Heat Treating O-1

Alarion

Alarion

Joined
Nov 26, 2001
Messages
1,375
Can I ht O-1 using a coal forge and quenching it in 15W40, 5W30 motor oil or hydraulic fluid, like I do for plain carbon steel?
Or do I nead an electronic oven like for hi-tech stainless steels?
 
It isn't a complex steel. Harden from 1450-1500 F , temper 300-500 F. At temperatures above 1500 F you risk more retained austenite, grain growth, and cracking .I would hold at hardening temperature [soak] a bit more than you do with carbon steels.
 
I have used a oxy acetylene torch many times with a magnet ..so i know you can use a coal forge..just watch the temp..check it with the magnet often and youll be fine..later Luke
 
i "think" the proper way to heat treat 0-1, would be in a kiln with either stainless steel foil or some sort of enert gas to keep it from decarbing. Most people can't afford that gas setup, and stainless steel foil works just fine. Using a coal forge, well, you can heat treat anything i'm sure, but there's no real way of determining the actual temperature you're heat treating it at. Plus depending on your fire and how good one is at using a coal forge, you can have areas that get hotter than others, etc etc, which could cause your steel to warp when you quench it. I wouldn't use motor oil of any kind ever. There are quenching solutions specifically made for that type of application. Motor oil sends up toxic fumes when it's heated like that which i'm guessing aren't good for anyone! Use a kiln, unless you plan on some surface grinding to grind all the decarb off.

I think the problem with the whole magnet thing is, if you've heat treated it above non-magnetic, how the heck are you suppose to tell "how over" you went over the 1500' degrees F?
 
Well, surely the kiln gives you exact control on temp and time.
As for the coal forge, you can get pretty even temp, and get it right with some experience.
I use coke, so the fire is always clean as a baby's soul.
for heat treating I use a very gentle blow, watch closely the color of the coals, and use finely broken coal.
I don't keep the blade just sitting there, but move it continuously, so to avoid that some hot spot makes a hot spot in the blade. I do it even in gas forges.
I frequently check the blade with magnet, and watch closely at the color of the steel AND the coals.
When it's OK, I back down somewhat the air, and keep that temp.
It's 20 years I do photography, and I've got a good eye at judging colors, so it's not much a problem for me.
The problem comes in two cases:
1) I do heat treatment always at dusk. I have a lot of light in my shop, and doing it at noon or during the first hours of the afternoon can cause some serious misjudgements of the temp.
2) Can't do it in somebody else's forge. The lighting is different, so are the colors.
Given some time to adjust, and to do some experiment, I could do it. But not right away.
So, I can go to non mag, hold it there pretty correctly, and judge non-mag by eye even before trying to stick the magnet to the blade. Don't have a clue about the actual temp, though, so if it's one of those hi-tech bitchy steels that require a precise temp that has nothing to do with non-mag point, I'll have to have it ht'd by somebody else who has a kiln.:)

For the oils, I don't know where to get graded quenching oil.
I know it'd be better, but all I have is different grades of motor oil, and hydraulic fluid.
I have a bright AND airy shop, and I'm careful, when quenching, NOT to breath the fumes (I actually wear a breathing mask).
But I see the problem: I have just ONE bar of O-1. Never heat treated O-1 before, so I don't know which grade of oil is ok. If it were graded quenching oil, I could just ask, and get the exact grade.
For motor oil, I have just to hope some other "desperado" is quenching using fresh motor oil and tells me what grade is using...:D
 
Leu Custom said:
i "think" the proper way to heat treat 0-1, would be in a kiln with either stainless steel foil or some sort of enert gas to keep it from decarbing. Most people can't afford that gas setup, and stainless steel foil works just fine. Using a coal forge, well, you can heat treat anything i'm sure, but there's no real way of determining the actual temperature you're heat treating it at. Plus depending on your fire and how good one is at using a coal forge, you can have areas that get hotter than others, etc etc, which could cause your steel to warp when you quench it. I wouldn't use motor oil of any kind ever. There are quenching solutions specifically made for that type of application. Motor oil sends up toxic fumes when it's heated like that which i'm guessing aren't good for anyone! Use a kiln, unless you plan on some surface grinding to grind all the decarb off.

I think the problem with the whole magnet thing is, if you've heat treated it above non-magnetic, how the heck are you suppose to tell "how over" you went over the 1500' degrees F?
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Because O-1 needs a much faster quench than air-hardening tool steels, I wouldn't use foil. Decarb shouldn't really be an issue with O-1 yf you're controlling the temperature with an oven and only taking it up to CT.

Plenty of folks HT O-1 with a forge, although a gas forge may be easier to keep even and setup a pyrometer. You're right that it is more difficult to tell exactly how far above non-magnetic you are with just a magnet.

I've used motor oil in the past, but as has been mentioned, it's not good for you. I'd just used veggie oil or mineral oil if there is no access to professional quenchants. Plenty of folks get good using knives without them, no big deal as long as you understand the limitations of the process.
 
I'm SUCH a low tech grungy.

I've done 2 blades in O1, kevin would shudder and kill me with a gladius, but:

heat to non mag in my propane pipe forge, hold it a bit (but not too long, it's not a really fast heating forge), and quench in *heated* motor oil. I use 10w50 because we buy it by the case.
I've done some brine quenching, too. And I'm thinking of moving to a vegetable oil base, but just haven't yet.

I did a triple quench on the first one and a double quench on the second.

I never have had a finished final bevel when I've done my heat treat, so there's a bit of removal after anyway.

They cut and keep on cutting, so it can't be failing :)
 
I think above 1000'F any steel starts to decarb and for sure at 1500'F it will decarb for sure! But then again like I said, if you're just gonna grind it all off like machinists do, then who cares.

Technically stainless steel foil is for air hardening steels, you are correct! But if someone doesn't want to grind a whole bunch of their knife off, then that works or the anti-scale paste (which is kinda toxic i hear)...but who knows :D
 
I just heat treated a batch of 5, O-1 blades in a propane forge with a motor quench.
(used 10-50 synthetic Harley oil)
This was my first time using O-1, and my first time with my new gas forge, Have always used reclaimed files and springs and such in charcoal.
I got a bit thrown off by the Decarb and originally thought that the steel did not harden, but after a light grind found that they had hardened up quite nicely.
My calipers tell me that I only lost .003 of an inch to decarb. I can live with that. The day after I did my heat treating my order of quenching oil from McMaster came in. Shipping for 5 gal. and a piece of steel was only $14.00 and they had it to me in 3 days.
 
Leu Custom said:
I think above 1000'F any steel starts to decarb and for sure at 1500'F it will decarb for sure! But then again like I said, if you're just gonna grind it all off like machinists do, then who cares.

Technically stainless steel foil is for air hardening steels, you are correct! But if someone doesn't want to grind a whole bunch of their knife off, then that works or the anti-scale paste (which is kinda toxic i hear)...but who knows :D
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If you're not air or plate quenching, the foil packet is not advisable. If you cut the blade out of the packet, you're missing your CT by the time you get into the oil, if you're going to drop the whole packet in you've got to consider uneven quenching due to air pockets and the packet slowing the quench.

The decarb you see at 1500 in an oven is truely negligable. We're not talking about machining back into the "good" steel here, we're talking about finish grinding a knife, that's how little it is. If decarb were such an issue, you'd have a whole slew of problems with hand forged pieces, damascus and any knife HT treated with a forge that we just don't see.

No one has to believe me, they can get a rockwell tester out and check. Decarb at 1500 with a 5 minute soak is not going to burn out a blade or make for a lot of machining. You're going to quench the blade and clean it up with finish grinding, then you're going to grind a primary bevel on it and finally finish the edge... you're well past the decarb at this point, even if you finish your knives to 800 grit before ht.
 
AcridSaint said:
If you're not air or plate quenching, the foil packet is not advisable. If you cut the blade out of the packet, you're missing your CT by the time you get into the oil, if you're going to drop the whole packet in you've got to consider uneven quenching due to air pockets and the packet slowing the quench.

The decarb you see at 1500 in an oven is truely negligable. We're not talking about machining back into the "good" steel here, we're talking about finish grinding a knife, that's how little it is. If decarb were such an issue, you'd have a whole slew of problems with hand forged pieces, damascus and any knife HT treated with a forge that we just don't see.

No one has to believe me, they can get a rockwell tester out and check. Decarb at 1500 with a 5 minute soak is not going to burn out a blade or make for a lot of machining. You're going to quench the blade and clean it up with finish grinding, then you're going to grind a primary bevel on it and finally finish the edge... you're well past the decarb at this point, even if you finish your knives to 800 grit before ht.
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I agree people have made O1 knives and treated them in a forge for many years including myself with no problems.
Bob
 
Pohan, The amount of decarb is a product of time, temperature, and atmosphere.
With O-1:
The time above 1250F (the point at which carbon readily starts to combine with oxygen and form CO2) is not long enough to allow significant decarb.
The temperature, 1450-1500F, Is not high enough to foster rapid decarb.
If the forge has the atmosphere controlled and balanced, the reducing atmosphere will retard decarb, also.

Thus, there is no reason for foil with O-1, and many reasons not to use it. I use Turco and have no scale or decarb to deal with. A can will last years.

As to using motor oil.....well lets just say you won't find many well known makers using it. The word "OIL" in 'oil quench' refers to oil based quenchants, not motor oil.

Stacy
 
Stacy: ahhh you're right! I guess a) it all depends on the kind of blade grind you're going to do...if it's flat grind, then no biggy, but if you're doing say a V Grind and don't want to lose the grain on the surface itself by over grinding/polishing, then there would be more of an issue. I suppose in a gas forge, the temperature reaches 1500'F in no time flat whereas a kiln takes a bit of time to get from 1000'F to 1500'F. I guess if you're only austenizing for 5 minutes, then no big deal. Stainless steel foil is really only for air-hardening steels mainly, but whatever less of a mess one has to clean up the better!
 
i have done some work with 01. i started out with a 2 brick forge and moved up to a little 8 inch map gas type forge that is little larger then the 2 brick. i did make some decent sharp knifes from that method. i have since built a kiln and the difference i get from it and the forge seem to be alot. i had a pyrometer in the forge and the kiln. it is so much easier to geta good soak in a kiln. lately i have been putting my blades in at 1500, let my temp rebound in about 1 1/2 mintues then start the time on soak. i have been doing 10 mintues at 1500 and the performance is great. also i hand work my blades once out of ht and i can manage to remove the decarb with minimal effort with 220 sand paper. the kiln i just built for around 250 dollars will got from 1000 to 1500 in about 1 minute 30 seconds or so. and from bare cold kiln to 1500 is just hair over 4 mintues. i like the electric kiln method so much more now.
 
Dakota11, I would be very interested in seeing a foto of the interior of your kiln; very specifically, the placement of the thermocouple relative to the heating coils. Thanks.
 
Dakota 11,
Does the power go out in the rest of town when you kick that thing on? That is an extremely fast ramp time.
 
fitzo, i just measured the inside dimensions and placement of thermocouple. the inertior deminisions are 7 inches wide, 4 and half inches tall and 18 inches deep. the thermocouple comes up from the bottom of kiln and and enters kiln interior 2 inches from the front door and comes up approx 1 inch from the bootom floor. its slightly offset from center to one side, the will put it approx 3 to 3 1/2 half inches. one thing about the kiln i built is when it gets to temp and the elements kick off they only come on for a fraction of a sec every few minutes. so far my bounce around temp seems to be 5 degrees. its wired for 220 at 13 amps and 3100 watts. i did the build that is floating around the web, but i also installed 1 inch koawool all away around the box.
 
mtnsct said:
Dakota 11,
Does the power go out in the rest of town when you kick that thing on? That is an extremely fast ramp time.
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No, but the lights flicker when the PID kicks on and off. I just walked up from my furnace which was preheating at 1200. It hit 1500 in 180 seconds. It is a small Lindbergh Blue.

I just heat treated some O1, I used the antiscale powder, worked like a charm. I think a lot of the crap that you see on an oil quenched blade is burnt oil. A buddy of mine left me some nice oil quench and even the areas that didn't receive antiscale are pretty darn clean. This is with the argon off, I don't use it much any more. I just stuck the hardened part in the kitchen oven with dinner. Wife says "what was that?" "Nothing dear".

I just put in some D2. I use the 309 high temp foil for that. I'm nursing a wound as I type. I know the stuff is gonna cut me, but I wait until I'm bleeding to scratch around for the Kevlar gloves. Feh..
 
Thanks for the dimensions/placement info, Dakota11. That's a helluva nice heat-up time; I like it! Did you paint the inside with a refractory of any kind?
 
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