember it cost over $20,000 for the CA6NM coupon - the only piece available in Australia at the time (50 mm thick).
Regards,
DD

 

[gtaw]

Just out of curiosity, have you tried using the WRC diagram as modified by D. Kotecki and J. Lipold?

The modification expands the WRC diagram to include carbon, low alloy steels, and high alloy steels. It indicates the solidification mechanism and the predicted ferrite number.

If I remember correctly, doesn't the Delong Diagram yield a prediction of the percentage of Ferrite rather than the Ferrite Number?

I'm just trying to pick the mind of the Master. I hope you are not offended.

Best regards - Al

 

[XL83NL]

No I havent. Do you mean method described in this article?

PS; we decided to quit the project and go for another route. There was no way the weld could've be made of a substantially good degree so as to assure no defects. The first test piece showed micro re-heat cracks in the martensitic part, after PWHT.

 

[wegm]

XL83NL, you are right, by my mistake I have posted incorect link. Please note that I would like to post this link:

http://www.weldinguide.com/viewtopic.php?f=5&t=58

that describes a similar case and may you could be helped

 

[wegm]

Sorry, I think that the above link doesn't work. Please see the correct link:

http://www.weldinguide.com/gdanastasiadis/viewtopic.php?f=5&t=58