KNIFE BLADE STEEL TYPES
How To Choose The Right Blade Steel
There are many different types of steel available for knife blades. The first
thing to do before you purchase a knife is determine how it will be used. Is it
going to be a collector piece? Are you going to use it for hunting purposes?
Will it be used around salt water when cleaning fish? Will it serve as a general
purpose pocket knife? The reason that there are so many different types of blade
steel is because it is not a “one size fits all” proposition. It is suggested to
research the different blade steels that are available to find the one that is
best suited for your intended use. And remember… the blade is where the work is
done so choose wisely!
The Making & Shaping of Steel
Steel is essentially a combination of iron and carbon. All steels contain
certain other elements in small controlled amounts, like Manganese, Sulfur,
Silicon, and Phosphorus. If nothing else is present, the steel is referred to as
plain carbon steel. Steels used for knife blades are enhanced with additional
elements and are called alloy steels. It is these additions that give different
types of steel their special properties. Alloy steels that have additions to
make them corrosion-resistant are labeled stainless steels, and these are the
steels most frequently used in making knife blades.
The making of stainless steel begins by melting steel in a furnace. Alloying
elements are added to the melt, and the molten steel is poured into molds called
ingots. Once the ingots have solidified, they are processed in a mill to make
usable shapes and sizes such as plates and coils. Plates are turned into knife
components by laser cutting and coils are shaped into components using a fine
Properties of Steel
The selection of steel for specific applications is based on the properties of
the steel and other factors like manufacturability—if the steel is difficult to
fabricate, then it is not practical for use in a manufacturing environment.
These properties are established by the alloys added to steel and by the methods
used in its manufacture.
Some of the important properties of blade steel are:
Hardness: A measure of the steel's ability to resist permanent deformation
(measured on a Rockwell Scale)
Hardenability: The ability of a steel to be hardened (through the
Strength: The steel’s ability to resist applied forces
Ductility: The steel's ability to flex or bend without fracturing
Toughness: The steel’s ability to absorb energy prior to fracturing
Initial Sharpness: The sharpness of the blade "out of the box"
Edge Retention: The ability of the steel blade to hold an edge without
Corrosion Resistance: The ability of the steel to resist deterioration as a
result of reaction with its environment
Wear Resistance: The ability to resist wear and abrasion during use
Manufacturability: The ease with which steel can be machined, blanked,
ground, and heat-treated (made into a blade)
Since no single material
is superior in all property categories, manufacturers select materials that
offer the optimum properties for the purpose intended.
The nomenclature used to describe the types of steel and their properties is
often derived from the internal structure of metals. As steel is heated and
cooled, its internal structure undergoes changes. The structures formed during
these changes are given names like Austenite and Martensite. Martensite is a
very hard structure that can be formed by rapidly cooling certain types of steel
during heat-treating. Steels that are capable of forming Martensite are called
martensitic steels, and it is this type of steel that is of most interest to the
cutlery industry. S30V, BG-42, 154CM and 420HC are all martensitic stainless
The properties of steel can be altered by the addition of certain elements to
the steel during the melting process. The alloying elements that are important
to knife-making are listed with a brief description of how they affect the
Carbon - is not an alloying element since it is present in plain carbon
steels. Nonetheless, increasing carbon increases hardness.
Chromium - improves hardenability, wear resistance, and corrosion
resistance. It is a major element in martensitic stainless steels, which are
most commonly used for sports cutlery applications.
Molybdenum - improves hardenability, tensile strength, and corrosion
resistance, particularly pitting.
Nickel - improves toughness, hardenability and corrosion resistance.
Nickel is a major element in Austenitic stainless steel that is sometimes used
for dive knives.
Vanadium - improves hardenability and promotes fine grains. Grain
structure in steels is another important factor in wear resistance and strength.
Generally, fine grain structures are desirable.
Some Popular Types of Steel
A. Non-stainless Steels (carbon, alloy, and tool steels):
· A2 Tool Steel is a high carbon steel that is very tough and abrasion
resistant. It responds very well to cryogenic treatment (see Knife Terminology)
for maximum edge retention.
· 10-series -- 1095 (and 1084, 1070, 1060, 1050, etc.) Many of the
10-series steels for cutlery, though 1095 is the most popular for knives. When
you go in order from 1095-1050, you generally go from more carbon to less, from
more wear resistance to less wear resistance, and tough to tougher to toughest.
As such, you'll see 1060 and 1050, used often for swords. For knives, 1095 is
sort of the "standard" carbon steel, not too expensive and performs well. This
is a simple steel, which contains only two alloying elements: .95% carbon and
.4% manganese. 1095 High Carbon Tool Steel, is also known as “Cutlery Spring
Steel”. This steel is well known for its use in manufacturing commercial saw
blades and recognized for its cutting and edge holding ability. It hones to an
unbelievable edge (better than any stainless steel), retains its edge (better
than most stainless steels) , and easier to sharpen, (compared to stainless
steel). Be aware, this steel will discolor over time and is susceptible to rust.
It is recommended to keep the blade oiled, but discoloration and/or rust will
not affect blade performance.
· D-2 is sometimes called a "semi-stainless". It has a fairly high chrome
content (12%), but not high enough to classify it as stainless. It is more stain
resistant than the carbon steels mentioned above, however. It has excellent wear
resistance. D-2 is much tougher than the premium stainless steels like ATS-34,
but not as tough as many of the other non-stainless steels mentioned here. The
combination of great wear resistance, almost-stainlessness, and good toughness
make it a great choice for a number of knife applications.
· 5160 is a steel popular with forgers and it is popular now for a
variety of knife knowledges, but usually bigger blades that need more toughness.
It is essentially a simple spring steel with chromium added for hardenability.
It has good wear resistance, but is known especially for its outstanding
toughness. This steel performs well over a wide range of hardnesses, showing
great toughness when hardened in the low 50s Rc for swords, and hardened up near
the 60s for knives needing more edge holding.
B. Stainless Steels:
· 420 has a lower carbon content (<.5%) than the 440 series which makes
this steel extremely soft, and it doesn't hold an edge well. It is used often
for diving knives, as it is extremely stain resistant. Also used often for very
inexpensive knives. Outside salt water use, it is too soft to be a good choice
for a utility knife.
· 420HC is a stainless steel that provides excellent rust resistance, is
easy to re-sharpen and has good edge retention. It is a higher carbon version of
standard Type 420 martensitic stainless steel. The Carbon content, combined with
the high Chromium content, provides good abrasion resistance and edge-holding.
This steel is not to be confused with standard 420 stainless steel. 420HC is an
excellent general purpose knife steel and is roughly comparable to 440A.
· 440A, 440B and 440C steels are some of the most popular stainless
steels used today. The carbon content (and hardenability) of this stainless
steel goes up in order from A (.75%) to B (.9%) to C (1.2%). 440C is an
excellent, high-end stainless steel, usually hardened to around 56-58 Rc, very
tough and with good edge-holding at that hardness. All three resist rust well,
with 440A being the most rust resistant, and 440C the least. 440C is fairly
ubiquitous, and is generally considered a very good general-use stainless,
tougher and more stain resistant than ATS-34 but with less edge-holding and
weaker. If your knife is marked with just "440", it is probably the less
expensive 440A; if a manufacturer had used the more expensive 440C, he'd want to
advertise that. The general feeling is that 440A (and similar steels, see below)
is just good enough for everyday use, especially with a good heat treat . 440-B
is a very solid performer and 440-C is excellent.
· 425M and 12C27 are very similar to 440A. 425M has .5% carbon. 12C27 has
.6% carbon and is a Scandanavian steel that is used often in Finish puukkos and
Norwegian knives. 12C27 is said to perform very well when carefully heat
treated, due to its high purity. When done right, it may be a slighter better
choice than 440A and similar steels.
· AUS-6, AUS-8, AUS-10 (aka 6A 8A 10A) are Japanese stainless steels,
roughly comparable in carbon content to 440A (AUS-6, .65% carbon) and 440B
(AUS-8, .75% carbon) and 440C (AUS-10, 1.1% carbon). AUS-6 is used by Al Mar,
and is a competitor to low-end steels like 420J. Cold Steel's use of AUS-8 has
made it pretty popular, as heat treated by Cold Steel it won't hold an edge like
ATS-34, but is a bit softer (and therefore weaker) and tougher. 8A is a
competitor of middle-tier steels. AUS-10 has roughly the same carbon content as
440C but with slightly less chromium, so it should be a bit less rust resistant
but perhaps a bit tougher than 440C. It competes with higher-end steels, like
ATS-34 and above. All 3 steels have some vanadium added (which the 440 series
lacks), which will improve wear resistance and refines the grain for both good
toughness, and the ability to sharpen to a very keen edge. Many people have
reported that they are able to get knives using steels that include vanadium,
like 8A, sharper than they can get non-vanadium steels like ATS-34.
· ATS-34 and 154-CM stainless steels. ATS-34 was the hottest high-end
stainless in the 1990s. 154-CM is the original American version, but for a long
time was not manufactured to the high quality standards knifemakers expect, so
knifemakers switched over to ATS-34. CPM is again making high-quality 154-CM,
and some companies seeking to stick with American-made products are using it.
ATS-34 is a Hitachi product that is very, very similar to 154-CM. Normally
hardened to around 60 Rc, it holds an edge very well and is tough enough even at
that high hardness. Not as rust resistant as the 400 series above. Many custom
makers use ATS-34, and Spyderco (in their high-end knives) and Benchmade are
among the production companies that use it.
· VG-10 is another vanadium-containing high-end stainless steel. Due to
the vanadium content, VG-10 takes a killer edge, just like other vanadium steels
like BG-42 and AUS-8. VG-10 is also tougher and more rust-resistant than ATS-34,
and seems to hold an edge better.
· BG-42 is somewhat similar to ATS-34, with two major differences: It has
twice as much manganese as ATS-34, and has 1.2% vanadium (ATS-34 has no
vanadium), so look for significantly better edge-holding than ATS-34. The
addition of vanadium and the clean manufacturing process (VIM/VAR) also gives
BG-42 better toughness than ATS-34.
· S30V is an excellent blade steel. It is a high vanadium stainless steel
with even higher edge retention.
Steel makers follow a precise recipe to ensure that each time they make a
particular alloy it has correct properties. The recipes are known as
Specifications, and they specify the amount of each alloy. Each alloy recipe or
type is named according to a number convention. Martensitic stainless steels,
for example, have numbers like Types 410, 420, and 425.
What is Rockwell Hardness?
The hardness of steel or other metals is
usually measured on a scale called the "Rockwell Scale", this scale gives a
number value to the hardness. This number is preceded by the letters Rc (for
example Rc58). High numbers indicate harder material. If a knife is too "soft"
meaning it has too low a Rockwell hardness, it will probably not hold an edge
and will bend quite easily. If a knife is too "hard" meaning it has too high a
Rockwell hardness, it will probably be very brittle and difficult to re-sharpen.
When a knife is designed, it is important to determine from the beginning what
kind of hardness will be required for its ultimate purpose. This will affect the
choice of steel. Once the steel is chosen, a heat treatment sequence must be
devised to result in the exact hardness needed in the final knife. (See
“Rockwell Hardness Test” in the Knife Terminology section)
to see our selection of Damascus steel blade knives.
Damascus Steel Blades
Damascus steel blade knives are growing in popularity due
to their beautiful looks, functionality and nostalgia. Collectors are drawn to
the unique and very pleasing patterns that can be created with Damascus steel.
The usefulness of Damascus steel blade knives is very attractive as well. The
idea of welding layers of steel together can also be thought of as “laminated
steel”. This is much like the concept of laminating wood which produces a
stronger piece of material. Usually two or more different types of steel are
used in the layers so the characteristics of each type will contribute to the
necessary qualities that are desired for a high quality knife blade. A good
quality Damascus steel blade will have all of the necessary features to provide
a lifetime of excellent service… it can be sharpened to a very sharp edge, it
will hold an edge very well and it will be tough. If properly taken care of, a
good Damascus blade knife can be passed down from generation to generation.
Producing Damascus steel blade knives is very labor intensive and it takes about
20 hours to produce one of good quality.
Historians have found that Damascus steel, formally known
as Wootz steel, originated in Asia over two thousand years ago, (200 BC).
Damascus steel gained popularity throughout the Roman era and was commonly used
to make armor and weapons. Damascus steel regained its popularity in the mid
18th century when a Swedish scientist discovered that the original wootz steel
contained carbon as the dominant element in the ancient steel. Swedish companies
began reproducing Damascus steel on an industrial scale and began using Damascus
steel to make gun barrels. Thus, the first crucible steel manufacturing began in
How a Damascus Steel Blade is Made
There are various techniques that bladesmiths and blacksmiths use to create
Damascus knife blades. The following is a “snap shot” of a basic method for a
fixed blade knife:
Making the Billet:
The process is started with five pieces of steel. Two
high carbon pieces and three medium carbon pieces. (If forging a larger blade
such as a sword, seven pieces may be used instead of five.) The thick ness,
width and length of the pieces depends on the size of the blade that is being
made. One of the me dium carbon pieces is made longer in order to handle the
billet in the forge. Impurities are cleaned from the pieces of steel, then
sandwiched together with the two high carbon pieces between the medium car bon
pieces. The pieces are then tied together with wire or arc welded together on
the end. The wire or weld material is removed after the first forge weld.
The Welding Process:
The billet is placed in a forge and brought to a cherry
red color. It is then removed and covered with bo rax. The borax becomes fluid
on the hot steel and acts as a flux to help clean the steel and keep it from
oxidizing. The pieces are then hammered together with a hammer and anvil and/or
a mechanical ham mer.
Drawing, Cutting, Folding and Welding:
The piece is then drawn out to twice the original length.
Skill and care are very important at this step as the billet must be struck
properly to avoid splitting. The billet is struck straight down to draw it out
and not to "push" the steel out. The billet is heated several times during this
process. The billet is then cut in the middle, leaving a little material to keep
it together until the next weld. The billet is then turned on its side and
hammered enough to swell the center of the billet. This provides a convex
surface for welding. The billet is then folded back on itself. The billet is
covered with Borax again and heated to welding temperature and then welded.
The draw, cut, fold and weld process is repeated the
necessary number of times to achieve the desired number of layers. Starting with
5 pieces of steel, it requires 5, 6, or 7 times in order to obtain 160, 320 or
640 layers respectively. The more layers that there are, the more skill that is
required for a good look ing and high quality blade.
Next the billet is hammered or cut and ground into the
shape of the desired blade.
The blade is then heated to a orange-red color (1,400 to
1,500 degrees), then quenched in a quenching oil (sometimes a brine solution is
used). The blade is then tempered by slowly heating to around 400 degrees.
The blade is then sanded multiple times using finer and
finer grit. It is then polished and sharpened.
The blade is then dipped in an acid bath. The acid reacts
differently with the two steels which brings out the distinctive grain pattern.
to see our selection of Damascus steel blade knives.
The blade is now finished.