Knife Blade Materials
Steel Specifics (text courtesy of Cold Steel, Inc. and Buck Knives)
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 (plates, coils, etc.). Buck Knives uses plates and coils, depending on the type of steel and its thickness. Plates are turned into knife components by laser cutting and coils are shaped into components using a fine blanking press.
Properties of Steel
The selection of steel for specific applications is based on the properties of the steel and other factors like manufacturabilityif 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 heat-treating process)
- 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 frequent resharpening
- 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, Buck Knives selects 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, 420HC and 420J2 are all martensitic stainless steels.
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 steel's properties.
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.
Types of Steel
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.
Blade Steels used (courtesy of Buck Knives)
S30V - Developed primarily for the cutlery industry by Crucible Steel, S30V contains noticeably higher amounts of Carbon and Vanadium than does BG-42. This increase in Carbon and Vanadium provides superior edge-holding and abrasion resistance. S30V is the best blade steel available today.
- Superior edge holding
- Improved ductility
- Good hardness- ideal range Rc 59.5-61
- Good corrosion resistance
- Very high amounts of Carbon and Vanadium
BG-42 - A proprietary alloy of Timken Latrobe Steel, BG-42 is a high-performance, bearing-grade martensitic stainless steel used in the aerospace industry. Because of its high strength and ability to reach high Rockwell hardness (Rc 61-62), BG-42 is well suited for blades that are subjected to extreme use.
- Very good edge holding ability
- High strength
- Rockwell Rc 61-62
- Fair corrosion resistance
- Contains Vanadium, improving hardenability and a fine grain structure
|1.15||.3||13.50 - 14.50||4.0||1.20|
154CM 154CM is a very high carbon stainless steel with the addition of Molybdenum. Because 154CM provides better edge retention than standard cutlery (stainless) steels, it is a good choice for blades that require heavier cutting applications.
- Very good edge holding ability
- Rockwell Rc 60-61
- Good toughness when double tempered
- Fair corrosion resistance
- Less expensive than BG-42 and S30V
|1.05||.35||13.50 - 14.00||4.0|
420HC - 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 when heat-treated with our proprietary Paul Bos heat-treat process.
- Good edge holding ability
- Resharpens well
- Rockwell Rc 58
- Good toughness
- Very good corrosion resistance
- Excellent standard knife steel
|12.00 - 14.00||1.0|
420J2 - A lower carbon content, general-purpose stainless steel. 420J2 has fair hardness and corrosion resistance and high ease of resharpening. 420J2 is suited for knife blades with light to medium use and routine applications.
- Resharpens well
- Rockwell Rc 56-58
- Good manufacturability
- Good corrosion resistance
|12.00 - 14.00||0.80|
17-7 PH - A Chromium/Nickel/Aluminum, precipitation-hardening, stainless steel. The alloy is used for high-strength applications requiring resistance to salt-water corrosion. 17-7PH offers a good compromise between Martensitic stainless steels (heat-treatable) and Austenitic (300 series) stainless steels (non heat-treatable). This is due to the high Chromium/Nickel/Aluminum content.
- Moderate edge holding
- Very good toughness
- Excellent corrosion resistance
- Rockwell Rc 54-56
|Steel Type||Edge Retention||Ease of Resharpening||Corrosion Reisitance|
OTHER BLADE STEELS (courtesy of Cold Steel, INC)
AUS-8 (also referred to as 8A) (some text courtesy of Cold Steel, Inc.)
The words "stainless steel" are misleading, because, in fact all steel will stain or show discoloration if left in adverse conditions for a sufficient time. Steel is made "stainless" by adding Chromium and reducing its Carbon content during the smelting process. Some authorities claim that there is a serious performance trade off with stainless steel: As the Chrome increases and the Carbon decreases, the steel be comes more "stainless". But it also becomes more and more difficult to sharpen and, some claim, the edge-holding potential is seriously impaired. We have found that most stainless steel blades are as sharp as other material blades and hold the edge longer. AUS 8A is a high carbon, low chromium stainless steel that has proven, over time, to be a very good compromise between toughness, strength, edge holding and resistance to corrosion.
Premium grade of stainless steel used by most custom knifemakers and upper echelon factory knives. It is Japanese steel, owned by Hitachi Steels. The American made equivalent of ATS-34 is 154CM, a steel popularized by renowned maker Bob Loveless.
GIN-1 (formerly known as G2)
Another low cost steel, but slightly softer than AUS-8.
Sometimes touted as the "super steel", it outlasts all stainless steels on the market today. It is, however, harder to resharpen (due to its unprecedented edge retention). But the tradeoff is that you do not have to sharpen as frequently. CPM-T440V is widely used by custom knifemakers and is slowly finding its way into high-end factory knives.
420J2 (text courtesy of Cold Steel, Inc.)
Due to its low carbon high chromium content this steel is an excellent choice for making tough (bends instead of breaking), shock absorbing knife blades with excel lent resistance to corrosion and moderate edge holding ability. It is an ideal candidate for knife blades that will be subject to a wide variety of environmental conditions including high temperature, humidity, and airborne corrosives such as salt in a marine environment. This extreme resistance to corrosion via its high chrome content also makes it a perfect choice for knife blades which are carried close to the body or in a pocket and blades which will receive little or no care or maintenance
San Mai III® (Cold Steel products)
San Mai means "three layers". It's the term given to the traditional laminated blades used by the Japanese for swords and daggers. Laminated construction is important because it allows different grades of steel to be combined in a single blade. A simple way to think of this type of construction is to imagine a sandwich: The meat center is hard, high carbon steel and the pieces of bread on either side are the lower-carbon, tough side panels. The edge of the blade should be hard to maximize edge holding ability, but if the entire blade was hard it could be damaged during the rigors of battle. For ultimate toughness the body of the blade must be able to withstand impact and lateral stresses. Toughness is generally associated with "softness" and "flexibility" in steel, so that, surprisingly, if a blade is made "tough" the edge won't be hard enough to offer superior edge holding. San Mai III® provides a blade with hard (higher carbon) steel in the middle for a keen, long lasting edge and tougher (lower-carbon) steel along the sides for flexibility.
VG-1 Stainless Steel (Cold Steel products)
Physical testing for sharpness, edge retention, point strength, shock, and ultimate blade strength showed that VG-1, showed the greatest performance increases in ability to retain an edge and proven strength in point and blade tests, VG-1 will provide Cold Steel® customers with superior performance previously unavailable in a stainless steel blade.
4116 Krupp Stainless Steel (Cold Steel products)
4116 is a fine grained, stainless steel made by ThyssenKrupp in Germany and is used for hygienic applications (medical devices and the pharmaceutical industry) and food processing which make it a superb material for kitchen cutlery. The balance of carbon and chromium content give it a high degree of corrosion resistance and also impressive physical characteristics of strength and edge holding. Edge retention in actual cutting tests exceeded blades made of the 420 and 440 series of stainless steels. Other alloying elements contribute to grain refinement which increase blade strength and edge toughness and also allow for a finer, sharper edge.
1055 Carbon Steel (Cold Steel products)
1055 steel is right on the border between a medium and a high carbon steel, with a carbon content between 0.50%-0.60% and with manganese between 0.60%-0.90% as the only other component. The carbon content and lean alloy make this a shallow hardening steel with a quenched hardness between Rc 60-64 depending on exact carbon content. These combination of factors make this one of the toughest steels available because, when quenched, it produces a near saturated lathe martensite with no excess carbides, avoiding the brittleness of higher carbon materials. This steel is particularly suited to applications where strength and impact resistance is valued above all other considerations and will produce blades of almost legendary toughness.
SK-5 High Carbon Steel (Cold Steel products)
SK-5 is the Japanese equivalent of American 1080, a high carbon steel with carbon between 0.75%-0.85% and 0.60%-0.90% manganese. As quenched, it has a hardness near Rc 65 and produces a mixture of carbon rich martensite with some small un-dissolved carbides. The excess carbide increases abrasion resistance and allows the steel to achieve an ideal balance of very good blade toughness with superior edge holding ability. Due to these characteristics, this grade of steel has been used traditionally for making a variety of hand tools, including chisels and woodcutting saws, and has stood the test of time and use over many years in many countries.