From: "Lee and Bex" <leebex@xtra.co.nz>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: Re: Re: [PSUBS-MAILIST] K-350 Reinforcing Rings
Date: Mon, 11 Sep 2006 17:33:09 +1200
Hi Tom,
Hy 80 is a high yield strength material, I have not built a submarine but
have worked on many high strength alloys of steel including pressure
vessels and spools, the beauty of mild steel which has an approximate yield
of around 250mpa is that it isnt prone to "work fatigue", if you were to
imagine a plastic school ruler and were to continuously apply force in a
bending manner along the same axis for a long period of time the rule could
be worked back and forth for many many times without fracture, however the
ruler would fracture if bent too far with very little elongation or
stretch, if the rule were to be made to resist that deformation or
elongation it would take far greater bending force to make it bend back and
forth making it a stronger material, a material that gains strength loses
ductility and unfortunately hy80 although is a very strong material...it is
still prone to fatigue when being constantly "worked" (as happens at
different depths due to pressure), basically what this means as all things
equal a submarine made of mild or low carbon steel (<0.3% c.e)would not go
as deep as one of hy 80 but it would not have work hardening issues
associated with higher carbon alloys such as hy80 and hy100.
However hy80 would absolutely go to greater depths provided an exact weld
procedure was followed with strict pre and post heat treatment. You cannot
get something for nothing!
the greater the hardness = the less ductility = the deeper dive capability
= more difficulty in fabrication and welding
the less the hardness = the more ductile = the less dive capability = ease
to fabricate and weld
The key is in the balance related to the operational requirement of the
vessel.
Regards
Leon Ducrot
----- Original Message ----- From: "Thomas Doster"
<thomas.doster@gmail.com>
To: <personal_submersibles@psubs.org>
Sent: Monday, September 11, 2006 4:54 PM
Subject: Re: Re: [PSUBS-MAILIST] K-350 Reinforcing Rings
As someone who welds on submarines for a living, I'd have to agree
with Dan H's methodology for welding the rings. It is a good way to
minimize the stress. With regard to what Leon contributed, I think
it's imperative that anyone even considering building any sort of
pressure vessel knows these things. Understanding the stress that
welding causes on steel is VERY important to know, especially when
your life is being supported by it. While there are a few methods of
stress reduction, not all are readily available to all PSubbers. The
best idea, if you haven't spent any time welding professionally, or
even if you have, is to read over some corporate welding requirements.
Anything you can get your hands on. A lot of them specify pre-heat and
interpass temperatures, joint design specifications, and many other
things. I think the American Bureau of Shipping documentation on
Hyberbaric Chambers has a lot of these things in there as well.
If you have the time, sit in on a metallurgy class at a local college.
Or attend as a student. If you're welding yourself, there are SO MANY
things you can and should learn before tackling such a project.
One question I have for Dan, Leon, or anyone else who knows:
Has anyone constructed a K-350 submarine out of HY-80 steel or any
other material? Would that increase it's depth capacity? What do the
plans specify?
Thanks,
-Tom
On 9/10/06, ShellyDalg@aol.com <ShellyDalg@aol.com> wrote:
Hello. One more thing. I asked the question about stress relieving the
finished hull also. There are some companies that have huge ovens to do
just
that. One in Texas that makes the tank heads I want does it on tank heads
for high pressure, and will even do a whole tank.
Their oven is very large. I think stress relieving is required on tanks
that
store very cold things and create problems with cold brittle stress.
The company is " Fort Worth F & D Tank Head " --great prices there.
Frank Dalgleish.
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