laminated Hitachi White and Blue Steel Heat Treat Process

[HSC ///]

To help with the recent HT sticky, I’m offering what I have learned and use myself relative to laminated Hitachi steel. I’'ll outline and detail the process as taught to me over about 9 days with Murray Carter over 2 separate visits. Carter’s book on bladesmithing is also a reference available.
I believe the steel is designed and meant to be forged although I know many are using it as stock removal blank. So however you use it, I'’ll just focus on the HT specifically on this post. I also won’t get into what kind of forge or oven you are using, although I do use a twin burner propane forge, a charcoal forge is most ideal.

So a summary first –

Harden - Blue 1436 °F

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White 1436 °F - 1526 °F

Quench - White → water, lukewarm
Blue → water (desirable), lukewarm, or oil

Temper – 356 °F
63-64 RC

Grind wet below 302 °F
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Once the blade is profiled, holes drilled and ready to harden, prior to hardening , thinly coat blade with clay slurry

I use a clay slurry that I made myself based on some online research and my experience of what Carter uses. This prevents the vapor barrier from forming when the hot steel in inserted into the quench water. The mixture is mostly ball clay, iron filings, charcoal powder, iron oxide. Most items were purchased from Aardvark Clay and Supplies in Santa Ana. The clay tends to get thicker (and settles to the bottom) as the water evaporates, so just add some water and stir everytime you use it. The clay slurry is very thin and it’s a light, almost see-thru coating). Again the purpose is to help the blade cool faster.

Dip the blade into the clay slurry, use the mixture to clean the blade by rubbing the blade back and forth in your fingers. Only the blade needs to be coated, not the tang.
With tongs, place the wet coated blade into the forge to dry and harden the clay coating. The clay will change color as it dries up. This only takes 20 seconds or so. The clay dried should be thin enough to “see through”. Set the blade on a rack or brick.

Water quench, bring your water up to approx. lukewarm temperature. Use the same stagnant water over and over. You can fire some rebar or scrap steel red hot in the forge and dunk it in the water to raise the temp to about 100 deg F.

You can now heat the blade in the forge to temp for the quench. In a forge heat the thickest part of the blade first and let the heat “bleed” into the tip(s). When the blade gets to temperature (you can check by magnet or color). The goal is to have the blade evenly heated. You do not want to overheat.
Once the blade is at temp and evenly distributed heat, dunk the blade straight into the water, no agitation or movement required. Count to about 5 seconds and you can take the blade out, it will be steaming and hot. I usually place the blade on a rack at this point.

The tempering is done almost immediately after pulling out of the quench. I use the aid of a Tempilstik marker. The tempering is very fast and there is no hold or soak at the temperature. The blade is brought up to temperature (checked with Tempilstik) and removed and allowed to air cool. The time to come up to temperature is only a few seconds, so you have to pay close attention.
Depending on the type of blade profile and thickness, bending and twisting of the steel during quench is common and predictable in that it will happen. It is accepted that the blade will require straightening. I straighten the blade with a brass or copper hammer on a wood stump or wood block using light taps. There is generally no danger of cracking or breaking the laminated steel.

I grind wet by dousing the belt with water, it’s messy but necessary for this steel.

 

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pic examples

clay application -

prior to quench

post quench

 

[Stacy E. Apelt - Bladesmith]

Thanks. I'll add this to the stickys.

Just a note that the auto-tempering in a short time is a Japanese method. It produces very hard edges. Hitachi steels produce such fine grain that this type edge works. Most other folks use a longer oven temper.

 

[HSC ///]

Thanks. I'll add this to the stick.

Just a note that the auto-tempering in a short time is a Japanese method. It produces very hard edges. Hitachi steels produce such fine grain that this type edge works. Most other folks use a longer oven temper.

as Stacy mentioned, very hard edges.
here are two coupons of blue steel, not laminated, processed as per the process I wrote above.

 

[samuraistuart]

I was reading Murray's book concerning tempering. Interesting he advocates for very short tempering times, as you pointed out Harbeer. A hold for a few minutes is all that is required, which is a bit surprising. But these are fine kitchen tools made with relatively simple carbon steels, after all, and don't need the extensive tempering for the work they're likely to encounter. He does a few things I've always been told is a no no...namely cold forging (thermal cycling seems to be the better route) and vermiculite cooling of such a high carbon steel (carbides in grain boundaries, not desirable). But again, these knives are likely to be treated well in the kitchen environment, not the camp trail batoning thru logs.

Here are the temps Murray says he is using for given steels (Bladesmithing with Murray Carter):
White steel: Quench at 790C / 1454°F Temper 180C / 356°F
Blue steel: Quench at 810C / 1490°F Temper 200C / 392°F
Blue Super: Quench at 810C / 1490°F Temper 205C / 401°F

I've been using those temps myself with great results, tempering 2 cycles, one hour each (White 2, Blue 2)

 

[HSC ///]

I was reading Murray's book concerning tempering. Interesting he advocates for very short tempering times, as you pointed out Harbeer. A hold for a few minutes is all that is required, which is a bit surprising. But these are fine kitchen tools made with relatively simple carbon steels, after all, and don't need the extensive tempering for the work they're likely to encounter. He does a few things I've always been told is a no no...namely cold forging (thermal cycling seems to be the better route) and vermiculite cooling of such a high carbon steel (carbides in grain boundaries, not desirable). But again, these knives are likely to be treated well in the kitchen environment, not the camp trail batoning thru logs.

Here are the temps Murray says he is using for given steels (Bladesmithing with Murray Carter):
White steel: Quench at 790C / 1454°F Temper 180C / 356°F
Blue steel: Quench at 810C / 1490°F Temper 200C / 392°F
Blue Super: Quench at 810C / 1490°F Temper 205C / 401°F

I've been using those temps myself with great results, tempering 2 cycles, one hour each (White 2, Blue 2)

Actually the hold is much less than a few minutes, it's more like less than 10 seconds to reach 350-400 deg F
I know cold forging is frowned upon but it's suitable for laminated steel and I've cold forged every laminated blade I've made.
Carter uses rice ash, I use vermiculite which is a substitute because I don't have rich ash.

have a look at this at 2:05 - not severe batoning but I think you can do more with the edge than you think you can
also my understanding is Carter will doing some destructive testing of his FS1 collab model this weekend so stay tuned for this

https://www.instagram.com/p/BHA9VIWhRSA/?taken-by=cartercutlery&hl=en

- [video=youtube;MFe0ylD_sjE]https://www.youtube.com/watch?v=MFe0ylD_sjE[/video]

regards

 

[samuraistuart]

Luong has opened my eyes to the fact that hard steels (64+) can do more than I thought they were capable of!

 

[Greenberg Woods]

When you say auto tempering, you mean getting the spirit e of the knife to about the temper temp and then just pulling it out and letting it air cool, correct?

 

[HSC ///]

Yes. I use a tempilstik to check. That's what the black grease mark is.


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[Tenebr0s]

I think it's important to note here that Mr. Carter is doing a traditional Japanese heat treatment on his blades, but that is not representative of ALL makers here in Japan. I know makers who do everything by eye in a pine charcoal forge, but I also know makers who heat treat in PID-controlled molten lead baths or electric kilns. Many makers quench their steel in water, but still plenty use fast oil.

I have seen nothing that suggests the Hitachi steels (which I love and use in my knives) are special in requiring wet grinding. All steels would probably benefit from wet grinding; or at least, it certainly helps prevent problems.

Hitachi steels are very pure and consistent. I believe this means they can stand up to some harsher heat treatment processes. But just because they can, I think the jury is out on whether they SHOULD. That's just my $.02, as someone who makes knives over here.

 

[HSC ///]

I think it's important to note here that Mr. Carter is doing a traditional Japanese heat treatment on his blades, but that is not representative of ALL makers here in Japan. I know makers who do everything by eye in a pine charcoal forge, but I also know makers who heat treat in PID-controlled molten lead baths or electric kilns. Many makers quench their steel in water, but still plenty use fast oil.

I have seen nothing that suggests the Hitachi steels (which I love and use in my knives) are special in requiring wet grinding. All steels would probably benefit from wet grinding; or at least, it certainly helps prevent problems.

Hitachi steels are very pure and consistent. I believe this means they can stand up to some harsher heat treatment processes. But just because they can, I think the jury is out on whether they SHOULD. That's just my $.02, as someone who makes knives over here.

Thank you for the additional insight on the various methods used.

It's true that Murray works hard to honor and maintain traditional Japanese bladesmithing, with some modern adjustments. He is almost rigid in his application and does not deviate.

Agreed on the wet grinding, I see a few new makers of 2x72 grinders and I tell then - how about wet grinding? It's so much more productive and beneficial.

On your last statement, how long have Hitachi blade steels been around, and wouldn't you agree that tens of thousands of blades have been made using harsher heat treatment methods? That this process has been proven over time to make an excellent blade?

thanks again for a knowledgeable contribution.

 

[Tenebr0s]

HSC, that's certainly true: these methods have been used for a long time, and, as you say, they have produced excellent blades. Japan's cutlery industry would not be so renowned if it was putting out inferior knives. Still, it does not necessarily mean that these methods are the BEST possible way to heat treat this steel. All the Hitachi steels (with the exception of White #3) require soak times at precise temperatures. This is no easy feat if you're doing it by eye in a charcoal forge. To the credit of the Japanese makers' dedication and skill, they pull it off. One of my teachers here in Kyoto does an excellent job with these steels; however, even he admits that there will be disparity within a batch of blades he produces. Of the blades that pass muster, there will still be some that perform better than others. This is only to be expected when you're doing things by eye.

I tend to trust metallurgy when it comes to heat treatment, but also accept that most users might never know the difference between a precision heat treated blade and one heat treated by eye by a skillful maker. It would require a lot of testing to show the differences.

On a personal note, I know that it took my teacher here 15 years to get good at heat treating in this way. He could afford to do so; he was an employee of his family knife business, which didn't need to start selling his own knives until they were good enough. At 32, I don't want to wait until I'm almost 50 to be able to make a decent knife, so I use a kiln. And my teacher is happy with the results I get.

 

[HSC ///]

Can you elaborate on the soak times process used by your teacher? And in comparison your own method?

Thanks
Harbeer


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[Tenebr0s]

For white steel, for example, it would be a soak time of about 5 minutes (or longer) at 760-800 C. My teacher would do 5 minutes by eye in his forge. I do 10 minutes soak in my kiln.

 

[Willie71]

I did some experimenting with blue #2 this weekend. I soaked at 1475 for 10 min, and quenched in brine. With a 375f temper, I was still Rc64 to Rc65. I had to go up to 410 to get Rc63. I checked my tester to see if it was out, but I was spot on with the test blocks. Brine gave me an extra Rc1.5 compared to fast oil. I will note the tang cracked off in the second temper trying to correct a warp. There is risk involved. I'll end up with a 240mm knife instead of a 280mm knife now, but that's ok.

 

[HSC ///]

adding a recent HT test of some laminated white steel,
using the same HT procedure above with auto temper to 350 F

it's not easy to check the hardness of a thin core, I got lucky

 

[J. Doyle]

What is the chemical make up of these steels? Are they forgeable and with typical hot temperatures? And where can they be purchased?

Thanks for the info guys.

 

[Willie71]

What is the chemical make up of these steels? Are they forgeable and with typical hot temperatures? And where can they be purchased?

Thanks for the info guys.

https://www.dictum.com/en/materials/steel/steel

Simple steels, but very pure.

Hitachi white #2 is 1.1 - 1.2 %, Si 0.1 - 0.2 %, P <0.02 5%, S <0.004 %)

Hitachi blue #2 is C = 1.1 - 1.2%, Si = 0.1 - 0.2%, Mn = 0.2 - 0.3%, Cr = 0.2 - 0.5%, W = 1.0 - 1.5%, P <0.025%, S <0.004%)


That's right, the white has no manganese and hamons like crazy.

 

[HSC ///]

and a 1 min video of bringing a blade to temp, the quench in water, hold for several seconds and the the auto temper at the end to 350 f with templistik. If anyone cares, background music is "Faded by Zhu. "

https://vimeo.com/176866371


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