Fairly new super steel from Crucible…anyone hear about it?

McClellan Made Blades

Well-Known Member
I was at the. Cutting Competition year before last, when Dan Kefflar
was crowned. WORLD CHAMPION, after the competiton was over there
was a demo of a new steel, I think it was called Rex121 or something like that,
the most amazing thing about this steel is that it would HT to a Rc of 70!
Yes, that was a 7 and an 0 side by side as in 70Rc! With NO CHIPPING, cracks
Etc. Matter of fact the demo was cleaving huge cans of corn in half top to
Bottom! I just want to know if anyone has heard of it, know if its being offered yet,
Or if it will be offered for sale. THANKS Rex
 
Wouldn't like to forge that stuff. It would just lay there and laugh at you. It will probably go through belts like crazy too.

Doug
 
A man across the big pond named Farid makes knives from Rex 121. I've seen videos, and they are pretty amazing. I would love to try some. Farid will sell chunks of it occasionally. It's the only time I've seen it for sale.


Typical Chemistry (Patent Pending)
Carbon 3.4% :what!:
Tungsten 10.0%
Chromium 4.0%
Molybdenum 5.0%
Vanadium 9.5%
Cobalt 9.0%
Sulfur 0.03% (0.12%)*
 
I recent ground two knives out of CPM-110V and that stuff is a bear to grind and really did laugh at finishing belts.

This REX steel looks like even more of a challenge.
 
Hi Guys, actually 70Hrc means nothing than that it has the hardness of 70Hrc ( i had 2519 blades that reached also 69-70 Hrc). This is not enough to say that the steel is superior cutting material.
The alloy is a High Speed Steel, with that amount of Carbon, Tungsteen and Cobalt for the bond, i doubt it is suitable for fine knife edges.
I tried other similar HSS alloys for knifes and they were different to heat treat, hard to work, difficult to sharpen and damned brittle.
...but at least it is always fun trying new steels and have fun while working is always a good thing to make good knifes!
 
Hi Guys, actually 70Hrc means nothing than that it has the hardness of 70Hrc ( i had 2519 blades that reached also 69-70 Hrc). This is not enough to say that the steel is superior cutting material.
The alloy is a High Speed Steel, with that amount of Carbon, Tungsteen and Cobalt for the bond, i doubt it is suitable for fine knife edges.
I tried other similar HSS alloys for knifes and they were different to heat treat, hard to work, difficult to sharpen and damned brittle.
...but at least it is always fun trying new steels and have fun while working is always a good thing to make good knifes!


The reason I am interested in this steel is because it DOES heat treat to a Rc of 70 and DOES maintain an edge, and with the demo I saw at BLADE in 2013
after the World Championship Cutting Competition, the guy that did the demo CHOPPED a large can of corn (a steel can) the proceeded to cut another, after that he
cut a few more items and did some fine cuts too, my memory fails me, I'd have to ask my son if he remembers everything that was done, but this steel IS a SUPER STEEL!
Now as for the ease of sharpening, I DON'T KNOW, which is why I want to find out, it may be useless, but then again, it may be phenomenal! Which is why I asked.
And partly due to what you said, it is fun working with new steel! Thanks for the response, Rex
 
Not having any experience with that stuff, and just going by the numbers....it is going to be very difficult to sharpen. With THAT much carbon, THAT much W, and THAT much V, I couldn't imagine the carbides in that steel! Probably not able to take a very super keen edge simply due to the carbide presence, but once that edge is there.....I bet it doesn't go ANYWHERE for a long time! I always think about being in a situation where you are on the top of a mountain trying to gut, skin, and quarter a bull elk, and you're knife goes dull half way thru the job. Is your steel going to respond well to quick touch ups? That is why I like AEB-L for stainless so well. There are basically NO carbides present, as there is only .7% carbon, and all the Cr is free to act as corrosion resistance. While not coming close to being able to hold an edge as some of these exotic tool steels and high speed steels, the edge AEBL and lower alloy carbon/tool steels can obtain is a bit sharper, and can be touched up in literally seconds with a small pocket stone. Just personal preference, tho, as always. I would have to do some testing with a new steel like that to see if it would serve me well in a given situation. I guess to sum up my steel preferences....I like fine grained steels that have little carbide formation. Keep the Mn, V, and W fairly low and carbon right around 1% - 1.2%. Would love to get my hands on some of the Rex steel, tho, and see what it is capable of!!!!
 
I've sent an email off to our crucible steel rep on this.
 
A man across the big pond named Farid makes knives from Rex 121. I've seen videos, and they are pretty amazing. I would love to try some. Farid will sell chunks of it occasionally. It's the only time I've seen it for sale.


Typical Chemistry (Patent Pending)
Carbon 3.4% :what!:
Tungsten 10.0%
Chromium 4.0%
Molybdenum 5.0%
Vanadium 9.5%
Cobalt 9.0%
Sulfur 0.03% (0.12%)*

I too, have seen some of the knives he's made, they look pretty good, although I haven't seen any of his video's,
the only knowledge I have of it is the demo that I saw at the BLADE SHOW. THAT was AWESOME I wanted to see what it would be like
in a smaller blade, see how the edge would hold up for primarily cutting soft material.
Now if he's selling chunks of it, that means I'd have to forge it, there is no way I would attempt that without a press and a surface grinder!
Rex
 
an answer from my steel guy:
CPM Rex 121 is not new…in fact it is an old grade that was developed for Gear Cutting Hobs for the automotive industry. It is an extremely hard to work with High Speed Steel which was designed not to temper back during high heat metal cutting applications like gear cutting. It is not designed for knives and would be very brittle. ....The price is extremely high.
 
I've got one of Farid's Mule blades in Rex 121. Sharpens up easily enough with diamond hones, won't take as fine an edge as less alloyed steel but will hold an aggressive edge for quite a while. Renovating the house it cut up rolls of carpet, dozens of cardboard boxes, opened bags of sand and plaster and didnt suffer.
It's not laser sharp but keeps a working edge happily and I don't feel like I have to worry about hurting it.

I bought it to try the steel, but I wouldn't have a custom made from it.
 
...
Yes, that was a 7 and an 0 side by side as in 70Rc! With NO CHIPPING, cracks
Etc. Matter of fact the demo was cleaving huge cans of corn in half top to
Bottom!

Credit has to be given to people like Farid for working with new materials and seeing how they work for knives. However when we see demonstrations like that we always have to ask is what we are seeing due to the steel or something else? People who have used the knife Farid demonstrated with have noted that the edge was so heavy that it bounced off of wood when they tried to cut with it. If you don't clearly know the geometry it is hard to say if the strength/toughness is due to the steel or just the shape.

I have used 121REX and it is a fairly expected step up from steels like 10V. It is harder, more wear resistant - and at the same time has lower toughness and edge stability. The curious thing about it is that the edge doesn't tend to stay sharp as in keep a very narrow apex, but it resists (in light cutting) any deformation of the apex. If you take it for example and something like ATS-34 and cut up cardboard, from what I have seen, the 121REX blade would look to have stayed sharper if you look at the apex as it won't reflect light but the ATS-34 one does in those small spots that blades pick up as they dull. But the curious part is the ATS-34 blade will actually cut better. It looks like the 121 REX blade wears to a more even apex.

I think what is happening is that it micro-chips at a fine level until the apex is thick enough so that it won't chip any more and then it enters into the process of very slow wear (due to the high carbide). It thus ends up with an apex of < 20 microns wide (can't see it) but which is fairly dull. If you compare this to something like ATS-34 at the normal 60/62 HRC range then parts of the apex are > 20 microns wide (you can see it) but parts of it are not and they cut well and it is also a more jagged type of apex so it can still slice. Most of this is just hypothesis as you need a SEM to actually know any of it. But I have done the same type of work on cardboard, ropes, carpet and just general use and it always does the same thing.

But this means if you are doing something like cutting carrots or peeling potato which doesn't need a super sharp edge, then the ability of 121REX would like be extremely impressive, which would explain why some people really like it for certain types of work as the apex will resist growing over > 20 microns strongly.

As an aside, I have ground it with simple abrasives, even basic waterstones - it just takes time. But ideally you want sharp and modern abrasives to cut it efficiently.
 
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