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High-Performance Blades Sharing ideas for getting the most out of our steel.

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  #16  
Old 12-02-2008, 06:09 PM
Chris Meyer Chris Meyer is offline
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Excellent post Kevin, save that one for your upcoming book...


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  #17  
Old 12-02-2008, 10:44 PM
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bindlestitch bindlestitch is offline
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First I just want to say thanks for all the excellent info in this thread.
I've been using o-1 pretty exclusively this year but just recently went back to 1095 because of the huge price difference. I've made a few 1095 blades and haven't hand any warping or cracking, quenching in veggie oil. But reading this info I'm thinking I didn't get to full hardness because: A, I quenched at non magnetic instead of getting to 1475.
B, I didn't hold my temp for more than a few seconds.
My question is this:
Is there any way, using a forge and magnet, that I can judge by color (or some other means) when I've reached 1475?
I know this would only solve half my problem, because I have no way of holding at 1475 with a forge accurately.
Any help is much appreciated.
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  #18  
Old 12-03-2008, 08:14 AM
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Alan L Alan L is offline
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If you're in a dark room and you have good eyes, plus a forge that can be dialed way back, you can visually observe the transition point. I'm not talking about colors, either.

The phenomena of decalescence and recalescence are your friends here. With the forge barely running in the low orangy region, say 1500 or so, put a blade in and watch it as it comes up to temperature. It will go to dull red, but then as it starts to get into the orange range (as seen in darkness, it's barely red in bright light) you will see what looks like shadows swirling around inside the steel. as the blade heats a little more, the shadows will disappear, running up the blade towards the tang. At the edge of this shadow/no shadow zone there will be a dark line. What you are seeing is the energy being absorbed by the iron and carbon crystal lattice as the crystals change phase from body-centered cubic to face-centered cubic, which means you're ready to quench (or hold at that temperature for a soak) once all the shadows are gone.

If you are just normalizing, pull the blade as soon as the shadows disappear. Watch it as it cools, and you will see the shadows reappear, but this time there will be a bright line at the leading edge. This is the phase change back to body-centered cubic structure. It releases energy instead of absorbing it, thus the bright line.

I do this in a coal forge with the lights off, and no air blast. If you're using propane you just need to turn it down until it's only just hot enough to cause the transition.
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  #19  
Old 12-03-2008, 08:34 AM
Kevin R. Cashen Kevin R. Cashen is offline
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Quote:
Originally Posted by bindlestitch
First I just want to say thanks for all the excellent info in this thread.
I've been using o-1 pretty exclusively this year but just recently went back to 1095 because of the huge price difference. I've made a few 1095 blades and haven't hand any warping or cracking, quenching in veggie oil. But reading this info I'm thinking I didn't get to full hardness because: A, I quenched at non magnetic instead of getting to 1475.
B, I didn't hold my temp for more than a few seconds.
My question is this:
Is there any way, using a forge and magnet, that I can judge by color (or some other means) when I've reached 1475?
I know this would only solve half my problem, because I have no way of holding at 1475 with a forge accurately.
Any help is much appreciated.
Most who use a magnet and a forge have been the beneficiary of a convenient drawback that in this case is a plus, and that is how the magnet got its exagerated reputation as a good indicator. 1414F is not enough for many steels but when working in a forge it is virtually impossible not to overshoot the mark by 50F - 75F, which will put you right in the sweet spot. To help calibrate things even tighter I agree with Alan about watching for decalescence, the magnet tends to stay with 1414F while each individual alloy will tell you what it is doing with those shadows and colors.

For very simple equipment I would recommend 1084 or 1080 over 1095, as there is no extra carbon to have to worry about arranging or going where you don't want it, they will also go into solution the quickest, and thus eliminating some of the need for soaking longer. 1080 and 1084 also have a bit more Mn lending them a hair more hardenability than 1095 and making them easier to heat treat with less than optimal quenchants.
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  #20  
Old 12-03-2008, 09:08 AM
AcridSaint AcridSaint is offline
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Hi Kevin, I wondered if you could confirm something for me. From what I know of the steels, 1095 is far more susceptible to grain growth. It's my understanding that the Mn in 1080/1084 type steels has a side benefit when it comes to grain growth. Would it be accurate to say that, in addition to the deeper hardening, this additional Mn helps in some way to retard otherwise rapid grain growth?


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  #21  
Old 12-03-2008, 12:25 PM
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bindlestitch bindlestitch is offline
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Quote:
Originally Posted by Alan L
If you're in a dark room and you have good eyes, plus a forge that can be dialed way back, you can visually observe the transition point. I'm not talking about colors, either.

The phenomena of decalescence and recalescence are your friends here. With the forge barely running in the low orangy region, say 1500 or so, put a blade in and watch it as it comes up to temperature. It will go to dull red, but then as it starts to get into the orange range (as seen in darkness, it's barely red in bright light) you will see what looks like shadows swirling around inside the steel. as the blade heats a little more, the shadows will disappear, running up the blade towards the tang. At the edge of this shadow/no shadow zone there will be a dark line. What you are seeing is the energy being absorbed by the iron and carbon crystal lattice as the crystals change phase from body-centered cubic to face-centered cubic, which means you're ready to quench (or hold at that temperature for a soak) once all the shadows are gone.

If you are just normalizing, pull the blade as soon as the shadows disappear. Watch it as it cools, and you will see the shadows reappear, but this time there will be a bright line at the leading edge. This is the phase change back to body-centered cubic structure. It releases energy instead of absorbing it, thus the bright line.

I do this in a coal forge with the lights off, and no air blast. If you're using propane you just need to turn it down until it's only just hot enough to cause the transition.
Alan,
Thank you kindly. I've seen exactly the process you've described but just never knew what it was. I too use a coal forge with the lights off, actually outside at night is when I us it, so I can usually see what the steel is doing.
Much obliged again,
Israel
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  #22  
Old 12-03-2008, 12:28 PM
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bindlestitch bindlestitch is offline
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Quote:
Originally Posted by Kevin R. Cashen
Most who use a magnet and a forge have been the beneficiary of a convenient drawback that in this case is a plus, and that is how the magnet got its exagerated reputation as a good indicator. 1414F is not enough for many steels but when working in a forge it is virtually impossible not to overshoot the mark by 50F - 75F, which will put you right in the sweet spot. To help calibrate things even tighter I agree with Alan about watching for decalescence, the magnet tends to stay with 1414F while each individual alloy will tell you what it is doing with those shadows and colors.

For very simple equipment I would recommend 1084 or 1080 over 1095, as there is no extra carbon to have to worry about arranging or going where you don't want it, they will also go into solution the quickest, and thus eliminating some of the need for soaking longer. 1080 and 1084 also have a bit more Mn lending them a hair more hardenability than 1095 and making them easier to heat treat with less than optimal quenchants.
Kevin, Thank you kindly, too.
I will definitely try some 1084 or 1080 on the next go around. It sounds like that'd be right up my alley.
Much obliged for the great information and the fact that all of you guys share it freely.
God bless,
Iz
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  #23  
Old 12-04-2008, 09:29 AM
Kevin R. Cashen Kevin R. Cashen is offline
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Quote:
Originally Posted by AcridSaint
Hi Kevin, I wondered if you could confirm something for me. From what I know of the steels, 1095 is far more susceptible to grain growth. It's my understanding that the Mn in 1080/1084 type steels has a side benefit when it comes to grain growth. Would it be accurate to say that, in addition to the deeper hardening, this additional Mn helps in some way to retard otherwise rapid grain growth?
Other than some particle drag on the diffusional process I don't why the manganese should retard grain growth all that much. Alloy carbides, yes, since they really like grain boundaries and require heavy heat to displace, but Mn will most likely be in the form of manganese sulfide particles if it is doing its job. 1095 may appear to get course grain due to grain boundary cementite or forming courser micro-constituents to the phases due to the extra carbon.

The very action of deeper hardening will contribute the fine internal structures and the appearance of finer grain due to avoidance of courser pearlite and a penchant for finer low temperature phases and the higher rate of strain driven nucleation when those lower or quicker forming structures are reheated.

The proeutectoid cementite in the 1095 could also contribute to grain refinement if it is placed in the right spots in the right condition. But if it gets locked up in the grain boundaries or in very coarse forms then it will indeed contribute to large grains that will not want to go away at average bladesmith tempertures in that steel, while the 1084/1080 will have no proeutectoid cementite to have to deal with. This is yet one more very good reason to work with 1080 or 1084 until you have the experience and equipment to deal with the special issues of 1095.

Last edited by Kevin R. Cashen; 12-04-2008 at 09:31 AM.
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  #24  
Old 12-04-2008, 09:34 AM
AcridSaint AcridSaint is offline
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Hi Kevin - I was under the impression that the Mn did indeed provide some solute drag, but was unsure. Your explanation makes more sense, however. Thanks!


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  #25  
Old 12-04-2008, 12:53 PM
T. Hendrickson T. Hendrickson is offline
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This thread has turned out to be far more informative than I expected. Thanks for all the great info, I feel like I know just what my mistakes were and how to avoid repeating them in the future.


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  #26  
Old 12-05-2008, 12:05 AM
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chiger chiger is offline
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Quote:
Originally Posted by T. Hendrickson
I feel like I know just what my mistakes were and how to avoid repeating them in the future.
Yep, but there are plenty of new ones to make Thayer!

Sorry for not getting back on the repair deal. Computer crashed. Just got a chance to get back on.

I had a feeling that is what happened. It's all to common. Got one to fix myself that I broke driving on a bolster. Read through the rest of the post after your question and didn't see it answered so I'll take a shot. I'm no blade smith either. I just do what works.

Yep, arch welding is the easiest way. I'd notch the steel at 45 degrees or so on the sides to about 1/3 of the way deep. Leave the top and bottom of where the tang and blade meet as is. I use a dremel with diamond bits to do it.

The object is to get a notch on both sides that follows the crack and leaves a 1/4 or 1/3 of the thickness in tact in the center to index the joint back together. And keep the weld from blowing through to the other side.

Then clamp the two parts together on something that won't burn and heat the area around the joint till it's at least 450-500 degrees. I think actual procedure for 1095 might call for 850, but I've not had to go that high on the few I've done and had no failures. Use the smallest stick you can and the lowest setting that will weld without sticking.

I know. That's not what your taught. Your taught to get good penetration. And you do want penetration, but if it's too hot it will cut the original steel around the weld and leave dimples you can't get out with sanding. So at least on the final passes you just want it to stick more than penetrate.

Run a bead on one face and let it cool while clamped down. Turn it over, clamp it back down and repeat the procedure. Let it cool and then clean ALL the slag out. You may have to resort to the dremel to get it done. Repeat the procedure until the weld notch is filled above the original metal.

Oh, and use the welder to put that radius in where the tang and blade meet so it doesn't happen again. And use at least a 7018 rod. and there are some better rods for hardenable/tool steel if you can find them.

Now just grind it back to original profile and re heat treat. This time, don't harden the whole blade and leave the tang and spine softer/tougher using some of the info you've gleaned here. Should be fine.

I'm sure there's some welding engineer reading this thinking, "You dumb A, that won't work. You have to do...!" And they may be right. But as I said, I've used this procedure a couple times and after a some failed attempts they are in use today.

Hope this helps.

chiger,
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  #27  
Old 12-05-2008, 12:54 AM
T. Hendrickson T. Hendrickson is offline
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Thanks Chiger!

My welding experience is *very* limited, so chances are I'll make a mess of it, but I might as well try it. That blade's not doing any good sitting on my bench, and it would be fun to take it to destruction on assorted test materials.


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