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.srini@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
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