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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

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  #1  
Old 03-16-2016, 08:46 PM
WNC Goater WNC Goater is offline
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Problem with 1095 and I have no answer

Got a couple new bars of 1095 from NJSB. I heat treated two blades yesterday. Heated to 1475° and quenched in 130°-140° canola. After quenching, I ran a file along the edge and it seemed to bite a bit. Then I tempered at 425° for two hours.

So before doing anything, I sharpened the edge and rolled it across brass. The fine edge bent.

So I scratch my head. I've had good results with this process on some of my early blades but have been using 1084 recently.

Today I used my electronic meat thermometer that I know is accurate. I found my dial thermometer I used was off by about 40° or so. That means my quench oil was in the neighborhood of 175° and my tempering oven was too hot. Okay, so there's my problem.

So I redo today, heat the two blades to 1475° for 10 minutes, quench first in canola @ 130° then I quench the second one. The second one, the smaller of the two blades, the file bites into. I check the oil and apparently the first blade heated it to over 150°. So I allow the oil to cool, reheat the blade to 1475° and quench @ 135°. I temper both of them a bit lower at 380°-385°.

This evening I sharpened an edge and did the brass rod test. The very edge bent on the smaller blade. If you look in the picture, you can see the rolled edge as shiny.

I have no answers, and realize this is a lot of info. Any means of salvaging this blade? Any ideas of what's happening?



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  #2  
Old 03-17-2016, 12:40 AM
Doug Lester Doug Lester is offline
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A temperature of 1475° should have put adequate carbon into solution so I doubt that your problem lies there. The 1095 probably has a cooling curve that is more to the left of the 1084 which is a bit deeper hardening. So it makes me wonder if the canola oil is doing the job for you. It could be right at the border of beating the nose of the curve. Your solution may be to get some commercial fast quenching oil or try brine.

By the way, how did the first knife turn out on the edge flex?

Doug


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Old 03-17-2016, 06:17 AM
WNC Goater WNC Goater is offline
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The first knife has a much heavier blade and I had difficulty making it flex. What I did see SEEMS to be okay but I'm not totally convinced. I batoned it into some hard maple wood and drove the tip in then pried sideways. Nothing bent or curled. But considering this thinner blade I'm not totally convinced and it makes no sense one would be fine and the other not okay.

I have quenched about 2 dozen knives in this same gallon of canola and wonder if it has a "useful life"?

I may need to try the brine. The first 1095 I got from Jantz and this batch from Aldo. In between I used some 1084. Maybe this is a bit different and the canola is just past the nose as you suggested. Dunno.

What little I've read, brine is mixed about 10% by weight so about .80 pound to a gallon of water. Is the brine heated before the quench? I'll do more research on the brine.

For whatever reason I'm not getting a fast enough quench with the canola and this batch of steel so I guess I'll risk a cracked blade and try the brine.


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Old 03-17-2016, 06:44 AM
jmccustomknives jmccustomknives is offline
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You know, come to think of it I had canola oil go bad. It wouldn't even harden 5160. Why not get some Parks 50. Aint nothing worse than hearing the ominous "TINK" when you quench. lol.
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Old 03-17-2016, 07:05 AM
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Crex Crex is offline
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Yeah canola does have a life span and needs to be replaced regularly. Might also consider a larger quench container if doing more than a couple of blades. It is also advisable to stir the quench for a more even heat dispersal throughout the quench.
Brine was always a hit or miss for me - one is one too many "tinks" for me.

Parks 50 will give better consistent results with 1095.


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  #6  
Old 03-17-2016, 10:56 AM
WNC Goater WNC Goater is offline
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Upon checking around I seem to run up against what a lot of guys do. That is, it seems Parks is only available in 5 gallon containers which, combined with the shipping charges, is not an insignificant expense. If this (my knife making) grows into something more significant, then certainly the expense can be justified.

In the meantime, I think I will try some new, fresh canola realizing that, at best, this isn't an ideal quenchant with 1095, and maybe experiment with some brine. But I agree Crex, that one "tink" is too many considering the effort already put into a blade before the quenching stage.
But heck, I'm new at this and it IS a learning process...

I haven't found a clear answer as to whether the brine should be heated or not.

And I wonder, is there a limited number of times a blade can pass through the "process" before the structure is altered to the point of no return. It seems forging a blade would answer that question. Also wondering if I should anneal the blades before trying another hardening/tempering process.


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Old 03-17-2016, 10:48 PM
Doug Lester Doug Lester is offline
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As far as whether or not brine should be heated, my experience with it, which was some time ago, was to heat it to about 160° before quenching. I can't say that it is a must but the few blades I quenched in brine didn't break.

As far as how many times you can put a blade through the austenizing and quenching process before before you make some irreversible change to the steel I would say that there really isn't one but with a caution that you might accidentally refine the grain of a shallow hardening to the point where you're not going to get any hardening. And that's a big might. If that happened all you would have to do is heat the blade up to where there is grain growth and then try to bring it back down a bit.

Doug


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Old 03-18-2016, 10:54 AM
WNC Goater WNC Goater is offline
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I just held them @1475° for 10 minutes and quenched in 125° brine @ 10% by wt. Grabbed them both out of the oven at the same time and plunged them in. Loud and dramatic quench.
Still warm I slid a file across the edges. The heavy knife skated the blade pretty good, the thinner blade...I don't know, seemed the file tried to bite somewhat. I cannot imagine why. Maybe it's just thinner, maybe my file is extra hard. But I cannot imagine it didn't harden. I believe the laws of physics and metallurgy DEMANDS that it harden, it has no choice! Maybe I'm wrong.
Both blades are in the tempering oven and I'm holding the temperature at about 375°. I figure if they are too hard I can temper them again at 400°.
I'll sharpen the edges tonight and see what happens.
If this fails I'm at a loss and will probably have 7 feet of 1095 for sale cheap!


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Last edited by WNC Goater; 03-18-2016 at 11:53 AM.
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  #9  
Old 03-18-2016, 11:35 AM
samuraistuart samuraistuart is offline
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WNC.....have you accounted for the layer of decarb that forms during heat treating? Not to be confused with scale, decarb is a layer of steel under the surface that has been robbed of it's carbon because of the heat treating. (the carbon that comes out forms the scale). A file will always bite into the decarb layer, and it must be sanded thru in order to reach the hardened steel.

Can't tell you how many times this has been the culprit in instances like this. It's nearly always decarb. Then temps being off. Then wrong steel ID.
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Old 03-18-2016, 11:54 AM
WNC Goater WNC Goater is offline
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Quote:
Originally Posted by samuraistuart View Post
WNC.....have you accounted for the layer of decarb that forms during heat treating? Not to be confused with scale, decarb is a layer of steel under the surface that has been robbed of it's carbon because of the heat treating. (the carbon that comes out forms the scale). A file will always bite into the decarb layer, and it must be sanded thru in order to reach the hardened steel.

Can't tell you how many times this has been the culprit in instances like this. It's nearly always decarb. Then temps being off. Then wrong steel ID.

No I had not accounted for that. I hope you are correct. Regardless, you've brightened my day and given me renewed hope!

And thanks to everyone for your help. I'll report on the edge when I check the results this evening.


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Old 03-19-2016, 07:54 PM
WNC Goater WNC Goater is offline
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I haven't really worked on the smaller blade but the larger one I started finishing up. I did the final grinding and then ground the secondary bevel and sharpened it up. I took it to hair shaving sharp than took a piece of red oak lumber and beat the crap out of it, whittled it down, chopped on it, beat the edge with the oak, twisted etc. No mark on edge, no chips, curls and it would still shave hair. So I think I got there on this blade.

It seems to have a very faint hamon, not sure that is normal or if that is what I see. There is also a very slight "orange peel" on the bevel and flats, but not near the edge. It is slight and I need magnification to see it. Don't know what that's about.


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Old 03-20-2016, 10:32 PM
Doug Lester Doug Lester is offline
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The slight hamon is a possibility because 1095 is a shallow hardening steel and in thin cross sections, such as a knife blade, it will only harden to a certain thickness. This also depends on the grain size with smaller grain decreasing hardenability. As a result the blade will only harden up to that point, usually about an 1/8" with a good fine grain. Thicker than that pearletic steel is formed. You could try to bring it out more with ferric chloride or even lemon juice. Don't know about the orange peel effect. Normally I would suspect overheating but you use a high temp oven for austenizing.

Doug


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Old 03-21-2016, 08:39 AM
Kevin R. Cashen Kevin R. Cashen is offline
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Here we encounter the frustrating limitations of “flex” tests in evaluating heat treatment. The only part of gradual loading and deformation, such as over a rod, that heat treatment effects is what occurs beyond the elastic limits (proportional range). Thus one must either bend or chip the edge to see the heat treatment effects, and before that all of the load level to deformation observed is determined entirely by the grind, not the heat treatment, and yet the brass rod continues to be a curious standard. In this case what makes the information gleaned come into any useable focus is coupling it with the file check as well. The file doesn’t directly relate to penetration hardness but it at least measures a form of hardness.

1084 has one of the highest levels of Mn in the 10XX series and thus has some of the deeper hardening levels- although it is still a shallow hardening steel, I still always scratch my head when it is described as a deep hardening steel. On the other hand 1095 has some of the lowest Mn levels and thus it’s about the shallowest hardening steel we regularly encounter; so much so that I use it for all of my quench evaluation studies when consulted for quenchant analysis. The only oil, so far, that I have been able to achieve full hardening in 1095 much greater than 3/16” is Parks #50, with Houghtoquench “K” coming in a close second.

Another clue I got from the situation described is the hesitation to buy 5 gallons of quenchant- not a problem there but it indicated that less than 5 gallons could be being used currently, to which I begin to ask what the quantity is? If it is around 2 gallons or less, depending on the shape of the container, you may not have enough volume for proper thermal extraction. Also, having room to be able to agitate, or circulate the oil is very important, particularly with 1095; just holding it still in the oil will give you all kinds of mixed results.
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1084, 1095, 5160, bee, blade, blades, brass, carbon, edge, file, first knife, harden, heat, hot, knife, knife making, knives, making, problem, quenched, rod, scratch, steel, wood


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