What's so good about 3 layers?
Three layered steel knives have been around for a long long time. They are a progression or rather a offshoot from the traditional folded steel blades of Indian and Japanese history.
The layered steel knife today is commonly known as "San mai" from the Japanese (三枚) meaning 3 layers or sheets. As of writing there are no western entities mass producing such steel and the bulk of knife maker's materials are originating within Japan and China.
Whilst such constructions can be made by the custom knife maker, in reality to produce a homogeneous san mai construction requires exacting metallurgical technologies beyond the realm of the individual. As such, one company stands out as a leader in these technologies, they are Takefu Special Steel Co., Ltd.
I reached out to them asking if they could provide some further information, specifically regarding their welding process which enables the homogenous bonding of the two steel types for example: 420 J2 to VG-10. Unfortunately, despite having several emails going back and forth they did not take me seriously enough and hence I can not provide you with any such information. My only guess is that they may have figured I work closely with several knife manufactures and maybe they didn't like this? I made it clear that I was NOT asking for any information which could be construed as confidential of course. Anyway enough of that. I tried. They do of course have some extremely basic cartoon like images
but these serve no purpose other than to illustrate that they make laminated steel products, not how they make them.
Why 3 layers?
BTW before anyone says, hey Fällkniven are making san mai knives!
Yes, they are but they are not making the san mail steel. They import the steel from Japan.
Ok, so back to the question, "Why three layers"?
This question can be answered by asking what is the point of having three layers of steel? The inner layer is always the alloy which can be made the harder of two steel types, for example VG-10, whilst the outer layers can be of 420 J2, a softer grade stainless alloy but of superior corrosion resistance to VG-10. Such a combination can lead to a blade which possesses crazy toughness as once demonstrated on the internet by a you tuber who wore a hockey mask and routinely destroyed knives in his workshop. The only knife he never could break was Fällkniven san mai constructed blade. All other makes and models eventually snapped under his onslaught of crazy bending and bashing tests. Not only does such a blade exhibit crazy toughness but the steel doing the cutting only needs to be thin, just thin enough to be able to be sharpened easily. So there is also good economic reasons for such blades.
Where the technology comes into play is how both sets of alloys are seamlessly bonded to one another so that during great stress, such a bending moments, the two individual alloys do not part company along the "weld".
If it's so good then why aren't all knife manufacturers doing this? Well as I explained, not many have this technology, and it's probably cheaper not mass producing such blades, as for example, if one makes a knife out of just VG-10, then an equivalent knife from VG-10 and 420J2 has to be more expensive due to more steps involved. However, if one wants to own a knife from a 3 layer construction and benefit from such an indestructible design
then this will drive the market for such production to continue.
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