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Need help Annealing

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Hello, I am trying to anneal a leaf spring to make a knife, I heated the metal to non-magnetic and quenched it in used motor oil and let it cool. I tried to drill a hole in the blank but it is too hard, the bit wouldn't even dent it. I thought this process would soften the metal so it could be worked. What did I do wrong?

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Triton you did NOT anneal that piece of spring, you hardened it. To anneal, heat the piece to non-magnetic, then let it soak for a couple minutes at that temperature to be sure it is heated completely thru. Then put it in a bucket full of ashes, vermiculite or lime. Make sure it is completely buried in the stuff in the bucket. Let it cool in the bucket over night.

Remember Quenching steel hardens it.

Slow cooling over a long period of time, annealing, softens steel.

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Two things,
Non magnetic is not always the right temperature to get everything into solution. Certainly let it sit at that temperature for a little while.

Any quench (oil or otherwise) is a hardening process.

Try allowing the metal to cool down very slowly in a bucket of wood ash, vermiculite or lime. Be aware of the health risk associated with the latter two!

At worst, allow the material to cool slowly be the side of the fire.

I believe their are a couple of metallurgists that subscribe to IFI and I hope that they can offer better advice.

Good luck

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Welcome to the merry band Triton.

I know you want to get to it but after annealing that piece of steel you might want to learn some basic forging techniques and build some skill while reading about bladesmithing. A little knowledge will go a long ways to successfully making blades.

If you'll click "User CP" at the top of the page and edit your profile to show your location you'll discover the folk living close enough to visit personally for some help.


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I seem to remember some one telling me that pearlite will work instead of ashes, vermiculite, or lime. Would that work, or am I mis-remembering? It tends to happen that way quite a bit...I need to take better notes.

Just a little FYI, "pearlite" (I know that was probably a typo, and you meant perlite, but I thought I would throw out some metallurgy ;) ) is actually the softened structure of steel that you are trying to attain through annealing. It is composed alternating bands of ferrite and cementite (iron carbide). When you heat steel above its critical temperature, austenite forms (simply put, the iron and carbon go into solution, forming a FCC crystaline structure). If you cool the steel slowly the carbon will diffuse and will form pearlite again. The slower you cool, the greater amounts of carbon will be able to diffuse, the more pearlite will form and the softer the steel will become. If you cool austenite very quickly (through quenching), the carbon will not diffuse sufficiently enough to form pearlite structure and the result will be martensite (or bainite, depending on the cooling rate). Martensite being the hardened structure of steel, formed when the carbon is "trapped" within the FCC strucure of austenite which essentially contracts, and in its contraction distorts and forms a body centered tetragonal structure, which is a much more ridigid structure, therefore allowing for less deformation, which is "hardness". The quicker you cool steel the less carbon will diffuse out of solution, the more martensite will form and the harder it will become. However, with higher carbon steels, you can cool them too quickly, forming too much martensite. The crystaline structure of martensite actually takes up more room than that of pearlite, resulting in expansion, (thats why differentially hardening a katana causes it to curve, since the edge is being hardened (forming martensite resulting in expansion) and the spine is not being hardened (pearlitic strucure)). This expansion of the martensite structure, paired with the rigidity of the structure will not always allow for the deformation and stress caused through this expansion, and the structure fractures (this is why quenching oil-hardening steels in water causes them to crack). In cases where there is more carbon present, more carbon will go into solution, meaning that it will take slower rates of cooling to diffuse this additional carbon. This is why higher carbon steels will become "harder" than those with less carbon, but it is also why they must be cooled slightly slower durring hardening (oil and air quenching, instead of water or brine). There are also alloying elements added to some steels to effect the rate of diffusion and other characteristics, but that is a whole other topic.

Anyway, hope I didn't get too carried away ;)
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