How Fallkniven's laminated steel breaks

[Twindog]

This failure was intentional, not the fault of the knife. This was a cheap S1 that I broke to see how failure initiates in the blade. No great lessons here. Just FYI for people interested in this sort of thing.

What happens is the knife delaminates with very little deformation prior to the break. This steel acted very brittle. I used a heavy vice and just hand pressure to break off a large chunk of the tip -- the first inch of the blade. Then I used a hammer for the thickest portion of the blade.

None of this would affect the knife when used as intended. This is not a slam on Fallkniven. I had no way to measure the force exerted. Both the hard VG 10 core and the softer 420-alloy cladding crack and break.

 

[Alberta Ed]

Interesting. The very nice laminated Fallkniven blades should hold an edge longer, but I stand by my F1 in good old solid VG-10.

 

[Twindog]

Interesting. The very nice laminated Fallkniven blades should hold an edge longer, but I stand by my F1 in good old solid VG-10.

I think I now feel the same way. I'd rather have a solid blade of VG 10.

It looks to me as though the inner VG 10 core breaks first, which triggers one side of the laminated steel to break, which triggers the other side of the laminated blade to break, but farther down the blade.

I thought that the softer 420 cladding would hold up better, but it is quite thin.

I also thought that the blade would bend more before breaking, but it breaks after minimal bending.

 

[jdk1]

That is surprising. I don't know anything about laminated steel, but figured the layers were essentially welded, or otherwise bonded much better than this. This lamination doesn't look like like it offers much. I guess that's why y'all are saying you would rather have a solid VG10 blade. Thanks for sharing this and maybe you can turn the stump into a really cool box cutter!

 

[Twindog]

That is surprising. I don't know anything about laminated steel, but figured the layers were essentially welded, or otherwise bonded much better than this. This lamination doesn't look like like it offers much. I guess that's why y'all are saying you would rather have a solid VG10 blade. Thanks for sharing this and maybe you can turn the stump into a really cool box cutter!

I thought that way, too -- that the layers would be more permanently welded together.

But I also couldn't see how the hard, more brittle core could stand up to the blade flexing pretty hard. And it doesn't.

What did surprise me is how the softer cladding broke so soon -- before the blade flexed that much. I thought it would just bend and only the inner core would break. But the soft 420 cladding broke and cracked. You can see in the bottom photo a long crack running through the cladding.

The blade was strong enough to do anything you would normally ask a knife to do, and then some. But I'm now skeptical that lamination adds 20 percent toughness to the blade, as Fallkniven says.

 

[DocJD]

!

This failure was intentional, not the fault of the knife. This was a cheap S1 that I broke to see how failure initiates in the blade. No great lessons here. Just FYI for people interested in this sort of thing.

What happens is the knife delaminates with very little deformation prior to the break. This steel acted very brittle. I used a heavy vice and just hand pressure to break off a large chunk of the tip -- the first inch of the blade. Then I used a hammer for the thickest portion of the blade.

None of this would affect the knife when used as intended. This is not a slam on Fallkniven. I had no way to measure the force exerted. Both the hard VG 10 core and the softer 420-alloy cladding crack and break.

I'm wondering if this would apply to Cold Steel's "San Mai" ?

 

[JokersFaceLifter]

yeah.. i dropped my fallkniven knife on the tip into a block of wood and i guess there was a nail or staple in there somewhere and the tip broke off, i was shocked, it grounded an edge fairly easy though, ended up selling it, never again

 

[Twindog]

!


I'm wondering if this would apply to Cold Steel's "San Mai" ?

That's a good question. Lamination means three layers, usually -- as in the case of Fallkniven's VG 10 lamination -- the inner core is a hard VG 10 and the two outside layers are softer 420J2. I'm not sure how Cold Steel's San Mai is made.

Research out of the Division of Solid Mechanics at Lulea University of Technology in cooperation with Fallkniven, found that lamination makes the blades tougher. So in the graphs below, a single-steel F1 breaks at 91 Nm and the laminated blade breaks at 108 Nm.

So I'm not going to challenge that science, but what I saw is the laminated steel breaking fast, with considerable delamination and breaks that travel down the blade -- rather than clean breaks. To me, the layers are so thin they lose toughness, but Fallkniven's science says otherwise.

 

[Twindog]

yeah.. i dropped my fallkniven knife on the tip into a block of wood and i guess there was a nail or staple in there somewhere and the tip broke off, i was shocked, it grounded an edge fairly easy though, ended up selling it, never again

The tip of my Frej has 5 mm of exposed VG10 at the tip. So I'm guessing that the part that broke off your Fallkniven was the hard VG10 core. If you run a hard core and depend on the soft cladding to protect it, you'll expose your hardened tip to breaking. There's no lamination at the tip to protect it.

 

[JokersFaceLifter]

The tip of my Frej has 5 mm of exposed VG10 at the tip. So I'm guessing that the part that broke off your Fallkniven was the hard VG10 core. If you run a hard core and depend on the soft cladding to protect it, you'll expose your hardened tip to breaking. There's no lamination at the tip to protect it.

likely --- ive heard of chipping issues from fallknivens knife line for a while, never experienced it myself until then, there's a chick on YT who runs a channel, she uses and severely abuses fallknivens knives until they break and chip then give it a bad review cause they broke... i mean, probably shouldn't be using the tip to pry off barnacles from rocks but then again maybe its just me

 

[DocJD]

That's a good question. Lamination means three layers, usually -- as in the case of Fallkniven's VG 10 lamination -- the inner core is a hard VG 10 and the two outside layers are softer 420J2. I'm not sure how Cold Steel's San Mai is made.

Research out of the Division of Solid Mechanics at Lulea University of Technology in cooperation with Fallkniven, found that lamination makes the blades tougher. So in the graphs below, a single-steel F1 breaks at 91 Nm and the laminated blade breaks at 108 Nm.

So I'm not going to challenge that science, but what I saw is the laminated steel breaking fast, with considerable delamination and breaks that travel down the blade -- rather than clean breaks. To me, the layers are so thin they lose toughness, but Fallkniven's science says otherwise.

There is probably a big difference in real world results if there is any deficiency in the processing of these laminated steels .

If the layers aren't basically fused into one piece , the supposed benefits are lost , IMO .

I've owned Cold Steel San Mai knives for many years but never really pushed them with any hard use .

But reviews from others I trust seems to indicate that these knives performed well in actual hard use .

Too many variables here to be very scientific , I'm afraid .

 

[jdk1]

I keep coming back to this and I'm not sure why, except it bothers me. This is lamination that isn't! It's three sheets maybe glued or soldered together. Lamination, to me anyway, implies the three become one, or are fused. The layers in your example are connected, but rather weakly so. I'm really surprised and disappointed.

 

[jlauffer]

!


I'm wondering if this would apply to Cold Steel's "San Mai" ?

Not sure about the newer Taiwan San Mai, but my understanding is that the Japan San Mai III and the Fallkniven laminated steel are made in the same factory, so possibly. Only difference is that CS uses a VG-1 core (the Taiwan San Mai has a VG-10 core).

 

[DocJD]

I keep coming back to this and I'm not sure why, except it bothers me. This is lamination that isn't! It's three sheets maybe glued or soldered together. Lamination, to me anyway, implies the three become one, or are fused. The layers in your example are connected, but rather weakly so. I'm really surprised and disappointed.

Yeah , I don't think this is as it's supposed to be and advertised to be !

 

[DocJD]

Not sure about the newer Taiwan San Mai, but my understanding is that the Japan San Mai III and the Fallkniven laminated steel are made in the same factory, so possibly. Only difference is that CS uses a VG-1 core (the Taiwan San Mai has a VG-10 core).

Back when Cold Steel still had it's own customer forum , I read ( on the CS website) many testimonials on the great performance of San Mai .

That information resource is now gone forever, I'm afraid .

 

[Twindog]

I keep coming back to this and I'm not sure why, except it bothers me. This is lamination that isn't! It's three sheets maybe glued or soldered together. Lamination, to me anyway, implies the three become one, or are fused. The layers in your example are connected, but rather weakly so. I'm really surprised and disappointed.

Lamination is achieved by hot rolling (above 1,700 F) three layers of steel -- two soft outer layers and one hard inner core. I don't know the exact physical process, but at that temperature the plates are welded together.

The idea, of course, is to protect the hard inner core that forms the knife edge. But only the blade itself is protected. The edge and tip are exposed during the grinding of the edge. It seems a bit odd, in a way, because usually blades don't break. It's more common for the edge and tip to chip or crack.

Fallkniven runs their blades pretty thick anyway, so breaking the blade doesn't seem to be a problem that needs solving.

In any event, it would seem easier to switch to a tougher alloy, one that holds an edge as well or better than VG10 and is tougher than VG10. Lots of those alloys are available -- CPM 154, V4E, M4, M2, CruWear, Elmax, Vanax.

The problem I see with lamination is that when the blade is laterally stressed (bent), the three layers bend are forced to bend at different rates. That force is what causes the delamination.

I can't tell for sure, but it looks like the center core breaks first, causing the sides to break next. Anyway, the fusion between the layers is not as strong as I thought it would be.

 

[LUW]

100% noob question here, so be gentle.
From the little of what I understand, each kind of steel should have a specific heat treatment, right? If so, in the case of a laminated blade with different kinds of steel, wouldn't one or both steels be not ideally heat treated?

 

[Twindog]

100% noob question here, so be gentle.
From the little of what I understand, each kind of steel should have a specific heat treatment, right? If so, in the case of a laminated blade with different kinds of steel, wouldn't one or both steels be not ideally heat treated?

That's a good question. I presume that the two alloys are chosen so that they both perform well with the same heat treat. But it does seem that the heat treat would be at least slightly below optimal for one or both alloys in a laminated blade.

But I don't know.

My sense, however, is that the lamination itself is not a perfect way to increase blade toughness, because the three layers have to bend at different rates. That difference in the rate of bending stresses the lamination bond. And the more brittle core, which tolerates much less bending, can still break. When it does, the other two layers break in quick succession.

 

[LUW]

And you raise another point, the difference in brittleness between the two steels. Using a radical example, if I glue two sheets of rubber on a blade of glass, the rubber sheets will not prevent the glass from breaking if flexed. As I said, I'm a total noob, so maybe this doesn't have absolutely no relevance, but in my uneducated mind that's what I would expect.

I always thought that the objective of lamination was more to protect the harder steel core using a more stain-resistant steel on the outside. Kind of like using a good hard carbon steel for the edge and then "coating" the whole blade with some stainless steel just to avoid oxidation.

 

[Twindog]

And you raise another point, the difference in brittleness between the two steels. Using a radical example, if I glue two sheets of rubber on a blade of glass, the rubber sheets will not prevent the glass from breaking if flexed. As I said, I'm a total noob, so maybe this doesn't have absolutely no relevance, but in my uneducated mind that's what I would expect.

I always thought that the objective of lamination was more to protect the harder steel core using a more stain-resistant steel on the outside. Kind of like using a good hard carbon steel for the edge and then "coating" the whole blade with some stainless steel just to avoid oxidation.

Sometimes that's true. Fallkniven's hard core is VG 10, which is already stainless; so I don't think that's the issue with this company's laminated steel, at least when VG 10 is the core.

The lamination study funded by Fallkniven focuses on how lamination increases the toughness of the blade -- increasing the resistance to breaking by about 20 percent.

The experiment that I did wasn't scientific, but it did give me a sense of what's going on. It didn't take that much to break the blade. Most of my knives would not break this easily -- they'd bend first.

Below is cracking damage on the edge of a blade made from A8(mod). It failed while cutting small branches, which is actually a tough test, but one this steel should have passed easily.

That weakness meant my A8(mod) blade had no more value to me as an EDC. I have other EDC blades that stand up to chopping small branches. So I decided to test its strength/toughness in the vice, just like the Fallkniven S1.

With about the same force that broke the S1, this blade just bent.

A8(mod) is normally a very tough steel, but I suspect that the heat treat was bad, allowing the edge to crack. However, it was still much tougher than the laminated Fallkniven blade -- in that it bent rather than broke.