Characteristics of Various Steels used for Cutlery
Steel in its simplest form is a combination of iron and carbon creating basic carbon steel. Modern steels contain other elements in specific combinations to enhance the properties of the material. Some of the most common of these elements, and their functions are:
Chromium - Improves corrosion resistance, stainless steels will have significant amounts (usually greater than 13%) of chromium.
Small amounts of Chromium can also increase the strength of the blade
Cobalt - Improves the strength of the steel.
Manganese - Can make the steel harder, but more brittle.
Molybdenum - Allows the steel to perform better at high temperatures.
Nickel - Makes for a tougher steel.
Phosphorus - Adds strength to the steel.
Sulfur - Increases machinability but usually decrease toughness.
Tungsten - Increases wear resistance of the steel.
Vanadium – Makes the steel harder and increases wear resistance.
Steel with some combination of the above elements is referred to as an 'alloy carbon steel' commonly referred to simply as carbon steel. These elements give a steel its specific properties such as toughness, hardness and wear resistance.
Stainless steel is any alloy steel with a significant percentage of chromium to make it corrosion resistant. They are generally defined as containing more than 13 percent chromium. Stainless steels vary as to how corrosion resistant they are. Some are better than others and often trade off various qualities such as hardness and toughness for corrosion resistance. Under the right circumstances however almost all stainless steels will eventually corrode (rust). One of the few exceptions being the Nitrogen based steels that contain no carbon.
These are true corrosion proof (rust proof) steels. However, there is a trade off for this feature.
A few examples of various steels used by knife manufacturers that you may encounter:
Alloy Carbon Steel
The 10xx series includes a large variety of steels including the very common 1080 and 1095 steels.
A few other common carbon steels include 5160, A2, and D2.
Basic Stainless Steels
Very common and inexpensive stainless steels used for decades to make stainless knives.
The 420 and 440 series of stainless steels fit this description perfectly. These steels are very rust resistant, making them ideal for inexpensive kitchen knives. However, knives made of these steels dull rather quickly because of trade offs made for the very good corrosion resistance and low cost. The high end of this series is 440C.
Particle (powdered) Steel.
Using the latest technology, these steels represent a new generation of high performance steel. Commonly referred to as "Super Steel" they have enhanced properties that older steels cannot match. But they also come at a premium price.
Unlike many other steels adapted form other industries this steel was designed to be used for knives. It is tough for a stainless steel, and has excellent wear resistance and good harness. This and it's newer slightly refined version S35VN are used in a lot of very high quality knives by many makers
This stainless steel has fantastic edge retention. And because of this it is very hard to sharpen with conventional sharpening equipment. Very few retail manufactures use it because it is very hard to machine and expensive. Most knives using this steel are either from custom makers or high end manufacturers. A newer variation of this steel CPM-S110V shares many of these characteristics. Either of these will provide blades that rarely need sharpening even after prolonged use.
These two nearly identical stainless steels are arguably the best all around knife steels with excellent edge retention, toughness and superior excellent corrosion resistance. The best part being that the blades made of these steels are relatively easy to sharpen and will take on a mirror polish and hair splitting sharpness
CPM-M4 and CPM-3V
While giving up some corrosion resistance (more so for M4) These are some of the toughest steels available. They are typically used in larger knives and will take a beating without chipping and breaking. Although very tough their edge retention is exceptional.
There are dozens, if not hundreds, of steels now available offering various features and qualities that have not been discussed in this brief summary.
Properties of Steel used for Knives
Hardness - The steel's ability to resist deformation (bend, buckle or fold) Refereed to as the Rockwell hardness.
Toughness - The blade steels ability to resist chips and total failure when subjected to beating, impact, twisting, and torsion.
Sharpness - The ability to sharpen the steel to extreme sharpness.
Ease of Sharpening - The ability to easily re-sharpen a dull blade
Edge Retention - The ability of the steel blade to hold a fine edge without frequent resharpening
Corrosion Resistance - The ability of the steel to resist corrosion (rusting) in adverse environments.
Wear Resistance - The ability to resist wear and abrasion which impacts edge retention.