Steel?

K

Ken Cox

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Dec 11, 1998
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I have seen a few Extrema Ratio ads in the magazines, and a quick search of the net produced a picture or two (beautiful knives) and a mention of cobalt steel.
I would like to know more about the steel or steels that Extrema Ratio uses to make knives.

And yes, welcome to BladeForums. :)
 
Near as I can tell, N690 has the following composition:

1.07 Carbon
17.0 Chrome
1.50 Cobalt
1.10 Molybdenum
0.10 Vanadium

and it's made in Sweden by Böhler's Uddeholm plant.

According to one of their charts, it sits between 440B and 440C with the addition of the cobalt. It's usually heat treated to HRC 58-60.

Bohler Material Charts
 
Actually, it is VERY close to Stellite in composition, including the cobalt. Stellite has been used for years to make industrial cutters, blades, and boring bits. Very high wear/corrosion resistance. The folks @ Extrema Ratio have toned the alloy down just a bit to make it machinable. Still, I have cut through a high number of objects, including hemp rope and cardboard (either of which dulls a blade QUICK) with mine, and can still shave with it.
 
Frank has a composition chart, and hopefully he can post it today.
 
It's supposed to perform similarly to VG-10.


Alloy composition of VG-10:

Carbon 0.95-1.05
Chromium 14.50-15.50
Cobalt 1.30-1.50
Manganese 0.50
Molybdenum 0.90-1.20
 
Actually, it is VERY close to Stellite in composition, including the cobalt. Stellite has been used for years to make industrial cutters, blades, and boring bits. Very high wear/corrosion resistance. The folks @ Extrema Ratio have toned the alloy down just a bit to make it machinable. Still, I have cut through a high number of objects, including hemp rope and cardboard (either of which dulls a blade QUICK) with mine, and can still shave with it.
Click to expand...

Actually, N690 is absolutely NOTHING like Stellite. Stellite is practically NON-ferrous (<3% usually). This is steel. Iron is the #1 component (>90% usually.)

Stellite is a Cobalt/Chromium alloy that is made up of those two elements primarily. Stellite is probably not tough enough for a big combat blade, either.

N690 does sound a lot like VG-10. We will see how it stacks up.
 
In response:
Admittedly, N690 is primarily steel, whereas Stellite alloys very greatly in composition. However, there are over 58 different alloys "wearing" the name "Stellite". It is a brand name, much like "Nissan". Additionally, of the 8 metals found in N690, most Stellite alloys have 6 of them in their composition.
"Stellite is probably not tough enough for a big combat blade, either."
Click to expand...
They use Stellite to make industrial drill bits, and industrial cutters, to bore through rock, cut through steel. A custom knifemaker actually made a fixed-blade drop-point out of a piece of Stellite once. Once. He swore he would never engage in that behavior again. It was too damaging to his equipment, as the Stellite was too difficult to forge/machine. It wore his equipment out.
VG-10 has a Rockwell hardness of 50. N690 has a Rockwell hardness of 58 to 60. Additionally, VG-10 has traces of sulphur and phosphorus in it. These are elements that are not desired in stainless steel. In the forging industry (and not just forging knives), an attempt is made to remove said elements from the steel during the smelting process.
:D
 
VG-10 has a Rockwell hardness of 50. N690 has a Rockwell hardness of 58 to 60. Additionally, VG-10 has traces of sulphur and phosphorus in it.
Click to expand...

My Spyderco VG-10 blades are definitely not hardened at 50, closer to 59, If I had to guess. They will hold an edge, better than 440C, and on par with ATS-34. I don't know where you got that information.

I don't think N690 is VG-10 anymore, their compositions vary slightly. Some have said it is based on 440C. I really don't know, I have never even seen an ER knife in person, but I think it should perfrom similar to VG-10. If Bohler places it between 440B and 440C, I wonder what the addition of Cobalt does to the performance of the steel.
 
I got that information in regards to the Rockwell hardness from a steel supplier (I actually got listings for about 30 steels...).
Cobalt is an anti-corrosion/oxidation element. It additionally adds somewhat to the impact and wear-resistance of the steel.
 
For the purposes of making knives, the name "Stellite" has been associated with Stellite 6K and 6BH. These are both Cobalt-Chromium, non-ferrous alloys.

Stellite is very wear resistant, but not very strong. It is adequate for smaller knives, but completely inadequate for larger ones.

People make knives out of Stellite 6K & 6BH all the time. Big Ones too. Simonich has made many for people who wanted extreme corrosion resistance.

Before you make any more claims on what Stellite can and cannot do in relation to knives you may want to do a search for "Stellite" or "Talonite" on these forums.

Stellite is primarily used for slicing and cutting bits in factories cutting soft materials, especially corrosive ones. It has also been used to line machine gun barrels.
 
A custom knifemaker actually made a fixed-blade drop-point out of a piece of Stellite once. Once. He swore he would never engage in that behavior again. It was too damaging to his equipment, as the Stellite was too difficult to forge/machine. It wore his equipment out.
Click to expand...

They make way better abasives and machinery nowadays. Stellite/Talonite/Cobalt alloy knives are actually easily manufactured compared to some of the super Titanium alloys as well as the ultra high Vanadium steels.
 
Hmm.

Any more comments/news on the ER steel?

A steel that's like VG-10 is very much NOT like a steel that's 440B/440C, I'd think?

I've been happy with both VG-10 and 440C (although I still like S30V and 5160! ;) ) but VG-10 seems to take a scarier, slicing-er edge...

-jon
 
And N690 is even on a higher performance level level than VG10. But debating steel is like arguing over who has the best looking girlfriend.
 
Frank,

*laugh*

When it comes to high-performance steels, yes. I do not think I could ever use those to their highest potential.

If it is that we are talking about "PAKI" steel... (or "ROSTFREI" for that matter) then... most respectfully, sir, I think I will not like to see that girlfriend!

;)

Take care,

-jon
 
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