What makes one "hard" edge better than another?

Yes, the standards for "high carbon" vary depending on who is making the divisions. In RR spikes, HC is .45%.

For knives it is pretty much as Willie said. IIRC, I consider for knives - .00% - .40% too low; .45%- .60% low; .65% - 80% medium; .85% - 1.20% high; 1.25%-2.00%% very high ( only used in high alloy stainless steels); 2.50% and up cast iron (too high, no good for knives)
 
Good info as I make more knives I find myself more and more interested in all the steels and compositions and what does what...good stuff
 
bladsmth said:
For knives it is pretty much as Willie said. IIRC, I consider for knives - .00% - .40% too low; .45%- .60% low; .65% - 80% medium; .85% - 1.20% high; 1.25%-2.00%% very high ( only used in high alloy stainless steels); 2.50% and up cast iron (too high, no good for knives)
Click to expand...

There are carbon steels used for knives with carbon content higher than 1.25%:
1.40% - Vanadis 4E
1.45% - M4
1.50% - D2

Two carbon steels with almost 2.5% carbon are:
2.45% - K390
2.45% - A11

I was surprised by the edge holding of A11. It has out performed every steel I've ever tested. I have not tested K390.

Chuck
 
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It all depends on where the carbon plays in the matrix.
To get maximum hardness you need a 0.84% C martensite; depending on how much alloy elements you have, they "eat" some of the carbon up into (mostly) carbides, subtracting it (or replacing it depending of the alloy element) from the austenite solution...that's why you can have high alloy steel up to 2.45% C and still have a martensite with 0.84% C + alloy products which bind the extra carbon.
If you didn't start with 2.45% C in those formulas, your martensite matrix would have resulted hypoeutectoid (<0.84% C) or even to the extent of not being hardenable at all.
 
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I added the word "stainless" as an afterthought, because most folks will be dealing with that level of carbon in stainless. Yes, there are some tool steels in that range.
 
I never really thought of the high alloy "tool" steels as carbon steels. I guess they are, but the heat treatment is more like stainless, and aren't friendly for the average smith.
 
I agree, the stainless are very complicated steels...it is difficult to let all that alloy elements get along toghether without having them fighting each other, both in formulating those steels makeup and heat treating them ;)
I'm not ready/equipped to mess with SS yet, but i had made a 14c28n blade to try and with happy unexpected results....now back to simple rewarding carbon steels :)
 
I had some really good experiences with stainless. Since I send my blades out for HT, the complexity of the process isn't a concern for me, so I get to take advantage of some of the other properties of stainless that make it more of a pleasure to work with... such as starting off with thinner billets, and being able to get closer to the real edge pre-HT.
 
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