Re: which steel

["Marsee Skidmore" <heyred@email.msn.com>]

A516 is garden variety low carbon steel. The only thing special about it is
the pedigree. It's really high quality, really clean, really tightly
controlled recipe low carbon steel. It's just the ticket for internal
pressure vessels designed per ASME cookbook. It's not bad for Psubs, but you
can do better. However, high yield strength is not the key to Psubs
happiness. What you want is toughness, which is a combination of yield
strength and ductility. 4130 is scores well in these categories, but it's
snotty to weld, and I think it demands heat treatment after hot forming.
Take a look at High Strength Low Alloy (HSLA) steels. :-o Joe
-----Original Message-----
From: asmyth <asmyth@hsomail.com>
To: PSUBS <Personal_Submersibles@psubs.org>
Date: Saturday, August 28, 1999 4:19 PM
Subject: which steel


>Hi everyone,
>
>I am wondering which type of steel is recommended for the pressure hull.
I'm
>not about to start on the hull for quite some time yet, but I am about to
>make some parts that will be welded to it eventually, so I thought I'd use
>the same material if possible, and this forces a decision. Obviously, this
>one issue could be discussed for ever, since there are so many physical
>properties to weigh, as well as price, etc.
>
>I am not looking for an Unobtainium alloy that will take me to the Marianas
>trench... just something COMMON (i.e., inexpensive and available in every
>shape or size) but with a good yield strength, machinability, and
>weld-ability.
>
>My little PSUB library includes a Welding Journal article about the
>construction of a K-boat. It says they used "A516, Gr.70 boilerplate steel,
>welded with E7018 covered electrodes". I then found pages and pages about
>A516 on Bethlehem Steel's website, which basically said this is the cats
>whiskers for pressure vessels. Yet the yield strength was specified as 38K
>psi. The Machinery's Handbook says common alloys like 4130 are around 46
>Kpsi yield strength, and some are way higher. So what's special about A516?
>
>No doubt I'm revealing my metallurgical ignorance, but I'd appreciate any
>suggestions from someone who knows more about this!
>
>- Alec Smyth
>
>
>