Annealing instead of normalizing to refine grain and remove stress?

flatgrinder

flatgrinder

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Dec 20, 2005
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I notice most guys who heat treat carbon steels like to normalize at least 3 times prior to quench.

Correct me if I am wrong ... to normalize, you heat to non-magnetic, hold for a few seconds and then let it air cool, right?

What if you let it cool in vermiculite instead? In effect this is annealing, right? Would this also remove stresses and result in smaller grain size due to the slower cooling rate?

Has anyone annealed or triple annealed a blade prior to quench? Would it be better than normalizing or is it a waste of time?

Any insight would be really appreciated! Thanks! :thumbup:
 
Hold for a few minutes not seconds.You'd end up with larger grains and larger carbides , either coarse pearlite of coarse spheroidized. That's because it's at high temperature longer where grains will grow.Annealing , normalizing, or 1000-1200 F will all relieve stresses.
 
flatgrinder said:
I notice most guys who heat treat carbon steels like to normalize at least 3 times prior to quench.

Correct me if I am wrong ... to normalize, you heat to non-magnetic, hold for a few seconds and then let it air cool, right?

What if you let it cool in vermiculite instead? In effect this is annealing, right? Would this also remove stresses and result in smaller grain size due to the slower cooling rate?

Has anyone annealed or triple annealed a blade prior to quench? Would it be better than normalizing or is it a waste of time?

Any insight would be really appreciated! Thanks! :thumbup:
Click to expand...


Air cooling is a great happy medium between annealing and quenching. You see if you quench from proper normalizing temperatures you run the risk of cracking many steels, while cooling too slowly will not give the uniform refinement you are looking for. The TTT curve and the Iron -Carbon phase diagram are both based upon Equilibrium conditions, that is things are held at temp long enough for those structures to form. Equilibrium is not necessarily what you want in heat treating that involves cooling as it allows thing to happen that you don’t want to happen.

If you are dealing with a steel that has over .8% carbon allowing equilibrium conditions above the pearlite phase will cause separation of carbide, and if you give it time it will go right for the grain boundaries. Course pearlite will form as it drops more. Yes you will have a very stress free soft blade but that is not the goal of normalizing. The goal is to homogenize and refine the inside of the steel. Industry recommends that you not normalize L6 because that will only harden it, but I still do for the sole purpose of refining structures, I just need to be more careful.

In general the quicker you cool steel the finer the products will be, the slower you cool the coarser they will be. Use heat to mix it all up and then cooling to refine it where it is, gong really slow will set you back to square one. And lets not forget the best reason to air cool- getting back at it sometime today :D.

The most common questions asked in this business begin with “what if you…” What if you quench in…, What if you used… What if you heated…, all very good questions if you are looking to improve upon something some bladesmith is doing or advising, but it can get you into problems if it concerns something that the folks that made the steel suggest, as they pretty much have figured the whole thing out quite well, in the most effective and efficient way. As bladesmiths, for the time being, we need to always be looking for ways to improve how we do things, for this all we have to do is look to industry and trust that they know what they are doing. I have found that many of the numbers in those books don’t work as long as I try to mix the goofy bladesmithing ideas with the industry standards, but as soon as I just let go and trust the folks who made the steel and put the bladesmithing concepts aside for a minute, all the numbers start working just like they do in the books. Reinventing the wheel can be quite exhausting if you need to do it every day.;)
 
Hmmm, I suppose to speed normalizing up and prevent excessive carbide formation in the grain boundaries you could "quench" just long enough to get past the pearlite nose and then back into the forge before Ms is reached. This method has been described to me before but I never put it in the context of carbides in the grain boundaries in hypereutectoid steels, which I'm only just starting to work with.

But aside from that, is air cooling fast enough in normalizing hypereutectoid steels to prevent excessive carbide formation in the grain boundaries?

Here's another question, in a steel like W2, do the vanadium carbides, which do not go into solution at normal austenitizing temperatures, hinder or help the formation or lack of formation of carbides in the grain boundaries?
 
Vanadium in the small amounts found in W-2 is there for grain refinement. Whether in solution or as carbides the vanadium collects at the grain boundary .This impedes movement of the grain bondaries which is necessary for grain growth - therefore 'refining' the grain. The iron carbide that collects in the grain boundary is independent of that .It's a matter of diffusing to the grain boundary as you approach the equilibrium conditions....Air cooling is fast enough to prevent grain boundaries collecting carbides, assuming they haven't already collected from previous conditions.
 
Guy Thomas said:
Hmmm, I suppose to speed normalizing up and prevent excessive carbide formation in the grain boundaries you could "quench" just long enough to get past the pearlite nose and then back into the forge before Ms is reached. This method has been described to me before but I never put it in the context of carbides in the grain boundaries in hypereutectoid steels, which I'm only just starting to work with.

But aside from that, is air cooling fast enough in normalizing hypereutectoid steels to prevent excessive carbide formation in the grain boundaries?

Here's another question, in a steel like W2, do the vanadium carbides, which do not go into solution at normal austenitizing temperatures, hinder or help the formation or lack of formation of carbides in the grain boundaries?
Click to expand...

Guy, just follow mete's advice on the methods, but I wanted to drop a warning about quenching in normalizing. First, you don't need to avoid pearlite you just need to avoid really slow formation of it. But more importantly, if you are going to quench you need to make some decisions. You can quench to pearlite and then stop, or you can quench to room temp, but not in between. If you succesfully avoid pearlite all you will have is the same old austenite that will have only upper bainite as an option to transform to, and you may not have that much time. Reheating the same austenite obviously will not make new and finer austenite grains. You need to transform into something else first in order to make fresh austenite from it, the quickest product will be fine pearlite at 1000F. But if you avoid it by quenching the next quickest will be martensite at 400F- 200F.
 
Thanks for pointing out what should have been painfully obvious to me Kevin. I was thinking purely in terms of temperature and not structure. My regular routine is to normalize as Mete outlined, air cooling the steel and letting it fade entirley to black in deep shade before returning it to the forge.
 
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