Tuesday, January 11, 2011

[MW:9185] Re: MW:8886- Duplex S.S - How to reduce ferrite content in HAZ

Further to all your valuable suggestions i just wanted to update the
changes i did and the results. I did increase the heat input to 46Kj/
inch and increased the interpass to 115°C. Additionally i slow cooled
with ceramic fibre inbetween interpass cooling. The ferrite results
obtained in HAZ averaged from 55 to 65% by point count method.

Again thanks for all your inputs.
Srini

On Dec 22 2010, 10:19 pm, "pgoswami" <pgosw...@quickclic.net> wrote:
> Mr. Srini,
>
> I highlighted some text on the attachment, which I'm sure would be of great
> interest to you. As the issue is with HAZ I would think the prime
> cause/causes are heat input vs. cooling rate.
>
> The heat input in the PQR is 42Kj/Inch or 1.7Kj/mm, which is slightly on the
> higher side, may not a lot. However  a strict interpass of 80 deg C means
> the cooling rate high which is not allowing the ferrite to transform into
> austenite.Note Duplex S.S will have high temperature  ferrite phase (see the
> arrow in page -2) , the primary mode of solidification is ferrite and the
> cooling rate throughout the transformation zone controls the ferrite :
> austenite ratio.
>
> I would think at the above heat input rate if  the interpass temperature is
> controlled between 100-125 deg Max, you'll be able to get around 55-65%
> ferrite in the HAZ.You may check the proper chemistry of the BM and welding
> consumable, the required level of Nitrogen in addition to Cr,Ni and Mo would
> help to balance the phases(ferrite and austenite).
>
> Thanks.
>
> Pradip Goswami,P.Eng.,IWE.
> Welding & Metallurgical Specialist & Consultant
> Email-pgosw...@sympatico.ca,
> pgosw...@quickclic.net
>
>
>
> -----Original Message-----
> From: materials-welding@googlegroups.com
>
> [mailto:materials-welding@googlegroups.com] On Behalf Of Srini
> Sent: Wednesday, December 22, 2010 11:13 AM
> To: Materials & Welding
> Subject: [MW:8886] Re: Duplex S.S - How to reduce ferrite content in HAZ
>
> 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
> <http://www.icn.bg/default.icn?show=about&status=about-news&news=158>
> &status=about-news&news=158
>
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>
>
>
>  W-45Nplus.pdf
> 307KViewDownload- Hide quoted text -
>
> - Show quoted text -

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