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It seems that every time I look a knife manufactures catalog or web site these days, I see a new blade steel that I have never heard of before. In fact, I still remember the days when 440C was the first choice among custom bladesmiths, 154CM was just starting to make inroads, and Bob Dozier had yet to popularize the use of D2.However, today we have small foundries such as Crucible Industries, Bohler, Sandvik, Latrobe, and Progressive Alloys that have the capability to make short runs of specialty steels such as CPM S30V, VG-10, BG-42, Bohler M390, and Cronidur 30. Consequently, bladesmiths are now able to develop formulas for specialty blade steels that greatly enhance the desired properties in order to create knives that perform far better than our forefathers could have imagined in their wildest dreams. Therefore, this new breed of modern blade steels has been dubbed “super steels” by the knife community. But, are they truly “super”?
Well, when designing a blade steel, it can be designed in such a way that the elements added to the steel to create the alloy enhance one or more of the desirable properties of the steel such as edge retention, hardness, toughness, tensile strength, impact resistance, wear resistance, and corrosion resistance. Thus, there are seven key elements that are added to today’s super steels:
- Carbon is the mineral that transforms iron into steel and thus, iron is transformed into steel results when 0.2 % or more Carbon is present. But, only a bare 0.8+% can be absorbed by the iron; the balance in extremely high carbon steel increases hardness and it also increases the edge retention and wear resistance of the steel.
- Chromium added in quantities greater than 10.0%, produces stainless steels and serves to increase the hardness, toughness, tensile strength, and abrasion resistance of the steel.
- Molybdenum is added to help improve the hardness, abrasion resistance, and corrosion resistance of blade steels and, during melting, Carbon and Molybdenum combine to form hard, double-carbide, bonds.
- Next, Vanadium is added to increase hardness, tensile strength, and impact strength and to help produce a fine grain during heat treat and, it also it improves the wear resistance and refines the gain for both good toughness and the ability to sharpen to a very keen edge. In fact, many people report that they are able to get knives using steels that contain Vanadium shaper than they can steels such as ATS-34 that do not contain this element.
- Furthermore, Cobalt is added to increases strength and hardness and it permits quenching at higher temperatures which helps to create finer grain structure. Plus, it intensifies the individual effects of other elements in more complex steel alloys.
- Last, Tungsten is added to help to produce a fine, dense, grain structure
- and Manganese is added to increase harden-ability, tensile strength, and abrasion resistance in steel and to help to produce a fine, dense, grain structure by reducing the size of the carbides. However, chemical composition alone does not create a modern super steel. Instead, super steels also employ an expensive form of metallurgical technology called “powder metallurgy” in which the base steel as well as the alloying elements are first ground into fine powder and then they are sprayed into a heated crucible one layer at a time to produce the most even distribution of ingredients possible which, in turn, results in an extremely fine grain structure in the finished metal. So, let’s examine some of today’s super steels more closely:
- Bohler M390 is a high end, third generation, Austrian-made, powder metallurgy, stainless steel containing 1.90% Carbon, 20% Chromium, 1.0% Molybdenum, 4% Vanadium, and, 0.60% Tungsten. Designed to be a super version of CPM S30V and developed specifically for knife blades requiring good corrosion resistance and a very high degree of hardness for excellent wear resistance, it produces a very small granule size for more even distribution of the various elements. Also, it hardens and tempers to 60-62 HRC and it can be polished to an extremely fine finish.
- Udderholm Elmax is a third generation, powder metal technology, high carbon, stainless steel alloy containing 1.70% Carbon, 18% Chromium, 1.0% Molybdenum, 3% Vanadium, and 0.30% Manganese. Noted for its fine carbide distribution with extremely low inclusion content for virtually no edge chipping, it displays an excellent balance between corrosion resistance and edge retention and it can be polished to an extremely fine finish. Hardens and tempers to 57-59 HRC and 60-62 HRC with deep freeze. But, for maximum toughness, it is best hardened and tempered to 57-59 HRC and, for maximum wear resistance, it is best harden and tempered to 60-62 HRC.
CPM S30V is a powder-metallurgy stainless steel developed by custom bladesmith Chris Reeves in conjunction with Crucible Materials Corporation that contains 1.45% Carbon, 14% Chromium, 4% Molybdenum, and 2% Vanadium and is specifically designed to display excellent wear and corrosion resistance properties. Considered to be one of the best blade steels ever developed, its chemistry promotes the formation and even distribution of Vanadium Carbides, which are harder and more effective at cutting than Chromium Carbides. In addition, Vanadium carbides give the steel a very refined grain structure, which further contributes to the sharpness and toughness of blade’s edge.
- BG-42 is a double vacuum melted, stainless, blade steel made by Latrobe Specialty Steels Co. that contains 1.15% Carbon, 14.5% Chromium, 1.20% Molybdenum, 4% Vanadium, and 0.50% Manganese. Developed for use in critical aerospace components and high performance bearings, the steel is Vacuum Induction Melted (VIM) and then Vacuum Arc (VAR) re-melted to provide the extremely high purity level required for these fatigue-critical applications. However, when manufactured in sheet form, BG42 has proven to be an excellent knife blade steel. Also, it should be noted that during melting, the Chromium combines with the Molybdenum in the steel to form hard, double-carbide, bonds and the Vanadium content (which also serves to refine the grain structure) provides approximately 19% carbide volume in the steel. Thus, the high carbide volume, along with the presence of very hard Vanadium carbides and a fine grain structure enhances the wear resistance of the steel. In fact, blades made from this steel display excellent edge retention and good corrosion resistance.
- VG-10 is a stainless blade steel developed by Takefu Special Steel co., Ltd, based inTakefu, Fuki Prefecture, Japan (the former cutlery/sword-making center) with a composition of 1.0% Carbon, 15.0 % Chromium, 1.0% Molybdenum, 0.2 % Vanadium, and 1.5% Cobalt. Also, VG-10 stands for V Gold 10 (“gold” meaning quality) or sometimes V-Kin-10 (kin means “gold” in Japanese) because this steel is of such high quality that it is compared to a gold standard. As a result, VG-10 steel is highly abrasion resistant, has an improved, long-term, clean-cutting, edge, and is highly machinable and easy to grind. Therefore, it was originally intended for use in high-end Japanese chef knives but, this steel has also found a home in sporting cutlery.
- Cronidur 30 is the latest of the premium stainless steels coming out of the space shuttle program and Boker is the first to have it available to the sporting knives industry. Containing 0.25% – 0.35% Carbon, 14% – 16% Chromium, 0.85% – 1.1% Molybdenum, 0% – 0.5% Nickel, and 0.3% – 0.5% Nitrogen, Cronidur 30 is made by Progressive Alloy Steels Unlimited and was developed for use in the aircraft and aerospace applications where component durability, reliability, and long life are a must. Therefore, Cronidur 30 is superior in corrosion resistance to 440C and the large carbides evident in other high grade steels do not exist in Cronidur 30. Instead, there is a homogenous structure of finely dispersed Carbon Nitrides.
However, such advancements are difficult to quantify without testing and thus, there is a custom bladesmith named Al Warren who has done some testing of the new super steels by repeatedly slicing a 3/8” hemp rope to determine edge holding capabilities and to determine strength, he clamps a test blade in a vise with a protractor behind it and then bends the blade until it breaks. Then, he rates each steel on a scale of one to ten based upon the number of cuts the steel can make before being unable to cut all the way through the rope and the number of degrees it bends before breaking. Consequently, CPM S30V @ 58.5 HRC bent to 75 degrees and made 155 cuts whereas the same blade design made from ATS-34 only made 75 cuts and only bent to 45 degrees. Therefore, Al rates CPM S30V at 61 HRC as having a 10 in edge retention a 8 in strength, and an 8 in corrosion resistance while he rates BG-42 @ 62 HRC as having a 7 in edge retention, a 7 in strength, and a 10 in corrosion resistance, ATS-34 @ 61 HRC as having a 6 in edge retention, an 8 in strength, and a 6 in corrosion resistance, and 440C at 59 HRC as having a a 4 in edge retention, a 9 in strength, and a 10 in corrosion resistance.
So, as you can see, today’s modern super steels are indeed super because they far exceed the performance of the old blade steels in every category. The advantage a new super steel blade gives can make you feel like you are using a saw blade when compared to inferior blades. a A knife made from one of today’s “super steels” will likely amaze you with its performance.