What is Carbon Steel

[Confederate]

So...what about my "high carbon" "surgical stainless" 420J2 Gerber? I've opened many a bag of potato chips with that knife and I've never had to sharpen it.

In all seriousness, there's so much bunk about steel floating around that you pretty much have to familiarize yourself with the steel charts. Advertising inaccuracies are now rampant. A number of years ago, the Navy tested a Smith & Wesson Model 60 stainless revolver. Along side of it they put the same model, but in carbon steel (Model 36). They exposed both to salt sprays and found that though the stainless initially resisted corrosion much better than the blued carbon steel gun, there was a point in which the stainless gun began rusting. And once it started, it ran away and became even more corroded than the blued gun. That surprised everyone.

The stainless guns also were known to scratch a bit easier, indicating that it was softer than the carbon steel guns. However, it withstood heavy loads better than the carbon guns and the flame cutting at the barrel/cylinder gap was significantly less in the stainless guns.

Cold Steel sold its Recon Tantos made from a coated carbon steel. Once its supply of carbon steel ran out, they began making the knife from AUS8 stainless. Now it seems that everyone wants one in the old carbon steel simply because it's no longer available; however, when it was freely available in carbon steel, there was only moderate interest in the knife.

I also recently procured a Smith & Wesson fixed blade stainless tanto for a great price. I was expecting it to be garbage, but I was very favorably impressed. Not only was it beautifully finished, the quality seemed first rate. I was very surprised. Even so, all things being equal, I'd rather have a carbon steel knife. I heard of one fellow (maybe here) who took his Cold Steel Recon Tanto carbon steel diving in salt water. When he got home, he rinsed it in cold tap water and dried it with no problem. I've also seen people who improperly store blued guns for years and never had any rust. Others, though, see rust in very short order. The oil in one's skin has a lot to do with it. I've honest-to-goodness seen people who can corrode any type of steel that has even a teeny amount of carbon, just by touching it. They are truly the cursed of the Earth.
Have you ever seen rust fingerprints on a gun? I have, and it ain't pretty. But it is pretty amazing.

 

[thombrogan]

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

Do you guys find this to be true?

Not really. Thinner edges on harder steels are generally easier to sharpen than thicker edges on harder steels and thicker edges on softer steels are generally easier to sharpen on softer steels. And the General Lee might have either 5160 or 9260 leaf springs.

 

[Cliff Stamp]

Not really. Thinner edges on harder steels are generally easier to sharpen than thicker edges on harder steels and thicker edges on softer steels are generally easier to sharpen on softer steels.

This is a vague property, is "ease of sharpening"

1) ease of grinding
2) ease of burr removal

-Cliff

 

[langchop]

Very interesting read..

My understanding has always been thus:

1. The vast majority of steels, regardless of what they are called, contain carbon. The carbon gives it its specific 'steel' properties and various additives can be added to refine grain or the like. Additives may inclide non metallics such as Silicone. Add Silicone till the cows come home and it is still carbon steel.

2. Stainless steel is not rust proof but only rust resistant. 13% Chrome is not a magical threshold between rusting to hell and never ever showing a sign of corrosion, but its just a number chosen by metallurgists because it seems to be an appropriate point of distinction between stainless and non stainless steels.

3. 'Alloy' refers to mixture of two or more metals. If its only got iron plus other non metal additives it is not referred to as an alloy. If its got only traces of other metals it is not considered an alloy either.

Here my grey area: Some Alloys rely on solid solution hardening of the alloys and some alloys still rely on carbon as the main hardening mechanism? Isnt it practical for these to be referred to as carbon steels? (or even carbon alloys?)

Lang

 

[Guyon]

This is a vague property, is "ease of sharpening"

1) ease of grinding
2) ease of burr removal

-Cliff

I'm pretty sure ease of sharpening means how easy it is to sharpen the knife and is dependent upon numerous factors such as the steel, the sharpener's skill, etc.

Ease of grinding and ease of burr removal would similarly depend upon the skill of the grinder or remover. In the case of a machine performing the task, any such ease would still be affected by variables such as angle and pressure and sharpening media, all of which would depend upon an engineer or operator.

 

[Cliff Stamp]

Ease of grinding and ease of burr removal would similarly depend upon the skill of the grinder or remover.

You can measure these things by direct material property, just like you can measure toughness directly. Toughness of an edge is also dependent on the skill of the user, but you can define it quantitatively anyway indepedent of that.

Ease of grinding, or speed of metal removal is pretty much inverse to wear resistance. However ease of burr removal is dependent on hardness, aus-grain size, and carbide volume. As hardness increases, aus-grain size decreases, and carbide volume decreases then ease of burr removal increases.

Thus for example the worse steel to sharpen would be something like :

CPM-15V at 56/58 HRC

The steel would still be slow to grind even when soft due to the massive carbide volume but would now burr very badly due to the low hardness. In contrast

13C26 at 63/65 HRC

Would grind much easier and burr almost insignificantly. My point was that it was much too vague a term, it is like "edge retention", that is also useless because it can not be determined without further constraints. About the easiest steel to sharpen would be something like 12C27M at max hardness as the wear resistance would still be low but there would be almost no burr formation. This would be similar to a 1050 or similar carbon steel.

-Cliff

 

[Guyon]

You can measure these things by direct material property, just like you can measure toughness directly. Toughness of an edge is also dependent on the skill of the user, but you can define it quantitatively anyway indepedent of that.

Ease of grinding, or speed of metal removal is pretty much inverse to wear resistance. However ease of burr removal is dependent on hardness, aus-grain size, and carbide volume. As hardness increases, aus-grain size decreases, and carbide volume decreases then ease of burr removal increases.

Thus for example the worse steel to sharpen would be something like :

CPM-15V at 56/58 HRC

The steel would still be slow to grind even when soft due to the massive carbide volume but would now burr very badly due to the low hardness. In contrast

13C26 at 63/65 HRC

Would grind much easier and burr almost insignificantly. My point was that it was much too vague a term, it is like "edge retention", that is also useless because it can not be determined without further constraints. About the easiest steel to sharpen would be something like 12C27M at max hardness as the wear resistance would still be low but there would be almost no burr formation. This would be similar to a 1050 or similar carbon steel.

-Cliff

If you mean simply "stock removal" when you say "grinding," then I'll agree that you can predict "ease" based on the properties of the material and the properties of the abrasive media. Same idea applies to burr removal.

However, when you talk about ease of grinding in a knifemaking context, so many other subjective factors are often brought into play, most of which depend upon the skill of the person in front of the grinder. By this same token, burr removal becomes a more subjective, "vague" term when you introduce a human being into the equation. All I'm really saying here is that, for purposive grinding or burr removal (ie. making a knife or sharpening a knife), technique matters. So does the person holding the knife.

Who's your audience here? Are you talking to metallurgists? Knifemakers? Knife users? Terms have different connotations dependent upon the audience you're trying to reach and the context in which you're couching your descriptions.

This is all off-topic, of course, since the original question is "What is carbon steel?" In this respect, one of your sentences above might be useful to the original question:

As hardness increases, aus-grain size decreases, and carbide volume decreases then ease of burr removal increases.

 

[psy-ops]

Why is AUS8 so damn good?

I am totally perplexed by that steel. It is stainless(?) It is soft and it is cheap(?) why? How?

Excuse me if my questions are off topic.

 

[Cliff Stamp]

If you mean simply "stock removal" when you say "grinding," then I'll agree that you can predict "ease" based on the properties of the material and the properties of the abrasive media.

I was assuming we were addressing an individual sharpening a used knife, not actually making the knife from bar stock. The primary issue then is just how much steel comes off with each pass on the stone. This is what almost everyone complains about when they note hard to sharpen. "I spent 2 hours last night on the RazorMaker and the knife is still dull."

The problem here is that the grindability is so low that it takes forever to remove the steel. This is why S90V and similar have a reputation for being difficult to sharpen. In reality this problem means the knife is either ground really suboptimally for the steel, or the steel is a horrible match for the knife. Try sharpening a Krein or Wilson knife and see if grindability is ever an issue.

By this same token, burr removal becomes a more subjective, "vague" term when you introduce a human being into the equation.

Not really, it is this simple. Give a hundren people a S7 knife and a T15 knife and ask them to do various activities which are impact related and they will all notice that the S7 blade is much tougher. Similar will be noted if you compare burr removal on properly hardened 13C26 vs S30V. Yes you will experience variation, so you talk about samples and not individuals. Properties always refer to samples to refer to populations, not individuals, variance is never a limitation.

I am totally perplexed by that steel. It is stainless(?) It is soft and it is cheap(?) why? How?

AUS-8A has a maximum hardness of about 62/63 HRC after tempering. It is one of the better steels for knife blades if you want a high push cutting edge retention as the carbide volume is low in comparison to something like 440C. It will also be tougher, easier to grind, etc. .

Lots of high quality knife steels are very cheap, 52100 is not an expensive steel, 1095 is very cheap, some like the spring steels are even free or available as scrap. The expensive ones generally just have lots of carbide, this is not always a good thing as it makes steels brittle, reduces corrosion resistance and lowers edge retention in many aspects.

-Cliff

 

[Guyon]

I was assuming we were addressing an individual sharpening a used knife, not actually making the knife from bar stock.
-Cliff

If you're talking about an individual sharpening a used knife, then a phrase like "ease of [anything...fill in the blank]" depends as much upon the individual's skill as upon the properties of the knife. That's my point.

Ease is a subjective term when people are involved.

Wasn't this a thread about carbon steel?

 

[me2]

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


Do you guys find this to be true?

Just as the definition of "its either stainless or carbon" is a vast oversimplification IMO, so is the general assumption that stainless is more difficult to sharpen than carbon. Using the above simplified definition of carbon and stainless, it is not true, since 10V and other very highly wear resistant steels fall into the "carbon" class. If a more technical definition is used, then it depends on the steel(s) in question. In general, I find that geometry and hardness are much more influential than steel type, the way I sharpen knives. Thin geometry or a microbevel and the absence of difficult to remove burrs make for easy sharpening, IMO. I use a belt sander to remove metal for those extra thick edges that need thinning. Dan Koster's video helps for a demo.

 

[rifon2]

As for the original post, the following seems a clear, accurate, and simple definition of "carbon steel": Alloying elements not in excess of: 1% carbon, 0.6% copper, 1.65% manganese, 0.4% phosphorus, 0.6% silicon, and 0.05% sulfur.

Then, in addition to "carbon steel", there are: alloy steel, stainless steel, and tool steel.

 

[Cliff Stamp]

Ease is a subjective term when people are involved.

Per person yes, per group, quantitative statements can be made. For example, in general, people find graphical interfaces easier to use than command line. Similar if the grindability is much higher then people will find it easier to remove material from the edge of a knife. I would severely doubt there is anyone for example would would find S90V easier to grind than 420HC.

-Cliff

 

[psy-ops]

Lots of high quality knife steels are very cheap, 52100 is not an expensive steel, 1095 is very cheap, some like the spring steels are even free or available as scrap. The expensive ones generally just have lots of carbide, this is not always a good thing as it makes steels brittle, reduces corrosion resistance and lowers edge retention in many aspects.
-Cliff

Thanks Cliff, I love the hi tech debates about steel. AUS 8 seems to have the best of both worlds. But I better stop promoting it because the pricemight rise. AUS 8 sucks.

52100, 5160 and 1095 are great steels but alot of makers charge high dollars for their knives where as AUS8 knive made is China make great knives affordable for us working folk.

 

[Cliff Stamp]

Yeah, those high prices are just for the names though, the cost of the steel is not significant.

-Cliff

 

[Keith Montgomery]

52100, 5160 and 1095 are great steels but alot of makers charge high dollars for their knives where as AUS8 knive made is China make great knives affordable for us working folk.

All three of those steels are not very expensive compared to even an average stainless.

 

[Keith_H]

All three of those steels are not very expensive compared to even an average stainless.

the steel is not very expensive on its own, but being steels commonly forged, the price goes up when masterfully pounded and folded into a beautiful piece of art- and is obviously increased over a factory ground aus8 blade.