Hello Srinivascvv, sorry to have picked up on this somewhat late. There is a company located in Albany, Ore. they are called ATI Wah Chang. I believe that you can google them and locate their contact information and likely also pose this question to their technical staff. I recently returned from a 1-day seminar there and one of the things that they stressed was matching the proper filler for the particular grade of Ti. I believe they also told us that there are 28 different grades of Titanium that they produce and each one of them has a specific filler material that should be used when welding them. They are a great group of folks and I believe if you contact them they will be more than willing to help you with your question and any others you may have. Good luck and best regards, aevald

This advice comes from one of the world's largest producers of Titanium, TIMET...

"It is generally good practice to select a filler metal matching the properties and composition of the titanium base metal grade. However, for both commercially pure grades and alloys, selecting a weld wire one strength level below the base metal is also done. Special situations may require a different grade of filler wire to give desired combination of joint properties. For instance, several options are available for use with Ti-6Al-4V-ELI (Extra Low Interstitials) otherwise known as: ERTi-6Al-4V-1. The low interstitial grade is useful where high weld ductility, such as is required in cryogenic applications, is needed."

I noticed that there can potentially be a problem or two with using a filler metal such as ERTi-6Al-4V to weld CP (Commercially Pure) grade 2 Ti together
Although there may or may not be a slight concern for microsegregation if one introduces an alpha/beta filler to join Commercially pure Ti such as grade 2 Ti. due to uncontrolled dilution via excessive heat input. I guess it mostly depends on the application, and any special considerations regarding the intended service conditions to give the appropriate recommendation in response to your query so, much more information needs to be addressed, and taken into consideration before one can give the proper answer to your application. In other words... Filler metals shall be selected based on specific base metals being welded, service conditions, design requirements (load conditions, etc.), and other design or service factors. 

Here's the link: http://www.timet.com/fab-p30.htm

Here's the link to their Design and Fabrication manual on Titanium to be viewed in HTML:

http://www.timet.com/view.asp?cnct=61&tab=

This link is to the same manual in .pdf format:

http://www.timet.com/pdfs/ti-handbook.pdf

Here's another good link that may be familiar with Stephan:

http://www.thyssenkrupp-titanium.com/printable.php?id=technical/titan_applications/kb13.html

This excerpt is from one of my favorite Ti reference books may be helpful, although one must read the info carefully:

http://books.google.com/books?id=HgzukknbNGAC&pg=PA72&lpg=PA72&dq=titanium+filler+metal+guide&source=web&ots=KZ-0gg3I1H&sig=X-60E2Zqb-UY0ripHgyLF9BpFYQ&hl=en&sa=X&oi=book_result&resnum=3&ct=result#PPA72,M1

Here's a rather interesting article which may or may not be useful:

http://www.slv-rostock.de/pdf/graz97.pdf

Finally, here's another good one from The Welding Institute (TWI):

http://www.twi.co.uk/content/jk24.html

I almost forgot about this one which also might assist in some of Shane Feder's queries regarding Ti:

http://www.wtia.com.au/pdf/TGN-MS-02%20Titanium.pdf

This one is from Miller:

http://www.millerwelds.com/education/articles/article120.html

This is the last one - Period!!!

http://www.welding.org/newsletters/summer2002/titanium.html

Well that's enough for now... I thnk that having all of this to look over will help you in better deciding whether or not to use Ti-6Al-4V for filler when welding together CP grade 2 Titanium. ;)

Respectfully,
Henry