Must I normalize before quenching?

[pso]

I noticed in my thread "preparing to heat treat" that Silent suggested normalizing before doing the actual quench to harden the blade. How necessary is this? What does normalizing do to/for the steel? Would I normalize at the time that I do the hardening (rather than as a separate process, say at a different time)? It appears that normalizing is somewhat different process from annealing in that the steel is allowed to cool naturally in the air instead of being insulated so that it cools to room temperature over many hours.

Thanks for your help.

Phil

 

[peter nap]

I'm going to let others give the nitty gritty on it but IMHO it is one of the most important steps in heat treating. This is both for edge quality and to remove stress in the steel. I've started doing it in threes just like the quench and temper.

 

[Will52100]

Pso, I don't know if it's necisary on stock removal, but if for no other reason on forged blades it helps keep the blade from warping in the quench. From my test it also showes an increase in edge holding and toughness.

Maybe someone can explain it better, but from what I understand normalizing re-crystalizes the steel from all the torcher you put it through during forging. It also helps to refine the grain structure makeing a stronger, tougher blade.

Like Peter, I now triple normalize, and have found it to be esential for me.

 

[pso]

Peter and Will

Yes, I am doing stock removal. The steel is from a bandsaw blade from a timber mill. I would imagine that it had a fairly hard life and is probably full of stress so normalizing probably would not hurt at all.

Phil

 

[Will52100]

Pso, I've use some band saw befor, and without a normalize session, every one I tried wanted to cure back in a band saw shape for me.

I would soften a piece on a brush fire so you can saw it, cut your profile out, (I have cut them out with a torch, but spend a lot of time removeing burnt metal.) heat up and straighten, then normalize in still air. An annealing cycle is up to you,(I havent' found much differnce on the simpler steels like L-6) after grinding heat to a little higher(50deg. or so) than nonmagnet, edge quench 1/2 to 1/3 in warm oil, then triple temper at 350 deg. for 2 hours each time. Test the edge, if it dosn't chip out you are on the money.

If you got what I think you have, heattreated right I havn't found a tougher blade steel. The edge holding will be similar to 1095, but will be virtuly indestructible. If all goes well you should have an ecelent hard use knife.

 

[Epsilon]

Get a cup of coffee or something, I wrote a whole lot.

Pso, here is what I know and what I have personally experienced. This opinion of mine is not meant to agrue anyone, I just want to point out some facts that I am aware of. Take them as you will guys. No offense intended.

Pso, normalizing is a type of annealing process. Annealing is any process that involves the recrystallization of metal. There are different annealing types for different metals, alloys, steels, heat treatments and desired effects. Normalizing is used in irons and steels. It involves heating a steel at least 100°F past its Ac3 temperature. What that means is, you must attain and tranform (fully, as in 100%) the microstructure of iron into a form called "austenite" and then allow the steel to cool in still air or at least slow enough to miss the Ms or "martensite start". The temperature in which martensite forms. This technique returns the steel to "normal". It is typically only used on carbon steels or those with low hardenability. Though techniquely, you can run the cycle on anything, you just won't get a normalized effect on everything. Ac3 is not to be confused with "critical temperature" which is Ac1. Ac1 marks the very beginning of austenite transformation and the structure is nowhere near homogeneous austenite.

Whether or not to use it at all in the making of a knife will depend on all that you do to the steel. I feel if you are forging and then heat treating in the forge (by eyesight obviously), the typical thrice normalize is a good practice to insure that stresses from forging are virtually eliminated. Also, it helps to keep the microstructure relatively uniform upon hardening to insure accurate transformation upon reaching temp for hardening. However, full annealing, the kind where you let sit in an ash pit or kiln will do the same thing, but allow better machining properties and far greater stress relief (austenitizing temperature is typically lower also). You are left with a coarser grain size though. However, this effect can be negated by either normalizing or just going to the hardening temperature and quenching. There are some exceptions out there.

Well there's something to chew on.

-Jason