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 Ferrite percentage no longer used,it has been replaced by Ferrite Number (FN).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 Ferrite percentage no longer used,it has been replaced by Ferrite Number Ferrite Number is an arbitrary standardized value designating the ferrite content of an austenitic stainless steel weld metal.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:
|
--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
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.
Comments