annealing medium

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Dan Rasmussen
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Joined: Thu Mar 20, 2014 7:19 pm
Location: rose creek mn

annealing medium

Unread post by Dan Rasmussen » Tue Feb 24, 2015 7:20 pm

Wondering what some of you use for a annealing medium. In the past I have used wood ash's, but during my shop remodel my annealing tub got thru out. Need to anneal some pieces and would appreciate any help.


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Darryl Ponder
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Joined: Sun Feb 10, 2013 12:10 pm
Location: Minnetonka, MN

Re: annealing medium

Unread post by Darryl Ponder » Tue Feb 24, 2015 8:23 pm


I use a five gallon metal paint bucket, with lid, full of vermiculite. Vermiculite is sold at some plant nurseries and is used in gardening. It is a very light weight material and insulates well. Some smiths talk of making a "steel sandwich" by placing the object to anneal between two larger items, bring them all up to critical temperature, then place the "sandwich" into the bucket of vermiculite and let it cool slowly to anneal. My experience is that this works OK on simple steels. I have not tired it on anything but simple steels. I'm hopeful some of our experienced bladesmiths or metallurgists will drop by this conversation and educate us on annealing various steel alloys.

You can always look up an alloy and see what the manufacturers recommend for temperatures and times to hold at a certain temperature, cooling rates and times, etc., for a full anneal. That takes a temperature controlled oven and I don't own one.

Note that vermiculite is a silicate and one should not breath the dust.

Good luck making soft(er) steel!



Martin Pansch
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Joined: Thu Feb 14, 2013 10:44 am
Location: Young America, MN

Re: annealing medium

Unread post by Martin Pansch » Tue Feb 24, 2015 10:53 pm

Pete Stanitis did a Metalsmith article a while back on annealing in wood ash. Volume 29 Number 1 from 2005 according to the Metalsmith index. If I was home at the moment I would scan and attach it for you.

I use the vermiculite as well. I used to use wood ash and I found the vermiculite holds the heat in a lot longer. Though that is just how it appears, I haven't done side by side tests with ash and my thermocoupler like Pete did.

When you actually read some of the manufacturer's specs for a full anneal on a lot of these steels it is generally asking for temp/time control most our shops are not capable of. If I remember correct O-1 asks for cooling it from 1450 to 1000 over 10 hours or so. Very difficult to pull off without a programmable heat treating oven, especially for thin cross sections of steel like knife blades. After slagging a number of drill bits trying to put holes in not-fully-annealed O-1 I found a few tricks that worked for me.

First is what Darryl mentioned, making a steel sandwich. I had a few 1/2"x2"x10" pieces of steel I heated up along with the blade, made a sandwich and buried in ash. This did work better for me than annealing the blade alone judged by the sharp decrease of ruined drill bits. This works fine for flat pieces like knives but not if you making gouges or other odd shapes I expect it will be less effective.

In the winter I had a colder shop so the steel would cool faster than I would like. Luckily for several reasons, I had a big barrel wood stove. So I would make a steel sandwich like above and stick it in the ash in my stove under a nice bed of hot coals with some burning logs on it. It would take the fire a few hours to die down before the steel had to worry about the icy hand of old man winter.

Another method I have seen is people just heat an item up in their gas forge, turn it off, close it up and let it cool down in there. If you have a rammable refactory or a lot of hard fire bricks in your forge it should hold a lot of heat. Same thing if you have a big piece of steel you are annealing. If your forge has more light refractory like kaowool or you are annealing small pieces of steel you might need to cheat it a little by putting a few heavy pieces of steel in and get them up to temp to use as heat batteries.

For slow cool down of large, odd shaped things I have been known to give them a wrap or two of kaowool as an insulator. Of course, I have mostly done this when slow cooling cast iron pieces I had to braze like blower casings, etc.

All that said, I don't anneal nearly as much as I used to. I pretty much now just anneal something if I need to drill it or something else that I really need it soft for. For most of my struck and cutting tools now I just normalize them 3 times to try to make the grains a uniform size and relax some of the stress from beating on it. Then I grind as needed. Then heat treat. Not sure if it is a better way but it is what I am doing now after reading some things and talking to some people.

Like Darryl I would love to hear from someone who knows what heck they are talking about. Maybe Jim Moenck, Paul Wiedenhoefer, or maybe even Mike Blue will stop in and offer an opinion.

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Re: annealing medium

Unread post by Ashurbanapol » Wed Feb 25, 2015 12:40 pm

I wish I could remember the man's name, but a man from Alaska told me how to anneal H-13, S-7. A-2 and similar alloys. You heat the metal in a gas forge to a the forging temerature, stop up the forge at the end of the day and let it cool in the forge. It has worked great for me. If you put it in vermiculaite it tends to get hard, and wood ash or lime as well, and this method has worked for a lot of tools I've forged, plus it is very simple. You can anneal fairly well on water and oil hardening steel. Realize none of the methods are true annealing, which requires making the steel absolutely as soft and stress free as possible, and which can be done in a proper heat treating furnace programmed to cycle the metal as the manufacturer recommends.. But practically we can do decent work with simple methods. I like to make my H-13 and S-7 tools soft on the back and heat treated on the front. I first make them all soft as above explained to stress relieve them, then take firebrick and either drill holes or make a slot the tool will go through, heat the front up for the required time not heating the back, take it out and air cool, then put in a toaster or other oven at 400" for an hour on small tools, a little longer on larger tools.

Jim Moenck
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Joined: Sun Feb 10, 2013 5:23 pm

Re: annealing medium

Unread post by Jim Moenck » Fri Feb 27, 2015 8:00 am

Dan, I agree with what the others have said. There is not a "one answer fits all" issue here. I recently had a run-in with the W2 I was working with. I could not get it to a satisfactory and uniform hardness when I tested it on a Rockwell tester. I reached out to the knife making community for some help, and the answers turned my whole process around.

Each and every steel has it's own intricacies. There are many places online to get the heat treating info on any given steel. If you have any hope of having repeatable success, you need to follow the guidelines for the steel you are working with. In my case, what I was doing in step 2 affected what I did in step 4. Step 2 was entirely wrong, and I just set myself up for disappointment. I used to do like many others. When I was done forging a blade, I thermo cycled it a couple of times, put it in the forge, closed the forge up and let it cool slowly. I assumed that it was annealed when I took it out. Wrong. What I learned was that I had to get the grain size uniform in the beginning of the annealing process. In the case of W2, I brought it up to 1700 degrees for 10 minutes and hung it in still air to cool. Next I lowered the temp to 1500 degrees for 10 minutes, then hung in in still air to cool. Next I dropped the temp again to 1300 for 10 minutes and shut the oven off and let it cool overnight. When I took it out the next morning, I went to the grinder and got the surprise of my life. It ground like butter! I rough ground 12 blades on a 60 grit belt, and the belt was still almost like new when I was done. This made a true believer out of me; follow the recipe for the steel you are working with. When I did the heat treat on these blades, I reached a uniform and acceptable RC of 61 - 62 on all of them throughout the blade.

I do have a Paragon heat treat oven, which is almost a must have if you are serious about precise heat treating. And what I want to emphasize here is that you don't have to have high tech equipment, but it sure helps. When I take out a known steel at 1400 degrees, I study it for color, just for future reference for work done in the forge. There are a lot of good blacksmiths who do heat treating (which annealing is a part of) with their forges or torches. Learn the metal you are working with. Experiment with it, try different things with it, get to know it. Try to work with known steels and follow the known heat treat methodology.

I hope this helps a little. If I can help in any way, just call me.

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