Joe wrote:
Stronger, harder, stronger..

I think you're mistaken there. Higher carbon alloys are
stiffer, not stronger.

... Steel with sufficient carbon compositions
can be heat-treated

Yeah, great idea. A heat-treated boat... and the
advantage(s) of such??

.... allowing
parts to be fabricated in an easily-formable soft state then made
harder for structural applications.

"Hardness" is of no benefit in a structural application. And
I think "easily-formable" is relative.


High Carbon steel rolls and holds it's shape nicely, and I suppose high
carbon slows rust too!
I've never seen a carbon anything rust.


Ever looked?

Peter Wiley wrote:
There is no good reason for using high carbon steel in a yacht hull.


I can think of one... if you happened to have a lot of it
laying around in approximately the right size pieces.


It's harder to weld.

The weld heat affected zone has different characteristics to the parent
material, usually worse, nearly always different corrosion
susceptibility.


Yes, it changes the crystalline structure of the metal.


High carbon steel has somewhat greater tensile strength, but so what.

IIRC the biggest difference is a straighter yield curve,
maybe slightly stronger too. If high carbon steel were
really stronger in tension, they'd make cable from it.


Steel yacht hulls are massively overstrength anyway, the plate
thickness is set by the need for min thickness for corrosion allowance
over the life of the hull.


It's the best stuff if somebody is going to be shooting at
you, or you plan to bounce over a lot of rocks. Other than
that, the only reason I can think of to build a boat of less
than 20 tons (or so) out of steel is because you are already
a skilled metal worker and have a lot of supplies, and
really really like the concept of a bulletproof boat
(although it should be recognized that fiberglass can also
be bulletproof).

I wonder how well a boat would hold up if sprayed both sides
with that plastic pick-up truck bed liner material?


High carbon steel does *not* slow rust appreciably. Some steel alloys
have greater corrosion resistance but this is due to the alloying
elements, not the carbon. In fact, very *low* carbon steel resists
corrosion better than high carbon steel.


IIRC most stainless steels are very very low carbon.

OTOH there is a lot of truth in Joe's statements if you take
them to their logical conclusion and use the highest
carbon material... carbon fiber!


Feel free to argue about it all you like. I'll just quote more bits
from 'The Procedure Handbook of Arc Welding' by the Lincoln Electric
Company.

You might own a steel boat, Joe, but so do I. Just that mine's bigger
than yours :-)


Yeah but Joe lives in Texas. Everything looks much bigger there.

Fresh Breezes- Doug King