I agree fully with Sanjay that it is not advisable to execute PWHT on
QT materials in order to avoid changes in materials microstrucre by
which it's loosen the original mechanical properties.
Most manufactures have datasheet available which give recommandations
and/or guidelines for welding such materials, I would advise to take a
look at the website of your supplier to see if you can find this
information, if not than take a look at the site of SSAB Sweden
(S690QL is similar to Weldox 700) and see what they advise for welding
these materials.
Always use heat imput as low as possible for same reason as why
omitting PWHT, especially in case where fatigue also can become a
problem.
Best Regards,
Herman Pieper
On 3 apr, 16:17, Erhan Turgut <ertur...@gmail.com> wrote:
> Hi,
> We're working on 2700 mm dia. pipes with a thickness range of 26 - 40 mm
> for S500QL and 30 - 48 mm for S690QL.
> These penstocks will be used in hydro power plant with a pressure of
> aprx. 140 bar
> We have two methods for welding: SAW on GTAW (root GTAW, fill & cap SAW)
> and SMAW on GTAW. We will try to achieve max. 12 kJ/cm heat input.
> So shall we apply PWHT (Stress relief)? If yes what is the thickness
> limits for PWHT.
> We planned to apply Soaking (Hydrogen Releasing) with a temperature of
> aprx 250 oC for 2.5 - 3 hours. So if we apply Stress relief
> heat-treatment with a temp. of 550 oC for 1 hour do we have to apply
> soaking anyway?
>
> Thanks in advance
> Regards,
>
> Erhan TURGUT
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