Choosing a Survival Knife
| Knife Sharpening
| Knife Steel Properties
| Knives and UK Law
| Knife Terminology
Confused about all those different steel references they give when
you're trying to decide on what knife to buy?
Firstly, what is steel? Well, Steel is an alloy of iron, with
carbon, which may contribute up to 2.1% of its weight. Various other
elements may be added to the steel alloy to affect different
properties, the main ones being:
- Strength – This represents the ability to
resist deforming when subject to stress and applied
- Hardness - Similar to strength this refers to
the ability to avoid any permanent deformations.
- Toughness - The ability to resist damage like
cracks or chips when being used in heavy duty
applications. This also defines the steel’s ability to
flex without breaking. Note that the stronger or harder
the steel the less tough it will probably be.
- Wear Resistance – This is the steel’s ability
to withstand wear and general abrasion during normal
- Corrosion/Rust Resistance - This is the
ability to resist corrosion such as rust caused by
external element. Note that a high resistance to
corrosion does involve a sacrifice in the overall edge
- Initial Sharpness – This is simply how sharp
the blade is when first used.
- Edge Retention - Represents how long the
blade will retain its sharpness and not require
"Stainless Steel" is a modern alloy developed in the
early 1900’s after metallurgists discovered that
chromium-iron alloys displayed superior corrosion resistance
to carbon steel alloys. Steels must
have at least 10% chromium (see below) in their content to
be called Stainless. Below this value, the alloy
steels will experience increasing corrosion rates and will
begin to rust in wet environments. The chromium forms
a protective self-healing oxide film, which is the reason
why this group of steels exhibits such corrosion resistance.
The ability of the oxide layer to heal itself means that the
steel is corrosion resistant, no matter how much of the
surface is removed.
Stainless steels may be classified by their crystalline structure
into three main types:
- Good to excellent corrosion resistance
- Can be work-hardened
- Easily machined and fabricated to tight tolerances
- Smooth surface finish that can be easily cleaned and
- Temperature resistance from cryogenic to high heat
stainless steel is the most widely used stainless alloy
group, accounting for up to 70% of all stainless steel
production. The alloy contains a minimum of 16% chromium.
Its versatility is in large part down to the fact that it
can be formed and welded with successful results.
Austenitic alloys are the 200 and 300 series of stainless steel.
The most common alloys are 304 and 316/316L. Type 201 is a general
purpose stainless alloy. 304 and 316/316L are commonly used for
- Good corrosion resistance
- High strength and toughness
- Cannot be work-hardened
- High machinability and workability to tight tolerances
- Smooth surface finish
stainless alloys exhibit lower corrosion resistance than
austenitic alloys due to a lower chromium content. These
alloys contain between 10.5% and 27% chromium. They contain
less than 0.10% carbon and are magnetic. The fact that they
can’t be hardened via heat treatment and don’t weld to a
high standard limits the use of these metals somewhat, but
they are still suitable for a wide range of applications.
Some of the 400 series of stainless steel are ferritic alloys,
including 409, 410s, 430 and 444.
- Good corrosion resistance
- Extreme strength and toughness
- Can be work-hardened
- High machinability and workability to tight tolerances
- Smooth surface finish
|Martensitic alloys contain lower amounts of chromium (between
12-14%) and are less corrosion resistant than austenitic and
ferritic alloys. It shares some characteristics with ferritic, but boasts higher levels of
carbon, up to a full 1%. This means that they can be tempered
and hardened and are thus highly useful in situations where the
strength of the steel is more important than its resistance to
400 series alloys, including 410, 420 and 440 are martensitic
stainless steel alloys.
Chemical Composition of
The chemical composition of a knife steel must be
balanced, not over alloyed and precise. The specification
tolerances must be tight in order to secure a high
consistent quality in the finished knife. Here is a list of common elements
used in knife steel production:
Carbon (C) - The main driver for hardness. Too
much carbon however makes it more difficult for the material
to produce martensite and thereby deep freezing is necessary
to achieve high hardness. The hardness is related to the
amount of carbon dissolved in the steel matrix. By tying up
chromium into carbides the carbon is indirectly decreasing
Chromium (Cr) - The main driver for corrosion
resistance. The corrosion resistance achieved is related to
the amount of Cr dissolved into the steel matrix and not
related to the nominal composition. Cr is also the main
driver for carbide formation.
Molybdenum (Mo) - Drives carbide formation and has
a small influence on hardness and corrosion resistance in
martensitic stainless grades.
Vanadium (V) - A strong carbide former. The
vanadium carbides are also very stable and do not dissolve
during heat treatment.
Manganese (Mn) - An important element, manganese aids the
grain structure, and contributes to hardenability. Also strength and
wear resistance. Improves the steel (e.g., deoxidizes) during the
steel's manufacturing (hot working and rolling). Present in most
cutlery steel except for A2, L-6, and CPM 420V.
Nickel (Ni) - Adds toughness. Present in L-6 and AUS-6 and
AUS-8. Nickel is widely believed to play a role in corrosion
resistance as well, but this is probably incorrect.
Nitrogen (N) - Hardness driver like carbon but
does not have the same negative effect on corrosion
resistance. Nitrogen is not commonly used in these
applications since it is difficult to achieve significant levels of nitrogen in
conventional steel production.
Sulphur (S) - Forms sulphide inclusions which have
a negative influence on the initiation of pitting corrosion.
Tungsten (W) - A carbide former, it increases wear
resistance. When combined properly with chromium or molybdenum,
tungsten will make the steel to be a high-speed steel. The
high-speed steel M2 has a high amount of tungsten. The strongest
carbide former behind vanadium.
Vanadium (V) - Contributes to wear resistance and
hardenability, and as a carbide former (in fact, vanadium carbides
are the hardest carbides) it contribute to wear resistance. It also
refines the grain of the steel, which contributes to toughness and
allows the blade to take a very sharp edge. A number of steels have
vanadium, but M2, Vascowear, and CPM T440V and 420V (in order of
increasing amounts) have high amounts of vanadium. BG-42's biggest
difference with ATS-34 is the addition of vanadium.
Manganese (Mn), Phosphorus (P) and Silicon (Si) -
These elements make no significant contributions. The
general rule is to keep these as low as possible.
The most important thing to remember is that hardness and
corrosion resistance are related to the composition of the
matrix after hardening, not the nominal chemical composition
of the steel. The excess amounts of these elements will form
large primary carbides during casting and will not add to
the hardness or corrosion resistance of the finished knife.
Primary carbides will make the knife more brittle and more
difficult to sharpen than a fine-grain steel knife at the
same hardness. The steels containing large primary carbides
will also cause very high tool wear for blanking tools,
making them unsuitable for blanking or stamping.
||Good corrosion resistance, excellent for water sports applications.
This alloy is a chromium-nickel-aluminium precipitation hardening
stainless steel with good edge retention. Great corrosion resistance
generally means a high chromium content, and this means knives made with
this steel will be a little harder to sharpen than blades with a lower
||Originally designed for jet engine fan blades, it is the precursor
to the Japanese made ATS-34. In recent years, this steel has made a
resurgence in the knife industry, offering good blade toughness, edge
holding capability and corrosion resistance. Fairly easy to resharpen.
||A hard, strong blade steel. This stainless steel is commonly used in
knife blades, and offers good corrosion resistance at a low cost. Decent
edge holding capabilities and fairly easy to resharpen, this steel is a
good balance of the most desirable traits for knife steel.
||A high carbon version of 420 steel, this steel combines the
excellent wear resistance of high carbon alloys with the corrosion
resistance of chromium stainless steels. The high carbon content makes
this steel harder to resharpen, but the trade-off is better edge holding
||A high carbon stainless steel, used in many production knives. A
good balance of edge retention, easy resharpening and corrosion
||A high chromium stainless steel which exhibits an excellent balance
of hardness and corrosion resistance. This steel takes a nice edge, and
is fairly easy to sharpen even for a novice.
||This is a plain carbon steel, which means it has low resistance to
corrosion, and low to medium edge retention. The benefit of this steel
is it's easy to sharpen, will take an extremely sharp edge and is
generally available at a low cost.
||A medium carbon, low alloy steel that hardens well. This steel is
ideally suited to blades with a very thick cross-section such as
tomahawks and axes. Extremely tough and impact resistant, this steel is
most often used on blades which are hafted and/or thrown.
||A very high carbon, chromium stainless steel with additional amounts
of molybdenum. This steel has good edge holding properties and high
corrosion resistance, but is more difficult to resharpen than lower
||A medium to high carbon stainless steel, this steel holds a good
edge and is particularly well suited for heavy, long blades that are
subjected to a lot of stress while chopping and hacking. It has good
edge retention, and is fairly easy to resharpen with decent corrosion
||A Japanese stainless steel, with superb toughness and good edge
holding capabilities. This steel is fairly easy to sharpen and generally
low cost with great corrosion resistance.
||A high carbon, low chromium stainless steel which has proven itself
to be the ultimate compromise between toughness and strength, edge
holding and resistance to corrosion.
||A Chinese steel; made by adding molybdenum and vanadium to the
5Cr13MoV It is similar to 5Cr15MoV, the hardness could be HRC 56-58. It
is widely used to make high-end scissors, folding knives and hunting
6CR12MoV It is also similar to 6Cr14MoV, 6Cr14 which are also created by
Ahonest Changjiang Stainless steel Co.,Ltd. They are produced as per
customers' requests. For 6Cr14MoV grade, the hardness could be HRC 60.
It is good at making razors, surgical instruments.
7CR13MoV The big difference between 7Cr13MoV and 7Cr17MoV is the content
of chromium. 7Cr13MoV has less tensile strength, hardness and resistance
to wear when compared with 7Cr17MoV.
7CR17MoV A Chinese stainless steel compared to 440A.
8CR13MoV A Chinese stainless steel tempered at the Rc56 to Rc58 range
and used in Spyderco's, Kershaw's, and other quality knife maker's
budget lines of knives. For example, Kershaw's Crown II is one of the
few "name brand steel" folders that can be had for under $20 (in 2013).
8CR13MoV is often talked about in terms of a high-end budget steel.
Early Byrd (the Spyderco budget line) 8CR13MoV knives were marked 440C,
but tests found that the steel was something entirely different from
American 440C. According to Sal Glesser, owner of Spyderco, this steel
was closer to AUS-8 (AUS8) than American 440C. 8CR13MoV is often
compared to AUS-8 and 440B, but it has slightly more Carbon.
8CR14MoV A Chinese steel with similar performance characteristics to
AUS-8. An excellent value priced steel for its performance.
9Cr18Mo A higher end Chinese stainless steel used mostly in high-end
barbering scissors and surgical tools.
14-4CrMo Manufactured by Latrobe Specialty Metals. A wear resistant,
martensitic stainless tool steel that exhibits better corrosion
resistance than type 440C stainless steel.
||This steel is very similar to AUS-8. It is manufactured in China and
has about 0.75% carbon content.
|| This is 440 steel with extra cobalt mixed in
to strengthen the blade. Has about 0.85% carbon.
||A high quality, bearing grade alloy with significantly increased
amounts of carbon and molybdenum content plus vanadium for improved edge
retention and strength. Easy to sharpen, with decent corrosion
||This low alloy, cutlery grade steel is superior to most other steels
due to its chemistry. Decent corrosion resistance with superior edge
retention make this a premium steel for knife blades. This steel is
exceptionally tough, and therefore harder to sharpen than most stainless
||This American made and engineered steel was created especially for
the knife industry. It is a powder made steel with uniform structure and
great corrosion resistance. Excellent edge retention and first rate
toughness make this steel one of the best all-around knife steels,
striking a balance between corrosion resistance, edge retention and
||This air hardened tool steel is sometimes called a "semi-stainless"
steel, because it contains 12% chromium. It offers decent corrosion
resistance with exceptional edge retention. It is harder to sharpen than
most, but can be finished to a high-polish shine.
||This steel is made from dissimilar steels folded or fused together
with heat. It is often acid etched, which brings out the different
steels in a striped pattern. Excellent toughness and edge holding
capabilities make it a great blade, but the cost of production is high.
Damascus is most often used in special applications like decorative
||Layers vary from 53-62
||This high-speed, tool grade steel is used primarily in cutting tools
in industrial applications. This is metal used to cut metal. With
excellent strength, enduring toughness and tremendous wear resistance,
this is some of the toughest steel used to make knife blades. The
trade-off for all this toughness is that this steel is hard to sharpen,
and it is highly susceptible to corrosion. All blades made from this
steel will have a corrosion resistant coating applied, to give good
corrosion resistance with such a tough steel.
||An Austrian made stainless steel, it is comparable to 440C in
performance. It offers good edge holding qualities with excellent
corrosion resistance, and fairly easy sharpening.
||This steel contains carbon along with high amounts of chromium,
molybdenum and vanadium. This steel is double tempered for hardness and
edge retention. It has excellent corrosion resistance, but is slightly
more difficult to sharpen.
||This stainless steel is made in Sweden. It is generally known as a
premium steel for knife blades, offering a good balance of corrosion
resistance, sharpenability and edge retention.
|San Mai III
||San Mai means "three layers". It is a term used when talking about
traditional Japanese swords and daggers. The laminated construction is
important because it allows the blade maker to combine different grades
of steel in a single blade. A high carbon centre layer provides the
strength and edge holding qualities, while the outer layers are lower
carbon steels, providing flexibility.
||Centre layer= 59 Outer layers= 57
||Developed for the aircraft industry for jet ball bearings, and used
in the medical industry for scalpels, this steel resists rust in the
worst of conditions while maintaining ample edge retention. Offering an
easy to maintain edge and excellent corrosion resistance, this steel is
ideal in knives used for water sports.