Steel Alloys:
At its most simple, steel is iron with carbon in it. Other alloys are added to make the steel perform differently. Here are the important steel alloys in alphabetical order, and some sample steels that contain those alloys:
Carbon: Present in all steels, it is the most important hardening element. Also increases the strength of the steel. We usually want knife-grade steel to have >.5% carbon, which makes it "high-carbon" steel.
Chromium: Added for wear resistance, hardenability, and (most importantly) for corrosion resistance. A steel with at least 13% chromium is deemed "stainless" steel. Despite the name, all steel can rust if not maintained properly.
Manganese: An important element, manganese aids the grain structure, and contributes to hardenability. Also strength & wear resistance. Improves the steel (e.g., deoxidizes) during the steel's manufacturing (hot working and rolling). Present in most cutlery steel except for A-2, L-6, and CPM 420V.
Molybdenum: A carbide former, prevents brittleness & maintains the steel's strength at high temperatures. Present in many steels, and air-hardening steels (e.g., A-2, ATS-34) always have 1% or more molybdenum -- molybdenum is what gives those steels the ability to harden in air.
Nickel: Used for strength, corrosion resistance, and toughness. Present in L-6 and AUS-6 and AUS-8.
Silicon: Contributes to strength. Like manganese, it makes the steel more sound while it's being manufactured.
Tungsten: Increases wear resistance. When combined properly with chromium or molybdenum, tungsten will make the steel to be a high-speed steel. The high-speed steel M-2 has a high amount of tungsten.
Vanadium: Contributes to wear resistance and hardenability. A carbide former that helps produce fine-grained steel. A number of steels have vanadium, but M-2, Vascowear, and CPM T440V and 420V (in order of increasing amounts) have high amounts of vanadium. BG-42's biggest difference with ATS-34 is the addition of vanadium.
CARBON and alloy steels (non-stainless steels):
These steels are the steels most often forged. Stainless steels can be forged (guys like Sean McWilliams do forge stainless), but it is very difficult. In addition, carbon steels can be differentially tempered, to give a hard edge-holding edge and a tough springy back. Stainless steels are not differentially tempered. Of course, carbon steels will rust faster than stainless steels, to varying degrees. Carbon steels are also often a little bit less of a crap shoot than stainless steels -- I believe all the steels named below are fine performers when heat treated properly.
In the AISI steel designation system, 10xx is carbon steel, any other steels are alloy steels. For example, the 50xx series are chromium steels. In the SAE designation system, steels with letter designations (e.g., W-2, A-2) are tool steels.
There is an ASM classification system as well, but it isn't seen often in the discussion of cutlery steels, so I'll ignore it for now. Often, the last numbers in the name of a steel are fairly close to the steel's carbon content. So 1095 is ~.95% carbon. 52100 is ~1.0% carbon. 5160 is ~.60% carbon.
|