S7/5160/L6/52100 = tougher than infi?

Last Visible Canary said:
I'd love to hear exactly why nitrogen increases corrosion resistance. In INFI I know it's used as a way to increase hardness, and having a low carbon content (.5%) it's 8% chromium results in a stainless like free chromium level of 3%, which floats in the matrix to create the chromium oxide passivization surface layer... but the nitrogen part, I haven't heard a clear description of what exactly it does.

Like this article:
http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=202
which explains what nitrogen does, but not really how.
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Thats pretty good info from keytometals.com. My math skill have degraded so much that I can't do the equations at the top, but the rest is pretty straight forward.

I wouldn't call 3% Cr in solution "stainless like". It's something, but not near the 11-13% (depending on your source) needed for stainless behavior. Where does the other 5% go? I'll have to look around and see if I can find the mechanism for nitrogen reducing corrosion. It could help with the oxide layer, or tie up specific impurities and prevent pitting.
 
me2 said:
Thats pretty good info from keytometals.com. My math skill have degraded so much that I can't do the equations at the top, but the rest is pretty straight forward.

I wouldn't call 3% Cr in solution "stainless like". It's something, but not near the 11-13% (depending on your source) needed for stainless behavior. Where does the other 5% go? I'll have to look around and see if I can find the mechanism for nitrogen reducing corrosion. It could help with the oxide layer, or tie up specific impurities and prevent pitting.
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Most stainless steels at 13% chromium have upwards of .95-1.00% carbon, which as I understand it saps up an .1 to 1% ratio of chromium. So at 1.00 carbon and 13.00 chromium, the result is 3% interstitial chromium, making INFI stainless in use, but not by definition. I know that nitrogen refines grain structure and helps produce nitrides, but again not sure how or how that would reduce corrosion, other than creating a finer surface structure with less large particles to corrode away.


(edit to add: I really should have looked up a few stainless compositions before posting, as 440c's minimum chromium level is 16% o_o)
 
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Unfortunately, it's not that simple. I wish it were. The amount of chromium needed to be considered stainless is 11-13% in solution. This is a big reason the high carbon stainless steels have pretty low corrosion resistance compared to other stainless steels. A lot of the chromium gets tied up with carbon and forms carbides. If you only have 13% to start with, it's pretty easy to loose enough to carbides that you drop below the 11% level. Unfortunately, again, it's not as simple as just adding more chromium. Too much chromium, and you can't austenize the steel. If you can't austenize it, you can't harden it by quenching and tempering. Its a delicate balancing act, and this is just 3 elements: carbon, chromium, iron. Add vanadium, niobium, molybdenum, etc. and things get really complicated. Oh, and FWIW, I'd have to disagree about SR101 (52100) being less able to handle a thinner edge than D2. Steels very similar to 52100 are used for razor blades and such.
 
I'll take Jerry's word for it. All of the Kin steels do for me everything he says they will. If he says D2 will tolerate a thinner cross section with aligned forces, that is good enough for me. I really would like to start forging someday and after a few years of that, I'll set aside theoretical chemical knowledge and go with empirical experience. Until then, he knows 1000x what I do about real life performance limits.
 
Jaxx said:
The question is rather broad... Tougher how? At what Rockwell hardness? ...At what thickness? ...At what edge angle? Lateral strength, flexibility, edge retention, malleability, etc...?

To me, INFI is the best all around steel. Other types of steel may each surpass it in one or two different categories, but will not in others. For example, if a knife in INFI strikes its edge against something harder, its edge may roll or dent while another type of steel might chip out or crack. Rolls and dents are easier to repair back to a good edge and with less metal lost.
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All is said. :thumbup:

INFI does not poseses :
- the best edge retention,
- the best edge achieveing ability,
- the best shock resistence,
- the best corosion resistence,
- the most obvious ease of sharpening
- the best lateral strenght.


But INFI is :
- a very good balance of all of these properties,
- and it does not chip at 59HRC if it hits hard materials, which is very precious in the field.

To appreciate these qualities, you need time to understand them, to "feel", to "live" them with your hands, your arms, your eyes, your brain and your heart. Is there any heart in a steel mallet ?...
 
Link him the Noss destruction tests if he wants to see dumb abuse to "prove" toughness.

Just because a dude has a stump, a 2x4, a hammer and a video camera does not make him Einstein. (although smacking that knife inches away from his foot, rocking his sweet dirty "safety" Nike clad foot does make him a candidate for no toes).

Also, if some one says that the FFBM test was not a valid test because the Infi was .32, link them to the Skinny Ash1 destruction test. 3/16 thick, and took mass abuse!
 
me2 said:
Unfortunately, it's not that simple. I wish it were. The amount of chromium needed to be considered stainless is 11-13% in solution. This is a big reason the high carbon stainless steels have pretty low corrosion resistance compared to other stainless steels. A lot of the chromium gets tied up with carbon and forms carbides. If you only have 13% to start with, it's pretty easy to loose enough to carbides that you drop below the 11% level. Unfortunately, again, it's not as simple as just adding more chromium. Too much chromium, and you can't austenize the steel. If you can't austenize it, you can't harden it by quenching and tempering. Its a delicate balancing act, and this is just 3 elements: carbon, chromium, iron. Add vanadium, niobium, molybdenum, etc. and things get really complicated. Oh, and FWIW, I'd have to disagree about SR101 (52100) being less able to handle a thinner edge than D2. Steels very similar to 52100 are used for razor blades and such.
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I should know better by now than to rely on memory when it comes to anything remotely related to metallurgy, as I don't use any of it on a day to day basis and it tends to get mixed up with other things. This is the original post that I was thinking of when I posted regarding chromium in INFI. I don't know how accurate the information is, but this is what I was thinking, said as it was originally said: (I'm going to modify it with some page breaks, because it's difficult to read as a single block of text)


http://www.bladeforums.com/forums/s...e-a-couple-of-questions?p=1683496#post1683496
"
Evolute said:
Redhook asked:

"I'm not familiar with INFI. Can someone give me more details?"

If I may quote Climber, a fellow forumite, from a post on the BusseCombat site:

"Some Technical Details...
Although INFI is not considered "stainless" by the arbitrary standard by which metals are judged, which is "higher than 15% Chromium" or "higher than 14.5% Chromium" or "higher than 12% Chromium" or whoever you're asking... Yet it DOES what "stainless" is SUPPOSED to do: Retard Corrosion. What really makes something "stainless" or stains less than standard carbon steels??? A good amount of FREE Chromium is ONE method, the most common. Free Chromium inhibits bonding by "outside influences" beyond the metal matrix itself. But to GET to that stage where the Chromium is "freed up" ah, there's the rub. Carbon "locks up" 17 times its weight in Chromium, under normal circumstances, & no other factors involved; which there sometimes are... (Hey, you want a SIMPLE answer? Then ask a simpler question! Ha, Ha! )

So if a steel has 1 full % of Carbon, it would 'normally' require 17% of Chromium to bond with the Carbon, producing Chromium Carbides -- good hardness qualities, good wear resistance, good toughness as benefits --BEFORE any FREE Chromium can do any real benefit in the 'stainless' or Corrosion Resistance department. 440C is around 1% Carbon, & usually 18% Chromium; hence it is a good corrosion-fighter: It has at least as much "remaining" Chromium after Carbon-bonding as there was Carbon to begin with...
An effective ratio for Corrosion Resistance.

Some others, like D2 are less in Chromium (14.5%) & more in Carbon ~1.4%, so it has far less corrosion resistance: i have a D2 sword rusting away right next to me here, just from the humid Nebraska air... (it's an handmade experiment, OK? )

So 'steels'(NOT!) like Stellite, Talonite, & BDC, have a Cobalt Matrix, TONS (Well: 28%-32%) of Chromium! Corrosion-Proof? Time will tell, but it probably will not tell in our lifetimes! Now, if you complicate matters, & i hinted that we would, add a little Vanadium to "THE MIX" and the Carbon is all over that! It bonds well to Vanadium, and it bonds well to other elements. So that decreases the amount of Carbon that is bonding to the Chromium, thus freeing up them little Chromium guys to "patrol the borders" if ya know what i mean! (Cor~ Res~) So also an amount of Molybdenum "frees up" Chromium, keeping them little greedy Carbons from sucking up all that Chromium!

So, Now, lets look at INFI: REALLY look at it...

This stuff is DESIGNED TO BE AMAZING, and it is amazing: here's just part of why:
INFI has less than 1% of Carbon, about half a percent actually; & 9% Chromium. Do the Math: 0.5% Carbon bonding with 17 times its weight of Chromium = 8.5% Chromium used as Chromium Carbides, leaving a remainder of 0.5% Chromium; which is as much as the Carbon was to begin with: so, same RATIO as 440C, a known, proven "Rust-Fighter." Also, wouldn't you know it, there's Vanadium AND Molybdenum AND Nickel AND Cobalt in that thar piece of INFI Steel ! So, there's actually a LOT more free Chromium runnin' 'round the Matrix than our math-formula suggests, as Carbon atoms bond with those other elements. Oh Yeah: Not to mention NITROGEN, which changes and enhances the bonding in more ways than i currently can spew...

Enormous Toughness; flexibility, metal-memory, hardness properties retained & not subdued, wear resistance maximized, STRENGTH beyond the legendary Wootz(!) etc, etc.
THEN: there's the heat treatment: Transversion-Wave HT... But it's a Secret: Shhh... Let's just say that Heat Treat is still the most important factor, which is why INFI is the most Advanced Steel we can commercially buy...
Enuf already!"
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"

and for quick reference:
http://www.bladeforums.com/forums/s...-to-help-pass-some-time?p=2100156#post2100156
mark23 said:
This is what I found ...

INFI:
C: 0.5
Cr: 8.25
Co: 0.95
Mn: 0.4
Mo: 1.3
V: 0.36
N: 0.11
Si:?
Ni: 0.74
Fe: Balance

Mod. INFI:
C: 0.58
Cr: 7.94
Co: 0.026
Mn: 0.37
Mo: 1.34
V: 0.48
N: 0.01
Si: 0.98
Ni: 0.29
Fe: Balance

Looks like two different steels. Using good laboratory equipment it is rather easy to make an analysis like that. The most important step in making a Busse knive is the special heat treatment, IMHO. And this, of course, is Jerry's best kept secret, I would say :)

Regards

Mark23
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Well, those bonding ratios and such aren't the way it works, but the concepts are close...sort of.
 
Yep, it's all in the heat treatment. Without the recipe for heat treat, the INFI would not perform so well. I really like the heat treatment they do on the SR 101 too:cool::thumbup: Sr 101 seems to get sharper, but loves to rust, and would probably chip instead of dent or roll....so that's when INFI steps back in:)

To me, INFI is the the player that can play every position very well.:thumbup:
 
infi is not the hardest, is not the toughest and is not the most corro-resisting. but it has been an good all around steel that can be put in any situation. in overall infi preformed very good compare to most other steel.

there is another excellent all arround steel that may out preform INFI. Bohler's N360 ISOExtra. at the hardness of RC 58 the unnotched impact toughness is no less than 70j/cm^2. hardness of RC 56~57, impact toughness reaches 140j/cm^2. 14%Cr and 0.4% N also meant supperior corro-resistance. however the price is extramly high as well. its like $400 per kg something, pretty over priced for PESR steel.
 
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