440c

T

twynn5586

Joined
Aug 21, 2002
Messages
30
How long are you supposed to keep the blade in a cryo freeze? I recall three days but I'm not sure. Lastly, is the blade going to be brittle after this process or can I put the finishing touches on it?
 
Have you done the hardening at temp., yet?
Maybe it would be better if you explained what you have already done, as far as heat treat.:confused:
 
A teacher my dad teaches with said I could use his liquid nitrogen. So, I thought i'd give it a shot since it's free. This is the first time I would be doing a cyro freeze or working with stainless.

Ok, This is what i'm doing:
1. Triple tempering at 400 (or whatever you think's best)
2. Cryo freeze with liquid nitro for x lenght of time
3. finish the blade
 
Your information is incomplete. It leaves out the most important part, the basic heat treating itself.
This is just an idea copied from a suppliers catalog. My suggestion would be to send it to Paul Bos and have it professionally done, as most folks don't have the capabilities of getting this stuff to the right high temperature, and holding it there. It is very critical that the temps don't vary during this operation.
TECHNICAL INFO

440C Stainless

Typical Analysis

C 1.03 Mn .44 P.025 S.001 Si .65 Ni .30 Cr 16.68 Mo .50 Cu .16

Hardness

R/B 92-95



Heat Treating Information

Initial Quench Temperature - 1850°F-1950°F max

Hold for 5 minutes

Quench in warm oil or air cool

Do not overheat (too much time or too high temperature)



Hardening & Tempering Information

300°F - 1 hour - R/C 60

500°F - 1 hour - R/C 57

800°F - 1 hour - R/C 56


Your Cryo would fall between the heat treating, and the final tempering. Temper twice, BTW.:eek:
 
So... If I put the blade in a furnace at 1850° and then quenched wouldn't that harden the entire blade? Does that mess with the flexabilty? I don't know much about knife making but I'm assuming that at 1850° the metal will go nonmagnetic so that when you quench you get ahead of the pearlite nose (or whatever it's called). Please correct me if I'm wrong but again I'm new to knife making and the only thing I've done with a stainless knife is sharpen it.
 
Do as Mike (above) says. Cryo in liquid nitrogen no less than 10 to 12 hours but only after heat treat (often refered to as the quench) and at least one temper (or 'snap temper' - a temper at about 50 degrees F. less than your normal temper). The steel will be very brittle after pulling from the liquid nitrogen until it warms to room temperature. After cryo temper two more times.

Yes, after heat treating and before tempering and cryo the steel will be brittle.

Roger
 
Originally posted by twynn5586
So... If I put the blade in a furnace at 1850° and then quenched wouldn't that harden the entire blade? Does that mess with the flexabilty? I don't know much about knife making but I'm assuming that at 1850° the metal will go nonmagnetic so that when you quench you get ahead of the pearlite nose (or whatever it's called). Please correct me if I'm wrong but again I'm new to knife making and the only thing I've done with a stainless knife is sharpen it.
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The metal will go non magnetic way before 1850 degrees. This is why I said it might be a better idea to send it to a professional. You wont be able to hold 1850 degrees for the time required, unless you have a heat treating oven.
 
Is there a test to see if the heat treating worked? What's the need for holding the metal at that temp? Lastly, can I guess the temp by looking at the color or is that to risky? The reason I don't want to send it to anyone is that the whole hardening process is what makes the knife. The only thing I would be doing is just making it look pretty. My thinking is that if I were to send it to someone to harden it it would be the same as me going to the store, getting a knife and just shine it up and say I made it. For me it takes away the feeling of accomplishment.
 
Originally posted by twynn5586
Is there a test to see if the heat treating worked? What's the need for holding the metal at that temp? Lastly, can I guess the temp by looking at the color or is that to risky? The reason I don't want to send it to anyone is that the whole hardening process is what makes the knife. The only thing I would be doing is just making it look pretty. My thinking is that if I were to send it to someone to harden it it would be the same as me going to the store, getting a knife and just shine it up and say I made it. For me it takes away the feeling of accomplishment.
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I would hardly call getting a bar of steel and grinding an acceptable blade, ""going to the store, getting a knife and just shine it up."
The hardening process does not make the knife. The maker has done that first. Hardening/tempering, make it more useful. 440C is a complex alloy steel, that requires something more than gettin her cherry red, and droppin her in the ol tranny fluid. If you wish to heat treat your own blades, I would suggest NON stainless steels of a simpler makeup. Steels like O1, 1095, 1084, 5160. Those can all be heat treated in a shop without too much trouble, and they hold a great edge.
 
Alright... Were's the cheapest place I can get this done at? I saw that Texas Knifemaker supplies does it for 10$ and cryo for 4$. I got a kiln that'll get to the right temp but my problem is this. I can try to learn how to do it myself and take a chance at messing my blade up or send it to Texas Knifemaker and have them do it for 14$
 
I use Paul Bos, in El Cajon, CA. But I think for the quantity you have, TKS would work fine.
 
If your doing this for yourself, there's no reason you can't take a gamble and play around with it yourself. Especially if you have a kiln to bring it up to temp and control the temperature.
If you do a search on hardening 440C in this forum, you'll come up with a few threads that describe doing it yourself.
Basically, you heat and quench 3 times in a row in order to make up for not holding at exactly the right temperature for a long period of time. If you send it somewhere for professional heat treat there is actually a whole cycle they take it through with an electric kiln just in heating it up.
After you have heated and quenched it 3 times, you should temper it once at the proper heat for the hardness you want. The chart mike posted will give you that. Alot of people just use a normal oven like you cook in, leave it in for about 2 hours.
Then you can do your cryo treating. After that you should temper it one or two more times in the oven, and then you can start doing your finish work.
I have been making knives with O1, and using pretty much this method, only you only have to quench it once provided everything works right.I plan on trying some 440C in the near future. It probably won't turn out the same as a professional heat treat on 440C but that doesn't mean it won't be usable.
If you want to test it after quenching to make sure its hard, you can do a file test. A file should skate across rather than biting in, it will have a sort of glassy feel, if the steel hardened properly.

If you decided to contract it out, I can recommend texas knifemakers supply. I sent two ATS34 blades to them and was very happy with the service and the results. Paul Bos is the best in the business but I'm pretty sure he has enough business coming his way that he can't/doesn't take small batches anymore (correct me on this one guys?)
 
I'll second TKS

But on a side note Mike, would you happen to have(or know where I can find) similar information for O1? want to gather all tthe info i can get on it
 
I got a few test knifes to try in my kiln and had a couple of questions. Will I have to worry about scale? Second, from what I've read some people say hold it at 1900 for anywhere from 30 min to 5 min. Is there an advantage to holding it longer or is 30 min to long?
 
Paul Bos is the best in the business but I'm pretty sure he has enough business coming his way that he can't/doesn't take small batches anymore (correct me on this one guys?)
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Matt, I spoke with Paul in November and at that time he said that he would take my single 440C blade. He did say that he would have to wait for more of the same steel to come in so that he would have a large enough batch to offset his costs.

Rick
 
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