Annealing steel

Bruno · 05-12-2008, 12:59 PM

I got this from Mike Blue.
If you want to know for sure that a piece of steel is as soft as it can be, you have to anneal it before working on it. That way you can save yourself time and effort, since you cannot know how the steel was treated before it came to you.

You have to heat the steel till it is red hot and demagnetised completely. You can check this with a magnet.
At that point you immerse it in something that acts as a perfect insulator. Wood ash is a perfect material for this. Then leave it to cool off over at least 24 hours.

Be careful: wood ash is a perfect insulator. If you stick your hands in the ash after 24 hours, there is a real chance of burning your fingers really bad because the steel will still be hot enough to burn you.

Some practical points: you need a pair of tongs or vice grips so that you can remove the steel from the fire to check the temperature, and place it back if needed.

I was already firing the steel when I discovered this practical problem. Also, since I was abusing my smallish bbq for this, putting the big piece of steel back underneath the coals was a bit of a problem.
So I decided to simply stoke it as hot as possible, and then extinguish the flames by pouring a bucket of ash over the coals.

This was a partial sucess. Since I did not have a bandsaw, I simply used a hacksaw to cut off a strip of metal lengthwise for my first project (a Japanese style cutting knife for my mother).
As I was sawing I discovered that the part that had been in the core of the fire was noticably harder than that part outside of the core, which was also the part I could peek at through a hole between the coals.

Cutting all the way through took a lot of time and effort.
The nice thing about doing things by hand though (at least the first couple of times) is that it really teaches me a lot about the metal that I would never learn if I used power tools, because I simply wouldn't notice.

JoshEarl · 05-12-2008, 01:07 PM

Bruno,

This new forum is fun.

Tell me if you want me to shut up.

Before you try to anneal a piece of bar stock, it's worth trying to cut it or file it to gauge its hardness. If it cuts or files pretty well, then you might be better off just working it as is.

Some steels come from the mill in a super-soft condition, and once you heat them up you'll never get them that soft again without sophisticated equipment.

I recently forged a blade out of O1, and once it was ground I was unable to drill the hole in the tang. Forging takes the blade well above critical, and once it cools down again it hardens to some extent. I ruined several drill bits on it, and I've tried different annealing and softening treatments to no avail.

From now on, I'm going to use O1 for stock removal only. It grinds and drills like butter when it's new, but once I forge it it hardens up. Gah.

Josh

Bruno · 05-12-2008, 03:58 PM

Quote:

Originally Posted by JoshEarl

Bruno,

This new forum is fun.

Tell me if you want me to shut up.

Before you try to anneal a piece of bar stock, it's worth trying to cut it or file it to gauge its hardness. If it cuts or files pretty well, then you might be better off just working it as is.

I don't.
I did.
And it didn't.

I don't shy away from anything atm, because anything I do can only increase my first hand knowledge about steel.
I filed before and after, and it is definitely softer than what I started with. At least the part that was in the core of the fire.

JoshEarl · 05-12-2008, 06:35 PM

Here's a link to my ongoing discussion at bladeforums.com:
http://www.bladeforums.com/forums/sh...d.php?t=554489

Sounds like your steel was hardened to begin with, so annealing is a good call.

Josh

randydance062449 · 05-13-2008, 05:35 AM

If I manage to forge harden my blade then I always anneal it again before drilling the pivot hole.

Either drill your pivot hole right after the anneal or after the second anneal.

My grinders are almost done!

KenS · 05-13-2008, 05:45 AM

As a youngster in the 50's I was lucky enough to know a Welsh blacksmith whom had gone through an apprenticeship as a youngster. He would heat the steel in the forge, then put it in a metal box full of lime and close the lid. He swore by lime, and said it wasn't the only material good for annealing metal, but one of the best.
Ken.

Russel Baldridge · 05-13-2008, 05:58 AM

There are other options for insulators as well, you can get ceramic blanket on ebay, haven't tried it myself but it's supposed to work similarly.

randydance062449 · 05-13-2008, 06:15 AM

The ceramic wool blanket works well, thats what I use inside an old metal tool box.

Russel Baldridge · 05-13-2008, 06:26 AM

Great! I have had a 2'x1'x2" piece laying around for a while, maybe I'll give it a shot this weekend.

How much would be necessary to make it effective?

randydance062449 · 05-13-2008, 06:52 AM

I use 1" thick blanket, about 2 layers thick so I think you have more than enough. Just be sure to have the ends closed up.

Russel Baldridge · 05-13-2008, 02:44 PM

Great, I'll give it a try.

Yorkshireman · 05-13-2008, 10:51 PM

Quote:

Originally Posted by JoshEarl

I recently forged a blade out of O1, and once it was ground I was unable to drill the hole in the tang.

What I generally do is to punch the holes at red heat with a pritchel. It is the traditional way in the cutlery industry - holes were rarely drilled in the old days before stamped out blanks and stock removal - just look at the dot (pivot) holes of old Sheffield razors.
If you use a pritchel with a flat, round end of about the right diameter rather than a pointed one, you can start the punching on the face of the anvil before moving over the pritchel hole. This will punch out a little disk, distorting the surrounding tang less than if you simply poke a hole through with a pointed pritchel.
I hope this is of some use. If I have just taught your granny to suck eggs then I apologize.

Duncan.

JoshEarl · 05-13-2008, 11:19 PM

Duncan,

I'd like to try that, actually. I tried to use a punch from Home Depot, and it just bent.

The trouble is that I don't use vintage-style pivots, so a precise hole is desirable.

Does the tang get bent at all when you do it this way?

Josh

Yorkshireman · 05-14-2008, 12:56 PM

Quote:

Originally Posted by JoshEarl

Duncan,

I'd like to try that, actually. I tried to use a punch from Home Depot, and it just bent.

The trouble is that I don't use vintage-style pivots, so a precise hole is desirable.

Does the tang get bent at all when you do it this way?

Josh

Forge your own pritchels from old car coil springs then harden & temper them. Cheaper & better than shop rubbish. Make them fairly long & you will keep your fingers away from the red hot steel.

Yes, punching distorts the tang. Tapping in the pritchel from the other side after the hole is formed evens up the hole and straightens the tang to some degree. You then just flatten the tang on the face of the anvil. If you punch the dot hole dead centrally in the tang then you should not get too much curling up or down of the tang (as opposed to the side-to side bending which is just hammered flat) using the "punch out a disk" method.

If you require a precise hole, it might be worth considering punching it undersize then drilling or reaming it.

Good luck,

Duncan.

Mike Blue · 05-14-2008, 01:45 PM

Good idea Duncan. Some of the pins being used are 0.062 inch and that's a small hole to punch. Since the material being work is hot anyhow, any deformation is easily corrected.

Another method, if you have a heat treatment oven, is to do a subcritical anneal. Get the blade up to 1300 F and hold it for two hours, then let cool slowly. This will spherodize the carbides and while slightly harder than a complete annealing, the material will act like free machining steel and be much easier to drill.

O-1 can air harden. Look around the working shop for air blasts from the furnace that warms the building or a fan that's moving air. That may be all it takes to put a piece into the hard-enough-to-be-a-PITA to drill stage.

It's all a grand experiment to find a way to play with fire...