5160? Please read!!!!

What gets me is,Mr Fowler has done pretty extensive testing on his steels and has had them sent off to be tested after almost evey procedure From forging to completion to prove his treatments. The important thing is that we all do our own testing to see what works for us. I personaly like the idea of "triple-triple-triple" heat treatments and until I find my own system (which seems to me at a stand still), I will continue to use Mr Fowler's methods.
 
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Why are you annealing the blade after normalization, right before hardening?

This is a completly unnecessary step, and could in fact be a cause (or contribution) of your hardening problem (I won't speculate as it could be a number of factors, soak time, decarb, wrong steel, etc and could really only tell you if I saw your exact process). Annealing is only necessary when you need to be able to easily work the blade (grinding, filing, etc.) and doesn't need to be done after normalizing.

I heat treat 5160 very similar to the approach defined by Mr. Cashen.

After forging, I give a quick normalization, and then anneal. Get all the grinding done etc, and then HT.

I do tripple, step down normalizations (one above crit, one at, and one below) with proper soak time durring each heat.

Dirctly following normalization I then go into the final heat for hardening (no need for un-necessary annealing cycles or anything like that in between, thats just more chance for decarb, and additional grain growth/mistakes) giving the blade proper soak time (I heat to 1525 F and I usually give most blades at least 5 min soak time at critical to ensure proper carbon diffusion, thicker blades I might give a bit longer. Also note that I'm running a digitally controlled furnace that gives pretty decent control), and then I quench in warm (about 140F) mineral oil.

Then its let the blade cool past Mf, and then into the tempering oven, for at least 2, 2 hour cycles (temp dependent on the actual blade and its intended function... but somewhere in the neighborhood of 375 F for most).

Cut out that extra annealing cycle, be sure to give proper soak times and double check your temps and that might fix your issues.
 
I will add one thing.

Many newer smiths think they have a bad piece of steel because the edge will not get hard. They often take the edge down too fine and it gets badly decarbed in the HT. Add to that that they may have heated it up above critical three or four time before the last quench ( I am not a fan of multiple quenches). The hard steel is there...just buried below the layer of decarb. I have often told a smith who contacts me with this problem to take the knife and sharpen it, made it dull, and sharpen it again...three times. The last time the knife suddenly gets screaming sharp........the decarb has been sanded/stoned off.

Stacy
 
The main reason I anneal is so that the spine of the blade is as soft as it can be for the JS test, if this is wrong please tell me so.If i just normalize it it will stiffer, Am i right?Do most JS only normilize when they take there test?
 
........Plus when you tell the average joe, this knife has been triple heat treated and was labor intensive he's gotta have one.Lol.

uhh, not really
 
Unfortunately that line of thinking doesn't actually work.

As soon as you heat the blade up past critical temperature, all the pearlite (softened strucutre) you created in your annealing transforms into austenite (think if it as a "transition" state), basically undoing the annealing anyway. The rate at which you cool the blade once in the austenite stage will determine what final microstructure the blade takes. If you cool things quickly enough (quench) the austenite will transform into martensite (hardened structure of steel), if you cool things more slowly, the steel will transform back into pearlite, or a combination of pearlite (course and/or fine grained) with some martensite, or even some bainite..... depending all on the rate of cooling.

So essentially the structure you created before heat treatment goes away (not completly of course, things like grain size can be affected by previous heat/cooling applications, etc) as soon as you heat the blade up to austenizing temperature (critical temp). So again, that annealing cycle is pretty worthless, just an extra cycle to create more decarb, possible grain growth, and if you are annealing well, requireing a much longer soak time to ensure all the ferrite and cementite (iron and iron carbide, which makes up pearlite) diffuse properly when at critical temp.

Now if you only heated the edge (say with a torch) it is possible for that structure to reamain in the spine of the blade, however I'm not a big fan of trying to torch heat a blade evenly, without over-heating.

Its all about how fast you cool the blade from critical that determines your final microstructure. You need to understand firstly what a TTT [Time Temperature Transformation] (or IT [Isothermal Transformation]) chart is, and what it shows, as well as what all the various microstructures of the steel are and what they physically mean, and in doing so you'll come to understand a bit more about how and why steels harden in certain instances and not in others.

I'd write pages trying to explain it all here (and have written pages on the topic, they are on my website under tutorials)

Additionally I recommend for a more thourough explination of things, you read the Verhoeven paper on the subject http://www.feine-klingen.de/PDFs/verhoeven.pdf

And take a look at Mr. Cashen's website as well, he has some very good information regarding the metallurgy of steel.

And a final note about the JS test. While a great deal of it rides on the heat treatement you give the blade, that is not the only thing to worry about. The blade design itself has a lot to do with the performance of the blade. A significant portion of the blades performance in that test also comes from the blade geometry itself. Things like spine thickness, distal taper, thickness behind the edge, edge geometry, etc. will dictate how well the blade can flex, how well the edge will hold up to chopping, how well the edge shaves, etc. Paired with the heat treatment of course. A big thick blade is not going to flex as easily and will have greater compressional and tensional bending stresses on its outer surfaces (meaning larger risk of failure). A chunky fat edge will hold up to chopping great, but may not cut a rope very well, and may not shave hair. How long the blade is will also affect how well it chops, but also how well it flexes in the bend test. etc. etc. etc.

Just some more things to think about.
 
Thanks for the info,It makes sence. Ive Tried hardning this steel again this morning at 1575 ,1625 and 1675 and have tried cooler temps in the past.As far as blade geometry goes i need to succesfully treat the blade before further testing of blade design.I really think this is not 5160,ive never had any trouble with other forging stee but ive never edged quenched as well,or try to make the knife that will pass the JS test.
 
The higher temps won't help most steels to harden (unless their critical temps are that high, but most "conventional forging" blade steels fall in the 1500 F ball park range, super generalized statement ;) )

If you quench at temperatures above critical (aside from haveing large grain growth) you actually are making it harder to harden the steel. If you look at a TTT chart, you'll notice what is known as the "pearlite noseline" and a very small section where you can miss it if you quench fast enough and enter into an unstable austenite phase that will eventually transition into the martensite microstructure. If you quench from a higher temp, you have to bring the steel from that higher temp to below critical (say 800 F for a lot of steels) in the same amount of time as you would if you quenched directly from critical (maybe on the order of 1-2 seconds for most blade steels, again generalization). The additional temp means greater amount of heat transfer has to take place in the same amount of time, which means to cool at the same rate you'd need a quench medium with a higher coefficient of convection (faster quench) to get it to harden. But doing this will impart more stress in the steel durring cooling (not to mention the large grain growth) and result either in blade failure, or a poor performing blade (maybe both).

Your edge quenching method could also be causing your lack of hardening. Either you are not getting the edge to cool quick enough to miss the pearlite noseline completly or you are re-entering the pearlite zone after you missed the noseline to begin with due to the residual heat in the spine, and only "partially" hardning the blade (possible bainite formation, etc). Think of it as over-tempering the edge with the heat left in the spine (not actually what is going on, but might be the easiest way to conceptualize it without the proper metallurgical background knoweledge).

When you edge quench, be sure to keep the edge submerged in the oil well past when the spine has lost its color. I usually wait until the spine cools below this point a few minutes, and then go ahead and cool the spine in the oil as well before removing the knife. If you have to rock the edge back and forth due to curvature, keep rocking the blade durring this time, etc. until you are sure things are cool enough that additional problems won't arise.

However, if you aren't getting much hardness out of the steel in any hardening case, its probably just that you got the wrong steel.

I'd say its probably best to just wait and get the new steel and try again. If you are still having problems, then its something you are doing (assume you get the right steel this next time around ;) ) and you can work on trouble shooting then. Otherwise the new steel may fix everything, so best to wait and see and eliminate that possibility first, rather than putting in more effort to try and fix something that may not actually need fixing :) .
 
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Thanks Graham, I read the TTT chart and understand what your saying, I increased my heats in order to see if im getting the blade to the oil without droping below 1525.Then I use the same method you mentioned above,rocking the blade in the oil making sure the residuel heat in the spine doesnt effect the hardend edge.I think your right, im going to stop testing with this steel and wait for the new stuff.
 
I've forged 5160 for a long time, I use a coal forge and hand cranked blower, hardly state of the art. I love 5160; It's a good, hard steel, and I've made choppers which went cleanly through a two inch branch. Now, ask me why it works, and I would ask you to just join me in a nighly forging session. The point is, there are guys who can't help but ask why something works, and there are guys who ask how it works.This is just my take, Go with the how!


Dave
 
David Stifle said:
I've forged 5160 for a long time, I use a coal forge and hand cranked blower, hardly state of the art. I love 5160; It's a good, hard steel, and I've made choppers which went cleanly through a two inch branch. Now, ask me why it works, and I would ask you to just join me in a nighly forging session. The point is, there are guys who can't help but ask why something works, and there are guys who ask how it works.This is just my take, Go with the how!


Dave
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could you point out in this thread the posts that have been a "why" ? I think this thread has been full of excellent information.
 
This is what I brought back from the ABS school. (5160 was all we had in Dec. 2008) Forge the tip and profile before the tang. Normalize three times - hold the blade in the dark and wait until all of the color is gone before the second and third heat. (You can hear the stress relieving as the metal "tings") We only did a full quench (although I've been doing edge quenches before and after the class). Once out of the tempering oven, because the entire blade was hardened, we put the edge in a pan of water and heated the spine with a torch until the blue temp. color was "chased" down near the edge. This softened the back enough to pass the 90 degree bend test.
I don't think there is any reason to draw the spine on an edge-quenched blade. Is that right, guys?
 
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Henry Cambron said:
This is what I brought back from the ABS school. (5160 was all we had in Dec. 2008) Forge the tip and profile before the tang. Normalize three times - hold the blade in the dark and wait until all of the color is gone before the second and third heat. (You can hear the stress relieving as the metal "tings") We only did a full quench (although I've been doing edge quenches before and after the class). Because the entire blade was hardened, we put the edge in a pan of water and heated the spine with a torch until the blue temp. color was "chased" down near the edge. This softened the back enough to pass the 90 degree bend test.
I don't think there is any reason to anneal an edge-quenched blade. Is that right, guys?
Click to expand...

So the edge stays completely hard.As I understand 5160 only gets to 63rc or lower and this would be possible.The very edge doesnt get any temper at all. Is this what your saying?
 
herlihy, I won't speak for Henry, but in my mind (and in my shop), I fully harden the blade, temper the entire blade, and then use the method Henry describes to "draw back" the temper on the tang and spine. A 63RC edge isn't going to be tough enough for the ABS test.

--nathan
 
I assume when Henry states "anneal" an edge quenched blade, he actually means temper.

Tempering serves more than just to bring back hardness. It is an important stress reliever, and possibly more importantly, it also brings the blade up close to the Ms point (martensite start point) and allows any austenite that was retained (did not convert into the hardened martensite structure) to finish transforming into martensite. A minimum of two temper cycles are recommended because the first serves to temper the martensite structure that formed in the blade, as well as convert and retained austenite. The second is then done to ensure the newly converted martensite is tempered properly as well. It is possible to have a significant amount of retained austenite in an untempered blade, and the blade will actually not be at full hardness (it can be quite puzzling at first if you don't know what is going on. You'll think the blade didn't harden fully and might be tempted to re-normalize and re-harden, but after tempering, it is suddenly hard, as it should be). Certain steels seem to have more of a tendency for retained austenite over others (simple steels are not at bad, but those with alloying elements are a bit worse with this issue).

I agree with Nathan. Temper the entire blade, at an overall lower temperature to get the edge hardness and toughness where it should be, and then after this, if you need the spine to be softer, torch temper it back. Even differentially hardened blades (be they edge quenched or clay insulated) should be tempered.

Best thing I can recommend for determining the proper temper (as well as hardness) for an edge is to do an edge flex test (or brass rod test). That will tell you right away if your edge is going to chip and you need to temper a bit more, or if you've over tempered and the edge will roll/fold, and you (unfortunately) have to re HT the whole thing.
 
You might also go to ED CAFFERYS website he had a tutorial that is called how to pass the abs test and it is with 5160 he tought me and my knife passed the test with know problem at all this was a couple of years ago at a class at Bronks Knife works.
 
As I am up against a deadline I do not have time to read the whole thread - sorry.
Here is what I do:
after forging normalizing I use a 988 f. Temper for the entire blade in my Paragon hold at 988 for two hours, I do this three times, slow up to temp, and cool down in Paragon until cool, to the home freezer and back to the Paragon for a total of three 988 f. tempering. I used to use the 1440 degree temper, then slowly started dropping the temperature until I reached 988 as good enough. Never had a tang break and can always drill them should I want to.

Then grind and harden. I never get the tang hot enough to harden, using a torch heat only the part of the blade I want hard and quench.
 
Sorry for the confusion. The blade is still put in the temper oven before drawing the spine.
As far as the annealling statement, I meant to say, ..."no need to draw the spine on an edge-quenched blade. Is that right, guys?"
 
Are you sure that the edge quenching isn't tempering the edge when you pull it out of the quench?
 
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