Am I right in thinking that case hardening of mild steel can be done by
heating the part up and dunking it in some oil? If so...
How do I know when the part is hot enough? Is there a standard(ish) colour
that I can refer to?
Will a hand blowtorch provide enough heat? Mine runs on a butane/propane
mix.
Would standard non-synthetic engine oil be suitable? Are there other
easily-obtained oils that are better?
How many times should the part be dunked in oil, and how long should it be
dunked for?
Cheers,
--
Wally
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Things are always clearer in the cold, post-upload light.
To case harden mild steel you need to use a case hardeneing compound, available
from most model enginering supply outlets. The object is best thoroughly
cleaned, packed with the compund in an airtight container and then heated to
red heat for an appropriate time depending on the depth of case needed. The
whole lot is then quenched in water.The instructions with the compund should
tell you more. Remember if you are making a small item you could use silver
steel or gauge plate which can be hardened and tempered simply by heating /
quenchcing / tempering. The old casenite compound was very good but is , I
believe, no longer available due to health and safety reasons.
Good luck
Just for more info
Case Hardening compound can still be bought and is listed at
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if you do a site search for the stuff. There will
be other suppliers as said below. But if for small parts and you can
machine a tougher material then just mild steel EN1 etc, then follow the
advise and go for a different material perhaps EN8 which I believe can be
hardened with heat and quenching.
If you are into reading some articles, then try these links :-
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The above seem to be from the 1924 Machinery Handbook
I saw in a recent EKP catalogue that they claimed to have Kasenit, but I don't
know if it's the 'real stuff' with the sodium hexacyanoferrate or not.
Mark Rand
RTFM
EN8 hardens pretty good in oil, I found old engine oil best, but it smells
and produces loads of smoke, and is liable to catch fire if you have lots of
bits to do in a small container (I used a tin plate over the top to kill the
flames) EN16T hardens up even better in oil, it really depends on the
application, one good thing about hardening a better quality steel in oil is
you don't have to spend ages cleaning all the crusted on carbon after case
hardening.
I used to use the above process to harden load cell cups for scales with
capacities of up to 100 tons, with no problem, apart from the time I
hardened a cup before I finished it an couldn't turn it to the finished size
lol (EN8)
HTH
Tim
In article , Mark Rand
writes
Not *that* many years ago, case hardening used to be carried out with
chopped up bits of organic material such as horse's hooves, bones,
etc...
: In article , Mark Rand
: writes
: >: >
: >>To case harden mild steel you need to use a case hardeneing compound,
available
: >>from most model enginering supply outlets. The object is best thoroughly
: >>cleaned, packed with the compund in an airtight container and then
heated to
: >>red heat for an appropriate time depending on the depth of case needed.
The
: >>whole lot is then quenched in water.The instructions with the compund
should
: >>tell you more. Remember if you are making a small item you could use
silver
: >>steel or gauge plate which can be hardened and tempered simply by
heating /
: >>quenchcing / tempering. The old casenite compound was very good but is ,
I
: >>believe, no longer available due to health and safety reasons.
: >>Good luck
: >
: >I saw in a recent EKP catalogue that they claimed to have Kasenit, but I
don't
: >know if it's the 'real stuff' with the sodium hexacyanoferrate or not.
: >
: Not *that* many years ago, case hardening used to be carried out with
: chopped up bits of organic material such as horse's hooves, bones,
or by plunging a red hot sword into a slave..........
When I started in engineering 35 years ago we had a slower method -
mixing salt and ground charcoal (barbeque charcoal not briquettes), with
the item in a small tobacco tin, then heating for 1/2 an hour to an
hour or so.
Packing the tin with charcoal in a barbeque with all the vents open
would probably work. Then take out, clean and heat to red heat and
quench in oil or brine. Don't use water as the cooling is too quick and
as you'll have a 'soft' centre and hard 'case' it can distort or crack.
We only used small amounts so it wasn't worth searching out Kasenite or
similar
Incidentally the 'thistle shaped' barbeques are also good for heat
treating (long soak for rolled 'bright MS before lots of machining to
stop distortion) Oh, and also for stir frying...
The chopped up 'organic' soup used to be used by blacksmiths for dunking
bright red steel to get a hard surface. I remember this when I was very
young ... and also the revolting smell from the 'organic bits'
repeatedly heated and cooled over years in the blacksmith's shop. It
used to be old bones, horse hoof clippings and usually a few 'other
bits' particular to the blacksmith (no, you don't want to go there...)
: Yes, as I intimated in a previous posting to this newsgroup, all of the
: old methods are dying out. Can't get the slaves these days...
:
But almost any carbon source, as others have mentioned, will work. I
remember as an apprentice how slow it was waiting for for the carbon to
migrate into the surface of the steel. Hours and hours for a few thous......
I would always prefer to use a hardening steel these days..
That's the sort of timescale that seems okay to me. What was the ratio of
salt to ground charcoal? Any idea what depth the carbon would penetrate to?
I don't have a garden or a yard, so using a barbie is out. I was thinking of
using a petrol-fueled stove in the doorway of my garage. Would that produce
enough heat? (Small parts, by the way - M6 bolts at the moment).
Noted.
--
Wally
formatting link
Things are always clearer in the cold, post-upload light.
Be careful with 'old engine oil', especially with cars that have
mechanical fuel pumps. You can get a lot of 'light chain' oil after a
while and if there's a mechanical pump working off the camshaft (esp.
older / classic cars) you can get petrol leaking into the oil as well.
Been there, and the eyebrows have now grown back except at full moon...
Mart
In message , Tim
Bird writes
Hmmm. Roughly one part salt to three parts finely ground (coffee grinder
when the other half is out for long enough to clean it thoroughly)
charcoal.
You need to get it at least dull red for half an hour. Probably not
petrol stove. Suggest large tin full of holes. Pack tin containing
mix/parts in larger tin with charcoal. Set light to charcoal and go for
a long coffee...
Has anyone in England discovered the products that would do this
and are available over here?
The ones mentioned are American commercial items.
--
Dave Croft
Warrington
England
Dishwashing liquid I am sure you have. Dishwasher Rinse aid is the
same as the Shaklee basic IIRC. A post on alt.blacksmithing should
give you a lead.
Geoffm
New Zealand
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