ZDP-189: not a 'steel'?

elkins45

elkins45

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Jun 17, 2006
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So I was reading the 2008 Spyderco catalog today and noticed this text:

"EXOTIC STEELS are generally accepted as steel, but by definition are not steel. Examples of Exotic Steels include H1, ZDP-189, Talonite and Titanium."

I understand the other three, but why isn't ZDP-189 considered to be a steel? Steel is iron alloyed with carbon, and ZDP has LOTS of carbon.

Is it the fact that it has SO much carbon or maybe because it has so much chromium?
:confused:
 
ZDP has so much carbon and chrome that it's impossible to make it in other way than sintering. It should be called hmmm... a sinter?
I don't understand why H1 isn't a steel.
 
cali said:
ZDP has so much carbon and chrome that it's impossible to make it in other way than sintering. It should be called hmmm... a sinter?
I don't understand why H1 isn't a steel.
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im with you there- i know about talonite and titanium but not the other 2
 
Pretty sure there's no carbon in H1, and steel needs to contain carbon to be considered steel.
 
Steel is defined as having a range of carbon content. Both H1 and ZDP fall outside of that range. Obviously a more modern definition is needed.

sal
 
It doesn't matter much Zdp-189 is awesome....its a pain to sharpen but it stays sharp longer than any steel or non steel around.
 
H-1 has 0.15 % C, austenitic stainless steels (304, 316 and others) have less carbon but they're called steel ;)
 
The nitrogen used in H-1 acts a bit differently than the carbon it replaces. It acts the same way carbon does within the steel molecules, but it also aids in the bond between the molecules, which carbon doesn't. H-1 is actually a ceramic.
 
I think when the carbon content hits 3%, steel becomes cast iron - at least using the older foundry methods. Obviously, ZDP is not cast iron...
 
I think a steel is supposed to have between 1% and 2% carbon. ZDP has ~3% carbon, and H1 has almost no carbon (but I guess that would still make it a steel?)

Not 100% sure.
 
I think the definition would be determined more by the maximum amount of carbon you can put in steel before it turns into cast iron (steel starts to curdle with too much carbon). IIRC the limit is around 2%. That has always been one of the benefits of powder metallurgy, you can use way more carbon than chemistry would normally allow.
 
Sal Glesser said:
Steel is defined as having a range of carbon content. Both H1 and ZDP fall outside of that range. Obviously a more modern definition is needed.

sal
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You are clearly right.

I would guess the original definition was made before the processes used to create H1 and ZDP were discovered.

If I'm wrong, I'm sure someone will come by to correct us both. :)
 
yablanowitz said:
The nitrogen used in H-1 acts a bit differently than the carbon it replaces. It acts the same way carbon does within the steel molecules, but it also aids in the bond between the molecules, which carbon doesn't. H-1 is actually a ceramic.
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Really? :eek:
 
yablanowitz said:
The nitrogen used in H-1 acts a bit differently than the carbon it replaces. It acts the same way carbon does within the steel molecules, but it also aids in the bond between the molecules, which carbon doesn't. H-1 is actually a ceramic.
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Not according to the ASTM definition, as reported on Wikipedia:

"The American Society for Testing and Materials (ASTM) defines a ceramic article as “an article having a glazed or unglazed body of crystalline or partly crystalline structure, or of glass, which body is produced from essentially inorganic, non-metallic substances and either is formed from a molten mass which solidifies on cooling, or is formed and simultaneously or subsequently matured by the action of the heat.”[1]

There's still a whole bunch of metal in H1, so it doesn't seem to fit this definition.
 
OldPhysics said:
You are clearly right.

I would guess the original definition was made before the processes used to create H1 and ZDP were discovered.

If I'm wrong, I'm sure someone will come by to correct us both. :)
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AFAIK that definition refers to plain carbon steel, without additions. as I said austenitic stainless steels can have no carbon at all, but they're called steel. But if H1 has crystal structure different than steel, it should be called... in some other way ;)
 
From geo classes in college I am unsure that 'glass' can be said to be non-metallic. Glass is simply liquid rock, containing metals and non-metals, that cools too quickly to form large crystals. I guess I could be wrong but that is at least how I remember it.
 
iamtoast said:
From geo classes in college I am unsure that 'glass' can be said to be non-metallic. Glass is simply liquid rock, containing metals and non-metals, that cools too quickly to form large crystals. I guess I could be wrong but that is at least how I remember it.
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Glass, in its traditional sense is silicon dioxide. Both are non-metals, chemically speaking. There can be some metallic impurities (lead glass, for example) but the bulk is still inorganic.

Glass, by definition is amorphous, which means that it does not have a crystalline structure. I'm not sure if a ceramic is crystalline, but I'm sure that ZDP is crystalline.
 
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