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How do you anneal?

go mike

go mike

Joined
Dec 5, 2008
Messages
1,597
I may have a source of 1075 steel, but it is in hardened, large chunks. I will be getting a fire brick built, propane forge, if that means anything. I read that it has to get to about 1250, and cooled at 50 degrees per hour until 1000, then air cooled the rest of the way. If I did this, would it get down to a low enough rockwell to not destroy my equipment?

Also, would the best way to hold the temp up be to just shut the propane off, and let it cool inside the forge, or use the kitty litter idea, of covering it up overnight?

I want minimum carbon loss, and I don't know much about decarburization, which I read happens when steel is hot for a while.



Thanks for any info, I just haven't found very much information on what steps need to be taken to anneal steel. I can accept if I sound like an idiot for asking.
 
What I do is heat to critical temp then bury the steel in kitty litter (although vermiculite is commonly used and recommended) and just let it cool slowly... Pretty simple.
 
I can anneal 1095 by heating to red and then air cooling. Why do you guys do the triple anneal? Seems like a wate of time to me.
 
Bill,
Yes heating to non-magnetic and cooling 1095 in air will make pearlite, but the structure type may not be the best. Cycle annealing to get a spheroidal structure will give you the smallest grain size, and the best structure to work from. The end result of the blade (when finally hardened) is a product of where the structures started out. Kevin covered this in his hyper eutectoid stickie, IIRC.

Mike,
For discs that size, you probably will have to cut them up into manageable pieces before you can put them in the forge. A person with a plasma cutter can slice them into 4" wide strips, or you can do a back yard anneal to soften them somewhat, and cut them on a metal cutting band saw. Making a good bed of coals in the BBQ ( maybe use an old hair dryer to add some oxygen), getting a disc up to red hot, and burying it in a metal bucket filled with vermiculite ( or clay type cat litter) will soften it good enough to cut. After it is in manageable pieces,I would get it into good shape (internally) since you don't know anything about the last HT.

Heat it in the forge to non-magnetic, and let it cool in the air till black. Heat again to a little above non-magnetic, and quench in oil. Cool for 5 minutes. Heat again to just non-magnetic ( observe the color), and let cool in the air till black. Heat to a little below non-magnetic ( a little less red) and cool, repeat again a little lower heat ( dull red), and stick in the vermiculite/cat litter. The next morning the steel will be fully annealed, and have a good structure to work from.

If you are filing/grinding, this is going to make your life much easier. If you are forging, it is not as necessary to do all this first, but still a good idea with unknown condition steel.
After you forge any blade ( regardless of the steel source), the blade should be run through this procedure before filing/grinding. This will ensure good grain structure, and a soft condition. It will prevent many warp and crack issues later. At final HT, a quick cycle (or three) to non-magnetic and air cool, will normalize any final stress produced in grinding.

I know there are makers and smiths out there who are saying," I never would waste that much time on a blade before I even grind it.", but the time spent getting the steel prepared before the knife gets made is when the blade is being born. A lot of what it will be later starts here. Would any of you tell the doctor delivering your first child, " Just yank it out, Doc, I ain't got time to waste standin' around here watchin' it come out nice and pretty."

Stacy
 
If it was me, I'd find someone to plasma cut it into useable strips then anneal. Lots easier to handle that way. I use a lot of big sawblade material and found that is the way to go(strips). A whole buncha strips fit better into my annealing box than big chunks of steel.
 
Bill DeShivs said:
I can anneal 1095 by heating to red and then air cooling. Why do you guys do the triple anneal? Seems like a wate of time to me.
Click to expand...

The way I learned it, Bill.

To soften hardened steel to cut/grind/drill, an easy thing to do is spheroidize anneal. In a kiln, a temperature of 1250 +/- (near, but below AC1... the point the steel will start making austenite) for an hour and air cool will work well enough on hardened steel. It's a high temperature temper... the carbon balls up. If I've got a forge, holding an even heat at the specific temperature for an hour is going to be tough to do. Heating the steel to the temperature a number of times with air cooling inbetween will spheroidize the steel well enough and is a lot easier to handle with a forge.

I've never tried to spheroidize hardened steel by heating it once to below AC1. Would you describe your process?

Mike
 
Stacy: Thanks for the detailed process. That's something that I couldn't find. Although, I didn't know what eutectoid meant either, so if I did see that thread, I wouldn't know what it was talking about. I was planning on cutting the discs in half with either a plasma cutter, or with an angle grinder. :)
 
I make leaf springs that are subject to thousands of cycles. I have NEVER had one fail.
I buy annealed 1095, cut and shape the spring, heat to cherry, quench in room temperature canola oil, clean to bright metal, and temper to just past blue. I use a propane torch and firebrick. I heat treat stock removal blades in a similar fashion.
I also occasionally use O1 with the same treatment.
 
The question of carbon loss came up in discussion of this thread.
here are some thoughts:

Carbon loss is a product of time and temperature. At the temperatures I was talking about, from 1100F to 1400F, there is no concern at all. Above, 1600F, carbon can combine more easily, but carbon loss is not a real issue unless you greatly overheat the steel and hold it there. I will forge 1070 steels for dozens of heats, all around 2000F, and the final carbon content is maybe 3-5 points less. It is a common mistake to think that carbon loss is a problem with simple steels, like 1070/1084.
The thing that can, and will, create carbon loss is having the wrong forge atmosphere. If the flame is running with too much air, it becomes oxygen rich, and will combine with the carbon into carbon dioxide. Having a neutral flame will make for little worry, and a carburizing (reducing) flame will actually add some carbon. This is one of the biggest reasons to build a blown forge. It will allow the air/fuel mix to be adjusted easily, to control the atmosphere. My two-stage burner control design will allow constant atmosphere control and exact temperature control ( often to +/- 5 degrees, or less)

Stacy
 
If you go read that thread especially the post by, Kevin Cashen, you would learn what it is and a whole lot more. Not only how to anneal, but, how to set your steel up so that when you HT you get the very best results after HT. He uses descriptions that make it simple and make sense. He has put a tremendous effort into this and if you want to make some serious knives I can not recommend anything more important than these threads. The best steel, the best grinds and shapes are all for nought if you don't make the best of the HT. Yes, getting it hot enough and quenching it well will make it hard, but, that is NOT the whole story and he explains why VERY well. Jim
 
I guess my method isn't scientific enough, but it works fine.
If I have to anneal, I just heat to red and air cool. It's been done that way for hundreds of years.
 
Bill DeShivs said:
I guess my method isn't scientific enough, but it works fine.
If I have to anneal, I just heat to red and air cool. It's been done that way for hundreds of years.
Click to expand...

Bill, I have no desire to disagree with you or oppose your method of doing things since it obviously works quite well for you and if you have found success for your applications I would be a fool to try to mess with that, nor should you let me. What I really want is to offer some counter points to the argument that "It's been done that way for hundreds of years" which is not at all unique to this conversation but is indeed quite prevalent in our field.

First however one point that may be confusing participants in this conversation is the interchangeable use of normalizing operations and annealing. I know of nobody who anneals more than once, but multiple normalizing cycles can be of great benefit. Normalizing involves air cooling for the purpose of refining the internal condition of the steel. Annealing involves slower cooling than air for the purpose of softening sand stress relieving the steel. Technically only nonferrous metals can actually be “annealed” by air cooling, air cooling steel by definition is normalizing.

Now back to the appeal to the authority of tradition argument, rather than directing my dissent to you I would rather urge the bladesmithing community at large to please reconsider this very flawed argument for techniques. Virtually every field of exploration or endeavor for mankind, outside of knifemaking, holds up the amount of innovation it has seen over the centuries as a sign of progress or quality. Which is more inspiring, a technology that boasts huge advancements in the last century or one that can say it hasn’t changed a bit for the last several centuries? The latter is most often a good recipe for extinction. When we seek out a surgeon do we want the guy who embraces all the advancements in medicine he can or a guy who believes leaches and banishing bad air spirits still works as good as it ever did?

We may argue that those traditions are more the heart of the craft than the product itself, but this would bring us to the most problematic aspect of the stance that "It's been done that way for hundreds of years" which is- it hasn't, at least not by any field that managed to keep up. Aside from all of the appeals to or dissent from tradition the one critical point that doing things the old fashioned way does not take into account is the evolution of steel.

The old ways worked not for hundreds of years, but thousands of years, however alloying and modern steel manufacturing changed everything. Simply applying ancient techniques to modern alloys is like working on a computer with a hammer. Heating and air cooling simple iron and carbon alloys from hundreds of years ago could actually approach annealing operations, however even our simplest carbon steels today contain copious amounts of manganese and multiple trace elements. Modern steel making methods changed everything, other metalworking fields that adapted to these changes became the driving forces in industry while those who rigidly adhered to tradition were left behind.

Once again please do not think this is about you in any way, you seem to be doing fine, but the appeal to tradition position is very, very common yet terribly flawed, and I have the best of intentions in hoping folks would abandon it for a better reasoning. :thumbup:
 
Kevin
I agree that research and development should be embraced.
That said, if I heat and air cool, and that softens the metal, why go further?
 
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