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Many thanks for the advice, Frank, and the
welcome. Aware of the lower yield but putting that into the ABS shell calcs
programme it looked OK. However I take your point on the brittleness at the
weld zone. I was looking at 316L which under ASME
is only good for 25000 yield. Waiting on Sandvik for the other properties. Maybe
I will stick to 516. Thanks. Regards, Hugh From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of ShellyDalg@aol.com Hi Hugh and welcome to the group. There
are several guys using the acrylic domes, so I'll let them answer that one. I looked at using stainless for my hull,
and probably would go that way if I was starting new but there are some draw
backs. First off, stainless doesn't have the
yield strength of the 516-70 steel most of us are using. Some of it gets as low
as 35Kpsi. Unless you get a higher grade like 309 or
316 stainless, it still gets rusty. When you get to the higher grades, it can
get brittle at the weld zone. The cost is also a factor. My tank heads at 84
inches were about $1000 each plus delivery. A low grade stainless like 304 was
close to $2500 each, and again, still gets rusty and isn't near as strong as
the 70 series steel. Pretty much have to rely on a good paint job to protect
either type of metal so I went with the 516-70. It's easily found, strong,
malleable, and reasonably priced. This steel is used for high temperature
boiler applications and certified mill specs can be had from the vendors. Welding on it is easier too. I'm using a
tig set-up for most welds, and 7018 arc rod for some cover passes. It's easy,
clean, and the rod can be found at any local supplier. Mostly though, the extra strength is what
made my decision. Frank D.
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