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- Oct 3, 1998
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Table of Contents:
I. What makes a steel perform?
A. Introduction
B. Sharpen for performance
C. Design for performance
D. Properties of performance steels
E. What's the "best steel"?
II. Elements of Steel
III. Steels
A. Non-stainless Steels
B. Stainless Steels
C. Damascus Steel
C. Non-steel used for cutler
IV. Selected URLs for steel information
V. Bibliography
I.WHAT MAKES A STEEL PERFORM?
A. Introduction
Steel is the heart of the blade. The search for higher-performance
steels has to a number of wonderful materials in recent years. Steel
by itself isn't the sole determiner of knife performance, of course.
Heat treatment, blade geometry, handle geometry and materials all
effect how a knife performs for a particular job. However, those
other qualities can be difficult to measure. You can't tell by
looking at it how well a blade has been heat-treated, and you can only
make educated guesses on how well the blade and handle geometry will
work. With steel, however, you can get a full listing of its alloying
elements, something measureable and somehow satisfying.
As a result, it's easy to fall into the trap of putting too much
emphasis on the steel itself. A knife is more than steel, and it's
important not to forget that. In addition, many modern steels perform
so well, that knife decisions can often be made based on other factors
than marginal increases in steel performance.
The question of "what's the best steel" or "rank the following steels
in order from best to worst" often comes up. The resulting replies
can never be totally accurate, because depending on the jobs the knife
will be used for, the blade geometry, and the quality of the heat
treat, what is "best" and what is "worst" can be very fluid. If you
want to make an educated decision about steels, try to learn the
basics of steel properties, and go from there.
B. Sharpening for performance
That doesn't mean that significant performance advantages can't be had
by choosing the right steel for the job. In fact, choosing a steel
can significantly impact the performance of a knife. But, to really
bring out the performance of a particular steel, you need to take
advantage of the better steel in your sharpening plan. If a weak,
brittle steel can perform the job when sharpened at
25-degrees-per-side, a strong, tough steel might give you some
marginal performance improvements if it, too, is sharpened at
25-degrees-per-side. However, to really bring out the performance of
the better steel, trying bringing it down to 20-degrees per side, or
less. The advantage of the better steel is that it is strong and
tough enough to hold up with a small edge angle -- and smaller edge
angles radically out-perform bigger edge angles. It's easy to get a
10-to-1 perform advantage for certain cutting jobs by cutting 5
degrees off your sharpening angle.
This leads to the general rule:
To really see the advantages of a better steel, exploit that
steel in your sharpening program. If you're going to sharpen
all your knives at the same angle regardless of steel, you
might de-emphasize steel choice somewhat.
On the internet, I'll often see someone posting about wanting to
upgrade from their ATS-34 folder to one that has S30V, and then in a
different post, declare that they sharpen all their knives at
20-degrees-per-side. Why spend all that extra money for S30V, just to
get some marginal wear resistance advantages but no other performance
advantages? If that same user would take advantage of S30V's superior
toughness and drop the edge angle to 15-degrees-per-side, they would
see a large leap in cutting performance, along with the extra wear
resistance. Because of choosing the right sharpening angle, the more
expensive S30V knife now gives an impressive return on investment.
*Now* you can see what all the fuss is about!
C. Design for performance
In the section above, we highlighted what the user can do to bring out
the best performance in a high-performance steel. But the user is
only half the equation; now we will look at what the knifemaker might
do with a higher- performance steel. As the knifemaker moves from one
steel to another, it is often possible to modify the design of a
particular knife to take advantage of the newer steel, and raise
performance.
For example, it is possible to make a hard-use "tactical/utility"
knife from ATS-34. To make sure the ATS-34 will take the kind of
stresses it might see in this environment, the edge might be left a
bit thick (sacrificing cutting performance), or the hardness brought
down a touch (sacrificing strength and wear resistance), or both. If
the same maker moves to much-tougher S30V, he might be able to thin
out the edge, thin out the entire knife, and raise the hardness,
bringing up performance as a whole. Moving to differentially-tempered
5160 might allow the maker to re-profile even more for performance.
If we're talking about a fighter, moving from 1095 to 3V might allow
the maker to make the knife much thinner, lighter, and faster, while
significantly increasing cutting performance and maintaining edge
integrity.
So to really take advantage of the higher-performance steel, we want
the knifemaker to adjust the knife design to the steel, wherever he
thinks it's appropriate. If a knifemaker offers the same knife in
multiple steels, ask about what the characteristics are in each steel,
and the how's and why's of where the design has changed to accomodate
each steel offered.
Note that there can be good reasons that a knifemaker might not change
the blade profile even though the steel has changed. Maybe he's
particularly good at heat-treating one steel or another, so that the
differences between disparate steels are minimized. Maybe the
higher-performance steel is not available in the next stock thickness
down. Maybe instead of higher cutting performance, the maker would
rather offer the same cutting performance but in a knife that can take
more abuse. Maybe his customers tend to only buy thicker knives
regardless of performance.
So work with the maker to understand the choices being made with the
different steels being offered. If you understand the kind of
performance you need, you'll be able to make a wise choice.
D. Properties of performance steels
What is it we're looking for in a steel, anyway? Well, what we are
looking for is strength, toughness, wear resistance, and edge
holding. Sometimes, we're also looking for stain resistance.
Wear resistance: Just like it sounds, wear resistance is the ability
to withstand abrasion. Generally speaking, the amount, type, and
distribution of carbides within the steel is what determines wear
resistance.
Strength: The ability to take a load without permanently
deforming. For many types of jobs, strength is extremely important.
Any time something hard is being cut, or there's lateral stress put on
the edge, strength becomes a critical factor. In steels, strength is
directly correlated with hardness -- the harder the steel, the
stronger it is. Note that with the Rockwell test used to measure
hardness in a steel, it is the hardness of the steel matrix being
measured, not the carbides. This, it's possible for a softer, weaker
steel (measuring low on the Rockwell scale) to have more wear
resistance than a harder steel. S60V, even at 56 Rc, still has more
and harder carbides than ATS-34 at 60 Rc, and thus the S60V is more
wear resistant, while the ATS-34 would be stronger.
Toughness: The ability to take an impact without damage, by which we
mean, chipping, cracking, etc. Toughness is obviously important in
jobs such as chopping, but it's also important any time the blade hits
harder impurities in a material being cut (e.g., cardboard, which
often has embedded impurities).
The knifemaker will be making a tradeoff of strength versus toughness.
Generally speaking, within the hardness range that the steel performs
well at, as hardness increases, strength also increases, but toughness
decreases. This is not always strictly true, but as a rule of thumb
is generally accurate. In addition, it is possible for different heat
treat formulas to leave the steel at the same hardness, but with
properties such as toughness, wear resistance, and stain resistance
significantly differing.
Stain resistance (rust resistance): The ability to withstand rust
(oxidation). Obviously, this property can be helpful in corrosive
environments, such as salt water. In addition, some types of
materials are acidic (e.g., some types of foods), and micro-oxidation
can lead to edge loss at the very tip of the edge, over a small amount
of time. In "stainless" cutlery steels, stain resistance is most
affected by free chromium -- that is, chromium that is not tied up in
carbides. So, the more chromium tied up in carbides, the less free
chromium there is, which means more wear resistance but less stain
resistance.
Edge holding: The ability of a blade to hold an edge. Many people
make the mistake of thinking wear resistance and edge holding are the
same thing. Most assuredly, it is not; or rather, it usually is not.
Edge holding is job-specific. That is, edge holding is a function of
wear resistance, strength, and toughness. But different jobs require
different properties for edge holding. For example, cutting through
cardboard (which often has hard embedded impurities), toughness
becomes extremely important, because micro-chipping is often the
reason for edge degradation. Whittling very hard wood, strength
becomes very important for edge-holding, because the primary reason
for edge degradation is edge rolling and impaction. Wear resistance
becomes more important for edge holding when very abrasive materials,
such as carpet, are being cut. And for many jobs, where corrosion-
inducing materials are contacted (such as food prep), corrosion can
affect the edge quickly, so corrosion resistance has a role to play
as well.
There are other properties that significantly effect how a steel
performs:
Ability to take an edge: Some steels just seem to take a much sharper
edge than other steels, even if sharpened the exact same way.
Finer-grained steels just seem to get scary sharp much more easily
than coarse-grained steels, and this can definitely effect
performance. Adding a bit of vanadium is an easy way to get a
fine-grained steels. In addition, an objective of the forging process
is to end up with a finer-grained steel. So both steel choice, and
the way that steel is handled, can effect cutting performance.
Manufacturing process: Cleaner, purer steels perform better than
dirtier, impure steels. The cleaner steel will often be stronger and
tougher, having less inclusions. High quality processes used to
manufacture performance steel include the Argon/Oxygen/Decarburization
(AOD) process, and for even purer steel, the Vacuum Induction
Melting/Vacuum Arc Remelting (VIM/VAR) process, often referred to as
"double vacuum melting" or "vacuum re-melting".
Edge toothiness: Some steels seem to cut aggressively even when razor
polished. For these steels, even when they're polished for
push-cutting, their carbides form a kind of "micro serrations" and
slice aggressively.
E. What's the "best steel".
Understanding these properties will get you started to fundamentally
understanding steels and how choice of steel can effect performance.
I often see people asking, "what's the best steel"? Well, the answer
depends so much on what the steel is being used for, and how it's
heat-treated, that the questioner can never possibly get an accurate
answer. For a knife lover, it's worth spending a little time
understanding steel properties -- only by doing so well he really
understand what the "best steel" might be for his application.
Putting it all together, you can see how these properties might
determine your steel choice. To pick on S60V and ATS-34 again, there
seems to be a feeling that S60V is "better" in some absolute sense
than ATS-34. But S60V is often left very soft, around 55-56 Rc, to
make up for a lack of toughness. Even left that soft, an abundance of
well-distributed vanadium carbides gives S60V superior wear resistance
to ATS-34, at acceptable toughness levels. However, does that mean
S60V is "better" than ATS-34? Well, many users will find edge rolling
and impaction the primary causes of edge degradation for everyday use.
For those users, even though S60V is more wear-resistant, S60V is also
so soft and weak that they will actually see better edge retention
with ATS-34! The S60V user can leave the edge more obtuse (raise the
sharpening angle) to put more metal behind the edge to make it more
robust, but now the S60V will suffer serious cutting performance
disadvantages versus the thinner ATS-34 edge.
So, the next general rule:
Knowing the uses you'll put your knife to, and exactly how
those uses cause edge degradation, will allow you to make a
much better choice of steel, if you generally understand steel
properties.
The properties of different steels will be laid out below. But in
your search for the knife with the "best steel" for your uses, I
always suggest you ask the makers of the knives you're considering
which steels they would use. The knifemaker will usually know which
steels he can make perform the best. And as pointed out above, heat
treat is absolutely critical to bringing out the best in a steel. A
maker who has really mastered one particular steel (e.g., Dozier and
D-2) might be able to make that steel work well for many different
uses. So never go just by charts and properties; make sure you also
consider what the knifemaker can do with the steel.
I. What makes a steel perform?
A. Introduction
B. Sharpen for performance
C. Design for performance
D. Properties of performance steels
E. What's the "best steel"?
II. Elements of Steel
III. Steels
A. Non-stainless Steels
B. Stainless Steels
C. Damascus Steel
C. Non-steel used for cutler
IV. Selected URLs for steel information
V. Bibliography
I.WHAT MAKES A STEEL PERFORM?
A. Introduction
Steel is the heart of the blade. The search for higher-performance
steels has to a number of wonderful materials in recent years. Steel
by itself isn't the sole determiner of knife performance, of course.
Heat treatment, blade geometry, handle geometry and materials all
effect how a knife performs for a particular job. However, those
other qualities can be difficult to measure. You can't tell by
looking at it how well a blade has been heat-treated, and you can only
make educated guesses on how well the blade and handle geometry will
work. With steel, however, you can get a full listing of its alloying
elements, something measureable and somehow satisfying.
As a result, it's easy to fall into the trap of putting too much
emphasis on the steel itself. A knife is more than steel, and it's
important not to forget that. In addition, many modern steels perform
so well, that knife decisions can often be made based on other factors
than marginal increases in steel performance.
The question of "what's the best steel" or "rank the following steels
in order from best to worst" often comes up. The resulting replies
can never be totally accurate, because depending on the jobs the knife
will be used for, the blade geometry, and the quality of the heat
treat, what is "best" and what is "worst" can be very fluid. If you
want to make an educated decision about steels, try to learn the
basics of steel properties, and go from there.
B. Sharpening for performance
That doesn't mean that significant performance advantages can't be had
by choosing the right steel for the job. In fact, choosing a steel
can significantly impact the performance of a knife. But, to really
bring out the performance of a particular steel, you need to take
advantage of the better steel in your sharpening plan. If a weak,
brittle steel can perform the job when sharpened at
25-degrees-per-side, a strong, tough steel might give you some
marginal performance improvements if it, too, is sharpened at
25-degrees-per-side. However, to really bring out the performance of
the better steel, trying bringing it down to 20-degrees per side, or
less. The advantage of the better steel is that it is strong and
tough enough to hold up with a small edge angle -- and smaller edge
angles radically out-perform bigger edge angles. It's easy to get a
10-to-1 perform advantage for certain cutting jobs by cutting 5
degrees off your sharpening angle.
This leads to the general rule:
To really see the advantages of a better steel, exploit that
steel in your sharpening program. If you're going to sharpen
all your knives at the same angle regardless of steel, you
might de-emphasize steel choice somewhat.
On the internet, I'll often see someone posting about wanting to
upgrade from their ATS-34 folder to one that has S30V, and then in a
different post, declare that they sharpen all their knives at
20-degrees-per-side. Why spend all that extra money for S30V, just to
get some marginal wear resistance advantages but no other performance
advantages? If that same user would take advantage of S30V's superior
toughness and drop the edge angle to 15-degrees-per-side, they would
see a large leap in cutting performance, along with the extra wear
resistance. Because of choosing the right sharpening angle, the more
expensive S30V knife now gives an impressive return on investment.
*Now* you can see what all the fuss is about!
C. Design for performance
In the section above, we highlighted what the user can do to bring out
the best performance in a high-performance steel. But the user is
only half the equation; now we will look at what the knifemaker might
do with a higher- performance steel. As the knifemaker moves from one
steel to another, it is often possible to modify the design of a
particular knife to take advantage of the newer steel, and raise
performance.
For example, it is possible to make a hard-use "tactical/utility"
knife from ATS-34. To make sure the ATS-34 will take the kind of
stresses it might see in this environment, the edge might be left a
bit thick (sacrificing cutting performance), or the hardness brought
down a touch (sacrificing strength and wear resistance), or both. If
the same maker moves to much-tougher S30V, he might be able to thin
out the edge, thin out the entire knife, and raise the hardness,
bringing up performance as a whole. Moving to differentially-tempered
5160 might allow the maker to re-profile even more for performance.
If we're talking about a fighter, moving from 1095 to 3V might allow
the maker to make the knife much thinner, lighter, and faster, while
significantly increasing cutting performance and maintaining edge
integrity.
So to really take advantage of the higher-performance steel, we want
the knifemaker to adjust the knife design to the steel, wherever he
thinks it's appropriate. If a knifemaker offers the same knife in
multiple steels, ask about what the characteristics are in each steel,
and the how's and why's of where the design has changed to accomodate
each steel offered.
Note that there can be good reasons that a knifemaker might not change
the blade profile even though the steel has changed. Maybe he's
particularly good at heat-treating one steel or another, so that the
differences between disparate steels are minimized. Maybe the
higher-performance steel is not available in the next stock thickness
down. Maybe instead of higher cutting performance, the maker would
rather offer the same cutting performance but in a knife that can take
more abuse. Maybe his customers tend to only buy thicker knives
regardless of performance.
So work with the maker to understand the choices being made with the
different steels being offered. If you understand the kind of
performance you need, you'll be able to make a wise choice.
D. Properties of performance steels
What is it we're looking for in a steel, anyway? Well, what we are
looking for is strength, toughness, wear resistance, and edge
holding. Sometimes, we're also looking for stain resistance.
Wear resistance: Just like it sounds, wear resistance is the ability
to withstand abrasion. Generally speaking, the amount, type, and
distribution of carbides within the steel is what determines wear
resistance.
Strength: The ability to take a load without permanently
deforming. For many types of jobs, strength is extremely important.
Any time something hard is being cut, or there's lateral stress put on
the edge, strength becomes a critical factor. In steels, strength is
directly correlated with hardness -- the harder the steel, the
stronger it is. Note that with the Rockwell test used to measure
hardness in a steel, it is the hardness of the steel matrix being
measured, not the carbides. This, it's possible for a softer, weaker
steel (measuring low on the Rockwell scale) to have more wear
resistance than a harder steel. S60V, even at 56 Rc, still has more
and harder carbides than ATS-34 at 60 Rc, and thus the S60V is more
wear resistant, while the ATS-34 would be stronger.
Toughness: The ability to take an impact without damage, by which we
mean, chipping, cracking, etc. Toughness is obviously important in
jobs such as chopping, but it's also important any time the blade hits
harder impurities in a material being cut (e.g., cardboard, which
often has embedded impurities).
The knifemaker will be making a tradeoff of strength versus toughness.
Generally speaking, within the hardness range that the steel performs
well at, as hardness increases, strength also increases, but toughness
decreases. This is not always strictly true, but as a rule of thumb
is generally accurate. In addition, it is possible for different heat
treat formulas to leave the steel at the same hardness, but with
properties such as toughness, wear resistance, and stain resistance
significantly differing.
Stain resistance (rust resistance): The ability to withstand rust
(oxidation). Obviously, this property can be helpful in corrosive
environments, such as salt water. In addition, some types of
materials are acidic (e.g., some types of foods), and micro-oxidation
can lead to edge loss at the very tip of the edge, over a small amount
of time. In "stainless" cutlery steels, stain resistance is most
affected by free chromium -- that is, chromium that is not tied up in
carbides. So, the more chromium tied up in carbides, the less free
chromium there is, which means more wear resistance but less stain
resistance.
Edge holding: The ability of a blade to hold an edge. Many people
make the mistake of thinking wear resistance and edge holding are the
same thing. Most assuredly, it is not; or rather, it usually is not.
Edge holding is job-specific. That is, edge holding is a function of
wear resistance, strength, and toughness. But different jobs require
different properties for edge holding. For example, cutting through
cardboard (which often has hard embedded impurities), toughness
becomes extremely important, because micro-chipping is often the
reason for edge degradation. Whittling very hard wood, strength
becomes very important for edge-holding, because the primary reason
for edge degradation is edge rolling and impaction. Wear resistance
becomes more important for edge holding when very abrasive materials,
such as carpet, are being cut. And for many jobs, where corrosion-
inducing materials are contacted (such as food prep), corrosion can
affect the edge quickly, so corrosion resistance has a role to play
as well.
There are other properties that significantly effect how a steel
performs:
Ability to take an edge: Some steels just seem to take a much sharper
edge than other steels, even if sharpened the exact same way.
Finer-grained steels just seem to get scary sharp much more easily
than coarse-grained steels, and this can definitely effect
performance. Adding a bit of vanadium is an easy way to get a
fine-grained steels. In addition, an objective of the forging process
is to end up with a finer-grained steel. So both steel choice, and
the way that steel is handled, can effect cutting performance.
Manufacturing process: Cleaner, purer steels perform better than
dirtier, impure steels. The cleaner steel will often be stronger and
tougher, having less inclusions. High quality processes used to
manufacture performance steel include the Argon/Oxygen/Decarburization
(AOD) process, and for even purer steel, the Vacuum Induction
Melting/Vacuum Arc Remelting (VIM/VAR) process, often referred to as
"double vacuum melting" or "vacuum re-melting".
Edge toothiness: Some steels seem to cut aggressively even when razor
polished. For these steels, even when they're polished for
push-cutting, their carbides form a kind of "micro serrations" and
slice aggressively.
E. What's the "best steel".
Understanding these properties will get you started to fundamentally
understanding steels and how choice of steel can effect performance.
I often see people asking, "what's the best steel"? Well, the answer
depends so much on what the steel is being used for, and how it's
heat-treated, that the questioner can never possibly get an accurate
answer. For a knife lover, it's worth spending a little time
understanding steel properties -- only by doing so well he really
understand what the "best steel" might be for his application.
Putting it all together, you can see how these properties might
determine your steel choice. To pick on S60V and ATS-34 again, there
seems to be a feeling that S60V is "better" in some absolute sense
than ATS-34. But S60V is often left very soft, around 55-56 Rc, to
make up for a lack of toughness. Even left that soft, an abundance of
well-distributed vanadium carbides gives S60V superior wear resistance
to ATS-34, at acceptable toughness levels. However, does that mean
S60V is "better" than ATS-34? Well, many users will find edge rolling
and impaction the primary causes of edge degradation for everyday use.
For those users, even though S60V is more wear-resistant, S60V is also
so soft and weak that they will actually see better edge retention
with ATS-34! The S60V user can leave the edge more obtuse (raise the
sharpening angle) to put more metal behind the edge to make it more
robust, but now the S60V will suffer serious cutting performance
disadvantages versus the thinner ATS-34 edge.
So, the next general rule:
Knowing the uses you'll put your knife to, and exactly how
those uses cause edge degradation, will allow you to make a
much better choice of steel, if you generally understand steel
properties.
The properties of different steels will be laid out below. But in
your search for the knife with the "best steel" for your uses, I
always suggest you ask the makers of the knives you're considering
which steels they would use. The knifemaker will usually know which
steels he can make perform the best. And as pointed out above, heat
treat is absolutely critical to bringing out the best in a steel. A
maker who has really mastered one particular steel (e.g., Dozier and
D-2) might be able to make that steel work well for many different
uses. So never go just by charts and properties; make sure you also
consider what the knifemaker can do with the steel.