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The quality of the steel is the basis for achieving the maximum effectiveness and durability of a knife blade but in general of all cutting tools beyond knives, such as scissors, chisels, etc.
Depending on the type of knife and the performance required it is important to choose steel.
The availability of steel types is very large and today there are many retailers for knifemakers that offer the sale of bars and trajectories of different sizes and thicknesses.
The characteristic of the steel combined with an adequate hardening allows you to obtain a high-level blade or tool.
The knife, however in appearances a simple object requires to bring to a high level a high knowledge and expertise not only with regard to the technical ability to realize it or the aesthetic form.
Several times I have talked about the difference between a window knife and a knife to use, between a functional knife or a “modeling” knife, while always appreciating the high technical and production skills of some makers who go into artistic works except with the shape of a knife.
Returning to the choice of steel it is important that the steel is hard to maintain a sharp thread for a long time, but at the same time it is flexible enough to bend without breaking.
It is essential that it is also stainless, so that it has a good resistance to corrosion.
Steel alone of course is not enough to determine the performance of the blade, thermal treatment, blade geometry, geometry and handle construction, are determining factors to have a good product to achieve the intended purpose.
Unfortunately some qualities in a blade are difficult to identify in the choice to purchase because you can not recognize “on sight” the type of thermal treatment that has been done, but knowing the composition of the steel used you can have an idea of how you will result during use.
Steel
The term steel generically indicates a link between two main elements: iron and carbon. Other elements present in steel are manganese, phosphorus, sulfur, silicon and in smaller quantities nitrogen, aluminum and oxygen.
Iron is a metal element and its chemical symbol is Fe.
Carbon is a non-metallic element, C is its chemical symbol; it is the main binding element in steel alloys and its percentage content ranges between 0.002 and 2.1, in terms of weight (in most steels hardly exceeds 1).
Because it is a metal alloy, the steel has no chemical symbol, so it is not listed in the periodic table. There are many nomenclatures established by various organizations that regulate technical standards, composition of each league, property, etc.
Features
The basic characteristics are bestowed on the steel alloy from carbon. The intentional addition of additional elements such as nickel, chromium, molybdenum, manganese, titanium, boron, niobio and vanadium,changes the characteristics of steel.
Carbon and other elements act as hardening agents. By changing the quantity of elements in the alloy, you control the properties of thesteel:
- Hardenability
- Hardness
- Toughness
- Ductility
- Fragility
In addition, steel is renowned for being a durablemetal:
- Corrosion
- traction
- wear and tear
- heat
For example, a steel with a high carbon presence in the alloy will be harder, but at the same time less flexible than a steel with a low carbon percentage.
If the carbon percentage is more than 2.1, the alloy is called castiron.
Production
The production cycle of steel varies depending on the technologies used and the type of steel you want to achieve. We can divide steel production cycles into two categories:
- steel produced with blast furnace
- steel made with electric oven
In the first case the raw materials used are: ironore, coke and fondant.
Mixing and blending these elements results separately cast iron and other subelements. Next, scrap iron and other elements are added to modify the mixture, so that a steel casting with the desired characteristics is obtained.
The cast steel is cut, reduced into large “blocks” (called blumas or slabs) that are then rolled (i.e. deformed) to be transformed into sheets, ribbons, pipes, bars, profiles, etc.
Currently, only three blast furs remain in operation in Italy: Taranto, Piombino and Trieste.
In the electric oven, on the other hand, the iron scrap is melted along with other elements and you get various semi-finished (billets, rodela, etc.) that can then be rolled hot orcold.
Resistance to wear and edge
Wear resistance means the ability to sustain abrasions during use.
Generally speaking, the quantity, type and distribution of carbs within the steel are the elements that determine this factor.
Sharp sealing is a factor related to wear resistance, but not only.
The cutting edge must be able to withstand even small shocks when cutting solid materials, here also comes into play hardness.
Resistance to deformations
The load capacity without permanent deformations.
For many uses resistance is a determining factor and is often correlated with hardness, the harder the steel, the stronger the resistance.
It must also be able to flex to return to the starting position and it must not break.
Consider how many ways a survival/bushcraft knife or a military knife can be used.
Resistance to oxidation
This property can be useful in corrosive environments, such as salt water and some silica materials (for example certain foods).
Micro-oxidations are not phenomena to be underestimated as they can, in a given period of time, lead to the loss of the wire.
The corrosion resistance of stainless steels is due to the formation of a passive surface layer, called a “passive film”.
In order for this very fine surface to form, the percentage of chromium in steel must be greater than 12.
This element generates on the surface of the metal, an oxide that has the property to stop corrosion.
However, it must be taken into account that all steels (even stainless steels), having a strong iron matrix, are subject to oxidation and only good maintenance preserves them completely intact.
Hardness
It is the ability to work without consequent damage.
Remember that the increase in hardness leads to an increase in the permanent deformation point (i.e. the point after which the deformation of the material changes from elastic to plastic and increases the point of tension breakage), but decreases the resistance to shocks and the flexibility.
On the other hand, the increase in toughness and elasticity results in the increased ability to absorb shocks, greater ductility and workability, but also a decrease in the point of deformation.
It is clear from these examples that if the steel being treated is intended for the production of swords or machetes, the last aspect will be privileged with less drastic hardenings and more pushed findings to avoid easy cracks in shocks.
On the other hand, if steel is used for the production of knife blades, where the impact is rare but is frequent cutting, it will be a drastic hardening and a detection just intended to stretch the material trying to keep the hardness at the highest level compatible.
As you can see it is essential to understand and know the destination of using the knife to make it reliable to its use and purpose.
A great yardstick for these aspects, is the Rockwell hardness test.
Sharpening and wire tightness (sharp)
Some steels seem to take a sharp much thinner than others, although sharp in the exact same way.
This is due to the presence of the “grain of steel”.
The thin-grained ones manage to have a thin cutting and a clean cut, where instead there is a “coarse grain” the operation turns out to be more difficult.
To overcome this problem, Vanadio is added.
There are steels that are more suitable for cutting than others.
Ps. Test! There are also a number of tests that need to be done every now and then on the blades to verify that they are in the required standards. A few blades must be sacrificed for testing.
Temper and re-found
The materials normally used by knife manufacturers producing blades are chromium-hardened, high-carbon steels “AISI (Arerican Iron and Steel Institute) 440 and AISI 420”, in other words the martensic stainless steels, which contain at least the 12 of chromium, the potential of which can be developed with an appropriate cycle of construction and heat treatment.
Martensitical steels are alloys of iron, carbon and chromium,to which very often, to improve and increase stainlessness, hardness, and toughness, other elements are added such as vanadium, molybdenum, nickel, tungsten.
The best distribution, union and fusion of these elements between them, allows to make a steel of excellent quality.
Hardening
To make the most of the potential of martensitic stainless steel, run the heat treatment or even called temper.
Steel tied to other elements develops particular properties according to the characteristics that are to be enhanced according to the use.
Typically what turns a steel tied into an optimal steel for the knife is the thermal treatment (temperature and re-found).
Each steel tied is characterized by a critical temperature at which the crystalline structure of the steel changes by increasing the carbon solubility in the ferritic matrix:
This temperature must be maintained in order to obtain the austenization of steel but not so much as to promote the growth of the size of the grain.
Ps. Especially for knife blades you prefer to keep low.
The next step is to cool the temperature sharply (tempera operation) by various means (water, oil, salt emulsions, ice, air, etc.) to get the desired hardness level.
Today cryogenic tempers are also going in fashion but I will talk about it in a specific post, after trying and testing this type of treatment.
Tempering
After the hardening, the steel is very hard but also very fragile.
To achieve a good compromise between hardness (which translates into longer wire duration) and decreased fragility (which results in increased shock resistance), a second heat treatment called operation is always performed of the founding.
The purpose of the detection is to relax the material subject to the state of internal comation, induced by temperand and remove the residualtensions.
Elements of steels
Carbon C
Present in all steels is the element that transforms the iron into steel characterizing the elasticity of the blade increasing the hardness and durability of the cutting edge.
Consider that on average steel must have a .5 carbon to be called a “high carbon content”.
Cr Chrome
An element that increases resistance to wear, fatigue and corrosion. A steel with at least 13-14 chromium is usually considered “stainless” steel, although the definition would not be entirely accurate because, despite the name, all steel can oxidize if no maintenance is carried out.
Cobalt Co
It increases stamina and hardness and allows you to withstand high temperatures multiplies the effects of other alloy elements.
Manganese Mn
Important element, as manganese helps the structure to elevate the capacity of hardness and improves steel, deoxidize and degasa metals during thermal treatments.
Present in most of the knife except in the A-2, L-6 and the CPM 420V.
Molybdeno Molybdeno Molydus
It prevents fragility (Krupp’s disease fragility to find) and increasing toughness and resistance to fatigue, increases workability and resistance to corrosion.
Ni
Increases hardness and endurance.
Present in L-6 and AUS-6 and AUS-8. Nickel can also play a role in corrosion resistance as well, but it is definitely not as valid as chromium and should be used with high percentages at the expense of wire tightness.
Phosphorus P
It decreases fragility if in high concentrations increases resistance, workability, and hardness.
Copper Cu
Increases corrosion resistance and fatigue resistance.
Silicon Si
It helps to increase the resistance.
Like manganese, it makes steel more flexible during construction due to the effect of deoxidation and degassing.
Zolphus S
Often avoided in the knife shop, it improves processing but decreases the hardness of the steels.
Tungsten W
Increases wear resistance and toughness.
Vanadio V
It helps to increase the resistance to wear and shock.
Another important feature is that it is able to refine the granular growth in the steel, this increases the hardness that allows to have an extremely clean and functional cut.
There are several steels that have this component, but the most significant are the CPMS60 and CPMS90.
Wolframio W
Increases wear resistance and toughness.
Non-stainless steelors or stainless seeds
They are usually forged steels and that lend themselves well also to differentiated tempre, a technique used for forging for katana blades, this to give a sharp with a greater hardness and greater elasticity of the coast.
In the SAE indication system, steels that have a letter indication (for example, W-2, A-2 ) are generally steels for professional tools. There is an ASM classification, but it doesn’t affect the knife.
Often, the latest numbers of the name of these steels, indicate the degree of carbon contained.
So 1095 is carbon-containing for .0.95, the 52100 contains carbon for .1.0, the 5160 has the percentage of .0.60.
D-2
The D-2 is sometimes referred to as “a semi-stainless.”
It has a high percentage of chromium (12), but not enough to classify it as stainless, but it is still better than the oxidation of non-stainless steels described above.
It has excellent wear resistance, it’s much harder than stainless steels like ATS-34,
The combination of wear resistance, almost stainlessability and hardness make this steel one of the most appreciated for using tools (cutters or other tools that have to work at high temperatures) but also by level knife builders, enough think of Cris Reeve or Benchmade who have been using it for some time.
M2, M2
Used mainly in the industry for the use of cutting tools that work at high speed resulting in overheating.
It can hold its temperament even at high temperatures.
It’s slightly tougher and slightly more resistant to D-2. However, this steel ossias very easily.
Benchmade has using this steel in some AFCK models.
A-2
Steel from tools harder than D-2 and m2, but with less wear resistance.
The excellent hardness makes him an excellent choice for combat blades, currently chris Reeve and Phil Hartsfield use A-2.
O-1
Very popular steel and used by forafores.
It is an excellent steel for the compromise between sealing and maintaining the cutting edge.
It’s easy to ossid if no maintenance is applied.
Randall and Mad Dog are among the most renowned knife builders using these blades.
10XX Series
1095 (and 1084, 1070, 1060, 1050, etc.) many of the steels of 10XX are used for knifery, but the 1095 is the most used among the aforementioned.
When you go in the order from 1095-1050, the higher the final numbering is, the higher the carbon percentage, then the more resistance and the harder. The 1060 and 1050, are often used for swords.
For the knife shop the 1095 is a great compromise between cost and quality, it is reasonably hard and holds a good thread and, what not to be underestimated, it is easy to sharpen, unfortunately it ossids easily if no maintenance is carried out.
It is a simple steel, containing only two binders: .95 carbon and .4 manganese.
The various Ka-bas use 1095 as steel with a coating to protect against oxidation.
Carbon V
Carbon V is a Cold Steel patent and is not specifically any particular steel, it describes rather which steel is used in its production.
It seems that such steel is an intermediate route between 1095 and O-1, and if no oxidized maintenance is carried out.
From reliable sources and from tests carried out by specific meters, they indicate carbon V in 50100-B, i.e. 0170-6 (they are the same steel see below)
0170-6 50100-B
These acronyms indicate the same thing, 0170-6 is the steel classification of the creators, while 50100-B is the indication of AISI.
A good chromium-vanadium steel similar to the O-1 but less expensive. Blackjack used O170-6.
L-6
Steel mainly used in the 90s, rather hard holds well the sharpening, but oxidizer very easy.
5160
Steel popular among foraforers who create blades of generous size.
It has good resistance to wear, but is known for its exceptional hardness due to the addition of chromium.
It is usually raised to a maximum of 50 HRC for swords, while in the knife shop we can reach 60 HRC.
52100
Used in the indirection in the construction of bearings is used only by forasters, but now it can also be found in bars.
It’s similar to 5160, it has carbon of around 1 versus 5160.60.
Used for hunting blades when looking for better resistance to wear at the expense of some degree of lower hardness.
CPM 10V
Steel is quite resistant to oxidation and has a high resistance to wear, but at the expense of hardness.
It can be a good alternative to D2.
CPM 3V
The incredibly hard 3V CPPm gives resistance to excellent wear and good resistance to oxidation.
Using when you want an extremely hard product with excellent resistance to wear, of course at the expense of resistance.
Steels
Given that, even if so defined, all steels can oxidize.
Surely the range defined as stainless, especially for the virtue of having chromium percentages of about 13, has a greater resistance to oxidation.
The following are the main steels used in the manufacture of blades in groups.
This is because many stainless steels have almost identical characteristics and their characteristics are improved or enhanced by the type of heat treatment and the type of object constructed.
Ranked in order of quality:
420 and 420J
The most basic of stainless steels.
They are extremely resistant to oxidation, but very tender.
They are generally used for exhibition objects, such as swords or collectible fantasy knives.
440A-425M-420HC-12C27-6A
Used in small knives, they can be hardened more than the previous group, to have greater resistance to wear naturally with the right heat treatment.
Gin-1 ATS-55 8A 440C
These steels will usually be stronger than the previous group and more resistant to use.
They maintain excellent properties of resistance to oxidation, however ATS-55 stick out here as not especially resistant stain.
8A is among those of this group that deserves a special mention, having a substantial percentage of vanadium can be very sharp but among the group is the weakest and the least resistant to use.
ATS-34/154CM VG-10 S60V
It is difficult to distinguish the substantial differences between ATS-34 and 154-CM, they are widely used and their characteristics vary from company to company depending on the treatments.
They lend themselves to multiple uses as they hold the cutting edge quite well and are quite hard, although they are not extremely resistant to oxidation.
VG-10 has in its interior of the vanadium that allows the formation of thin grains, quality that allows to have a thin and clean cut.
S60V is the one that best resists wear and is the one mentioned in the group when it takes resistance to abrasions for general work
BG-42 S90V S30V
The best. BG-42 has better wear resistance among the steels described.
It is harder and more resistant to oxidation than an ATS-34, but it is difficult to sharpen. S90V is the top in wear resistance and oxidity resistance.
It can also be difficult to sharpen.
Difficult to process there are few houses that produce blades with this steel, mainly we talk about knives built behind order.
The S30V recedes on the Wear Resistance of the S90V, but is significantly harder and easier to sharpen.
It is more resistant to the use of BG-42. S30V is currently used in some Spyderco, Chris Reeve and Benchmade.
420
The lower carbon meet<( .5) that brands of 440 series this steel extremely gently and it does not hold a well an edge.
It is often used for diving blades, as it is extremely resistant stain. Also often used for very cheap blades.
External use of salt water, is too soft to be a good choice for a practical blade.
420HC
Carbon is added to 420 to increase its cutting capacity.
440A – 440 B – 440C
The carbon content of this stainless steel is about : A (.75) B (.9) C (1.2). 440C is an excellent stainless steel, usually around 56-58 Rc, very hard and with good cutting grip.
The 440C was the king of stainless steel in the 1980s, before ATS-34 and VG10 rose to fame in the following decades.
All three resist oxidation well.
Sog used 440A for the Seal 2000, Randall apparently uses 440B for his stainless blades.
425M 12C27
Similar to 440A the 425M (0.5 carbon) has been used in the past by Buck.
The 12C27 (.6 carbon) is a Scandinavian steel that, when treated appropriately, is better for lightness and resistance to the family of 440.
Several companies use this steel for their folding, Viper, Laguiole En Aubrac, Mongin, are examples.
AUS-6 AUS-8 AUS-10 (aka 6A 8A 10A)
Japanese stainless steel saditable in amount of carbon to the family of 440A : 440A ( AUS-6, .65 carbon) ; 440B (AUS-8, 0.75 carbon) ; 440C (AUS-10, carbon 1.1).
All 3 steels have an added amount of vanadium (which the 440 do not have), to improve wear resistance and refine grains to improve cutting capacity.
GIN-1 (aka G-2)
Steel with a little less carbon and a little more chromium.
Used by Spyderco in production in the mid-1990s for cheaper lines. Ultimately it is a very good stainless steel, less expensive but with a tip less resistance to wear and resistance than ATS-34.
H1
High-percentage chromium steel that offers high performance in corrorsion resistance.
Used mainly for knives for use at sea.
ATS-34 154-CM
Japanese production in the 90s was the stainless at the top of production. The 154-CM is the American version today mainly used by US companies such as Microtech.
As a rule these steels are around 60 Rc and can hold a good sharp even if very hard.
ATS-55
Similar to the previous one but with the items removed and some others added. This steel is a good knife steel. With the molybdenum removed, ATS-55 doesn’t seem to hold the cutting edge like ATS-34.
VG-10
Other stainless steel with vanadium addition.
The VG10 easily takes the wire and is extremely resistant to oxidation.
One of the best in value for money.
It is used by Spyderco.
BG-42
BG-42 is similar to ATS-34, with two important differences: it has double manganese and has vanadium 1.2 ( ATS-34 has no vanadium ), this to increase the grip of the cutting edge.
S60V (CPM T440V) – S90V(CPM T420V)
Two of the best trade steels.
Both steels have a high percentage of vanadium which represents excellent wear resistance but at high costs.
CPM S30V
This steel gives the hardness of an A2 with the wear resistance of an S90V, holding a reasonable hardness (-59-60 Rc).
This blend makes this steel among the top on the market. Chris Reeve currently uses this steel for his folding.
NCo690
This steel is produced in Austria by a small steel mill specializing in high-quality steel.
N690 is a martensic stainless steel with 17chrome and aiSI 440 C steel is distinguished by a higher molybdenum (double) content.
The molybdenum in addition to being a strong trainer of carbs (improvement of cutting characteristics), increases the resistance to corrosion in high steels related to chromium.
In addition, the additions in vanadio alloy (also a carb trainer resulting in increased wear resistance and therefore maintenance of the cutting edge) and cobalt (hinders the enlargement of the grain at higher temperatures and significantly improves the high-temperature resistance) and the properties of this steel.
The characteristics of high corrosion resistance, wear, sharp wire tightness and good lucidity combine high hardness values greater than 60 HRC (More than the traditional AISI 440 C steel) that can be obtained by the thermal treatment of Hardening.
For these reasons its use is oriented to the production of professional blades and knives and thanks to the particular tightness of the cutting edge and resistance to oxidation is used in the industrial (food and fish) knife industry for the meat processing.
In addition, in the medical sector it is used for the production of surgical instruments. This steel is used throughout the Extrema Ratio range.
Damascus
The steels of Damascus are obtained by forging and “welding” one or more steels that are then beaten, wronged or cut depending on the reason you want.
It can then be acidic to make the textures of the design stand out.
Nowadays the damask is built more to provide a scenic effect than for performance use.
Titanium
The new titanium alloys provide high performance, are extremely resistant to oxidation, lightweight, abrasion-resistant and amagnetic.
Due to the high cost and difficulty in processing, few companies use this material, including the “Mission Knives” which uses a alloy called Beta Titanium.
ceramic
A small signal about the ceramic knives very used in the food field that have the characteristic of having very hard blades obtained using zirconium enriched with magnesium, silicon and calcium.
Mostly used for kitchen knife and offer unique features such as, an above-average cutter seal, maximum hygiene thanks to the inert building material that does not provoke reactions with the cut food and easy cleaning.
Never be used in sports or survival for the high fragility of the blade.
Translation of “steel” into other languages
- Albanian: Eliku
- Arabic: (-)
- Basque (euskara): altzairua
- Bulgarian:
- Catalan: acer
- Czech: ocel
- Chinese:
- Croatian: Chelik
- Danish: st’l
- Hebrew:
- Flemish: stoal
- Finnish: ters
- French: acier
- Japanese:
- Greek:
- Hindi:
- English: steel
- Latin: aciarium
- Norwegian (bokmal and nynorsk): st-l
- Dutch: staal
- Polish: stal
- Portuguese: acao
- Romanian: Oel
- Russian:
- Serbian: Chelik
- Spanish: Maple
- Swedish: st’l
- German: Stahl
- Turkish: Elik
- Hungarian: acél
Bibliography
- www.spyderco.com
- www.extremaratio.com
- www.ajh-knives.com/metals.html
- www.zknives.com/knives/articles/knifesteelfaq.shtml
- www.metal-mart.com/Dictionary/dictlist.htm
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