Christy,
I did a quick search of an interpretation data base provided by our AI company. I found no interpretations regarding selection of filler metals for dissimilar metal welds. This is as I would expect. The Code has never, as far as I know, dictated the filler metal to be employed. The filler metal is selected based on design requirements and engineering knowlege. For welding ferritc materials, there are often advantages to using the filler metal with the lowest strength. One advantage is that shrinkage strains are accomodated in the more ductile carbon steel filler metal and therefore results in having lower residual stresses/strain on the coarse grained heat affected zone in the P22 material. This can reduce the tendency to hydrogen assisted cracking and reheat cracking.
One side comment, for this couple you need to be careful with PWHT depending on the particular ASME Code you are using as there may be a very small range for the soak temperature. Most PWHT is subcritical (below the lower transformation temperature) for the base metals - for carbon steel that is 1333F (723C) - equilibrium or 1340F (727C) if you use the table from B31.1. and most of the B31.X Codes require a minimum of 1300F (704C).
John
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Christy
Sent: Monday, July 20, 2009 3:39 AM
To: materials-welding@googlegroups.com
Subject: [MW:2727] Dissimilar Weld
Hello Friends,
We have an PQR for Dissimiar welding the material P1 TO P22. The filler wire is used ER70S-2.
In the ASME Interpretations is given we can use the lower side material filler wire. But i could not able to locate it is in which section.
If anybody knows please let me know the section.
Regards,
Christy
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