Welding Chrome Moly to P1 material 1

[PressuresOn]

Good morning,

We are currently reviewing the welidng for a client contract that involves welding the following material combinations together;

a) P1 material (ASTM A516 GR 70) to P4 material (ASTM A387 Grade 12) Class 2
b) P4 material to P4 material

The P4 materials are being used as a liner that is not welded to a pressure bearing surface. There is equivalent pressure both sides of the liner and as such the welds are not pressure bearing.

My question simply revolves around preheat and heat treatment. If none of the welds are pressure bearing or contact a pressure bearing part of the vessel then is there any need to preheat or heat treat the welds afterwards.

The choice of p4 material is based on its corrosion and wear properties in liner service - the unit design temperature being 200 degrees C and thus not high temp service (which is what the usual criteria is for selecting these materials in the first place).

Any assistance you could offer would be greatly appreciated.

Thank you

 

[Kiwi2671]

Pressureson,
No welding, whether it is on pressure parts or not should be performed without a qualified WPS.
The WPS will dictate whether a pre heat or PWHT is required - not an engineering forum,
Regards,
Kiwi

 

[PressuresOn]

Kiwi,

Thank you for your reply.

The question is not about whether or not we use a WPS. The question is about members experience of the mettalurgical effects of not performing PWHT. This is a grey code area and that is why I am seeking input from others who may have experience when working with these grades.

If I need any advice on how to keep our ASME U Stamp or EN welding systems up to date I will contact you for some of your sound advice.

 

[metengr]

For the above, I would strongly recommend you follow preheat guidance that is applicable ot the Code book section (I or VIII). For P-No 4 base material I would use a minimum preheat of 250 deg F. Second, regarding PWHT, I would use the limit of 5/8" or greater in thickness for PWHT regardless if it is for non-pressure parts.

 

[jtseng123]

Good question and I have faced this many times, and for sure many answers.
On the safe side even it is non pressure parts, your question (b), just follow the code for preheat and PWHT to reduce residual stress, as metengr advises.
For (a), the PWHT temp for P4 will deterioate P1 materail. What we do is, preheat P4 part and weld a butter layer, then PWHT P4 part with this butter layer. After that, weld P1 part to the butter layer like P1 to P1 welding.

 

[Kiwi2671]

PressuresOn,
I was not trying to be a smarts#ss.
Your question appears to ask do you require preheat or PWHT for non pressure parts.
Your applicable code will mandate this.
Eg. B31.1 requires 250 F for P4 as metengr noted for all materials, no mention of not doing it for attachment or non pressure parts.

"My question simply revolves around preheat and heat treatment. If none of the welds are pressure bearing or contact a pressure bearing part of the vessel then is there any need to preheat or heat treat the welds afterwards"

Regards,
Kiwi

 

[PressuresOn]

Hi folks,

Thank you all for the advice.

I think the answers generally told me what I already suspected and offered some good advice - especially in the areas not covered by the codes relating to non-pressurised welds.

In response to JTSeng123, we intend to perform a PWHT at 600 deg C for a longer period to effectively mimic a P! test at 650 Deg C. This is agreeable to us, the client and the AI as we are performing PWHT for non-code welds.

Thank you all for your suggestions and input.