5 hour soak with O1

[Phillip Patton]

Heat your L6 to 1500-1520F and soak for perhaps 10 minutes and you should find things back to where you want them.

I'll try this tomorrow and see how it goes. Unfortunately, there's a big chunk missing from the edge, so even if I get the heat treat right the shape of the blade won't look right after reprofiling.

 

[Kevin R. Cashen]

...I have become convinced after HT'ing many, many blades that with proper temperature control and a choice of Austenitizing temperatures at or slightly below the mid-range specified for a given steel, that under-soaking will result in more degradation to knife performance than over-soaking.

Although, it may have looked like I was saying something different in conversations we have had on another forum, much of what I have seen under the microscope, has me saying that I must concurr with you R.J.

 

[Kevin R. Cashen]

Side note: This thread has proven to me that while I have have quality results through testing and use, my setup leaves so much to be desired. As a science dork at heart, I have taken this thread very seriously. Can anyone get a forced air forge to regulate at the exact temp suitable to soak for 20 minutes? I know I cant.....and that says something.....with tax refunds coming back, that oven is looking awful tempting.....

Great thread guys, a real eye opener!

TicTock, one thing to be aware of is that the performance of the resulting knife can be relative to the application . While a blade heat treated the way we are describing would chop 2X4's and cut rope like crazy, it would fail the bend test totally unless you went through some extra effort to soften the spine enough. So for an ABS test knife these methods are not what I would recommend.

I mention this only because there are so many different strokes for different folks out there that I would hate to have anybody think that I am saying everybody has to have an oven or a salt bath, for some folks forges are just fine.

I just can't let the notion slide that there is no difference between the heat treats that these different tools provide, as you have discovered the differences can be huge. Without making any blanket quality judgements, I am just pointing out that there are differences.

 

[mete]

TikTock, are you putting our blade inside a pipe it the forge ? That evens out the heat quite a bit .....Kevin, RJ, the soaking discussion reminds me of a sample of tool steel that had a problem . I prepared the sample a number of times and saw that it wasn't right. A very subtle thing which I saw but no one else could. But I worked with that steel on an every day basis while no one else did . My conclusion was -not enough soak ! There seems to be so much worrying about grain growth which is far more a problem of temperature rather than time .So concentrate on proper temperature and don't concentrate on 'minimum' soak....I agree with RJ when he says that you can't simply translate size to time going from 1" times to 1/8" times.

 

[David Schott]

Yes I put them in a forge, but I have never had a thermocouple to test beyond careful magnet usage along longer blades....

Ive never had problems, just have always wanted precision andsome ability to do stainless, so maybe i'll sell a few knives ive been sitting on and bite the bullet.

 

[Dan Gray]

P.S. I know it is just a matter of time before somebody starts splitting hairs with the less than precise terms I am using here. Sometimes you just want to discuss this stuff with folks who aren't total nerds, and you have to resort to plain English, but it can become very frustrating when one crowd picks at you for the techno-babble, while the other is waiting to pounce as soon as you misspell "arret refroidissement". It is one of the reasons knowledgable folks refrain from sticking their necks out for these talks, I can only hope that folks will cut me some slack here.

Kevin
not knowing for sure but I dare say most of who reads these posts would rather see this stuff written in layman terms rather than in nerd terms any day, at least until they understand them that's me for one I dare say

would you put together,
your recommended times, heats, and recommended quench mediums for a few normally used steels?
for the masses,
say using a temp controlled oven or controlled forge..
I'd like to post this for a reference if you would?

this stuff gets said so many times and it's spread all over,and with manufactures specs printed for tool use they are ball park but not tailored to blade makers thin edges..a reference
put in a few places to reference at later dates would be nice, if not to just save you time spelling it out over and over again....
unless you really enjoy it.. thank you

 

[Kevin R. Cashen]

I could do that, but it has already been done and I would only be repeating what is in the ASM "Heat Treater's Guide", or on any of the spec sheets for steel, one can go to Crucible's web site, Carpenters web site or a few others to get this information and more. I would love to say that I could give you all of Kevin Cashen's secret recipes to make super performing steel but that would be a joke. Bladesmiths are the best folks I have ever seen at reinventing the wheel, I have done it many times myself. Struggle with heat treating methods, testing like crazy and then heat treat again, all while ignoring the fact that it has all already been figured out for us.

That is not to say that there aren't some quirks for making knives from specific steels, there are a few steels that I have worked exclusivley with for a while and have learned their quirks. Other steels may have some behaviors that would be best addressed by somebody who has worked them exclusively for some time. Where you get into trouble is when a method is held up as definitive coming from folks who may be blindly stabbing in the dark at the best method, and one day after doing the hokey pokey get a knife that cuts better than the one they did last month, and then scream "eureka", without ever considering how lousy that older blade was as opposed to considering the newer one the "Holy Grail". I remember doing this myself after I got the salt baths. Suddenly I thought I had the magic bullet, I could make the "super knife", none of my previous blades worked this well. I just couldn't bring myself to admit that my previous blades could have been that lousy and I had finally managed to shoot par. After all, salt baths are very old technology (practaiclly obsolete) for every field but custom knifemaking.

I would be happy to share how I would treat O1 or L6 or even 1095 or 1084, but there are variables among knifemakers that make one rigid formula hard to follow, which I was going to cover in my next post...

 

[Kevin R. Cashen]

For those of you who are new to some of these concepts, I thought it best to chew on some of the discussion a bit before complicating things with the next point that occurred to me. Neccesarry soak times are greatly effected by the condition inside the steel before heating, and these conditions vary greatly with forged blades in particular. Bladesmiths, unlike grinders, love to take the very nice annealed condition that the steel arrives in and just jumble it all up.

Some microstructures take longer than others to get into solution. It has to do with how much the carbon has to travel to disperse and evenly distribute. Spheroidal conditions take about the longest, because the carbon is balled up in big globs spaced far apart, fortunately this is the most common condition that our steels some in from the supplier and they account for this in the heat treating recommendations.

Let me once again explain the spheroidal anneal. For this the steel his heated to a temp that is below, at, or just barely above Ac1 and the carbon is allowed to seperate at this low temperature into little spheroidal carbides. Here:

the little white/silver globs are left over spheroidal carbides in a hardened piece of my 1095. I don't have an image of totally spheroidized steel that I made but it would have the entire field covered with those little round globs. This is one of my favorite images, because I was albe to use the natural colors with my camera to get wonderful contrasts that I haven't even seen in many textbooks.

Anyhow, since the spheroidal anneal is subcritical, it does not mess with grain size at all, this is why I prefer to do all of my grain refinenment and normalizing right after forging and then make it all completely stress* free with this anneal. It is also the best for machining steels that can form carbides because little balls in soft ferrite offer little resistance to cutting. Spheroidized steel is about as soft as a high carbon steel can get.

I will cover the next condition in the next post or this post will get too large.

*Edited to note: that indeed stress and strain are not interchangeable but I think folks get the idea just fine using plain English .

 

[Dan Gray]

I could do that, but it has already been done and I would only be repeating what is in the ASM "Heat Treater's Guide", or on any of the spec sheets for steel, one can go to Crucible's web site, Carpenters web site or a few others to get this information and more. ..

that's the point
to much info for the new guy
and I'm not sure they could compare say Texaco A with B
or parks AAA with brine or even know where to start other than here on the forums, it's here but not for long and it will have to be looked up again (if they can) or asked all over again. definitive wouldn't be the word or point,, a base for a good start to monkey with how many times have we been asked "what do I quench my steel in?" once they know what ... quench means some of us are on the other end of starting out..and take things for granted that new guys struggle with,
that was the point with layman terms also.
just a thought that may not have been a good one..

as you can see you post a lot faster than I can too it is a great thread BTW

 

[Kevin R. Cashen]

The next longest to dissolve would be coarse pearlite. This is what perhaps 40% of bladesmiths would have in their blades if they do not use ovens to anneal. Pearlite comes in a wide range from coarse to very fine, the courser it is, the softer the steel will be. It dissolves a little quicker than spheroidal carbides, because it is made up of alternating lammelae (layers) of cementite (iron carbide) and ferrite, so that the carbon is fairly evenly distributed thoughout to begin with. Here is one of my images of pearlite, not a good one but it gives you an idea:

The cooling was off a bit so I only got partial colonies growing from the grain boundaries but you can see the striations in them caused by the lamellae.

To make this stuff, you heat to well above critical and then cool very slowy through the critical range, the slower you cool, the more carbon seperation, and the coarser the pearlite. Many bladesmiths heat to above "critical" and then insulate the blade in wood ash or vermiculite.

Because it is a euetectoid steel, 1084 is a pearlite making machine, and will convert to almost entirely fine pearlite if heated to critical and allowed to air cool. Finer pearlite will be increasingly harder until it can even mimic hardened steel to the untrained oberver or less than accurate means of testing.

The finer the pearlite, the quicker it will go back into solution. Most cooling rates for anneals that I have seen bladesmiths use would produce less than the coarsest pearlite, to the finer side. Since pearlite puts the carbide in films or sheets it is tougher to cut an machine than the spheroidal stuff. In 1095 course pearlite surrounded by loads of pro-eutectoid iron carbide will squeek and burn up drill bits just like fully hardened steel, Except it will let you get halfway through the piece before doing it:grumpy:

 

[Kevin R. Cashen]

The quickest condition to get into solution would be one that was already there. Martensite is a room temperture saturated solution of iron and carbon, so the only soak time neccesarry would be to dissolve any carbides formed on the way up to austenization temp, so obviously this would be highly effected by rate of heating. Something like salts or induction heating would be a snap, slow and incremental heats, like in a forge would take some carbide out of solution and need a little time to put it back, once over the hump.

 

[Kevin R. Cashen]

Dan

As I said I would be happy to share what works best for me with my equipment and oils, but it is pretty boring stuff. One thing that is quite noticeable from reading the posts from different guys with different tools is that things get very standardized once you get tight control over the temperatures; suddenly all you need are the spec sheets. The guys that need to get creative don't have the tools that the spec sheets assume you have. With torches, forges, water, brine, olive oil etc.., there are indeed infinite ways to achieve the desired results, and there are many shades of gray. But when you can hold at 2 degrees above critical or 2 degrees below all day with a press of a button, the field narrows to just a few methods because things start to get pretty black and white. Perhaps this is why I believe the high teck stuff will never win the popularity contest with the impovised folksy stuff- black and white is boring.

 

[Kevin R. Cashen]

One point that I also wanted to make about soaking was that for some folks total solution is boring and not what they shoot for. Martensite will begin to level off in hardness from carbon saturation at around .6% and will reach that maximum at .8%. Some folks think is is cool to push it far enough to get a percentage in this range into solution and then put the rest into super hard carbides scattered throughout that hardened matrix. But needless to say it takes planning and very tight control to do it.

 

[Dan Gray]

Dan

As I said I would be happy to share what works best for me with my equipment and oils, but it is pretty boring stuff. One thing that is quite noticeable from reading the posts from different guys with different tools is that things get very standardized once you get tight control over the temperatures; suddenly all you need are the spec sheets. The guys that need to get creative don't have the tools that the spec sheets assume you have. With torches, forges, water, brine, olive oil etc.., there are indeed infinite ways to achieve the desired results, and there are many shades of gray. But when you can hold at 2 degrees above critical or 2 degrees below all day with a press of a button, the field narrows to just a few methods because things start to get pretty black and white. Perhaps this is why I believe the high teck stuff will never win the popularity contest with the impovised folksy stuff- black and white is boring.

hence we are blessed with more of the improvised folksy stuff by necessity
be it money or just the want to get the feet wet, ahh to be called a knife maker, it has a ring to it..and it beckons many
that damn Bug

edited to add
I'll get my junk off from here soon to keep this thread from getting messed up.. it's a good one..

 

[Jesse Frank]

:thumbup: This is a kick butt thread!:thumbup:

I myself noticed a large jump in performance when I started soaking my blades at lower temps for longer times, especially with 1095 or W1.

It's been mentioned in passing, but I just want to point out that if you are doing long soaks, be sure to use either a good antiscale compound or ss foil to stop decarb! It doesn't do a lick of good if all that good carbon get's sucked out of the edge

 

[David Schott]

In some of my early blades, I had a good deal of banding looking effects. I now realize that these may have been not fully dissolved blades where they never went to full solution. Does that look to be the case for this blade? I heard this was alloy banding but it now makes alot of sense to me since I can not soak properly with my current setup (and wasnt even doing soaks, etc back then)

 

[Asis]

First of all, apologies for my dumpish english

As far as I know, alloy carbides are different salts. They do dissolve at higher temperature than Fe carbide. Even weak carbide formers like Cr still need higher temperature to be dissolved.

When you forge or anneal at 1500 F, carbon from Fe carbide start swimming back into solution. But, is that hot enough for alloy carbide? Is it possible to have alloy carbide (re)crystalization? After cycles of heating forging cooling, you may end up with fibrous alloy carbide in high carbon matrix. (let's take 1%C 1.5%Cr for example)

This 's just my idea, corrections will be highly appreciated.

 

[mete]

You should have started a new thread. Carbides are not fibrous. Carbon doesn't swim it diffuses !!... Different alloying elements have different bonding strengths with carbon. The tightest bonds [W,V,Mo] require higher temperatures and longer times. The basic heat treating dissolves carbides to saturate the matrix with carbon so as to produce the strongest and hardest martensite.

 

[Asis]

Ah, yes, many thanks mete. It diffuses, not swims.

Sorry for didn't start a new topic. I just want to discuss on this banding pattern as showed above. (seems to be ignored for a whole year)

And also sorry for putting many improper, misleading terms here. I do understand that metal carbides dissolve like salts. Their solubilities and rates are highly temperature dependent. My point 's that, some other metal carbides require higher temperature to make it dissolve back into solution. What if someone forges his steel around 1500 F? Do weak binder (chromium) carbide crystalized at that temperature? And after numbers of heating/forging cycles, you can have fibrous pattern of carbide banding along the forged direction. And if it not going to happen at 1500 F, is it possible to happen at some lower temperature?

Thank you in advance for answers and corrections.