Why s90v and all these other high carbide steels suck for knives

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kraftzion

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Steel and carbides have a lot in common with cement and gravel. If you get the right mixture of cement and gravel your concrete is strong. But if you add to much gravel, there is not enough cement to keep the gravel in place and your concrete crumbles. Crucible even state in there own literature to avoid sharp radii with these high carbide tool steels. The very definition of a sharp radii is a knife edge. The quote"Tool steels are notch-sensitive materials. The presence of notches, undercuts, sharp radii, changes in section, or any geometric features may concentrate applied stress and exaggerate the material’s tendency to break." and the article.http://www.crucible.com/eselector/general/generalpart1.html
These steels are designed for machine operations like stamping out door panels for cars out of sheet metal. Nothing even close to the angle of a knife edge is involved. At most two 90 degree angles will pass each other in close proximity and shear the sheet metal. At 90 degrees there is enough steel to keep the carbides in place and let them do there job. By all means if you consider a 90 degree angle on a knife sharp get you some s90v(funny how they even have 90 in the name) and you can saw through manila rope or what ever floats your boat until the cows come home and never have to worry about sharpening your knife again. You can also do this with a backwards hacksaw blade by the way a LOT cheaper. But if you are like me and don't even consider it a knife until you get to 15 per side, 30 degrees included or below you are best off choosing a proper knife steel. Here is a video of what happens to high carbide steels when used as a knife compared to what I consider a proper knife steel(12c27). And this is compared to s30v which was supposedly developed as a knife steel.
Now I consider 1000 strips of dirty carpet more than enough wear resistance to suit my needs. And the thing that seems to be glossed over in all these "super steel" comparisons is that you can't hone them. You can take that 12c27 after 1000 strips cut of dirty carpet and run it across a steel for about 10 seconds and your razor edge is back. If you try to hone these "super steels" all you do is move the carbides around further weakening or destroying what is all ready a pitifully weak edge. You have to resharpen them which takes significantly more time. When you sharpen these "super steels" to any angle even approaching what I consider a knife edge what you end up with is a bunch of loose or barely hanging on carbides on the edge. And just like loose gravel in your driveway when you step on it any pressure moves them out of the way. And your razor sharp edge goes away. So I implore American knife makers to get out of the gravel, stop trying to put a square peg in a round hole and start making knives out of proper knife steels again. I shouldn't have to buy a Chinese knife to get a decent steel.

EDIT: I want to make clear that Cliff didn't write this. I just used his video because it supported my(extrapolated) experience with s90v and d2. I in fact emailed Cliff the link to this post and his response was "
I would not go so far as to say they suck, but I have similar views on the utility of very high carbide steels for knives. The performance is often highly exaggerated." Also want to say that my aggravation at paying what I consider a lot of money for knives that are inferior for my use to knives that are considerably cheaper made my post more extreme than my actual views. Take price out of the equation and the only steel I think really sucks is D2. 50 micron carbides in a knife steel, give me a break.

Edit 2: Since this isn't complete without sharpening technique. I prefer a convex bezel, I use a cheap ass 1x30 harbor freight belt sander. It was $30 when I bought it $54 now. 3m micron film belts, finish with steel if the knife steel will allow it. The reason being that nothing polishes an edge like steel. 300 power camera hooked to my laptop to support this conclusion. 3m trizac belts to set bezel. I own Japanese water stones which I enjoy on some knives.Diamond plates which I don't seem to use much. One of those sharpeners that clamps the knife and the stone is connected to a rod to set the angle I don't remember the name of it. I don't care for it as a I can get a knife as sharp(or sharper) via other methods that seem more like a skill to me. I have tried leather belts, felt belts, and cork belts on the 1x30- don't like none of them as the belt is to thick and slaps around to much to suite me. My favorite was 1/4 micron diamond paste on a wore out 3m film belt. I will have to wait until I wear out another 5 micron film belt to get that back as my old one just came apart.
 
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does Cliff mention anywhere what abrasives he used to sharpen the knives with in this test?
 
I would think they're are people who are far more in the know about such things that would highly disagree with you i.e. Sal from spyderco.

There's many other factors that go into edge retention or lack there of, heat treat being a big one to make an assertion that steels with higher carbide counts suck as knife blades.

The makers are selling what people want, if you don't like the market, give it time it will change. There's plenty of options in plane jane steels that aren't Chinese made if you cared to look.
 
From the little that I've learned, pm steels at very low angles will suffer carbide tearout, microchipping, so better use low alloy for really thin angles. If you use high angles, no problem, carbides will help in wear resistance. So for extreme thin angles, one should use low alloy high medium-high toughness steel like 52100, for instance. That's why razors are not made of pm steels (the cost being another problem).
 
So if you can get the right mix for strong concrete, why cant you get the right mix for strong "super steels"? And that mix includes proper and very specific heat treatments for the desired characteristics.

When they talk about tool steels being "notch sensitive" etc. It is when the hardened an tempered steel is being used under very heavy stresses like in a 20,000 ton punch press. If your knife has a notch in it, you want the corners of the notch to have a significant radius so that you don't create a stress riser in that area. If you are not using it as a pry bar you shouldn't have any issues.

Here is an interesting read on the topic. https://vacaero.com/information-resources/the-heat-treat-doctor/1173-tool-steel-carbides.html

Here is a quote from the article.

Finally, caution should be observed in that although carbides are beneficial in tool steels for a number of reasons (e.g. strength and wear resistance) they are also likely crack initiation sites in instances where high application stress is involved.

the "sharp radii" of a knife edge is an external "radii" (If you want to equate an edge to a radius for the sake of argument).
What they are referring to though is internal radii.

I will agree though that the super steels may be more prone to edge chipping when being used hard.

Just my 2 cents.
 
I come down somewhere in the middle of this debate. I think high carbide steels have gained in popularity in part because of marketing by companies and knife testers who cut a lot of cardboard. High carbide is like high horsepower on a sportbike. You can reach an insane top speed but at the expense of torque.
You have bragging rights but for practical purposes you've given something up.
On the flip side, those against high carbide steels act like they all chip out just by looking at them. I don't think that's true either.
 
AF said:
I come down somewhere in the middle of this debate. I think high carbide steels have gained in popularity in part because of marketing by companies and knife testers who cut a lot of cardboard. High carbide is like high horsepower on a sportbike. You can reach an insane top speed but at the expense of torque.
You have bragging rights but for practical purposes you've given something up.
On the flip side, those against high carbide steels act like they all chip out just by looking at them. I don't think that's true either.
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The 2013 Kawasaki ZX-14R makes 115 lb.-ft. at 7,600 rpm. The ZX-14R, in all of its 582 pound glory, is more of a sport touring bike than a pure sport bike; but it’s no wonder you see a lot of these at the drag strip. The 14R has a torque/weight ratio of 0.20 lb.-ft./lb.
 
There are high alloyed tool steels that are very good even at low angles, like cpm3v, 4v or Vanadis 4 extra. These three, when well heat treated, will take some abuse at very thin angles, but more alloyed than that and microchiping is a reality. I have choppers made out of Vanadis 4 extra and will take severe abuse, but my edge angle is very thick so the edge would NEVER chip.
 
jill jackson said:
The 2013 Kawasaki ZX-14R makes 115 lb.-ft. at 7,600 rpm. The ZX-14R, in all of its 582 pound glory, is more of a sport touring bike than a pure sport bike; but it’s no wonder you see a lot of these at the drag strip. The 14R has a torque/weight ratio of 0.20 lb.-ft./lb.
Click to expand...

In not really in the motorcycle game anymore but it's the smaller displacement sportbikes where you see the stark difference between horsepower and torque. The "race-replica" 600cc and 750cc.
 
Maybe I didn't read the OP correctly but isn't what's being stated that he steel doesn't take well to being bent, not that it can't take acute angles? The fact that there are knives in those steels, that have worked, and tested to work well, seems to make that long explanation moot.

I find an angle of 15 degrees per side to be a bit too steep for me for any blade, even non super steels. I have come to appreciate the carbon steel on my traditionals and they almost sharpen themselves it seems compared to the stainless on my modern folders. However, 15 degrees isn't even something I desire but to each their own.

The ability to hone on a steel is a known weakness of the high hardness steels, it's goes hand in hand with the idea that they're harder to sharpen. You shouldn't have to sharpen them as much and thus you sharpen it when you're done working instead of hone it while you're working.

As always, pick your steel based on the application. If you need something that's not a super steel then don't get a knife with it. If you need stainless then don't get carbon steel. Luckily, we have tons of options and no one is forcing anyone to pay extra for the high dollar steel.
 
AF said:
In not really in the motorcycle game anymore but it's the smaller displacement sportbikes where you see the stark difference between horsepower and torque. The "race-replica" 600cc and 750cc.
Click to expand...


The big displacement sport bikes make just as much, or more torque as the V-twins. I had a Suzuki 1200 Bandit and it was a torque monster, pulling high gear down to 20 mph. The smaller ones no, but the V-twin small bikes don't make high torque either.
 
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Not sure that analogy holds up. Heat treat has as much to do as angle. I find the high carbide steels do hold an edge much longer, but take longer to sharpen and require diamond hones. I do like the ease of sharpening 12C27, 420HC etc. and the way they take a very fine edge, though.
 
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