CPM 3V questions...

Mongo

Mongo

Joined
Nov 5, 2001
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MicroAlign's thread made me think and do a little searching... I don't know much about this steel. Does it have another name? (an annoying thing with some steels) Am I correct that it is a forgeable steel? What are it's strong points, it's weak points?
Educate me please...
Mongo
 
The only one I have seen forged is by Bailey Bradshaw and it was a BEAUTY!

CPM-3V is all about toughness and impact strength. Great for heavy use fixed blades and overkill on small utility knives and folders IMO. I have a Pathfinder in 3V from RJ Martin and it is the toughest damn knife I've ever seen. I chopped with it extensively last summer and never could tell it had done a thing. It is definitely not an easy maintenance steel, it will rust badly from what I here but I have not left mine wet or uncared for and have had no problems. I am currently having a tough, hard use fixed blade in the 7" range made and it was no mistake that I chose it to be in 3V.
 
Originally posted by blademan 13
The only one I have seen forged is by Bailey Bradshaw and it was a BEAUTY!
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Yep, it sure was....

orig.jpg


Cheers,

Roger
 
Roger:
Had a chance at that one in Reno.Snoozed.Bad news on my part.:(
Beautiful piece.
Randy
 
Ahhh...wonderful CPM3V. It is one of my two favorite steels of all time. To me, it's only drawback is that it is diffucult to work.

As for good points, it holds an edge wonderfully well. Better than any of the carbon steels I have used, with only triple marquenched and cryo treated 52100 rivaling it in my tests. You have to do A LOT of cutting to tell a difference. It is also extremely tough. It is by far more durable than ANY stainless steel going, even it's stainless "twin" S30V. Again, only 52100 comes close in my tests. (1084, L-6, 15n20 were also tested)

I think it got an undeserved reputation for rusting. I have carried one of my working folders with 3v for almost four years, and have only one or two very small dots on the blade. This is in Texas summer heat with probably a gallon of sweat poured over it. I spoke with Ed Severenson of Crucible a few years ago about the composition of 3v, and why I found it more stain resistant than D-2. 3V has only 7 points of chrome, but also has 3 points of vanadium. Chrome adds three qualities in the correct amount. Increased hardenability, stain resistance, and carbide formation. Most stainless steels have 12-17 points of chrome, and the mixture generally relies on this amount to perform all three tasks. The problem with this large percentage is it decreases toughness, which is why stainless steels tend to be brittle when hard enough to hold an edge well. 3V, with only 7 points chrome relies on the chrome for hardenability and stain resistance only. The vanadium in the steel mix forms carbide faster than the chromium, so essentially all of the chrome is left for stain resistance. This is actually a higher percentage than many steels with 12-13 points, like D-2 which uses chrome to form carbides as well.

The high degree of toughness in 3v is partially due to the vanadium's other task of grain refinement. Fine grain gives more surface area in terms of grain boundries. It's like glueing large wood chips together as in particle board as opposed to wood powder like MDF is made from. The MDF is much tougher than particle board.

Last, many feel 3V is only suitable for large blades due to it's toughness. While it does make a great chopper, why not get the same high degree of toughness in a nice thin pocket knife blade. The tougher the steel, the thinner you can go, the easier it is to carry, better cutting geometry, and easier to sharpen ( less metal at the edge bevel to remove if you grind to a thin edge). This is why I selected 3V for my Whitewing line of folders I did a couple of years ago. The project never made it like I had hoped, but talk to some of the Whitewing knife owners and see how they like 3V in a pocket knife.

Hope this answers your questions, and hope I didn't ramble too much
 
Dangit Bailey, I've already changed the Laredo I have on order from S30V, to 3V, and back to S30V. Now you've got me wanting to change BACK to 3V :D
 
Originally posted by Bailey Bradshaw

Last, many feel 3V is only suitable for large blades due to it's toughness. While it does make a great chopper, why not get the same high degree of toughness in a nice thin pocket knife blade. The tougher the steel, the thinner you can go, the easier it is to carry, better cutting geometry, and easier to sharpen ( less metal at the edge bevel to remove if you grind to a thin edge).
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Point well taken Bailey.

Nice to hear your reports on rust issues. Like I said, I have'nt had any problems with mine, but then again, it was always lurking in the back of my mind. Thanks.
 
Bailey Bradshaw :

I think it got an undeserved reputation for rusting.
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Mainly because its first big push was made by custom makers used to using ATS-34. CPM-3V will take surface rust a lot sooner than ATS-34 (or similar steels). However in extended salt water soaks it doesn't pit deeply, nor in general suffer functional damage. I have done repeated 12 h, and 24 hour soaks and after giving the blade a quick wipedown with a worn scotchbrite pad you would be hard pressed to tell the before and after pictures from each other.

In the same light though, the toughness of CPM-3V has been vastly overhyped because it was usually compared to the same steels and making such a comparison it comes off as very tough and ductile so it got a reputation as a super tough steel when in fact if you compare the toughness of CPM-3V with steels like L6, 5160, etc., it doesn't stand out and there are steels that are much tougher still, 50% or more.

It is also mainly uniformly hardened and thus comparing the overall durability with a spring tempered carbon tool steel blade the CPM-3V one will not fare as well. But when looking at air hardening steels, especially those with a decent amount of wear resitance, CPM-3V does well, but then again wear resistance is often highly overrated *especially* for large heavy knives of which it is usually of no use and often just a hinderance if anything because it comes with the price of lower machinability.

-Cliff
 
Cliff,

I think that 3V is a more well rounded steel than any of the steels you mentioned, hence it's popularity. Wear resistance is a big factor IMO, unless you enjoy sharpening your tool after every use.

L-6 is tough, but not quite as tough as 3V with much less wear resistance. I think that when comparing 3V to other big knife steels, there is no comparison right now. A good 52100 blade may come close in overall performance, but 5160 won't and neither will A-2, L-6, O-1 etc.

As an overall steel with good wear resistance and toughness 3V is more well rounded than most.
 
Cobalt :

Wear resistance is a big factor IMO, unless you enjoy sharpening your tool after every use.
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It depends on what you use the knife to cut, blunting can almost ignore wear resistance on a lot of materials and instead be dominated by hardness, impact toughness and ductility. This is usually the case for large chopping knives where resharpening is usually needed after mishaps. Wear resistance can be of benefit on utility knives which tend to cut more abrasive material.

Will CPM-3V make a quality large chopping knife, yes it would based on what I have seen of it, it has a high ductility and takes pretty severe impacts to fracture it on thin profiles. Here is a shot of a 3V blade (10 degree edge) used to attempt to cut a Cr-V screwdriver shank in half with the aid of a Estwing hammer :

http://www.physics.mun.ca/~sstamp/images/3v_edge_impact.jpg

The steel clearly fractured, but also took severe deformation before it did. This is also very thin for a tactical knife, if it was beefed up to a 15 degree edge, with a 0.025" thick primary leading bevel I would estimate *far* less damage, and would not bet against the damage being restrained to the edge grind.

My main points are simply that :

a) 3V is only considered *super* tough when compared to brittle steels, there are lots of cutlery steels that are just as tough or even more so and it is very rare to cause them to fail by direct fracture when heat treated directly. Here is a shot of an HI khukuri (5160, ~15 degree edge) after being chopped heavily into an iron chain :

http://www.physics.mun.ca/~sstamp/images/chain_ak.jpg

You can see the edge damage is mimimal on the khukuri, and only really visible towards the tip where they drop the hardness down significantly. Also check out Ray Kirk's 52100 blade after the heavy impacts on concrete :

http://www.physics.mun.ca/~sstamp/images/rk_bowie_light_concrete_chop.jpg

It is difficult to even see where the edge impacted and this was on a fine edged bowie. Note Ray leaves the edge significantly under 60 HRC to get a higher level of toughness and ductility.

b) wear resistance can often be of no benefit on a large chopping blade and can in fact be a detriment by increasing sharpening times after heavy accidently impacts


... neither will A-2, L-6,
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These steels are not even in the same clas, L6 has 4 times the notch toughness of A2 and is *much* more ductile (See Bryson for example). A2 is only considered a tough steel by those that use *very* brittle steels like the pseudo-stainless cutlery grades of ATS-34 and company.

-Cliff
 
Cliff,

I hate to interupt here but I would like you to please clarify your last post. 3v was cutting hardened tool steel, 5160 was cutting soft iron chain, and 52100 was cutting concrete of unknown hardness. Right?

My question is, how can you draw any comparison under those conditions? :confused:

Tom
 
Those examples were simply cases of various blades in extreme use senarios, they were not done with all blades mainly because they were not all in possession at the same time. The point made was that various tool steels like 5160 and 52100 (and there are a lot more) when heat treated so as to generate high toughness will allow the blade to suffer minimal damage in extreme cases, as they deform rather than suffer direct fracture. Quite frankly there are not a lot of people complaining that steels like L6 and 5160 are fragile in large blades so having a tougher steel would not seem to be of direct benefit, there are already many in existance anyway.

For such cases as cited having higher impact toughness would be of little or no benefit as it was already high enough so as to not be the limiting performance and wear resistance is of no consequence at all. If you wanted to make direct steel comparions such as concluding 3V was functionly tougher than 5160 you would cut with similar edges on progressively harder to cut material and see which one failed first, or allowed a thinner edge without failure. The 3V blade has indeed been used to cut concrete and suffered a similar type of damage as the 52100 blade, but more extensive mainly because the edge angle is much more acute.

3V does have an advantage in that it is air hardening whereas L6 and 5160 tend to be oil (or water hardening) and use differential hardness (spring spines) to maximize overall durability (when done they are then several times more ductile and tougher than 3V), however steels like A8 (Tom Johanning) are also air hardening and are extremely tough and ductile.

-Cliff
 
Cliff, I'm confused about the relative toughness of the steels. I went to Crucible's site and found the following information (Charpy C-Notch ft-lbs)

125 ft-lbs S7 at HRC 57
70 ft-lbs 3V at HRC 60
68 ft-lbs L6 (Champaloy) at HRC 56-58
40 ft-lbs A2 at HRC 60
30 ft-lbs O1 at HRC 60
26 ft-lbs S30V at HRC ??
21 ft-lbs D2 at HRC 60
19 ft-lbs S90V at HRC 59
16 ft-lbs 440C at HRC 58

I'm having trouble reconciling these numbers with the relative performance characterizations you've given. For example "L6 has 4 times the notch toughness of A2."

Thanks, Gabe
 
Cliff,

I must disagree with you on a couple points, or at least clarify some of them so I know we are on the same page.

The first is the comparison of 5160 to 3V. I know for a fact 3V will take far more abuse at a much higher (much higher to me is four or five points on the RC scale) rockwell than 5160. I define toughness as the ability to withstand abuse with little or no fracture OR deformation. If a steel deforms where others do not, I define this as more malleable. L-6 is a better performer for me than 5160, but still falls shy of 3v. My L-6 edges tend to roll before the 3v edges.

In recent cutting competitions, the only blades that I have witensses fail due to wrinckled or rolled edges were made from 5160.

A differentially heat treated blade is a whole different animal. The spine of the knife may be more springy, but the blade is not necessarily tougher overall. There are so many factors at play here it is hard to make such a statement. We do the bend test on our knives, and while the criteria to pass the test is to not have a blade that breaks, there are many blades that do more than just withstand being bent 90 degrees without breaking. John Fitch made a few bainite tempered D-2 blades, and one withsood several 90 degree bends back and forth before it broke. My MS test knife sprang back to about 15 degrees over the length of the blade. Both John and Pete Peterson witnessed me bend a 4" pocket knife blade made from 3v just past 90 degrees before it broke in two. It was at rockwell 60 throughout. Had I drawn the spine with a torch, it probably wouldn't have broken at all.

The best way to compare steels is to compare them at a hardness and cross section that best suits that particular steel for the intended purpose. When I have done this, 3v offers the superior balance of all the qualities a high performance knife needs.
 
A steels impact toughness is a direct relation to its alloy content and the make-up of its microstructure. Hardness, alloy content, microstructure including the presence of carbides all play a part. The type, volume, size and orientation of the carbides also contribute. When you look at published impact numbers you are getting ballpark numbers that can vary for all of the above reasons and that doesn't include the heat treat factor. The D2 example with good ductility is a direct function of the carbides being finer and more evenly dispersed in thin blade size sections. Cut a blade from a 2 inch plate and the toughess will drop considerably. The PM steels are unique in that the process forms very fine homogenous carbide structures. Make 3V conventionally and it won't be as tough as A2 in impact tests. Make it PM and it's at the top of the impact toughness chart for tool steels.
 
I must admit that I sometimes have trouble with the "all purpose knife". While I can certainly understand the purpose of bladesmith test knives. I don't always see a practical use for such knives other than showing the metalurgical knowledge of the maker. The days of mounting your horse and riding off into the wilderness are long gone and the universal knife is not needed except for the fun of it.
I personally want a 4" hunter made of pretty good steel for cutting (O-1 would probably do but what would be the fun in that). If I thought I might need to chop something I would want a machete, Kukri or hatchet made of some high impact steel (1080 would probably do but again what would be the fun in that). IMHO the new steels like 3V allow me to make a 4" hunter much thinner and lighter while having the same strength and with an edge that lasts. With CPM 3V and 30V steels you can get big blade performance out of an 1/8" piece of steel.

In tactical knives KaBar has been using 1095 and Randal has been using O-1 with great sucess for decades. Their knives are war proven yet these steels have a poor showing on all of the charts. New steels like 3V allow this same or better performance with lighter weight.
If you look at a knife as first an formost a cutting and stabbing instrument that may have to make an occasional chop 3V makes a much better showing. However if you look at a knife as a chopping instrument that may have to cut once in awhile then steels like L6 and S7 make more sense but, IMHO a much poorer knife. Sort of an elongated axe.

Tom :)
 
I am tying up loose ends. This has been an interesting thread, but I am leaving this forum until searching is re-enabled for basic members.
 
Tom,

No more ridding my horse off into the wilderness:confused:

My horse probably won't mind, but I kind of like to do it.

I do occationaly ride on my land, and have found it invaluable to have a good sized knife for cutting trails and keeping trails clear. I carry one of my Tejas models, and have found it to be quite a usefull tool. I have cleared shooting lanes for a deer stand, cut the wings off 30+ geese (tough wing bones) and numerous other chores at different times. As for an all-around knife, I have grown to appreciate them. Big enough to do heavy work, but light and nimble enough to serve any function short of caping a trophy. It replaces a small axe, huning knife, and machete in my pack.

Mine is L-6, but I will probably forge one from 3V just for kicks. I know I don't need to forge it, but the bar I have is way too thick, and not wide enough, so forging it to shape makes sense here.
 
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