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A little discouraging... Your thoughts?


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So this is both my first attempt at a Japanese style blade and my first knife attempt in months. It's a stock removal because I didn't want to spend hours only to have what happened happen, only had about 3-4 hours into it. Not sure what I did wrong as I've forged a few out of the same 1095 with no issues. I heated to a nice even dull orange and checked it with a magnet, then quenched in hot water(out of the tap) for about 6 seconds pulled it out and put it back in and heard the pings...

 

Should I be quenching for a shorter amount of time or maybe with hotter water? I didn't normalize as I figured it wouldn't be needed with no forging, or maybe it did?

 

It looks like it would have had a great hamon and the sori came out exactly how I wanted.... :( Oh, and I burned my finger!

 

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Edited by Silent Matt
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Can't help you with the burnt finger other than cold water but I have found that for water quenching, the trick is differential heating. Very carefully control the heat so that it gets non-magnetic up into the clay transition point or slightly higher but not so much that the spine goes to non magnetic.

If you can pull that off then you should get success in a water quench. It might have something to do with not doing grain reduction but the last time I cracked a blade was due to heating the whole blade evenly.

I know that not everyone does what I'm doing but I got this advice from Bill Burke and haven't cracked a W2 blade since.. (now that I've jinxed myself.. :rolleyes: )

 

And it's likely that the tip got too hot. Did the clay pop off?

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Guest guest T

That kind of crack is due to uneven cooling in the spine and edge. My theory is that the edge cools quickly without shrinking as it turns into martsinite but the thicker spine does not cool as fast and shrinks as it cools trying to stretch the now hard edge. The most stressful part of cooling the blade is well after critical temp and if it cracks it usually does after it has cooled to black. This could be somewhat avoided by using a more deep hardening steel or claying the blade so that a smaller part gets hardened. You definetly need to normalize before quenching the steel grain size from the

manufacturer will be somewhere between fine sand and 100 grit from what I have seen. Dull orange seems hot for 1095 I don't know if you could use oil for it though I have had good success with using cold water and I heard the Japanese smiths used ice cold water from another post. Take what I say with a grain of salt but I would not post something I did not beleive and observe to be true.
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1095 is a water quench steel and I've been successful in the past with it. Maybe I went a little too hot, I'll try again with a normalized blade and less heat.

 

 

Stuart, I used furnace cement instead of mixing up some clay and yes it popped off. Oh, and on the burn, I've noticed if you don't use anything cold it normalizes(haha) faster.

 

I was so looking forward to making the mounts for it <_<

Edited by Silent Matt
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Man, I would be discouraged too. That is a great looking little blade, that fuller especially...perfectly clean and even.

 

 

1095 is a hyper- euctectoid steel that can be quenched in either water OR oil. When the thickness of the steel gets below 1/4'' or so, it is my understanding that oil will give a much more consistent (and positive) result.

 

Tre mentioned uneven cooling, and that feeds into the fact that a lot of smiths recommend mar-quenching 1095 to minimize distortion,cracking and residual stress . Just a thought.

 

That kind of crack is due to uneven cooling in the spine and edge. My theory is that the edge cools quickly without shrinking as it turns into martsinite but the thicker spine does not cool as fast and shrinks as it cools trying to stretch the now hard edge.

 

Tre, I'm not sure if I understand exactly where you are coming from on this... Steel expands when heated, and obversely shrinks when cooled. How can edge not undergo shrinking as it is being quenched ( cooled )? . Could you maybe expound on that? Are you simply referencing a timeline, of it not shrinking before turning to martensite?

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Did you use a milling bit for that fuller?

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I'm not sure about furnace cement but clay popping off can be a sign of getting the steel too hot (other than the blade not being clean before application.)

I suspect that's the problem.

Edited by SBranson
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That kind of crack is due to uneven cooling in the spine and edge. My theory is that the edge cools quickly without shrinking as it turns into martsinite but the thicker spine does not cool as fast and shrinks as it cools trying to stretch the now hard edge.

 

In making Japanese style blades and how "sori" or curvature is induced. Briefly, the edge cools quickly and the blade bends downward and forms martensite so when the spine cools more slowly it creates more densely packed pearlite and thus pulls the blade upwards. It's a lot of stress but if you can control the heat (among other variables) then it works.

 

http://www.fukuyama-u.ac.jp/gakubu/mecha/staff/inoue/cd/temperature/anim.htm

http://www.fukuyama-u.ac.jp/gakubu/mecha/staff/inoue/cd/martensite/anim.htm

http://www.fukuyama-u.ac.jp/gakubu/mecha/staff/inoue/cd/pearlite/anim.htm

http://www.fukuyama-u.ac.jp/gakubu/mecha/staff/inoue/cd/stress/anim.htm

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My money is on the not normalizing part. You don't know for sure what the structure or grain size of the steel was when you got it, other than "annealed."

 

That does hurt to look at.

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On previous blades of this material I forged the shape and primary bevel, and they all got normalized. I'm pretty sure that and maybe a hair too hot were the culprits. At least I learned something and it will be that much better when I do get it right. Time to go get some steel and try again.

 

Al, yes the fuller was milled in, I'd be crying if I spent the time on it by hand. I still need some lessons in patience and skill.

 

 

Thank you all for the pointers.

Edited by Silent Matt
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A blade that size would have been ok at 4 seconds in the water, by 6 seconds you were probably within a few hundred degrees of room temp. I'd recommend going into oil after the initial water quench, much slower cooling when the blade is going through the martensite conversion which means the stress build up isn't so sudden.

 

I'm not sure but the bo hi being put in before the quench may increase the rate of cracks. A paper showing the stress a japanese style blade goes through during quenching has been circling around for a few years and was recently posted on this forum. It shows a large amount of stress builds right around the boshi. Having a dramatic cross sectional change (the fuller) right where most of the stress is localized may cause more cracks. Of note, your big crack is almost exactly where that paper shows a large stress point is focused.

 

Beautiful blade however. Good luck on the next!

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Normalize at least 3 times in descending heats.

 

use hot tap water (it is less stressful than cold, not the other way around, but cold removes heat more effectively because it takes

longer to boil, but the smiths who were using cold weren't using modern steel, I bet.)

 

shoot for 1450F with a 2-3 min soak, if you can't control temps in your forge then work hard to keep the whole thing even and bring it up to tem very slowly.

 

leave it at least twice as thick as you would for a quench in Parks 50

 

Take it out of the water after 3 secs (I count almost to 4, but I am excited at this point, so I count too fast).

 

Put it into room temp canola or Parks or whatever oil you have in a big enough container and just leave it there for about 8 secs.

 

Remove from oil, knock off the clay, and straighten really fast by hand before the edge steel sets.

 

I always cut the fullers in before hardening, and I think that they may actually reduce some of the stress because there is less steel to pull against the edge when cooling.

 

Those are my suggestions. This regimen works really well for me. Just remember, thick! Way thick. Too thick. Thick like a nickel for the size blade you had, or more.

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I have actually seen 1095 technically described as water-quenching steel.

 

"Water quenching" in the industrial sense often indicates brine. When I was working with low-hardenable steel combinations involving 1095, I used fairly saturated brine at 120 degrees F with much better results that with oil or plain water. There's argument over whether or not brine quenches quicker or slower based on concentrations, but it's gentler either way, as the salt inhibits steam jackets. I'd certainly give that a try.

Edited by J.Arthur Loose
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Bo hi are carved -always- after the hardening process, maybe you have been punished by the kamis for that mistake ? A quick etch will probably reveal you were too hot. Working by hand make you way more focused when you are heating your blade for quenching. Spend more time, you'll be rewarded, I can tell. Fear of loosing working time may not enter the equation, as the goal is not really the result

Edited by igrec
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Nope- some folks say "15%" and some folks say "saturated," by which they mean heat it to 120F and put as much salt in as will dissolve. I think anywhere in between is safe.

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I've had 1095 that would only quench in brine. It might have quenched in something like Parks #50 but I didn't have the money to invest in it if I had known about fast quench oils. I would go with it not being normalized. It's just bad Ju-Ju not to do it.

 

Doug

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Mat,

Thanks for posting this experiment..lots of good advice..lots more experiments..I suspect the spine thickness had a lot to do with your cracks.

 

Stuart,

I have enjoyed the blades you have posted and value your knowledge and experience. Right now until I try a few more quenches ,I disagree ( I am assuming the clayed spine does need to get hot , to non magnetic...but must be relatively thin) . I have found the thin spine to wrinkle due to the edge expansion , at first I thought this was a defect but I think it is good. I have even thought of pre wrinkling the spine. In about a month I will be quenching quite a few blades and hope you will add the colorful graphs again and participate in the discussion.

 

Jan

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