Is this knife forged? semi-forged? water quenched? oil quenched?

I received another Sakai Takayuki knife today. It is a blue 2 carbon steel gyuto 18cm with bolster (heat treated). In Japanese, chef knife made from blue steel is considered for professionals, white steel is for business, and others are for home cooking. So I got my first Pro knife, yay!

Is this knife forged? semi-forged? It has a bolster, so it must be forged, right? But the blade and the tong look like stamped.

Its label says it was heat treated. May I ask can you oil quenched blue steel? It has hardness of 60-62, so it must be water quenched, right?

Calm down, assume less, and don't trust marketing.

Blue: pro, white: business?
(Heat-treated) bolster?
Forged vs semi-forged vs stamped?

None of these things is accurate or meaningful.

The problem with running with presumptions is that deconstructing your understanding of knives is harder than building an accurate knowledge base from scratch.

Nice 👍

Your questions are probably best answered by the manufacturer. If I where to guess; it's maybe roll forged and stamped. Most likely oil quenched, as blue2 doesn't need a super aggressive quench to reach full hardness.

Thanks mate for your great input! But that bolster is kinda big, do you think they have such a big steel blank for roll-forge?

I suspect the bolster was forged, then cut, like Wusthof?

Hey, I have the 210 of that! How's the F&F around the handle? Mine has lines on the side of the blade that scream out that it was made on a CNC-type machine (lots of faint, parallel, perfectly-even circular marks going the entire length of the blade).

Also, how well do you find it to cut?

Edit: Now, with the coffee kicking in more, "milled" is the word I was looking for.

aichmophobia said:

Thanks mate for your great input! But that bolster is kinda big, do you think they have such a big steel blank for roll-forge?

I suspect the bolster was forged, then cut, like Wusthof?

Click to expand...

Usually the bolsters are pinned and soldered on and simply well blended to look like they are one piece (integral). Quite a lot of folks are convinced by it.

There are other techniques to make a big bolster by welding a thicker stock to a thinner stock and grinding it out, but I doubt it was done in this case. True integral forging is unlikely.

The blade is a monosteel if I recall, and I'd be willing to bet the bolsters are stainless.

As far as forging goes...it is likely cut from sheet and ground to shape. That does not make an inferior blade.

Virtually all non-junk blades are heat treated (at least hardened and tempered). You can easily achieve high hardness with blue2 in oil quenches (there are different kinds, some faster and some slower), and it is very practical from a production standpoint due to less warpage and failure.

Tig welded rather than soldered seems to be the norm. I'm guessing that's the case here. Almost certainly not forged.

aichmophobia said:

In Japanese, chef knife made from blue steel is considered for professionals, white steel is for business, and others are for home cooking.

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Where in the hell did you hear/read this? Also, love to hear them explain the difference in professional and business use

Only important question is, do you like the way it cuts?

BTW, nice knife:knife:

XooMG said:

Calm down, assume less, and don't trust marketing.
The problem with running with presumptions is that deconstructing your understanding of knives is harder than building an accurate knowledge base from scratch.

Click to expand...

Xoomg speaks truth...

Dan P. said:

Tig welded rather than soldered seems to be the norm. I'm guessing that's the case here. Almost certainly not forged.

Click to expand...

Makes sense, if it's not simply mechanical. I haven't ever taken one apart and don't have any to look at, so it was a guess.

or like that :

[video=youtube;4pWNx4wreP4]https://www.youtube.com/watch?v=4pWNx4wreP4[/video]

aichmophobia said:

...I suspect the bolster was forged, then cut, like Wusthof?

Click to expand...

Wustie has the stamping business pretty well down. My take is the Wustie bolster is "squished" into place. Describing any part of the process as forging is a bit of a reach. Would not be surprised if other mass produced blades did the same.

[video=youtube;DSZRx4eXM60]https://www.youtube.com/watch?v=DSZRx4eXM60[/video]

chinacats said:

Xoomg speaks truth...

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And the truth shall set you free.


But first it will piss you off:cool2:

Thanks for the video Dave!

Now that I know what I'm missing I'm off to buy a set of Wusthofs! :helicop:

I thought Blue steel was for Smurfs

daveb said:

[video=youtube;DSZRx4eXM60]https://www.youtube.com/watch?v=DSZRx4eXM60[/video]

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Oh man, they absolutely butcher the definitions of "tempered" and "annealed" in this video.
"Tempered at 1000 °Celsius (1850 °F)"!!! :bigeek:
Its gonna be hard to blow the temper on that knife by, say, accidentally overheating the edge above 1000 °C on a grinder. :laugh:

Thank you guys, I learned a lot from your replies. I think my Blue 2 knife might be roll forged by machine from blank, then stamp cut into blade, then bolster soldered by machine or by hand, then heat treated and quenched by oil. That explaines why the blade has lots of machine pressed strip marks, also the hardness is only 60 to 62. Because water quenching blue steel is extremely difficult, for this price, must be oil quenched.

Also, in Japan, Blue is indeed considered for professionals, everyone knows that. Forgive my poor English above.

Because water quenching blue steel is extremely difficult, for this price, must be oil quenched.

Click to expand...

this is not the price who decide how to quench steel, in water or in oïl, or in air ...it's the steel composition.
quench in oïl a shiro 1#A, is a mistake. and quench in water a super blue, it is useless.

Could there be confusion between oil/water normal and differential quenching? Or maybe even steel that stays white (stainless) vs that which becomes blue (carbon)?

From here on, assuming we mean blue paper (aogami) vs white paper (shirogami) steel.

....

If that is really monosteel and not differentially quenched (if it was, you'll have paid at least $500), 60-62HRC is hard even for blue steel. Usually, blue (paper) steel is associated with 61-66HRC knives, but using awase (two/three layer) construction. I'd be crazy enough to want to try a 66HRC AS (super blue) non-diff mono, but this a) isn't made and b) would have to be shipped packaged like glassware.

....

The knife types usually most associated with professional and enthusiast use would be the old-school japanese types (funayuki,yanagiba,usuba,deba), of which the vast majority of "proper" ones seems to be made of white steel.

Many steels can be quenched in water/brine or oil.

Dan P. said:

Many steels can be quenched in water/brine or oil.

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yes , but here we talk about blue or with paper.
with paper in oïl is not a realy good choice IMHO.

in fact, we can quench in water some steel who usualy quench in oïl, but the good question is : what is the point ?

or shiro 1, with a speed oïl like V35 ... but it's not realy sexy ...

You can quench both blue and white in oil. What, if anything, you sacrifice in speed you make up for in stability. I don't know if the Japanese use brine or straight water, but presuming they don't use cold water, warm water (as opposed to brine) can be a rather slow quench depending on temperature, same as oil.
Where there is the option of oil and water I suppose the maker would use what makes best sense to them?

oïl ( except some spécial oïl like V35 & co. )for shiro ( frome Hitachi ) dosen't work at al

but, whatever. i never use bluesteel. so i can't speak .

From James trip report to Sukenari, I believe they use old water/brine for at least some of their knives. Using old instead of new water, I imagine would slow down the quench due to other particles in there?

Dan P. said:

You can quench both blue and white in oil. What, if anything, you sacrifice in speed you make up for in stability. I don't know if the Japanese use brine or straight water, but presuming they don't use cold water, warm water (as opposed to brine) can be a rather slow quench depending on temperature, same as oil.
Where there is the option of oil and water I suppose the maker would use what makes best sense to them?

Click to expand...

pkjames said:

Fig 11: A deferentially heat treated honyaki knife, the water in the tank below is over 10 years old, apparently the age of water reduce the chance of failure during water quenching process the honyaki knife.

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Water can be pretty harsh. I think the traditional Japanese way of helping the blade survive a water quench is to coat the entire thing in clay. Even the edge that becomes martensite gets a thin layer.
Then theres also heating up the water and using old water as mentioned above.

If you want a good idea of how rough a water quench can be on a blade, watch this short clip where you can see the blade curving one way and another under the stress (the sori). It all happens in about 5 seconds.

[video=youtube;HOTKVLZlM8Q]https://www.youtube.com/watch?v=HOTKVLZlM8Q[/video]

mikedtran said:

From James trip report to Sukenari, I believe they use old water/brine for at least some of their knives. Using old instead of new water, I imagine would slow down the quench due to other particles in there?

Click to expand...

Could be the old water is "killed", meaning devoid of oxygen??
I'm not sure if that would make a difference or not, but surely the water cannot all be ten years old as it does evaporate, etc.
It's also true that there may be limited reason to change the water if it is used everyday, except to top it up!
Hocus-pocus may also be at play here.

Does anybody know if the Japanese use brine, rather than plain water?

Dan P. said:

Could be the old water is "killed", meaning devoid of oxygen??
I'm not sure if that would make a difference or not, but surely the water cannot all be ten years old as it does evaporate, etc.
It's also true that there may be limited reason to change the water if it is used everyday, except to top it up!
Hocus-pocus may also be at play here.

Does anybody know if the Japanese use brine, rather than plain water?

Click to expand...

Intressting Point of view! this may be the case, extremely reduced bubbling (don`T know if this is the right word, i am no native english speaker...) So called dead water....

To use brine as hardeneing medium is quite usefull because the boiling point is at about 108 Celcius..... and the oxigen flow is reduced. Not as save as a good oil with about 80-140 Celcius but much better then cold fresh water....

This is for sure something to experiment with..

Greets Sebastian.

Sharpchef said:

Intressting Point of view! this may be the case, extremely reduced bubbling (don`T know if this is the right word, i am no native english speaker...) So called dead water....

To use brine as hardeneing medium is quite usefull because the boiling point is at about 108 Celcius..... and the oxigen flow is reduced. Not as save as a good oil with about 80-140 Celcius but much better then cold fresh water....

This is for sure something to experiment with..

Greets Sebastian.

Click to expand...

Not as safe a quench as a good oil for the knife, but much safer for the human organism!
I have also read the distilled water is preferred as well, as being chemically inert (apart from the H2O & NaCl chemicals, obviously!) and devoid of particulates. Rain water the same, but perhaps this was more true in the old days when the rain wasn't full of acid and soot .

Makes one wonder how heavy syrup would fare?

LifeByA1000Cuts said:

Makes one wonder how heavy syrup would fare?

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Sounds delicious.

I have no idea about hardening really, the reason I thought about syrup was "watery liquid that can still go significantly above 100°C before evaporating" ... wonder what effect the copious amount of carbon available would have though....

Well, I have heard of adding sugar to flux when pattern welding, to prevent decarb. Total waste of time, BTW.
Anyway, just for the record I don't believe syrup would not work. It's too viscous and would also, I expect, form an insulating jacket of carbon/burnt syrup.