heat treating results

T

twynn5586

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Aug 21, 2002
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I made up some test blade from 440c and heat treated them in my kiln. The first blade I didn't temper. It would cut brass and hold it's razor edge but shattered when I hit it with a hammer (pretty damn fine grain). The second was was tempered at 400 for 30min but wasn't much change. The third I left in the oven at 400 for 4 hours (didn't mean to leave it in for so long but I forgot about it) which it took a couple hard hits to the brass then lost its razor edge (It would cut a little hair but not near as much as before).

Is there any way to harden just the edge? Lastly does anybody know what flavor stainless the "miracle blade perfection series" is made from? You know the ones on that stupid infomercial that "Chef Tony" uses.
 
I think you need to either elaborate on your heat treating technique or alter it. I treat 440C this way- heat to 1880 and and hold for 30 min in a controlled atmosphere furnace or kiln = no air. The air will burn up much of the carbon in the blade material. If you can't control the atmosphere then you need to wrap the blade in heat treating foil. Quench in warm oil and draw at 375 for 2 one hour cycles. This should give you a rockwell hardness between 57-59 with good toughness. I'm not sure that you can edge quench 440C?

Chef tony uses stainless blades that are serrated, that's why they don't dull. When he cuts something metal he is dulling the tips of the serrations but not the part that does the cutting. Those knives are junk!
 
I held the blade at 1900 for 5 min with no foil wrap or anything and quenched in water. Everything came out fine except the last blade (it warped a little. Well even if I did burn all the carbon out I still have a knife that'll cut stuff. Anyway I thought I'd try my hand at heat treating stainless and see how it went.

Do you think if I put some refactory cement or something on the spine of the blade it would keep it from getting to 1900 degrees leaving the edge the only thing that got to temp?
 
According to my notes, 440C should be oil quenched or rapid air quenched. If oil quenched the oil should be pre-heated to about 140 F. to minimize thermal shock. Stainless decarbs very deeply if not protected from oxygen. You should get some hi-temp foil for air quenched steels. Leave it naked for oil quenching. 440C requires only about 5 minutes soak and may not decarb too awful badly but would prefer to foil wrap or paint and rapid air quench. I have not treated 440C yet but have done other stainless that requires longer soak times. No were have I yet seen that 440C should be water quenched. Temper before steel is allowed to cool below 125 F. From my notes I would probably choose a temper of about 375 F - 385 F. and I would not worry at all about leaving in temper oven too long - only not long enough. I would temper three times.

It seems like Striper28 has good experience with 440C and I would lean more towards what he says than what I say. However I suggest you try both.

Roger
 
I too haven't heard anything about quenching in water. The only reason I did was I didn't want to wait for it to cool (I didn't have much time). Anyway, I was just tring different things. I heard that you're supposed to use foil but I wanted to see how I'd do without. If the heattreating process goes off without a problem how's the flexability going to be (while being able to hold a decent edge)? Should you be able to bend it 90 degrees without breaking?
 
I've not yet done destructive testing, except for some edge retension tests on numbers of feet of cardboard.

Roger
 
A 90deg flex test is generally only performed on forged blades. It is part of the ABS test where you have to cut a free hanging 1in rope, cut a 2X4 in half twice and then the flex test. The first 2 are to test edge geometry and sharpness and edge holding abilities. The flex test tests your heat treating knowlege.

Check out the tutorials on this site. They have them for heat treating, differential heat treating, Quenching media and their uses, Testing blades, and how to make a blade to pass the ABS journeyman smith test. It will answer lots of your questions.

Link to tutorials
 
I don't think your going to get any stainless blade to flex 90 degrees. Just not going to happen at any useable hardness level :( I just did my first 440C blade, using a torch and oil quench (brought it up to color and held for 5 minutes, quenched in motor oil, did this 3 times as recommended in previous threads. It would skate a file after the first one though). I tempered for about 3 hours at 400 deg F. Normally I do two 2 hour cycles, but things got busy and I wanted to get this one finished to see what it would be like. I didn't break it, but judging from the way my sharpening stones would cut it, its high 50's, maybe 60RC, and seems to have a really fine grain. Takes a VERY polished edge.
This stuff behaves COMPLETELY different than O1 heat treated similarly. It doesn't grind as cleanly on the finish grind and hand rubbing it was hell. It didn't act like it would chip, but there definitely isn't the same level of flexibility as O1.
 
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