Quenching 440C

B

BCK

Joined
Feb 4, 1999
Messages
79
I work with ATS-34 as it is air quenched.
440C should be quenched in hot oil formula, if what I read is correct. Although I have quenched 440 both ways, I am unshure of the difference in the quality of the blade (I don't have a Rockwell tester). If anyone can tell me about what is best, the difference, etc. I sure would appreciate it. Thanx!!

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BCK: 440-C can be quenched in air or oil. Oil quench will produce faster cooling, and thus a higher initial hardness. However, oil quenching necessitates removing the knife from the foil pouch (I assume you're using foil), and thus opens up the nasty world of decarb, as well as the loss of temperature while you get the envelope open prior to quench. Some will say that you can quench into oil with the knife still in the foil. This is wrong, period.
Ths difficulty with an air quench is getting the quench rate up high enough. Again, I don't recommend following the standard rule of opening the envelope, unless you wait until the red is gone from the steel first.
So, when you air quench, you'll likely get a lower as quenched hardness. If you liquid nitrogen treat, after the first temper, the hardness will probably come right back.

Good Luck!!
RJ Martin
 
Thnx. for the info. RJ.
Maybe I'll go back to making a few projects from 440. I usually dont remove from the foil as you know, it tends to weld itself to the steel somewhat & it's hard to get off without
loosing the critical temp. as you said. Not to mention scorching the pinkies.
I take the blade from the oven & place it in a vice that has been modified with some airated pipe to help the cooling & cut down the chance of warpage. Then place a fan to it. Thank-you again. Nice to hear from you.
smile.gif
Bruce.

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Bruce: If the foil is sticking, I'd like to know how hot your Austenizing temp is. Also, for small blades, if you have nice smooth jaws in your vise, you can press quench the blade right in the jaws. This will cool it real nicely, and make it really flat. Forced air can be tricky, depending if the foil is touching the blade or not, the cooling rate will be different.

RJ
 
RJ:
I have been using exclusively ATS-34 & have been taking it to 1960 Deg. & holding for 20 min.. I believe I know what you mean about the diff. cooling rate due to foil, because many times the color of the blade has been different when I unwrap em.. Do you think that I would be better off to clamp them without the fan? The reason I put the fan to them, is because the square pipe that I have attached to my vice gets naturally very hot & holds the heat. I get my foil from the folks at Sheffield supply, & it says that it will tend to stick at temps of 2000 & above. Unfortunatly it sticks below that temp. & I cant get it off safely.Look forward to your reply...Bruce.
 
Bruce: I'm going from memory here, but, I think the last time I did 440C, I used 1875 and it worked great, but you should check the exact temp. I hit about Rc64 at quench. As to those little color marks/swirls, I suspect those are caused by what little air is left inside the foil pack. I get them too. If there is black/grey, then, you had a pinhole and decarb. bad.
Is your furnace accurate? That's the only other reason I can think that the foil would stick.

RJ
 
RJ:
I hope that my oven is correct. I have never tested it. It's a "Paragon" that I bought new, a mod. 14. I have been trusting it to be correct, but your right, who knows.
The difference in color I mentioned is the steel, ATS-34 that is, comes out the most beautifull shades of purple & red, mixed in with the steely grey color. It really looks nice. Whether it's supposed to look like that, I'm not really sure. (Sure would love to have an RC. tester)!!
 
Bruce, I have 2 Paragons and both of them are off. The KM9 is 2 percent at 1850 degrees and the KM14 is off just a little less. I check them about every 3 months and when I change an element. Doesn't sound like much but at some of the higher temps it means alot.

I don't ever recall having a blade stick to the foil. Maybe it's the cigarette butt that I put in the pouch that does the trick.
They do come out with the colors, though.

A Rockwell tester is great to have just to make sure you are doing things right. I test every blade. Sometimes if you heat treat by the charts you won't end up where you want to be. Most of them are designed for much thicker stock than knife blades so you have to be careful.
 
Yes, I agree with Kit. Check your furnace!!! You can use ceramic cones or tempil Pellets, but, the cones are easier to interpret. I added a second thermocouple and a digital panel readout so I can monitor the temperature of THE BLADES, not the furnace. It is the bomb!!

RJ
 
Hi Kit:
Thanx. for the info. It's nice to know that someone else has the diff. colors. I was a little concerned about it. I will have to do a temp. test for sure though. With reguards to the sticking problem. When I first got the oven, it came with a small amount of foil, & I had no sticking problem at all! Then, once I ran out, I ordered some from Sheffield, & thats the stuff that sticks. I will have to find another foil supply & test it out. Not to fault Sheffield at all. They have some fine products & I'm very happy with thier service. (I will try adding a butt, see what diff. it makes). It is a little harder to get all this nice stuff living in Canada. Knife making is not all that popular here & thus suppliers are far & few between, & the ones that we do have, offer a limited amount of items. Every time I want something, I have to pay extra for shipping & duty fees. It makes everything quite expensive, so I dont get to try out as many new things as I would like to. Not to mention having to wait 2-3 wks. for the order to arrive. Anyway, thats enough crying. Thank-you for your responce
smile.gif
Take care..Bruce.
 
Thanx RJ.
You guys have been alot of help, & it's been nice to talk to you!! Happy knifemaking!
 
I had a problem with foil sticking to ATS 34. Then it went even further and started sort of crumbling and falling off. Digital readout still read 1950 but it became apparent that the furnace was getting too hot.

The overheat actually caused the ATS34 to change character. After coming out of the furnace and air cooling it lost a lot of its magnetic properties. It would barely stick on a magnetic holder on which I store my blades. The loss of magnetism was obvious when comparing to annealed steel with a hand magnet. This confirmed that something was bad wrong with the furnace.

It's a Paragon KM24 with digital.

The original thermocouple was two separate wires of different metal welded together at the tip. Really an elongated U.

Ordered a replacement from Paragon and it was different. There was an inconel tube with no wires showing outside other than the two terminal wires running to the controller. It looked sort of like the metal tube part of a meat thermometer.

Have had excellent luck controlling the furnace since I made the change.

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Ben R. Ogletree, Jr.
 
Mayor:
Thanx. for your info. I still have not tested the temp. of my oven with ceramic cones yet, but do plan to. Have you ever used these cones to check yours?... I am wondering just how accurate they really are...Do you still find that the foil is sticking to your ATS at 1950 with the new thermocouple?... Thnx. again! Talk to you later.
 
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