Hey, Spyderco! What is Cobalt Special???

[Sequimite]

This silence as to what Cobalt Special steel is and why we should care is rather strange.

I have a natural tendency to want to buy all things Spyderco but if you want me to go all the way you at least need to chat me up a bit.

[jackknifeh]

This silence as to what Cobalt Special steel is and why we should care is rather strange.

I have a natural tendency to want to buy all things Spyderco but if you want me to go all the way you at least need to chat me up a bit.

Spyderco. Do you realize you should be on cloud 9? How often does a customer ask to be "sold" on a product. Your sales department must have the easiest job in the world. I bet they walk around all day with this expression on their faces :D .

Jack

[The Deacon]

At the least, it would be nice to know where it falls in terms of stain resistance. I may be reading something into Kristi's announcement that's not there, but it seems to imply that one of the purposes of the AUS420J2 outer layers is to improve corrosion resistance.

[Sequimite]

I may buy this Mule, and it will feel so right, so fulfilling.

But the next morning, will I awake filled with regret, look over at the Cobalt Special lying next to me and think, who is this steel?

[richroemer]

Guess i'll just have to buy one and find out for myself what it's like!
That's why it's called a mule?
(Need a mule faced smilie, going Hee Haw!)

[dj moonbat]

Takefu makes VG-10, too, don't they? Which is a cobalt steel. So figure Cobalt Special shares some characteristics of VG-10.

[Chris_H]

I'll take a WAG and say that it will be a steel with edge retention potential above VG-10 or N690Co, but with equivalent corrosion resistance.

Perhaps it is something along the lines of a Japanese version of BG42?

[Sequimite]

I'll take a WAG and say that it will be a steel with edge retention potential above VG-10 or N690Co, but with equivalent corrosion resistance.

Perhaps it is something along the lines of a Japanese version of BG42?

I agree with Paul that they would not encase Cobalt Special in stainless steel unless it served a practical function. CS must be brittle or prone to corrosion.

[Sequimite]

Finally found something. This is a post from the Falkniven forum:

About the new Cobalt steel.

Eric said it's holding an edge better than VG-10,but not all the way up to 3G,wich still is the best steel FK knows of.

It's closer though,to 3G rather than to VG-10.
As the Cobalt steel isn't a powdersteel,it's possible to keep the cost closer to VG-10.

So,the Idea with Cobalt steel seems to be performance close to 3G at quotes closer to VG-10!

Mikael

That's Falkniven's Eric not "ours".

[phillipsted]

I agree with Paul that they would not encase Cobalt Special in stainless steel unless it served a practical function. CS must be brittle or prone to corrosion.

This was the case with the laminated ZDP-189 they used successfully on the Caly Jr. and others. Correct me if I'm wrong, but that "sandwich" counteracted the tendency of the ZDP to be brittle while still allowing the blade to have a fantastic edge.

TedP

[jzmtl]

I thought the reason they used laminated zdp on caly is because the maker can't cut solid zdp?

[Michael Janich]

Why should you care? Because it's a Spyderco, because it's a Mule Team blade, and because it provides another unique opportunity to assess steel performance through the platform offered by the Mule project.

As for the specifics of the steel, here is a list of the alloys in the steel and the percentages of each:

Carbon: 0.95 - 1.15%
Chromium: 15.00-17.00%
Cobalt: 2.00-3.00%
Manganese: 0.30-0.50%
Molybdenum: 1.00-2.00%
Nickel: 0.25%
Phosphorus: 0.03
Silicon: 0.60-0.70%
Sulfur: 0.01%
Tungsten: 0.20-0.30%
Vanadium: 0.20-0.30%

The most notable element, as the name implies, is cobalt. For comparison, standard VG-10 contains 1.30-1.50% cobalt, N690Co contains 1.50%, and CPM-S110V contains 2.5%. At 2.00-3.00% cobalt, Cobalt Special will offer more of the qualities this alloy provides, specifically increases in strength and hardness and the ability to quench at higher temperatures. Cobalt also acts as a catalyst to intensify the benefits of other alloys.

As far as stain resistance, at 15.00-17.00% chromium, it is well above the threshold of a stainless steel and contains more chromium than VG-10's 14.50-15.50%.

The MT09 Mule will feature Cobalt Special steel "clad" between layers of SUS420J. 420J has minimal carbon (0.15%) and 12-14% chromium. This "san mai" (three-layer) construction provides great strength because the outer layers provide support for the hard core. When ground to an edge, a lamination line will be visible at the boundary between the outer layers and the core.

Part of the challenge of providing information on this steel is that very little information is available on it in English. Takefu's own web site does not include it in their list of steels. Hopefully, this information will help fill in some of the blanks.

Stay safe,

Mike

[bh49]

Mike,
Thank you. Can you give us rough idea about hardness, please

[JacksonKnives]

Good to see the composition numbers; this looks more like zdp-189 than, say, m42 in terms of alloy complexity. Lots going on that probably won't behave exactly as expected.

Ripe for testing, in other words! ^_^

[dj moonbat]

I agree with Paul that they would not encase Cobalt Special in stainless steel unless it served a practical function. CS must be brittle or prone to corrosion.

Not necessarily. It might just be a lot cheaper than making the whole blank out of the really fancy stuff, when the edge is where it's really needed. Lots of Japanese kitchen knives clad VG-10 in other steels, even though VG-10 has little need for outer layers to address corrosion or brittleness.

[2cha]

I think it's like with the Fallkniven knives--mimics the effects of differential heat treatment that are difficult or impossible the accomplish with modern stainless steels. The outer layers of the 420J are much softer than the more brittle core this paradoxically makes the blade stronger by allowing it to flex where and when it needs to. Fallkniven laminated blades were subjected to incredible testing--beating out all but the Busse infi steel blades--delaminating only after being beaten across the flats with a heavy sledge repeatedly. The advantage the cobalt gives is near absolute rust resistance. I can attest to the rust resistance after using a Boye cobalt knife for salt water related activities until I bought a pac salt last year. Absolutely no corrosion. I never badly stressed the cobalt blade, so I don't know how brittle it is. I do have a fallkniven laminated blade, but I've never abused mine personally, but I can say with assurance that the 420J outer layers take a high polish easily.

[Sequimite]

Not necessarily. It might just be a lot cheaper than making the whole blank out of the really fancy stuff, when the edge is where it's really needed. Lots of Japanese kitchen knives clad VG-10 in other steels, even though VG-10 has little need for outer layers to address corrosion or brittleness.

Good point, but I can't imagine Sal doing that.

[dj moonbat]

Good point, but I can't imagine Sal doing that.

I think Spyderco purchases the blanks already rolled out from Takefu. They aren't likely laminating their own steel.

[Sequimite]

I think Spyderco purchases the blanks already rolled out from Takefu. They aren't likely laminating their own steel.

My thinking is:
1) Spyderco hasn't done this before, in fact they have done the opposite with ZDP.
2) Mule steel is often referred to by Sal as being special small batches. I'm sure there are some exceptions.
3) The small size of the Mule minimizes the amount of money that could be saved. Obviously huge runs of larger kitchen knives has a very different economic incentive.

So it would be unprecedented for Spyderco to use clad blades to save money.

Doesn't mean it couldn't happen, but it would be surprising.

add: well I'm surprised

[sal]

Hi Sequimite,

We really don't know much about it. It's one of those odd steels that is supposed to be special. No one has played with it yet. I trust Takefu to do it right. It is also challenging to get these foundries to play with us.

I am guessing that the reason it's clad is to save money. The alloy is most likely quite expensive to proeduce. The Japanese foundries cut a channel into into the edge of the "laminate" steel and place the special steel in the channel.

The sample that I've been testing for the past few months has been impressive.

With the Mule team, we all get to try a piece of this special stuff and come to our own conclusions. What's better than that?

sal