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Annealing stainless steel


#1

Hi. My kids put another stainless steel spoon down the disposal. I
should be able to repair it, I’m a metalsmith! Question is, how does
one anneal stainless steel.

Thanks.
Peg


#2

With the exception of knife blades, stainless steel used in the
making of kitchen and dining implements is 300 series or similar
austenitic stainless steel. To anneal it you need to heat it to 1750
F and water quench, unlike carbon steel or 400 series martensitic
stainless you should quench austenitic stainless steels to make them
soft. However you will find it will not be much softer than it is
now. It is tough stuff even in its annealed state.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#3

Peg,

For relief of cold working stresses or deep drawn parts of USS 18-8
should be heated to 1750 Degrees F followed by rapid cooling. This
comes from the Fabrication of USS Stainless Steel. Not knowing which
type stainless your spoon is made from the above procedure will
probably get you in the ball park. Stainless is tough stuff to form
whether it is annealed or not. Try bending it back into shape by
hand and then hammerform it with a nylon or UHMW hammer backed up by
a steel stake. Don’t use a steel hammer. Any hammer marks are there
to stay they won’t planish out like silver. Deep nicks will need to
be sanded or filed and then polished out.

Duck


#4

Hi Peg;

You must have time on your hands. An accomplished metalsmith could
pull that off in about 1/2 hour, including finishing out the nicks
and polishing, if he/she had the right equipment (a set of graduated
grit unified wheels, spoon stakes, planishing hammers, craytex
wheels for the fordom to do the inside of the bowl, etc.). That would
make that spoon worth about $25 in my shop. Stainless is steel, a
ferrous metal, so annealing it is a different procedure than with
silver, gold, brass, etc. You need to get it to a visible orange
color and let it cool down slowly. It’s probably not going to get any
softer than it is presently. I’d get an alumina block, or charcoal,
and heat up the surface of it with a very large torch, like a
hardware store propane torch or a prestolite, or a Smith with a big
tip, or a rosebud tip on your Little Torch. This will “bank” a little
extra heat to slow cooling. Once the block is pre-heated, put the
spoon on it and get it up to a good visible red/orange color. If
you’ve got some fiberfrax, cover it, otherwise, just leave it alone
until it’s cool enough to pick up. Never mind about re-hardening,
it’s going to be to stiff to distort unless you use if for a pry bar.
I’ve done a lot of work in stainless, and I’ve usually worked it
while it’s bright orange. To polish it, you’ll have to get down to at
least a 400 grit, preferably 600 unless you’ve got a 6 inch stitched
muslin buff and some GreyStar. Good luck.

David L. Huffman


#5

Hello Peg,

I’ve done it… both dropped the spoon in the disposal and (tried) to
recover it. I was able to beat out the bowl shape again, but
stainless steel keeps the nicks and gouges. The best I could do was
to file the nicks out of the edges and smooth out the gouges in the
bowl of the spool, then use progressive grits to restore the finish.
It was an interesting experiment. BTW, I did not try to anneal the
metal. Frankly, just buy a new one. It’s cheaper. In fact, buy a
whole place-setting and you’re covered against future
disposal-disasters!

Judy in Kansas


#6
Stainless is steel, a ferrous metal, so annealing it is a different
procedure than with silver, gold, brass, etc. You need to get it to
a visible orange color and let it cool down slowly. 

Austenitic stainless is different than most iron carbon alloys heat
and quench is the rule. Slow cooling will not yield the softest
material. I went and looked up the data sheet to be sure, I was off
in the temperature it needs to be heated to 1850 F-2050 F then
quenched

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#7

I’m not convinced you need to anneal it. If it can bend once it’ll
bend twice. Heating it will discolor it, I’ve got lots of SS tools to
prove that. If you’re having trouble use a vise with copper guards on
the jaws, clamp the spoon as close to the bend as you can and pry or
whack it back into shape.

All the disposal damage I’ve fixed, and its alot, the main repair is
gouges and burs. If you’re a glutton for punishment most can be
removed at least to the point of usability. If deep gouges run across
the pattern you’re kinda outa luck.


#8

Hi Jim;

Austenitic stainless is different than most iron carbon alloys
heat and quench is the rule. Slow cooling will not yield the
softest material. 

I stand corrected. There are carbon bearing stainless alloys, I
believe, used in making blades, and these do harden and temper. Most
of what I’ve used in my career has been a few stainless alloys
prefered by the knifemakers (back in the days when I did grunt work
for Daryl Meier). I’ve never understood the metalurgy well, just
followed the instructions on the tech sheets. But I think everyone
here who’s familiar with repairing stainless tableware are in
agreement that whatever you do, it’s not going to soften appreciably,
not like a non-ferrous alloy like bronze or brass or sterling will.
It’s going to be stubborn stuff, like nickle, which makes up a good
part of it.

My dad was a glassblower, and he used to give me the old punti rods
that burned down too short to use. These were some really nice
stainless. I used to hot forge it into cuff bracelets and neck
collars. It was arduous to finish and polish it, but it was beautiful
when it was finished.

David L. Huffman


#9

Hello All,

a friend of mine needs to bend stainless rod into a hook shape. The
questions are, how to anneal the metal and how to remove the
discoloration from the annealing process.

Thanks for any help.
Marc


#10
a friend of mine needs to bend stainless rod into a hook shape.
The questions are, how to anneal the metal and how to remove the
discoloration from the annealing process. 

I’d bet he doesn’t really need to bother with annealing at all
unless it’s one of the stainless versions that specifically can be
heat treated to harden it, and even then, it might be soft enough as
sold. Much stainless is like simple low carbon steel. Soft enough to
work without a lot of fuss.

Peter


#11

There are lots of types of stainless but the most common varieties
are the 300 series. To anneal them you heat to 1750F-1850F then water
quench. Removing the scale from heating requires a pickling in an
acid bath (hydrochloric or nitric) or ferric chloride

Jim

James Binnion
James Binnion Metal Arts


#12

Hello Marc,

First you need to know which type of stainless you have? If there is
a reactive metal (Ti or Nb) in your stainless (317 or 347 series)
then you have to hold the metal at 900 Celsius for about 3 hours.
Otherwise you can anneal stainless the same way you would any other
steel (heated to cherry red over a reduction environment), however
it must be quenched rapidly so you need to use water. This goes for
all types of stainless.

The trick is to then harden the steel again, this is why you really
need to know which type you have. 300 series stainless cannot be heat
treated, only work hardened. Some of the 400 series stainless can be
heat treated and some cannot, you’ll need to look this up.

All can be hardened by working the steel so I would go with this
method, so when making the hook don’t just bend it, hammer it
gradually into the hook until the metal re hardens. Also if you plan
to polish the hook you will have to do so after you anneal, then
anneal and form your hook and then polish the hook again after it is
finished. The second polishing will be much easier if the metal has
already been polished when

To get the discoloration off will require you to grind off the oxide
layer or use a pickle that does not contain muriatic acid
(hydrochloric acid). You could also use any product used to remove
exhaust pipe bluing.

I hope this helps
Kenneth


#13

Thank you James and Peter.

Sounds like my friend shouldn’t have any problems with his project
knowing this info.

Yours,
Marc