Did you check the Nitrogen % in the base material ? How much is it?
If the material is dual certified, I think the minimum N% should be 0.18%, anything less than this you'll be landing up with higher ferrite in the HAZ, if you have these values in your material TC, then i think u can control it by your process.
may be 80 degree centigrade interpass temperature that you maintain on a higher thick material (32mm) can really retain higher ferrite % than normally expected in a lower thick material.
You can start to weld once the temperature reaches 100 deg.C, this will to some extent control the cooling rate and allow some austenite to form.
Regards,
Praveen
--- On Wed, 12/22/10, Srini <sethu.srini@gmail.com> wrote:
> From: Srini <sethu.srini@gmail.com>
> Subject: [MW:8886] Re: Duplex S.S - How to reduce ferrite content in HAZ
> To: "Materials & Welding" <materials-welding@googlegroups.com>
> Date: Wednesday, December 22, 2010, 9:43 PM
> Yes. i am proceeding with G48A to
> asertain pitting resistance.
> However, is there any thing more i can do to fine tune the
> process
> itself to get the ferrite in HAZ down?
>
> Thanks
> Srini
>
> On Dec 22, 3:16 am, p_chavda...@mail.bg
> wrote:
> > Dear Mr. Srini,
> >
> > Two things:
> >
> > 1. According to me it is strange that you have
> measured so high ferrite
> > content, taking into consideration the weld method and
> the obtained heat
> > input. Are you sure that the ferrite content in the
> HAZ 71% is.
> >
> > 2. From what I am reading I am not convinced that
> there is no loss in the
> > resistance to pitting corrosion. ASTM C is a good
> procedure in terms of
> > determining the loss in the resistance because of
> precipitation of
> > intermetallic phases, but not in general. Take into
> account, that sometimes
> > even when there are no intermetallic phases, pitting
> corrosion could appear
> > because of local depletion of Cr, Mo or N, i.e.
> locally the PREn is less
> > than required. By such high ferrite content, you could
> expect at least
> > precipitation of Cr2N (there is no enough austenite to
> dissolve the
> > nitrogen), so I suggest you to perform additionally
> the G 48 test in order
> > to ascertain that there is no loss.
> >
> > Regards
> >
> > Parvan Chavdarov
> >
> > ----- Цитат от Srini (sethu.sr...@gmail.com),
> на 21.12.2010 в
> > 21:44 ----- Can you please advice some thoughts how
> to reduce ferrite in
> > HAZ and
> > bring into range of 60% max. This is an weld procedure
> development and
> > ferrite was as high as 71% (E562 - Metallography
> method) in HAZ.
> > Ferrite in parent metal 50%, ferrite in weld metal was
> 50 to 55%. The
> > details of the processa are as below.
> >
> > Material Dual S32205/S31803. Thickness 1.25" (32mm).
> Process- SAW.
> > Double butt joint. Parameters 450A/30V/20". Heat input
> was 42Kj/inch.
> > After each pass i let the part cool naturally to about
> 80° and then
> > welded the next pass. i continued the same to keep the
> cooling rates
> > consistent. May be i have put too much control and
> resulted in faster
> > cooling rate and hence high ferrite in HAZ.
> > No intermetallic phases found. ASTM 923 C - no
> corrosion loss, but the
> > customer would not accept 71% ferrite in HAZ. has to
> be less than 60%
> > to avoid pitting corrosion.
> >
> > Thanks for any help in advance.
> >
> > --
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> >
> > -------------------------------------
> >
> > P.S. Само да ти кажа - Коледа
> идва с 30% Хостинг Отстъпка
> > и Безплатен Домейн като
> подарък
> > http://www.icn.bg/default.icn?show=about&status=about-news&news=158
>
> --
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> personel views and meant for educational purposes only,
> Users must take their own decisions w.r.t. applicable
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>
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