Dr Ganeshan,
The role of "Si" in austenitic S.S weld metal is to improve wetting and flow of weld puddle, other than increasing high temperature oxidation and carburization resistance. As per ASME Sec-II ,Part-C, the "Si" content allowed in undiluted weld metal for matching S.S 321 & 347 are :-
· Bare wire GMAW- 0.65-1.00 (SFA- 5.9)
· Bare wire GTAW- 0.30- 0.65 (SFA- 5.9)
· Covered Electrode, SMAW- 1.00(SFA-5.4)
The major problem which filer metals with "Si" lower than AWS specifications:-
· Poor wetting -- would call for wider groove /access angle, and more electrode manipulation for manual welding. For automatic welding slower weaving speed and more dwell perhaps would be necessary. One has to work out the best welding parameters after a few trials and errors.
· Welds could be less tolerant to porosity:- Hence joint cleanliness would be a must, also the interpass cleanliness has to be very good.
It may a good idea to stay within the ASME range, unless there are issues with Ferrite No. This is so as Si has good effect on Cr equivalent on Delong Diagram.
Thanks.
Pradip Goswami,P.Eng
Senior Engineer/Specialist(Welding-Metallurgy)
Machine Dynamics & Component Integrity Dept.
Engineering & Training Services Division
ONTARIO POWER GENERATION Inc.
PO Box-2000, RR-55(South)
Nanticoke, Ontario,N0A1L0
Tel:-(519) 587-2201, Ext 3107--in Nanticoke
(416) 231-4111, Ext 5925--in Kipling,Toronto
Fax: (519) 587-6814
-----Original Message-----
From: pgoswami@sympatico.ca [mailto:pgoswami@sympatico.ca]
Sent: Thursday, January 07, 2010 11:54 AM
To: GOSWAMI Pradip -THERMAL
Subject: FW: [MW:3980] Role of 'Si'- welding
> From: vaidehi@igcar.gov.in
> To: materials-welding@googlegroups.com
> CC: vaidehi.ganesan@gmail.com
> Subject: [MW:3980] Role of 'Si'- welding
> Date: Thu, 7 Jan 2010 13:26:56 +0530
>
> Dear Moderator of the group,
> Pl arrange to post the following:
> Thank you,
> Best Regards,
> Vaidehi Ganesan.
> -----------------------------------------------------------------------------------------------------------------------------------------
> Dear Group members,
> Kindly give feed back based on your experience for the following:
>
> We all know the presence of "Si" helps during welding of austenitic stainless-steels. What is the minimum "Si" required to weld 15Cr-15 Ni, Ti stabilized austenitic stainless -steels (End-cap welding for Nuclear application). One of the suggestions is minimum 0.5 % Si required for good welding. Suppose to safe guard the other properties of the material (seamless tube), if we reduce 'Si' to < 0.3 % (approx 0.28% Si), then, what are the precautions to be taken regarding welding, electrodes, procedures etc to achieve good welding? Experts can send their opinion regarding,
> whether with 0.28 % Si in 15 Cr-15 Ni, Ti stabilized austenitic stainless-steels, any welding problems can be anticipated? Pl mark a copy of your response to my gmail i.d also.
>
> Thank you in advance,
> Best Regards,
> Vaidehi Ganesan.
> --------------------------------------------------------------------------------
> Dr. Vaidehi Ganesan
> Metallurgy & Materials Group,
> IGCAR, Kalpakkam-603 102, India.
> =====================================================================
>
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