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Quenching factors that lead to Warping


John Smith

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Ok here is my problem, I can make Japanese style blades like no budies business. But Midevil type blade I have broken every single one. I forged a Bastard Sword blade that was 29" long and 1 3/8" wide with a taper of 1/4" at the ricasso to 3/16" just before the tip, I normalized the blade twice " I most likely should have done it two or maybe three more times "

 

Ok I put ruthlands high heat mortar mix on the center of the blade to alow the center to cool even slower. I let this set for a week, today I test fired my heat treat forge to making sure it was sound and sealed. I then shut it down and started to heat the oil for the quench.

 

I placed the blade in the heat treat forge and fired her up, alowing the steel to come to temp slowly. Once the blade was non magnetic I quenched it, the blade sounded fine going in and smoked alot and I slowly moved it around. Then I felt the blade shuddered and I heard the clay poping off the blade. I pulled the blade from the oil and I had a warped blade, it warped 1/4 of the way down from the point. Now here are the factors that I feel may have contributed.

 

1 not enough normalizations

2 My pyrometer is out of commission, so I had to eye ball the color and temp

3 I heated the oil to about 140 f

 

If any one can see any where else that I may have gone wrong please say so.

 

Oh the steel was 5160 it was 3/8" thick and 1" wide and 25" long when I started It may have been a newer leaf spring that I was using who knows.

John W Smith
www.smith-forge.org

Fire and wind come from the sky, from the gods of the sky. But Crom is your god, Crom and he lives in the earth. Once, giants lived in the Earth, Conan. And in the darkness of chaos, they fooled Crom, and they took from him the enigma of steel. Crom was angered. And the Earth shook. Fire and wind struck down these giants, and they threw their bodies into the waters, but in their rage, the gods forgot the secret of steel and left it on the battlefield. We who found it are just men. Not gods. Not giants. Just men. The secret of steel has always carried with it a mystery. You must learn its riddle, Conan. You must learn its discipline. For no one - no one in this world can you trust. Not men, not women, not beasts.

[Points to sword]

This you can trust

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leave off the clay. while you can clay harden 5160 (just about), and you can clay harden a 25" double edged blade, i can't really imagine that you can do both. if you are making a european sword, then you don't want 'hard' edges - how would you expect it to be used? if you are convinced you need the aesthetics of a hamon on a long, tapered, double edged blade, use 1080 in oil, or 1095 if you have Park's 50. if you really feel you need a differential hardness on a 5160 double edged sword blade, run your h-t forge at 1400f until up to temp and soaked, then turn it up full and quench just when the thinner edges get past critical. differential hardening on 5160 is a whole different ball game than doing it on a shallow hardening steel, and this will give you a quench line, but not a hamon.

 

edit: just re-read your post, and a few other things spring to mind.

 

1. never move a double edged blade in the quenchant. yes, movement will both agitate the quench and expose the steel to unheated quenchant, but seeing as you have about 9 secs to beat the pearlite nose of 5160, why'd you want to speed up the quench - all you get from moving it back and forth is an uneven quench speed, which will warp your blade.

 

2. similarly, clay will only work as a heat sink, in terms of stopping parts of the blade from coming up to temp - this is how you use clay on 5160 - it will never inhibit the rate of cooling enough to prevent martensite forming, but it will affect the rate of martensite formation, which will, again, warp your blade.

 

3. normalising - if you don't have a working pyrometer, then you're never going to get better results than 3x post mag. to do 5160 right, i'd guess youd have to soak really hot (1850+) to put the chromium into solution, and then have steadily descending heats down to about 1412f to shrink the grain size, and even then i'd imagine that the distribution of chromium would precipitate martensite transformation deeper than you'd want.

 

if you're using a spring steel, give it a spring temper, and you'll get what you're looking for on this kind of blade.

Edited by jake cleland

Jake Cleland - Skye Knives

www.knifemaker.co.uk

"We can't solve problems by using the same kind of thinking we used when we created them."

"Everything should be made as simple as possible, but not simpler."

"Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."

 

Albert Einstein

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Jake

 

Actually I was not going for differntial heat treating I just wanted to have a soft center and hard edges. I am not even sure you can get a hamon on 5160. I honestly thought I was helping the process by adding the clay, for added insulation.

 

I am sure I was past critical as well, but with out my pryrometer working I was guessing.

John W Smith
www.smith-forge.org

Fire and wind come from the sky, from the gods of the sky. But Crom is your god, Crom and he lives in the earth. Once, giants lived in the Earth, Conan. And in the darkness of chaos, they fooled Crom, and they took from him the enigma of steel. Crom was angered. And the Earth shook. Fire and wind struck down these giants, and they threw their bodies into the waters, but in their rage, the gods forgot the secret of steel and left it on the battlefield. We who found it are just men. Not gods. Not giants. Just men. The secret of steel has always carried with it a mystery. You must learn its riddle, Conan. You must learn its discipline. For no one - no one in this world can you trust. Not men, not women, not beasts.

[Points to sword]

This you can trust

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John,

 

hard edges and a soft centre is differential heat treating. my point is that it can't really be done on 5160 purely by insulation, because the steel is so deep hardening, and so all the clay adds is a different rate of martensite precipitation, which leads to warping.

Jake Cleland - Skye Knives

www.knifemaker.co.uk

"We can't solve problems by using the same kind of thinking we used when we created them."

"Everything should be made as simple as possible, but not simpler."

"Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."

 

Albert Einstein

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I see your point, I just figured 5160 could not be Diff HT, but I was wrong so just do not add clay next time, what about heating the oil? And forgive me I know these are beginner questions but like I said I do not cross into long double edged blades, let alone using 5160.

John W Smith
www.smith-forge.org

Fire and wind come from the sky, from the gods of the sky. But Crom is your god, Crom and he lives in the earth. Once, giants lived in the Earth, Conan. And in the darkness of chaos, they fooled Crom, and they took from him the enigma of steel. Crom was angered. And the Earth shook. Fire and wind struck down these giants, and they threw their bodies into the waters, but in their rage, the gods forgot the secret of steel and left it on the battlefield. We who found it are just men. Not gods. Not giants. Just men. The secret of steel has always carried with it a mystery. You must learn its riddle, Conan. You must learn its discipline. For no one - no one in this world can you trust. Not men, not women, not beasts.

[Points to sword]

This you can trust

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My own experience with 5160 is that, when edge quenching, you get about 2x more hardened steel than your immersion would suggest. That is, if you immerse 1/4" of the edge, you get about 1/2" or better of hard steel. My thinking is that a 5160 double edge blade of 1 3/8ths full quenched as you describe is going to harden nearly to the core, no matter what. I did do a 5160 dagger that was hard edge and soft spine by spinning it in the forge (trying to heat just the edges) and watching the colors. The edges heated faster than the core, but it was a balancing act. I also used a "psycho" quench, stabbing the piece into the oil and out again, very fast. That would be hard to do on a long blade.

 

I agree with the cautions about moving the blade in the quench. If you are going to move it, do it ONLY in line with the edge, not against the flats of the blade, and then only as little as you can.

 

Geoff

"The worst day smithing is better than the best day working for someone else."

 

I said that.

 

If a thing is worth doing, it is worth doing badly.

- - -G. K. Chesterton

 

So, just for the record: the fact that it does work still should not be taken as definitive proof that you are not crazy.

 

Grant Sarver

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Hey John,

 

I use 5160 for many of my long double edged blades, european style.

 

This is the routine I use:

 

Start forging pretty hot, in the solid/light yellow range.

FInal forging a bit less heat, but I do not worry much about grain growth. I rather spend less time in heat and move the steel efficiently. To my experience it creates trouble to forge in lower ranges as you get tensions that can be resisting your idea of straightness through out the process. Shape and straighten in a god solid heat and take care of grain size during normalization.

 

I forge thickness and width close to shape, but leave more material for grinding in the bevels. This is to be sure I come to fresh steel without risk of decarb. Before the normalization I descale the blade. I normally give the blade a first rough grind before I do the normalization just to check I have calculated dimensions correctly and to check for straightness and symmetry. After this I place the touch mark into the blade (I stamp this hot).

Using a drum forge for most of my heat treating I put ATP-64 as anti scale on the blade. That way I minimize the decarb and scale build up.

 

I normalize three times: 870 C, 850 C and 835 C. Cool to dark hanging in a wide iron tube between heats.

 

Now I do all rough grinding to shape and go over all shapes in the blade with draw filing. I make sure the bevels are symmetrical, edges mirrored in thickness and that no side has more or less bulge than any other. In short: the blade must be as even and symmetrical in shape as you can possible make it. If not you will invite cork screwing, warping, s-curving and bending. It takes very little difference in the edge thickness and volumes on each side of the spine, to induce sabering or curving. Tolerances need to be within a couple of tens of millimeters.

I leave edges about 1.5 millimeters. This allows for grinding afterwards and helps create a good final edge geometry (nice lean apple seed section).

 

If you do not look to symmetry you will just spend more time straightening afterwards. I rather file before heat treat than straighten after....

 

Some times I do stress relieve heating after excessive grinding and filing. You will induce a lot of stress in the surface as you grind and file. The blade will come out straighter if you let it soak for some 600 deg C over 40 - 60 minutes.

 

Then it is time for final heat treat.

I coat with ATP-64 and let it sit over night.

When furnace is in temperature, 835 deg C, I introduce the blade and let it come to temp. It takes about 15-20 minutes in my drum forge. I let it soak at temp for 15 minutes. I want to be sure I get full transformation to austenite. If not it will also invite warping.

 

I quench into a standing tube of canola oil. It is about 60 - 80 deg C. I have a die grinder fitted with an excentric steel disc fastened to the quench tube, that I start just before it is time to quench the blade. This makes the bath vibrate, which helps to break up vapor jacket.

Blade is removed from oil when it has stilled. Blade is still smoking a bit and too hot to touch without a good glove.

Martensite has not fully set yet, so there is time to do some initial straightening. It is normal to have some slight warping every time. A long lazy bend (not as a saber) is the most common. This is very ease to counter. I have two blocks of wood on a bench and press the blade with a third block, working against the bend in the blade. Go easy or you will easily introduce stubborn kinks. A light hand does the trick. When the blade does not react to straightening any more it is too cool and needs to go into the tempering bath. I use a salt bath for tempering. Final straightening is done over the tempering process. 45 minutes @ 220 deg C times three.

 

This gives me a hardness that is about 57-58 HRC. It is a good balance between hardness and toughness with this steel if you give it a fine structure. No need to worry about a tough core and hard edges. Edge holding will not be as good as a carbon steel hardened and tempered to a higher hardness, but you have a blade that is like a *very* hard leaf spring that will take an incredible amount of bashing and still hold a decent enough edge, for a sword.

 

Please show your results! I am eager to see what you make with a european-style blade!

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Well Peter aside from a few of your techiques, I pretty much do the same thing for all my long blades. I also do not have a large tempering tank, perhaps I need to get one started. So like I said Japanese blade I am good to go, because the steps needed to reach the final results are pretty simple. But it seems that a double edged long sword need more care due to the types of steel being used.

 

Well I know what I need to do and that is make more things for the shop, my favorite time creating tools.

John W Smith
www.smith-forge.org

Fire and wind come from the sky, from the gods of the sky. But Crom is your god, Crom and he lives in the earth. Once, giants lived in the Earth, Conan. And in the darkness of chaos, they fooled Crom, and they took from him the enigma of steel. Crom was angered. And the Earth shook. Fire and wind struck down these giants, and they threw their bodies into the waters, but in their rage, the gods forgot the secret of steel and left it on the battlefield. We who found it are just men. Not gods. Not giants. Just men. The secret of steel has always carried with it a mystery. You must learn its riddle, Conan. You must learn its discipline. For no one - no one in this world can you trust. Not men, not women, not beasts.

[Points to sword]

This you can trust

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John, I'm not in the same league as most of you guys but I noticed that no one suggested thermal cycling. I started doing it a couple years ago and haven't had so much as a wavy edge since. I do it for three cycles in between the last three forging heats prior to normalizing.

 

Like so: Heat to forging heat, forge. Heat to critcal, quench. Repeat x2. Normalize. If you misjudge and need another heat or two, just make sure you heat and quench as the last thing before you normalize. I've been getting tiny grain size and no warpage at all, even with relatively thin edges.

 

I just started working with 5160 myself and after asking around I've had several suggestions to try a slow quench oil. I've got some McMaster slow quench and I'll be trying that soon, but I can't comment on it yet.

 

-Todd

www.toddblades.com

 

"Geometry says how sharp, steel says how long." - Roman Landes, Ashokan 2009

 

"People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf."

 

- George Orwell

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John,

 

I use almost exclusivly 5160, As jake says 5160 is deep hardening, it can get a hamon, but it is very tricky to do so. If it makes you feel any better i have tried clay coating mine for fun and Ive bent or cracked every single one that was 5160 and those were smaller blades round 3-12 in blades.

 

heres what I do that works well for me and gives me excellent results every HT ( not that I dont still worry mind you )

 

I forge halfway to shape, normalize once, forge to final shape I want, normalize 3 - 4 times stepping down temp each time, then I heat it once more and leave it in the turned off forge till cool. next day I profile grind and refine geometry etc... next fire I adjust anything I may have missed; crooked tang, slightly bowed blade and the like.. .after that 2 more normalizings and then full anneal in vermiculite.

 

I have never broken or warped a 5160 blade using this method so I assume it works even though it is a bit overkill.

 

Oh I also quench in 150 deg F veggie oil, I do a interupted edge quench almost all the time. then after 7 sec.. full quench.. sometimes a double if Im daring followed by a diff temper.

 

Or as Lon Humphrey told me.. he forges his 5160 at a much lower temp, Im assuming aus forging then when he hardens he only gets the edge to critical by exposing it edge up to the burner. it will result in what you want as the soft/ hard combo, Ive seen his blades done this way bend 180 deg 10- 12 times and not break.

 

hope this helps.

 

Pat B

Gnáthamh na hoibre an t-eólas

(Knowledge comes through practice)

 

Iron is full of impurities that weaken it; through the forging fire, it becomes steel and is transformed into a razor-sharp sword. Human beings develop in the same fashion. - Morihei Ueshiba

 

my site: http://lfcforgeworks.webs.com/

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John, you ARE quenching vertically, point down, right? If you try to edge-quench a double-edged blade it'll warp every time. That includes a full quench into a horizontal tank. I'm sure you know that, just making sure everyone else does too.

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Alan howdy, and yes it is a vertical quench tank my oil mix is 15 gallans of hydraulic fluid, which has a flash point around 500 if I remember correctly, and the remaining 10 gallans are deisel fuel.

 

I think everyone is right the clay was the factor that caused the warp and eventual breakage of the blade. I will attempt another long sword soon, I just need to get a tempering tank built, so I have to find another propane tank to cut up. I have the setup to heat the tank from my old fry baby french frier it will do 400 f so that should be enough to heat the tank for tempering.

 

I thank everyone for their input I see the errors that I have made and you guys pretty much agreed on the cause.

 

And yes I am trying to for different blades as there is and SCA chapter in this area and I wish to appeal to them as far as bladesmithing.

John W Smith
www.smith-forge.org

Fire and wind come from the sky, from the gods of the sky. But Crom is your god, Crom and he lives in the earth. Once, giants lived in the Earth, Conan. And in the darkness of chaos, they fooled Crom, and they took from him the enigma of steel. Crom was angered. And the Earth shook. Fire and wind struck down these giants, and they threw their bodies into the waters, but in their rage, the gods forgot the secret of steel and left it on the battlefield. We who found it are just men. Not gods. Not giants. Just men. The secret of steel has always carried with it a mystery. You must learn its riddle, Conan. You must learn its discipline. For no one - no one in this world can you trust. Not men, not women, not beasts.

[Points to sword]

This you can trust

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Alan on a side note, I used to work for the Kentucky Tenn clay company and I used to do some drilling in the Johnson city area of Tenn, I sure wish I could get a bag of their clay, so I can make so heat treat clay. As they sold it by the back from the plant where I worked in Hickory Ky

John W Smith
www.smith-forge.org

Fire and wind come from the sky, from the gods of the sky. But Crom is your god, Crom and he lives in the earth. Once, giants lived in the Earth, Conan. And in the darkness of chaos, they fooled Crom, and they took from him the enigma of steel. Crom was angered. And the Earth shook. Fire and wind struck down these giants, and they threw their bodies into the waters, but in their rage, the gods forgot the secret of steel and left it on the battlefield. We who found it are just men. Not gods. Not giants. Just men. The secret of steel has always carried with it a mystery. You must learn its riddle, Conan. You must learn its discipline. For no one - no one in this world can you trust. Not men, not women, not beasts.

[Points to sword]

This you can trust

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Alan on a side note, I used to work for the Kentucky Tenn clay company and I used to do some drilling in the Johnson city area of Tenn, I sure wish I could get a bag of their clay, so I can make so heat treat clay. As they sold it by the back from the plant where I worked in Hickory Ky

 

Small world!

 

If I run across any I'll let you know, but I haven't seen it before. Most of the clay around here goes into brick manufacturing via General Shale, but I have a potter friend who's into local clays and glaze materials, so I'll ask him if he's seen any.

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  • 2 months later...

Small world!

 

If I run across any I'll let you know, but I haven't seen it before. Most of the clay around here goes into brick manufacturing via General Shale, but I have a potter friend who's into local clays and glaze materials, so I'll ask him if he's seen any.

 

 

Multiple causes of distortion and warping - all related to non-uniform quenching.

Causes of Distortion-steel.pdf

Distortion Fishbone.pdf

D. Scott MacKenzie, PhD

Heat Treating (Aluminum and Steel)

Quenching (Water, Polymer, Oil, Salt and Mar-Tempering)

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