View Full Version : What about L6


Sethhoward
05-21-2003, 03:54 PM
I have seen a few people singing the praises of L6. I am used to forging 1084 and 5160. What differences / benifits should I expect to see with L6.

Seth

whv
05-21-2003, 08:50 PM
per kevin cashen: http://www.cashenblades.com/Info/Steel%20selection/L6.html
it is supposed to be tough stuff good for large blades by itself. because it contains 1.5pct nickel, folks use it with 10xx for damascus.

T. Hendrickson
05-22-2003, 11:31 AM
I would like to hear more on this thread.

Kevin R. Cashen
05-23-2003, 05:35 PM
In the forging you will find L6 just a little bit stiffer under the hammer but after working it for years I myself don't even notice it until I go to 1084 or something similar.

The real big difference that keeps it off most peoples list is the lengths one must go to to get it soft (annealed). Without a lot of paitience and incredibly accurate controls you can pretty much forget a traditional lamellar anneal (pearlite). I have the cotrol and still don't mess with lamellar. The best way to go is to spheroidize it, but this also requires some control on your heating.

I did a demo one year at the Ashokan seminar in which I heated both a bar of L6 and a bar of 1095 to critical and then simultaneously put hem in wood ash. Several hours later, during the second half of the lecture, I bent them both(or tried). The 1095 folded completely over with no problem the L6 snapped clean at around 30 degrees. It was almost completely martensitic using the "standard" bladesmith anneal.

I have since done some further testing on 1/2-3/4" thick bars that I heated to critical and threw on my shop floor to cool. Most of the bars were 61HRC from just air cooling (and a little help from the concrete). If you do not spheroidize this tuff will eat up belts and squeek a blunt end onto anything but a diamond drill bit. Believe me, I speak from experience.

So why put up with the headache? Because foot pound for foot pound L6 will out do just about any other "edge holding" steel in impact strength. I have done, and continue to do, many tests in this area and the stuff still amazes me with the energy it can absorb at relatively high hardnesses. This equates to a very strong knife that does not have to be soft to do it.

In pattern welded mixtures it will give the most beautiful silver contrast you could want and I have found that in the right temperature range it welds like a dream. I could swear that if you heat it to 2100F. and flux it up then throw it agianst the wall it would stick!

It heat treats like a dream! To get a lot of pearlite in a quenched L6 you may have to be the worst heat treater alive. It responds very well to low temp salts and is very straightenable should it move.

Last, but not least, when bought in large round stock it is cheap! I currently work with L6, O1, 1084 and 1095 and L6 is the least expensive of the lot. Of course I do have the power hammers to work it down from the large rounds and those who by it in flat stock can plan on paying more.

whv
05-23-2003, 06:40 PM
thanx for jumping in, kevin. i also notice that the cover of the july blade has an l6 sword that has been through the mill with little sign of use. really tough stuff.

Terry_Dodson
05-23-2003, 06:54 PM
any chance of seeing that picture here? i like swords, and i really like pictures :D so L6 is really good for swords? whow do you heat treat something like that?

Danbo
05-27-2003, 11:16 AM
Ok Kevin, you sold me on the L6. Now, when can I get my L6 camp knife? ;) :D

T. Hendrickson
05-27-2003, 11:25 AM
Yeah I saw that sword-read that article, too. Anybody know anything about this bainite ?
So-could I take all this to mean l6 can be air hardened? Perhaps it won't be quite as hard, or..

Kevin R. Cashen
05-27-2003, 12:49 PM
L6 will air harden but it is not meant for that medium, you will get more consistant results in oil.

Bainite has been around as long as steel, but was not understood and really recognized until the first half of the 20th century when Edgar Bain (note the name), while developing I-T curves by quenching at different temps and rates, found that a different structure would precipitate when quenched steel was held in the area below where pearlite forms (below 900-1000F.) and above the temperature at which martensite would form, a range between 800F. and 450F. This microstructure had an odd feathery look when formed at high temp. (upper bainite) and a more martensite like acicular look at lower temps (lower bainite). One thing was notice right away however, the stuff was very resilient and incredibly tough.

The high temperature transformations, like pearlite and austenite form through diffusional processes (carbon moving about and equalizing) and the low temp martensite is a shear dependant (not reliant upon carbon movement but, quite the opposite, the trapping of carbon and the shearing shift of the austenite. more complicated than what I need to get here). Bainite seems to have some qualities of both so I have always sort of thought of it as the bastard love child of pearlite and martensite ;)

If shock resistance is a higher priority than edge holding (like some swords) then bainite is pretty good, but for all around cutting knives martensite is still the tops. My study and experience has shown me that prperly marquenched martensite will provide more shock resistance that most mere mortals require as well as excellent edge retention.

One drawback of bainite is the difficulty in properly making it. You have to be able to miss the pearlite nose, with either fast quench mediums or deep hardening steels. The faster quench will result in martensite before you can make any bainite. Even with the deep hardeing steels you will need to stop the quench in the bainite range and hold it there long enough to form bainite. This can be many minutes to many hours, depending on where you hold. Any non tansformed austenite will turn into martensite upon cooling so if you don't get it all to bainite you will have martensite embrittlement that will have to be dealt with.

The bainite is cool stuff but, like every other fad that was going to revolutionize the knife world, it is highly over rated. It is also nothing new since Bain was working with it around or before WWII.

fitzo
05-27-2003, 01:11 PM
For anyone who is interested in the technical end of this, keep your eyes open for a copy of Bain's book "Alloying Elements in Steel". It is a technical book, and a difficult read, but it is packed with so much useful info for those trying to understand this process of heat treat for all steels.

No longer in print, you'll have to search through used bookstores for a copy. If you live near a university town with a good Materials Science department, there is probably a copy in the university library. For the not-faint-of-heart, if you really, really want a copy, you can order a fresh reprint from www.AstroLogos.org

Be prepared to hold onto your shorts, cuz the reprint cost is staggering. Nonetheless, though, what an awesome tome on the chemistry/metallurgy of heat treat.

Very interesting thread. Thanks so much for chiming in, Kevin, it is great to read some good tech info here. Science-boy in me loves that! :D

Jan Dox
05-28-2003, 11:21 AM
Reading Kevin's notes I get to believe the blades from worn diamond concrete cutting saws (24 to 40" and about 3/16th thick)are not L6, because after the "standard bladesmith anneal" I can drill and file them ( it is hard on HSS drills). I edge quench in oliveoil and this gives a hard edge and softer back with reasonable "hardening line".(Also distinct difference in grain stucture between the two areas visible at the break surface of a testblade)
The manufacturer wouldn't give me the type of the steel when I asked. So we're still not sure what this alloy is.

Jan

Kevin R. Cashen
05-28-2003, 12:19 PM
If your steel has some of the other qualities of L6 but heat treats in the manner you describe, a possibility is 15n20.

Gary Riner
05-28-2003, 12:46 PM
I have a friend in the Concrete cutting business and he gives my all the worn out "cores" that i want. I asked him to contact his supplier for the alloy. They will tell him anything he wants to know due to the high dollar amount he spends with them. He talked to the supplier of the cores and was told that the ones he gets are 4135.

It will harden better than you would think from the low carbon content about .35% and is relativey tough.
Hope this helps.
Be blessed
Gary
..................................http://fibermascus.com/logo50.jpg

whv
05-28-2003, 08:52 PM
jan - fwiw:
from the bit of research i have done, i believe that most specialized saw blades depend upon the tooth tip material to do the cutting (diamond, carbide, etc.), rather than the core. as gary mentioned, the core can be (and usually is) some steel rather poor for making knives.
.
the blades that have no special tips, ie the teeth are the same material as the blade/core, are the ones more likely to be of l6, 8670 and the like, which will make for a good knife blade.

T. Hendrickson
05-29-2003, 11:43 AM
very interesting

canyonman
05-30-2003, 08:32 PM
I recently called the maker of our blades, for the metal band saw at work. It looked to my eye as if the teeth and body of the blade were the same material. Lo and behold he told me the teeth were M2 and the body was a plain carbon, but he didn't know what it was for sure. All he could do was tell me to harden some and see what I thought. Not exactly what I wanted to hear but in the final analisys he's right.

Jan Dox
05-31-2003, 04:19 AM
The cutting parts on concrete cutting saws and hollow coring drills are blocks of a metal alloy filled with industial diamonds.
The system works as follows; It's the hard diamonds that grind the concrete or stone away, during that grinding they get dull and at the same time the bearing alloy (matrix) wears too. The ideal combination for a certain type of stone or concrete is that while the diamond particles dull, the dust of the ground stone wears the matrix so that the dull diamonds are not supported anymore and fall off and fresh diamonds appear at the surface to take over the work at the same time. The manufacturers could go very far in tuning the cutting segments to a certain concrete in varying the hardness of the matrix and the amount and size and quality of the diamond particles.
I work for Hilti, a multinational, specialised in tools and anchors for the building trade and sell these saws and drills myself, but the head office keeps the details to themselves, I couldn't get the "industrial secrets" like alloys of the sawblades from them.
I have the alloys for the bits for the electro-pneumatic combi hammers and breakers at work ,because who needs them for reshaping and HT gets that info without problems.

Jan

Jan Dox
06-07-2003, 07:31 AM
Thanks Kevin,

The 15N20 is indeed the most likely alloy, without the Chrome, Molibdenum and Vanadium (all between 0.25 and 0.4%), it hasn't those airhardening characteristics and a bit less wear resistance, but gives me good steel for longer working blades.

Jan

Mike Sader
06-07-2003, 11:12 PM
Jan, any chance you would or could tell a fella what those bits are made of? I have about 6 that got broken in use and was thinking about trying Genos' idea of wrapping some cable around them and forging them out if the steel is any good. Thanks, Mike

Jan Dox
06-10-2003, 02:18 PM
Hi Mike,

We have 5 groups of breaker bits for which I have 3 alloys and the specifications for reforging the working end and the tempering instructions:Illustrations can be found on
www.hilti.com
I couln'd find the exact American description nor the detailed alloy,
but the first number is the carbon content and then the other alloying elements with a number that gives their combined % according to a specific formula.

The current generation TE-Y and first generationTE-S bits:
The TE-y have a round shaft of 18mm (about3/4") with SDSmax connection and towards the point they become diameter 16mm.
Where they get thinner you notrice a friction weld where the front part is connected to the rear.
The TE-S bits have an hexagonal rear (22mm across the flats)and a round front end connected by a similar friction weld .
The working end is an air-hardening tool steel: X50CrMo51 (1001287)
Forging at 1000-1100?c and final temp. for heat treat 1050-1150?C (Bright orange-yellow) and cooling in air, on a rack separated from each other , no other treatment is nessessary for a hardness of about 57HRC

The older generation with hexagonal shaft (all the way) are TP 19 or TP22 bits (size in mm across the flats roughly 3/4 and7/8")
They are made of C70W2 , a waterhardening (10-20%salt) steel.
Forging temp 800-1000?C (orange-red to bright orange)
Hardening 800?C (bright red) tempering in oven at 260?C 60min.
or with residual heat on colour red-brown (before red-violet!wich is 270?C)for hardness of 55+-3 HRC

The older generation 3/4" round shafts with SDS connection are made of 45SiCrV6, an oil-hardening steel.
Forging at 850-1050?C (bright-red to red-orange).
Quench at 850-880?C (bright red) and temper in oven for 60min.
at 320?c or by colour reddish-brown.

The latest generation TE-SP bits (hexagonal 22mm) has a special shape and is induction hardened and through the shape they wear back but stay pointed and don't need resharpening or reforging. They were introduced in Belgium by the end of march this year.
The smaller chisels with TE-C and TE-T (10 and14mm) connections
are oilhardening "verg?tungsstahl" and are forged at 900-1000?C
(bright red to bright-yellowred) and quenched in oil, no HT or tempering is nessessary (for chisels of course).

Jan

shgeo
06-18-2003, 10:32 PM
I have a friend who gave me some worn lapidary diamond blades to try out for knife blades. I've been researching (Google) online with manufacturers and most of what I have found are either L6 or 1050.
I haven't been able to get specific info on these saw blades, but shouldn't have much trouble telling the difference when I try a heat treat on the first knife blade.

Jan Dox
06-25-2003, 02:15 PM
Mike,

when reading your reply again I gess You meant the blocks of metal with the diamonds in it:
Their alloy can vary completely from type to type and brand to brand. We had a series that were a copper/Titanium (CuTi) alloy.
They are made by sintering blocks filled with a mixture of powdered metals and diamonds under high temperature and pressure.

Jan

Mike Routen
06-27-2003, 03:50 PM
I just ran across this thread and have a question.

Recently I purchased a bar of L6 and have started forging some small hunters out of it. What would be the best way to anneal them before I start filing/grinding them? I do not have any special ovens or heat treat equipment, just a gas forge and a bucket of vermiculite.

Any help would be greatly appreciated!

Thanks,

- Mike

Kevin R. Cashen
06-27-2003, 04:33 PM
Originally posted by PropellerHead
I just ran across this thread and have a question.

Recently I purchased a bar of L6 and have started forging some small hunters out of it. What would be the best way to anneal them before I start filing/grinding them? I do not have any special ovens or heat treat equipment, just a gas forge and a bucket of vermiculite.

Any help would be greatly appreciated!

Thanks,

- Mike

forget the vermiculite stuffing hot L6 into vermiculite will get you similar results to stuffing it into water (only without the cracking). Without tight temperature controls your best bet is to heat it to non magnetic and then let it air cool all the way to cold then reheat it to dull red several times. If in this process you should go over into the nonmagnetic range again you will be back to square one.

I used to have patchy results with stuffing it into a gas forge that has cooled below 1400F and then pakcing ceramic wool in the doors. this would work with a thicker refractory lined forge but a cerawool liner would probably cool too quickly.

Mike Routen
06-27-2003, 04:37 PM
Kevin,

Thanks for the info! I never would have guessed on going to critical temp, cooling completely then going to dull red. Does this basically just normalize the steel, or does it really help soften it up a little?

When I go to dull red, how far should I let it cool before going to dull red again?

Thanks!

- Mike

Kevin R. Cashen
06-27-2003, 05:28 PM
Going to dull red will pull the carbon out of play and this is easier to do with finely dispersed microcontituents such as martensite. So by going to critical you will form austentite that, in L6, upon cooling will transform into martensite. Then by going to dull red, below critical, you will not form austenite but you will diffuse the carbon and you will need to do this a few times to get it done good. you do not have to wait for it to cool all the way in between the duller heats but you can see how if you were to go to high and form austenite you will start all over again.

Mike Routen
06-27-2003, 06:12 PM
Kevin,

That make a lot of sense. Thanks again, you probably saved me a ton of effort and frustration on my first commissioned work!

- Mike :)

Will
07-04-2003, 01:00 AM
So far the only way I've gotten a good aneal is to pre-heat two pieces of 1/4 thick scrap steel slightly bigger than the blade and heat the blade to just below non-magnetic. Put the blade between the pre-heated bars and cover in a bucket of wood ash. This methoud takes about six hours to cool to where I can handle the blade. I do this three times and the blade comes out uniformily soft. It took a while to figure out, but L-6 realy likes to air harden.

Hope this helps,

William

Kevin Hagan
07-27-2003, 05:45 PM
Thanks! I have been asking that question in the newbies arena and haven't gotten anywhere with it. Folks told me to treat it just like carbon steel. Thanks again! Oh, this stuff makes great tomahawks too, buy the way!

Greg Covington
08-24-2003, 03:00 PM
Here is a pic of a knife that I just made from L6. 6" blade forged, full tang, stainless guard and a parkerized finish. I heavily tested this blade before finishing it. It chopped thru a 2X4 a couple times as well as some old rock maple, and did not degrade the edge. I tempered it twice at 380F.

Interesting thing is that you can really see the grain structure on L6 showing thru the parkerizing.

http://www.covingtonknives.com/images/brom.jpg

Dragon cutlery
08-24-2003, 05:22 PM
you can treat admiral steels L6 like plane carbon but the stuff cashen calls L6 you better treat it just like he says or youl be looking at one hell of a hard blade that you thought would be soft :( i thought i was working L6 till i talked with cashen and he told me it would air harden :confused: now im just trying to find out what the hell i have been using for the last 5 years :(

Daniel J
08-25-2003, 02:20 AM
Greg, what is parkerization? That blade looks good enough to eat! :D

Greg Covington
08-25-2003, 03:10 AM
Parkerizing is a phosphate coating that is very rust resistant and has been used on military weapons and knives for years. I sandblast the blades first then use Amerlene from Brownell's.