"Jordan" wrote in message
u...
Can all steels be case hardened?

No. Look up "carburizing," "case hardening," "nitriding," and
"carbonitriding" in your favorite metals info source. Machinery's Handbook
contains the basics, and a lot of libraries have an old copy on the shelves.
There's a lot to absorb on the subject.

In general, plain low-carbon steels are the easiest to case-harden, and
produce the best combinations of surface hardness and overall toughness.
There are some low-alloy steels that are made specifically to be
case-hardened. High-carbon and high-alloy steels don't carburize well, in
general, but they can be nitrided, which is an extremely thin but also
extremely hard layer of what amounts to a conversion coating. Carburizing
can be done much deeper into the steel. All carburizing means is that a lot
of carbon has been added to the surface and that surface layer then behaves
like high-carbon steel. Primarily, that means it can be quench-hardened.
Usually the hardness is higher than you would normally leave a comparable
piece of plain high-carbon steel, because you don't have to worry as much
about brittleness with a hardened case.

As for struts, I think the materials cover quite a range. The better ones
are high-strength alloy and hard-chrome plated. All "hard chrome" means is
that the layer of chrome is thick and isn't plated over a softer plating,
such as copper. The chrome itself is really no harder than thin, cosmetic
layers of chrome.

I don't know what they're making run-of-the-mill struts out of these days.
Sorry. Be wary of the "junkyard steels" sites on the Web. Many of them have
copied old Machinery's Handbook or SME listings from the 1940s and '50s.
Things have changed. But the better sites, maintained by knifemakers and
high-quality blacksmiths, are aware of this and give up-to-date information.
Ask a knifemaker. They really know their steels.

Good luck.

--
Ed Huntress