Post by Lobster on Feb 3, 2016 17:51:18 GMT 3
Blade steel
The variety of steels used in knife making is bewildering with so many different offerings available. While for most users the type of steel isn't a priority when making the decision to buy any particular knife, it is worth looking into the propreties of the different materials when buying a knife for a specific task because their characteristics vary greatly.
The process of making steel:
Steel is made by adding carbon to iron, which itself is soft and not usable for making a working blade. Additional elements will give the steel further desired characteristics. We must understand, that there is always a trade off when making steel. With the current technology we cannot have a blade that is hard, tough, and easy to sharpen, has supreme edge retention and doesn’t rust. But the high end steel producers are working on it and we will certainly edge closer and closer to the perfect blade steel in the years to come.
Here re some of the most commonly used elements needed to make knife steel:
Carbon (C): Present in all steels, it is most important for hardening and adding strength to the steel. Knife-grade steel usually has more than 0.5% carbon making it high carbon steel.
Chromium (Cr): this element is added for increased wear resistance, ability to harden and corrosion resistance. A steel with at least 13% chromium is termed stainless steel. Despite the name, stainless steel can corrode if not maintained properly.
Cobalt (Co): Increases strength and hardness, and permits quenching in higher temperatures. Intensifies the individual effects of other elements in more complex steels.
Copper (Co): increases corrosion resistance
Manganese (Mn): aids the grain structure and increases hardness, strength and wear resistance. Improves de-oxidation during the manufacturing process of the steel.
Molybdenum (Mo): prevents brittleness and maintains the steel's strength at high temperatures. Present in air-hardening steels.
Nickel (Ni): Used for strength, corrosion resistance, and toughness.
Nitrogen (N): Used in specialized knife steel instead of carbon for hardening. Offers unusual high corrosion resistance.
Phosphorus (P): Improves strength, machinability and hardness. In high concentrations it males steel brittle.
Silicon (Si): Like manganese, makes the steel more sound while it's being manufactured and adds hardness to the steel.
Sulfur (S): Improves machinability when added in minute quantities, but can decrease toughness.
Tungsten (W): Increases wear resistance. Tungsten will make the steel to be a high-speed steel when combined with chromium or molybdenum.
Vanadium (V): Increases resistance to wear and ability to harden. Helps to produce fine-grained steel.
Types of steel used for knife making
Knife blades are made from a variety of materials, the most common ones being carbon steel, stainless steel, tool steel and alloy steel. Less-common materials like cobalt and titanium alloys and ceramics cn be used too. Below is a list of some of most widely used in the knife making industry:
Non-stainless steels (high carbon and alloy steels):
Because of their high carbon content, Carbon steel tends to corrode much quicker than stainless steel. These are some of the most commonly used carbon steels used for knife making:
10.. series steel: Many of the 10-series steels (1095, 1084, 1070, 1060, 1050) are used, though 1095 is the most popular for knife making. When you go in order from 1095-1050, you go from higher to lower carbon content, from better to lesser edge retention and from tough to toughest. For knives, 1095 is sort of the "standard" carbon steel, not too expensive and performs well. It is reasonably tough and holds an edge very well. It rusts easily. This is a simple steel, which contains only two alloying elements, 0.95% carbon and 0.4% manganese.
Alloy steels:
5160: Extremely popular now and a very high-end steel. It is essentially a simple spring steel with added chromium. It has good edge retention and outstanding toughness.
52100: A ball-bearing steel similar to 5160 (though it has around 1% carbon vs. 5160 ~.60%), but holds an edge better. It is less tough than 5160 however. It is used often for hunting knives and other knives where the user is willing to trade off a little of 5160's toughness for better edge holding.
A-2: An excellent air-hardening tool steel, it is known for its great toughness and good edge holding.
D-2: is a tool steel sometimes called "semi-stainless". At 12%, it has a high chrome content but not high enough to classify it as stainless. It is nonetheless much more stain resistant than most high carbon steels and is used for many mid tech knives because of its excellent edge retention.
L-6: A band saw steel that is very tough and holds an edge well, but rusts easily. If the maintenance is not an issue and extreme toughness is required , this can be considered one of the best steels available.
M-2: A high-speed steel, it can hold its propreties even at very high temperatures, and as such is used in industry for high-heat cutting jobs. It is an excellent edge holder.
Stainless (low carbon) steels:
All steels can rust. But the following steels with their high amount of chromium (13%) and low content of carbon (below 0.5%) have much more rust resistance than the steels mentioned above. Also, other alloying elements have a strong influence on the amount of chromium needed; lower chromium with the right alloying elements can still have "stainless" performance.
420: The carbon content of less than 0.5% makes this steel much softer than the 440 series steel and it doesn't hold an edge well. It is often used for diving knives due to its corrosion resistance but it is too soft for general utility knives.
440 A - 440 B - 440-C: The carbon content and thus the hardness of these stainless steels increases from A to C and the corrosion resistance decreases. 440-C is widely used, and is generally considered one of the best general-use stainless steels. If your knife is marked with 440, it is likely the less expensive 440-A. The general feeling seems to be that 440-A is good enough for everyday use, 440-B is a very solid performer and 440-C is excellent.
3Cr13: Chinese made steel equivalent to 420B with an approximate HRC of 52 after heat treatment.
3CR13MoV: Chinese made by adding more elements molybdenum and vanadium to the 3Cr13 formula.
4Cr13: Chinese made 420-C stainless steel, it obtains about 55-57HRC.
4Cr13Mo: Chinese made, developed based on 4Cr13 with added Molybdenum.
5Cr15MoV: Chinese made, some manufacturers label it as 5Cr13MoV. It's widely used to make kitchen knives, high-end scissors, folding knives and hunting knives etc.
6CR13MoV: Chinese made, also labeled as 6Cr14MoV. Similar stainless steel grade of 420D which does not contain molybdenum and vanadium.
7CR17MoV: Chinese made 440A modified which contains more Vanadium.
8CR13MoV & 8CR14MoV: Chinese made, these grades do not have very big difference. They are similar to AUS-8, an excellent steel for its low price.
9Cr13MoVCo (9Cr13CoMoV): Chinese made, described as forged high carbon cobalt stainless steel.
14-4CrMo: American made, stainless tool steel that has better corrosion resistance than 440C stainless steel.
1.4116: This is the steel used in Swiss Army Knives. It is exceptionally corrosion resistant and very tough. It does not hold an edge well, but it is very easy to sharpen.
154CM: Widely used in high quality knives. It is a good balance between all three attributes, being relatively hard, tough and corrosion resistant. It is very similar chemically to RWL 34 and ATS-34.
ATS-34: A Japanese product that is very similar to 154-CM, and is the premier high quality stainless. Normally hardened to around 60 Rc, it holds an edge very well and is tough enough even at that high hardness. Not quite as rust resistant as the 400 series above.
ATS-55: Similar to ATS-34, but with the molybdenum removed and other elements added. It combines ATS-34 edge retention with increased toughness. Since molybdenum is an expensive element and knife blades do not need to have the high speed properties, removing it reduces the price of the steel while at least retaining a high performance.
AUS-6 - AUS-8 - AUS-10 are Japanese stainless steels, roughly comparable to the 440 series mentioned above. 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. Unlike the 440 series, AUS steels have vanadium added which will improve wear resistance.
BG-42: Somewhat similar to ATS-34, with two major differences: It has twice as much manganese and has 1.2% vanadium (ATS-34 has no vanadium), so it has better edge-holding than ATS-34
G2: A steel with slightly less carbon, slightly more chromium, and much less molybdenum than ATS-34. A very good stainless steel.
H1: uses nitrogen instead of carbon for hardening making the steel extremely corrosion resistant. Does not retain edge too well.
Sandvik 12C27: A Swedish steel with a hardness range of 54-61 HRC and 0.6% carbon. Is is similar to 440A, has high toughness and good corrosion resistance. It takes a very sharp edge and is used for hunting knives, pocket knives, camping knives, high-end chef's knives and tactical knives.
Sandvik 13C26: Generally the same properties as Sandvik 12C27, but with slightly higher hardness but less corrosion resistance.
Sandvik 14C28N: Generally the same properties as Sandvik 12C27, but with higher hardness and slightly better corrosion resistance.
VG10: A Japanese made high-end steel high in carbon and chromium, giving it excellent corrosion resistance and high hardness. Tough, but lacking hardness compared to even cheaper steels like AUS-8.
N690 Cobalt Stainless Steel is made in Austria by Böhler. With a 1.07% carbon content, this steel is similar to 440C which has a carbon content ranging from .95 – 1.07 percent. The N690 is a high end stainless steel used by many makers, Extrema Ratio uses nothing else for their knives. It is a durable knife steel that is wear resistant and hardens well.
Powder steel:
Powder steel is the current cutting edge in knife steel technology. It is formed by mixing very finely ground powders of the various metals and elements compressing them into a mold and then heating them just below melting temperature to make them bond. It allows for a precise mixture and perfectly even distribution of all the different elements. This is specialist chemistry done under strict laboratory conditions. For knife making they are exceptional steels.
CPM 1V: Produced by Crucible using Crucible Particle Metallurgy process it has very high toughness, several times higher than A2 with same level of wear resistance
CPM 3V: very high toughness, more than A2, and high wear resistance, better than CPM 1V. Used by several custom knives makers and factories. Makes good choice for large knives.
CPM M4 is a high speed tool steel. It is a high-vanadium steel exhibiting very good wear resistance and toughness. Although M4 has been around for a long time, it has only lately entered the world of high end production and custom Knives.
CPM 10V: highly wear-resistant tool steel, toughness comparable with D2 tool steel.
CPM154: has the same chemical composition like 154CM but with superior characteristics due to the better distribution of the elements.
CPM S90V contains high amounts of vanadium and carbon. Hard to work, expensive and challenging to sharpen but exceprional wear resistance and edge retention.
CPM S110V: Hard to work and sharpen but extreme high wear resistance and edge retention. Very similar to CPM-S90V.
Elmax: A European powder metal steel used in higher end knives, Elmax is a very good all around steel, a generation ahead of formulations like 154CM with superior edge retention and ease of sharpening.
M390: uses third generation powder metal technology and was developed for knife blades requiring excellent corrosion resistance and very high hardness for excellent wear resistance. Chromium, molybdenum, vanadium, and tungsten are added to promote sharpness and outstanding edge retention.
S30V: Introduced in 2001, S30V is made with 1.45% carbon, 4% vanadium, and 10.5% chromium carbide. This steel continues to be one of the best knife steels on the market for a wide range of knife uses and applications. Vanadium carbides are some of the most prized carbides for knives. Their carbides provide extreme hardness in the steel alloy matrix.
S35VN modified the formula of S30V by adding niobium (hence S35VN) to the vanadium and chromium carbide forming elements. The specific formula for S35VN is 3% vanadium, 1.4% carbon, 0.5% niobium, 2% molybdenum, and 10.5% chromium. This composition makes it tougher without reducing the edge retention. S35VN is tougher and easier to machine, grind and polish than S30V .
S60V: This stainless steel has high wear resistance. High content of vanadium and a carbon content of 2.15%. It is just a step above S30V. This steel is not commonly used for knives.
S90V: Has a carbon content of around 2.30%. This steel has an even superior edge retention still but it is extremely difficult to sharpen. Right now, few custom makers are the only ones using this type of steel.
Vanax: Vanax is currently one of the most high tech steels available for knives. It is a third generation powder metallurgy nitrogen stainless steel. The steel has very little carbon. Nitrogen is used in place of the carbon to make the steel hard. The result is a steel with extreme corrosion resistance, excellent edge holding and is easily resharpened. According to the steel manufacturer Uddenholm, the latest generation of Vanax is tougher than Elmax which is the toughest PM cutlery grade stainless steel.
ZDP-189: A Japanese-powder steel, ZDP-189 is essentially the mirror opposite of 3V—it is extremely hard (64-66 HRc) instead of extremely tough. ZDP-189 can be ground thinner and needs sharpening less often. ZDP-189 can tarnish, though not as easily as CPM3V.
Cru-Wear is a Crucible tool steel which a great balance between toughness and wear resistance and it can be set between CPM-V3 and CPM-M4
Maxamet is quite a new powder steel used in the knife industry since around 2014. It features extreme hardness and very high edge retention and toughness but it is not corrosion resistant. It is comparable to CPM-S110V steel except that it is not a stainless steel. Challenging to sharpen.
MagnaCut is a new steel type designed by Larrin Thomas in 2021 specifically for knives. Produced by Crucible, it’s a powder metallurgy steel exhibiting very interesting and quite unique properties. It provides an excellent mix of toughness and wear resistance with high levels of corrosion resistance. Together with the very fine structure, MagnaCut can be put it in the same league as CPM-CruWear and CPM-4V for toughness and edge retention but above CPM-S45VN and CPM-S110V with regards to corrosion resistance. Very expensive but over time the cost might come down as more manufacturers make use of this new steel.
Damascus steel:
The origin of this steel dates back over 2500 years to India. By today's standards, Damascus steel is not considered a particularly high quality steel but until the 17th century it was the most sophisticated and magnificent steel for knives and swords. It was highly priced for its sharpness, flexibility and toughness. Originally, Damascus blades were forged from so called wootz steel ingots that were made in India and Sri Lanka and exported to the Middle East and the city of Damascus where a thriving weapons industry was eagerly using these ingots to produce blades of outstanding quality. The details how the ancient metal smiths were producing these Ingots were lost by the middle of the 17th century and despite a lot of efforts, nobody so far has been able to faithfully reproduce wootz steel.
Today, a process known as pattern welding is used to produce a steel of very similar characteristics and appearance and although technically incorrect, the name Damascus steel is applied to pattern welded steel. These days, Damascus steel is used mainly for its visual appeal and appreciation of the craftsmanship that goes into forging a blade from folded steel.
distinctive Damascus pattern on modern knife
Properties of Knife Steel
Characteristics often used to describe the quality of knife steel are hardness , wear resistance, toughness, edge retention and corrosion resistance.
Hardness is a measure of a steel’s resistance to deformation. Hardness in knife steels is commonly given in hardness Rockwell. Hardened knife steels are generally between 54 and 62 HRC (hardness Rockwell C), depending on the grade. The Rockwell hardness is measured by the indentation a diamond tip leaves in the steel under a given pressure.
Wear resistance is the ability of material to resist being abraded or eroded by contact with work material. Wear resistance is provided by both the hardness level and the chemistry of the knife blade. There is no standardized test method for wear resistance.
Toughness is the relative resistance of a material to breakage, chipping, or cracking under impact or stress. Toughness may be thought of as the opposite of brittleness. Toughness testing is not as standardized as hardness testing. It may be difficult to correlate the results of different test methods. Common toughness tests include impact tests and bend fracture tests.
Edge Retention dictates how well an edge will retain its sharpness. The problem with edge retention is that it cannot be quantified, it is a very subjective characteristic and there is no standardized way of measuring this characteristic.
Corrosion Resistance is a measure of a steel’s resistance to corrosion in high humidity, damp, or salt environments. This resistance is established by the addition of chromium to the composition. Developing corrosion resistance in a heat treatable, wear resistant steel is a challenge that has been met with numerous special alloys.
Heat Treatment
It is natural to assume that 2 knives made from the same steel will have the same characteristics but that is not so, the heat treatment process is crucial to determine the final characteristics of the stell in use. The heat treating process alters the alloy distribution and transforms the so called matrix to be capable of withstanding the pressure, abrasion and impacts inherent in knife use. Heat treatment has a huge impact on a knifes performance, a knife made from inferior steel but with a first class heat treatment will outperform a knife that is made from a super steel with a poorly executed heat treatment.
Preheating of knife steels during heat treatment is necessary to avoid thermal shock and distortion. Preheating is done to just below a critical transformation temperature. The part is then held long enough to allow the full cross‐section to reach a uniform temperature. Once the entire part is equalized, further heating to the austenitizing temperature will allow the material to transform more uniformly.
Austenitizing at an elevated temperature is necessary to harden knife steels. The actual temperature used depends on the chemical composition of the steel. The temperature is varied to tailor the resulting properties to specific applications. Higher temperatures permit slightly higher hardness, lower temperatures permit higher toughness.
Quenching the steel from the austenitizing temperature causes the steel to fully harden, which will provide the material’s strength. How fast a steel must be cooled to fully harden depends on the chemical composition. No matter how knife steels are quenched, the resulting structure, known as martenside, is extremely brittle and under great stress. For this reason, as soon as knife steels have been quenched by whatever method to hand‐warm temperature, they must be immediately tempered.
Tempering is performed to stress‐relieve the brittleness of martenside which was formed during the quench. A higher tempering temperature will yield a somewhat softer material with higher toughness, whereas a lower tempering temperature will produce a harder and somewhat more brittle material.
The variety of steels used in knife making is bewildering with so many different offerings available. While for most users the type of steel isn't a priority when making the decision to buy any particular knife, it is worth looking into the propreties of the different materials when buying a knife for a specific task because their characteristics vary greatly.
The process of making steel:
Steel is made by adding carbon to iron, which itself is soft and not usable for making a working blade. Additional elements will give the steel further desired characteristics. We must understand, that there is always a trade off when making steel. With the current technology we cannot have a blade that is hard, tough, and easy to sharpen, has supreme edge retention and doesn’t rust. But the high end steel producers are working on it and we will certainly edge closer and closer to the perfect blade steel in the years to come.
Here re some of the most commonly used elements needed to make knife steel:
Carbon (C): Present in all steels, it is most important for hardening and adding strength to the steel. Knife-grade steel usually has more than 0.5% carbon making it high carbon steel.
Chromium (Cr): this element is added for increased wear resistance, ability to harden and corrosion resistance. A steel with at least 13% chromium is termed stainless steel. Despite the name, stainless steel can corrode if not maintained properly.
Cobalt (Co): Increases strength and hardness, and permits quenching in higher temperatures. Intensifies the individual effects of other elements in more complex steels.
Copper (Co): increases corrosion resistance
Manganese (Mn): aids the grain structure and increases hardness, strength and wear resistance. Improves de-oxidation during the manufacturing process of the steel.
Molybdenum (Mo): prevents brittleness and maintains the steel's strength at high temperatures. Present in air-hardening steels.
Nickel (Ni): Used for strength, corrosion resistance, and toughness.
Nitrogen (N): Used in specialized knife steel instead of carbon for hardening. Offers unusual high corrosion resistance.
Phosphorus (P): Improves strength, machinability and hardness. In high concentrations it males steel brittle.
Silicon (Si): Like manganese, makes the steel more sound while it's being manufactured and adds hardness to the steel.
Sulfur (S): Improves machinability when added in minute quantities, but can decrease toughness.
Tungsten (W): Increases wear resistance. Tungsten will make the steel to be a high-speed steel when combined with chromium or molybdenum.
Vanadium (V): Increases resistance to wear and ability to harden. Helps to produce fine-grained steel.
Types of steel used for knife making
Knife blades are made from a variety of materials, the most common ones being carbon steel, stainless steel, tool steel and alloy steel. Less-common materials like cobalt and titanium alloys and ceramics cn be used too. Below is a list of some of most widely used in the knife making industry:
Non-stainless steels (high carbon and alloy steels):
Because of their high carbon content, Carbon steel tends to corrode much quicker than stainless steel. These are some of the most commonly used carbon steels used for knife making:
10.. series steel: Many of the 10-series steels (1095, 1084, 1070, 1060, 1050) are used, though 1095 is the most popular for knife making. When you go in order from 1095-1050, you go from higher to lower carbon content, from better to lesser edge retention and from tough to toughest. For knives, 1095 is sort of the "standard" carbon steel, not too expensive and performs well. It is reasonably tough and holds an edge very well. It rusts easily. This is a simple steel, which contains only two alloying elements, 0.95% carbon and 0.4% manganese.
Alloy steels:
5160: Extremely popular now and a very high-end steel. It is essentially a simple spring steel with added chromium. It has good edge retention and outstanding toughness.
52100: A ball-bearing steel similar to 5160 (though it has around 1% carbon vs. 5160 ~.60%), but holds an edge better. It is less tough than 5160 however. It is used often for hunting knives and other knives where the user is willing to trade off a little of 5160's toughness for better edge holding.
A-2: An excellent air-hardening tool steel, it is known for its great toughness and good edge holding.
D-2: is a tool steel sometimes called "semi-stainless". At 12%, it has a high chrome content but not high enough to classify it as stainless. It is nonetheless much more stain resistant than most high carbon steels and is used for many mid tech knives because of its excellent edge retention.
L-6: A band saw steel that is very tough and holds an edge well, but rusts easily. If the maintenance is not an issue and extreme toughness is required , this can be considered one of the best steels available.
M-2: A high-speed steel, it can hold its propreties even at very high temperatures, and as such is used in industry for high-heat cutting jobs. It is an excellent edge holder.
Stainless (low carbon) steels:
All steels can rust. But the following steels with their high amount of chromium (13%) and low content of carbon (below 0.5%) have much more rust resistance than the steels mentioned above. Also, other alloying elements have a strong influence on the amount of chromium needed; lower chromium with the right alloying elements can still have "stainless" performance.
420: The carbon content of less than 0.5% makes this steel much softer than the 440 series steel and it doesn't hold an edge well. It is often used for diving knives due to its corrosion resistance but it is too soft for general utility knives.
440 A - 440 B - 440-C: The carbon content and thus the hardness of these stainless steels increases from A to C and the corrosion resistance decreases. 440-C is widely used, and is generally considered one of the best general-use stainless steels. If your knife is marked with 440, it is likely the less expensive 440-A. The general feeling seems to be that 440-A is good enough for everyday use, 440-B is a very solid performer and 440-C is excellent.
3Cr13: Chinese made steel equivalent to 420B with an approximate HRC of 52 after heat treatment.
3CR13MoV: Chinese made by adding more elements molybdenum and vanadium to the 3Cr13 formula.
4Cr13: Chinese made 420-C stainless steel, it obtains about 55-57HRC.
4Cr13Mo: Chinese made, developed based on 4Cr13 with added Molybdenum.
5Cr15MoV: Chinese made, some manufacturers label it as 5Cr13MoV. It's widely used to make kitchen knives, high-end scissors, folding knives and hunting knives etc.
6CR13MoV: Chinese made, also labeled as 6Cr14MoV. Similar stainless steel grade of 420D which does not contain molybdenum and vanadium.
7CR17MoV: Chinese made 440A modified which contains more Vanadium.
8CR13MoV & 8CR14MoV: Chinese made, these grades do not have very big difference. They are similar to AUS-8, an excellent steel for its low price.
9Cr13MoVCo (9Cr13CoMoV): Chinese made, described as forged high carbon cobalt stainless steel.
14-4CrMo: American made, stainless tool steel that has better corrosion resistance than 440C stainless steel.
1.4116: This is the steel used in Swiss Army Knives. It is exceptionally corrosion resistant and very tough. It does not hold an edge well, but it is very easy to sharpen.
154CM: Widely used in high quality knives. It is a good balance between all three attributes, being relatively hard, tough and corrosion resistant. It is very similar chemically to RWL 34 and ATS-34.
ATS-34: A Japanese product that is very similar to 154-CM, and is the premier high quality stainless. Normally hardened to around 60 Rc, it holds an edge very well and is tough enough even at that high hardness. Not quite as rust resistant as the 400 series above.
ATS-55: Similar to ATS-34, but with the molybdenum removed and other elements added. It combines ATS-34 edge retention with increased toughness. Since molybdenum is an expensive element and knife blades do not need to have the high speed properties, removing it reduces the price of the steel while at least retaining a high performance.
AUS-6 - AUS-8 - AUS-10 are Japanese stainless steels, roughly comparable to the 440 series mentioned above. 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. Unlike the 440 series, AUS steels have vanadium added which will improve wear resistance.
BG-42: Somewhat similar to ATS-34, with two major differences: It has twice as much manganese and has 1.2% vanadium (ATS-34 has no vanadium), so it has better edge-holding than ATS-34
G2: A steel with slightly less carbon, slightly more chromium, and much less molybdenum than ATS-34. A very good stainless steel.
H1: uses nitrogen instead of carbon for hardening making the steel extremely corrosion resistant. Does not retain edge too well.
Sandvik 12C27: A Swedish steel with a hardness range of 54-61 HRC and 0.6% carbon. Is is similar to 440A, has high toughness and good corrosion resistance. It takes a very sharp edge and is used for hunting knives, pocket knives, camping knives, high-end chef's knives and tactical knives.
Sandvik 13C26: Generally the same properties as Sandvik 12C27, but with slightly higher hardness but less corrosion resistance.
Sandvik 14C28N: Generally the same properties as Sandvik 12C27, but with higher hardness and slightly better corrosion resistance.
VG10: A Japanese made high-end steel high in carbon and chromium, giving it excellent corrosion resistance and high hardness. Tough, but lacking hardness compared to even cheaper steels like AUS-8.
N690 Cobalt Stainless Steel is made in Austria by Böhler. With a 1.07% carbon content, this steel is similar to 440C which has a carbon content ranging from .95 – 1.07 percent. The N690 is a high end stainless steel used by many makers, Extrema Ratio uses nothing else for their knives. It is a durable knife steel that is wear resistant and hardens well.
Powder steel:
Powder steel is the current cutting edge in knife steel technology. It is formed by mixing very finely ground powders of the various metals and elements compressing them into a mold and then heating them just below melting temperature to make them bond. It allows for a precise mixture and perfectly even distribution of all the different elements. This is specialist chemistry done under strict laboratory conditions. For knife making they are exceptional steels.
CPM 1V: Produced by Crucible using Crucible Particle Metallurgy process it has very high toughness, several times higher than A2 with same level of wear resistance
CPM 3V: very high toughness, more than A2, and high wear resistance, better than CPM 1V. Used by several custom knives makers and factories. Makes good choice for large knives.
CPM M4 is a high speed tool steel. It is a high-vanadium steel exhibiting very good wear resistance and toughness. Although M4 has been around for a long time, it has only lately entered the world of high end production and custom Knives.
CPM 10V: highly wear-resistant tool steel, toughness comparable with D2 tool steel.
CPM154: has the same chemical composition like 154CM but with superior characteristics due to the better distribution of the elements.
CPM S90V contains high amounts of vanadium and carbon. Hard to work, expensive and challenging to sharpen but exceprional wear resistance and edge retention.
CPM S110V: Hard to work and sharpen but extreme high wear resistance and edge retention. Very similar to CPM-S90V.
Elmax: A European powder metal steel used in higher end knives, Elmax is a very good all around steel, a generation ahead of formulations like 154CM with superior edge retention and ease of sharpening.
M390: uses third generation powder metal technology and was developed for knife blades requiring excellent corrosion resistance and very high hardness for excellent wear resistance. Chromium, molybdenum, vanadium, and tungsten are added to promote sharpness and outstanding edge retention.
S30V: Introduced in 2001, S30V is made with 1.45% carbon, 4% vanadium, and 10.5% chromium carbide. This steel continues to be one of the best knife steels on the market for a wide range of knife uses and applications. Vanadium carbides are some of the most prized carbides for knives. Their carbides provide extreme hardness in the steel alloy matrix.
S35VN modified the formula of S30V by adding niobium (hence S35VN) to the vanadium and chromium carbide forming elements. The specific formula for S35VN is 3% vanadium, 1.4% carbon, 0.5% niobium, 2% molybdenum, and 10.5% chromium. This composition makes it tougher without reducing the edge retention. S35VN is tougher and easier to machine, grind and polish than S30V .
S60V: This stainless steel has high wear resistance. High content of vanadium and a carbon content of 2.15%. It is just a step above S30V. This steel is not commonly used for knives.
S90V: Has a carbon content of around 2.30%. This steel has an even superior edge retention still but it is extremely difficult to sharpen. Right now, few custom makers are the only ones using this type of steel.
Vanax: Vanax is currently one of the most high tech steels available for knives. It is a third generation powder metallurgy nitrogen stainless steel. The steel has very little carbon. Nitrogen is used in place of the carbon to make the steel hard. The result is a steel with extreme corrosion resistance, excellent edge holding and is easily resharpened. According to the steel manufacturer Uddenholm, the latest generation of Vanax is tougher than Elmax which is the toughest PM cutlery grade stainless steel.
ZDP-189: A Japanese-powder steel, ZDP-189 is essentially the mirror opposite of 3V—it is extremely hard (64-66 HRc) instead of extremely tough. ZDP-189 can be ground thinner and needs sharpening less often. ZDP-189 can tarnish, though not as easily as CPM3V.
Cru-Wear is a Crucible tool steel which a great balance between toughness and wear resistance and it can be set between CPM-V3 and CPM-M4
Maxamet is quite a new powder steel used in the knife industry since around 2014. It features extreme hardness and very high edge retention and toughness but it is not corrosion resistant. It is comparable to CPM-S110V steel except that it is not a stainless steel. Challenging to sharpen.
MagnaCut is a new steel type designed by Larrin Thomas in 2021 specifically for knives. Produced by Crucible, it’s a powder metallurgy steel exhibiting very interesting and quite unique properties. It provides an excellent mix of toughness and wear resistance with high levels of corrosion resistance. Together with the very fine structure, MagnaCut can be put it in the same league as CPM-CruWear and CPM-4V for toughness and edge retention but above CPM-S45VN and CPM-S110V with regards to corrosion resistance. Very expensive but over time the cost might come down as more manufacturers make use of this new steel.
Damascus steel:
The origin of this steel dates back over 2500 years to India. By today's standards, Damascus steel is not considered a particularly high quality steel but until the 17th century it was the most sophisticated and magnificent steel for knives and swords. It was highly priced for its sharpness, flexibility and toughness. Originally, Damascus blades were forged from so called wootz steel ingots that were made in India and Sri Lanka and exported to the Middle East and the city of Damascus where a thriving weapons industry was eagerly using these ingots to produce blades of outstanding quality. The details how the ancient metal smiths were producing these Ingots were lost by the middle of the 17th century and despite a lot of efforts, nobody so far has been able to faithfully reproduce wootz steel.
Today, a process known as pattern welding is used to produce a steel of very similar characteristics and appearance and although technically incorrect, the name Damascus steel is applied to pattern welded steel. These days, Damascus steel is used mainly for its visual appeal and appreciation of the craftsmanship that goes into forging a blade from folded steel.
distinctive Damascus pattern on modern knife
Properties of Knife Steel
Characteristics often used to describe the quality of knife steel are hardness , wear resistance, toughness, edge retention and corrosion resistance.
Hardness is a measure of a steel’s resistance to deformation. Hardness in knife steels is commonly given in hardness Rockwell. Hardened knife steels are generally between 54 and 62 HRC (hardness Rockwell C), depending on the grade. The Rockwell hardness is measured by the indentation a diamond tip leaves in the steel under a given pressure.
Wear resistance is the ability of material to resist being abraded or eroded by contact with work material. Wear resistance is provided by both the hardness level and the chemistry of the knife blade. There is no standardized test method for wear resistance.
Toughness is the relative resistance of a material to breakage, chipping, or cracking under impact or stress. Toughness may be thought of as the opposite of brittleness. Toughness testing is not as standardized as hardness testing. It may be difficult to correlate the results of different test methods. Common toughness tests include impact tests and bend fracture tests.
Edge Retention dictates how well an edge will retain its sharpness. The problem with edge retention is that it cannot be quantified, it is a very subjective characteristic and there is no standardized way of measuring this characteristic.
Corrosion Resistance is a measure of a steel’s resistance to corrosion in high humidity, damp, or salt environments. This resistance is established by the addition of chromium to the composition. Developing corrosion resistance in a heat treatable, wear resistant steel is a challenge that has been met with numerous special alloys.
Heat Treatment
It is natural to assume that 2 knives made from the same steel will have the same characteristics but that is not so, the heat treatment process is crucial to determine the final characteristics of the stell in use. The heat treating process alters the alloy distribution and transforms the so called matrix to be capable of withstanding the pressure, abrasion and impacts inherent in knife use. Heat treatment has a huge impact on a knifes performance, a knife made from inferior steel but with a first class heat treatment will outperform a knife that is made from a super steel with a poorly executed heat treatment.
Preheating of knife steels during heat treatment is necessary to avoid thermal shock and distortion. Preheating is done to just below a critical transformation temperature. The part is then held long enough to allow the full cross‐section to reach a uniform temperature. Once the entire part is equalized, further heating to the austenitizing temperature will allow the material to transform more uniformly.
Austenitizing at an elevated temperature is necessary to harden knife steels. The actual temperature used depends on the chemical composition of the steel. The temperature is varied to tailor the resulting properties to specific applications. Higher temperatures permit slightly higher hardness, lower temperatures permit higher toughness.
Quenching the steel from the austenitizing temperature causes the steel to fully harden, which will provide the material’s strength. How fast a steel must be cooled to fully harden depends on the chemical composition. No matter how knife steels are quenched, the resulting structure, known as martenside, is extremely brittle and under great stress. For this reason, as soon as knife steels have been quenched by whatever method to hand‐warm temperature, they must be immediately tempered.
Tempering is performed to stress‐relieve the brittleness of martenside which was formed during the quench. A higher tempering temperature will yield a somewhat softer material with higher toughness, whereas a lower tempering temperature will produce a harder and somewhat more brittle material.