edge quenching any better than imersing the whole blade?

This is a very fascinating thread! Great reading for a newbie like myself. I have a question regarding multiple quenches. Is there a need for normalizing or a waiting period between quenches, or do you guys heat and quench 3 consecutive times?

Rick
 
Hillbillychuck: Good Questions! I have been waiting years to hear these kind of questions, THANKS!!!
How can a steel that measures lower on the Rockwell scale scratch a higher rated steel and cut longer? The most significant aspect of cut are chromiun carbides in this case (52100). Ultra fine chromium carbides which are uniformly randomly dispersed in the steel will not be accurately evaluated in most Rockwell testing outfits, the carbides are too small to effect the test. The probe on the rockwell tester deflects and measures the matrix surrounding the carbides.
(The nature of the matrix is probably the most significant and dynamic frontier for exploration we have at this time.)

When you cut with the blade, the carbides do most of the work, when they are washed out of the matrix the surrounding matrix is easily abraded away by the stone revealing a new bunch of carbides ready to go to work. Thus the ease of sharpening.

Oils differ, adatives do (who knows) and what for to a knife blade when hardening. The more addatives in an oil, the more complex the predictable life of the oil as a quench with the same results. Conversely the less addatives the longer the predictable life of the oil as a consistent influence. A quenching oil of known properties produces repeatable results that can be repeated - exactly. You know the flash point, you have reams of doccuments to use in research. If you want an oil just a little faster or slower you can start by varying the quench temp of the oil or, you can pick another oil and with the ASTM Standards predict very accurately the influence it will have on the knife blade.

The bladesmiths on the forntier 100 years ago had to use what he had available. They developed some great knives using what they had. I am planning some experiments with Bear and Lion fat, they will be interesting, but with limited application for most of us. Today we can select eactly what we need, oils and steel emperically defined at very little expense. The old way is a fun way, so is the stuff we do, for us.
 
Baumr; With 52100, 24 hour waits between quenches will definately influence toughness. It seems that the transformation is mostly complete after a few hours, but continues with progressively deminshing influence for some time longer. A blade that was made 150 years ago will definately vary in hardness from the time it was heat treated. Most of what is going to happen happens in 24 hours. I always give 52100 a lot of tincture of time, forging and heat treating, it can't hurt a thing and definately is worth the investment.

I strongly believe that multiple quench produces a more stable blade than a single quench.
 
You had me on lion fat (bear I figured out). I kept thinking Africa. Finally occured to me you have cougars around, just like the ones that stray into our neighborhoods every so often.
This is a great thread, and once again thanks to you Ed, we get an education in our field of interest, that would be almost impossible to obtain otherwise.
 
OK, it is starting to sound familiar. When you let it sit for 24 hours, you put it in the home freezer, right? Have you ever tried a more deep freeze cycle for the 24 hour period, like dry ice/acetone? Do you think it might have any benefit?

Rick
 
Thanks for the reply Ed,

Just call me grasshopper(remember the TV show Kung Fu?). So what you are saying is with a multiple quench the matrix is turned into a softer material but the carbides are bigger, or maybe just more uniformly spread through the matrix? John was saying that 1095 reacts the same way, but I thought that 1095 was a simpler steel that didn't form the same type of carbides as 52100. And what happens to the matrix? Is it given a larger, and thus softer grain with the multiple quench or is it fractured and broken up, making it softer than the carbides it surrounds? Or does no one know this yet? And how does the speed of the quench affect all of this? Does the transformation on 1095 continue for a time? Is it better to wait between quenches on 1095 or go for all three one right after the other? This is really great stuff!!!

Ken, you really started a great thread here.


Chuck
 
Chuck,

Let me start by admitting that this was a one-time "experiment" that happened on accident. The customer wanted a "hamon" on a Japanese-style piece. 1095 can be a bear to harden, and I really wasn't happy with the depth I got on the first two attempts. I nailed the third one. I also hardened a smaller blade on the same day, and I nailed it on the first try. Well, I tempered them together with very different results.

NOTE: Do not quote me here! I am just giving one possible explanation,but it could be totally wrong! I have not done sufficient research, nor do I have sufficient knowledge to truly answer this question now.

That said..... As for 1095 being a simple steel, yes, it is. But it also has over .84% carbon, or, in technical terms, is hypereutectic (or is is hypereutectoid? never can remember). Anyway, past .84% carbon atoms start bonding with other elements to form carbides. In 52100, that extra carbon bonds with chromium. I am guessing that in 1095 we are getting iron carbides. These would not be as hard as the chromium, but they would be harder than the matrix supporting them, leading to something similar to what Ed explained.

John
 
Thanks John, That did explain a good bit of what I was trying to figure out. You should try a faster quench on that 1095, I've never had a problem hardening it so hard that if you drop it before you temper it it breaks like glass. Try hot bacon grease, that works like a charm for me. In "The Making of Tools" by Alexander Weygers he says that pork or lamb fat is one of the fastest quenches that you can get unless you go to water. That is a really great book by the way, they have it at my local library. I've checked it out probably 50 times :D

Thanks again, this is a fantastic thread!

Chuck
 
RARANEY: Sorry about calling mountain lion lion. I have been reading some stuff from the early 1800's, this author simply refers to them as lions, I got so used to the term I used it by habit. He mentions using it as a quench oil after rendering to oil out of the fat.

Rick: I tried the liquid nitrogen quench at one time, I did not get the kind of blade that I felt would be totally reliable. They cut better, were very strong, but did not stand the flex as well. Also they felt like something I did not want in my hands when I put them on the Norton India stone. One day I may run the experiment again, we have learned a lot since then. Now I simply allow them to cool to room temperature in the quenching oil, then wrap them in some paper towels to avoid any real shock and place them in the home freezer. If the temperature is 20 degrees or less outside, they just go outside. While hardened and tempered blades are waiting for me to make them knives they sit outside my shop.

Chuck: The carbides are ultra fine, randomly and uniformly dispersed in the martensite matrix which is also very fine grained. The entrie operation, low temp. forging, and thermal cycles result in the fine grain structure. A uniform grain size may be brittle, 14 and finer grain, the and finer is a very significant influence. The soft portion of the blade surrounds a martensite cone, point toward the spine of the blade. There is a relationship between the soft and hard, both influence each other. This is a place where we have a lot to learn. You can see the influence between the two in the bands of the temperline. Some temperlines have up to seven bands. This is one benefit of working with great steel.

John, was there much difference in the cutting performance with your multiple vrs single quench 1084?
 
Hi this is DaQo'tah

I wish to make sure I understand something that might be important...

If I get all my steel from a guy named Rex Walters, and this steel comes 'ready to work", would my first steps be to heat it to Normalise it just to make sure?

The one thing I want to avoid is a warped knife, (I dont fix bends well), would I reduce warpage by multiple normalizing heats?
 
Normalizing refines grain. Normalizing releives stress. Warp in blades is caused by uneven stress in a blade. The uneven stress can come from many variables. Bilaterral symetry while forging, each side receives the same number and manner of hammer hits. If you move more on the right side, then simply even things out on the left side, the residual stress will not be even. Heating should be the same from side to side, when forging or during heat treat, same with cooling. Uneven geometry during the quenching operations may contribute to stress, the difference may only be a few tenthousandas. Warp is something you manage
constantly, even great blades may warp slightly. The trick is to keep thinking, and track down the source of stress. Warp is a fickel lady, but a great teacher. She is one to enjoy for she will lead the way to greatness.
Stick With It!
 
Lion oil? that wasn't the Ben Lily legend was it?

Just got done reading it. One great book:D

Would have loved to hang aound with Ben, for a day or two
 
Sweany: I read it in the Ben Lilly book and several others. One was an account of some men living on the frontier in the early 1800's, they had a blade that had been in a fire and rehardened it using the lion oil. I have been trying to find that story again for years and can't remember where it was.
 
Hias :) A few months ago I was in a rush to make two knives for a friend. I had two days to finish two blades, and if anyone else who knows how slow I work wants to comment, will tell you it just didnt happen.. heh. So anyways, It was the first time I'd quenched 1095 with a torch, so I heated the first blade to nonmagnetic, and quenched in used motor oil, it was still to soft as a file would easily mar all but the very edge, so I tried again, more or less the same result but more of the edge was hard. I gave up on the oil and finally quenched it in cold (~60-70 degree) brine. The blade was finally hard. Odd thing was, even though the entire blade (according to my magnet) was at critical when I quenched, I got a "very" distinct hardening line. It now seems to follow the edge of the spine of the blade (its a wharncliffe) but I think thats because I overdid it a bit on the final grinding (I didnt grind the point to prevent warpage and uneven hardening) Still, I have no idea how I got a sharp hardening line when I did a full quench. Wierd stuff steel is :p Now Im tryin to debate whether to finish it, and make it my personal neck knife, or just do some cutting and other tests, then break it to check out the grain. Any suggestions?
 
I use diff hard on blades over about a 4" blade length. Less than that I have no functional need in my work. My full hard 4" blade are damn tough too.
 
Yoda: what you describe sounds like a hardening cycle where the oil was not fast enough to harden the blade to the desired hardness, but hardened it a little. This is the big problem with using a quench medium of unknown effect. When you use a known well specked oil such as Texaco Type A, you know what happened. I would do some experimenting with the blade, cut with it, then get some specific quench oil, forge another blade, harden it with the known oil. Then cut with it and compare it to the first blade, then do some full flex tests and see what they look like. Consider it an opportunity to learn.
 
Break it Yoda. Don't worry I'm sure you'll make more. :p

I agree with Ed.

Something to know. The cold hard facts like destruction testing put all that theorizing to good use. You can read and listen to everything out there, but when it comes down to it, your hands have to be able to match your brain.

In matters of hardening... when you can see that glassy, satin look of a nice fine grained steel, the satisfaction will give you tons of confidence in your skill as a maker.

-Jason
 
I figgered out what Im gonna do, Im gonna make it a "skeleton" handled neck knife that I'm gonna use for general cutting and rope testing, and I'll use it hard. Then after I make a few more blades and break those and test em, I'll test this one to destruction and see what I did with it.
 
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