RE: [MW:17901] Ferrite number verification

[prave...@yahoo.com]

Hi Binu, The easiest way to prove it will be to weld a few samples internally using the same batch of E347si electrode using slightly longer arc length (not too long such that it will cause porosity). Longer arc length will try to suck little more atmospheric air than the normal arc length does. Due to the fact that more than 78% of the air is Nitrogen, and the more nitrogen is absorbed into the arc column, this will stabilize more austenite thus reducing the level of ferrite. Of course you'll not be getting a big difference in the ferrite values but surely less than 10 FN, try it yourselves before you demonstrate to your client. Regards, Praveen Alavandar Sent from Yahoo! Mail for iPad

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From: Binu Nair <binugn...@gmail.com>;
To: <material...@googlegroups.com>;
Subject: [MW:17901] Ferrite number verification
Sent: Sun, Jun 9, 2013 7:03:18 AM

Dear Experts,   Recently we faced a problem regarding the ferrite number of Electrode E 347Si. In the MTC FN is shown as 10. The client specification shows the range of FN shall be 3-10. So the client has written a comment to ensure the ferrite content should be less than 10 while welding. Now they are insisting to prove it before using the particular lot of electrode. Is there any way to prove that? Please send your valuable suggestions with code reference.   -- To post to this group, send email to material...@googlegroups.com To unsubscribe from this group, send email to materials-weld...@googlegroups.com For more options, visit this group's bolg at http://materials-welding.blogspot.com/ http://www.linkedin.com/groups/MaterialsWelding-122787?home=&gid=122787&trk=anet_ug_hm   The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents. --- You received this message because you are subscribed to the Google Groups "Materials & Welding" group. To unsubscribe from this group and stop receiving emails from it, send an email to materials-weld...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.

[c sridhar]

Mr. Binu Nair,

To understand the Ferrite  control, one has to know reason for ferrite formation. Welding metals like

304L, 316L,347Si, retain some amount of delta ferrite formed at grain boundaries, due to composition

of weld metal & welding conditions like high temperature (550⁰ - 950⁰C). Both factors determine the

percentage of delta ferrite as well as its size, morphology and distribution. Though delta ferrite reduces

risk of micro fissuring / cracks, if it exceeds 8-10%, corrosion resistance of SS decreases steeply. Ferrite

level beyond 7% is unacceptable for high temperature service. Again, Zero or very low ferrite may

create micro-fissures. Ferrite turns to brittle sigma phase (rich in Cr)  at high temperature and affects

ductility, toughness and also cause  inter granular corrosion due to Cr depletion from austenite matrix.

Hence it has to be maintained depending up on service requirements.

While welding, control your inter pass temperature by using minimum amperage as recommended by the

manufacturer and stop the welding if the heat input goes beyond the acceptable values.

 

Ferrite scope, Magna & Severn gauges are other methods, to measure the delta ferrite and their are said to be

accurate and widely used due to its simplicity.  All  gauges are available easily in the market.

Sridhar.

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From: Binu Nair <binugn...@gmail.com>
To: material...@googlegroups.co

Sent: Sunday, 9 June 2013 12:33 PM

Subject: [MW:17901] Ferrite number verification