4140 as a san mai jacket steel

[jdm61]

I was checking out the Murray Carter/Weimy FS1 knives and on the original version of those they went with a san mai blend of 1035 and Hitachi Super Blue instead of the normal "soft iron" or non-harding stainless. The explanation was that they wanted a very tough "springy" mixture that could be taken down very thin, like as thin as .113 at the spine, and still have a very hard edge so they could get a very tough but very light combat/outdoors blade that could cut like a mutha. I don't have any Super Blue, but I do have about 250 pounds of CruForgeV and that got me to thinking. Would a blend of that with a 4140 "jacket" make for an interesting san mai blend? The "normal" HT for Cru Forge with the 400F temper leaves you with the steel at about 61 and abrasion resistant as all get out. it also takes a scary edge. As best as I can tell,4140 temper at 400F would end up in themed 50's, maybe lower because I wond'treally austenize at the over 1500F temps you would normally use for 4140 for say a tomahawk. Any opinions?

 

[Stacy E. Apelt - Bladesmith]

Toughness is mostly a trait of steel alloying .... springiness is mostly a trait of the thinness and geometry.

The traditional softer skin san-mai was developed mainly to save precious steel. The benefit was that the thin steel core could flex more without breaking, and the soft skin would bend and not crack. Today, it is the visual effect that is desired in san-mai. 4140 would work as well as 1035 or 00Fe.

 

[Matthew Gregory]

Man, I wish more people understood that.

 

[Tenebr0s]

I do think there is still a benefit to sanmai/laminated blades in knives where the user may wish to thin the knife on water stones. The soft jacket abrades away easily, making the job less hellish. This is useful especially in kitchen cutlery, and one of the reasons that the Japanese still make knives this way.

 

[timos-]

I was checking out the Murray Carter/Weimy FS1 knives and on the original version of those they went with a san mai blend of 1035 and Hitachi Super Blue instead of the normal "soft iron" or non-harding stainless. The explanation was that they wanted a very tough "springy" mixture that could be taken down very thin, like as thin as .113 at the spine, and still have a very hard edge so they could get a very tough but very light combat/outdoors blade that could cut like a mutha. I don't have any Super Blue, but I do have about 250 pounds of CruForgeV and that got me to thinking. Would a blend of that with a 4140 "jacket" make for an interesting san mai blend? The "normal" HT for Cru Forge with the 400F temper leaves you with the steel at about 61 and abrasion resistant as all get out. it also takes a scary edge. As best as I can tell,4140 temper at 400F would end up in themed 50's, maybe lower because I wond'treally austenize at the over 1500F temps you would normally use for 4140 for say a tomahawk. Any opinions?

Sounds like a fun experiment to test for sure. With all the san mai I have tried , it is great for the kitchen but not outdoors like you alluded to. That stainless clad san mai takes a bend and holds it, a mono steel knife might be too thin for the desired amount of flexibility, so you are hoping to accomplish more flex/spring with thicker heavier capabilities?

 

[jdm61]

Okay, okay, I'll admit that I do not actually believe that a 1/8-5/32 blade made say from Cru forge V really NEEDS to be toughened up. With that said, some people do believes that and the customers always right except for the times when they are misinformed. Either way, you do get the cool factor with san mai. My thinking with 4140 is that it may be more "compatible" the heat treat with a deep hardening steel than with the medium carbon 10xx steels.

 

[jdm61]

Stacy, I must admit that this was part of my thinking. i have a finite amount of Cru Forge and even though some people still have some for sale, it doesn't look like any more will be made. So there is a possibility of stretching out my secret stash.

The traditional softer skin san-mai was developed mainly to save precious steel.