Hi Michael,
Mate noneed to blast fittings just make sure there clean acetone them is sweet,marksing tape all joints
Do you gap fittings ??,
if you do this & Purge you will get a nice bead on inside,
as i wasPipfitter,coded welder doing only Stainless & other Exotic metals,
One thing i would say to do ,DON`T Tack in gap BRIDGE TACK in 4 spots so you can get a NICE weld all the way around,
you just grind tack off i know its SMALL PIPE but its the BEAD ON INSIDE which you want nice & even ,
HOPE its of some help,
Keep up Great work,
Cheer`s Chuckie