Heat treating O-1 in Charcoal?

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GIFF07

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May 10, 2004
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This will be my first time atempting to heat treat any metal. I have made a couple of knives by the stock removal process and was thinking of getting some O-1 to experiment with. I was planning of filing and sanding my blade shape, then placing the blade in the lit charcoal until it is non magnetic. At that point I would quelch it in a brine. Then I would put it in an oven at 350F for 2 hours to temper. Does this process seem like it would work?

I also am wondering if I use the charcoal chimy for heat treating the blade, will I have to worry about any residues left by the metal if I want to use it to light charcoal for cooking? I would not use the same charcoal that I heat treated in to cook with.
 
Quench in oil , not brine . The O in O-1 means oil quench.There will be no residue left by the metal. You may need a blower to get more heat.
 
What you are attempting to do is drive your car at night with the lights off. With the process you have described you have no way of knowing what you will end up with quality wise. Do whatever you can to heat treat with more control over temperature and time or have someone do it who has the right equipment. I'd hate to see you work that hard to manufacture the knife only to fall short on the heat treatment.
 
I've HT'd 1095 in a charcoal grill (twice -- the first time I warped the blade), and it seems to have worked. I'm waiting to fully sharpen it until I have a handle on it, but I did sharpen it up a bit (I left ~1mm on the edge before HT'ing because I was worried about cracking). Comparing it's feel to that of other knives on the waterstones, it's probably in the high 50s. I think I quenched it just a bit early, because I was worried about overheating it.

Anyway, the point is, yes, you can.

What Satrang is saying is partially true. People have been making knives and swords for hundreds of years, and they never used to have all these modern forges. You CAN use a charcoal grill, and you CAN figure out what the color means. I've started to be able to recognize how the color changes as it heats up in my grill, after several normalizing sessions and two heat treats. I feel pretty confident that I could get pretty damn accurate just judging by the color.

On the other hand, it is difficult to get the heat all that even, which is why I warped the blade during my first attempt. Getting uniformly shaped charcoal helps a LOT. I used hardwood chunks the first time, and it was much harder. Get the charcoal hot and place the briquets in two lines, with just enough room between them to fit the knive in, edge down. You may need to stack the charcoal, depending on the height of the knife. When you heat up the knife, occassionally move it a bit back and forth, because the charcoal will touch the blade in some places but not others.

If you ever warp a blade, and you should expect that you will, remember that you can normalize it (heat it up past non-magnetic and let it cool in the air), bend it back, and try again. If you ever crack a blade, you can still use that metal to practice heat treating some more.

You may want to make some really simple, quick knives just to practice with.

Good luck!


EDIT: I should note that when I say I've HT'd 1095 twice in a charcoal grill that's all the steel I've ever HT'd in my life. Hope it didn't sound like I knew more than I actually do. Most of the stuff I'm spouting is all stuff I've read or assume from limited experience... :p
 
I agree with Satrang in that it sounds like he was just going to stick the blade into the coals and find it at some point to be up to temp.

You can make charcoal to use fairly easily... you'll need some chunks of wood and a barrel to "cook" it in.

You WILL need to use a blower to get the coals hot enough. A hair-dryer can work, but you have to be careful that you don't melt the darned thing.

Just lighting a bbq full of coals isn't going to be adequate.
 
brash said:
snip

On the other hand, it is difficult to get the heat all that even, which is why I warped the blade during my first attempt. Getting uniformly shaped charcoal helps a LOT.

snip
Click to expand...

I had trouble getting even heat untill someone mentioned using a pipe. What I'm doing now is placing a piece of pipe (non-galvanized) in the coals putting some on each side and some on top (someone has mentioned using kaowool or similar on the top to reduce fuel usage, haven't tried that yet). When the inside of the pipe heats up the temp inside will tend to uniformity making it much easier to get an even heat. I place the blade in the pipe spine down and hold it there with tongs of course (using 1095 which doesn't take long to heat). In proper lighting conditions, I can even see when the blade undergoes the phase change which indicates critical temp. I find I can, with care, HT a blade just a shade longer than the pipe I have.
 
son_of_bluegrass said:
I had trouble getting even heat untill someone mentioned using a pipe. What I'm doing now is placing a piece of pipe (non-galvanized) in the coals putting some on each side and some on top (someone has mentioned using kaowool or similar on the top to reduce fuel usage, haven't tried that yet).
Click to expand...

Wow... I'll be trying this on the next knife I HT. Thanks!
 
Thanks for the replies, a charcoal chimany is like a pipe but with holes in it to acheive better air flow http://www.naturesownonline.com/sho...=25&prevaction=category&previd=10&prevstart=0. The reason for the brine was I was going to follow this procedure: http://www.navaching.com/forge/heattreat.html I felt a little uncomfortable quenching in oil (oil fires are not fun but I am going to have a fire extinguisher handy). I will have to pick up that $50 kinfe shop book it seems right up my alley. I don't think I am ready to invest in a forge yet. I have no professional aspirations (yet):D .
 
I'm curious why O-1 should be quenched in oil rather than brine. (I mean the science behind it, not just that it has an "O" in the name...) Actually, a more general question I hope someone can answer too: what are the different properties of oil and brine as quenchants?
 
brash,

those question take up books all by themselves. A good overview can be found in a couple of chapters (6, 7 and to a lesser extent 9, 10) of "metallurgy Theory and Practice" by Dell K. Allen.

The short answer is the chromium in O-1 is principally the reason it is oil hardening.
I don't understand it well enough to give a coherant longer answer. Any metalurgist out there????

As for quenchant properties, the important factor is speed of quench with the order fastest to slowest is brine, water, oil, air. There are other things that can be used (lead, molten salt), but outside of industry they ain't common (may not be common there).

The problem with using too fast a quenchant is the surface is the point of heat exchange and if it cools a great deal faster than the inside (getting into thermodynamics here and that can be a lifetime of study in and of itself) it can crack or result in internal stresses that will result in premature failure.
 
Okay, you convinced me to use an oil quenchent, would about a gallon of motor oil be good enough? I plan on heating a small piece of metal and toss it in to heat the oil up a little. If I do the oil quenchent do I have to do all the waving the piece around ect that was in the little how to guide I had posted before, or should I just dip it in the oil and then put it straight away into the oven to temper? Remember you are talking to a beginner with limited equipment. I do have a K-type thermocouple I was planning on using for reading the temperature of the oven for tempering and probally the temperature of the piece after it comes out of the quench. It will not read high enough (only goes to 1300F) to control the temperature of the heat treatment.
 
A gallon should do for a small knife .Heat the oil to about 140F. Move the knife around in the oil. .....Steels are listed as to their 'hardenability', that is how deep [from the surface] the steel will harden when quenched. A 1050 will be a very shallow hardening and an A2 will be a very deep hardening. Quenchants are separated according to how fast they cool the steel . In general from the fastest ; brine, water,oil, air.
 
This post brings me back to my first knife, over 30 years ago. 01 steel, heat treated in my dad's charcoal grill. I didn't use a blower, just placed the knife in the brickettes until it was a nice, orange color. Quenched in warm vegetable oil. Came out fine, except for the raised areas on the blade wherever it touched the charcoal!!!!
I think the carbon content in those areas was probably close to that of cast iron!

Anyway, I finished it up and it cut. Plenty hard, and brittle, too, but it cleaned a few deer until it was lost in the woods.

Now, I've got a $3500 furnace, full cryo capability and a hardness tester. And a degree in Materials Engineering. See what happens when you get hooked on knifemaking? :D
 
son_of_bluegrass said:
The short answer is the chromium in O-1 is principally the reason it is oil hardening.
Click to expand...

Thanks! This is a good starting point for me to do some research. :)
 
GIFF07 said:
Thanks for the replies, a charcoal chimany is like a pipe but with holes in it to acheive better air flow http://www.naturesownonline.com/sho...=25&prevaction=category&previd=10&prevstart=0. The reason for the brine was I was going to follow this procedure: http://www.navaching.com/forge/heattreat.html I felt a little uncomfortable quenching in oil (oil fires are not fun but I am going to have a fire extinguisher handy). I will have to pick up that $50 kinfe shop book it seems right up my alley. I don't think I am ready to invest in a forge yet. I have no professional aspirations (yet):D .
Click to expand...

I took a look at the procedure listed above and must say I'm not impressed. While it does appear it would work, it would just take a moment to long in brine to crack O-1. I know you've already decide on oil, but had to get this out there.

And don't think the colors he shows are accurate. With thanks to alvinj over on rec.knives

http://www.panix.com/~alvinj/ron.temperingcolors.jpg

This is a photo of the oxidation colors for tempering. As opposed to the created scale he has on his site.


As for the incandesence (sp) of forging temps, ambient light makes a world of difference.

On fires: they need 3 things; heat, fuel, and oxygen. without all three, no flame. The fuel necessarily must be a vapor. The hot steel is hot enough to vaporize the oil, but if all of the glowing steel is below the surface of the oil, then no oxygen for fire. So by plunging the knife completly under the oil surface you minimize the risk of a flame up. I personally use used cooking oil with no problems.

As for a forge, they are easy enough to build cheap for charcoal or coal. I did it from scrap so invested some time only. The blower was given to me, but that to can be cheap (old hair dryer) or home-made.

http://www.panix.com/~alvinj/Ron.fairweatherforge.jpg
 
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