Tuesday, September 14, 2010

Re: [MW:7008] Ferrite and its properties

Do not mix up the .concept of Ferrite in SS and duplex
Ferrite in SS is of delta ferrite and not the ferrite which is of Duplex steel both are having different caracterestic
Regards
Hegde P B

Sent from my BlackBerry® smartphone from !DEA


From: saroj kumar <sarojselva@gmail.com>
Sender: materials-welding@googlegroups.com
Date: Tue, 14 Sep 2010 14:56:16 +0300
To: <materials-welding@googlegroups.com>
ReplyTo: materials-welding@googlegroups.com
Subject: Re: [MW:6998] Ferrite and its properties

Dear Karthik and All,

Many thanks for your kind explanation regarding Ferrite subject. Here i would like to have some more clarifications from your end.

1. Which alloying elements are inducing the formation of Ferrite in SS/Duplex SS, whether Cr or Ni or any other?.

2. The unit of measurement of ferrite content is by Volume or Weight?. What is the unit?.
   
3. Like ferrite number, are there any terms like Austenitic number or Martensitic number
   available?.

4. I came to know that Ferrite content is very very important for achieving the low temperature    toughness. Is it correct?. If yes means, what are the other important properties imparted by Ferrite Content, other than Solidification cracking resistance?.

5. Can we say, if FN is 8, then balance volume/weight is fully occupied by Austenite in Austenitic SS or Duplex SS?. 

6. Is there any relation between Welding process/Welding Parameters and Ferrite Number?.

Advanced thanks for your support and co-operation. Looking forward the good things always.

Best regards,

M.SarojKumar
Sales Manager-Bohler welding group products,
Alruqee Industrial Marketing Co Ltd.
Saudi Arabia.

On Mon, Sep 13, 2010 at 1:41 PM, Karthik <karthik6684@yahoo.com> wrote:
Hi,
You have asked a big and number of questions in single post.
Anyhow Please find below my answers with my own as well as extracted from useful datas.
 
01. What is meant by ferrite?
Ferrite is a primary solid solution based on alpha iron having body centered cubic (B CC) structure.
It is the interstitial solid solution of carbon in iron.
It is soft, ductile and highly magnetic.
It can undergo extensive cold working.
Carbon solubility is 0.025% at 723 C and at room temperature it is only 0.008%.
What is ferrite number?
Ferrite number is a measure of = Chromium & Nickel equivalent in an Austenitic stainless steel material. It should be between 3-7% max. Very low ferrite can lead to cracks. It is a measure of denoting the ferrite content in an stainless steel. Ferrite Number has been adopted as a relative measure for quantifying ferritic content using standardized magnetic techniques. The Ferrite Number approach was developed in order to reduce the large variation in ferrite levels determined on a given specimen when measured using different techniques in different labratories.
The ferrite level is only important to assure minimum exposure to solidification cracking when depositing austenitic stainless steel weld metal. The lower ferrite number is better for corrosion resistance, while balancing higher ferrite content to avoid solidification cracking in the weld deposit. I would not worry about lower ferrite numbers for clad overlay welding, if no cracking is observed (Liquid Penetrant verification).
02. What is ferrite percentage?
Ferrite percentage no longer used,it has been replaced by Ferrite Number (FN).
FN has been adopted as a relative measure for quantifying ferritic content using standardized magnetic techniques. The FN approach was developed in order to reduce the large variation in ferrite levels determined on a given specimen when measured using different techniques in different laboratories. FN approximates the "volume percent ferrite" at levels below 8 FN; above this level, deviation occurs.

03. What is the difference between ferrite number and ferrite percentage?
Ferrite percentage no longer used,it has been replaced by Ferrite Number
Ferrite Number is an arbitrary standardized value designating the ferrite content of an austenitic stainless steel weld metal. It should be used in place of percent ferrite or volume percent ferrite on a direct replacement basis.

FN has been adopted as a relative measure for quantifying ferritic content using standardized magnetic techniques. The FN approach was developed in order to reduce the large variation in ferrite levels determined on a given specimen when measured using different techniques in different laboratories. FN approximates the "volume percent ferrite" at levels below 8 FN; above this level, deviation occurs.
A number of instruments are commercially available for determining the ferrite content of welds, including the Magne gage, Severn gage, and ferrite scope.

04. What would happen if weld metal having more ferrite?
ferrite is that over 10% is extraneous for hot cracking prevention and leads to other problems in mechanical properties through the formation of undesirable phases at 375C and above.

05. What would happen if weld metal having less or no ferrite?
Very low ferrite can lead to cracks

06. How we can control the ferrite?
Treating the high FN welds with a wash using the Tig arc, but no wire after the weld is completed, acts like a heat treatment and gets the FN16 down to about FN7-8.

07. Is it present in non ferrous materials?
Yes.Some non ferrous metal have ferrite content ..like Zinc.But it can be seperated by Ferrite seperator
08. What is the optimum ferrite value required in CS,LTCS,SS and SDSS?
The ferrite level is only important to assure minimum exposure to solidification cracking when depositing austenitic stainless steel weld metal

09. What are all the parameters affecting ferrite content in the weld?
Weld Cooling Rate may affect the ferrite content
 
Thanks & Regards,
 
(Karthik)

Karthikeyan.S
QA/QC Manager
Getabec Energy Co.,Ltd.
379,Moo6,Soi8,Nikhomphatana,
Rayong-21180,
Thailand.
Phone: 0066 38 897035-8 (Off)
Fax: 0066 38 897034
Hand Phone: 0066 892512282


--- On Mon, 9/13/10, limesh M <limesh78@gmail.com> wrote:

From: limesh M <limesh78@gmail.com>
Subject: [MW:6975] Ferrite and its properties
To: "Materials & Welding" <materials-welding@googlegroups.com>
Date: Monday, September 13, 2010, 12:41 PM


Dear All

What is meant by ferrite?

What is ferrite number?

What is ferrite percentage?

What is the difference between ferrite number and ferrite percentage?

What would happen if weld metal having more ferrite?

What would happen if weld metal having less or no ferrite?

How we can control the ferrite?

Is it present in non ferrous materials?

What is the optimum ferrite value required in CS,LTCS,SS and SDSS?

What are all the parameters affecting ferrite content in the weld?


Thanks in advance

Regards,

Limesh

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