Nitpick my heat treat please

Redmeadow Knives

Redmeadow Knives

John Conner
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Knifemaker / Craftsman / Service Provider
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I recently purchased the Evenheat KF18 240V. I have always sent my stuff off to Pete's, so this is new to me. I have treated a couple of blades so far. I've checked the grain growth and it appears to be fine. I'm looking for opinions on my process. Any input would be greatly appreciated. I am using 5/32 O1 from Amtek. Below is what I have been using which is what I have learned mainly from this forum. Feel free to tell me I'm a mess.


Load blade into cold oven (Thoughts on this? Loading hot better? Loading temp?)
Ramp to 1200F
Hold @ 1200F for 10 minutes
Ramp to 1500F (Should 1200-1500 be raised slowly or on a full ramp?)
Hold @ 1500F for15 minutes (Too short, long?)
Heat Vegetable Oil to 120-140F
Vegetable oil quench (any tips on length of quench would be helpful, as in how cool should it be upon removal)

Temper at 450F for two hours (remove from oven until cool to the touch before 2nd cycle)
2nd Temper at 450F for two hours (around 59 hardness?)
 
Can't say for all of it, but preheat the oven to the desired temp and let it stabilize, then load the knives in. Otherwise they can grossly overheat during the ramping.
 
You might consider actual quenching oil rather than vegetable oil. I prefer higher hardness/lower tempering temperatures, but that's not for everyone. Also, look into the recent thread about quenching after tempering, typically in water.
 
Several things.

I'd recommend doing a heat soak of your oven first. Bring the entire oven up to temperature (1200F will work) and let it sit for 30-45 minutes before popping your blade in. This allows the entire mass to come up to temperature and decreases large swings as you austenitize at your target temperature.

If you want to do the preheat, I wouldn't worry too much about the ramp speed up to your austenitizing temperature. Just set it to your target and go.

Once the oven has equalized at your target temp, I would allow at least 2-3 minutes to allow your blade to be fully at temp, and then start your soak timer. One thing I learned with O1 is that a longer soak time isn't going to hurt anything. 15 minutes is probably just about long enough, but if in doubt, add another 5-10 minutes on to your soak. People run into problems when they only soak for 1-5 minutes. A long time ago, there was a thread here comparing grain size in O1 with various soak times. Bottom line, if you have tight temperature control, you're not going to hurt anything by holding longer (except for decarb), and it does allow time for all of the alloying elements to get fully in solution.

Vegetable oil will probably work just fine for O1 being that it is a medium speed steel that hardens deeply. Also, given the thin profiles we're dealing with, it should work just fine. If you want to use O1 for a long time, I'd recommend investing in some AAA quench oil. It works REALLY well for O1.

When I was using O1, I typically had a target temperature of 1450-1475F. I went a little lower than 1500F to try and reduce retained austenite, though the differences were probably fairly minute.

Keep good, detailed notes on your procedure for every blade you treat. Then do performance testing and see the differences, if any.

--nathan
 
Also, look into the recent thread about quenching after tempering, typically in water.
Click to expand...

I love this. I remember reading that thread and it tells me even the best and most learned are still learning. KROM!!!!
 
Never start with your blades in a cold oven. Bring your oven to temperature then let it equilibrate for 20 minutes to 1/2 hour then put your blade in spine down in a rack that holds it above the oven floor, I like to put a piece of lump charcoal in to create a carbon monoxide reducing atmosphere in the kiln as a guard against decarb and scaling. Canola may be too fast an oil for O-1 you want a slow oil which canola is not. Try Parks AAA or what I used to use for O-1 was 130 degree olive oil. Obviously the engineered oil is better. Do not use motor oil or transmission fluid

-Page
 
I do my 01 as follows, from a cold oven. Evenheat 22.5 oven. Rampmaster 2. Stock removal blades. Blades are edge up on slotted fire bricks and coated with ATP-641 after the stress relief heat. I do three at a time centered under the thermo sensor.
1 hr stress relief soak at 1250°. Air cool.
45 minute soak at 1250° for pre-heat, then ramp to 1400° for 10 minutes to allow oven to soak a bit, then ramps to 1475° for 20 minute pre-quench soak. Quench in Parks AAA at 130°.
2 + 2 temper at 425° to 450° depending on type of blade. There is no need to go beyond 1475° with hypereutectic carbon steels, for the quench soak. Checking with kiln cones, I have never found my oven to over heat to any noticable degree. If anything, it stops short and takes about 8 or more minutes to level up to the target temp.
 
O-1 is fairly flexible for HT. Starting out with a hot oven is better .Start at 1200 F to equilize the blade temperature. A long soak there doesn't do anything for the blade . Ramp up to hardening temerature .A long soak here is not necessary though a long soak won't hurt unless hardening temperature is exceeded.
 
Mete', I got most of that proceedure directly from KC, and the stress relief seemingly has greatly reduced warp.
 
So for stock removal the 1250F soak air cool before treat will relieve stress? Good to know. Is this stress strictly from my grinding or could the steel have stress in before? As in before I even received it?
 
Stress comes from grinding or even filing. Normally PG 01 is stress free when you get it, but working it adds stresses and they in turn can cause warp in the HT. If you were to fully bevel one side, then the other, rather than a bit at a time trading sides as you go, it is guaranteed to warp from the unequal stresses. There are many causes of warp, and stresses are one of them. Most warp that I get is minor and easily straightened by hand before the blade is fully cooled after quenching.
 
KC ? That guy again ?LOL I would have done the 1250 F ,inspected the blade and if no warp proceed.
The 1250 F is called stress relieve or subcritical anneal .It does both.It is possible to get stressed steel from the mill .Of course any working can stress it also.
 
Mete', that was my first thought also, but ol' KC insisted it should air cool after the stress relief heat, and then go through the pre-heat cycle before ramping up to 1475°. I don't mind extra steps as long as there is some chance of improvement, with no chance of harm.
 
I ran an hour soak at 1250F and let air dry. It came out with a thin coat of very flaky scale. I need to get a hold of some anti-scaling compound. Any recommendations other than ATP-641? I see Brownells carries it, I think I'll try some out.

Here are the changes I'm making to my program based on your recommendations:

Initial stress relief soak at 1250 for 1 hour. Let air cool.

Ramp to 1250F
Load oven
Soak @ 1250F for 30 minutes
Ramp to 1475F
Soak @ 1475F for 20 minutes
Heat Vegetable Oil to 120-140F
Quench
 
I think that would work very well, except I have no experience with vege oils and 01, and I would hang the temp of the oil at around 130°. You might avoid canola oil though. I believe it is considered a little fast for 01. I do not protect my blades from the stress relief heat, but use the ATP for the next steps. There is another anti-scale, but it has to be applied with the steel at about 600°. It is a powder that melts and bonds when it is sprinkled on. I tried it for about a year, then switched to the ATP. Much easier to apply and remove afterwards. The ATP is also cheaper per blade and coats and spreads much like latex paint. It easily washes off brushes with just water. The ATP first coat works best if allowed to dry over night. Then you need to inspect the blade for tiny places that may show through, and touch up if needed. I then use a second coat over the edge and point areas maybe 3/8" up the blade. For that first coat, the steel must be clean, and it helps if it is warmed maybe to around 110/120°.
 
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Thanks for the details LRB, much appreciated.
It looks like Parks AAA isn't the easiest thing to find.

Thanks for the replies and Happy Thanksgiving.
 
More like "almost totally eliminated warp" in my personal experience.;)
LRB said:
Mete', I got most of that proceedure directly from KC, and the stress relief seemingly has greatly reduced warp.
Click to expand...
 
So loading the oven when 1200 is reached for both the stress relief and the actual treat is best. Or simply put, loading a cold oven is never a good idea?
 
lessismore said:
So loading the oven when 1200 is reached for both the stress relief and the actual treat is best. Or simply put, loading a cold oven is never a good idea?
Click to expand...

I don't know for a solid fact, but I don't worry about it. My blades sit in the oven about 2" under the thermo sensor. I only do three at a time to keep them centered away from the coils. My oven stops about 10° / 15° short of target temp, and takes another 8 to 10 minutes of cycling to creep up on it. I do an extra step in between the 1250° pre-heat soak and the 1475° target temp with a 10 minute soak at 1400° to allow the oven itself to soak and equalize some. Probably not necessary, but it makes me feel better about it, and I can see no harm it doing so.
 
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