Hello all
I would like to Harden and temper a tool I made out of 1045
steel. I have all the temperatures and holding times needed, but as
for a quenching medium, I have a slight problem.
An oil bath is better than water, but I dont have the proper oil. I
dont want to use motor oil, even though the part is submerged, I dont
want to explode.
I was thinking vegetable oil would do fine...
Any suggestions?
Thanks, Jay
Any oil will work. I have used peanut oil - left over from turkey fry - it
has a high flash point. And I've used mineral oil, which is nice because it
doesn't go rancid. Motor oil is just fine for a one off. It's pretty smelly
though.
Can you put the motor oil in a container with a lid?
Drop the piece in, then sit the lid on (loosely). Won't the stop the smoke and
the stink, but it smothers the flame nicely.
(Works for me)
Jeff
I may be telling you something you already know, so excuse me in advance if
I am, but 1045 will only quench in oil if it's in fairly thin sections. 1045
is a water-hardening, plain-carbon steel. If the part you want to harden is
thin, oil is no problem. In fact, it probably will help resist warping a
bit. But it won't quench 1045 fast enough in thicker sections.
What's "thick" and "thin"? I don't have any hard data, but I'd guess that
1/4" is the limit for oil-quenching 1045.
It's not a straight-line relationship, BTW. You have to reach a critical
threshhold of quenching rate, or you get no hardening at all -- none, nada,
zilch. But there is a narrow range in which you get more or less hardening.
That quench-rate zone is quite narrow.
Ed Huntress
Thanks for you response..
The tool is a bench block I made, cylindrical in shape, similar to the
Starrett blocks. The main difference is there are 6 , M6 threaded
holes around the circumference to allow clamping to the block.
Diameter 3.000"
Height 2.500"
Wall Thickness .300"
Top thickness .500"
My knowledge of heat treating is mostly theory, but not much practical
work. I was thinking about case hardening, as I have 10 pounds of
Kasenite, but I figured if I could harden it, then temper, that would
be better, as I also have a portable Rockwell tester, and I wanted the
practice.
I was reading the Machinery Handbook, and gathered that quenching in
water would not produce the desired effect, as the oxygen would cause
, more or less, uneven hardening.
Do you figure water will be better?
Thanks,Jay
I have two suggestions- Quickly submerge the part below the surface and
there will be no flame and always agitate the part or else bubbles will form
and the cooling rate may not be sufficient.
Here's my best guess for a short answer: given the shape of your part, no.
I'd go with oil. But that doesn't mean that oil will do the job you want. It
means that I think there's too much risk of cracking or at least building in
too much stress if you use water. You're going to do some pounding on this
thing, after all. If oil does it, you're home free. If it doesn't, at least
your bench block will be safer.
And here's the longer answer. Your bench block is an excellent example of
why slow-quenching tool steels were developed. Fairly massive, it will
not through-harden in any plain carbon steel, anyway. And the faster quench
rates required by plain carbon steel will stress that part, potentially
causing trouble at the holes. If you've studied some heat treating you
probably know why that is. Cracks could develop at the edges of the hole(s).
The best material for that block is an air-hardening tool steel. With some
skill in heat treating, it's probably also a safe candidate for an
oil-hardening steel, which, by my guess, is what Starrett probably uses. If
you're going to make it out of carbon steel, which is what I'd do at home,
I'd make it out of 1020 and case harden it -- especially if I had as much
Kasenit around as you do.
The trouble with 1045 for this job is that it's a little high in carbon,
given the great difference in section thicknesses between the places with
holes versus those without, for water quenching -- including water quenching
for the purpose of case hardening.
On the other hand, it's a medium-carbon steel that isn't going to be subject
to the fairly extreme expansion stress (the result of conversion to
martensite) that you'd experience with a higher-carbon steel like 1095. So
you may get away with it.
If you had used 1020 or another low-carbon steel made for case hardening,
you'd probably be on safer ground because, although a rapid quench will
cause some stresses due to thermal contraction, at least you won't compound
the problem with differential expansion as a result of martensite
conversion, which would add to the thermal stress.
1045 can be hardened up to Rc 58 with a water quench. I don't have the
maximum value for oil quenching handy, but 1045 often is oil-quenched in
industry. You're probably going to have to agitate the part to get enough
heat conduction away from it to get any hardening at all, using oil, given
its mass. Oil can harden it but it may fail entirely if the heat conducted
from inside the block prevents the surface (which is all you really care
about, of course) from attaining an adequate quench rate. That's the
threshhold business I was talking about. The gentle quench can do some
hardening AS LONG AS your actual quench rate isn't impeded by heat
conduction from the mass inside. That's the classic problem with judging
which medium to use for quenching, in middle-of-the-road cases like this.
Here are some links that will clear up some of these points, given that you
know something about heat treating. The first two are from a 1920s edition
of Machinery's Handbook. The last two are from Timken. In the very first
one, scroll down until you get to the section on 1045. If you *really* want
to get into it, search on Heat Treating 1045 Steel, without quotes, on
Google. There's a regular cornucopia there.
Hey, you could leave it soft and you'll have a useful bench block;
as-delivered 1045 ain't all bad. Or you can take a chance and learn
something useful. That's what makes this amateur stuff fun.
Good luck, Jay.
Oh, I should have pointed out, as an aside, that there's a good chance
Starrett hardens these blocks by induction hardening. This part is a natural
for that process. You can get a hard surface, to a controlled depth, without
generating significant heat in the mass of the part.
But that's for controlled industrial production, with experiments and tests.
Ed Huntress
you have to understand what you are trying to do... cool the part at a
certain rate and do it evenly.... Each oil has a different rate of heat
absorption so the different oils will give you different results.
Steels have varying requirements depending on the type. There are oil
hardening, air hardening and some are done in brine.
Dropping the piece in a bucket will give you poor results since there
will be uneven heat loss and the part hardness wont be consistent. the
oil should be circulated or the part agitated in the oil.... also the
oil should not be cold since it will tend to form cracks in the metal in
some tool steels. If you keep the part submerged it will not smoke and
will not explode. The quantity of oil must cover the piece completely or
it will smoke and catch fire. don't hesitate when you plunge it into the
oil and don't pull it out until it is cool.
John
Outstanding write-up Ed. Thanks.
I wonder if you could answer one question: In the description
of case hardening from the Machinery's Handbook above, it is
suggested that a cast or wrought iron box be used in the carbonizing
process. As is the usual case for old literature such as this, the
iron box is mentioned in an offhand way, as though everyone has some
laying around. As you know, wrought iron stock is effectively
equivalent to unobtainium these days. Is there any reason that wrought
or cast iron was preferred back when that book was written? Was it
just what was most commonly available back then, or is there some
advantage to it over, say, steel?
Thanks again.
Of course, acquiring the hooves and horns will be another problem! :-)
Whatever you do, the oil must contain NO water. If it does your whole
quench container can explode from steam formed when the hot part hits
the water. If in doubt, heat the oil to beyond the boiling point of
water first to get rid of any water. Then let it cool to about room
temp before using it.
When yo use it, avoid the tendancy to let the part drop to the
bottom of the quench container, because that's where the water may lurk.
I don't think you will be able to tell any difference between various
oils in this application. I use used crankcase oil for this regularly.
I agree with other posters that, in future, use 4140 or O1 for
something like this.
Pete Stanaitis
-------------------
Jay wrote:
I really don't know. There are boats and muffles made of sheet steel today,
so my guess is that it doesn't matter. But I'd double check that before
betting anything on it.
My pleasure.
Charred leather or rawhide is supposed to be good. You could get one of
those rawhide bones at the pet shop and toss it on the barbie.
Ed Huntress
True, stainless steel tool wrap is another example, I think. Or is that
just used to seal out oxygen during heat treating?
As a point of info, that description does say that old shoe leather and
belting is _not_ suitable material for case hardening. It must be the
"impurities" in that leather from the tanning process (and possibly shoe
polish?) that make it unsuitable. Doesn't say anything about chewy toys
though! :-)
Well, that's what a heat-treating boat does, too. With a metal boat, or a
stainless foil wrap, you have to throw in something to keep the carburizing
potential up a little bit, even if you aren't case hardening.
BTW, something to keep in mind, if you haven't done this, is that potter's
clay makes an effective wrap for slow carburizing. Just roll some out fairly
thin (maybe 3/16" or 1/4" at most) with a rolling pin and wrap the part,
with some carburizing material, like a burrito or a dumpling. Then pinch the
ends closed, poke a couple of holes with a toothpick or whatever to keep it
from exploding, and let it dry for a day or two. Warm it up slowly to drive
off any remaining water, and then toss it into the coals, or whatever you
use for case hardening. When it's done, just crack it open with a hammer.
I've always wondered about that. Leather can be tanned in several different
ways, which have very different chemistries.
You also can buy sliced hooves at the pet shop.
Ed Huntress
Next time I'm food shopping I'll get some burritos and give this a try.
No, seriously, I take your meaning and it sounds like an excellent idea.
I was wondering about using some sort of ceramic pot instead of a steel
or iron box. I never thought of just encasing the part in potter's clay
along with the carburizing material. Sounds much easier to do than baking
a special air-tight ceramic box.
The container for pack carburizing can be iron, steel, ceramic, it doesn't
matter as long as it can stand the heat without cracking or distortion.
Some gunsmiths often use terra cotta pots from a plant nursery when color
case casing. www.brownells sells the hardening compounds. You can get bone
charcoal at
I forgot to mention that you should wrap the part in paper first, to keep
the clay from touching it while it's still wet. And, if you're just
heat-treating, rather than carburizing, the paper is enough.
If you're inclined to be obsessive, lay a strip of wood lathe or something
similar on each side of the clay when you're rolling it out, for screeds.
That way you'll get a uniform thickness of clay.
Have fun.
Ed Huntress
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