How is cpm M4 vs. INFI

This discussion seems rather, um, theoretical...since few here have used large blades in M4 and INFI.
 
AF said:
This discussion seems rather, um, theoretical...since few here have used large blades in M4 and INFI.
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The OP was talking about 4" inch fixed blades though. The discussion somehow got sidetracked to toughness and now people are talking about S30V. Classic internet discussion.

But I agree, M4 is still pretty tough at 63 rc, the data says it's still tougher than D2 at 60 rc. Most of my M4 knives are around this hardness.
 
cotdt said:
The OP was talking about 4" inch fixed blades though. The discussion somehow got sidetracked to toughness and now people are talking about S30V. Classic internet discussion.

But I agree, M4 is still pretty tough at 63 rc, the data says it's still tougher than D2 at 60 rc. Most of my M4 knives are around this hardness.
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My answer to the OP would be that you would not be at a loss with either steel. They are both premium cutlery steels and would perform just fine for a 4-8 inch fixed blade. Both hold edges well. Both are tough. That's all that matters in a fixed blade of that size.
 
steelnut said:
Why does it have to be large to be tough?
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It doesn't but most would agree that toughness is an attribute more desired in a large blade. And it's easier to test toughness (in usage) with a large blade - like when chopping for instance.
 
??? How, those are rather different applications. In simple words tough knife can chop through the hard medium, withstand twisting and prying, hard and thin edges with M4 @65 HRC definitely will break...
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agreed, I was just trying to point out that comparing toughness at different (up to 5 Rc points different) hardness is not really helpfull
 
To make a real comparision, you'd need to have 4-5 of the same models made with each metal and then do a series of tests.
My gut feeling is if you went to all that trouble and expense the result would be kind of a tie.
 
There are some very good informative threads about infi.
Do some searching and reading.
It comes down to: infi is basically A8mod, and the long heat tread period is typical for an air hardening steel like A8.
There goes a lot of marketing and hype

This said infi is a very good steel.
The reason A8 isn't used more in the knife industry is because of the very high price.
Busse build up an reputation going from A2 and is managing to deal with this.
Other companies don't take the risk

About toughness.
I guess it's something between A6 and A9
http://corse76.altervista.org/col.php?noti2=resilienza

Be aware it's M4 in this graphic, not cpm M4 and it's at an hardness of 64 HRC.
I think cpm m4 has one of the best combinations between toughness and edge holding.
 
From what has been said in the Busse forums, the INFI steel itself is not expensive, I doubt as expensive as a CPM steel, but the heat treat is very involved. Doing a "proper" heat treat is indeed relatively expensive considering that like M4, INFI is heat treated as a high speed steel using a high temperature temper several times.
 
Since chopping is more about impact resistance than edge holding, and cutting/slicing is more about edge retention than impact resistance, my gut says INFI,but, since INFI is proprietary and M4 is not, M4 gets the nod from me.
 
cotdt said:
From what has been said in the Busse forums, the INFI steel itself is not expensive, I doubt as expensive as a CPM steel
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S30V is almost $17.00 a pound.
CPM3V is about $15.00 a pound.
A8 is about $50.00 a pound.

The heat threat used is not uncommon for this kind of steel.
The steel itself isn't used much because of the cost of purchase and the cost for grinding and machining this though stuff.
 
Neo said:
S30V is almost $17.00 a pound.
CPM3V is about $15.00 a pound.
A8 is about $50.00 a pound.

The heat threat used is not uncommon for this kind of steel.
The steel itself isn't used much because of the cost of purchase and the cost for grinding and machining this though stuff.
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You need to switch A8 suppliers as quickly as possible.

Your "cost of grinding and machining" comment is BS.
 
Jesus Christ, Buddha, Confucious, Dos Equis Most Interesting Man in the World, and Taco Bell Dog:

We pray to you, in hopes that you will once and for all descend upon us and eliminate this oft-perpetuated, dumbass notion that INFI is in any way, shape, or form modified A8. Give unto those who can't read a chart the understanding that INFI contains components that are not included in A8, and that A8 contains components that are not included in INFI. Allow them to see that those of us who say that it isn't A8, or modified A8, or discombobulated A8, do not say so because we hate A8, but because it simply is a fact that it's NOT A8.

I Metallurgy's name we pray,
Amen
 
Neo: thanks for bringing a little salt and pepper to the table. What is life without the spice? I am curious about your numbers on A8 or A8 mod. You do realize that just because a company prints out a fact sheet on their material does not implicitly imply truth (unless we could be around for rockwell and charpy measures that were verified by an honest, impartial 3rd party) in any form of the word. Watch out for marketing!

AISI A8 Tool Steel may contain any number of various combinations, a pinch here, a few grams here of a variety of heralded materials, some of which may be known only to the chemists/metallurgists. One formula for this tough offering insists that A8 is:

C .50 - .60
Cr 5.00
Fe 90.00
Mn .50
Mo 1.4
P .03
Si .93
S .03

Still another states that A8 mod (chipper steel harder than a harlot's heart) is:


C .50
Cr 8.00
Fe 88.00
Mn .45
Mo 1.30
Si .95
V .45

Or what about this combo?

Ni .30
W 1.00 - 1.50
P 0.03
S 0.03
Cu 0.25
C .50 - .60
Si .75 - 1.10
Mn .50
Cr 4.75 - 5.50

Which report are we to believe? I once tried to make an apple pie from an old cooking book. It never did taste like the one my grandmother made.
 
Here's your toughness test, Have 2 similar sized knives, one INFI one M4. Have them both sharpened at 10deg per side. Now cut just hard woods, and do real use activities. See what happens to which steel. I know who my money is on.
 
Stubai said:
One formula for this tough offering insists that A8 is:
C .50 - .60
Cr 5.00
Fe 90.00
Mn .50
Mo 1.4
P .03
Si .93
S .03
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I believe this one is incorrect, as the Tungsten(W) is omitted.

Stubai said:
Or what about this combo?

Ni .30
W 1.00 - 1.50
P 0.03
S 0.03
Cu 0.25
C .50 - .60
Si .75 - 1.10
Mn .50
Cr 4.75 - 5.50

Which report are we to believe?
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The last one is the official AISI A8 definition. Otherwise, efunda, Matweb, kaker and dozen other steel resources are wrong, including my own steel charts. As usual I cross reference at least several sources (when available)...
 
I don't think INFI is any one of those A8 steels. You can order your own compositional mix of steel if you order enough of it. INFI is a proprietary mix. If you have the money you can even order a powder version of it made by Crucible.
 
Yeah, the last part is the one people have hard time coping with :) I've heard it a lot of times, nobody is gonna make special steel for a maker, they're too small etc...
In fact most of the steel companies producing those super duper steels are nowhere in top 30 steel producers of the world. If you pay, you will get your formula.
 
Gator97 said:
Yeah, the last part is the one people have hard time coping with :) I've heard it a lot of times, nobody is gonna make special steel for a maker, they're too small etc...
In fact most of the steel companies producing those super duper steels are nowhere in top 30 steel producers of the world. If you pay, you will get your formula.
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Yeah it is definitely doable even by a small knife manufacterer. All Metals & Forge, LLC can supply Air or Vacuum Melted Designer Alloys™ in quantities as small as 250 lbs. Crucible would do a custom melt of powder steel if you order 45,000 lbs. of it. There's quite a number of other places that can do custom melts.
 
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