[TheForge] Hot-rolled versus cold-rolled

[Phlip]

Ene bichizh ogsen baina shuu...

> I've heard that hot-rolled is relatively soft compared to the same type of
> steel in cold-rolled.
> Is this true, and does it apply only when shaping something cold?

See my incoming posting about that. Basicly, with cold rolled, you have a
compressed surface- work-hardened.

> It seems that once they're heated to forging temperature, working
cold-rolled
> shouldn't take any more effort than hot-rolled. Am I correct about that?
>
> Bob

Yes, once it's hot, it's the same stuff, more or less. Depending on how it
was compressed. it will get a few odd bends in it, but if you're working it
hot, a couple whacks with a hammer will straighten that out.

The only time you might run into a problem with the two is if you use the
cold rolled in a precision hot application, for example, bracing your
non-efficent furnace precisely an inch from each wall. As long as it's cool,
it will stay in place, but the more heat that it gets, the faster it will
"normalize", in other words, readjust itself to the position it wants to be
in, rather than the position it was forced into. Eventually it will do this
whether there's added heat or not, but the heat makes it do it much faster.

Usually, this is only a problem if you have a long span- across a couple of
feet, a 1/4 or 1/2 inch deviation usually isn't very significant, but the
same deviation across 30 feet is a gross total of 7-8 inches, and the usual
deviation is a bow of some sort- not something you want in a precision
structural member.

Phlip

"When in doubt, heat it up and hit it with a hammer."
 Blacksmith's credo.

 If it walks like a duck, and quacks like a duck, it is probably not a
cat.

Never a horse that cain't be rode,
And never a rider who cain't be throwed....