Toughest steel

Depends. Define "toughness".

Heat treat method, hardness, grind, and thickness will all influence toughness.

Properly heat treated, 5160 should come out ahead.

David
 
Impact toughness?

Probably something in the "Silicon" series, like S7 (think jackhammer bits).
 
CPM-1V has about twice the impact toughness of S7, and is hardenable to Rc59-60. Actually it can be hardened to Rc62, but at Rc59-60 it's extremely tough. (Think sword blades.. :) )
 
Try again....tough = 4340.... for knives then look to the big boy custom makers.
 
You said 1V has almost twice the impact resistance as S-7. What hardness and prior austenitizing temp of the S-7 and 1V are we talking about? S-7 takes a dive in Charpy C-notch ratings after HRC57 because that is not at its optimum hardness/toughness rating for its intended purpose. Especially anywhere above 59HRC. This is with an aus temp of 1725/1750, 30/45 min soak.:confused:
 
Steel is inherently characteristic of no exact preset strength or toughness ratings. That is why metallurgy is a science. It's not that simple. There is no "toughest" steel.
 
Epsilon, your last statement is indeed true. Some formulas however make achieving acceptable toughness easier. CPM-1V is austenitized at 1950-2000, and tempered at 1000-1025 for 2 hours, twice. Hardness should be Rc58/59. Maximum impact toughness is at Rc57-59. No mention is made of cryo quench, which should improve it further. S7 was hardened at 1725. I don't have the temper number or hardness for S7, but these are the comparative numbers from Crucible Steel. Likely it was 400-500 and Rc 54-56
 
Jerry Hossom :

[impact toughness]

No mention is made of cryo quench, which should improve it further.
Click to expand...

From what I have read, the best that deep cryo has been able to do is not decrease the impact toughness. It is well known to increase the stress/strain toughness, but that is a very different property. However I have not actually done a journal search lately and more research is being done all the time.

For reference, S7 is about 50% tougher, impact wise, than 3V with both at ~57 RC. Interesting comments on CPM-1V, at that high a hardness, with that high an impact toughness it would make a very interesting hard use steel.


-Cliff
 
Indeed, I had not heard of CPM-1V until this thread... so thanks to Jerry on this one.

I hadn't seen 1V mentioned in what condensed literature I have from Crucible.

If anybody has the alloy makeup, would like to add that to my alloy spreadsheet.

Thanks.
 
Carbon 0.55%
Chromium 4.5%
Vanadium 1.0%
Tungsten 2.15%
Molybdenum 2.75%

I have been sawing on a piece of 1V for some weeks now, a little each day. It is the first steel I've ever handled that is dramatically more difficult to saw than other steels I've used. Grinding is not going to be any fun at all. Unfortunately 1V is not available in thicknesses required by knifemakers, the thinnest piece I've found is 1.5" thick. What I have is a 1/4" thick piece sliced from that, making it hideously expensive to use.
 
Note that CPM 1V, at .55% Carbon, is a medium-carbon steel and still highly regarded. And that HT is known to do more than harden the alloy.
 
Originally posted by Jerry Hossom
I have been sawing on a piece of 1V for some weeks now, a little each day. Unfortunately 1V is not available in thicknesses required by knifemakers, the thinnest piece I've found is 1.5" thick. What I have is a 1/4" thick piece sliced from that, making it hideously expensive to use.
Click to expand...

:D

Now that, folks, is true dedication to furthering the range of materials available for one engaging in stock removal.
 
Originally posted by samwereb
Note that CPM 1V, at .55% Carbon, is a medium-carbon steel and still highly regarded. And that HT is known to do more than harden the alloy
Click to expand...
...

...ok... I think I've with you so far ... keep going ...
 
For the record, the 1/4" slice was not done by me, but was done commercially. I'm taking forever just sawing the 1/4" material that resulted from that.

I think Sam's referring to the fact that you really can't draw many conclusions by just looking at the numbers. Some might suggest that a steel with only 0.55% carbon could never be as hard as 1V is able to get, as high as Rc62. The CPM process really does change a lot of the rules. By eliminating carbide segregation among other things, a lot of what was/is thought about high alloy steels has to be revisited.
 
Hi, RD and Jerry.

A argument roils in another forum that medium-carbon, low-alloy steels are junk. I had the silly idea that some of the participants might look in here. I didn't mean to preach to the choir. Or the deacons, for that matter.
 
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