[MW:9393] RE: 9389] RE: 9372] AC welding for P5A & P5C

Hi Bhavesh,

Is your SAW wire flux combinations based on the Japanese Supplier(Kobelco)? Traditionally Alternating Current power sources had been very popular with Japanese, I would say the concept originated with them. I'm talking about mid 1980's since when I started working.The advantages of AC being:-

Cheaper power sources , AC. power sources would not require the rectification to convert to DC.
Accordingly fluxes were formulated to suit AC.
Moderate/Controlled penetration as compared to DC.The penetration characteristics are DC(+ve) most, DC(-ve) least, AC in between.This(penetration) controls base metal dilution and heat input and accordingly notch toughness may be better. However notch toughness property is not controlled by the power source type alone e.g A.C or D.C, because welding wire flux also have big role to play here.
If the welding process is Tandem Sub Arc, then the trail arc is usually AC, to prevent Arc Blow.
AC/AC tandem arc is also quite common with Japanese fabricators

The materials you mentioned are used a lot in the refining industry.For hydro processing applications there're strict control on residuals and impurities. Some consumable manufacturers formulate wire flux combinations only for AC power sources, while others could meet such requirements with DC also.

The end result is that both DC and AC are feasible options for welding of those steels. The choice of AC over DC could be influenced by the welding consumable manufacturers' recommendations also.

Thanks.

Pradip Goswami,P.Eng.
Welding & Metallurgical Specialist & Consultant
Email-pgoswami@sympatico.ca,
pgoswami@quickclic.net

-----Original Message-----
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of amitabha.bhattacharya
Sent: Friday, January 21, 2011 7:04 AM
To: materials-welding@googlegroups.com
Subject: [MW:9389] RE: 9372] AC welding for P5A & P5C

Hi Bhavesh,
You may expect higher toughness values with AC welding for CrMo-steels.
Thanks
Amitabha

-----Original Message-----
From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com] On Behalf Of JIGO
Sent: Friday, January 21, 2011 2:55 PM
To: Materials & Welding
Subject: [MW:9372] AC welding for P5A & P5C

Dear All,

Why we are using AC current for SAW welding in low alloy steel (Mainly for P5A & P5C) ?

Kindly share your valuable input.

Regards,
Bhavesh Patel
ISGEC, Dahej

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