K490

Many steels that are used in knives today are actually steels that were designed for industrial applications, rather than knife making. That's not to say that you cannot use these steels for knives, but the knife market is a very small percentage of their distribution.

Just because a steel looks good on paper, does not mean that it will be well-suited for a knife. The terms "wear resistance" and "toughness" are used in a different context when talking about industrial applications. Sure, toughness can translate to bending your knife in a vice grip down to a 45 degree angle, but that's not the use that these manufacturers have in mind when they design these steels.

That said, K490 seems to have less wear resistance than CPM-M4, but more toughness. It looks like an interesting steel indeed. Wether we'll see it in the knife industry or not, I don't know; but, the reason it's not marketed as a knife steel is because it wasn't designed to be such a thing.
 
Blues Bender said:
Sure, toughness can translate to bending your knife in a vice grip down to a 45 degree angle, but that's not the use that these manufacturers have in mind when they design these steels.
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Aren't you describing lateral strength . . . the ability of the blade to bend without breaking or taking a set? I thought toughness had to do with impact resistance.

I'm so confused. :confused:
 
bld522 said:
Aren't you describing lateral strength . . . the ability of the blade to bend without breaking or taking a set? I thought toughness had to do with impact resistance.

I'm so confused. :confused:
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Yes, you're right. I can never get that darn terminology correct:D

I believe lateral strength is a balance between tensile strength, ductility, and toughness though. Maybe I'm wrong...Now I'm starting to confuse myself:D Either way, my point is that steel manufacturers design these steels for a different purpose than knives most times.
 
Bohler calls the steel their allround cold work tool steel.
One of the applications they mention are "industrial knives" whatever that might be ;)
 
I'd imagine "industrial knife" refers to a blade that might be used in some sort of assembly machine rather than one that folds and fits in your pocket or a kitchen knife of some sort. Not sure!
 
Looks like a great knife steel, but there are so many high-end steels out there right now that the full value of its advantages will be seen only in very specific applications.

K390 will offer a lot more wear resistance than K490. 3V will offer much more toughness than K490. But K490 appears to be fairly well balanced -- kind of like M4 with a bit less wear resistance and quite a bit more toughness. Sounds good to me.

I'm starting to feel sorry for D2.
 
Toughness can be used to refer to the impact resistance (or the energy required to fracture a specific size of sample in a specific test) it can also be used more generally to describe the resistance to brittle failure.

A full hard file in W2 is very strong, but not tough. If I put it in a vice and hit it with a hammer it can shatter, or conversely if I grind a v notch stress riser in it I can snap it off with my hands. Even though I'm not nearly strong enough to exceed its ultimate strength, I can easily take advantage of the stress riser and its magnifying effect on stress to cause a crack to form and propagate.

So in either case the steel was not very tough, even though it was very strong.
 
So what about spring steel and lateral strength? Is spring steels ability to resist deformation when bent considered toughness?

"Strength" isn't a commonly used term to describe blade steel, so I have trouble understanding the properties it lends when in use. From what I gather, toughness plays a role in strength BUT, I'm not a materials scientist:D
 
Blues Bender said:
So what about spring steel and lateral strength? Is spring steels ability to resist deformation when bent considered toughness?

"Strength" isn't a commonly used term to describe blade steel, so I have trouble understanding the properties it lends when in use. From what I gather, toughness plays a role in strength BUT, I'm not a materials scientist:D
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Strength gets talked about quite a bit. It's an important consideration.

https://en.m.wikipedia.org/wiki/Strength_of_materials

http://www.engineersedge.com/material_science/yield_strength.htm

https://en.m.wikipedia.org/wiki/Ultimate_tensile_strength

https://en.m.wikipedia.org/wiki/Compressive_strength


When you want to retain the apex of the edge (edge stability), and I mean keeping the apex angle as crisp as possible, strength, toughness, and wear resistance together are what need to be considered.

Strength keeps the apex from moving back and for before breaking off or crushing (denting or rolling). Generally Rockwell hardness is used to talk about it because the different types of strength correlate with hardness, but that's not the whole picture with strength.

Toughness keeps the apex from fracturing (chipping).

Abrasive wear resistance keeps the apex from blunting on abrasive materials.

Adhesive wear resistance keeps the whole steel mix together without pieces of the steel coming apart from galling (carbide tearout).

For an all purpose knife you ideally want all of these properties maxed out. When certain jobs cause failure of one of those traits more than another then you need to increase the property that's failing at the cost of the property you have an abundance of.

That's why a steel like A11 is so impressive to so many people. It has the right mix to cut soft, abrasive media for a long time. But it doesn't have much in the way toughness so it's not wise to stress the apex where fracturing may occur. But the same traits that make it so impressive to some people make the steel disappointing to others. It fractures too easily given the job. It's too wear resistant to sharpen easily, etc.

That's also why I like 4V/ Vanadis 4E a lot. It was made to have enough toughness for my uses, can get as hard as reasonably necessary, has enough carbide content to resist slow wear for a long time, and was made specifically to resist adhesive wear. All of those properties together of the steel itself combined with proper hardening and tempering cycles lead to a steel that does very well for my uses. In other words, it has high apex stability for the work I do.

But apex stability is subjective depending on what kind of work you do. People generally aren't honest enough with themselves about what they need and try to keep up with the joneses and they end up buying a knife that disappoints them given the job they're trying to accomplish or whatever.

In my feeble mind, 4v is half as likely to fracture as 10V and I need that for what I do with knives. 4V can also be more easily made to resist rolling than 3V while having ample ability to resist fracture and compression. It also has enough carbide content to cut a long time in abrasive media without being crazy with it. And it has the ability to keep the steel together without crumbling.
 
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bodog said:
Strength gets talked about quite a bit. It's an important consideration.

https://en.m.wikipedia.org/wiki/Strength_of_materials

http://www.engineersedge.com/material_science/yield_strength.htm

https://en.m.wikipedia.org/wiki/Ultimate_tensile_strength

https://en.m.wikipedia.org/wiki/Compressive_strength


When you want to retain the apex of the edge (edge stability), and I mean keeping the apex angle as crisp as possible, strength, toughness, and wear resistance together are what need to be considered.

Strength keeps the apex from moving back and for before breaking off or crushing (denting or rolling). Generally Rockwell hardness is used to talk about it because the different types of strength correlate with hardness, but that's not the whole picture with strength.

Toughness keeps the apex from fracturing (chipping).

Abrasive wear resistance keeps the apex from blunting on abrasive materials.

Adhesive wear resistance keeps the whole steel mix together without pieces of the steel coming apart from galling (carbide tearout).

For an all purpose knife you ideally want all of these properties maxed out. When certain jobs cause failure of one of those traits more than another then you need to increase the property that's failing at the cost of the property you have an abundance of.

That's why a steel like A11 is so impressive to so many people. It has the right mix to cut soft, abrasive media for a long time. But it doesn't have much in the way toughness so it's not wise to stress the apex where fracturing may occur. But the same traits that make it so impressive to some people make the steel disappointing to others. It fractures too easily given the job. It's too wear resistant to sharpen easily.
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Totally agreed.

There are plenty numbers of steel that look great on paper but wouldn't be that great on knife application.
 
Bodog, what do you think about K490

I believe impact energy unnotched in joule of K490 at 62RC is 80j while my beloved Vanadis 4E at 62RC has 50j.
Is this correct?
 
Thanks for the clarification Bodog.

Often times, I hear people talking about wear resistance, toughness, and corrosion resistance; strength is not mentioned often IMO. I know strength is a big part of material science, but I didn't know how it corresponded to knives.

I think I've been using the term "toughness" when I should have been using "strength" instead.
 
Neo said:
Bodog, what do you think about K490

I believe impact energy unnotched in joule of K490 at 62RC is 80j while my beloved Vanadis 4E at 62RC has 50j.
Is this correct?
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Personally I think it looks interesting but there are people here who have a far better knowledge and understanding. Hopefully they'll opine.
 
I think understanding the meaning of the various material properties is best started by looking at each property in isolation. Once the properties are understood separately, then one needs to combine them to develop an understanding of real world performance.

Strength correlates with hardness and reflects how much force a sample can withstand before suffering permanent deformation.

Toughness is essentially a measure of how much energy is required to cause brittle fracture.

Knives need a balance of these properties along with resistance to abrasive and adhesive wear.
 
Blues Bender said:
So what about spring steel and lateral strength? Is spring steels ability to resist deformation when bent considered toughness?

"Strength" isn't a commonly used term to describe blade steel, so I have trouble understanding the properties it lends when in use. From what I gather, toughness plays a role in strength BUT, I'm not a materials scientist:D
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"spring steel" is somewhat of a misnomer. Any steel will function as a spring as long as you don't exceed its yield strength. Spring steel is just a high strength steel that will move without taking a permanent set. People make knives out of car springs.

Strength vs. toughness-
Take a piece of wire and start bending it. At low loads you let go of it and it returns to its original shape. Pull it a little harder and it permanently deforms a little bit. You have exceeded its "yield strength". Pull it even farther and depending on the steel it will eventually break, this is its fracture strength or ultimate strength. The yield strength is easy to experience if you play with a piece of coathanger wire. The range of movement between initial yielding and ultimate fracture is the ductility. Ductility is pretty much what we mean by toughness, it bends a long way before it fractures. You won't fracture a piece of coathanger wire by bending it but you can fracture a higher strength steel that way.

If you test nice clean specimens, toughness has no affect on strength, they are separate things. But in the real world, for things whose shapes are not perfectly clean, toughness becomes more important. Someone mentioned grinding a notch in a file and breaking it easily. This is an example of material strength being compromised by low toughness. Knife blades are not always simple shapes. There are various places in a knife where strength can be compromised by low toughness.

There are numerous ways that toughness can be important to a blade. Some examples-
1) I saw pictures where someone was splitting a log with a blade and partway through the log the wood grain deviated and the blade ended up with a good bend in it. Without enough toughness the blade could break right there.
2) Someone could be putting a good load on their knife and it can yield. With good toughness it bends and doesn't break. They see that the knife is bending a little bit and they stop whatever they are doing but the knife is still intact. If the blade had low toughness it would have fractured right away.
3) Knives with significant defects become handicapped with low toughness steels. Things like sharp corners where the tang meets the blade can lead to early failure if the steel doesn't have enough toughness.
4) Bump a staple while cutting a cardboard box and you can bend a part of the edge. If the steel is low toughness then the edge would just chip. If the steel has good toughness then the edge bends but stays intact, and you can fix it.
 
bdmicarta said:
"spring steel" is somewhat of a misnomer. Any steel will function as a spring as long as you don't exceed its yield strength. Spring steel is just a high strength steel that will move without taking a permanent set. People make knives out of car springs.

Strength vs. toughness-
Take a piece of wire and start bending it. At low loads you let go of it and it returns to its original shape. Pull it a little harder and it permanently deforms a little bit. You have exceeded its "yield strength". Pull it even farther and depending on the steel it will eventually break, this is its fracture strength or ultimate strength. The yield strength is easy to experience if you play with a piece of coathanger wire. The range of movement between initial yielding and ultimate fracture is the ductility. Ductility is pretty much what we mean by toughness, it bends a long way before it fractures. You won't fracture a piece of coathanger wire by bending it but you can fracture a higher strength steel that way.

If you test nice clean specimens, toughness has no affect on strength, they are separate things. But in the real world, for things whose shapes are not perfectly clean, toughness becomes more important. Someone mentioned grinding a notch in a file and breaking it easily. This is an example of material strength being compromised by low toughness. Knife blades are not always simple shapes. There are various places in a knife where strength can be compromised by low toughness.

There are numerous ways that toughness can be important to a blade. Some examples-
1) I saw pictures where someone was splitting a log with a blade and partway through the log the wood grain deviated and the blade ended up with a good bend in it. Without enough toughness the blade could break right there.
2) Someone could be putting a good load on their knife and it can yield. With good toughness it bends and doesn't break. They see that the knife is bending a little bit and they stop whatever they are doing but the knife is still intact. If the blade had low toughness it would have fractured right away.
3) Knives with significant defects become handicapped with low toughness steels. Things like sharp corners where the tang meets the blade can lead to early failure if the steel doesn't have enough toughness.
4) Bump a staple while cutting a cardboard box and you can bend a part of the edge. If the steel is low toughness then the edge would just chip. If the steel has good toughness then the edge bends but stays intact, and you can fix it.
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Thanks for the very informative response, this is exactly what I was looking for.:thumbup::thumbup:
 
I know i am necro-threading...

But i find this is the second reference to k490 in knifemaking i have found except my stuff...
I've used it a bit the last year or two and find it very very good, my edc's i can have an edge at 7dps RC63... it gets minor roughness feeling damage doing things like hard whittling and cutting stuff with hard bits in it... chef's knives... i like it, but stock thickness is a pain. heat treat needs to be worked out for your system, but i am using low aus temps and low temper temps and that 30 min soak time seems about right... and cryo... it is pretty darn tough... It decarbs a lot so beware...
 
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