P5A to P5B welded with ER90S B3

[90harley]

Can anyone explain in detail the pros and cons of welding and P5A to P5B joint with ER90S B3? I know the age old thought is to weld this joint with ER90S B9 but I think engineering studies has proven that the B3 wire works more efficiently.

 

[metengr]

90harley;
There are no pros and cons for this approach because the filler metal meets or exceeds the strength of the weaker of the two materials being joined. For your application you have a dissimilar metal weld (DMW) joint with a higher chrome being joined to a lesser chrome material. The filler metal matches the strength of the lesser chrome material - there are no problems provided the DMW joint is properly designed for the intended service conditions.

 

[DVWE]

B9 is a Grade 91 compatible electrode, and Grade 91 alloys are no longer P5B materials (now P15E). I believe even the B3 will also meet yield strength requirements of the higher alloys.

 

[stanweld]

If you make the dissimilar weld using "B3" filler, lowering the PWHT temperature is recommended to mitigate carbon migration from the deposited weld metal to the P91 base material. Possibly the best method to make these welds is to use a "stabilized" (vanadium/niobium bearing) T23 or T24 type weld filler.