A487 CA6NM to 9Cr PWHT temp?

[runda]

Hi, I would like to know what would be the best PWHT temperature for a weld of A487 CA6NM with a 9Cr carbon steel.
I understand that the PWHT temp for the CA6NM is about 1150F and for the 9Cr is about 1350F

Thanks for your help

R

 

[metengr]

What is your application for this combination of base materials? Service conditions? Is the 9Cr a 9Cr-1Mo alloy steel? Are you intending to qualify a weld procedure?

 

[runda]

metengr,
we are going to weld a nozzle (9cr-1Mo)to a pump case (CA6NM) running at a temperarture of about 700F. No welding procedure qualification is required.

Thanks

 

[metengr]

Are you familiar with welding CA-6NM and 9Cr-1Mo materials? I would presume that the nozzle be fillet welded to the CA-6NM pump case. You did not mention the thickness of the pump case or the size of the nozzle.

What I would do is to butter the entire weld prep end of the 9Cr-1Mo nozzle and perform a separate PWHT before you weld it to the CA-6NM pump casing. Use preheat for buttering to the 9Cr-1Mo base material. The butter layer should be 1/4" thick to assure that welding the nozzle to the pump case will not affect the Cr-Mo base material. The filler metal should be 410NiMo for buttering. This is a low carbon martensitic stainless steel filler metal that would be compatible with Cr-Mo and CA-6NM.

After you buttered the nozzle, weld it to the CA-6NM pump casing using the same filler metal with no preheat. Once this operation is completed, perform a local post weld heat treatment of the nozzle attachment weld at 1150 deg F for 1 hr/inch of weld deposit thickness (not base metal thickness of the pump case).

I would still insist on qualifying a weld procedure before you perform this work. I would also perform a wet fluorescent MT after the nozzle is welded to the pump case.