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Rust and 440V

Joined
Oct 13, 1998
Messages
669
I just got a Kershaw Random Task, and was wondering how easily the 440V blade will rust. Is it stainless like ATS-34 or stainless like 304...or somewhere in the middle(my guess)
Aaron

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aaronm@cs.brandeis.edu
I like my women like I like my knives: strong, sharp, well-formed and pattern-welded!
 
I made a kitchen knife with CPM440V and have tried (sorta) to let it rust. I have left it in the sink covered with tomato juice, whatever for a day or two at a time, tossed it into the dishrack wet and let it dry. Never even so much as a hint of corrosion. I find it very difficult to REALLY abuse it just to see, but from what I've read CPM falls somewhere in between ATS and the other VERY stainless steels...jeff
 
Aaron - "Q-Fog" data suggests that CPM-440V is not a good as ATS-34 in corrosion reistance. But the difference is quite small.

After 6 hrs in Q-fog, ATS-34 had a .9% advantage over CPM-440V

After 24 hrs, this advantage decreased to .4% advantage.

After 48 hrs, .07% advantage.

After 72 hrs, .02% advantage.

Keep in mind that Q-Fog is extreme. few would ever expose their knives to even 6 hours of Q-Fog equivalent. After 72 hours, both CPM-440V and ATS-34 were rusted toast. After 6 hours, both CPM & ATS had lost 40% of their surface to rust.

From a comparison basis, ATS has a slight advantage over CPM (less that 1%). Neither will resist corrosion nearly as well as 440C, but both are superior in edge retention to 440C.

"Generally" speaking, corrosion, edge retention and carbon content go together. Steels like 304, which have no carbon resist corrosion very well, but are just about impossible to keep sharp (serrations help).

hope this helps.
sal
 
I'm somewhat confused at the results of the Q-Fog testing. To start, what is it and how is it conducted? How are the results measured?

The main reason for the confusion comes from having formed some conclusions after reading about the different steels. I was under the opinion that it is the free Chromium (>10% is stainless) that added to the stainless properties of the steels. For most steels Chromium is a carbide-former. But, Vanadium and Molybdenum are also a carbide-formers. With ATS-34 having 14% Chromium and CPM-440V having 17% Chromium, I would think that CPM-440V would be more stainless (potentially of course). Although there are other carbide formers present in both steels (Molybdenum 4% in ATS-34 and Vanadium 5.5% in CPM-440V), could the Q-Fog results be an indication of the higher carbon content (2.15% versus 1.05%) in CPM-440V that forms more carbides and thus reduces the free Chromium in the steel?

Anybody have an answer?

Hmm...perhaps if this is true a better knife steel might be 440V with a little less carbon content?

jj

[This message has been edited by jeffj (edited 05 July 1999).]

[This message has been edited by jeffj (edited 05 July 1999).]
 
What exactly is "Q-Fog".
You are right on the free Chromium, but depending on the corrosive environment the Chromium may or may not be the most important element.

If you drop the carbon on the 440V the attainable hardness will be affected.

440V was designed to be in the same ballpark as 440C (Corrosion resistance wise). Any differences seen between the two will depend on the corrosive environment.
 
Thanks for all the info! I expected the corrosion resistance to be in the ATS-34 range, and it's good to have experimental data to back that up. I guess I'll have to actually oil the blade, instead of storing it in vinager
smile.gif

Aaron
ps Sal, I guess I should have used 410 as the most rust-resistant hardenable steel.

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aaronm@cs.brandeis.edu
I like my women like I like my knives: strong, sharp, well-formed and pattern-welded!
 
Thanks for the info, Sal. I guess that's why the blade on my BF Native seemed to get a few spots so quickly after getting a little ketchup on it, similar to the ATS34 blade that I had also.

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Work hard, play hard, live long.
Outlaw_Dogboy

 
from my understanding....440V is mainly 440C made with the particle metallurgy process and a bunch of vanadium added.....so the chromium content is the same....and corrosion resistance is excellent...but any knife steel that has iron and carbon in it will rust.....some moreso than others....whereas the 300 series...(in original question) are nonmagnetic...no iron, which is the thing in steel that rusts. I just got thru cleaning up a ATS blade for a guy who got stuck up in the mountains for three days in a radical rain storm//// three days /// his machete that i made him was cover with rust...light...and slightly pitted all over.... but i have knives of the same steel hanging in my shop that i ground 10 years ago and never finished and are shiny, without the hint of any corrosion.....the fog test might be a good indicator but there are a lot of things out there in the real world that change the variables....like when an animal product sheath gets soaking wet and your knife is in it for days......or blood or salt water, etc..the real world is the best place to test stuff.....and unless its stellite or talonite or ti...it will rust...count on it.

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http://www.mayoknives.com


 
For me 440V does not rust however ats does. So much for Q fog tests haha. I guess it just goes to show you that we are all a lil different. Only explaination I ever came up with was it had something to do with my sweat Although I have knives stored side by side and the ats will freckle while the 440V will not. I don't understand why.


Regards,

Tom Carey
 
Tom-
Probably impurities in the ATS.
That is the comment I get from many custom makers.

Also, satin finish or a high polish (like that Mini Mamba!)
smile.gif
will certainly reduce
corrosion of any steel.

I just use Tuf-Glide/cloth (ahhhhhhhhhhhh)
and dont have any more rust worries....
 
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