Hello,  A question regarding TI filler:  GTAW of ASTM B338 Grade 9 .039"-.045" wall tubing. Purged Tee joints, fillet welds.    AWS G2.4 Table 3 recommends ERTi-9 filler for this base material.     Yet another reliable source has told me that ERTi-5ELI is a better filler for Gr.9 due to the change in grain structure when cooling, i.e. loss of strength. Is this true?
Although in AWS B2.1 Table III-1 both F-No.53 and F-No.55 are in the same group, is welding 3Al-2.5V tubing with 6Al-4V ELI filler wrong?
Thank you.

There are several factors to be considered when selecting a filler metal for any type or combinations of base metals. Recommended filler metals are just what they are said to be, recommendations. It is up to the fabricator or the designer to determine which "recommended" filler metal meets their need to match base metal chemistry, mechanical properties, toughness, response to post weld heat treatment, color match, etc. There are certain things a table or chart cannot do for you, i.e., make a final decision as to which filler metal will meet all your needs.

You may want to consider consulting with the company that supplied the raw material for the tubing you are welding. TiMet would be a good source of technical information regarding titanium. They offered a short course on welding titanium.  their technical/marketing people might be happy to send you information about welding their titanium products.

Best regards - Al