San mai yes or no

[JoeBusic]

Just watched a destruction test of a Falkniven A1. It's a san mai blade. Of course it broke as it's a destruction test. How it broke is unneasy for me as I wanted to go in that direction. Layers detached at one part and on the clean break part, the break is layered.
Is that normal or is it a bad forge weld? I understand the differences in material with render some consequences but delayering with a break!? :/

 

[Joshua Fisher]

Most destructive tests are entirely unrealistic and if you fatigue anything enough it will break. If the cladding is non hardenable then it should help provide some strength if the knife is bent but I wouldn’t say it’s the main purpose of the cladding. There are various reasons for traditional San mai, first and foremost was to conserve hardenable material that was less abundant. (Not really an issue today in most cases) secondly it make straightening easier from the makers stand point, even after hardening you can use a brass or even steel hammer lightly to straighten. Now some of the by products of the process do increase overall strength in different ways, obviously it helps in the case of force being applied to the side of the knife such as bending, it also protects the core steel at the edge by minimizing chipping. Closer the cladding is to the edge the more it decreases the largest possible chip by supporting the material so in the traditional sense it allowed for extremely hard cutting edges with softer sides. (Traditional old Japanese kitchen knives verus old German knives, the first focus on a really hard edge and cladding to support it the second focused on softer steel overall to be tougher) today there’s also a benefit to stainless cladding to help with corrosion resistance with a carbon steel core, strength really isn’t the focus there but more that the cladding will be easier to maintain overall. Now modern San mai is often done for aesthetics using steel combinations that don’t really make sense other than for looks and to be “cool” 1084 paired with 15n20 cladding will perform no better than just 1084, same with using aebl for cladding it doesn’t make sense. Welds are always a point of potential failure but if the traditional San mai blade can be bent back and forth 200 times before the weld lets go and the monosteel blade breaks after the 2nd bend which one performed better in the “destruction” test. I hate seeing videos where someone shoots a knife or bashes it into a rock repeatedly and after an insane amount of stress the knife finally fails and people will jump in and say it was a bad knife, you should be able to shoot it atleast 10 times because that will ever happen in real life.

 

[Greenberg Woods]

I think that may just be the failure mode of san mai. No matter how good the welds are, a boundary layer is going to be weaker than continuous steel. The fact that it was a mixed break between a clean break and a delamination implies to me at least that the force required to delaminate and the force required to snap the blade were similar.

 

[JoeBusic]

Welds are always a point of potential failure

Helpful! Thanks

 

[JoeBusic]

No matter how good the welds are, a boundary layer is going to be weaker than continuous steel.

That's the point I was seeking. Thanks

 

[Joshua Fisher]

Helpful! Thanks

You should definitely quote the rest of that sentence, again while a weld can be a point of potential failure if not done correctly it can also prolong a potential failure if done properly using the right materials. It’s not a cut and dry topic, you can’t look at it as well if there’s a forge weld it’s an inferior blade over solid steel and vice versa.

 

[JoeBusic]

You should definitely quote the rest of that sentence, again while a weld can be a point of potential failure if not done correctly it can also prolong a potential failure if done properly using the right materials. It’s not a cut and dry topic, you can’t look at it as well if there’s a forge weld it’s an inferior blade over solid steel and vice versa.

I understand your point and the validity of it. Question was based on my belief that a good weld will act as monosteel. So it seems that a simple calculation of benefits is not valid. One should take into account delamination. That way if I do go that way I wouldn't be demoralized with a delam in a destructive test.

 

[Natlek]

I think that it delaminated in part 5 from hammering on spine while he cut that flat iron not from bending ?

 

[JoeBusic]

I think that it delaminated in part 5 from hammering on spine while he cut that flat iron not from bending ?

Hard to say. I watched other video with tests of san mai and all fail similarly. It seems that delam initiates a break in the outer layer. Quick thinking about it would suggest using less strong steel for outer layers so the weld isn't pulled that much.
Anyway I think going for a thicker stock is less troublesome. Though the idea is attractive still.

 

[DevinT]

It’s a sign of weakness

Hoss

 

[Natlek]

Hard to say. I watched other video with tests of san mai and all fail similarly. It seems that delam initiates a break in the outer layer. Quick thinking about it would suggest using less strong steel for outer layers so the weld isn't pulled that much.
Anyway I think going for a thicker stock is less troublesome. Though the idea is attractive still.

In half an hour, I'm going to visit my father, my workshop is there. In the name of science, I'll try to break this san mai and see what will happen It is 12519 core and 304 from sides

 

[Richard338]

In half an hour, I'm going to visit my father, my workshop is there. In the name of science, I'll try to break this san mai and see what will happen It is 12519 core and 304 from sides

I say the left side scale comes off first...

 

[Natlek]

I say the left side scale comes off first...

Scale are glued well they are a little bigger than thang , I shaped them separately from tang I didn't want to sand them after gluing to preserve the look.....but you're right, they will come off with a light hammer blow .And I will do that before I try to break steel...

 

[timos-]

It is interesting that historically the san mai was used to reserve the much more valuable core steel, but today san mai is generally more expensive than just buying mono steel.

 

[Greenberg Woods]

It is interesting that historically the san mai was used to reserve the much more valuable core steel, but today san mai is generally more expensive than just buying mono steel.

throughout most of history, high or even medium carbon steel has been very expensive and resource intensive to produce. Most edged implements from axes, chisels, and knives would have a tool bit welded in. Most swords, even those not classically associated with san mai like roman gladius and spatha swords, several viking broad swords and so on. The labor involved to make forge welds was just a lot smaller than the labor and charcoal involved in producing bloomery steel. So only what absolutely had to be steel was.

Now that massive foundries can produce high quality, consistent tool steel in bulk and hourly wages are much higher especially for skilled craftsmen, the labor of forge welding often has more value than a bar of 1095. To most ancient peoples a large piece of clean, high carbon steel would be an incredibly valuable commodity indeed.

 

[Greenberg Woods]

That's the point I was seeking. Thanks

Im not exactly sure what the question you're asking is.

Is a san mai blade going to have an increased risk of failure due to the potential of delamination?
Yes. The chance of a failed weld or other issues means san mai is inherently at a greater risk of catastrophic failure compared to a monosteel blade.

Is the failure point of a san mai blade always going to be a delamination failure?
No. Properly welded and treated it should preform fine and its reasonable to think a different mode of failure like a snap would happen first.

In the end i think it comes down to what risks are you willing to take?
How confident are you in your forge welds?
How much added value do you put on the aesthetic benefits of san mai?

 

[Natlek]

I say the left side scale comes off first...

Well Richard , i did not know that some *idiot* put hidden pins on that scale It took two blows with a hammer to loosen . So much epoxy , it holds on steel like a drunk against the fence

I forget how much tough is this steel , with hammer i was not able to break piece from belly so I used long pliers and that was not easy ...I break that piece just to see how hard is this steel after thermal cycling and hardening and how it will break . It break clean and i really like how small grain has this steel !almost invisible with eye

It explode just before i was able to shoot picture how much it bend before it snapped !
it pass far away from 90 degree, maybe it is more then 130 .......... pure 12519 on that hardness will break before 90 degree for sure ! I lost tang and tip somewhere behind bench and right now I m not dressed to move all that garbage to find it , i will sleep outside house tonight if I do that

it can be straightened

another try

that 304 don t behave like 304 anymore it behave more like bronze , it took some carbon from 12519?

this is not delamination , 12519 split in half there

Now , I break hundreds pieces of this 12519 steel I know how it behave .San mai worth every penny , that is what i think after this .To delaminate san mai you need to do crazy things that will never ever happen in real use .

 

[Natlek]

Im not exactly sure what the question you're asking is.

Is a san mai blade going to have an increased risk of failure due to the potential of delamination?
Yes. The chance of a failed weld or other issues means san mai is inherently at a greater risk of catastrophic failure compared to a monosteel blade.

Is the failure point of a san mai blade always going to be a delamination failure?
No. Properly welded and treated it should preform fine and its reasonable to think a different mode of failure like a snap would happen first.

In the end i think it comes down to what risks are you willing to take?
How confident are you in your forge welds?
How much added value do you put on the aesthetic benefits of san mai?

No !
failed weld is failed weld . Good welded san mai is not at greater risk of catastrophic failure compared to a monosteel blade , not even close . .Monosteel will fall long before san mai ..

 

[JoeBusic]

N Natlek Thanks man, appreciate the test.
I got what I needed. Thanks to all. Interesting subject. Will dive into it.

 

[Natlek]

N Natlek Thanks man, appreciate the test.
I got what I needed. Thanks to all. Interesting subject. Will dive into it.

This is angle when blade explode , literally explode . I hold that long tube with my left hand , with all my weight on it.Tube was shaking my hand as if I had a fever and it just explode , I did not apply more pressure . Mono steel don t break like that , you bend them and when it pass point it will just break .This san mai was 3.7mm thick on spine core is 1.5mm before welding .