explain "laminated blade" to me

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martin j

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May 16, 2001
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I understand how laminate outside layers of stainless can " insulate" a carbon steel core layer from corrosion. But some references say laminate blade is also tougher, how is this so? If you have a brittle core, how does softer outside layers make the much harder core more resistent to shock or flexing stress ?
Is there other benifits to laminated blades I don't know????? Please explain!
Thank you
Martin
 
From what little I know,
I think the answer is very simple.
because the brittle is thinner, it is able to flex much better than if it was thick.
 
Basically the benefits of laminated blades are what you mentioned, stainless over a carbon core for rust protection, and soft steel over a hard core for durability. In addition to giving the hard core some felxibility the softer outer steel also makes sharpening easier. In sharpening you only need to remove the softer outer steel.

I am sure the exact way a laminated steel allows a hard core to not break when impacted or flexed is very complicated. But basically the softer outer layers flex easily, yet keep the hard core from breaking. I would presume that it is acutually similiar in function to a differential HT.

Check out the latest issue of TK, there is an interesting article in it about laminated steels.
 
Knife steel breaks when it is stretched beyond its limits in some localized spot. You seldom clamp a knife at both ends and stretch it in a tensile test machine. You generally break a knife be applying a bending force. When you bend the knife the surface that is on the backside of your bend is stretched. A hard steel does not stretch much plastically to releave local stress concentrations. In a practical sense this makes it subject to breaking easier at places with microscopic cracks, crystal boundaries, and even hard spots. A blade with a hard surface is a brittle blade.

When you laminate a blade you take the hardest steel and put it in the center of the blade where the bending stress is low. When you encase it in a softer steel, the softer steel also flows plastically to even out local stresses on the surface of the hard core. Mixture of a hard material in a softer surrounding medium is also how fiber glass works. So the hard steel is really protected by the softer outer layer as well as being nestled in a more protected area.
 
Often hard materials do not break because they are flexed beyond its flexibility limit, but because they receive a shock that ripples through the material. In hard materials a shock is dampened very little and transmitted very well (essentially it rings like a bell), which results in local stress points. In flexible or soft materials a shock is dampened and quickly dies off. The soft material surrounding the hard core functions essentially as a dampener dampening the amplitude of the shock and stopping the ring. Its the same as when you hold a glass at the rim lightly with your finger tips and tap (toast, ring) the glass.
 
Two basic reasons to laminate. The first is to make the steel that holds the cutting edge thinner for both lower cost and easier maintenance. The second is to make the knife tougher by lowering the average hardness of the blade by using soft steel on the exterior. Jeff Clark described that reasonably well above. The Japanese have made an art form of it. The Japanese make the best kitchen cutlery on the planet and the availability of laminated blades is one of the several reasons.

There really are two types of lamination in Japanese cutlery manufacture. The original one is called "kasumi." This process forge welds a piece of hard carbon steel to a piece of soft steel or iron to acheive the benefits listed above. It is a two ply lamination and is used on single bevel knives with the hard lamination facing whatever is being cut.

The other is called "warikomi" and is a three ply lamination. The soft steel is folded around the hard core and then forge welded to it. It is the kind of lamination the Japanese put on double bevel knives.

There really isn't any downside to the laminated blades. They work really well. The upside mentioned above is real. Too bad we don't make laminated blades in this country. It produces a terrific product.
 
OK i think I understand, thank you for informative replies! I thought it was like putting a sheet of glass between two pieces of rubber, I see how this analogy is incorrect .

So Japanese and Swedish style lamination- they are similar? I have seen inexpensive swedish laminates, however Japanese laminated knives seem expensive, this is not correct? The cost saved by useing cheaper outer layers, I would guess this is off set by the cost of forge welding??

Thank you
Martin
 
Sorry, I don't know anything about Swedish lamination. I haven't studied it nor have I seen any of the knives.

I'm not sure whether you are referring to Japanese kitchen cutlery or sporting knives when you talk about the high cost of the laminated blades. I'll assume sporting knives. They are expensive partly because the U.S. and European "manufacturers" who use these blades sometimes choose exotic steels for the cores - things like exotic ZDP-189 or even something as common as VG-10 as an example. That would be a costly. But truthfully, the major part of the cost of Japanese laminated blades is the making of the laminated steel itself regardless of the "ingredients."

I have no idea how the Swedes do it or how they do it less expensively. Perhaps someone that know more about that than I do will chime in.
 
The scandinavians have been making laminated blades for hundreds of years .The reasons ? Cost -a central high perfomance , high cost steel with lower cost outer layers makes a lower cost blade.Axes here were made with low carbon steel folded over and welded to a high carbon cutting edge.Some smiths still do it today.Sharpening - with the scandinavian grind you grind the whole edge, you don't make a secondary edge, so the softer outside makes it easier to grind. You can get laminated blades of carbon steel/carbon steel or carbon steel/stainless steel or stainless/stainless steel. I don't see the point of stainless steel outside with carbon core, the edge will rust . Since you now can get fine stainless core stells stick with stainless/ stainless steel. Laminated blades are also more flexible.
 
Trond makes nice laminated blades.

Here's a knife I made from one of his blades:

scandiblade.jpg


Mike
 
Check out Fallkniven's laminated blades, and their testing regime. The strength and edge durability they achieve is excellent.

As mentioned above, full convex grind knives are much easier to sharpen when the outer layers are a softer/more flexible stainless steel.
 
Scandinavian laminated blades (Helle, Brusletto, Frost of Sweden...) usually have thick core - thicker then sides, Japanese usially makes thiner core.

Laminated blades cons - it may just bend without breackage, but you may unbend it back (it is true for thin blades). Well it better to be this way if you are outdoor somwhere in the middle of Scandinavian or even Russian winter. Also softer sides are easy to scratch, but also easy to polish back.

As I understand Falkniven blades are actuall Japanese not Swedish.

As I understand lamination was standart practice everywhere in Europe for hundreds years in the past. Good steel was very expensive. I know in Russia at least hundred years ago for example they fill iron pipe with pices of broken files and hammered it to perfect laminated blade.

Examples:

Authentic Higonokami knives - brass handle laminated with Aogami steel in core (also known as Blue steel 1.3% C 1-1.5% W), black handle Shirogami in core (also known as Wight steel 1.3% C) - Aogami one $16! at LeeWalley.

Higonokami-08.jpg


Norvegian Helle Fjellkniven knife - stainless laminated steel

helle-fjellknivrn-01.JPG


Thanks, Vassili.
 
In Japan, as I understand, laminated blades is standart for knives - I bought this one in and it was not even mentioned anywhere - I just found it out when I look close. And this is regular knife for abou $20 for school student to sharpen pencils etc:

ICCut-V2-03.jpg


Thanks, Vassili.
 
Japanese blades tend to have harder cores which makes the edge a bit vulnerable to chipping. The scandinavian blades have a core that is of a more ordinary hardness around 60 RC and a rather soft exterior. The scandinavian blades are not likely to chip or break. The only problem is that they may bend plastically more easily than other knives of comparable dimensions.
 
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