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jake cleland

clay hardening 1080

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finally found a supplier for 3/16" 1080 here in the uk, which i bought primarily for clay hardened pieces. While i know that 1080 isn't the best 10xx steel for showing hamon, it's a heck of a lot better than the O1, D2 and spring steels which are the only things i've been able to get in sheet/bar stock here.

so my question is: how do i go about heat treating this steel for the best hamon? oil or brine quench? normalising cycles? edge thickness at ht? clay thickness and placement?

i'm planning on doing the first few pieces stock-removal, which i'm still more confident/faster at, starting probably next week, between finishing my last sgian dubh order for the moment, and starting on a pair of wedding rings next month - i want to get a couple of blades shaped and hardened before i start the rings so i can carve waxes for them and cast fittings along with the rings.

i know that the key is going to be experimentation, but any leg up would be greatly appreciated,

cheers,

Jake

 

 

can you point me in the direction of summa dat 1080 in the UK please? Would be much appreciated.

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hi Guys,

 

I did my first Ht on a clay coated 1080 blade the other day, using a charcoal forge. Proabably got it way too hot, as it was orange-red. Anyway, checked with magnet then into the motor oil quench. Came out with a great hamon, but file bites into edge easily. also, the area below the clay line almost looks like damascus.

 

Guess I'll do it again, but I don't know why it didn't harden. Too hot? Oil too thick? Just not sure. Any advice?

 

Thanks,

Dave

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Maybe need to preheat oil a little.

 

Another thing I've read to check is to make sure you don't have a small layer of decarb which could be covering the hardened steel.

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Edgar,

 

The oil was heated to about 150 degrees. Even though the blades were heated to no-mag, maybe I needed to soak them a little. I did 4 blades, 1080 & 5160, and none of them hardened. I've read and read on Ht before doing this, and thought I knew what I was doing, but I made some errors somewhere along the line. Well, there's nothing like practice.

 

Bewildered and Confused,

Dave

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Edgar,

 

The oil was heated to about 150 degrees. Even though the blades were heated to no-mag, maybe I needed to soak them a little. I did 4 blades, 1080 & 5160, and none of them hardened. I've read and read on Ht before doing this, and thought I knew what I was doing, but I made some errors somewhere along the line. Well, there's nothing like practice.

 

Bewildered and Confused,

Dave

 

I'm not a great smith but I'd say a soak might help a bit. In my forge the color at hardening appears more orange than red. Not a red orange so much as true orange. I had to verify it with a temp controlled atmosphere, ofcourse. It is possible the oil is too slow, depending on what it is. I've used motor oil for a long time, cut with diesel fuel and a couple cups of dish soap. Makes a very thin oil that works pretty well for producing very hard blades... My quench tank holds 30 gallons so I have plenty of room to move the blade to avoid vapor jackets... Do you have enough oil to allow it to extract heat effectively?

 

You are sure that they didn't harden, that it isn't decarb? I've had that happen a few times, the decarb causing a hard blade to appear soft.

 

Just a few thoughts....

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Scott,

 

I think you put your finger on my problem, the blades were not orange, but orange red, or even closer to dull red. And I don't think the motor oil worked fast enough. I need to cut it as you suggested, and certainly add more to my tank. Heck, since I have to temper them in the oven in the house, I should go to a veg oil so I don't hear the wife yelling. It isn't decarb, the blades are truely soft. The second time's the charm!

 

Thanks for the ideas,

 

Dave

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Motor oil is not a good quenchant - for a lot of reasons. It contains a lot of nasty stuff in it that is toxic and difficult to dispose of. Second, the cooling curves are poor.

 

If you use a quality quench oil, the results will be excellent and consistent. Use a medium speed oil, so that the thin sections harden, and the thick sections do not harden....depending on the hardenability of the steel, a fast oil would also work.

 

I can help you select if you PM me...

 

Scott

 

 

I really like the aqueous polymer PEO, but it had it's own set of issues to deal with. But for making hamon, oh Baby is that stuff neat! And it washes up with water too.

 

Howard - where are you located? Where did you get your PEO - I assume it is Aqua-Quench 3600. What sort of concentration do you use?

 

Thanks

 

Scott

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I am in central Iowa, and yes, that was/is the PEO I have, from Houghton. The really great hamon was happening with very low percentage solutions, at 7-10%. I ended up settling for about 8%, and it works great. The problem, from my point of view, was that the blade curvature induced in the quench (sori) was less than that acheived with water, and even worse, it relaxed upon tempering. I could live with it, if it weren't for that. The hamon than can be created are truly spectacular, as the quench speed can be fine tuned to the steel in a manner not easily done otherwise. It is kinda spendy, too, but at only 8% it's not that big a deal. The other problem was that I austenitize in high temp. salt, and the salt is also water soluble, so, the result is that your refractometer readings go right out the window, in trying to keep the polymer solution right, because the instrument is now reading a binary solution, which throws it off. I ended up having to just make a new solution for every batch of heat treating. PITA, but it was the sori issue that really pushed me back to water and accepting the part loss percentage. I can make a far cooler hamon with PEO, however.

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Howard, I came to same conclusions with the polymer. I don't want to drag up an old subject, but the way the polymer affected the sori has had me scratching my head. It seems like we can take the speed of the quench out of the equation or am I wrong on that?

 

I love it as a quenchant though despite the pita. Too bad about the sori. There has to be a thermal solution to that problem.

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I don't know. I have scratched my head and pondered this a lot. Why the sori would change has me puzzled. One would think, logically (maybe) that if the water quenched blade doesn't change, and the oil quenched blade doesn't change, the polymer quenched blade shouldn't change, either, but they DO change when tempered, and it always relaxed more than I wanted. Of course one could always put it in service untempered, the way many Japanese made blades have been, but then you MUST stay below .6C or you're asking for BIG trouble with untempered high carbon martensite. I can only conclude that there must be some microstructural change occurring during tempering (which we know, to some degree, that tiny carbides precipitate out, and the martensite loses some hardness as the structure relaxes a little bit). But what I can't fathom is why the polymer quenched blades are so pronounced in this. There must also be some change occurring in the pearlite body of the blade, but that makes no sense at all. All the evidence points to retained austenite in the polymer quench in greater portion than with the other quenchants, but that doesn't make any sense either, as that (quenchant) is the only change, and the heat extraction rate was greater than oil, which apparently does not suffer the same difficulties. Polymer and oil gave the same kind of results in terms of negative sori on long blades at percentages greater than 10%, which is around the same quench "speed" as Brownell's "Tough Quench", but not as fast as the Park 50 or something similar, which apparently some of these guys are using and getting positive sori ? I don't remember if there was any change in the sori on those blades (the negative sori, or recurved ones), and I don't know if I even pusued that, and they were likely re-heated and done over, regardless.

 

I dunno, it would make a great research project if one had the time...(thinking wistfully of the pursuit of knowlege for it's own sake instead of the filthy lucre)

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You guys are drawing my interest to this polymer stuff and negitive sori is not a problem with the style of my blades. Guess I'll have to get some :)

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Yeah, the park 50 gives about half the sori on a given blade as water will, with a hamon that's mostly the same, and about all you need is ashi to influence the hamon, so it's kinda cool. I don't think utsuri and stuff is as easy with the park 50 though.

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just clay coated and heat treated a folder blade of 1080, and from what i can see so far it has a pretty good hamon, but it warped very slightly at the riccasso and now it runs slightly sqint. it's just a friction folder, so i'm not bothered about getting it perfect, but i don't want it to rub on the stag when opening/closing. so far ive tempered it once to straw colour for 30 mins just to draw the stresses, but i want to know what temp (and colour as i dont have an accurate temp guage)to draw it to before i try to tweak it. any advice?

cheers,

jake

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I straighten my folder blades right after the quench, you have a few mins to do this and the blades are very easy to bend with hand presure. I have found blade much harder to straight after temper but a blade with hamon should be no problem for a slight tweak.

Edited by Don Hanson

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I don't know. I have scratched my head and pondered this a lot. Why the sori would change has me puzzled. One would think, logically (maybe) that if the water quenched blade doesn't change, and the oil quenched blade doesn't change, the polymer quenched blade shouldn't change, either, but they DO change when tempered, and it always relaxed more than I wanted. Of course one could always put it in service untempered, the way many Japanese made blades have been, but then you MUST stay below .6C or you're asking for BIG trouble with untempered high carbon martensite. I can only conclude that there must be some microstructural change occurring during tempering (which we know, to some degree, that tiny carbides precipitate out, and the martensite loses some hardness as the structure relaxes a little bit). But what I can't fathom is why the polymer quenched blades are so pronounced in this. There must also be some change occurring in the pearlite body of the blade, but that makes no sense at all. All the evidence points to retained austenite in the polymer quench in greater portion than with the other quenchants, but that doesn't make any sense either, as that (quenchant) is the only change, and the heat extraction rate was greater than oil, which apparently does not suffer the same difficulties. Polymer and oil gave the same kind of results in terms of negative sori on long blades at percentages greater than 10%, which is around the same quench "speed" as Brownell's "Tough Quench", but not as fast as the Park 50 or something similar, which apparently some of these guys are using and getting positive sori ? I don't remember if there was any change in the sori on those blades (the negative sori, or recurved ones), and I don't know if I even pusued that, and they were likely re-heated and done over, regardless.

 

I dunno, it would make a great research project if one had the time...(thinking wistfully of the pursuit of knowlege for it's own sake instead of the filthy lucre)

 

Bare with me here for I have little or no practical experience with this, but I have been pondering and reading everything I could find about this phenomenon for years now. I briefly discussed it with John Verhoeven too but not far enough to reach any deep conclusion.

I'm strongly suspecting that the difference in curvature (oil/water) and in this case polymers has more to do with pure mechanical effects than metallurgical one.

1- The "speed" of quenchant is not a single characteristic, it's more like an average. Reality seems clear that in fact each quenchant (due to various effect, one being the vapor properties) has a curve of cooling, i.e. the heat transfer is dependent of the temperature, producing a different speed at each point of the cooling. That in itself makes that a particular physical quenchant, even of differing "speed" (maximum cooling rate or average cooling rate) have a same curve shape resulting in a similar behavior as to the sori.

2- The cooling evolution (speed/gradient within the blade) introduces a combination of stress/deformation into the blades that are essentially a factor of time. For example when the edge contracts due to cooling depending on the state of the spine at that time (temperature, maleability and position relative to perlite cristallisation) that contraction can introduce either a stress loaded perlite, or a mechanical deformation of the more maleable austenite (i.e different sori). Once in turn the spine contracts (and the edge expands slightly due to martensite formation at the same time or not) then the blade behaves again in different manners.

3- The "penetration" of the quenchant into the clay, or relative "wetability" of a particular quenchant and clay combination could play a factor as well (in combination too with the vapor characterisitcs of that particular quenchant)

 

I higly suspect that the phenomenon of sori is identical in essence to welding deformation as well as heat straightening of metal (like in bodywork). A typical experiment is to close a heavy C frame with a thin steel bar (to form an O of sorts) then heat up the thin bar and it will either brake or bend the C frame when cooling. (therefore mostly unrelated to a bigger martensite crystal although that plays a small part). It's all about differential timings and differential states of maleability within the blade section.

 

So in short sori would be a mechanical effect depending strictly on shape of the cooling curve for a particular type of quenchant, and also to some extent its interaction with the clay, the geometry of the blade and the method of quenching (spine first or blade first). In other words we keep trying to find a metallurgical answer (carbides, cristals, etc..) but it's purely mechanical (dilatation/restraint, deformation, stress and timed gradients thereof).

 

If that hypothesis is correct, then the sori variation in polymer quenching tempering could be explained by the state reached being an intermediary state between water and oil. Water deforms the spine more therefore introducing sori, oil deforms the spine less, and polymer creates an intermediary metastable state that tempering temperature is enough to complete/reverse the mechanical evolution (similar to the straightening that is done with a block of hot copper)

 

This is pure hypothetical theory and it's in rough shape, but I'd like the people with much practical experience to think about it and see if that makes sense with what they've observed and know. Anyway just a thought! I'm sure Dr Scott can also deny/confirm and expand on some of this. I'd like to conduct some experiments but I don't have access to metallurgical labs or precise enough equipment to do the forging part without major variation factors (no less, maker lack of repeatability due to inexperience). Maybe it should be taken out of this thread too so as not to hijack, sorry.

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I do not disagree at all, but the one puzzle remains, even if the hypothesis (that it is mechanical, and not metallurgical) is correct. Why does the sori relax upon tempering ?

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ok, another question. with my normalising cycles, should i be decarburising the blade to reduce hardenability - 0.8% carbon seems a little high to get good activity - or is it all about grain size?

so far i've been starting my normalising about 1600f and coming down to about 1400. is there any advantage to going for sucessivly cooler heats beyond this - as in sub-critical? i'm starting to get what i think are quite nice hamons, but they're not very active, and i'd like to start getting some wilder effects. once again, any help would be appreciated.

 

(curse this forum - a year ago i was happily just heating things up to critical and dunking them in oil; now i'm on a mission, and i can no longer seem to finish anything - as soon as i get a blade polished i just want to make another one, and i've lost all interest in stainless. my customers, unfortunately, have not. end rant.)

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Activity in the hamon is a combination of a lot of factors, they can be plenty active at .8 C or even higher. Some kinds of activity seen in Japanese blades are dependent on lower carbon, and long, high temperature heats prior to the quench. Large nie, specifically. I cannot get that with the heat tretament methods I use, all the nioi you want, but no nie. Other kinds of activity in Japanese blades is dependent on the material being welded many times, and yet still having some inconsistencyl.

 

You have aquired the syndrom, there is no hope Jake, you are doomed to this now. ;)

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I do not disagree at all, but the one puzzle remains, even if the hypothesis (that it is mechanical, and not metallurgical) is correct. Why does the sori relax upon tempering ?

 

 

It is both a mechanical and metallurgical issue. At the edge, the microstructure is martensite, and at the backside, it is predominately pearlite. There is a volume expansion of about 4% due to martensite transformation. This causes some residual stresses. As the martensite tempers, some of the carbides precipitate out, resulting in a relaxation of the stresses, and a change in the volume. Hence the sori relaxes.

 

Hope that helps.

 

Scott

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I do not disagree at all, but the one puzzle remains, even if the hypothesis (that it is mechanical, and not metallurgical) is correct. Why does the sori relax upon tempering ?

As Scott said, that's part of what I was trying to say.

In other words I'm trying to say that maybe the polymer quenching introduces a state that is a bit more "on the edge" (or unstable) in the quenching mechanical evolution and the energy introduced during the tempering is sufficient to make it evolve further. While the oil or water quench would create a more stable state (obviously I guess) hence not being signifiantly affected by tempering. Now on the metallurgical importance of the secondary transformation during tempering (retained austenite , etc..) I don't know how much of an effect it has and I trust Scott to have a way better idea than I would.

 

Once again it's just hypothetical and an attempt to help maybe a little bit in the aggregation of experience and thinking that is required to better understand what is happening.

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Attached is a paper by Tatsuo INOUE, on the Science of Tatara and Japanese Sword - Traditional Technology viewed from Modern Science, ICBTT 2002. It gives a good explaination from a metallurgist point of view regarding the formation of the sori. I think that this might clarify things a bit.

 

Scott

International_Conference.pdf

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