O-1
This is a steel very popular with forgers, as it has the reputation for being "forgiving". It is an excellent steel, that takes and holds an edge superbly, and is very tough. It rusts easily, however. Randall Knives uses O-1, so does Mad Dog.
W-2
Reasonably tough and holds an edge well, due to its .2% vanadium content. Most files are made from W-1, which is the same as W-2 except for the vanadium content (W-1 has no vanadium).
The 10-series --
1095 (and 1084, 1070, 1060, 1050, etc.)
Many of the 10-series steels for cutlery, though 1095 is the most popular for knives. When you go in order from 1095-1050, you generally go from more carbon to less, from better edge holding to less edge holding, and tough to tougher to toughest. As such, you'll see 1060 and 1050, used often for swords. For knives, 1095 is sort of the "standard" carbon steel, not too expensive and performs well. It is reasonably tough and holds an edge very well. It rusts easily. This is a simple steel, which contains only two alloying elements: @.95% carbon and .4% manganese. The various kabars are usually 1095 with a black coating.
Carbon V
Carbon V is a trademarked term by Cold Steel, and as such is not necessarily one particular kind of steel; rather, it describes whatever steel Cold Steel happens to be using, and there is an indication they do change steels from time to time. Carbon V performs roughly between 1095-ish and O-1-ish, in my opinion, and rusts like O-1 as well. I've heard rumors that Carbon V is O-1 (which I now think is unlikely) or 1095. Numerous industry insiders insist it is 0170-6. Some spark tests done by a rec.knives reader seem to point the finger at 50100-B. Since 50100-B and 0170-6 are the same steel (see below), this is likely the current Carbon V.
0170-6 - 50100-B
These are different designations for the same steel: 0170-6 is the steel makers classification, 50100-B is the AISI designation. A good chrome-vanadium steel that is somewhat similar to O-1, but much less expensive. The now-defunct Blackjack made several knives from O170-6,
and Carbon V may be 0170-6. 50100 is basically 52100 with about 1/3 the chromium of 52100, and the B in 50100-B indicates that the steel has been modified with vanadium, making this a chrome-vanadium steel.
A-2
An excellent air-hardening tool steel, it is known for its great toughness and good edge holding. As an air-hardening steel, so don't expect it to be differentially tempered. Its outstanding toughness makes it a frequent choice for combat knives. Chris Reeve and
Hartsfield both use A-2, and Blackjack made a few models from A-2.
L-6
A band saw steel that is very tough and holds an edge well, but rusts easily. It is, like O-1, a forgiving steel for the forger. If you're willing to put up with the maintenance, this may be one of the very best steels available for cutlery, especially where toughness is desired.
M-2
A "high-speed steel", it can hold its temper even at very high temperatures, and as such is used in industry for high-heat cutting jobs. It is an excellent edge holder. It is tough but not as tough as some of the toughest steels in this section; however, it will still be tougher than the stainless steels and hold an edge better. It rusts easily. Benchmade has started using M-2 in one of their AFCK variations.
5160
A steel popular with forgers, it is extremely popular now and a very high-end steel. It is essentially a simple spring steel with chromium added for hardenability. It has good edge holding, but is known especially for its outstanding toughness (like L-6). Often used for swords (hardened in the low 50s Rc) because of its toughness, and is also used for hard use knives (hardened up near the 60s Rc).
52100
A ball-bearing steel, and as such is only used by forgers. It is similar to 5160 (though it has around 1% carbon vs. 5160 ~.60%), but holds an edge better. It is less tough than 5160 however. It is used often for hunting knives and other knives where the user is willing to trade off a little of 5160's toughness for better edge holding.
D-2
D-2 is sometimes called a "semi-stainless". It has a fairly high chrome content (12%), but not high enough to classify it as stainless. It is more stain resistant than the carbon steels mentioned above, however. It has excellent edge holding, but may be a little less tough than some of the steels mentioned above. And it does not take a beautiful finish. Bob Dozier uses D-2.
Vascowear
A very hard-to-find steel, with a high vanadium content. It is extremely difficult to work and very wear-resistant. It is out of production.
"STAINLESS" Steels:
Remember that all steels can rust. But the following steels, by virtue of their > 13% chromium, have much more rust resistance than the above steels. I should point out that there doesn't appear to be consensus on what percent of chromium is needed for a steel to be considered stainless. In the cutlery industry, the de-facto standard is 13%, but the ASM Metals Handbooks says "greater than 10%", and other books cite other numbers. In addition, the alloying elements have a strong influence on the amount of chromium needed; lower chromium with the right alloying elements can still have "stainless" performance.
420
Lower carbon content (<.5%) than the 440 series makes this steel extremely soft, and it doesn't hold an edge well. It is used often for diving knives, as it is extremely stain resistant. Also used often for very inexpensive knives. Outside salt water use, it is too soft to be a good choice for a utility knife.
440 A - 440 B - 440C
The carbon content (and hardenability) of this stainless steel goes up in order from A (.75%) to B (.9%) to C (1.2%). 440C is an excellent, high-end stainless steel, usually hardened to around 56-58 Rc. All three resist rust well, with 440A being the most rust resistant, and 440C the least. The SOG Seal 2000 is 440A, and Randall uses 440B for their stainless knives. 440C is fairly ubiquitous, and is generally considered the penultimate general-use stainless (with ATS-34 being the ultimate). If your knife is marked with just "440", it is probably the less expensive 440A; if a manufacturer had used the more expensive 440C, he'd want to advertise that. The general feeling is that 440A (and similar steels, see below) is just good enough for everyday use, especially with a good heat treat (we've heard good reports on the heat treat of SOG's 440A blades, don't know who does the work for them). 440-B is a very solid performer and 440-C is excellent.
425M - 12C27
Both are very similar to 440A. 425M (.5% carbon) is used by Buck knives. 12C27 (.6% carbon) is a Scandanavian steel used often in Finish puukkos and Norwegian knives.
AUS-6 - AUS-8 - AUS-10 (aka 6A 8A 10A)
Japanese stainless steels, roughly comparable to 440A (AUS-6, .65% carbon) and 440B (AUS-8, .75% carbon) and 440C (AUS-10, 1.1% carbon). AUS-6 is used by Al Mar. Cold Steel's use of AUS-8 has made it pretty popular, as heat treated by CS it won't hold an edge like ATS-34, but is a bit softer and may be a bit tougher. AUS-10 has roughly the same carbon content as 440C but with slightly less chromium, so it should be a bit less rust resistant but perhaps a bit tougher than 440C. All 3 steels have some vanadium added (which the 440 series lacks), which will improve wear resistance.
GIN-1 aka G-2. A steel with slightly less carbon, slightly more chromium, and much less moly than ATS-34, it is used often by Spyderco. A very good stainless steel.
ATS-34 - 154-CM
The hottest high-end stainless right now. 154-CM is the original American version, but for a long time was not manufactured to the high quality standards knifemakers expect, and so is not used often anymore. Late-breaking news is that high-quality 154-CM may again be available. ATS-34 is a Hitachi product that is very, very similar to 154-CM, and is the premier high quality stainless. Normally hardened to around 60 Rc, it holds an edge very well and is tough enough even at that high hardness. Not quite as rust resistant as the 400 series above. Many custom makers use ATS-34, and Spyderco (in their high-end knives) and Benchmade are among the production companies that use it.
ATS-55
Similar to ATS-34, but with the moly removed and some other elements added. Not much is known about this steel yet, but it looks like the intent was to get ATS-34 edge-holding with increased toughness. Since moly is an expensive element useful for high-speed steels, and knife
blades do not need to be high speed, removing the moly hopefully drastically decreases the price of the steel while at least retaining ATS-34's performance. Spyderco is using this steel.
BG-42
Bob Loveless announced recently that he's switching from ATS-34 to this steel. Keep an eye out for it, it's bound to catch on. BG-42 is somewhat similar to ATS-34, with two major differences: It has twice as much manganese as ATS-34, and has 1.2% vanadium (ATS-34 has no vanadium), so look for even better edge-holding than ATS-34. Chris Reeves has switched from ATS-34 to BG-42 in his Sebenzas.