S30V vs M390 Toughness?

[chiral.grolim]

back on topic, Crucible has the toughness of 20cv listed as the same as 440c at two points higher in hardness. crucible has s30v listed as being 4 times tougher than 440c... any clarification on why the manufacturer has s30v as being tougher than 20cv? are they incorrect? If what i'm reading from crucible is incorrect please correct me i'm just confused on why crucible would be incorrect about the steels they developed

Pulling back because I didn't see anyone else correct this, though i haven't bothered reading every post since,

See my post just before that one? It contains data sheets from Crucible on S30V and CPM-20CV. It looks like simplytoolsteel took they comparative transverse toughness comparison of S30V and such to 440C and pretended it was longitudinal toughness and kept the same proportions for only those steels, i.e. utter nonsense. Per crucible, S30V and S35VN and CPM-20CV, etc. all present about the same impact toughness as 440C but at a few points higher hardness (which is good, but nothing like what that graph pretends).

Crucible lists S30V and S35VN and CPM-20CV and 440C all at the same toughness, i.e. 25-28J via Charpy C-notch. THAT IS LONGITUDINAL TOUGHNESS. Crucible only lists S30V as 4x tougher than 440C via TRANSVERSE impact-testing which isn't really relevant. It's a marketing ploy. You rarely find transverse-toughness values because they are generally all <15J (quite weak) and because makers specifically design/manufacture their tools to avoid the problem. When you look at Crucible's compar-o-graphs on their website, the toughness values presented are all longitudinal.

The problem is that simplytoolsteel, like yourself, didn't bother understanding what was typed in that datasheet, that S30V only offers superior transverse toughness and not longitudinal toughness. Hence the confusion.

Read and understand.

 

[shinyedges]

turns out i wasnt clueless... and i was correct. No hard feelings, sharing information so we all learn is what this community is all about. This thread pushed me to search and learn more and part of that is thanks to you so.. thanks ankerson.

And think about those possibilities if they would have, instead of S30V back then it would have been a lot different....

 

[shinyedges]

I'm not perfect and still have alot to learn from the great folks here.. thanks for clarifying. No need to come off rude.. if i offended you over this topic it was unintended.


If you would educate me what exactly is TRANSVERSE IMPACT toughness? and why is it irrelevant? thanks

Pulling back because I didn't see anyone else correct this, though i haven't bothered reading every post since,



Crucible lists S30V and S35VN and CPM-20CV and 440C all at the same toughness, i.e. 25-28J via Charpy C-notch. THAT IS LONGITUDINAL TOUGHNESS. Crucible only lists S30V as 4x tougher than 440C via TRANSVERSE impact-testing which isn't really relevant. It's a marketing ploy. You rarely find transverse-toughness values because they are generally all <15J (quite weak) and because makers specifically design/manufacture their tools to avoid the problem. When you look at Crucible's compar-o-graphs on their website, the toughness values presented are all longitudinal.

The problem is that simplytoolsteel, like yourself, didn't bother understanding what was typed in that datasheet, that S30V only offers superior transverse toughness and not longitudinal toughness. Hence the confusion.

Read and understand.

 

[Ankerson]

Pulling back because I didn't see anyone else correct this, though i haven't bothered reading every post since,



Crucible lists S30V and S35VN and CPM-20CV and 440C all at the same toughness, i.e. 25-28J via Charpy C-notch. THAT IS LONGITUDINAL TOUGHNESS. Crucible only lists S30V as 4x tougher than 440C via TRANSVERSE impact-testing which isn't really relevant. It's a marketing ploy. You rarely find transverse-toughness values because they are generally all <15J (quite weak) and because makers specifically design/manufacture their tools to avoid the problem. When you look at Crucible's compar-o-graphs on their website, the toughness values presented are all longitudinal.

The problem is that simplytoolsteel, like yourself, didn't bother understanding what was typed in that datasheet, that S30V only offers superior transverse toughness and not longitudinal toughness. Hence the confusion.

Read and understand.

The reason I didn't say anything is because I find it irrelevant.....

Since most are talking about folders or small fixed blades, it doesn't really matter anyway.... Impact testing that is....

And for the larger harder use knives they have thicker geometry anyway so that takes care of those issues.

For Swords the simpler low alloy spring steels are used and HT in a variety of ways.....

 

[shinyedges]

Any one care to answer what exactly transverse impact toughness is? and why its irrelevant..... also if its factual data about the steel then how is it a marketing ploy?

 

[Ankerson]

Any one care to answer what exactly transverse impact toughness is? and why its irrelevant..... also if its factual data about the steel then how is it a marketing ploy?

It's not a marketing ploy by the steel companies pertaining to knife blades....

It just doesn't have any real meaning at all when talking about knife blades...

Impact toughness in general doesn't really have as much relevance as some try and make it out to have in normal sized blades most use, folders and small fixed blades..

 

[shinyedges]

I guess the word transverse through me off... so its just impact toughness? which is usually not important in small knives because there not impact tools and under regular use wont face impact beyond what the steel will handle? and its more applicable to choppers and large knives because they face more impacts in regular use?

It's not a marketing ploy by the steel companies pertaining to knife blades....

It just doesn't have any real meaning at all when talking about knife blades...

Impact toughness in general doesn't really have as much relevance as some try and make it out to have in normal sized blades most use, folders and small fixed blades..

 

[Ankerson]

I guess the word transverse through me off... so its just impact toughness? which is usually not important in small knives because there not impact tools and under regular use wont face impact beyond what the steel will handle? and its more applicable to choppers and large knives because they face more impacts in regular use?

In general, yes....

Most problems people have they create themselves really....

It can be sharpening issues....

Lowering the edge angles too low for the steel and the intended use of the knife...

Using the knife in a way it wasn't designed to be used.

 

[shinyedges]

ok i gotchya, thank you. While i get why the transverse impact toughness is irrelevant most of the time I still like knowing what they are... i mean why not it cant hurt to know more about the steel. And i agree with you most people do create there own problems and then blame the steel.. not always but i'd bet its pretty common. Thanks again for explaining it.

In general, yes....

Most problems people have they create themselves really....

It can be sharpening issues....

Lowering the edge angles too low for the steel and the intended use of the knife...

Using the knife in a way it wasn't designed to be used.

 

[Ankerson]

ok i gotchya, thank you. While i get why the transverse impact toughness is irrelevant most of the time I still like knowing what they are... i mean why not it cant hurt to know more about the steel. And i agree with you most people do create there own problems and then blame the steel.. not always but i'd bet its pretty common. Thanks again for explaining it.

If it was as relevant as some try and make it out to be then almost every knife on the market would snap like glass doing almost nothing...

And I wouldn't have been able to do this with a knife in an A11 Steel... (CPM 10V) That has SAK geometry..... That's .070" spine thickness and .020" behind the edge....

That includes snapping out the blade sideways in the wood....

 

[chiral.grolim]

Any one care to answer what exactly transverse impact toughness is? and why its irrelevant..... also if its factual data about the steel then how is it a marketing ploy?

Slow down, I don't get a chance to post that many times in a day.

Transverse vs longitudinal has to do with grain-direction. In a transverse-impact test, the fracture is able to follow the grain of the steel. In a longitudinal test, the grain runs perpendicular to the impact and so prevents such propagation.

With ingot steels, low transverse toughness is more of a concern, particularly ones with large chromium carbides like 440C. The impact toughness is very low between the grains, the material fractures readily. But if you manufacture your tools to take advantage of the increased longitudinal toughness, it isn't really a problem. That is how knives are made, so the tool follows the grain of the steel and provides enhanced toughness (~10X tougher for 440C). That is how 440C achieves 25-28J, which is the same as S30V and CPM-20CV a couple of points harder, all of which are MUCH lower than CPM-3V (113J at 58Rc). Again, those are longitudinal values.

Powder steels mitigate the transverse grain issue but do not fully eliminate it (hence S30V transverse toughness of only 10J vs 28J longitudinal)
However, in use your knife is unlikely to ever encounter a transverse impact (assuming it was milled correctly).
That typed, many regard concern over impact toughness or reference to measured values from Charpy C-notch testing entirely irrelevant to knife use altogether. We are far more likely to need high levels of fracture resistance in NON-impact use, i.e. strength.

EDIT to add: as Jim's knife above, strength at thin geometry.

 

[Jerry Hossom]

In my opinion transverse toughness does matter, and it's a proof is in the pudding kind of thing. It's also a point where metallurgical numbers and practical experience diverge. Can you take transverse toughness to the bank and say it defines edge toughness? No, but it is a guide and getting back to S30V, the target was to have a stainless with the wear resistance of D2 and the toughness of, get this, A2. A2? Yep, because A2 was long known for being a tough steel. In fact in the wood working world the very best chisels and planer blades were made of A2, and not that long ago - 10-15 years. Why A2? Because when they used it for the purposes those blades are designed they held their edge longer than other steels you might think would hold any edge longer - like maybe D2. Why? Toughness, not "wear resistance". Because what killed those edges wasn't wear, it was micro-chipping, one of the things that kills knife edges, probably more than what we think of as "wear". I did some work with people in the serious woodworker world some years ago, when they were searching for a better steel for those tools. What they went to was CPM-3V, not CPM-10V. Why? Because what really matters is what works. Numbers, not so much. We, especially in these forums, become enamoured of numbers and often make judgements based on those. Harking back to what Dick Barber told me. "We really don't know how steel performs in knife edges." He had all the numbers in the world available to him, but he knew they didn't matter in the end. When you look back on the numbers however, you'll see that lateral toughness correlates reasonable well with actual performance. You can't say 8 is better than 6, but you can probably say 10 is better than 4.

 

[shinyedges]

Jerry, I learn more with every word you type... keep it coming lol I need your number on speed dial for when i have these questions. The way you explained that just made sense to me. Thank you sincerely for your time...

In my opinion transverse toughness does matter, and it's a proof is in the pudding kind of thing. It's also a point where metallurgical numbers and practical experience diverge. Can you take transverse toughness to the bank and say it defines edge toughness? No, but it is a guide and getting back to S30V, the target was to have a stainless with the wear resistance of D2 and the toughness of, get this, A2. A2? Yep, because A2 was long known for being a tough steel. In fact in the wood working world the very best chisels and planer blades were made of A2, and not that long ago - 10-15 years. Why A2? Because when they used it for the purposes those blades are designed they held their edge longer than other steels you might think would hold any edge longer - like maybe D2. Why? Toughness, not "wear resistance". Because what killed those edges wasn't wear, it was micro-chipping, one of the things that kills knife edges, probably more than what we think of as "wear". I did some work with people in the serious woodworker world some years ago, when they were searching for a better steel for those tools. What they went to was CPM-3V, not CPM-10V. Why? Because what really matters is what works. Numbers, not so much. We, especially in these forums, become enamoured of numbers and often make judgements based on those. Harking back to what Dick Barber told me. "We really don't know how steel performs in knife edges." He had all the numbers in the world available to him, but he knew they didn't matter in the end. When you look back on the numbers however, you'll see that lateral toughness correlates reasonable well with actual performance. You can't say 8 is better than 6, but you can probably say 10 is better than 4.

 

[Jerry Hossom]

Let me qualify what I just said. While S30V might have a transverse toughness of 10 and 154CM a toughness of (I forget exactly but) say 4. A coarse S30V edge will not perform better than a more polished 154CM edge. And that is where a lot of these discussions fall apart. There are a whole lot of variables in the equation and we tend to look at only one or two at a time.

 

[shinyedges]

I understand, variables... lots of them. Before i got into blade steels and knives I never knew so many factors were at play when comparing steels but sweet heavens there are a lot. The key i believe is to try and make an apple to apple comparison when pitting two steels against one another example same edge thickness, finish on edge coarse or fine or polished ect.. I get what your saying though..

Let me qualify what I just said. While S30V might have a transverse toughness of 10 and 154CM a toughness of (I forget exactly but) say 4. A coarse S30V edge will not perform better than a more polished 154CM edge. And that is where a lot of these discussions fall apart. There are a whole lot of variables in the equation and we tend to look at only one or two at a time.

 

[james terrio]

post reserved... let me think on this some before I ask the questions that are bothering me...

 

[Jerry Hossom]

Just say it, James. I've been wrong before...

 

[Ankerson]

Just say it, James. I've been wrong before...

I don't think it was you.

 

[Ankerson]

In my opinion transverse toughness does matter, and it's a proof is in the pudding kind of thing. It's also a point where metallurgical numbers and practical experience diverge. Can you take transverse toughness to the bank and say it defines edge toughness? No, but it is a guide and getting back to S30V, the target was to have a stainless with the wear resistance of D2 and the toughness of, get this, A2. A2? Yep, because A2 was long known for being a tough steel. In fact in the wood working world the very best chisels and planer blades were made of A2, and not that long ago - 10-15 years. Why A2? Because when they used it for the purposes those blades are designed they held their edge longer than other steels you might think would hold any edge longer - like maybe D2. Why? Toughness, not "wear resistance". Because what killed those edges wasn't wear, it was micro-chipping, one of the things that kills knife edges, probably more than what we think of as "wear". I did some work with people in the serious woodworker world some years ago, when they were searching for a better steel for those tools. What they went to was CPM-3V, not CPM-10V. Why? Because what really matters is what works. Numbers, not so much. We, especially in these forums, become enamoured of numbers and often make judgements based on those. Harking back to what Dick Barber told me. "We really don't know how steel performs in knife edges." He had all the numbers in the world available to him, but he knew they didn't matter in the end. When you look back on the numbers however, you'll see that lateral toughness correlates reasonable well with actual performance. You can't say 8 is better than 6, but you can probably say 10 is better than 4.

There is a lot of truth to that.

There is a variety of ways that an edge will dull.

Micro chipping is one of them, rolling, and flattening are the other two main ones.

So there has to be a balance, part of that is steel choice based on what the knife was designed to do.

Some of the others are geometry based on both the steel choice and what the knife was designed to do.

Then we have HRC hardness that is also based on what the knife is designed to do.

So the choices in the end have to be picking the steel, geometry, and final hardness that will give the best overall performance based on what the knife is designed to do. So a balance between toughness, edge retention and slicing/cutting ability has to be made.

And that's why we have choices in steels and knife makers like you that can balance those needs out to provide people with the best performing knives we can get.

 

[Ankerson]

Here is a simple example using two knives that are really designed for two completely different types of uses, both are M390....

The 1st one is .006" behind the edge and 62 HRC with a 10 DPS edge geometry.....

The 2nd one is .035" behind the edge, 60 HRC with 20 DPS egde geometry...

Both together.....

Now looking at these two knives that are about the same overall size, close to the same blade length, same steel, M390......

What knife would be more suited for slicing and what knife would be more suited for hard use?

I used this extreme difference to make a point that knife design is just as important as any other factor in choosing what needs have to be met.