Hardening steel - recycled car-parts

Jewelry Discussion
1

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

2

Hi Brian

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.

Interesting story and since I’m just learning about tool steels etc
(making blanking dies) I might have something to share here.

Just recently did a weekend workshop and learnt to make blanking
dies and the teacher said she never bothered to harden the steel.
Have used the dye I made in the workshop about 60 times (unhardened)
and it’s still working though one can see a little distortion at the
edges. Subseqent dies I have made I have hardened (having some A2
tool steel which does harden) and these are not distorting.

Still the lesson here is, you can use them unhardened but they
probably won’t last as long.

Have fun,
Renate

3

Brian,

In general, this is why - when I was blacksmithing quite a bit - I
mostly quit trying to recycle steel, especially car parts!

Steel used to mean iron with some carbon (0 to 1%), maybe with a
trace of chrome, moly, nickel, etc. Leaf springs from GM cars were
great medium carbon steel, so too the coilovers. Intake valves (the
lower temp side), usually good stuff.

Now steels are custom cooked for the application, with silicons and
other high temp alloying agents, and as you discovered, a
homogeneous part may actually be heterogeneous with neat tricks like
stir welding, friction welding, or explosive cladding/welding being
used to join unlike metals invisibly and perfectly, with no or
minimal heat zones. Air hardening or high temp steels can be joined
right up against ordinary carbon steels and the only way to find the
transition zone is trial and error (for most of us). Even if you can
identify it, some of the “exotic” alloys (stainless esp.) have
pretty stringent heat treating requirements, with soak, quench, draw
cycles that involve timers, controlled ramp ovens, inert
atmospheres, etc. Far cry from heat it till the magnet doesn’t stick
and drop it in water or oil!

As far as leaving it annealed… well, yeah. Copper is a lot softer
than even annealed steel. I guess it depends on the application. How
detailed is your stamp? What is your backing material when stamping?
I’m pretty overboard on this, probably, but I really only make tools
out of new, O1 or W1 drill stock, and I heat treat and temper all
of them. I figure if I’m taking the time to make that tool, I want
it to outlive me. Good steel from a reputable supplier, olive oil
for the quench (yummy smells) and a perfect surface finish on every
tool.

cheers,
Kevin

p.s. On a curmudgeonly side note, you can’t always count on getting
quality homogeneous steel from a “new” material supplier either… I
ruined a hammer face on a ball bearing that was embedded in some new
purchased, but obviously recycled, dimensional stock as I was forging
at a bright orange heat… the ball bearing was still at full
hardness :frowning: I’ve also received air hardening drill rod when ordering
oil hardening from online metals.com, so test a piece any time you
order new stock!

4 
As far as leaving it annealed... well, yeah. Copper is a lot softer
than even annealed steel. I guess it depends on the application.
How detailed is your stamp?

Thanks for the steel details in your post, Kevin. I too have made my
most useful and often-used punches from O1 (Oil hardened) stock and
tempered to straw (approx, depending on the shape). And I can
appreciate that were I to have spent a great amount of time doing a
design on the punch, it ought to be hardened.

However, many other punch tools I use and teach the use of are really
only patterning and texturing tools. In this case the design that is
filed emery’d and polished on the working end is more of an abstract
‘design element’ which produces an interesting pattern or texture.

I can now see that this kind of punch may well be fine left annealed,
occasionally needing touching up every so often.

Brian
Brian Adam
www.adam.co.nz

5

Been there! Perhaps vintage engines used corbon steel valves because
they needed frequent re-seating and valve grinding. Modern engines
use exotic composites including titanium valves for racing engines.
Old solid push pods are good if you can find them, but they too are
nearly extinct.

Coil springs are a good source of high carbon steel. Those from tilt
type garage door openers provide a long rod about 6mm in diameter. A
bit bigger diameter are torsion bar springs used for keeping the car
boot (trunk) open, and coil springs from motor cycle shock absorbers.
Spokes from old motor cycle and bmx wheels are medium/high carbon and
work well for smaller tools.

To unwind a coil spring I clamp a stout bar vertically in the vice,
heat the whole coil red hot, drop it over the bar, then quickly pull
on the lower end of the coil with the tongs. The coil will reel off
in one swift movement leaving you with a surprisingly long and kinky
rod, ready for cutting to length and further treatment. Just be aware
that if there are any cracks in the spring it can break there as you
are unwinding it and it’s not nice to be stumbling in the company of
a long whippy piece of red hot metal…been there too!

Cheers, Alastair

6 
Steel used to mean iron with some carbon (0 to 1%), maybe with a
trace of chrome, moly, nickel, etc. Leaf springs from GM cars were
great medium carbon steel, so too the coilovers. Intake valves
(the lower temp side), usually good stuff. Now steels are custom
cooked for the application, with silicons and other high temp
alloying agents

I recently saw a reference book (Stahlschlussel : Key to Steel) in
its 21st edition that claims to catalog 60,000 commercial steel
alloys !

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts

360-756-6550

7

Here are a couple of good links for those interested in making your
own tools from steel:

www.threeplanes.net/toolsteel?
Tool Steels - Heat Treatment Considerations for Water, Oil and Air Hardening Tool Steels

The first one even has a color chart and tells you where you can buy
the chart.

The color chart I use is from Tempil, Inc. and is titled “Basic
Guide to Ferrous Metallurgy.” Usual disclaimer, just have the chart.

I got my color chart and learned how to make stamps from a jewelry
class taught by a blacksmith. A really fun way to get a new
perspective on making jewelry.

Carolyn

8 
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.

Perhaps an easier solution: buy some O-1 oil hardening drill rod.
This is available off the shelf from most industrial suppliers like
MSC and McMaster-Carr, and has no difficulty being hardened. It’s
available in a wide variety of sizes, both metric and imperial. It
ships in un-hardened form.

Paul Anderson

9 
On a curmudgeonly side note, you can't always count on getting
quality homogeneous steel from a "new" material supplier either...
I ruined a hammer face on a ball bearing that was embedded in some
new purchased, but obviously recycled, dimensional stock as I was
forging at a bright orange heat... the ball bearing was still at
full hardness

I build miniature steam engines as a hobby, and a lot of casting
suppliers use recycled metal in their castings. I’ve hit hard spots
in cast iron castings that were like glass, and could barely be cut
with a carbide cutter. I’ve had to anneal more than one casting just
to get it to a point where I could machine it.

Paul Anderson

10

this has been suggested before by Jim Binnion and myself:

The US price is even lower now – $13.57 US

buy the book you won’t regret it.

There are a couple very simple things you can do to determine what
type of steel you have. A magnet will tell you what type steel it is
– If it doesn’t attract a magnet it,it is an austenitic steel and
can be heat annealed but not heat hardened. It can be work hardened
( which causes problems in cutting it). Steel that is magnetic may
be hardenable if it has enough carbon in it. this can be determined
by looking at the spark pattern when grinding it. The book does show
spark patterns. Cars are not likely to have much mystery metal in
them, but modern frame and body steel is not the same as it used to
be. Lighter, thinner, stronger alloys are being used now. These will
be very low carbon with the lighter, stronger properties coming from
the added non carbon metals in the alloy.

As far as automotive valves go there are a few problems - Exhaust
valves may show up as austenitic. Which means they are not easily
hardened, but some will be magnetic and but not desirable forging
stock because they are Sodium cooled. The valves are hollow and
filled with sodium which spontaneously catch Fire with water… The
larger standard American engines will not normally have sodium
cooled but aftermarket sodium filled valves are around installed in
racing engines. I don’t know about newer US engines. European
engines commonly will have sodium cooled exhaust valves.so It is
better just to avoid exhaust valves for reworking into tools and
stick with magnetic inlet valves.

a few Internet sites on steel identification aRe:

http://www.alexdenouden.nl/04/vonkset.htm

http://metalwebnews.org/machinist/ch2.html

jesse