Welding SA-350 LF2Cl1 to SA-516 Gr 70N

[tonnesen]

Hello,

We are going to weld a SA-350 LF2Cl1 nozzle neck to a SA-516 gr 70N head. As I never worked with forgings, I was reading the SA-350 and found that the piece will be normalized and tempered or quenched and tempered, based on this I would like to know if after welding the nozzle neck to the head I will have to PWHT in a temperature just below the original tempering temperature of the nozzle neck (like in quenched and tempered materials), in order to re-temper it after welding or if this PWHT is only determined by UCS-56/UW-40 requirements.

Thank you all.

 

[metengr]

PWHT is determined by Section VIII, Div 1 fabrication rules. The PWHT temperature range for materials approved for use by Section II, Part D for Section VIII, Div 1 applications have minimum tempering performed by material specification at or above stated minimum PWHT temperature.

 

[tonnesen]

metengr,

thank you for your answer, so the nozzle neck manufactor should heat treat the component in accordance with the requirements of SA-350, and I (the vessel manufacturer) should determine the need for PWHT by ASME Section VIII div 1, correct?

I read the paragraph UF-31(2) that says:

(2) Vessels fabricated by welding of forged parts
requiring heat treatment shall be heat treated in accordance
with the applicable material specification as follows:
(a) after all welding is completed; or
(b) prior to welding, followed by postweld heat
treatment of the finished weld in accordance with UW-40;
(c) when the welding involves only minor nonpressure
attachments to vessels having carbon content
exceeding 0.35% but not exceeding 0.50% by ladle analysis,
requirements of UF-32(b) shall govern.

So I would like to know if the PWHT is only for stress relief or if it is for restore the material properties.

 

[metengr]

tonnesen;

I (the vessel manufacturer) should determine the need for PWHT by ASME Section VIII div 1, correct?

Correct to your item 1.

So I would like to know if the PWHT is only for stress relief or if it is for restore the material properties.

In reference to ASME Section VIII, Div 1 there are two options during fabrication regarding heat treatment. You can perform heat treatment of the entire component to the required material specification, after fabrication, which will take the material back to original properties per the material specification. Or you can perform a subcritical heat treatment - PWHT on material that has been initially heat treated per the material specification. The function of a subcritical PWHT is to reduce residual stresses from welding and to locally temper the base metal heat affected zone and the weld metal. A subcritical PWHT only affects the welded regions and not bulk properties.

 

[stanweld]

tonnesen,
When applicable per UCS-85, the vessel Manufacturer must provide heat treatments that the materials will experience to the material supplier that wiil define the heat treatment requirements of the test specimens supporting that material beyond the requiremnts of the material specification.

 

[tonnesen]

metengr,

thank you for the help!

stanweld,

Do I need to do this even if I apply a localized PWHT?

 

[stanweld]

Yes, unless the exemptions listed in UCS-85 apply