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radkins
08-20-2011, 06:52 PM
After failing to find any supplier that still has a stock of Kasenit I bought a 1 lb container of "Cherry Red" from Enco, apparently it's about the same stuff with a different name. OK the instructions are a bit sketchy although quite plain up until the part about quenching, it simply says the part can be quenched in water or oil or simply allowed to air cool, :confused: Which is it? Would it be better to oil or water quench or air cool and what criteria would determine the best method? Finally if I do water or oil quench do I need to temper afterward? It doesn't say anything about tempering after quenching, does not even mention it, but I would think it would be necessary or would it?

BTW, I am using it to case-harden 1026 steel.

gwilson
08-20-2011, 07:11 PM
Mild steel case hardened with Kasenit or its generics will develop only a THIN crust of case which should be quenched in water. Air cooling can be done,but then you have to reheat the piece to red hot and water quench.

Sometimes a bunch of case hardened parts are allowed to cool,and re heated to red to harden. I'm not certain why this would be done. Maybe to keep you from dumping a bunch of hot,melted Kasenit into the water?

If you want a DEEPER case than just a few thousanths,use charcoal and put the parts in a covered crucible. I have done this and gotten a case over 1/32" deep(which was as much as was needed for these parts).

Aquarium charcoal is a good charcoal for case hardening. Kasenit products do not produce a deep case,while charcoal does.

Some disagree,but I think a good heavy lid helps drive the carbon deeper into the red hot steel. When steel is red hot,its structure opens up more,better admitting carbon into the metal. From personal experience,I have found that a good heavy lid helps,even if it only gives a pound or so more pressure inside the crucible.

Since the case hardening is not very deep,it is not necessary to temper the parts. IF I was making a knife blade,like they do in Pakistan,where the blades are laid in the bottom of a layer of charcoal,and only get casehardened on 1 side(you should hone the SOFT side of a Pakistani knife,to avoid wearing the case off),I WOULD temper the blade to a straw color afterwards,since a fully hardened knife edge would be brittle. Otherwise,no tempering is needed.

Evan
08-20-2011, 08:49 PM
1026 will harden fairly well just by heating and fast quenching in brine. 1026 contains manganese as well as around .26% carbon so that enhances the hardenability. In sections up to a couple of inches a fast quench will produce up to about RC50 hardness.

SGW
08-20-2011, 08:53 PM
It's not exactly that "its structure opens up." Carbon literally dissolves in hot iron. The longer you leave steel heated in the presence of carbon, the deeper the carbon will migrate into the metal.

darryl
08-20-2011, 09:13 PM
So- highjacking a little- how do you get carbon out of steel? Heat it in a non-carbonous container in a vacuum? I've been of the impression that prolonged heating will actually let the carbon escape-

radkins
08-20-2011, 09:35 PM
I would not have thought 1026 would have gotten as hard as R50 but I was aware that it would harden somewhat by heating and quenching, I asked about that a while back and sure enough it worked but I didn't think 1026 would get that hard-that's something to consider. Also a few weeks ago I made a a failed attempt at color hardening although the parts I did seemed to take a really good case, again I was using advice I got here and the result was quite satisfactory even if the color did not turn out like I wanted. So why am I using the Cherry Red now? Because I still have not got a good controllable oven and the crude set-up I was using, while it did work, requires too much guess work and this time I was just looking for a quick easy way to spot harden some tooling and one small piece for my rifle project.



OK so using Cherry Red and water for the quench no tempering necessary?

huntinguy
08-20-2011, 09:43 PM
So- highjacking a little- how do you get carbon out of steel? Heat it in a non-carbonous container in a vacuum? I've been of the impression that prolonged heating will actually let the carbon escape-

take it up to critical temperature and hold it there without a carbon atmosphere and it will burn away. At least the surface will, depends on how long you hold it there.

the put in charcoal thing is also called carbon packing. It was commonly used for both case hardening and heat treating prior to the advent of the carbon controlled furnaces now used for heat treating.

in modern heat treat furnaces with controlled atmosphere you set the carbon soak to the same amount... or maybe one point more than the carbon content of the steel being heat treated. If set too high you get cracking or case hardening if set too low you end up burning off the carbon from the material being heat treated.

Evan
08-20-2011, 10:15 PM
Removing the carbon is called "decarburizing". By holding the steel above 1450F or so the steel is converted to austenite and the carbon is able to react with oxygen at the surface. This has a negative side effect of promoting large crystal growth when the steel is cooled and reduces the ductility and yield strength considerably.


OK so using Cherry Red and water for the quench no tempering necessary?

That depends, as usual. In this case (!) it depends on how thin the thinnest section is. If the part has very thin sections then it should be tempered because those sections will become very brittle. If you are case hardening something like a large pin then no tempering will be necessary. Tempering is easy and can be done in the kitchen oven.

gwilson
08-20-2011, 10:33 PM
I said pretty much the same thing,as in knife blades with thin cutting edges. Thin parts will be the same,and need tempering.

SGW,I think we are saying the same thing in different terms. The carbon has to get into the iron. More rapid movement of the molecules enables it to enter.

Evan
08-21-2011, 12:09 AM
It isn't just the rapidity of molecular movement. At about 1400F steel undergoes a phase transition from Body Centred Cubic crystals (BCC) to Face Centered Cubic crystals (FCC). That is the change from Martensite (ferrite) to Austenite. Carbon has low solubility in martensite, less than one percent. Because of this it also has low mobility in martensite. When the phase changes to FCC the solubility suddenly goes up to 2.5 to 4 percent depending on temperature. At the same time the mobility of the carbon increases dramatically, both in and out of the bulk iron. Iron also becomes non magnetic at the FCC phase change temperature.

radkins
08-21-2011, 01:19 AM
Tempering is easy and can be done in the kitchen oven.



A couple of these parts have a thin edge, about, .050, so would around 450 deg for 1/2 hour or so do the job?

Bob Ford
08-21-2011, 01:42 AM
Bring the parts to the 450 temperature then keep them there for 1/2 hr. Should end up with RC between 55 and 60.

Bob