What's up with 440C

stjames :

[dendritic cobalt]

Nice grippy cutting edge with that stuff!
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David Boye's dendritic blade materials have a reputation for high cutting ability, but consider that he recommends putting a coarse finish on the blades when sharpening (600 grit diamond was one of the suggestions). All blade materials will make a huge jump in performance in regards to slicing if you lower the grit finish from the usually buffed NIB edge to a coarser one. As well, Boye grinds some of the highest performing blades out there because of the edge geometry he uses (knife is about 0.01" or less behind the edge, which is ground at a decently acute angle). Basically, the cutting ability that is commonly praised is due to the geometry and the edge finish, not the materials used.

In regards to that specific material I found it vastly inferior to his dendritic 440C in regards to edge strength and overall durability. Even in something as low stress as cutting cardboard the dendritic Cobalt fell apart much faster than the 440C. Now I am not talking about a few cuts and the edge is gone, but after a lot of cutting (1000's of cm) I found that the edge would break apart at the 0.1 - 0.2 mm level and thus produce fractures about 1-2 mm long along the edge. Thus when you went to sharpen the blade it would take much more time because you have to grind out these fractures if you want a smooth cutting surface. Compare this to the dendritic 440C which just wears down. Note dendritic Cobalt is just cast Stellite 6, which is far softer, weaker and more brittle than the other two common cobalt knife alloys Stellite 6K (higher carbon content, work hardened) and Talonite (precipitation hardened).

James :

440C has good carbon content and very high chromium which would account fo its stain resistance.
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You want a low carbon content to get corrosion resistance, or more importanly a high Cr : C ratio as Carbon will lock up 17 times its own weight in Cr carbides. This is why the 440 A/B steels are far more corrosion resistant that 440C. Other ways to increase corrosion resistance are to use elements that are stronger carbide formers (Vanadium) , or those that directly help the formation of the Cr oxide layer which is what prevents corroions (Molybdenum).

In regards to protecting your blades with oil or whatever, if you are going to take that kind of care of them then disregard the stainless steels and look at a high performance alloy steels.


-Cliff
 
I have been using a Benchmade 551 for a little while now. It is 440C. I have gotten very good performance from it. It may not hold an edge as long but the edge came back easier than my experience with ATS-34. I think 440C is a good steel. As noted above it just isn't the latest steel in the steel of the week club.

I will say that it is my experience that heat treat and edge geometry are more important than which steel is used.
 
For the record, SOG uses AUS-6, not 440-A. yes, I know it says that in their advertising. Well, it USED to say that actually! There was a thread about this a while ago. I just wanted to clear that up. SOG uses the AUS line a lot, and never 440-A.

They also use BG-42!
 
The first knife I made has a 440C full tang blade and it has served me well for over 20 years. Many moose, caribou, bear,and deer have been butchered with this knife. I would have to touch it up once or twice for a big moose but it is easy to sharpen and is rust resistant. It also doesn't seem to chip when bones are hit. I think it's overlooked because of the new super steel.
 
Hi folks,
My experience with 440c steel is very good, it's easy to work and finish, heat treatement isn't difficult too, although new steel like S30V, S60V, BG42...... are better for folders 440C is a good choice for general knives, you can make a small skinner or large bowie with this steel, you can satin finish or mirror polish the blade without problems, in a nut shell, it's very versatil steel.
If you have conditions to make a sub-zero quenching, you have excellent results, in my tests, a 440C blade with sub-zero out performed a ATS34 blade.
 
Personally i do not like 440A/B/C, maybe if it was alot cheaper, but price wise it is only slightly cheaper than 154CM, with 440C being 1/8” x 1-1/2” x 1' = $8.00 and 154CM being 1/8” x 1-1/2” x 1'= $9.25, That said i would pay the extra 1.25 a foot and go for the better performing 154, prices ripped from TKS. It doesnt hold a edge near as well and its only marginally cheaper(10 cents a inch cheaper) i dont understand why people still use it, especially with the new steels out there, such as S30V.
 
When I lived in Japan, a maker of Japanese swords told me that they never use oil on their blades because oil will eventually discolor the blade. At his advise I use baby powder on all my blades. I have a number of custom FB's that I have had since '85-'86 that have been stored in their leather sheaths(previously loaded with baby powder) since that time. None have suffered even the slightest spot of rust. These blades are mostly 440C.
 
Back in the day when 154CM/ATS-34 was "the ultimate", 440C was the penultimate... 440C is, by most accounts a very good performing stainless steel with properties somewhat similar to GIN-1 or AUS10. (though 440C is a Crucible, american steel. while GIN-1 and AUS10 are japanese)
I've never had a 440C knife but i'd never be hesitant to buy one.
Nowadays the steel snobs will root for the new "exotics" as they are commonly called like: CPM440V, CPM420V, VG-10, BG-42, S30V, and so on and so fourth, I also like alot of the exotics and won't deny that they are indeed better, perhaps among the best. However 440C still is what it always was: a very GOOD steel, not great, not amazing or high-tech, just a good balance of that ole time alloy creation made in the good ole US of A. :P
 
I firmly believe that too many people have to have the latest and greatest whether they will ever know the difference or not. Over the years I have had many knives made from 440C and they have all been great. In certain areas it will not be as good as other steels, but it is an excellent all around steel. It is very corrosion resistant and polishes up to a great mirror finish. It takes a fine edge and holds it well.
 
No offense to anyone in particular (or in general, for that matter) but, I tend to believe that a lot of us have become steel snobs.

440C, imho, is a very underrated steel. It offers excellent rust resistance combined with good edge taking and holding properties. I've had many knives in 440C over the years, and I still have an old Buck 102 in 440C that's provided yeoman service since I was a kid. Recent purchases in 440C include a BM Griptilian and a BM Tether knife. I'll not hestitate to buy, use, or carry a knife in 440C from a company that knows how to temper it to maximize it's performance in cutlery.

Mike
 
It is my understanding that the degree to which a steel is "stainless" is a function of the percentage of chromium in that particular steel. Since 440C, 440A and ATS-34 all contain about the same amount of chromium (14.5%) I would suspect their resistance to staining/rust would be about the same.

I believe the CPM steels have a higher chromium content and therefore, in theory, would be more stain resistant.

I own several knives made from 440C and have always been impressed with its quality and performance as a blade steel.
 
My views could be construed to be a part of the steel snob contingent. I think I bring some balance to the snobbery, and a mild disgust with "the latest fad" steel when presented in an unbalanced way. With those admissions up front, I continue...

Corrosion Resistance

With steels (and with non-ferrous alloys, as far as I know) the degree of corrosion resistance is generally correlated with overall chrome content, but that doesn't tell the whole story... there are too many exceptions in the 420, AUS, and CPM families. Corrosion resistance is strongly related to "free" chrome content.

Chrome is bound up into Chrome Carbide during the smelting process by the inclusion of Carbon in the mix (and of course carbon is what allows iron to become steel). This is a relatively good thing in moderation, since chrome carbide tends to run Rc60 and aids abrasion resistance somewhat.

I'm not a metallurgist, but I've worked with several in my line of work, and they all informed me, independently and over a 15 year time period, that corrosion resistance of a material is a function of the oxide layer that forms on the surface of any steel or other alloy... it is the oxide layer that prevents corrosion, not the underlying metal alloy per se. Chromium Oxide (Cr2O3) is the responsible party. So chrome must remain "free" from being bound up with other atoms (carbon notably) at the surface in order to oxidize in air. (If some metallurgist reads this and can get us closer to the truth, please chime in.) Just like iron turns to "rust" when it oxidizes to Iron Oxide (Fe2O3), Chromium oxidizes to Cr2O3. The difference is that Cr2O3 is a very tenacious, tough, and self healing oxide, whereas Iron Oxide is very brittle and flaky.

On point, here are a couple of threads that Google turned up:
http://www.mcwelding.com/morelinks/stainlesssteel.html
http://www.ssina.com/stainless/

As you use a knife, you wear off the Chromium Oxide, but it self-heals very rapidly if even small amounts of oxygen are present. (this is one reason that metals subjected simultaneously to both corrosive AND erosive mediums are worn and corroded away so quickly...erosion continuously scrubs off the Cr2O3, and the corrosive elements have a field day at the same time [especially if oxygen is not around to "self heal" in a liquid environment], competing with oxygen to react with the underlying alloy).

I'm not a diver, but would guess that a very heavily used dive knife would corrode pretty badly, as the chlorides in sea water would go after the underlying alloy pretty aggressively. Most dive knives are probably not that heavily used though...occasional prying and poking.

Knife materials

In developing 440V, Crucible started with 440C, i.e. a 17-18% chrome steel, to which they added a big dose of Vanadium (6%) and about double the carbon (2.15% vs. 0.95-1.2% for 440C) in making a more wear resistant stainless. Problem is 440V gets relatively brittle above Rc56, depending on who and how the heat treat is done, and despite the CPM steel's tendency to have a fine grain structure if handled correctly.

According to Crucible, 420V does notably exceed 440V in terms of corrosion resistance. Not sure I know why, but suspect that super high vanadium content (9% vs. 6%) in 420V causes much of the available carbon to bind with vanadium into Vanadium Carbide, and leaves more of the chrome available to remain "free" after carbide formation. 420V also is tougher at a given hardness, and it also is more wear resistant than 440V.

I've stated before that 440V is pretty much obsoleted by 420V. The reason 420V didn't replace 440V in the production houses and with some makers is that 420V requires a much higher austenizing temperature in heat treat (oven limitations) and is harder to put a nice finish on, and harder to grind in general, so only the more dedicated custom makers have tackled it.

Now with S30V on the scene, 440V has been theoretically AND practically obsoleted, due to S30V's tractability in heat treat, and improved toughess at a given hardness, and similar edge retention/edge wear characteristics. S30V can generally be run 4 Rockwell C points higher than 440V (due to superior toughness) so is going to make a better edge holder, and knife steel, overall. S30V's toughness can be run at least 2-3 Rockwell C points higher than 440C, generally conducive to edge holding (slicing, push cutting).

Example of 420V's corrosion resistance: I smeared fresh lemon juice all over a 420V blade and let it sit for 3 days. It did not corrode (no rust, no pitting), but it did discolor somewhat... it is a beadblasted blade, and in a couple spots, not all over the blade, the blade turned darker, to a light gray instead of silvery.

S30V contains 14% chrome, 4% vanadium, 2% molybdenum, along with 1.45% carbon. It is purported to have corrosion resistance on par with 440V and 440C. S30V exceeds 440C in all areas of performance save "ease of sharpening", an overrated trait IMHO, see below.

The low carbon 420J stuff doesn't bind up much chrome in carbide content so free chrome is available for corrosion resistance here also. Of course, 420J is a very mediocre (being kind) edge holder also. From memory (my Crucible handbook is packed up for moving), Crucible lists 420J as having twice the corrosion resistance as 440C (probably salt spray test). But for me, the tradeoff in edge holding is not worthwhile. I'm not sure how 440A would compare to 420J, probably pretty close in corrosion resistance. But 440A would exceed 440B and 440C in corrosion resistance for same reasons (more carbon around in 440B/C to bind up chrome in form of chrome carbide) with similar, inverse tradeoffs in edge holding. The 420HC stuff that Buck uses is an underrated steel also, and will be about as good as 440C in terms of corrosion.

Talonite and Stellite will be the most stain resistant, serviceable knife blade materials you can find since they are not steels, but are cobalt/chromium alloys (no iron, or well, very small amounts of iron). No iron means no "rust" or Iron Oxide. Generally, if you can put your hand in it, it won't bother Talonite/Stellite. Generally #2, you have to get into very low pH acids to corrode these CoCr alloys. These CoCr alloys run soft (Rc 42-48) compared with most blade steels (Rc 55-62), but are very abrasion resistant, so they make pretty good slicing knife blades (although edges tend to roll more easily, making the grind geometry more important than usual on these). Since they are relatively soft, I find the CoCr's to be very easy to sharpen especially with diamonds, and very responsive to steeling to realign the edge.

Titanium alloys can be excellent in terms of corrosion resistance, bending strength, strength-to-weight ratio, and toughness, but not in terms of being an edge holder for slicing chores (soft). They tend to underperform the CoCr's in this area, even at their hardest.

Bottom Line:
Nothing wrong with 440C. It is firmly "mid range" in terms of stainless cutlery steel in overall performance, and serves a purpose still. It is cost effective and relatively stain resistant, near the top of stain resistance for blades suitable for good cutting performance, and easy for most any maker to grind, heat treat and finish.

Other than price, or the desire for a fancy mirror finish on a "not to be used" display piece, I can't think of a single reason I'd choose 440C from a custom maker now that S30V is available, not for a single using knife, large or small. If buying a set of custom kitchen knives, 440C would be a good, cost effective candidate if heat treated to at least Rc58 by a competent maker.

A personal bias: ease of sharpening is very low on my list of desireable attributes. In general terms, anything easy to sharpen is easier to dull in use. (there are a few exceptions that generally prove the point, e.g. a well heat treated 52100 blade). Anything easier to sharpen generally has to be sharpened more often, making the "need to sharpen now" that much more likely to happen at inopportune times. Buy diamond stones, or a small folding diamond sharpener for field sharpening, and obviate the need for a knife that is "easy to sharpen". This is one steel trait that you can overcome with a bit of knowledge (how to sharpen) and a bit of foresight (carrying a small diamond hone with you to the field).
 
rdangerer, despite your non-metallurgical disclaimer, you got it pretty much on the mark!

While it is entirely possible to sort out the heat treatable "400-series" stainless steels (these include 154CM ATS34 BG42 etc)in order of corrosion resistance in a lab, it does require a little broader perspective to realize where they fit.

Non-stainless steels (52100, 1095, carbon steel, even tool steels like M2 or A2) have essentially no stain resistance, no inherent mechanism for resisting rust or corrosion. Stainless steels do indeed acquire their corrosion resistance through the formation of a surface layer, as you mentioned. Non-magnetic ("300-series") stainless steels, like your stainless kitchen sink is made from, are head and shoulders better than any of the heat treatable steels for corrosion resistance, because they form a stronger, more tenacious surface layer, but of course they are soft & cannot be hardened at all, so are not useful for mechanical tools of any kind. Non-iron-based alloys, like the cobalt-based Stellite type materials, do not suffer from teh inherent problem that they oxidize or corrode like iron, and thus are feee of the problems this thread was started to address.

So from a metallurgist's perspective, 440C does a pretty good job of balancing hardness and wear properties, reasonable corrosion resistance in non-extreme environments, and practicality (by which I sort of fudge together all kinds of things like cost, availability, ease of working with it, etc.). If you want to really stretch one of those properties at the expense of another, you can. For instance, the CPM stainless V series (S30V, S60V, S90V...) pushes the wear properties up, but at the expense of cost of manufacture (powder metallurgy required). The 410 and 420 series push corrosion resistance up, but at the expense of lower hardness or wear (often lower than useful for a knife blade, but often perfectly suited for other knife parts, like handles or scales, where corrosion resistance, i.e. cosmetics, is a higher priority than wear properties.)

On top of all that, as many of the other replies have mentioned, all the heat treatable stainless steels depend 100% on proper heat treating to develop their corrosion resistance at all. Variations in heat treating can result in variations in the degree to which each grade reaches its full capabilities. This is true for all heat treatable steels of course, not just the stainless ones. There is probably no greater friend to a piece of steel than a good heat treater!

So the answer is - there's nothing wrong with 440C. If you want a good quality knife with some moderate degree of stain resistance for most uses, 440C is fine. If you want something a little better for one reason or another, you can find it as well, like the CPM stainless, but that's no knock against the 440C, just another level of performance if you want to choose it. There are lots of options, lots of rungs on the ladder. We all like to keep up on the state of the art, the latest & greatest, the ultimate performers. But arguing about whether a Lamborghini is a "better" car than a Maserati in no way means that we wouldn't all be quite happy tooling around in a Corvette, eh?
 
440A, B & C, and AUS 6, 8, & 10, even GIN-1 (G-2) are all from a similar family. There are small differences among them that will add a ltiile to the hardness, wear, or corrosion properties. In fact, I am not fully familiar with all of them in detail, and there may be other subtle differences among them, so I won't profess to make specific claims for them. But all are from one very close family.

You can find a very thorough comparison of steel chemistries at Spyderco's web site, under their "Edge-u-cation" link (click "Steel Chart"). You will see that the carbon and chromium contents of all these grades are similar. In general, higher carbon is better for hardness & wear, lower carbon is better for corrosion resistance and toughness, and higher chromium is better for corrosion resistance. However, it's not that straightforward, there are a ton of trade-offs and compromises to be made.

The Japanese AUS 8 looks closest to 440B in the US. Both are attempts to strike a balance between reasonable corrosion resistance and toughness along side reasonable wear and hardness, without tilting the balance too much in favor of one at the expense of the other. I believe the Cold Steel web site mentions this very point in discussing their steels. In fact, I think they also mention the same comments as above concerning their use of AUS10 for improved wear over AUS8 when desired.
 
My EDCs are both a large and small Sebenza in BG42. Recently, I picked up a BM Outlander in 440C. I've used it quite a bit in the last few weeks for everything from food prep to cardboard box cutting. I'm amazed at how sharp this thing will get with a few strokes on my sharpmaker. It may not hold an edge for as long as my Sebenzas' but it sure is easy to sharpen.
 
so 440c is pretty much vastly superior to aus 6? I was thinking of getting a meerkat, and although I like the recurved "S" spyderco changed from 440c to aus 6 for the updated model.

guess the clear answer is go for the more traditional blade shape?
 
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