[MW:9659] RE: 9652] QW 405.2 conflicts?

You have not read the complete sentence. The complete sentence reads:
"This variable does not apply when a WPS is qualified with a PWHT above
the upper transformation temperature or when an austenitic material is
solution annealed after welding."

If you normalize a ferritic material & weld after completion of the
weld; i.e. PWHT above the upper transformation temperature, the ferritic
grain structure will transform to austenite upon heating and form new
ferritic grain structure upon cooling. This phase change and
development of new microstructures essentially removes any
microstructural evidence of the weld metal or heat affected zones. Since
the original weld metal and heat affect zone microstructures are
eliminated, the difference in heat input upon the development of the
microstructures between vertical up {high heat input} and vertical down
{low heat input} have no effect on impact properties.

Please note that most PWHT is performed "sub-critical" or below the
lower transformation temperature; i.e. there is no
ferrite-to-austenite-to-ferrite transformations. While the
microstructure may change in some ways, the coarse grained heat affected
will still be present and the weld metal will still have the appearance
of "as-cast" material. Therefore the difference in heat input will
result in significant differences in microstructure and have very
different effects on impact properties.

Although austenitic materials do not experience phase changes, when
solution annealed the carbide structures and locations will be changed
from that present in the weld and heat affected zone. The elimination
of carbides formed or modified by welding will eliminate the effect on
impact properties {remove "sensitization" effects}.

Hope this helps.

John

-----Original Message-----
From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com] On Behalf Of Srinivas Engr
Sent: Tuesday, February 01, 2011 6:23 AM
To: Materials & Welding
Subject: [MW:9652] QW 405.2 conflicts?

Dear All

QW 250 WPS, 405.2 it is given in supplementary essential variable.
Once if toughness is required by code then only we have to go for
Supplementary variable.
If we refer 405.2 welding variables.. It say once if qualified with
PWHT it doesnt apply.
But as per QW 250 we have to take 405.2 for WPS wit PWHT.
Pl explain about tis.

Thanks
Srinivas.

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