Hey Metals!
The process they (Grumman Aircraft of Bethpage, NY out on Long Island) used on the "Tomcat's" fuselage was EBW.
Otherwise known as Electron Beam Welding.
The process was totally automated (customized one of a kind system) and, the welding was performed in a "clamshell" type vacuum chamber. Do'nt worry about the "brainfart" because your intentions were good!!!
I know first hand about this system at Grumman because, I had the honor (seems like many) years ago to actually see how this system performed and MAN-O-MAN, did it ever!!! Perhaps one of the GREATEST Fighter aircraft EVER produced in the WORLD!!! GO NAVY!!! SECOND TO NONE!!!
The F-14's motto is "ANYTIME - BABY"!!! Too bad they're being retired!!!
Anywho, getting back to your situation "Racefan"... As TimGary mentioned, with the appropriate trailing shields, the need for a vacuum chamber can be avoided. SWP also had some good advice also as did Lawrence...
I've personally welded a variety of Titanium.
From CP (commercially Pure) grades to a variety of Ti alloys when I worked for company in New Jersey and, the key words to successful weldments were: Cleanliness & backpurge and monitor the heck out of the joints before during & after welding for gas purity!!! I say this because even if everything else was strictly followed such as mentioned in the previous posts, if the joints were'nt clean (white glove treatment) & backpurged properly - it did'nt matter if everything else was correctly done... The welds would turn out to have some CONTAMINATION and they would not consistently pass NDT or NDE (Non Destructive Testing or Non Destructive Evaluation, they both mean the same)... Just as important is to make sure not to contaminate the joint with arc strikes or tungsten contamination...
Color is also an important factor in understanding how to set up your current, travel angle, travel speed, work angles, tip to work distance, etc. Cross contamination is critical also. Meaning that the machine tool bits used in fabrication, the grinding/cutting wheels, the wire wheels must be of the type that does NOT leave any residue or impregnate any of it's materials into the Ti base metal and, must be used exclusively on ONLY the specific Ti base metal!!! NOT on any other metal PERIOD!!! I cannot stress this enough!!!
I could go on and on but, the only way you're going to learn how to weld Ti properly is to learn from someone who has already done so successfully on a consistent basis because, even though the metal is relatively easy to weld, it is far more difficult to produce consistent high quality welds with this metal without knowing and experiencing firsthand - ALL of the factors & variables, ALL of the necessary precautions that are required to ensure success due to the very nature of this reactive metal... Not to mention that Ti is'nt a relatively inexpensive metal to fabricate and weld compared to lets say, Aluminum... I hope this helps!!!
Respectfully,
SSBN727 Run Silent... Run Deep!!!