L6 and Bainite

Steven Roos

Steven Roos

Joined
Jun 29, 2002
Messages
4,131
Does anyone know the specifics on how you have to heat treat L6 to form Bainite structures in the steel?

Also, can you heat treat a damascus with L6 in it and form Bainite in the L6? What sort of results do you get with and L6 and high carbon? (1095 I suppose)
 
Quench from 1450-1550 F to 450-500 F hold at temperature for 6 hours. This is austempering to produce bainite and of course requires salt bath quench. As tough as L6 is with martensite it will be tougher with bainite. The nickel in L6 etches less than 1095 so that combo will produce a nice damascus. But if you mix L6 and 1095 you will have to stick to a normal quench and temper to get the 1095 hardened, it will work fine.
 
So, you couldn't produce Bainite in an L6/1095 damascus? Is there another steel that would harden properly along with the L6 Bainite process?
 
How will the contrast be on such a damascus? How would the function be? How flexible would the O1 be with the L6/Bainite heat treat?
 
1095it.jpg
l6IT.jpg
 
Thanks for the graphs, Kevin. Would you by any chance have an O1 curve you'd share?
 
I would have included and O1 chart but there are so many variations of O1 that it would be a daunting task.

The contrast on an O1/L6 mix is as versitile as one wishes. I can get a striking black/silver or a subtle grey/grey, depending upon how I treat the etch. I am not into sales pitching my own web page on forums but I have many examples of this mix on my site.

So far my testing shows that one losses very little of L6 impact strength by mixing it with O1, even in a 60% O1 mix. This is in an un-notched specimen, notched changes the numbers a bit, but not as bad as one would expect. Of course, all of these results are for a martensitic sample.
 
Kevin, do you by chance have that book called "Atlas of IT's" or something like that? If so, is it worth getting as a study aid to help understand alloy effects? I know it's expensive. Or, alternatively, can you tell us how to dig up TTT and IT curves?

Thank you, for the O1 response and any on this question.
 
Originally posted by Kevin R. Cashen
So far my testing shows that one losses very little of L6 impact strength by mixing it with O1, even in a 60% O1 mix. This is in an un-notched specimen, notched changes the numbers a bit, but not as bad as one would expect. Of course, all of these results are for a martensitic sample.
Click to expand...

What properties does O1 add as opposed to straight L6?
 
Steven the higher carbon content of O1 gives better edge retention. .....Fitzo I have "Tool Steels" by Roberts,Hamaker, andJohnson, very comprehensive but for tool steels only.
 
Kevin, thank you for posting the 1095 chart. Please add your website to your signature.

Every time I see the time/temperature curve for 1095 I have questions. Cooling a blade from critical to 1000 degrees in less than one second is a sporty task. There is almost no margin for error. How many makers keep this in mind when using 1095? How do factories who use 1095 effectively cool large batches of knives to 1000 degrees in less than one second?

Am I reading the chart wrong?
 
Alright, thanks!

Can anyone point me towards a chart on O1? How hard does the O1 get with the Bainite heat treat? Is the combination nice and flexible?
 
hehehe...

mete, not being a metallurgist, I got a copy of "Tool Steel Simplified", of course. :) I have a nice little metallurgy library. I even got a copy of Bain's book, but that one is a bear, even with a chemistry background. I think I need the "Simple" version there, too. Gotta match the literature to the intellectual capabilities....:D

I have to say, though, that I just love trying to understand the scientific principles that try to explain what we do.
 
Originally posted by Chuck Bybee
Kevin, thank you for posting the 1095 chart. Please add your website to your signature.
Click to expand...

Click on this under his name to take you to his website.
 
Originally posted by fitzo
Kevin, do you by chance have that book called "Atlas of IT's" or something like that? If so, is it worth getting as a study aid to help understand alloy effects? I know it's expensive. Or, alternatively, can you tell us how to dig up TTT and IT curves?

Thank you, for the O1 response and any on this question.
Click to expand...

I have the "Atlas of Isothermal Transformation Diagrams" that was put our by US Steel. It is an older copy and didn't really cost me that much. I don't use it as much as I could, althoguh I could see how it could be valuable for general reference.

TTT or IT are invaluable tools for heat treating practices and a wholw lot of heartache can be avoided by learing how to use them. I would suggest the appropriate diagram for the particular steel one is using. I specifically posted the Crucible L6 curve because this is the steel that is being used a lot for the bainite thing and the Carpenter chart looks significantly differnent that this.

A sugary sweet "pretty please" to the steel manufacturer can often yeild information like this.
 
Originally posted by Steven Roos
What properties does O1 add as opposed to straight L6?
Click to expand...

As well as the hihger carbon content that Mete mentioned there are also to alloying features that contribute to abrasion resistance. Many variations of O1 also have vanadium which not only greatly increases wear resistance but alos helps refine grain and keep it that way, which is kind of handy if you are going to be cooking it at the temperatures required to make a damascus blade.
 
Originally posted by Chuck Bybee
Kevin, thank you for posting the 1095 chart. Please add your website to your signature.

Every time I see the time/temperature curve for 1095 I have questions. Cooling a blade from critical to 1000 degrees in less than one second is a sporty task. There is almost no margin for error. How many makers keep this in mind when using 1095? How do factories who use 1095 effectively cool large batches of knives to 1000 degrees in less than one second?

Am I reading the chart wrong?
Click to expand...

From many of my conversations and observations, very few knifemakers keep that in mind, but with this odd emphasis on "bendability" over edge holding that knifemaking has gotten caught up in, it doesn't seem to matter.

It is worth pointing out however, that the edge of a knife can often achieve this cooling rate, while it is the spine and body of the blade that skids through the pearlite nose. Most IT diagrams show around .5 second to get below 1000F, with 1084 at around .75 seconds.

The up side to this is that if one gets the right quench you can form beautiful rolling temper lines down the side of a 1095 blade with a full quench and no messing with clay.

I cannot speak for the factories, but there are quenches that can handle it and the solution that industry usually resorts to is to raise the austenitizing temperature, thus tweeking the grain size up a notch and pushing the pearlite nose to the right a bit to allow for more time. Quench 1095 at ASTM grain size 8 to 10 and you had better be screaming fast in that quench.

Some folks have had results with a lower than normal austenitizing temp, but some of the tests that I have done in this area have raised enough doubts that I am not ready to entirely embrace it yet, instead I am happy I discovered perhaps the fastest oil on the market today in Park Metallurgical's #50.
 
To expand on Kevins point -- This is why I have said in the past that the quench tank should be right next to the furnace. You can't afford to run across the room to the tank. 1095 has sometimes had a bad rep in both commercial and custom knives but heat treated correctly it makes a fine blade. Careful attention must be paid to every detail of the blade making process - austenitizing temp,immediate quench, immediate temper to prevent cracking. Heat treating stresses can be extremely high ,enough to crack steels that have tensile strengths of 300psi or higher.I much prefer a 400 F temper, as is the standard in industry ,because it will produce a very stable martensite , lower temps don't do this......Chuck ,there are some very fast commercial systems , I've worked with vacuum heat treating furnaces where when it's quenching time the bottom of the furnace opens up and the parts fall into the tank.
 
You must log in or register to reply here.
Back
Top