By definition, steel is a combination of iron and less than 2 percent
carbon. For centuries, carbon was the only alloying element. The problem in the
early days of steel making was getting rid of unwanted elements, not adding new
ones. However, there are a variety of alloying elements that are added to
modern steels to impart various characteristics.
Iron alone is relatively soft. It does not hold an edge well, wears
quickly and has little resistance to bending. Add a little bit of carbon and
the story changes dramatically. The carbon combines with the iron to form hard
carbide platelets cemented together in a matrix of iron. The combination is
resistant to wear and bending and will take a keen edge.
Smaller carbides and a tighter grain structure allow for a stronger,
sharper edge. Other carbide formers, like vanadium, can refine the grain of the
steel further. Knives with a high vanadium content can take a very keen edge,
but are harder to sharpen.
Carbon - Present in all steels, it is the most vital hardening element.
Greater than 0.5 percent carbon content qualifies a steel as a “high carbon”
steel.
Chromium - Added for wear resistance and corrosion resistance. A steel
with at least 13 percent chromium is considered “stainless.” Chromium is a
carbide former, so it also increases wear resistance.
Manganese - A carbide former. Manganese aids grain structure, increases
hardenability, and wear resistance. Manganese is present in most cutlery
steels.
Molybdenum - Another carbide former. Increases hardness, prevents
brittleness, makes the steel easier to machine.
Nickel - Adds toughness and possibly aids in corrosion resistance.
Phosphorus - Essentially a contaminant.
Silicon - Increases hardness and strength.
Sulfur - Increases machinability but decreases toughness.
Tungsten - Increases heat, wear and shock resistance. Tungsten is the
strongest carbide former behind vanadium.
Vanadium - Another carbide former. Contributes to wear resistance and
hardenability. Vanadium refines the grain of the steel, which contributes to
toughness and allows the blade to take a very sharp edge.
Most kitchen knives fall into the category of “high carbon stainless.”
These knives generally contain between 0.5 and 0.8 percent carbon, 13 to 18
percent chromium and a little manganese, molybdenum, silicon, phosphorus and
sulphur. This makes for a steel that is easy to produce, is very stain resistant
and reasonably wear resistant. Knives from Global and Mac’s Superior line have
some vanadium added for improved wear resistance and a finer grain, which
allows the knife to be sharpened to an incredible edge.
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