Laminated Steel

[Cait_Sith]

Wondering if anyone could provide more insight on laminated steels. Specifically the type of usage between the laminate that uses a hard core and is sandwiched in between soft outer layer versus that of a soft core and sandwiched between hard outer layer.

Any particular benefits or negatives on using one over the other?
And did one exist before the other?

 

[RX-79G]

The edge steel is always going to be hard, high carbon steel. So a typical laminate is going to be the first type. The point of this construction is that the knife could bend past the breaking point of hard steel and will just deform instead of cracking.

The only kind of laminate I can think of with soft steel on the inside is an old type of Japanese sword construction that has a hard edge that wraps up around a soft core. While someone could make an alternate argument, the primary reason for this type of construction is to stretch the relatively rare high carbon steel by filling the middle of the blade with the lower carbon stuff. But a blade that is completely hard on the outside isn't going to behave any differently than a solid hard steel blade. If bent too far, the hard outside steel will crack.

And, as you can see in the picture on the left, you can have an edge laminated to the back, rather than the sides.

 

[mete]

RX, you're thinking about japanese swords. For knives Fallkniven ,. Helle and some others make laminated blades including all stainless types . Right now I'm carrying a Fallkniven U2 which has their top of the line steel in the center .A very fine steel !! Laminating gives you the advantages of a great steel at the cutting edge at lower cost without being brittle etc. About the only problem ,and that is rare is delamination if the steel mill hasn't been doing it correctly.

 

[Rich S]

I have a few laminated Helle blades and they are wonderful. Cut like razors.
Rich

 

[RX-79G]

RX, you're thinking about japanese swords. For knives Fallkniven ,. Helle and some others make laminated blades including all stainless types . Right now I'm carrying a Fallkniven U2 which has their top of the line steel in the center .A very fine steel !! Laminating gives you the advantages of a great steel at the cutting edge at lower cost without being brittle etc. About the only problem ,and that is rare is delamination if the steel mill hasn't been doing it correctly.

No, I'm not.

The first part of my post was about typical laminates - like the Moras, Fallkniven, Cold Steel and other common laminates with hard cores.

The second two paragraphs were about the OPs unusual soft-on-the-inside question. Do you know of any modern blades with soft steel in the middle?

 

[Cait_Sith]

Thanks for expanding on the topic. I was thinking that the rarer type with a soft core had to be done for a certain reason as it didn't seem to provide anything better even over a mono-steel. It makes sense that perhaps during times when purity of steel was difficult to come by that the efficiency of saving it and just having it as an outside layer made a lot of sense.

 

[Jens Schuetz]

If the core is hard and the outside soft, wouldn't the core crack too if bent?

 

[me2]

If bent/flexed, stress decreases the closer you get to the center, so if the center is thin enough, it won't crack.

 

[bdmicarta]

If bent/flexed, stress decreases the closer you get to the center, so if the center is thin enough, it won't crack.

Yes, the outer surfaces will see the highest stress and will start to yield first. If you are using a softer steel, i.e. a less brittle steel, it can yield and deform without cracking. When the user sees that the blade has been bent they should take this as a sign to stop doing whatever they are doing. If you continue to bend the blade, the outer surfaces will continue to deform plastically. The inner core has not reached its yield or fracture point yet so it continues to bend and increase stress elastically. At some point it is possible that the core could reach its fracture point and crack. If the center is relatively thin it would take a lot of deformation for it to reach its fracture point.

 

[Jens Schuetz]

If bent/flexed, stress decreases the closer you get to the center, so if the center is thin enough, it won't crack.

Yes, the outer surfaces will see the highest stress and will start to yield first. If you are using a softer steel, i.e. a less brittle steel, it can yield and deform without cracking. When the user sees that the blade has been bent they should take this as a sign to stop doing whatever they are doing. If you continue to bend the blade, the outer surfaces will continue to deform plastically. The inner core has not reached its yield or fracture point yet so it continues to bend and increase stress elastically. At some point it is possible that the core could reach its fracture point and crack. If the center is relatively thin it would take a lot of deformation for it to reach its fracture point.

Thanks guys. That makes sense.
The thinner the core the less danger of cracking? The only challenge if the core is super thin could be to match it to the apex of the edge I guess.

 

[FortyTwoBlades]

From an Emerson & Stevens catalog page in my collection showing their lamination process for scythe blades.

High carbon edge steel for a hard edge, medium carbon for the spine (or "back" as it was called in scythe blades) for springiness, and low carbon cladding for toughness. You wouldn't believe some of the abuse I've seen laminated scythe blades take and not break. Most laminated scythe blades only had the hard high carbon "cast steel" core with high-grade iron cladding so if they bent they stayed that way until you hammer the bend out cold on an anvil. Despite some truly gnarly "rainbowed" blades from folks driving the tip full force into the dirt with a golf club swing (not recommended technique) I've only had a couple suffer cracking of the edge when I tapped them back out. Though I've seen plenty of plain old busted ones I can't even imagine how much abuse they must have put them through before they failed fatally.

 

[Bigfattyt]

One of the traditional reasons for using a soft core, was efficient use of limited resources.

The steel quality was not great. The smelting/refining process they were using produced higher quality high carbon steel that could be hardened to a higher level, and more lower carbon, softer steel and iron that was useful for building materials/filler.

It was common with many early tools. A high carbon/quality bit, welded into a lower quality softer iron body.

 

[Jens Schuetz]

One of the traditional reasons for using a soft core, was efficient use of limited resources.

The steel quality was not great. The smelting/refining process they were using produced higher quality high carbon steel that could be hardened to a higher level, and more lower carbon, softer steel and iron that was useful for building materials/filler.

It was common with many early tools. A high carbon/quality bit, welded into a lower quality softer iron body.

The cost of using the better steel throughout was basically higher than the wage of the blade smith doing the more complicated work?

 

[Forgedfixedblade]

I have seen where the Falkniven knives chip pretty easily against bone, seen a few hunters post up pics.

 

[Bo T]

The cost of using the better steel throughout was basically higher than the wage of the blade smith doing the more complicated work?

Exactly. Remember in the middle of the 18th century there were a lot (relative to today) of blacksmiths and after a few years of apprenticeship the majority knew how to forge weld.

 

[RX-79G]

I have seen where the Falkniven knives chip pretty easily against bone, seen a few hunters post up pics.

That's a problem of the edge steel which a laminated construction can't address.

Exactly. Remember in the middle of the 18th century there were a lot (relative to today) of blacksmiths and after a few years of apprenticeship the majority knew how to forge weld.

Everybody's labor had a cost, including the labor of whoever smelted the ore. Low carbon steel wasn't worth wasting, and a smith's time is "free" to him, but his materials had to be paid for in cash.

I've seen some amazingly complicated mechanical objects made in a blacksmith's forge when I took some classes. The kind of thing no one would even try to do anymore.


Even today, we still use cheaper steels where a slightly higher grade would be better. Most structural uses would be great to use stainless, but our cars still rust.

 

[PiercedBill]

My only experience with laminated knife blades is my Helle GT, and I really like it.
It was very sharp, even after having been the display model. A little work on the water stones and it's perfect..

 

[Bigfattyt]

The cost of using the better steel throughout was basically higher than the wage of the blade smith doing the more complicated work?

Well, it is a bit more complicated than that.

The people making weapons in ye-olden-times ranged from masters that made high end art pieces for kings and emperors to village blacksmiths.

The steel in and of its self was expensive and rare.

Raw ore was used. You did not just order a billet of pure foundry steel. You melted ore, separated out the different grades of metal, folded and refined it to pound out impurities.

Japanese smith's smelted tons of black iron ore sand to get smaller quantities of quality steel. It took tons of charcoal to keep the furnace hot enough long enough to get the heats necessary to melt the ore into the seperate grades of iron and steel. Just to get that little bit of higher quality steel took a crew of highly skilled experts nearly a week of constant labor. And that was not even the sword making process. Just the beginning of the process. The sword maker still had to separate the grades, forge weld, fold and forge again and again.

High quality steel was expensive, and pretty rare in and of its self.

If you are making steel in ye-olden days, the ore you dig out of the ground is not 1095, or any other clean, quality steel (let alone high catbon, super duper, strong wear resistant high speed wonder tool steel).

It's like production cars today. Your run of the mill car uses steel frame, and aluminum body. Exotics like carbon fiber and titanium, etc, make a faster, lighter stronger safer car. But they are more expensive.

Quality high carbon steel was like carbon fiber or titanium back then . It was there, but more expensive to make and use, and so, used in smaller amounts to save raw material costs.


Another thing to consider, is back in olden times, labor was pretty cheap! Labor was basically the cost of feeding the laborer, and housing him (often poorly, at that!). At least in regards to lower skill. But even the best sword smiths and masters used apprentices for the less skilled menial jobs. Many of the smiths may not have even been free (fudal systems, serfs, slavery etc make for cheap labor).

Just some thoughts.....