Regular steel vs "special steels"?

D

DavidL41

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Oct 12, 2014
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For steels that are regular carbon blades what are the differences in sharpening times compared to one that has added elements like tungsten ect.

Are the regular carbon blades, say white steel a bit sharper than blue steel steel because the white steel doesnt have those elements added leading to a better sharpen -> sharper edge. Or alternatively if one was to sharpen identical knives, one white steel and one blue steel knife completely they would be the same sharpness except the blue steel would last longer than the white steel.
 
Very good question. Let's focus on Blue vs White. As you know, Blue has a bit of Cr and W to aid in wear resistance. The White being, for the most part, just iron and carbon. I have a Korin catalog that gives a graph of sorts showing you the difference between the two...and I disagree with it. They show Blue and White able to attain identical sharpness levels (I think White can get scary scary sharp...blue not so much but still crazy sharp). Then they show the White steel's wear properties immediately dropping off (think Nasdaq), while the Blue stays sharp all the way across the graph till the end, where it then drops off.

What I have seen is the White can attain an edge slightly better than the Blue. However, the superb edge that White steel is capable of will go away fairly quickly, leaving a very good user edge for a long time. Blue steel seems to take not quite the same edge as White, but the edge it takes stays that way for a long time. It is those carbides aiding in cutting that prevent such a fine edge, but like I said it is VERY sharp regardless.

Sharpening time is going to vary of course with equipment and technique. Blue is more wear resistant.
 
Sharpening time depends more on equipment and technique than steel-type. Softer or low-carbide steels are more easily shaped/carved. Soft steels (like most kitchen cutlery <55Rc) can be shaped/apexed easily with a "steel", removing apex-material and re-aligning the edge, but the low hardness makes it difficult to maintain this edge and excessive burr-formation is common. Harder (~60Rc) steels benefit from re-alignment but generally require a finer/harder abrasive to establish an apex - Arkansas stone, etc. - and hold a fine edge much better. Steels with more/harder carbides require sharper/harder abrasives to achieve a high finish at the apex, e.g. SiC or diamond, but can achieve the same level of apex-refinement as any other steel, with an average apex-diameter ~0.5 um.

The alloying elements in super blue are carbide-formers and grain refiners, the goal being the creation of numerous tiny ceramic particles/plates embedded in the ferrite matrix to protect it from wearing away with use. If your abrasive (hone) isn't hard+sharp enough to literally carve through these particles, it can only skate over the top of them (no/slow progress) or knock them loose (disjointed progress). At the apex, knocking a carbide loose leaves a gap (between "teeth") which can be beneficial or detrimental depending on the desired edge-refinement. With very fine carbides, the gap/teeth would be very fine, possibly finer than the grit of the abrasive scratch-pattern meaning you wouldn't be able to tell. With larger carbide-aggregates, the gap is larger. If you don't want a gap, use finer/sharper/harder abrasives and good technique. Technically a steel with carbides in the apex can achieve a sharper edge (i.e. lower apex diameter) due to the increased hardness of the carbides, but the advantage would be minimal IF achieved in the first place.

Also a "toothy" edge is sharper than an "un-toothed" edge with the same angle-geometry since the "teeth" function exactly as expected, i.e. as penetration points, focusing the same cutting force over a smaller surface area and "biting" into material more easily. Achieving "teeth" of appropriate size is more a matter of abrasive-grit selection than steel type, but harder steels will hold those teeth in alignment better.

Blue is superior to White in that it can take a higher hardness (stronger/finer apex, i.e. sharper) and possesses more abrasion-resistant carbides (more wear-resistant), but won't require any additional sharpening-time when proper equipment is used.
 
David martin - Yes something like that. Easy to sharpen but could potentially gets sharper or harder to sharpen and lasts longer.



In simple terms - using 1k japanese ceramic stone and 6k ceramic japanese stone:

White steel/O1 steel - For estimate sake how long can this cut leather till its too dull to cut. How long to get it sharpened using the two stones above. How long for sharpening with just a strop or 6k stone for touch ups.

(super) Blue steel/ A2 - Same as above.
 
DavidL41 said:
David martin - Yes something like that. Easy to sharpen but could potentially gets sharper or harder to sharpen and lasts longer.



In simple terms - using 1k japanese ceramic stone and 6k ceramic japanese stone:

White steel/O1 steel - For estimate sake how long can this cut leather till its too dull to cut. How long to get it sharpened using the two stones above. How long for sharpening with just a strop or 6k stone for touch ups.

(super) Blue steel/ A2 - Same as above.
Click to expand...

Super Blue can be taken to higher hardness = stronger, thinner (finer) edge. Super Blue has more+harder carbides in matrix = less wear, and can be sharpened in the same amount of time as White/O1 using those abrasives. It is superior.
 
chiral - is this observation or experience? Sounds right but when things are tested they sometimes are different then the initial observation.

Im curious why carter cutlery would say white steel is better than blue and creates a sharper edge. In general blue steel number 1 how much longer sharpness are we talking about compared to white number 1 - 30 percent? 50 percent? double or longer?
 
Your question is a logical one. Wanting to get some specifics about two things: Absolute sharpness of an edge in a particular steel. Edge holding of that same steel.

It becomes a complex question for several reasons. First, measuring the sharpness. You have to define some type of test to determine this. Thus why a lot of people push cut phonebook paper, or shave arm hair. But these types of tests, while showing you something about the edge, don't necessarily mimic what you might be cutting in the real world. White and Blue steels (as far as I know) are most commonly used in kitchen cutlery. So some sort of kitchen task would probably be a better measure, but what to use? It would be hard to figure out a universal kitchen standard. Thus why other more arbitrary measures are used: How many rope cuts, how many inches of cardboard, how many cuts of thread, etc, etc. All of these measures are flawed, but at least they are repeatable. Edge finish is very important here too. If your task is to cut rough material, especially with slice cuts, a coarse finish works better. This is super important and can affect edge holding in a huge way.

Which brings us to edge holding. Again, how do you test it? Most would use some repeatable test like I outlined above: Rope cutting and that type of thing. It's not real world, but it's repeatable. I know from my own informal testing how long my blades hold their edges in my work tasks (mostly cutting open boxes, pallets, etc). I have kind of a "profile" of the steels I use and I know which ones hold edges for the longest, and I've started to figure out which edge finishes work for the longest.

To me, the difference in edge holding between a basic steel like 8Cr13MoV and S30V isn't huge. It's about the same for initial sharpness. They both dull down from screaming sharp to just "ok" in a very short amount of use. Then the S30V holds a useable (but kinda dull) edge for something like 2 or 3 times as long as the 8Cr blade. I always get annoyed and resharpen the S30V because I want it sharper. Just an example.

You might find someone who's done a more real world test of White versus Blue versus Super Blue. Or even a standardized test of some sort. Otherwise you come down to generalizations.

Brian.
 
Murray Carter likes to extole the virtues of White steel for sure. I think the main reason more than anything is the time and effort he spent under a smith(s) in Japan learning how to properly forge and heat treat white steel. Blue steel is MUCH more forgiving in forging and heat treat than White. And again....due to the comp...White steel CAN attain a higher sharpness than Blue, that super duper razor edge quickly goes away allowing a good user edge to last a long time.

The Blue won't get quite as sharp, but what it does get is sharper than the White's "user" edge, and lasts longer too. Super Blue is hard for me to compare, I have never used it. It has V to help pin grain boundaries during heat treat, but again Super Blue's main carbide is W. Combined with even MORE carbon than Blue or White.

Giving quantified answers to "how sharp is this" "how long will it last" etc is just not practical. Just like steel compositions cannot tell you the whole story of how a steel will perform. Take AEBL for instance. Very simple stainless steel. Works WONDERS over more complex steels.
 
Just looking at A.G.Russell's Steel Chart. White steel doesn't come close to A2. Which would fit nicely between this and blue steel in most departments. Yet blue steel should even give better edge retention that D2. The two your asking about are not close in elements. So, yes agreed, this comparison is 'not practical'. The blue steel (no experience) should hold it's edge 60-70% longer than white and be about that much harder to sharpen with it's % W. If your wanting decent edge retention, toughness, ease of sharpening with some maintenance A2 would get my nod. DM
 
samuraistuart said:
Murray Carter likes to extole the virtues of White steel for sure. I think the main reason more than anything is the time and effort he spent under a smith(s) in Japan learning how to properly forge and heat treat white steel. Blue steel is MUCH more forgiving in forging and heat treat than White. And again....due to the comp...White steel CAN attain a higher sharpness than Blue, that super duper razor edge quickly goes away allowing a good user edge to last a long time.

The Blue won't get quite as sharp, but what it does get is sharper than the White's "user" edge, and lasts longer too. Super Blue is hard for me to compare, I have never used it. It has V to help pin grain boundaries during heat treat, but again Super Blue's main carbide is W. Combined with even MORE carbon than Blue or White.

Giving quantified answers to "how sharp is this" "how long will it last" etc is just not practical. Just like steel compositions cannot tell you the whole story of how a steel will perform. Take AEBL for instance. Very simple stainless steel. Works WONDERS over more complex steels.
Click to expand...

The determining factor in attainable sharpness for a given substances is attainable hardness which is determined by carbon content in steel, and by grain-refinement, accomplished through specific alloying elements and HT. Blue#2 and White#2 have the same carbon content, but Blue's tungsten (W) content allows for a more refined grain = sharper edge at same hardness, and more abrasion resistance in that edge = Superior. White#1 & Blue#1 have higher carbon content than the previous 2 but the same principles apply, and Super Blue has even more carbon with grain-refiners and carbide formers to support the matrix = even higher attainable hardness with same grain-size and increased carbide content = higher attainable sharpness and abrasion resistance.

THAT is what the composition tells you - White steel canNOT achieve higher sharpness than Blue unless comparing White#1 to Blue#2. Now that might not make a difference if you can't actually achieve that superior sharpness in your sharpening - the steel doesn't automatically have that sharpness, you still need to get it there through proper equipment and technique, THAT is the limiting factor. A good maker using White#2 might achieve a thinner, longer-lasting edge than a lesser maker using Super Blue.
Regarding ease of sharpening, this again depends on equipment and technique. Using harder/sharper abrasives (e.g. diamond, SiC), the abrasives are so much harder than the steel-matrix, with or without carbides, that it takes no longer to abrade away the metal from one vs another. With inferior equipment, you may experience a difference in sharpening the resistant material vs the weaker one.

Here's a good reference link: http://giantcypress.net/post/609709105/one-steel-two-steel-white-steel-blue-steel

Regarding AEB-L, I haven't found it to be much different from 420HC, depends how hard the maker gets it (should be >59). I'm not sure what "wonders" it possesses or what "complex" steels it compares to... Often 420HC or 440A or 1095 is all you need, or the maker using it produces a better knife than some other maker using a better steel. *shrug*
 
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