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I was trying to make some hand punches from scrap car engine valves,
(upcycling it might be called) thinking that I could anneal,
re-shape, and re-harden the steel at the working end of the tool. In
this case I wanted to make decorative punches to hammer designs or
textures onto non-ferrous metals.
So I took some car engine valves, annealed all of it by heating to
red and allowing it to cool slowly. At home I usually swathe it in
fibre blanket (a kiln lining material), but last week when I was
showing Andria how to do this in the absence of blanket I just
allowed the red-hot steel to cool slowly right there beside the hot
bricks surrounding the soldering bay.
The steel was annealed. We could easily saw off the valve head and
file a design into one end.
Then I expected to re-harden the tool at the working end, so heated
to bright red and quenched in (at first) water. No luck. Tried again
by quenching in engine oil - still no hardening happened.
Now that I Google it I note that someone in the Newsgroup
rec.crafts.metalworking writes:
> Subject: Re: Q about automotive valves and seats ...
> attempting to make a small gouge from a valve stem to carve
> copper... I annealed it, forged to shape, sharpened, and quenched
> in icy brine. Tested on the copper before tempering; it's soft and
> useless. Whatever it's made of, seems to not be heat treatable,
> unless I did something awfully wrong.
> Test it with a magnet. 21/4N exhaust valve steel is stainless
> austenitic - non magnetic and not heat treatable. You may find that
> the other end of the stem 'is' magnetic. Most std production
> exhaust valves are two piece friction welded - 21/4N head and half
> the stem - the top half of the stem being magnetic EN52B or
> similar. Heat treatable at 900C plus. Try the same trick with an
> inlet valve and you'll make a perfectly usable cutting tool for
> light use.
Hmm. I think I have inlet valves here. They're not very coked up.
A thought occurs to me: anneal and don't harden at all. The engine
valve steel seems so tough that in some applications I wonder if we
really need to harden it... for jobs where the steel has little
strain on it, and we're stamping silver and copper only.
What do all y'all think?
Brian
Brian Adam
Auckland NEW ZEALAND
www.adam.co.nz
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