A8 Tool Steel vs CPM 3V?

flatgrinder

flatgrinder

Joined
Dec 20, 2005
Messages
2,045
Which steel is tougher A8 Tool Steel or CPM 3V?

Which one has better edge retention?

Thanks! :thumbup:
 
I just found some numbers and thought others might be interested.

A8 (at HRC 59) in the charpy c-notch impact test results in 160 joules. CPM 3V is 104 joules at the same hardness. So A8 wins easily.

(FYI: S7 at HRC 57 is 165 joules).

Any idea in regards to edge holding for these two steels? :thumbup:

Thanks!
 
Last edited:
Last edited:
never used A8
but sure do love 3v and i have beat on it. i have ot guess that liek many things once you get past a point the returns are slight for the application
 
Hypothetically, in what situation would you need a knife steel tougher than CPM 3V?

If a steel like A2 is not tough enough, you would want a big toughness upgrade like 5160 or S5, rather than moderate toughness upgrade like 3V.
 
It all depends how often you want to sharpen your knife and for the few extra pennies your trying to sqweeze out of a inferior steel . If you want good steel then pay for it and get cpm154 or 154cm or ats34 . the edge retention is at a completly different level . Ive sharpend a fair number and have made a few from 8a and wont buy it anymore.
 
cotdt said:
Hypothetically, in what situation would you need a knife steel tougher than CPM 3V?

If a steel like A2 is not tough enough, you would want a big toughness upgrade like 5160 or S5, rather than moderate toughness upgrade like 3V.
Click to expand...

How tough is 5160, tougher than 3V?

Can you give some joule/ HRC

S7
165 joule / 57 HRC

S5
193 joule / 58 HRC

S1
212 joule / 59 HRC

3V
113 joule / 58 HRC
95 joule / 60 HRC
53 joule / 62 HRC

A2
45 joule / 58 HRC
50 joule / 59 HRC
56 joule / 60 HRC

5160
?

Thank you
 
The data for A2 toughness analysis doesn't make any sence. Typically the chirpy impact numbers go up as the hardness goes down. Which makes sence, as the steel becomes harder and more brittle. These numbers look more what you would expect from tensile test. In that instance the harder the steel gets the more force it takes to tare the metal apart resulting in much higher forces.
 
Razor080 said:
The data for A2 toughness analysis doesn't make any sence. Typically the chirpy impact numbers go up as the hardness goes down. Which makes sence, as the steel becomes harder and more brittle. These numbers look more what you would expect from tensile test. In that instance the harder the steel gets the more force it takes to tare the metal apart resulting in much higher forces.
Click to expand...
It could be for a couple reason. I would bet that whoever tested the a2 tempered into the range where tempered martensite embrittlement starts to occur.

That or they may have went too hot when austenizing on those two. Possibly both. Without having the heat treatment temperatures they used we can't be certain.
 
Never used A8 naked but make sure you guys are checking how the Charpy testing is done. Some datasheets list transverse toughness, some list longitudinal which is. More common in the steel industry but not exactly the most pertinent for knives. (It's usually a transverse break, aka the smallest cross section). There's.. yield and ultimate strength. The way I usually explain it, yield is when it will bend and return to true. Exceeding that, is actual plastic deformation which is into the "ultimate" area and the end of that would be of course the break. I'll stay out of the weeds!
Blankblank said:
It could be for a couple reason. I would bet that whoever tested the a2 tempered into the range where tempered martensite embrittlement starts to occur.

That or they may have went too hot when austenizing on those two. Possibly both. Without having the heat treatment temperatures they used we can't be certain.
Click to expand...
A2 is going to be right on the limit of alloying for TME so that would be my vote.

Razor080 said:
The data for A2 toughness analysis doesn't make any sence. Typically the chirpy impact numbers go up as the hardness goes down. Which makes sence, as the steel becomes harder and more brittle. These numbers look more what you would expect from tensile test. In that instance the harder the steel gets the more force it takes to tare the metal apart resulting in much higher forces.
Click to expand...

That's.. not exactly true. Tempering is a lot more complicated than just.. Heat to soften. Micro carbide reabsorption, solid-solid phase changes..etc. I said I'd stay out of the weeds!

Neo said:
How tough is 5160, tougher than 3V?
Click to expand...

Yes it is but ingot not PM, more carbon, vanadium. Molybdenum (hardenability and pitting resistance but A LOT..). I prefer heat treating 3V personally.

cotdt said:
Hypothetically, in what situation would you need a knife steel tougher than CPM 3V?

If a steel like A2 is not tough enough, you would want a big toughness upgrade like 5160 or S5, rather than moderate toughness upgrade like 3V.
Click to expand...

S5 > S7 in toughness but S7 should be plenty for anything. I'm wondering the same thing here. I think most people forget that.. 5160 is still what? 97+% iron? Steel is steel guys, it's known to be tough and all of this is relative.
 
Last edited:
Jack Marsey said:
Never used A8 naked but make sure you guys are checking how the Charpy testing is done. Some datasheets list transverse toughness, some list longitudinal which is. More common in the steel industry but not exactly the most pertinent for knives. (It's usually a transverse break, aka the smallest cross section). There's.. yield and ultimate strength. The way I usually explain it, yield is when it will bend and return to true. Exceeding that, is actual plastic deformation which is into the "ultimate" area and the end of that would be of course the break. I'll stay out of the weeds!

A2 is going to be right on the limit of alloying for TME so that would be my vote.



That's.. not exactly true. Tempering is a lot more complicated than just.. Heat to soften. Micro carbide reabsorption, solid-solid phase changes..etc. I said I'd stay out of the weeds!



Yes it is but ingot not PM, more carbon, vanadium. Molybdenum (hardenability and pitting resistance but A LOT..). I prefer heat treating 3V personally.



S5 > S7 in toughness but S7 should be plenty for anything. I'm wondering the same thing here. I think most people forget that.. 5160 is still what? 97+% iron? Steel is steel guys, it's known to be tough and all of this is relative.
Click to expand...
What datasheets use transverse toughness!? You obviously do know what you are talking about. I can tell that! šŸ§

This is news.
 
I'm not exactly sure I know Vanax lists it transversely but you would have to research that stuff man.
 
I have a graph that shows A8 toughness at 59rc at just about as equal to L6 toughness at 60rc. The graph doesn't provide joules or foot pounds of energy so I can't speculate on the numerical value of its toughness. However L6 is extremely tought in a worst case scenario its equal to 5160 in toughness, yet I've personally always found L6 to be tougher than 5160. And I've seen other graphs indicating that L6 and 5160 are tougher than 3v. Again its hard to say by how much but simply going off of graphs you can speculate around 30%-35%. And since A8 is the same toughness as L6 one can deduce its going to be roughly 30% tougher than 3v. I have two knives made out of A8. Its a an impossible steel to find here in the States, almost no one uses it. One Custom maker used in the early 2000 Tom Johanning. Everyone that reviewed his knives said they were tough as hell. I've never abused my knives cause its impossible to find knives made from this steel so I rather not destroy them. Also remember reading somewhere that when INFI Steel used by Busse was send for analysis, that it came back basically indicating it was essentially A8 with few minor tweaks. Aperantly their current steel they use now doesn't have nitrogen. I will try to find that forum or article and post a link here. In conclusion A8 should be a very tough steel, in a worse case scenario its just as tough as 3v, but most likely its much tougher. I know its not very scientific cause I don't have numerical data but based on whats written and graphs thats the conclusion I've reached so far.
 
Someone sent me some woodworking tools in 3V at 59 hardness. It would be difficult to find any reasonable failure in it's length direction at 59 hardness, and what it has at that hardness is probably better than 5160 and L6 because it's not anywhere close to its hardness limits.

But you can do simple heat treatment with L6 and 5160, I guess.

The toughness of 3V actually creates a problem for woodworking tools where strength of the edge is more important than toughness, at least to a point, and 3V will hold little bits of damage and let them propagate. Different application than knives, I guess, but the ability of 3V to hold on to bits of damage was pretty incredible.

For practical purposes, if there's that much difference between something like less than hard tempered 3V or 52100, I can't imagine 5 or 10% more cross section wouldn't negate the difference.
 
You must log in or register to reply here.
Back
Top