Blade steel, the metal used to make blades for knives, is manufactured from a combination of elements that provide the specific features the manufacturer is looking for. Typically, the most common blend is iron and carbon with other materials like chromium, molybdenum, vanadium or manganese.
When deciding which type of blade is best, the job it will be doing is the most important factor. There are a variety of materials which, when combined, will provide the features you most need. While the basic materials used are very important, so is the process used to create the blade. The table below includes some of the more popular types of materials used to create blades. Since some of the terminology is confusing, the following paragraphs explain the terms.
The basic shape of the blade is achieved through forging, stock removal or stamping. In forging, a method usually reserved for high-end blades, the single piece of steel is heated to a high temperature and then hammered to the required shape. This method is most often used in creating custom blades. The stock removal method is the process of grinding steel to turn it into a blade. Blades can also be stamped out of stainless steel sheets. When using more resilient or more complex types of steel, sophisticated equipment like water jet cutters or lasers are used.
After the blade has been honed to its final shape, it is tempered. It is heated to a temperature above the critical point to make the blades more durable, but they will not hold an edge well. It is possible to temper at lower heat to produce a harder knife that will keep an edge longer, but it will be more brittle and more likely to break. When it has been heated sufficiently, it is quenched, or cooled rapidly, to harden it.
Laminate blades are created using multiple layers of different metals, like a sandwich, to take advantage of features of each. Pattern welding is similar, but the product is manipulated after the sandwich is formed, so patterns appear in the steel.
Stainless steel blades must contain at least 13% chromium, which provides the corrosion resistance. By increasing Chromium and reducing Carbon, the steel becomes more resistant. The caveat is that it cannot hold an edge as well, so these blades are not as razor-sharp as non-stainless steel blades.
Carbides, an alloy of carbon and iron, are the hard particles formed when carbon bonds with iron. The type and volume of carbide affects the wear resistance and toughness in steel. Because it is very hard, increasing high volumes of carbides in the mix will make steel brittle. Knives with high edge stability stay sharper longer and make good kitchen knives. When the amount of carbides is increased, the wear resistance is improved, but the toughness and edge stability are reduced.
Strength refers to the ability to resist deformation and rolling, important factors if the knife needs to be sharpened to a fine edge. Important factors in obtaining greater strength are grain size and the alloy used. Cobalt strengthens the steel. In general, the strength and toughness of steel are in direct opposition. If it is tough, it is not strong with an important factor being the grain size.
Toughness is the ability to resist chipping or breaking and is affected by the amounts of carbide and chromium as well as the hardness to which the steel is heat-treated. Nickel and silicon are often added to increase toughness.
Wear resistance is the ability of the metal to resist abrasion. This is particularly important for slicing hard materials. High wear resistance makes the steel more difficult to sharpen. When slicing through softer materials, the edge stability, strength and toughness are more important.
The grain size affects toughness and strength. The smaller the grain, the more these attributes are increased. Heat treatments and forging processes influence the grain size as well as carbide types and the alloy melting point. Using products with a higher volume of carbides and alloys that have high melting points keep grains smaller. Adding Vanadium and Niobium can be added to aid in retaining the small grain size.
Cryogenic Quenching is the process of freezing blades to -120 degrees Fahrenheit to improve blade performance.
When a knife blade has been formed, it needs to be dressed. Dressing refers to treating the surface of the blade, and includes any coatings that are applied.
Satin finishes have low-luster sheen and include several levels of luster. Stonewashed satin is when the blade is literally tumbled with small stones to create a scratched finish. Scotchbrite finishes blend the grinding lines to produce a grained or brushed effect. Usually, the pattern is from the spine to the edge of the blade.
Tumbled or Vibed finishes are similar to stonewashed, a low luster with a random scratching pattern. Burnished metals have a plastic that is smeared to make portions of it shinier. Hand rubbed finishes are not usually found on mass-produced blades. The graining goes from tang to the tip.
Polished finishes are reflective, glossy finishes that smooth the surface. It aids in corrosion because there is less surface is exposed. Bead blast or military finishes are non-reflective and are created by sandblasting the blade. The surface is rougher to reduce glare. It is more likely to corrode because there is more surface area exposed.
Here is a listing of some of the more popular metals used in knife blades. Some steels are proprietary, owned by a specific company. They sometimes sell their steel to be used in products from other manufacturers.
|1095||A popular, plain carbon steel that is easy to sharpen.|
|154CM||Made in America, this premium stainless steel was developed for turbine blades in jets and other industrial uses. It is corrosion resistant with good toughness and edge quality. Similar to ATS-34.|
|420||A lower grade of stainless steel used for display knives, it is not suitable for actual use.|
|420HC||A better grade of stainless steel that has high carbon content.|
|420J2||An inexpensive, highly corrosion-resistant knife used in inexpensive or diving knives.|
|440A||A high-carbon stainless steel used in mass produced knives.|
|440C||Stainless steel with high chromium content, typically used for mass-producing general-use knife blades. It is tough and stain resistant, holds an edge well and is easy to sharpen. Similar to N690.|
|5160||Spring steel is a popular forging steel for manufacturing sword blades and large knives. It has high toughness and good wear resistance.|
|52100||Ball bearing steel has good toughness. It has fine carbides, which produce high edge stability. Often used in creating custom knives.|
|8Cr14MoV||Steel made in China with medium carbon and high chromium levels. It produces a tough blade with good edge sharpness and is very corrosion-resistant. Provides excellent value for the price. Similar to AUS-8.|
|8Cr14Mov||Steel manufactured in China that produces a tough blade with good edge sharpness, which is highly corrosion-resistant. Similar to AUS-8|
|9Cr13CoMoV||Manufactured in China, a stainless steel with high carbon content. Cobalt is added for better edge retention. It offers high level of corrosion resistance at a reasonable price.|
|A2||Wear-resistant steel that does not rank high in toughness. It is often used in custom fighting knives.|
|ATS-34||Japanese stainless steel with 1.04% carbon content. It is not as rust-resistant to 440c, but holds an edge better. Similar to 440C.|
|AUS-8||Made in Japan, this stainless steel has medium carbon and high chromium levels. The blade is tough, has good edge sharpness and is very corrosion-resistant. Similar to 8Cr14MoV.|
|BG-42||Stainless steel with a good edge-holding ability, better than 44C. It is more durable than ATS-34.|
|Bohler M390||Performance steel with high levels of vanadium and chromium carbides. It offers superior cutting ability and durability. The powder metallurgical creates a uniform carbide distribution. It is often used in surgical instruments and for blades with a high finish.|
|Bohler N680||This is stainless steel made with chromium, molybdenum, vanadium and nitrogen. It has excellent corrosion resistance, even in salt water. It also feature good hardness, high wear resistance and the ability to preserve sharpness.|
|Ceramic||Ceramic blades are brittle and difficult to sharpen. They hold an edge well but chip easily.|
|CPM-M4||Powder metal, non-stainless steel with Carbon, Molybdenum, Vanadium and Tungsten. Excellent durability and toughness.|
|D2||Durable, air-hardened tool steel with a very high, 1.5%, carbon content and an excellent ability to hold an edge. It has low chrome levels, 12%, so it is does not rate high in toughness and corrosion-resistance.|
|Damascus||A costly type of steel that is created in layers, which offers very good toughness and edge quality. An acid etch reveals the surface layers. Most of the uses involve its visual appeal, as in collectible, artistic pieces. This is also the name of an ancient crucible steel.|
|H1||Japanese steel that is extremely corrosion-resistant. Edge quality is sacrificed for corrosion resistance and toughness. It is often used for diving knives.|
|M2||Extremely tough, tool grade steel used primarily in industrial settings because it can keep a tempered edge at high temperatures. Superb strength and extremely wear-resistant, but low corrosion resistance. It is used in custom knives designed for fine cutting with thin edges.|
|N690||Austrian made stainless steel with keen edge qualities and very good corrosion resistance. Similar to 440C.|
|O1||Popular forging steel for custom knives with good wear resistance and edge stability.|
|Obsidian||Blades made from obsidian were used by American Indians.|
|S30V||A premium grade, American-made stainless steel that was designed especially for use in manufacturing knives. Powder made steel with uniform carbide distribution, excellent corrosion resistance and superb edge qualities.|
|Titanium||Used for diving or bomb knives because it is rust-resistant and non-magnetic. It is not recommended as the sole metal in the blade because it does not take an edge well. Some manufacturers use it as a coating. Gerber’s Fine Edge Titanium Nitride Pocket Knife is an example of titanium coating.|
|X15||Steel developed in France for ball bearings used in jets and scalpels. Extremely resistant to corrosion, particularly saltwater environments, with good edge retention|