"Proctologically Violated©®" wrote in message
...
Great links.

But, I'm curious about your comments on SS/chrome. SS is less stiff?? Not
the stuff I deal with, esp. tubing. Or sheet.

Yes. It's a little less stiff than mild steel. I'll see if I can find some
Young's Modulus figures for common materials and post them. The
"springiness" of a material -- that is, its stiffness up to the point where
it breaks or takes a permanent bend -- is measured by Young's Modulus, or
the Modulus of Elasticity.

Chrome aids hardening?

Yes. I'd have to go back to my texts, but my recollection is that, up to
some moderate percentage, it *slightly* improves superficial hardness, but
that it *greatly* increases depth of hardening. The air-hardening steels,
which through-harden to great depth, get their through-hardening properties
from chromium. It's all but impossible to through-harden a thick piece of
plain, high-carbon steel, such as AISI 1095.

Then why is hardenable SS so rare?? I think a rel
recent development, as well.

Common grades of stainless, the 300-Series, can't be quench-hardened because
the high chromium content (and maybe the nickel contributes; I forget)
prevent the steel from transforming into the hard phase, which is called
martensite. 300-Series stainless remains in the austenitic phase at room
temperature.

When you heat-treat a piece of high-carbon steel, heating it above the
transformation temperature (say, 1400 - 1650 deg F) converts the steel phase
to austenite, where it remains as long as you keep it above the
transformation temperature. Austenite is soft. If you cool the steel slowly,
it transforms into another soft phase, called ferrite. If you quench it
quickly, faster than the rate known as its "critical quench rate," it
transforms into martensite, instead of ferrite. Martensite is hard.

Plain carbon steels have a very fast critical quench rate. That's why you
have to quench them in water. Certain alloy ingredients slow that rate down.
That's "oil-hardening" steel. You don't necessarily quench it in oil
(whether you do depends on the piece's thickness, and the result you want),
but the suggestion is that you can quench it a little slower and the
austenite will still convert to martensite.

High-alloy steels that can be quenched even more slowly are the
air-hardening steels. In very thin sections, even 4130 is more-or-less
air-hardening. The A-Series tool steels will fully harden in air, up to
substantial thicknesses.

I hope this is clear. I hate to have to re-edit these things. g

--
Ed Huntress