Internal carborization for sharpness?

C

Corey789

Joined
Sep 7, 2018
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I've been toying with an idea- please say what you think if it might work out, has already been done, and such. Thanks.

What if I start with something like a 1018 tube, hammer an "hourglass" constriction in the middle, put powdered charcoal in one end, and flatten the other end, with a very small gap between the internal sides (not touching in the middle).



Thanks much for any thoughts.

Corey
 
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You are basically doing an internal pack case hardening.
The carbon could leave an ash/residue that may make the two surfaces not weld.

I think your temperature is too high. 1300-1500F would be more in the range. The carbon vaporizes at 1250F.

The bigger question is why? You will be making a non-uniform 10XX steel, which could be purchased for less than the gas and time involved in trying to make it. If you could weld this up, you could weld a bars of 1018 on each side of a bar of 1095 and make a much better san-mai.
 
Thank you much for the quick reply. Here's the thinking. Smite me if I need to be smitten :)

On san-mai (which I know nothing about), maybe begin in thickness proportions of 1018 and thin 1095 stock, that when forge hammered down to knife thickness overall, the 1095 is thin enough that the edge exposure would be very sharp?

Thanks again

Corey
 
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OK since the neck is stretched so far anyway-

Lots of geological features were made by preferential wearing patterns, can this be taken advantage of in the blade world? Am I 2000 years too late with the thought?
 
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That is the basic idea of san-mai. The sides are soft and thicker and the core at the edge is thin. This allows a very hard edge on a tough knife.
If doing a 2X4" test billet, use 1/8" 1095 and 3/16" 1018. After welding and drawing out to usable thickness, the core will be about .030" thick.
You can buy commercial san-mai with less than a 1mm core.
 
I’ve seen other knife makers try this concept on knives over the years by coating the blade with something hard like nitriding and sharpening from one side only. It always sounds good but never works.

Hoss
 
I agree you could have better results just using some san mai rather than bond different materials to steel. Something like Hitachi blue steel laminate would seem to fit what you are looking for. If you can find it with a 1mm thick core as Stacy mentioned it should work well.

The mild steel cladding would be easier to sharpen than the blue steel core, which has some chromium and tungsten. Forging out the billet carefully could also make the core thinner if 1mm isn’t thin enough.

Also the “hardness gradient” you described will happen with san mai if it is heated for a long period of time, or multiple times. If you have say a 1095 core and 1018 cladding, the carbon in the 1095 will diffuse into the 1095. So if you heated up the billet and held for say an hour or two at 1500, repeating multiple times, the carbon would diffuse quiet a bit. This would not give very noticeable or practical results, but if you want to try it out go for it.
 
Mayday, mayday.....

Corey, you’re headed down the wrong path. Find a mentor and make some knives before you try and change the world.

You’ll be better off.

Hoss
 
DevinT said:
Mayday, mayday.....

Corey, you’re headed down the wrong path. Find a mentor and make some knives before you try and change the world.

You’ll be better off.

Hoss
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Thanks much for the direct warning friend, do appreciate it. I'd better watch Antman a few more times before going subatomic :)
 
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There is more going on at edge than pure wear. There is:chipping, edge role, edge deformation, carbide tear out, fatigue just to name a few. I can see self sharpening working when something needs to be relatively sharp like teeth on digging machinery but not at the the level of performance we are going for.
 
I'm with Devin. Find someone to teach you a bit about knifemaking and learn what methods are best. Self sharpening isn't a feature we deal with.

If you want to make a knife with a thin core, try some Dictum three layer steel with white paper core (also available in blue core). The billet is 330X33x3.5mm and costs only 16 euro a piece. The core is around 1mm and the sides are low carbon steel. They have lots of other layered steels and katana steel.
https://www.dictum.com/en/steel-cca...red-steel-core-layer-white-paper-steel-719615
 
DevinT said:
I’ve seen other knife makers try this concept on knives over the years by coating the blade with something hard like nitriding and sharpening from one side only. It always sounds good but never works.

Hoss
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Isn't that effectively what all those guys making ultralight titanium knives are doing by carbidizing one side of a chisel grind?
 
madcap_magician said:
Isn't that effectively what all those guys making ultralight titanium knives are doing by carbidizing one side of a chisel grind?
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Yes but the carbide layer they're depositing is thicker and less uniform than nitriding. The uniformity of the nitriding and how thin it is sounds really good since thin edges cut, but the reality is it cannot support itself in cutting thickness.

The carbidizing works because the lack of uniformity and varying thickness in application lends itself to creating a saw edge with multiple cutting surfaces, almost like a knapped blade - and why you don't sharpen the side with the carbide.

On the nitrided blade, even if you don't sharpen the nitrided side, it acts as if you did because it's so even.
 
Corey789 said:
That was the thought behind setting up a gradient that becomes tougher and less hard (and/or corrosion resistant) as you move away from the thin cutting edge. Essentially the steepness of the chemical gradient in the blade would proportion to the "grinding" profile of the blade in use.
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I understand. I think your biggest challenge will be getting that thin band of carbuerized steel centered in the edge for the entire length of the blade. The juice isn't worth the squeeze to me but I understand the fun of experimentation.
 
You could probably do it if you knew all the variables. It wouldn't work on a hand held knife. I can get a shaving edge on most knives in 2 minutes and most of the guys here do the same. It hard to beat the precision and ease of mechanical sharpening.
 
skillgannon said:
You could probably do it if you knew all the variables. It wouldn't work on a hand held knife. I can get a shaving edge on most knives in 2 minutes and most of the guys here do the same. It hard to beat the precision and ease of mechanical sharpening.
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Thank you for that. Any particular mechanical device better than others? I'm sure there's a lot on this site as well as general info out there on sharpening, so, just what you like would be great if you'd like to share.
 
The mechanical device for sharpening is called your hand. The controller that runs it is called your brain, and the interface between them is called your eyes and fingertips.

It takes only a little practice to learn to hand sharpen knives. Many of us do the first sharpening on the belt grinder running at a very slow speed, then quickly finish on a fine stone and a leather strop board. You don't need fancy stones, machines, or jigs. For most folks, a set of DMT diamond plates will last a lifetime and make sharp edges quickly.
 
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