What filler rod is the best for welding titanium grade 2, grade 5, and grade 9? I read it's best to use a softer grade of filler wire than the parent metal. My initial plan was to use ErTi-2 for grade 2, ErTi-5 for grade 5, and ErTi-9 for grade 9. Also read that ErTi-1 can be used for grades 2, 5, ...