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Jesus Hernandez

Inducing positive curvature (upward sori) in a shinogi-zukuri katana using OIL

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That's a beautiful sword. I would not have thought that possible in oil. If I had any Park 50 I would try it. Maybe I need to get some after all....

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That's really lovely.

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That's a beautiful blade there Jesus.

 

As far as why- there are a ton of possible variables here.

 

What we know:

1) Oil has to be around 180 degrees

2) Clay coating is essential.

 

Oil temp.

One of the most obvious variables of course is viscosity.

At room temp (70F) water has a viscosity of 1 cts (centistokes)

At 100F .68cts

At 200F .28cts

 

Parks 50 at 100F is around 6 cts (45 SUS or SSU). (Canola oil at 70F is 40cts)

I could find no info on Parks viscosity at 180F since they recommend using it at 120F or below.

But if water viscosity can change 35% in a 30 degree increase and 72% in a 130 degree increase I have to believe that Parks viscosity can change dramatically at increased temps as well.

So my best guess is that at 180 degrees you are approaching the viscosity of water.

 

No big surprise. Intuitively we probably all figured that was the case. This is just some numbers to put to it.

A place to start :)

 

 

 

Regarding the clay.

I am not sure of all the sequences of events in clay quenching in oil vs water but as I understand it, it is the rate of change in volume of the edge in relation to cooling speed. So it would seem that this lends further credence to the closer you get to the viscosity of water the more it acts like a water quench ( A faster quench).

 

Again as I understand it, the main danger with water in not the speed of cooling but the uneven cooling caused by a vapor jacket. In this case if the oil can replicate the speed but not the uneveness then we have a win. I think it is not the positive or negative sori we are looking for but the activity in the hamon. I think this blade shows this very well.

Another advantage would be to fine tune the process where there is no change in sori. That way we can shape the blade the way we want it pre-quench. Naw! It couldn't be that easy. Shape it the way we want AND reduce the risk of cracking? Where's the fun in that. :lol:

 

Please feel free to add to or correct any of the above. I feel that there are some gaps or errors in the logic.

Edited by Danocon

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That's some great data, Dan. Thanks.

I completely agree with you on the viscosity issue. I think that everyone I spoke with think that this is the main mechanism for this phenomenon.

I think there is still a missing link given that drastic effect that clay has on the process. I always thought that the sori changes in water or oil where due to a timing issue between physical differential contraction of the metal due to cooling and volumetric transformation due to change in crystalline structure.

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Preliminary pictures of the second sword. This is a sanmai construction 1050 for the core and folded cable steel for the sides.

The hamon is a simple suguha (straight). It worked on one side. The other side had a spot with some funky activity.

 

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Been waiting on this! Aside for the funky its a great piece, as expected.

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Very cool, Jesus. I'll try this as soon as I get a blade ready, which will be in a few decades at the rate I'm going :wacko:

 

I don't remember where, but I thought I read somewhere online that heating the Parks 50 above 120 would hasten it's degredation, not that the benefit of positive curvature isn't a a huge one, but at the dollar cost of Parks 50, could be a factor. If it doesn't ruin the oil, then I'm all over it.

 

Any problem with flare up in any of your quenching at those oil temps. I've never had a problem with Parks 50 and flare up, but remember a friend commenting when he tried P50 for the first time, it flared six feet. We determined that it was the red hot tong syndrome, but with room temp P50. Could get real exciting with hot oil.

 

Nice work and thanks for all your sharing.

 

Dan

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Thanks for the link to this and for doing this in the first place.

 

I have a couple questions though..

 

In the past I have cracked a couple blades in water quench but only when the whole blade had been heated to austenitic in my "Don Fogg" style HT forge.

When I have done a more controlled heating by moving the blade in an open ended forge careful to not get the spine non-magnetic, I have success.

 

Based on an earlier PM with you Jesus, are these experiments fully heated blades?

 

Also, that first hamon in W2 looks to me like a typical Parks50 hamon, a very literal line. Yes it's beautiful but it's not quite as "wispy" or ghostly as my experiences with water.

I find this interesting.

 

Further, have you assessed the difference in hardness from the regular Parks50 temperatures to the super heated version? The literature, as mention, recommends Parks50 in the 50-120 degree F range so I wondered that with such a change in the effects as noted in the sori, is there a corresponding hardness variance?

 

Very interesting stuff here... Definitely going to have to try this.. (except for my fear or ruining the Parks 50. It's stupid expensive getting it shipped up here)

 

Thanks!!!!

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Hi Dan, how have you been?

I am not sure about the degradation of the oil but definitively no flare up. Just a very violent boiling reaction.

 

Stuart,

 

These blades were fully austenized. And I agree with you the hamon does not look like a water quench. It not as wispy but interestingly enough it follows the clay perfectly in the third of the blade closest to the edge. I don't have any means to measure hardness accurately.

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Sir, those are beautiful!

 

i missed this post at the time so i a coming into this a bit late. i was wondering if you had any indication of the hardness of the blades? the formation of the hamon shows that the steel did harden. the question is are they as hard as if they were quenched in water?

 

I had not seen the last reply. appears you answered this already... if anyone has hardness testing kit this would be the next thing i would think would need to be investigated.

 

 

this is very interesting... i have a blade in 1080 that is in need of rough grinding before it is ready for heat treating. i was planning to go with water but i will try this method and let you know what happens.

Edited by taran

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These are the preliminary pictures of the hamon on the 3rd blade (W2 steel). The fourth blade will not get done for now until it finds someone who would like to own it.

When I finish putting together this blade I will post better pictures in a separate thread like I did with the other two.

 

So this will close this thread for now just hoping for others to try this and post their experiences. It's been almost a straight month of polishing every day and I need a break for a while (a break from polishing that is). I feel that the hamon obtained in this way is quite interesting, particularly for the batch of W2 steel that I am using. In the third or half of the blade closer to the edge the hamon follows the clay very closely. In the third or half above that the hamon becomes a version of what is called utsuri. The habuchi (white) is not as fluffy and wide as with water but in this blade there are some areas where it looks like the proper clay layout could widen that effect. Still the advantages of positive curve and no cracks can make up for the difference.

 

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I've been under the impression that Martensite is greater in volume than Pearlite. On a differentially hardened blade, the martinsetic edge pushes the tip up, because it is trying to "puff up" a bit more than the softer back.

 

If quenching in oil, no clay, on a blade-like cross-section, of course the tip will go down, as there is more mass along the top of a blade than the edge, forcing the geometry out.

 

Water's so fast, that the edge will swell before the rest, and by then most have chickened out and pull the blade out of water, so the tip goes up.

 

Oil, with clay, seems to preserve the expansion of edge steel, while disallowing spine steel to convert to martensite, explaining the phenomena.

 

 

 

 

That's all I can pull together from various ABS lectures on the subject, but it seems straightforward, and more about which part of the blade is being transformed to martensite than the quench medium per se... it is only the means to the ends.

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Does anyone _know_ if there is any consistent difference in martensite distribution in the blade cross section between upward and downward sori?

 

I don't suppose anyone is willing to chop a couple of swords in half to find out? :)

I have a feeling that if I spent the hours conducting such a test then I wouldn't be able to detect a difference.

 

I had a sword that went up at the tip and down towards the handle. It ended up in cleanly broken bits which would have been perfect to analyse if I hadn't been in the middle of redoing heat treat when the breaks occurred :(

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I don't know, Jack, but several years ago Don had one of his differentially hardened blades tested by a metallurgist and posted the resulting short paper here. There may be something in there that helps, it was a little over my head when it first came out. It's by R.K. Nichols, aka Quenchcrack, appropriately enough. :lol:

 

 

The Nichols report.pdf

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That is really interesting. Thanks!

A much better experiment and report than I would have done. If I do get around to doing such an experiment, then I will not put any clay on the blades - I can still expect up and down sori can't I?

Also, in the only video I have seen and from a description of the quench process from Don, a water quench starts with the tip bending down before moving back again. Do we have any evidence that upward sori can occur without being preceded by downward?

Maybe oil and water quenches start the same, tip down. Oil then results in the movements freezing at the tip down stage. Water (and now hot oil) allows the movement to continue and turn to upward curve before things are frozen?

 

It would also be interesting to find out residual stress distribution in a downward sori i.e. are there compressive stresses along the blade edge?

Have people had edge cracks in downward sori blades?

Edited by jhobson

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I would hope Mr. Cashen would be able to shed some light on this issue. Maybe someone who knows him better can ask him to wade in with an opinion...

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Well I finally got some blades ready for some hot quench oil experiments. The blades ran the gamut. three traditional tantos, one large chefs knife, one smaller paring knife, two shinogi zukuri katana(one 26" and a huge one that is close to 32") and to make things interesting a yari(spear) blade that's had two previous unsuccessful quench attempts . Steels ranged from 1065, Aldos low manganese 1075, forge welded 1075/W2 at 1200 layers, and W2. I tried to recreate the conditions that Jesus has outlined in this thread and from conversations we've had on this subject. In the end I was not able to get any positive curvature in any of the blades, actually as the blade length increased I saw negative(downward) curve. And I also never saw any violent boiling of the quench oil as I was quenching.

 

So here are some variables that might come into play.

 

This is the same Parks 50 I had down at the Fire & Brimstone Hammerin when I first tried this. Maybe it's old, contaminated, ETC.

 

I used Rutlands furnace cement as my refractory which I have to say based on preliminary hamon results might be my new favorite clay.

 

I don't know where this all leads us but I would love to get some ideas as to why I can't recreate Jesus's results.

 

Don't get me wrong, nothing cracked, the tantos cames out with what look like some really nice hamons, and the problem child/third times the charm yari came out of the quench almost dead straight! So all and all a very good night heat treating.

 

Matt

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Well I finally got some blades ready for some hot quench oil experiments. The blades ran the gamut. three traditional tantos, one large chefs knife, one smaller paring knife, two shinogi zukuri katana(one 26" and a huge one that is close to 32") and to make things interesting a yari(spear) blade that's had two previous unsuccessful quench attempts . Steels ranged from 1065, Aldos low manganese 1075, forge welded 1075/W2 at 1200 layers, and W2. I tried to recreate the conditions that Jesus has outlined in this thread and from conversations we've had on this subject. In the end I was not able to get any positive curvature in any of the blades, actually as the blade length increased I saw negative(downward) curve. And I also never saw any violent boiling of the quench oil as I was quenching.

 

So here are some variables that might come into play.

 

This is the same Parks 50 I had down at the Fire & Brimstone Hammerin when I first tried this. Maybe it's old, contaminated, ETC.

 

I used Rutlands furnace cement as my refractory which I have to say based on preliminary hamon results might be my new favorite clay.

 

I don't know where this all leads us but I would love to get some ideas as to why I can't recreate Jesus's results.

 

Don't get me wrong, nothing cracked, the tantos cames out with what look like some really nice hamons, and the problem child/third times the charm yari came out of the quench almost dead straight! So all and all a very good night heat treating.

 

Matt

 

Matt,

I do not know what the cement is you are using .....and I do not know the details of how the study was done as evaluated by Mr. Nichols. Looking at the study, it seems the back of the water cooled blade is softer than the back of the oil cooled blade. I found that interesting.

Why not concentrate on the back of the blade and make sure it is not cooling too soon ( and that it does get up to full heat ) ....maybe by....mixing an organic material (fine powder) with the cement and / or maybe sealing the applied cement after an initial heating with for example a heat resistant paint.

Jan

 

 

Good luck

Jan

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Hey, Matt. Thanks for giving this a go. I don't know where the differences are but I can tell you that the boiling type reaction is a characteristic of the process. I recently quenched another blade using this method. It was wakizashi-length and the steel was home-made smelted from ore. It curved up. More so than I expected it would but this steel is, shall we say, "softer". May be it is not your oil that is contaminated, may be is mine. Whatever it is, I am going to fiercely protect this oil tank from any one.

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There are a great many variables in the equation for doing yake-ire, to produce a hard edge and soft back. TINY differences in the amount of manganese will have great influence, and the presence of chrome, nickel, vanadium, silicon, copper, and several other things can radically change the beahviour of the steel in hardening, especially when you are walking the razors edge between hardening and not, trying to produce a complicated hamon. Ideally, you would have no manganese at all, and use water, and it would be simple. Tough to do that without making the steel from scratch.

 

I believe it is the order of the decomposition of the austenite that determines the curvature of the sword. If the edge cools sufficiently fast to get past Ms, and make a significant percentage of martensite, BEFORE the pearlite starts to form in the spine, the curvature is point up, positive, classical sori. If on the other hand the pearlite forms first, then the curvature is point down. The difference here can sometimes be measured in fractions of a second, and it is over in less than ten seconds in any case. Everything has an influence. The temperature that you use to austenitize, the grain size, the alloy content, the quench temperature, and the quanch medium are simply the short list. There is also heat history, carbide size and distribution, what kind and how much clay, and how you applied it. How much air was worked into the clay as bubbles? How did you dry it, or did you not.

 

The unfortunate truth here is that you must find a way that works for you, with the stuff you have or can get. And practice is the only path to success in this endeavor. I suggest keeping notes. It helps as you get older, so you don't have to repeat the failed experiments as many times, then slap yourself in the head and say, "oh yeah, now I remember why I don't do it that way". Enough variable to keep one wondering for a lifetime, perhaps. :)

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I have a w2 waki blade ready for HT as we speak and I want to try this, but i don't have a quench tank built yet. My blade is 26" .30 thick Aldos W2 all stock reduction, never allowed to get hot to the touch.

 

Mr Hernandez, what size is your quench tank and how much parks did it take to fill it? I could probably go 10 gal ($) but not much more...

 

Is there a minimum size trough i should shoot for? Any input appreciated..

 

 

Brent

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Thank you for your input, Howard. "Too many variables". Saying that reminds of the movie "Sneakers". "Too many secrets". It's a great movie. We should add agitation of the quench media. Matt, you should toss in your thoughts too.

 

I only used a 5 gallon bucket of oil and please, drop the Mr.

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Thank you for the info, 5 gallons is very do-able. Its my first sword and I was going to chance it in water but after all this work i don't wanna risk it...Now Im wishing I would have forged some sori in it then did the grinding.

 

 

Brent

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