What is Carbon Steel

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me2

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Oct 11, 2003
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Prompted by Noestotails carbon steel folder thread, I'm a little confused over the generally accepted definition of carbon steel. At what point does steel have enough elements added that its not carbon steel (generic term) anymore. Of course the stainless steels are out, since they have their own classification. Is the term "carbon steel" limited to steels like O1, W1, 1095, 5160, etc, or are A2, M2, D2, S7, M4, etc grouped with "carbon steel"? I personally think of anything that must be water or oil quenched to fully harden as carbon steel. Air hardening high alloy steels are the gray area for me.
 
Carbon steels are the 10xx series where [other than Mn and Si ] carbon is the only alloying element such as 1095. 5160,9260 ,52100 are Alloy Steels .The number 51xx indicates the major alloying elements and their amounts while the last two [or three] numbers indicates carbon content.So 5160 tells us that it contains .70-.90 % Cr and .60 C...The letter series are Tool Steels .The letters do mean something to us metallurgists anyway. A -air hardening, O-oil hardening, W-water hardening,D- cold work Die steel, S-high Silicon steel for shock applications , etc. These are old AISI designations . Things get a bit confusing with things liks S30V ,154CM and various foreign steels.How they are quenched has nothing to do with it !
 
Mete,
Thanks for the quick reply. The 10xx series are the only ones that are technically (classified by non-knife industry) carbon steels. Anything else is alloy steel of some persuasion. However, if I come to this site and ask for a carbon steel blade material, I will get responses that are quite a bit outside that classification. In the thread about carbon steel folders, the responses range from 1095 to A2 and even to M2. While these 2 are obviously not plain carbon steel, in knife talk, they get lumped into the carbon steel category. In an editorial in Tactical Knives, they basically lumped everything into stainless and carbon steel. This was years ago, and some of the statements were irksome to me, which is the only reason I remember the article. Then they started talking about sharpenability and the (IMO) myth that carbon steel is easier to sharpen than stainless. Then the question was posed comparing ease of sharpening when the stainless is 12C27 and the "carbon steel" is M2 at over 60 HRc. All I'm trying to do is nail down how broad the term "carbon steel" is in knife talk.
 
For us laymen (not mete ofcourse but I mean the rest of us) we generally tend to lump every steel that has less than 13 percent chromium content as being carbon steel.

I'm s ure the exact definition of stainless steel is a lot more complicated than that though.

edited to add: And that's why D2 steel with 12 percent chrome is often referred to as semi-stainless around here since it's on the verge of being outright stainless.
 
me2, a assume they just divide it into stainless steel and non-stainless steel and call the non-stainless - "carbon steel" .That's total misuse of the term since there is a vast difference between 1095 and M2 [even in NZ !!]
 
A difference a pro like you would understand completely. But most of us just find it easier to devide steels simply as carbon or stainless even if it's really more complicated!

When you study something for many years you become very careful of the exact details and differences.
For the rest of us though it's just easier to lump a whole bunch of varrying low chrome steels as "carbon steel" even if it's not the accurate term.

Atleast I think that's the way most people think around here anyway.

BTW, mete, while I have your attention, my favourite steel and the one I personally use to make my knives is AISI 9260. What would you call it?
 
I'd like to know more about 9260 myself. A coworker does sword cutting demos and that steel seems popular for the beginners because it is more forgiving of a sloppy cut. How does it work for knives?

I guess I'll just have to accept the standard knife talk definitions of carbons steel, "if it doesnt rust, its stainless, if it does, its carbon steel." Seems overly simple to me, especially with the latest developments in steels.
 
Emanuel said:
For us laymen (not mete ofcourse but I mean the rest of us) we generally tend to lump every steel that has less than 13 percent chromium content as being carbon steel.

I'm s ure the exact definition of stainless steel is a lot more complicated than that though.

edited to add: And that's why D2 steel with 12 percent chrome is often referred to as semi-stainless around here since it's on the verge of being outright stainless.
Click to expand...
Yeah, I'm guilty as charged with that. Probably my dumb posts that that made the poster wonder.
 
9260 is similar to 5160 except that it has no chromium, and 2% compared to .23% silicon. It's high silicon content would make it an alloy steel.
 
Yes Keith is correct. 9260 like 5160 is often used for suspension springs for autos.I handles [HT and forging ] in a similar way also.In my days as a fencer I found that was the steel they used !
 
I've heard some say 9260 was too soft and couldnt hold an edge, but it doesnt seem like it would be any softer than 5160, what with the same carbon content and all.
 
willis said:
Case CV=carbon steel
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That depends on which definition of carbon steel you are using. CV is not a true carbon steel. It is 50100B or 0170-6 and would be considered an alloy steel, because it contains chromium and vanadium. If you are going by the definition of a carbon steel being any steel that isn't stainless, CV would indeed fit that description.
 
excellent question....powder steels have muddied the water too.



I think it's accepted that there are two general categories (stainless and non-stainless)...and one murky gray area (A2, D2, etc.)



That said.....any stainless steel with enough carbon in it WILL rust. !
 
Daniel Koster said:
That said.....any stainless steel with enough carbon in it WILL rust. !
Click to expand...

Not to be a PITA knowitall, but even very low carbon content (< or = to 0.03%) stainless will rust.

So I guess in answer to my original question, there is no clear cut definition universally used in knife talk.
 
I think you'll find we agree on that point. ;)

"enough carbon..."

:D :p






Interesting conversation I became party to (unwittingly):

Apparently, carbon steel is easier to sharpen than stainless steel.


Do you guys find this to be true?
 
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