Testing times, temps, normalizing, quenching, etc.

NickWheeler

NickWheeler

Joined
Dec 3, 1999
Messages
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Right out of the gate, I should mention that I am way behind in the shop... so this thread is NOT me volunteering to conduct and manage some kind of all encompassing testing for the forum. I'd be glad to share what I find, when I have time, but there's no timeline for this.

I have been learning about heat treating for about 14-15 years now, and it seems the longer I do it, the less I feel like I know/understand. :o

With the myriad of threads floating around all the forums about varying processes, it always leaves me wondering if what I'm doing is optimal, or if somewhere something could/should be improved.

So I'm going to be doing some more testing on a handful of steels--- definitely W2, 52100, and 1084, maybe a couple others.

Just an example of what I'm talking about here. I always do a very high initial normalizing cycle on these steels after forging them, 1700F to be exact. Most guys scream that's way too hot, and I'm blowing up the grain. Well, it is too hot for grain refinement, but for that initial heat, I'm looking to smooth out the disasters I caused inside the steel during forging, and start refining the grain on the next heat.

However, I've recently seen a lot of mention of heating to 1650 and quenching. I don't remember ever reading that in a text anywhere, and my gut tells me that it is throwing a ton of shock at steel that isn't ready for it... BUT, I've never tried it. So, I want to actually try it for myself and see what happens.

Another example, I have always done a spheroidal anneal on 52100 (well, since I got a kiln anyway), but I've seen some recipes for normalizing that are supposed to set up a pearlite structure that's easy to grind/drill, etc.


I'm going to be doing these tests with both my Paragon and my digitally controlled salt bath. I'm going to do some multiple quench pieces too, just because I can. ;)

So my question-----

If you were going to do something like this, what would you try? What would you want to test? Any particular times, temps, quench cycles, etc.?????


At this point, my test "coupons" are in about 3 sizes-

1/8" X 1" X 4"
1/4" X 1-1/2" X 4"
5/16" X 1-1/2" X 4"

I cut a slice from each to do a Rockwell test in the "from the mill" condition. Since I forge most of my knives, most of my test coupons are forged down from larger stock, but I do have some pieces that were cut from the parent bar and surface ground in their "from the mill" condition.


So if you have any ideas about this, please feel free to throw them out there.


Thanks :)
 
How about at what temp the grain begins to grow? Heat to 1500 and quench then break to see the grain. Then heat another piece to 1550, quench and break, another at 1600, quench and break. You get the idea. Stop when the grain looks larger than the prior one. Wouldn't this give you a good idea what the highest heat for normalization that you could get away with?
 
From what I recall, the high temp with a short soak is to purposely grow the grain to make the random sizes of it more uniform. Then by progressively lower heat cycles, the grain is made smaller and ready for the hardening quench.
 
LRB has it.
You want to grow a medium to slightly large grain size to start with, then make it smaller. 1650 or 1700, won't make a huge grain size without a long soak. 2200 will grow big grain fast.

Lets look at this example:
You have a jar of 300 green jelly beans and 100 red jelly beans that you want to put into piles of twenty green and five red, you could start counting 1-2-3-4-5-....20 green;1-2-3...-5 red, repeat...... ,but that would take sixteen slow repetitions. If you mix them up on the table, and divide them into roughly half with a ruler, and then divide those piles roughly in half, and do this a total of four times, you will quickly have sixteen piles of about twenty-five jelly beans. The average will be about 20 green and five red.

Now, that does not seem to have much to do with grain reduction, but in a way it does. If you start with a larger grain, the carbides are more evenly distributed because there are less places for them to be. As you refine it by dividing those grains, you end up with a more even distribution of the carbides, as well as finer grain throughout the blade. Carbides don't move around much at just above critical, but do pretty well at 1650-1700.

The stress in a quench from 1650F shouldn't really be any worse than from 1500F if the quenchant is right. It forces the steel to form new grain.

Nick, I look forward to seeing your results.
 
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I am less than a year into this, and am absorbing all I can. I will be watching this carefully.
 
I tried to get some clarification on that as well, so I look forward to your results, Nick.

NickWheeler said:
However, I've recently seen a lot of mention of heating to 1650 and quenching. I don't remember ever reading that in a text anywhere, and my gut tells me that it is throwing a ton of shock at steel that isn't ready for it... BUT, I've never tried it. So, I want to actually try it for myself and see what happens.

Thanks :)
Click to expand...
 
I'm very interested in what you'll find, Nick.

Thanks a bunch for hangin it out there!

I could ask for a bunch of things, but I'll be satisfied to see your own methodology and results.

I feel about the same way. The more I learn, the more I find things I'd like to test more thoroughly, but it sure takes a concentrated effort.

Hat's off to you, friend. I hope you find good results.
 
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Thanks guys. :)

My approach to normalizing is the same as what LRB posted. :)

For the record, I don't have any intention of trying to prove anyone wrong or right with any of this, I just want to keep building a better understanding of heat treating.

I'm also not trying to reinvent the wheel! ;) :)

A big "issue" I have with many of the interwebz heat treating conversations, is that a lot of what I see seems to be regurgitated information from books and websites, without the posters having real world experience. An ounce of hands on experience is usually worth ten pounds of theory.

It's like with the no clay differential stuff I've been doing. Some guys don't think it's possible. Then there's the ones that will say, "Well of course it is, it's simple! It's just a matter of setting up the proper structure in the steel and hitting the correct times and temps! Easy as 1-2-3!!!"

Okay, well go do it then. ;)

So my point is, I don't know exactly where this thread might go, I just want to work on narrowing variables and bridging theory with application, for my heat treating. If you guys can help me out, and I can help some of you out, then that would be a win-win. :) :thumbup:

Thanks fellas. :)
 
BTW- Grizz... go ahead and throw your ideas out there. There's a really good chance you've got something I haven't thought of.
 
Its great that you're doing this and even greater that you're not trying to biasly prove one method better or worse then the other. Just a pure search for what/which methods produce the best blade possible. Good on ya brother.
 
I have been thinking of something similar, but much more limited. I was thinking of comparing normalization with quenching. I.e. cooling in air and quenching at 1600/1500/1450. To see grain size. Stacy seemed to imply that air cooling doesnt reduce grain size (at least in 52100) but my limited testing in 1084 did show very good grain reduction with air cooling in descending temps.
My plan was to harden one piece of 1084 right from Aldo. Heat 3 others to grow grain. Quench one for comparison of the bad grain, and normalize one 1600/1500/1450 and one quenched at each of those heats.

I would be very interested in any findings that Nick would have. I think that most are trying to make the bed blade that we can, but the water seems a little murky on how to do that.
 
Cody Hofsomme said:
Stacy seemed to imply that air cooling doesnt reduce grain size (at least in 52100) but my limited testing in 1084 did show very good grain reduction with air cooling in descending temps.
Click to expand...

I don't think he meant that, Cody. Of course you'll get grain refinement as steel is thermal cycled at decreasing temperatures(within the austenitic range.) I think(and I might be wrong, but...) that through quenching, Stacy is creating more potential nucleation points (higher energy martensite) and avoiding any unwanted structure formations. The latter is especially important in hyper-eutectoid steel, where excess carbon can migrate to the grain boundaries and cause problems. Quenching "locks" them in. In eutectoid steels it isn't as important but quenching from black (800F-900F) can help prevent fine perlite from turning into coarse perlite. Same goes for tempering... Quenching between cycles prevents certain precipitations from happening(please don't ask me to describe the unwanted precipitations :o).


I start my normalizations high (1650F-1750F) but don't quench on that first heat. Call me a chicken but it scares the hell out of me to quench at high temps.

I ran my own testing a while back and was shocked to find some insane temperature spikes in my kiln. Along with my kiln's pyrometer I added two more. One was an analog and the other is a very sensitive digital unit. The sensitive T/C was picking up spikes as high as 200F @ 1500F quench settings and 100F @ 400F temper cycles. Whenever the elements kicked in, the smaller T/C picked up radiation heat while the larger ones stayed fairly consistent. The way I see it, a .020" edge would be pretty vulnerable to temperature spikes like that.

It's something to think about. Maybe Nick can dip his toes into temperature control as well. I would think the salt pot would eliminate most issues.
 
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Thanks Rick, you really do have a way of explaining things. I was going to ask more about that, but decided that it would be some thing I could try and not be "that guy" that won't try to find out on there own. So I thought I would derail Nicks thread instead! ;)

Looking forward to Nicks results
Cody
 
Nick,
I'm not sure if you had considered this, but you may want to consider grinding to your normal edge thickness, as well. I don't know that my assumption is.correct, but wouldn't the different geometry present in a blade vs. a blank be a consideration, as well? It may be harder to get a cleaner break, but my guess is it may be worth trying to see if there is a difference. Again, I may be completely wrong.

BTW, since I didn't say it in the other thread, congrats on getting married! It's a good thing to find a woman that compliments you, but even better to find one that drives you to be better... The best to you both!
 
Rick Marchand said:
I don't think he meant that, Cody. Of course you'll get grain refinement as steel is thermal cycled at decreasing temperatures(within the austenitic range.) I think(and I might be wrong, but...) that through quenching, Stacy is creating more potential nucleation points (higher energy martensite) and avoiding any unwanted structure formations. The latter is especially important in hyper-eutectoid steel, where excess carbon can migrate to the grain boundaries and cause problems. Quenching "locks" them in. In eutectoid steels it isn't as important but quenching from black (800F-900F) can help prevent fine perlite from turning into coarse perlite. Same goes for tempering... Quenching between cycles prevents certain precipitations from happening(please don't ask me to describe the unwanted precipitations :o).


I start my normalizations high (1650F-1750F) but don't quench on that first heat. Call me a chicken but it scares the hell out of me to quench at high temps.

I ran my own testing a while back and was shocked to find some insane temperature spikes in my kiln. Along with my kiln's pyrometer I added two more. One was an analog and the other is a very sensitive digital unit. The sensitive T/C was picking up spikes as high as 200F @ 1500F quench settings and 100F @ 400F temper cycles.

Whenever the elements kicked in, the smaller T/C picked up radiation heat while the larger ones stayed fairly consistent. The way I see it, a .020" edge would be pretty vulnerable to temperature spikes like that.

It's something to think about. Maybe Nick can dip his toes into temperature control as well. I would think the salt pot would eliminate most issues.
Click to expand...

How about putting a muffle pipe inside the kiln ?
 
Thanks Rick, That is exactly what I was referring to. Martensite makes a much better platform for grain reduction than pearlite.

There is often a mental disconnect between the terms Grain Growth, and Growing Finer Grain:

In Grain Growth, the energy provided to the grain boundaries ( from heat in our situation) causes them to cannibalize the adjacent boundary, thus absorbing the next grain, and becoming a bigger grain. So 1000 grains per area becomes 500, then 250, then 125, ...and so on. Thus, you get fewer and larger grains in a Sq.mm ( Lower grain size number).

In Growing Finer Grain, the grain boundaries are coerced into nucleation, and start new grains. Thus, 1000 becomes 2000, becomes 4000, etc. This makes more and smaller grains per Sq.mm ( Higher grain size number).
 
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