1095 and O1

[Eli Jensen]

So this is my first go at my own heat treating and I want to do it right. I have a pretty shabby tool shop with almost none of the equiptment that most people use to make knives. I use an angle grinder free hand and a 4x36 stationary sander. I'm able to crank out decent blades for a poor, ill equipt, young lad in school.

My first question is, my blades go through quite a bit and can get hot while working them. I've read I should then normalize them? How do I do that and when should I do it?

I know I may be scolded for this method, but I am planning on heat treating them on a campfire. A very well controlled campfire with trenches and grates and such so there is air underneath. I also plan on very carefully controlling the wood disribution and wood type. Wish I had another option, but its this or texasknife, which is the too expensive option (although they do a dandy job and have no complaints with them.)

So then when I am heating the blades, 1095 needs to be a bit hotter than O1 right? I think I read its about 100 degrees or so higher than non-magnetic (I am going to go off of color (at night) and a magnet)? How long should the blades soak at their respective temperatures? I read somewhere that at such high temperatures, the steel can decarburize and lose carbon. Will this happen if they soak for 10+ minutes? Can decarburization occur durring normalization? Is there anything I can do about it (foil maybe? but then I cannot judge by color and need a much more powerful magnet)

I plan on doing a file test to see if my heat treat works, but I also hear that a dry/ice cryo can help mitigate a bad heat treat, and improve the steel in general. I've heard that 1095 should be tempered once before cryo, does O1 need a temper before cryo to prevent cracking? Should I temper once or twice after cryo? How long at what temperatures?

Back to the forest furnace, anyone know what woods would be best? Would charcoal briquettes help? I have available Ponderosa pine and possibly juniper, aspen, and oak. I can also get cedar but could that burn too hot maybe?

Thanks ahead of time!

[son_of_bluegras]

I tried replying yesterday and had trouble, so I'll try again today.
I may even get all the points I said yesterday.

A "camp fire" should work fine and depending on the conditions, additional air may or may not be necessary. You should let the wood mostly burn down to charcoal and if you do the wood type won't matter much. However charcoal briquettes are next to worthless, they are pressed and contain stuff to slow the burning of the briquette. Such a fire may have inconsistencies when heating the blade, that can be mitigated with the use of a muffle pipe. Do a search if you don't know what I mean by that.

I don't use O1 so I don't know the details of that, but is has alloying elements that aren't in 1095. Some of those, I think, mean the O1 can stand to get hotter than the 1095 (maybe needed) and the O1 needs a soak at temperature to get everything out of it. For the rest of this, it is based on my experience with 1095 and may or may not apply to O1.
You'll want to take the 1095 around 100 degrees hotter than non-magnetic. If you get a lot hotter you'll get grain growth which is bad for a knife. If it is dark enough, you may be able to see a "shadow" pass across the steel when you heat it. That is the steel removing heat energy to undergo the phase change. For 1095 when the color gets back to the color just before the phase change, you are pretty close to the temperature you need. A very short soak will be good to ensure complete dissolution of the carbon. By very short, I'm talking 15-30 seconds. For a campfire type heating arraignment, if you try to soak much longer than this you risk getting hot enough to suffer grain growth.

You should normalize 2 or 3 times. To normalize, heat to critical (just above non-magnetic) then allow to air cool to magnetic or cooler. This will relieve stress and refine the grain. You can use the cooling time to watch for the above mentioned shadow to determine the color you need to see.

Unless you really mess things up the decarb will be mostly on the surface. Because you'll need to do some finish grinding after the heat treat, decarb isn't much of an issue. On a related note, leave the edge 40 thousands or so thick (about the thickness of a dime) when you heat treat. This will reduce the risks of warping and cracking of the blade.

As for the cryo, it won't help a bad heat treat. If may improve the blade a bit. See the recent threads below in this forum on cryo, there is a lot of good information there that will take too long to type.

I don't see what quench medium you plan on using. Oil will work, I use old cooking oil. I don't like motor oil but some use it. Water can be used for the 1095 (don't know about O1) but it increases the risks of a cracked blade.

The tempering temperature depends on what you want to use the blade for. I temper to 325 F for an hour twice. That leaves a really hard blade that will slice very well but won't hold to chopping or prying. For a chopping blade, 450 to 500 F is a good place to start. For prying, get a pry bar.

I've probably missed something and may have raised more questions. Feel free to ask.

ron

[Eli Jensen]

Thanks for the tips. I'll look into the muffle pipe, but otherwise I'm very confident I can make the fire work as well as it can for something like this. I'm doing it at night so it should be dark enough. That is unless moonlight can change that? Never done this before so I dont know. Same thing with the shadow thing, probably one of those things you are confused by until you actually see it and makes sense. I'll read up on that too. I think I'll do the air trench anyways just because it'll make it faster for me to build the coals and allow somewhere for the spent coal to go.

I am also perfecting my grinding and have found that now that I know how to do it right, its a lot easier to do it right the first time than to fix one I did wrong. So I'll have a few blades that I won't mind getting messed up, and all that normalizing will give me practice for the shadow thing.

And yes I plan on using vegetable oil. I hear olive oil is better because then you can think about baking cookies, but $$$ . . .

Is the tempering time the same for 450-500 degrees? Just out of curiosity, what does tempering multiple times accomplish?

About what temperature is the "oh s@%#" temperature for going too hot? I can maybe tell by the color. Weird thing, I'm red-green color blind but I do way better than most people on shades of red (still can't tell blue from purple or green from brown though)

Thanks again

[son_of_bluegras]

With real charcoal (read from wood not pressed briquettes), you don't have to worry about spent coals. You get some ash, but if you supply additional air, the ash is fine enough to be blown out of the fire.

As for moonlight changing thing, any change in ambient light will change things. If you haven't developed your technique for a particular lighting condition, changes in light won't matter much so long as you can see what you need to see well enough. Full sunlight is bright enough I can't see any incandescent colors when critical is reached but at dusk I can.

I've read fome reports that show where canola oil has a very good cooling curve for carbon steels. I hear peanut oil works very well. What I use is a mix of animal fats and vegetable oils collect from my own frying pan. It's worked well enough for me.

The tempering times aren't as critical as temperature.
Multiple tempers are good, particularly for higher carbon steels, because there can be some retained austenite after quenching which the first tempering cycle may convert to martensite which will then be untempered. The second tempering cycle tempers any fresh martensite. Mostly it is insurance.

On the "too hot" question - for tempering or before quenching? You want to stay out of orange or yellow (depends on your eyes and ambient light) before quenching. For tempering yellow to brown is good, somewhere around 400 to 425 the steel with start to show tempering colors with light yellow being first. Tempering colors can be different if there are any oils left on the blade and will darken with time and maybe level of finish on the blade surface.

If you find you have a bad heat treat, 1095 can be heat treated again a couple of times.

ron

[Eli Jensen]

Thanks for all the help Ron. Now all I really have to do is to find a day (maybe when its warmer, or down by Phoenix. I am luck that I work for the schools entomologist and we do a lot of bolt (log) studies with beetles so there are a ton of multiple sized logs with no bark that I can take! Thats good cause the ponderosa bark is fire resistant and burns slow and dirty.

I guess my only other question is how can I lay the knife on the fire? Do I stick it in the coals directly? Flat or vertically? On a grate?

[son_of_bluegras]

I go vertically and edge up. The edge will heat faster than the rest of the blade. To get even heating you may need to pull the blade out for a second or three to allow the edge to cool then back in the fire.
Directly in the fire is fine. If you use a muffle pipe, then in the pipe.

ron

[WBE]

As far as the temper, use your oven with an oven thermometer. Going by color is very iffy, and you will get a much better temper if the blade is soaked at temp for a while. 2 hours twice, cooling to room temp in between will get it done much better. Even better if you bury the blade in dry sand. That will off set your oven thermostat heat flucuations.

[Eli Jensen]

Good idea on the sand. I've got an old gas oven so thats probably a really good idea. I've heard about people wrapping blades in foil for tempering, is that necessary?

[Doug Lester]

Wrapping a blade in foil, stainless steel not aluminum, is often used when heat treating stainless steel and maybe some other high alloy, air quenching steel. These steels often have to be tempered at temperatures well above what is possible with the kitchen oven and the wrap protects the steel from the effects of oxidation. It's much cheaper than building an electric oven that can be given an argon atmospher.

Doug Lester

[Eli Jensen]

Good to know.

One more Q - Is there such a thing as cryo treating with dry ice for too long? I've heard anywhere from 4-12+ hours. I've heard that its very important to let it slowly warm to room temperature after, so my plan was to make a dry ice/acetone bath in a foam cooler and just let it sit there until it all sublimated out. I'm a student and busy a lot so the extra time wouldnt break my heart.

[son_of_bluegras]

The long times I've heard for cryo are for alloy steels. The O1 may benefit from a long soak, I don't think the 1095 will benefit from a long cryo soak. What you are trying to do is convert the retained austinite to martensite. That conversion happens very fast once temperature is reached.
Have you read the threads on cryo below in this forum?

ron

[Eli Jensen]

I have. What I want to know if its in there too long will it hurt it? It would be easier for me to put it in there and forget about it for a few days, with the idea that it will slowly warm up as the last bit of dry ice sublimates and the knife is still insulate in the cooler and in the acetone. That would be easier for me that messing with warming it up slowly after a designated time.

[WBE]

There is no benfit from cryo treatment of 1095, and very little to none for 01. It is not worth the effort for either of these steels. Foil wrapping is only used for the hardening process, mainly to prevent decarb and scale from the high heats used in hardening stainless and high alloy steels. In tempering even these steels, the temperature is not high enough to need foil.

[Eli Jensen]

I've heard that there is no benefit, I've heard that there is some, and I've heard that there is. I guess the only thing I can do is to test it out myself.

Does anyone know if elevation (say 8,000 ft) has any effect on any of this?

[son_of_bluegras]

I don't think elevation should affect the process in any way.

ron