NiCrMo-3 or 309L for Welding Carbon Steel to Stainless Steel 1

[iam42]

Hi Guys,

I am seeing more and more customers specify NiCrMo-3 for welding dissimilar welds instead of 309/309L, i.e CS to SS.

Can anyone help me understand why?

Thanks

 

[stanweld]

Generally due to expansion coefficient mismatch issues when the carbon steel is subject to PWHT, or operating at temp above 500F to 600F or operating at cyclic temperatures and the stainless steel is either 316, 317 or duplex.

 

[iam42]

Thanks Stanweld,

Could you or someone else elaborate on why 309/309L is not so good at the higher temps?

Thanks

 

[wegm]

iam42,
As stanweld told 309/309L is not so good at the higher temps due to thermal expansion coefficient mismatch issues. In other words in high temperatures the CS and the SS will not have equal expansion and thus induced stresses will be produced. Such stresses may give cracking in the weldment. Please note that the nickel filler metals give welds that have thermal expansion coefficient between stainless steel and carbon steel. Please have a look at this post:

http://www.weldinguide.com/gdanastasiadis/viewtopic.php?f=5&t=32

that cllarifies such an issue
regards
wegm

 

[Rich2001]

Check the EPRI site. I don't remember the report number but there is report on dissimilar metal weld joints, and filler metals,

http://www.epri.com/Pages/Default.aspx

Richard

 

[XL83NL]

Someone knows that EPRI report#? Been trying to find it, but there are too many reports on this subject ...

 

[stanweld]

The 309 intensifies the coefficient mismatch at the fusion line of the least ductile (carbon steel) material, resulting in high shear loads thereon and greater potential for failure, especially in cyclic service. The greater expansion mismatch, if possible, should be at the more ductile (austenitic stainless steel) side of the joint.

 

[iam42]

Thanks for all the help guys. Greatly appreciated.

Ian

 

[metengr]

Very simply put, 309 stainless steel filler metal promotes carbon migration from diffusion (pick-up) resulting in loss of carbon along the ferritic side of the DMW joint. This is why nickel-base filler metals are typically used in elevated temperature DMW joints. The diffusivity of carbon is lower in nickel-base alloys exposed to elevated temperature (>700 deg F) service.

 

[XL83NL]

Someone knows that EPRI report#? Interested in it...

 

[iam42]

Metengr,

Is there a similar problem when PWHT'ing a dissimilar joint between carbon steel and stainless steel using 309 as the filler. The time at the elevated temp may only be 1 to 2hrs.

thanks

 

[metengr]

Diffusion is an activation energy controlled mechanism, meaning the effects of time at temperature control the rate. For PWHT the temperature is well above 700 deg F, so there will be some carbide precipitation along the fusion line.

 

[metengr]

XL83NL;
Development of a New Nickel Filler
for Dissimilar Metal Welds and
Repair
1018991
Final Report, July 2009

 

[metengr]

Here is the most recent report by EPRI

Repair Methods for Dissimilar
Metal Welds—Development,
Weldability, and Properties of
EPRI P87 Solid Wire Filler Metal

1019786

http://www.epri.com

Final Report, December 2011

 

[XL83NL]

Thanks metengr, found both of em

 

[iam42]

Metengr,

Thanks so much for your help.

 

[21121956]

Hello everybody:

I really beg your pardon but, the OP never mentioned that the application would be at high temperature, it was only said "welding CS to SS". So, it can be inferred that, for a "not high temperature application" (< 700°F) the filler 309 can be used?

El que no puede andar, se sienta.

 

[weldstan]

21121956
The OP's question was to understand why ERNiCrMo-3 is specified. I believe that question has been answered; however, I have not seen ER/ENiCrMo-3 being mandated for use with austenitic stainless steel to carbon steel welds regardless of operating temperature conditions. We normally see Owner requirements for ERNiCr-3 and similar ENiCrFe-X weld filler metals for these joints when operating temperatures dictate. For lower tempearture applications and those applications that do not require PWHT, ER/E309 is most commonly specified.

 

[iam42]

Thanks for your reply Weldstan.

I should have stated that my question was in regards to operating temps >600F.

Thanks