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Jon. If the hull is 70 series ( AS 516-70 ) then you use 7018 on
everything. Filler metal is always to match the base metal. I suggest TIG the
root, stick the filler, and TIG the cover pass. Then back grind the inside
and TIG that with a cover pass. ALL of it with 70 series rod. The process
of laying down small overlapping TIG beads makes a very strong and clean weld,
without applying a ton of heat to the joint being welded. That reduces stress
build-up, and it's much easier to make really clean welds. Bad thing is, it's
slow and you need cover gas too ( ARGON ) which runs about $125 a bottle. Still,
the weld quality is the best.
When you stick weld the filler pass, make sure you clean the start/stop
REAL good, and when you lay down the TIG cover pass, most inclusions or weld
defects from the stick weld pass will show up as a little hole or bubble. Stop
welding, and grind or drill out the inclusion down to nice clean steel.
It's a good idea to get a stainless wire wheel on your little
grinder and keep it right next to you so you can clean out the start/stop
while it's still hot. Start the stick "ARC" a little before the end of the
previous bead, then weld over the end and down into the groove so the molten
puddle flows and fuses with the previous bead. Any wobbling or nasty stuff from
starting the arc will be on top of the previous bead and is easy to buff off
with the grinder before you start the TIG cover passes. Mostly just practice.
Although I've been welding for over 40 years, I still run a practice bead on
scrap every time I get ready to weld stuff. It helps me focus on making a good
weld, and if there's any adjustment with the machine or my position or what
ever, better to get that all fixed on the scrap, and get your mind focused on
the welding to be done.
Frank D.
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