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Hardness, Edge Retention and S30V
- Thread starter Confederate
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Inclusions are sulfides or oxides that are found in steel. Normally we don't want them as they cause brittleness. One exception is a free machining grade where we intentionally add sulfides which act as chip breakers when machining.....There are certain words which are used both by layman and scientists and this causes confusion. In the scientific terms metal has atoms, crystals,grains and metallic bonds ...There are three types of primary bonds : metallic, [metals] ,molecular or covalent [plastics] and ionic [ salt ,NaCl crystals] ....An atom is just that , an atom .When we combine them we can get molecules or crystals. Oxygen -one is an oxygen atom .Put two together you get O2 the oxygen molecule. Iron ,one is an atom, 9 or 14 will give you a crystal.....Frank, Talonite is not steel ! It's a cobalt alloy. While the wear resistance of Talonite is high it's edge will more easily roll over because the matrix is soft. S30V edge will resist roll over better. For wear resistance [edge retention] we need hard matrix and carbides. For impact [ax, machete, kukri ] we need toughness.Nickel as found in L-6 adds toughness. For prying we need strength .
Which isn't really helpful, unless you say, why. To say it with the fewest words possible: I wouldn't by a car in yellow..... .
I am sure your statement is somehow connected to performance, but unless you say, what experiences you have made with that type steel at that hardness, or what type of performance you expect and why, it isn't exactly adding to the discussion, is it?
dantzk8
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mete,
I have there an issue with the vocabulary. You only associate "edge retention" with "wear resistance" (i understand against abrasion). I thought it was in association too with toughness (against chipping), with strength (against rolling), with stain resistance (against rust). Do i misuse the words "edge retention"? Thanks to enlighten my bad english.
dantzk.
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OK, i wouldn´t buy anything in blue mood
and maybe, if i regret yellow cars it may be considered to personal preferences. But anybody would think twice about cars, that weight 1.5 tons with less tahn 100 PS performance (please excuse, i don´t know the right words considering cars an motors).Well it is much easier to say so, than to repeat all the things, that have been already said about hard carbides embedded in soft matrix or to remind the things about CPM 420 used in the Spyderco Military (dropped down to HRC 56 and than changed the steel grade).
If someone really dropps that kind of steel grade down to HRC56, it is just a dejá vu.
No, mete actually said in his post that edge retention needs "hard matrix and carbides". The hard matrix will give the strength against rolling (in part the carbides and precipitated particles suspended in the matrix will add hardness and strength through secondary hardening as well, but that is another degree of complexity). The carbides will add wear resistance. Toughness will only play a role for edge retention in certain applications. It will hardly matter for a paring knife, while it becomes increasingly important for a big chopper. That corrosion resistance is a factor for edge retention in a wet climate goes without saying. Obviously, an edge won't last if it rusts away, but that doesn't usually need to be pointed out.
not relating to this particular question...
while this is generally true...
it is sometimes different.
There are many factors regarding steel: chemical elements, heat treat history, steel production process... that can affect final result.
IMHO, the thing one should remember about steel is that it is a largely empirical subject, so extrapolations are not always right.
and appying those at highly subjective characteristics like "edge retention" or "performance in the field", makes it even worst.
dantzk8
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As some article (sorry can't find it back) edge is lost by:
* rolling
* wear
* chipping (or micro chipping)
rolling appears on too soft steel
wear can't be avoided but is countered by... wear resistance... which is related to hardness to some point (but not exclusively) ...
chipping is generally a by product of shocks and/or too high hardness for application.
* rolling
* wear
* chipping (or micro chipping)
rolling appears on too soft steel
wear can't be avoided but is countered by... wear resistance... which is related to hardness to some point (but not exclusively) ...
chipping is generally a by product of shocks and/or too high hardness for application.
dantzk8
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Somes articles i've read and from experience, i would say:
Abrasion. A one you can't avoid.
Rolling. Lack of strength.
Chipping, cracking. Lack of toughness.
Rust. A one which may happen even if you don't use the knife.
dantzk.
You can factor in toughness in a different way as well. Toughness and what I would call "micro-toughness" will in general allow a thinner edge geometry and the thinner edge geometry will in turn improve "edge holding". But if you take the term "edge holding" literally, this is actually not quite correct. The thinner geometry will not improve edge holding, but you have more room for edge degradation till you reach unacceptable bluntness. So I was comparing edges at the same edge geometry.
Ok, a slightly unconventional explanation:
Except for the noble gases all atoms have fewer electrons than they would like. To remedy the shortcoming they share electrons. For example hydrogen (H) would like to have two electrons, but has only one. Oxygen (O) has 6 electrons, but would like to have 8. So they form a bond in which they share the electrons. In order to satisfy the O's demand you need two more electrons, which it gets by sharing two of his with the H's, and so you have H2O. In this sharing of the electrons, the electrons belong most definitely either to one of the Hs or to the O. Even when you have water with lots of H2O, the electrons always belong strictly to one H2O unit. Two H2O units never exchange electrons. The H2O unit is a molecule and the sharing of the electrons between the definite members of that molecule form a covalent bond. The covalent bond tends to be the strongest of the chemical bonds (there are always exception but as a general trend), but it acts only within one molecule. The forces that bond different molecules together are generally very weak (polymers are a different class. Even though covalent bonds are the ones that hold polymers together, they should be considered as a unique class). This is why at room temperature water is a liquid.
There is a different way of satisfying the shortage of electrons: The "communistic" approach
. In this case, instead of finding a definitive partner to share its electrons with, many atoms donate their electrons to a common pool which is accessible to all atoms. So the individual atoms can pretend as if they all had as many electrons as they like, because they are surrounded by a whole host of common electrons. The bond forms because the atoms can not leave the community as they would then have to leave with fewer electrons than they would like. So many atoms are held together in a lattice of equally strong bonds. That is the basis of the metallic bond. If a lattice is regular and little deformed without gaps or irregular "stuff" in it, the lattice forms a crystal. A metal can consist of many little crystals, each regular, but in between a regular section are breaks in the regularity. This is a polycrystalline material (most common occurrences of metals are like that). If the entire chunk consists of a single regular lattice, it is a single crystalline material (pretty difficult to get a sizable chunk like that).This has certain consequences. 1) Except for some oddballs, all metals are solid at room temperature, because the metallic bond is fairly strong and extends over the entire lattice bonding many, many atoms together. 2) The electrons are pretty much free to move, as long as they don't bunch together or leave the lattice, which implies that metals are conductors. 3) The atoms in the lattice have designated "favorite" places, but since they are always surrounded by electrons, they have a lot of latitude to move a bit in their position or even exchange positions (it is not so much that two atoms switch position, but rather that a whole row of atoms can "move one over"). This give metals great ductility, the ability to bend and deform without breaking.
Hope that helps a little bit.
Hob, thank you for your excellent and easily understandable explanations. it is satisfying to me to now understand a little better, the properties of steel that this great thread is about. if you are not already an educator by profession, you certainly could be. roland
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Well, how is S30V in toughness and strength? If it has a tendancy to chip, it must be brittle to a point. I've also noticed that longish blades aren't made from S30V. Is this because of cost or the fact that it can't take impact?
As with anything else, there are subjective views and objective views. People tend to regard knife blades differently. Some people turn their noses up at 440A; others think it's a good choice for an all around blade. Some think their Buck 110s with 420HC are imbued with an almost mystic quality, while others wonder why it's praised more than 440C or AUS8. Many believe their Sebenzas are the best knives they've ever carried, while others find their performance somewhat lackluster. Cliff Stamp, for example, found that for optimum cutting, the edge of the S30V blade in the small Sebenza had to be reprofiled to ten degrees, but that with this vastly increased performance, the edge was so thin as to limit the cutting jobs it was able to do. Indeed, he found that S30V was capable of being ground to very fine edges, but that while the cutting performance improved, the blade's toughness was redulced. His reviews of the various blade steels also were at odds to many of the subjective reports I've read on this forum. ("Direct comparisons have also been done and found that S30V [in] a small Sebenza...to be less durable than 425mod, and another judges a small Sebenza in S30V comparable [to] AUS-6A." The latter observation, by Sodak, notes that "Fit and finish [on the Sebenza] are great, but it gets a lousy edge and holds it about as long as AUS 6." This is, however, one opinion and based on the possibility that Sodak's knife may not have been adequately heat treated.)
Regarding the stats on the Kershaw, I suppose there's no way to tell when buying on eBay whether you're getting a new knife hardened to 57-59, or one hardened to a lower Rockwell. (I wonder why they don't shoot for a 58-60?) The Kershaws, I've heard, have thin-styled blades. This leads me to think that S30V, for all of its state-of-the-art characteristics, really is geared towards very fine cutting jobs. It's not exactly what one would choose to cut carpet with, right?
As with anything else, there are subjective views and objective views. People tend to regard knife blades differently. Some people turn their noses up at 440A; others think it's a good choice for an all around blade. Some think their Buck 110s with 420HC are imbued with an almost mystic quality, while others wonder why it's praised more than 440C or AUS8. Many believe their Sebenzas are the best knives they've ever carried, while others find their performance somewhat lackluster. Cliff Stamp, for example, found that for optimum cutting, the edge of the S30V blade in the small Sebenza had to be reprofiled to ten degrees, but that with this vastly increased performance, the edge was so thin as to limit the cutting jobs it was able to do. Indeed, he found that S30V was capable of being ground to very fine edges, but that while the cutting performance improved, the blade's toughness was redulced. His reviews of the various blade steels also were at odds to many of the subjective reports I've read on this forum. ("Direct comparisons have also been done and found that S30V [in] a small Sebenza...to be less durable than 425mod, and another judges a small Sebenza in S30V comparable [to] AUS-6A." The latter observation, by Sodak, notes that "Fit and finish [on the Sebenza] are great, but it gets a lousy edge and holds it about as long as AUS 6." This is, however, one opinion and based on the possibility that Sodak's knife may not have been adequately heat treated.)
Regarding the stats on the Kershaw, I suppose there's no way to tell when buying on eBay whether you're getting a new knife hardened to 57-59, or one hardened to a lower Rockwell. (I wonder why they don't shoot for a 58-60?) The Kershaws, I've heard, have thin-styled blades. This leads me to think that S30V, for all of its state-of-the-art characteristics, really is geared towards very fine cutting jobs. It's not exactly what one would choose to cut carpet with, right?