[Combat-wombat]

What's the deal with different blade materials? How can you know which ones are high/low quality or whatever? How can I tell what AUS6 or 440C mean? (not specifically, just examples)

[SquirrelNuts]

Here is a quick rundown on my limited knowledge. I only know the numbers and manufacturers to buy, and those to keep away from.

The different numbers (ATS-34, 154-CM, S30-V, BG-42, etc.) tell you the steel's content, and possibly how it was made. You can determind the hardness, strength, and edge holding capabilities from these numbers.

Now, more importantly that the type of steel is how it was treated. Generally, 154-CM is a VERY good steel for an EDC folder, but it is the way it is treated and tempered that makes the difference. For example, you can get a good 154-CM folder for $100, but a 154-CM Masters Of Defense will run you $200, simply because of the way they treat the metal. So you can find good and bad in each steel type.

-SquirrelNuts

[Jim March]

There's an entire FAQ on this subject - go post over at www.bladeforums.com and you'll get a pointer to it.

Your SOG is AUS6, one of the "lowest" grade stainlesses...but SOG heat-treats it well and the result both works, and is "extremely, marine-grade stainless".

The three main classes of steels:

"Conventional high-carbon steels" are what a classic sword was made out of, or any knife of any quality made in the 1960s or prior. These include the 1060/1084/1095 series (where the last two digits indicate percentage of carbon, .60%, .84% or .95%), 5160 (automotive leaf spring steel, my favorite sword steel) and a few others. These "primitive" steels can be "recycled" by heat-treating 'em back to soft, massaging 'em as needed and then re-heat-treating.

These steels are still used for any big, tough blade - swords, large Bowie knives and anything else that must not break.

"Tool steels" are more modern: D2, A2, 01, L6 and the like. Expensive, they eat grinder belts/disks like crazy, which drives the prices up. You get what you pay for. D2 is a "borderline stainless" - not a true stainless, but close. 5160, in the same fashion, is a "borderline tool steel"...not quite, but close. L6 is what lumbermill saw blades are made of and is "simple enough" to be compatible with heat'n'beat (see below).

"Stainless" - the best stainlesses are "borderline tool steels", such as ATS34/154CM (more or less the same thing), BG42 and per some definitions 440C. There's also 440B, 440A, AUS6/8 and a bunch of others. Most of these, and some of the tool steels, are "one shot only" on the heat-treat - once the heat-treat cycle is done, you can't heat it back up to soft and start over, they're "ruined" if you do. The exception is 440B. There is also an entire family of "crucible particle metallurgy" (CPM) steels like 440V, 420V and the like which are VERY good stuff indeed.

There are also "Cobalt alloys" which aren't "steels" because there's no iron content :). Talonite is now the most common. Titanium blades are also not "steel".

Knife blades are created with one of two methods: "stock removal" in which you take a block of steel and grind away whatever isn't a knife, or the more traditional "heat'n'beat" (forged) where you get it hot and pound it into shape. For the latter, you must use a steel that can be re-heated. All Randalls are heat'n'beat, and on their stainless fishing knives, they use 440B...so far as I'm aware, they're the only ones doing heat'n'beat stainless.

The higher-tech steels are only compatible with grinding. One of the problems is that if they're "burned" at the grinding wheel (like they get stuck in one of the assembly-line robots) then a part of the steel will get, effectively, "heat treated" in that one spot. Then once finished and the full heat-treat is performed, in that one spot you've got a brittle point and possible failure down the road. This is NOT common, but it can happen.

Which is why, when I got the opportunity to own a hand-ground ATS-34 folder, I decided to actually carry it on the street and for the last three years, have done so. When Bob Brothers ground it, he used his bare hands so that as the blade heated, he'd have to stop and cool it. So the "one shot at a heat-treat" was never "spent" at the grinding wheel. It then got the Paul Bos-type heat treat which in my opinion isn't as good as the Ernie Mayer/Hitachi process, but it's adequate :D.

What else...OH YA, "Damascus" (really "pattern welded"). Take two steels, soften 'em up, twist 'em together a whole lot, and one school of thought says you get the best features of each steel. Another opinion says you've got a blade riddled with hairline fractures. I lean towards the latter, unless you spend MAJOR bucks.

One last one: by some accounts, the genuine, original "Damascus" steel has been rediscovered, and is usually called "Wootz" steel. It has enormous amounts of carbon in it, up around 2.5% or so. Carbon hardens steel. Real middle eastern "Damascus" steel was the stuff that drove the Crusaders crazy, when the Arab swords could go right through much of their armor. (We don't know how much of that was the steel, and how much was the Arab trick of making swords that were hollow and filled with a couple pounds of mercury(!) which "sloshed around in there" and changed the balance depending on what you were doing.)

[Guyon]

Have a look:

http://www.agrussell.com/rec.knives/steel.html

I'm beginning to see that makers are using a high end steel called S30V, particularly Spyderco. Anybody know much about this steel?

[mete]

Guyon, I have ordered a camillus dominator which uses S30V. This is one Cricible steels CPM steels but unlike the others is specifically made for knives. It is better than 154cm. Most good knife steels are for other purposes like BG42 which is a bearing steel. ------Jim March, I wish you could document the arab mercury swords, I'll bet it's a myth . I'm sure they would like to hear about it on swordforum.com.

[Jim March]

Hrrrrm. Well I read that somewhere...

Am doing lots of googling trying to sort it out.

[Jim March]

Oh man. Looks like some idiot I read years ago adapted it out of an old fantasy story. Sigh. A fantasy author I'd never read.

Sigh.

Embarassing, it is.

I was right about Wootz though :). And I did OK on everything else :o.

[SquirrelNuts]

I have a Microtech UMS (I think that's what it is called) Automatic. It is made with S30V steel. My understanding is that the steel is very well mixed because it begins life as a powder and is melted that way, rather than sheets.

I got a card from Spyderco at the Blade Show that has the percentages of roughly a dozen meterials in a particular type of steel. S30V is similar to 154CM

-SquirrelNuts

[grenadier]

There's also the process of cryotempering, where a blade is subject to liquid nitrogen temperatures.

http://www.imperialweapons.com/shared/cryo.html

Very impressive...

[mete]

Grenadier, you are impressed with cryo ? I always say that much of cryo is nonsense. For example the website you list has comments from a research metallurgist with the NBS. Does that impress you ? When I read on he mentions that cryo produces a "denser molecular structure" ,still impressed ? Well he's not much of a metallurgist Why ? Well I am also a metallurgist and at least I know (from chemistry 101) that METALS DO NOT HAVE MOLECULES. If he doesn't know that I don't read any further. But as I said much of cryo is nonsense.

[hso]

Well no one has mentioned Joe's FAQ on this yet.
http://www.bladeforums.com/features/faqsteel.shtml

Here's Spyderco's
http://www.spyderco.com/education/steelprod.asp?sts=6%2F29%2F2003+10%3A27%3A50+PM&mscssid=DMLC9CHHRU5N9JRMBKBP4QUCGQDN6QLC

Crucible's
http://www.crucibleservice.com/cutlery.cfm

Heat treat and edge geometry matter almost as much as steel type (perhaps more). A knife with properly heat treated 440C with an edge geometry to match the task will outperform many of the "super" knives out there with ATS 55 and S30V steels.

[Jim March]

One theory with Cryo-treat: if it's a relatively simple steel, such as 1095 high carbon, cryo does very little.

With at least SOME of the more complex steels, apparantly including ATS-34, it can have a more serious impact.

[MAURICE]

I do want to mention that the blade steel does NOT make the knife. To have a quality blade you MUST have a good HT, Decent steel, and Proper edge geometry. An excellent HT on say 440c will beat the crap out of a mediocre HT on 154cm. Do your homework, read, read,and read. Check out Bladeforums.com , look for the knife encyclopedia at agrussell.com and study steel charts- these will tell you the molecular breakdown of different steels and you will soon learn what makes a good steel...well....good.

Any more questions, just ask.
MAURICE

[mete]

Maurice, "molecular breakdown"? Please read my prevoius post --metals do not have molecules !! There are always two problems with steel - picking the steel and heat treating it. The stainless knife steels in order of their effectiveness - 440c, 154cm, BG42 ,S30V. But they must be heat treated properly.

[Baba Louie]

mete,

Metals don't have molecules? Then what is their molecular structure composed of? What is austenite and all those other ...ites if not some form of crytallization of... a bunch of atoms???

I'm a bit of a simpleton and only slightly confused in my middle years. When I was much younger I knew everything. But it seems, the farther away from my educational background I travel, the dumber I become.

Adios

[mete]

Baba, they don't have molecules, they don't have molecular structure, they don't have molecular bonding. They DO have atoms ,crystals,grains and metallic bonding. Metallic bonding is the key, this is what makes them metals - conduct electricity etc.

[Baba Louie]

mete,

yeah, ya learn something every day I tell ya.

I did a google search and came up with all kinds of scientific reports/studies, etc concerning molecules and metal... way over my head.

I believe I should have paid better attention in H.S. Chem. Biology was my favorite between the two.

Kind of fascinating in a twisted way. Molecules in glass are always moving??? Weird.

Life goes on.

Thanks for the information

Adios

[Joe Talmadge]

http://groups.google.com/groups?q=group:rec.knives+insubject:Steel+insubject:FAQ+author:Joe+author:Talmadge&hl=en&lr=&ie=UTF-8&as_drrb=b&as_mind=20&as_minm=6&as_miny=2003&as_maxd=2&as_maxm=7&as_maxy=2003&selm=s28Ka.11148%24Fy6.4368%40sccrnsc03&rnum=1

Hopefully that long URL above will work out, it's a link to the newest version of the Steel FAQ, comments/critiques always appreciated. I think it's much improved from the version on bladeforums, I'll have bladeforums update their version inthe next week or two.

Joe

[hso]

Thanks Joe.

[Kentucky Rifle]

I've got a Spyderco stainless steel scale "Cricket" with a VG-10 stainless blade and a Sebenza with BG-42. I carry both daily and use both frequently. They've never needed sharpening. Pretty good performance, I'd say. When I fly, the Sebenza gets swapped for a 50/50 Spyderco Titanium "Salsa" with an ATS-34 stainless blade. If I have to cut a stuck seat belt, I figure the serratons will make short work of it. I've never had to sharpen the Ti Salsa either, as it's a "dedicated flying knife".

KR