Hello Again Shane!

Just got an e-mail from Stacey Nyakan, a metallurgist from TIMET's Henderson Technical Laboratory.

She wrote: "Normally a stress relief PWHT is performed. This is optional but, recommended. As with other metals, PWHT reduces residual stresses in the weld zone and improves fatigue performance. PWHT of different durations are required for stress relief of the various grades.

According to the TWI "Welding Titanium Handbook", stress relief for one to two hours (depending on thickness and temperature) at 600c (1110F) max is usually adequate for both CP and 6-4 (Grade 12 is a modified Commercially Pure=CP grade) to reduce residual stress to manageable levels while avoiding excessive thermal oxidation. Higher temperatures should be avoided, since microstructural ageing can reduce toughness and ductility."

Stacey Nyakana
Metallurgist
Henderson Technical Laboratory
TIMET
702-564-2544 Ext. 369
702-564-9038 Fax
Stacey.Nyakana@TIMET.com

As for myself, I interpreted the words "optional but, recommended." to say that PWHT is'nt required although, considered a best practice...

I would also like to add that the rods or wire that you're using should be of the low oxygen type in order to prevent cracking.
If you look at all the other titanium grades, you will see that the wire chemistry is lower than the base material.

Btw, you should be able to get some additional information regarding your question from the Titanium Fabrication Corporation's people if you e-mail them all of the pertinent information including the filler wire chemistry that you'll be using to deposit the welds...

I hope this helps but if you really want to know if it's a requirement then definitely contact either the American Society of Testing Materials (ASTM) or the American Society of Mechanical Engineers (ASME).

The ASTM uses Techstreet as their specifications and technical documents distributor. You can find these standards at:
http://www.cssinfo.com/info/astm.html When you get to this site, there's a catalogue search. Just type in the key word: "Titanium"
You should get abou 100 hits, and all you have to do is go to hits 21-30.
You'll find either one of the standards that you're looking for (B861-02 or B862-02). These are the updated versions of the previous ones I wrote in my earlier reply to you. You can order these standards for $36.00 US dollars, (I do'nt know what the exchange rate is currently with Australia's equivalent) and they will be sent in 24 hrs via .pdf document.

ASME specifications are adapted from ASTM specs. for the same products, but include only those grades or alloys of Ti that are permitted for pressure vessel construction. ASME favors alloys which have higher ductility, usually with elongation of at least 10%.
ASME requires more stringent material testing and documentation, often adopting as mandatory, some of the optional requirements contained in the ASTM specs. Otherwise, ASTM and ASME specs are almost identical.

You will note that the specification: B861-02 indicates an ASTM non-ferrous material specification and the year of the latest update.
More of this info is available at: http://www.tifab.com/subpages/tech_spec_grades.htm

I just checked out the ASME digital store but, could'nt find anything in there other than B31.3 since you're working with hazardous materials, I had to edit my original incorrect suggestion about B31.11 (does'nt cover what your application is about) The website is:
http://www.store.asme.org/category.asp?catalog_name=Codes+and+Standards&category_name=&Page=1
They also offer short courses for B31.3 that are given at various locations in North America. Check out these sites:
http://ww2.asme.org/pd/courseDetail.cfm?CO_ID=635

http://ww2.asme.org/pd/courseDetail.cfm?CO_ID=506
The first one is a bit expensive but, if you do alot of this type of work, then it's well worth it. I believe the second address suits you better...

Well - that's about all I could find out for now but, I should get some more info before the weekend so I'll post some more when I get more info...

Respectfully,

SSBN727 Run Silent... Run Deep!!!