Are the CPM's really steel?

  • Thread starter Thread starter tek
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tek

Hey guys and gals,
According to the current Spyderco catalog and web pages "By definition, steel is a combination of iron and no more than 2% carbon." But in the "steel" charts the carbon contents of CPM 420V and CPM 440V are listed as 2.20% and 2.15%, respectively. So are the CPM "steels" actually steel or are they just called steel to keep from causing problems or confusion? Thanks for any info.

Travis
 
Good question. I haven't thought about that.

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-Dennis-


 
That definition probably just predates the CPM series and just picks the "2%" number because no steel produced by "normal" methods goes over that mark. The intent was likely to exclude materials that are not primarily iron, not to exclude new particle-formed materials that manage to pack in a few tenths of a percent more carbon. I don't think we should stop considering the CPM series "steel" over that.

-Drew
 
The traditional top end cutoff for carbon content in the definition of "steel" is to distinguish it from the hard but brittle "cast iron" material. Back a couple hundred years ago they figured out that it was high carbon content that made the difference. A classic use for cast iron is old steam engine wheels.

I guess we need a new definition of steel to accomodate alloys that have forced some ductility and toughness into these higher carbon content mixes.

[This message has been edited by Jeff Clark (edited 20 August 1999).]
 
I agree with Drew and Jeff. We didn't write the difinition, just copied it. Perhaps time has changed it.
sal
 
Cast Iron is basically iron in which the carbon content is above the maximum solubility of austenite at the eutectic temperature. In a plain iron-carbon compound only this is 2.14 percent by weight and steel is less than that basically. High alloys may change this number significantly.

In cast irons because the carbon content is so high you can easily get carbon in the form of graphite in the iron. Cast irons also have a decent amount of Silicon to enhance the formation of graphite. If I had to make a guess I would say that the CPM steels behave like steels and not cast irons when their carbon content exceeds 2.14 percent because the carbon is tied up in all the carbides due to the extreme amount of alloys present. CPM does have an email though and you can contact them off of their webpage.

-Cliff


[This message has been edited by Cliff Stamp (edited 31 August 1999).]
 
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