Annealing mistake?

[flandersander]

So, I'm trying to make a knife from a leaf spring. I tried to anneal the steel by throwing it in a campfire. The fire burned for about an hour or so, and I left it sit outside in the ashes overnight. I went out this morning, and drew out the knife shape. I went to cut off some extras, and wrecked a hacksaw blade. Whatever, I dismissed it as being dull when I started. So I broke out the grinder, and cut off a corner. It took a lot longer than I expected. I got about 9/10ths of the way through, and decided I would fatigue the steel and break it off. So I took it over to the anvil, and hit it with a 4 lb hammer. Nothing. Didn't break, didn't bend. Nothing. So I whacked it again. Nothing. I repositioned, and hit it, and the corner didn't bend, but it snapped clean off. WTH!? I thought annealing it softened it, so it was easier to work? Did I accidentally harden the snot outta the steel? What can I do now, to make it workable? This came as such a surprise. lol.

[Camp10]

No, you didnt make a mistake. Leaf spring steel is 5160 (most likely). If you look this up you will see the annealing process for this steel is a very slow. I dont have my "cheat sheets" in front of me but you can do a Google search on it and see what I mean. It needs to be held at 1400 (or something like that) and then cooled at just a few degrees and hour until it is below 800 (again, something like that). You can normalize it with the process you used as long as your fire got it to non-magnetic and then work it like that.

You did learn though why it is a great knife steel, the stuff is hard, tough and forgiving to work with.

[flandersander]

Thanks Camp10! I did a little research, and was told to heat to 1450 F and let air cool. Okay, I can do that, but how the heck will I know if it get's that hot?

[Camp10]

Thanks Camp10! I did a little research, and was told to heat to 1450 F and let air cool. Okay, I can do that, but how the heck will I know if it get's that hot?

That will leave it normalized not annealed..still soft enough to work but not as easy as plain steels can get. You can check the temps with a magnet. When the steel is non-magnetic it is in the austenite stage. This is when the crystal structure changes. The hardness of your steel is determined by what you do when the steel is in this state. If you quench it, you form martensite. This is when the carbon is trapped in the crystal structures of the steel. If you allow the steel to cool through it's austenite stage slowly, the crystal composition will go back to "normal".

This is a pretty generic explaination. All steels have their own magic formula but the basic rule of thumb with carbon steel is non-magnetic to change the structure. If you look for my DIY 1095 heat treat thread, it has a picture of me checking temp with a magnet. A picture is worth a thousand words..or something like that.

[canid]

most people learn to tell by color [when viewing a given steel at a given light level, out of direct light] and - with simple steels - by magnetism.

it's can be pretty hit and miss untill you get used to it. i've done it many times and i will probably continue to mess it up from time to time for a long while to come.

if i may make a suggestion, the next time you try it, rather than leaving it in the fire unattended, watch it, and if nessecary, find a longish tube you can blow through to feed air to the embers the steel is in slowly until it comes up to temp.

this will let you get a feel for how quickly the fire brings your steel to temp, at what intensities, and you will actually be able to see where the heat is even, overly hot and overly cool. it is best to do either always in full shade, or always at night, as heated steel looks much different in different light levels.

if the fire is reaching the appropriate temperature for very long, you can cause decarburization, and end up instead with steel that doesn't harden well, just the other end of the problem spectrum.

in either event, you should pack it in a depth of loose ashes where the fire is no longer burning, or not burning intensely, and let it cool until it is cool to the touch [12 hours is often good].

i hope all that was helpful.

[Rick]

If you look for my DIY 1095 teat treat thread...

A Freudian slip if ever there was one.

[canid]

and rarest of the rare; a clean one at that.

[Camp10]

if the fire is reaching the appropriate temperature for very long, you can cause decarburization, and end up instead with steel that doesn't harden well, just the other end of the problem spectrum.



i hope all that was helpful.

Yeah, very good point. It only needs to stay in this austenite stage for a short duration, just long enough for the crystal structure to change. Some steels have a soak time others really dont need to.

[kyratshooter]

This will probably be easiest if you have a wood stove where you can keep the temp level and hot for a long period.

If you get the whole thing good and red it should be around 1400-1500. If you bury it in sand, real deep, it will cool slowly. I have seen large pieces like this still be warm the next day.

How do you plan on retempering and drawing it when you get finished if you do not have a heat source to anneal it?

[klickitat]

I would do most of my annealing in the wood stove. However if it was the warmer part of the year when I was not running a wood stove, I would wrap my steel in a couple of bats of fiberglass insulation. I tried to make sure the roll ended up at least 2' in diameter. Try to throw the last bat around the ends and let sit 12-16 hours.

BTW: that was after I heated the steel with a torch.

[flandersander]

Well I figured I would head it to non-magnetic in the forge, and quench it. Then possibly temper it in the oven, for a few hours, then let it cool slowly. Or something to that effect.

[rebel]

You may need to anneal it a couple of times.

[flandersander]

Well I heated it beyond the point where it becomes non magnetic, and burried it in fine gravel. (I didn't have any sand) I'll let it sit there overnight, and see what happens. I can't wait to see how the knife turns out.

[klickitat]

Well I heated it beyond the point where it becomes non magnetic, and burried it in fine gravel. (I didn't have any sand) I'll let it sit there overnight, and see what happens. I can't wait to see how the knife turns out.

If you are going to use mass to slowly cool the blade then you need to heat the medium as well. Putting it in a cold medium is only going to harden it. No different than water.

[flandersander]

AWEH! Well that was a big waste of time. Okay, I've got it figured out now.

[Rick]

Just keep saying, "We learn by our mistakes".

[preachtheWORD]

I don't know much about annealing, but I did make a balde from a leaf spring by stock removal - i.e., grinding. The most difficult part was straightening the leaf spring. See this thread for the story, with pics:

http://www.wilderness-survival.net/f...ad.php?t=12452

[kyratshooter]

Well I heated it beyond the point where it becomes non magnetic, and burried it in fine gravel. (I didn't have any sand) I'll let it sit there overnight, and see what happens. I can't wait to see how the knife turns out.

And you really need sand. For some things you simply can not replace what works with something close just because that is what is available. This is not like choosing between Verison and T-mobile.

[klickitat]

Just keep saying, "We learn by our mistakes".

I 100% agree with this, with one exception; the only time it is a mistake is if we did not learn from an event. Learning what not to do is usually more valuable than what to do.

Keep going and do not give up. You are on a journey and we are all pulling for you.

[flandersander]

I've got a bit of an idea. Have you ever cooked in a pit? With hot rocks? What if I heated some rocks super hot, and threw the non-magnetic knife into the hot pit, and covered it over. That would take forever to cool down. Think it would work? I just don't know how I could heat up the sand.