do a low temp anneal, at a guess you are getting carbides. For best results harden first then soak at 1150-1200 for half hour or so. most of the time i just normalize and then toss it in the kiln at 1200 for 15-20. that normal works fine.

MP

Thanks Matt, when I first read your response I was saying "huh? what?" and then I remembered Kevin talking about carbide sheets and such laughing at your drills and saws here: http://www.americanbladesmith.com/ipboard/index.php?/topic/2429-tang-to-hard/page__p__17074__hl__Tang,

That was the "DOH" moment. I just hardened that bar out of 1485 and it's back in the oven at 1200 for 30 minutes.

Your very slow ramp up, time at solution, and very slow ramp down made some pretty nasty things in that steel. You probably have carbide networks in the grain boundaries, so you will want to take you time forging and do it a little warmer. Matt's suggestion for a fine spheroidal anneal is good for your final product but at this phase, and considering that you will be cutting it, an industrial spheroidizing would be a good idea, especially since you have the ramp capability to do it.

Normalize the bar to break up the networks you have, and then heat it (no ramp, just heat it) to 1375F for 1 hour and then ramp down no faster than 50F per hour to below 800F-850F. This is what I do when I need to mill, cut or otherwise machine my steel and want my tools to be fine with it. You will have coarse spheroidal carbides but it will cut like butter.

Thanks Kevin.

I guess it goes back in the oven....again.

Do you have to use an oven to normalize if you make your own damascus. I planned to use my forge to normalize. I have a billet welded up of 1095 and 15n20. Any feedback for what I should use here would be helpful. Sorry if I am hijacking the thread.

Scott

Not at all a hijack Scott, the discussion is welcome. I'll get to your question in a moment, first I have something to tell Kevin.

Kevin, I actually missed it. I missed the techno-talk and scientific explanation. I was hoping you'd chime in and help me out, and I am very grateful for the advice and direction, but I found myself asking the question "Why did this happen?" I know I've chided you in the past for getting all "egghead" (as you would put it), but I really want to know the "what happened and why" of this. It's great to know what to do to fix it, but that is just information without understanding. So, if you have the time and inclination, I'd appreciate the science behind what happened. Thanks.

Now for Scott's question. First off, I'd like to stress the fact that a controlled oven is not necessary for any of this. Humans have been making steel tools for millennia without any of these technological contraptions. The difference between them and us is basically the amount of time we have to devote to our tools and learning the intricacies of fire management. If you were a smith in 1100 C.E., you would have had a whole lifetime devoted to this craft, day in and day out, from your childhood to whatever age you are now. You would have appretenticed under an experienced smith starting at around age 7 and smithing would have been what your whole life was about. The forges, presses, ovens, etc. just make our job a whole lot easier to do and learn. OK, so that smith from 1100 C.E. didn't have the steel we have today, but that's not a deal breaker. It just means that to use "archaic" methods, you'd have to be a lot more careful and deliberate.

Normalization is just one part of the heat treating regimen, a first step as it were. I think most of us normalize in our forge (I do anyway) because it is fast and effective. Annealing is a different process that takes more heat control and time than a simple normalization. Before I had the oven, I built an annealing box for my steel. It was a steel box (leftover from a power tool) with a Koawool blanket and a bunch of silica sand.

I'd bury the hot steel in that and let it cool down. It took quite a few hours and produced a fairly soft and workable consistency.

Thanks Joshua. Looks like i have to build an annealing box.

Scott

|quoted:

Not at all a hijack Scott, the discussion is welcome. I'll get to your question in a moment, first I have something to tell Kevin.

Kevin, I actually missed it. I missed the techno-talk and scientific explanation. I was hoping you'd chime in and help me out, ...

Well, you asked for it <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//biggrin.gi f' class='bbc_emoticon' alt=':D' /> ...

When you put steel into austenitic solution, i.e. the carbide is dissolved and the resulting free carbon is in in even solid solution in the iron, it will only want to stay that way at the elevated temperatures that provide the necessary equilibrium. Upon cooling the carbon will separate out of solution and concentrate until it begins to form iron carbide. This iron carbide will take the form of lamellae (networks of thin ribbon like formations of alternating ferrite and carbide). This process is diffusion based so that time plays a huge factor; the more time the carbon has, the more distance it can cover.

Simply air cooling from solution results in very fine pearlite with the carbide and spacing very fine, but the slower the cooling the coarser the spacing and the carbide ribbons. In steel with .8% carbon or less this is not a big deal because there is not enough carbon to make much more that thin pearlite (the lamellae based phase), but with steel in excess of .8% carbon extra carbide is produced until the pearlitic equilibrium point of .8% is achieved and then the remainder of the carbon goes into the pearlite. The slower the cooling the more of this excess carbide (known as pro-eutectoid carbide) is produced and gathered in inconvenient places. Eventually, with enough time, it will gather in the grain boundaries where it will stabilize and cause embrittlement, ornery machining and a few other aggravations.

This is why you should never use a full (lamellar) anneal in steel with more than .85% carbon. The problem is that bladesmiths love one size fits all heat treatments, which modern steels did away with; the heat to non-magnetic and into vermiculate or wood ash trick should only be used on steels with less than .8% carbon. I must beg to disagree with the idea that ancient smiths could have worked things out with modern alloys given enough time with the tools that they had. I have a saying I use often – “alloying changed everything.” I have often been challenged with the an appeal to tradition/authority argument that ancient smiths did just fine without all these fancy tools and technical jargon, the problem is that the ancients didn’t work with the same materials. Modern alloys evolved with the technology and industry of the times, and so they are tightly linked. More controlled ovens were not just a convenience, they began to appear, out of necessity, about the same time intentional alloying hit its stride. I, too, had no idea what a difference there was between ancient steel and modern alloys, until I began making my own bloomery steel, then the contrast was shockingly stark. Think about it, intentionally add just a pinch of chromium (say just half of one percent) to the tatara smelt and suddenly Masamune would no longer be able to produce hamon on his blades, the temps would all be off by at least 75F and a simple forge would be insufficient to dissolve the Cr carbide carefully, welding would be miserable, forging stiffer, polishing quite different, and the resulting blades would be worthlessly brittle without a much more controlled system of tempering. Expecting a smith to work on a modern alloy with ancient tools and technology is more extreme than expecting a Model T mechanic to work on a 2016 Ford car. Even with a lifetime to figure it out, without a working knowledge of fuel injection systems and computer diagnostic tools to tune and program, even early 20th century technology is left frustrated. The problem is that smiths manage to make a blade that cuts from a richer alloy and believe they have mastered it, but with the proper equipment, industry brings out properties exponentially greater in that alloy by tapping its true potential.

Now all that being said, there is no reason for Scott to lose heart, there are some operations that you can do fine with a forge, even with slightly richer alloys. Normalizing is one of them. Normalizing is more about the rate of heating and cooling than the exact temperatures. It is more about dissolving everything into solution evenly and then cooling in a manner that produces even and well distributed structures/phases. I have all my fancy gadgets about 8 feet from my forge and still use my forge about 75% of the time for normalizing my damascus. All you need to do is heat well above non-magnetic and evenly air cool. This is well within the forges capabilities. Ramping for isothermal anneals and proper soaks for hardening are better left to the controlled oven but the forge can still do many things. And also remember that if you wish to do more with a forge like they did in the old days, then you simply follow the evolutionary path backwards in your steel choice. The simpler the alloy, the simper the tools needed. 1075, 1084, 1095, W-1, W-2 are alloys left over from our initial steps from ancient steels to modern alloys, so they can be worked quite successfully in a traditional smithy.

Back to the original topic. Joshua, your machining setbacks can be summed up in one word- 1095. It is the simplicity of 1095 that makes its extra .15% carbon so annoying. With no carbide formers (Cr, V etc..) to distract that carbon it forms very obnoxious pro-eutectoid carbide networks rather readily. I think I have dulled more drill bits on 1095 than any other alloy.

To tame it, you approach things from the opposite direction. Keep the annealing temp below critical, (or at least well below the upper critical AcCm). By doing so you have a more slow and controlled diffusion that tends to gather the carbide up into spheroids, rather than lamellae. This eliminates the carbide networks and makes things easier to machine.

Thank you Kevin, that was exactly what I was looking for. It explained very clearly what the problem was. In a nutshell, you can't treat 1095 the same as 1080, which up until yesterday, was my M.O.

I never experienced the types of troubles with my 1080/15N20 Damascus billets and I was confused to say the least.

BTW, you don't have to beg to disagree with me, just do it straight up! I have to clarify that I was answering Scott's question from the specifics of 1095/15N20 pattern welding. I was not intimating that it would work with any of those more complex alloys. However, taking your explanation into consideration, he may find the annealing difficult with the method I suggested. It does work well with 1080/15N20 and I have had good luck with O-1 and the simple annealing box before. Maybe that was dumb luck, but my understanding is that the pre-industrial revolution smiths worked steels with higher carbon contents than .8% and did so without benefit of controlled temps, atmospheres and such. True, the alloying and adding of elements like chromium, vanadium, tungsten, etc. change the qualities and require working processes outside of the basic smithy, but I don't think that a high carbon content alone is a game changer. Am I incorrect?

Thank you Kevin! I actually understand that. <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//blink.gi f' class='bbc_emoticon' alt=':blink:' />

Brion

|quoted:

Thank you Kevin! I actually understand that. <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//blink.gi f' class='bbc_emoticon' alt=':blink:' />

Brion

Yeah, it's like the more we hang out with him, the more sense he seems to make!

The annealing box would work for the 1080/15n20 as it would have in the range of .75%-.80% carbon overall, but you may indeed have been lucky with the O-1. O-1 responds very nicely to spheroidizing and if you liked it lamellar annealed you will love it spheroidized.

Eventually, after good blast furnace methodology was perfected, you did begin to see more consistent results in higher carbon materials, but much of bladesmithing history runs the gamut with carbon contents (sometimes even in the same blade <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//wink.gi f' class='bbc_emoticon' alt=';)' /> ) with much more at the lower end of the scale. There were indeed some exceptions, like crucible steels, but they were still handled with the knowledge and technology of the times, with the most common approach being to not harden the stuff you didn’t want brittle. We obviously have many more options than this today, and it is why differential hardening is really more an aesthetic thing with modern alloys which have much better toughness properties than their predecessors.

Just as with 1095 and W2 our ancestors no doubt found, through trial and error, that there were things you shouldn’t do with higher carbon steel, and adjusted their methods accordingly. We can do the same with 1095, W-1 or W-2 with just our forge, although we don’t have to spend half a life time figuring it out, somebody already did that for us <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//biggrin.gi f' class='bbc_emoticon' alt=':D' /> .

It is interesting how this all sort of ties together with your request for more in-depth information. In the ancient world the master told the apprentice “do this”, and the apprentice never dared ask “Why”, making the line of knowledge thin and tenuous based upon ritual like adherence to methodology. But when we fully explore the “why” factor we gain an understanding of the process that frees us from the ritualistic recipes and allows us to advance, expand and improve at a much greater rate, and adapt to the unexpected. This is why I do not give out “recipes” as I see them as chains binding the user to one limited approach. And this is why I am always happy to expand and explain the “why”, because it is the ultimate path to freedom. Knowledge is indeed power and your most valuable tool; salt baths, ovens, or even forges are useless without it.

Thanks for all this Kevin and Joshua. This is very helpful. Could I just anneal the billet of 1095/15N20 by heating well over non-magnetic and turning the GAS forge off and allowing it to cool slowly? Or is it better to air cool more quickly.

The faster cooling is the "Normalization" process, and you should do this at some point during the whole process.

Slower cooling is the "Annealing" process, and whether you do this or not largely depends on what your scope of work is going to be.

So tell us what you plan to do with this billet, and we can point you in the right direction.

What stage of billet development is it at right now? (# of layers, is it a flat laminate, twist, etc.)

What other manipulations (if any) are you planning? (what is the final intended pattern)

What is the final purpose? (is this for blade steel, fittings, or something else?)