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Tim Mitchell

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Everything posted by Tim Mitchell

  1. AA stands for Atomic Absorbtion and it is a kind Optical Emissions Spectrometry.... Just the old time word for it
  2. Will, you need to test for Carbon which XRF cannot detect. Any carbon determination using XRF is a subtractive amount and is worthless. Basically they use the elemental profile to guess at what your steel is and that can pinpoint your carbon, but yours isn't a standard steel and so they have nothing to compare it with and any carbon figure is a sum of all the errors in the detection of the other elements... worthless. You need to get Spectral AA analysis for all elements or you need to get Leco analysis for carbon, sulphur and then use XRF for Phosphrous, Silicon, vanadium, manganese etc. XRF is still not very accurate so the Spectral analysis is much better. We are talking about very small amounts here. You only need 0.05% Phosphorous for the ingot to develop cold shortness and not much sulfur to get hot shortness. Grey cast iron increases the silicon level in the ingot which can cause formation of graphite in the ingot so white is definitely best...
  3. One other thing, the old method of using long roasting periods for ingots may have been to help remove any remaining sulfur in the steel. They would roast the ingots in Hyderabad for a long time, pull them out, hit one with a hammer and if it broke they would put them back in and roast them again. This was either because their carbon content was too high.... or it was because they were needing to get any remaining sulfur down to a level where their ingots were no longer hot short and could be forged. So if you do have sulfur in the ingot a good long roast will help to get some of it out of your existing ingots.... just a thought.
  4. Will, happy to help. The green glass is fine, it actually has some copper in it to create the colour and so that does help the melt a bit. Al used to use the green glass and it never caused him problems and that is what I use and have never had issues. Concerning heats... High heat is above Acm.... if you know what that is. Low heat is at least 100°C below Acm. So for 1.6% C ingot high heat is 1050 - 1100°C and low heat would be around 800°C. The issue is that if you have lower carbon (1%C) then your Acm point is 820°C and so forging at a mid orange heat is too high... However I think your issue is too much carbon not too little. The problem is that if you are trying to forge above Acm with an unknown ingot carbon percentage, then you will cause problems for yourself. You will have more failures than success. Some ingots in the 1.5% carbon range can only be forged at 800°C or lower or you will crack them... this is because of higher impurities that make them hot short. Giving it a good roast in the gas forge for 1 hour should decarb the outside of the ingot enough for you to do a gentle forging.. But if you forged the ingot at a mid orange heat and had it crumble then you have very few possible explanations. 1) Your carbon content is too high.... waay too high. 2) your sulphur level is too high... 3) you didn't roast it properly.. coupled with sulphur in the ingot 4) you forged too fast and hard. There are a few other less likely possibilities but I think what you are dealing with is one of these, or a combination of these. Calcium is not an alloying ingredient it is a fluxing ingredient, it helps to reduce porosity in the ingot, it removes some phosphrous. Most of the old ingots had some Manganese to help remove Sulfur and it helps with the overall quality of the steel. I wouldn't do the long roast until you know that you are getting consistent and good quality ingots or it will be a waste of time and fuel. It won't make much difference to cracking the ingot or not if sulphur has been your issue. A good 6 hour roast would be helpful though (in iron oxide) and then a decarb in the forge for around an hour. It only takes a small amount of Phosphorous to make your steel cold short especially at higher carbon levels. I would add some calcium to your melt... a large spoonful of crushed shell, in order to reduce that from being a problem. It is easy to have a highish phosphorous bloomery iron. Unless you know your blooms are low in phosphrous (from your charcoal source) I would be adding something to reduce that and to help kill the gasses in the ingot as a matter of course. Cheers, Tim.
  5. Thanks Joshua, I will have to play around with this a bit. I loved the blade in that thread... very nice pattern and the coffee etch really is startling in it's contrast. I also like the comments about normalising and graphite spray to remove the lines... Were the lines due to decarburisation of the outside of the bars while welding? That is what it looks like to me.. Gary thanks for the info on your method too... I like the idea of going straight from the ferric into the coffee without cleaning the blade... it makes sense.
  6. Joshua, do you mix the mixture of Instant coffee with boiling water or do you use cold? This is the first time that I have heard about using a coffee etch. It seems some people use it on Wootz as well with success.
  7. A few years late.... but it wasn't anything that you did in polishing of the blade. The area along the entire blade edge where the pattern has dissolved is where the quenching of the blade has formed martinsite on the edge. This is common and expected to have the watered patterns at the edge be masked by the crystal structure of the blade. Martinsite is harder than the Pearlite body of the sword, but the price you pay for the hardness is that the pattern shows less well or not at all. Sword blades also are quenched to differing degrees due to their curve and that will affect the degree of martinsite that is formed in that place and the resulting hardness of the edge in that location. This effect can be seen in a blade that is quenched very quickly, such as a water quench... not recommended at all..., making the whole blade martinsite and it can almost entirely obscure the pattern. Hope that helps.
  8. To answer your question specifically about thermocycling, the purpose of thermocycling is to soften the outside of the ingot in order to stop the ingot crumbling under the hammer as you forge if it has a little sulphur in it, so the thermocycling is done in a gas forge with a slightly oxidizing flame. This is normally done (by Al and myself) at around 1050 to 1100 degrees C for a 1.5% -1.6% C ingot. It does help to make the ingot easier to forge through the repeated annealing cycles, which applies to both a gas and coal. But if you do this in a coal forge you won't get the same effect of decarburizing the outside of the ingot, unless you turn the ingot frequently and make sure that it gets plenty of air during the process. The traditional roasting of the ingot was for a slightly different reason though. It was primarily to start to break down the dendritic structure allowing the ingot to be forged easily and maximizing the spacing of the cluster sheets in the final forged ingot. The roasting allows the impurities in the Inter-Dendritic Regions (IDR) to migrate slowly and even out in the ingot. If you do this too long you erase the pattern and have to remelt to get it back. But it dissolves the smaller or secondary dendrites first leaving the larger ones just slightly reduced. This means that the boldness of the final pattern will be increased. You want to have large dendrites and slow solidification times but that causes porosity in the middle of the ingot if you solidify it too slowly and the excessively large dendrites will prevent you from forging the ingot. Long roasting of the ingot helps to correct for the dendrites being too large as it helps to dissolve them partly, it doesn't help with porosity though. Most of the old ingots had porosity that is why they forged them so the underside of the ingot became the surface and edge of the blade and any porosity was contained within the blade itself. The old ingots were often 5 or 6 inches in diameter and more like a discus instead of the modern ingot style. This made the ingots more likely to get porosity in the middle of the top as well.. But generally speaking you want to avoid it and not solidify the ingot too slow or it will cause you problems even if you do a long roast. Long answer with a bit of extra information.... Cheers, Tim.
  9. On reading this in the morning with fresh eyes I wanted to add something. IF you forged from above Acm and continued to forge the ingot as it cooled to be cool to the touch you will also cause problems. You should not forge the ingot to below the A1 temp (727°C) and if you did that using an ingot which was high in bloomery iron then you were approaching the area of causing problems from "Cold Shortness" as bloomery iron often has Phosphorous in it which makes the iron brittle if forged too low. I wouldn't expect problems from forging an ingot from around 900°C unless you did forge it too cold at first with phosphorous in it, but it would be a problem if you have too much sulphur and forged at that temperature. Bloom steel can make great crucible steel IF it is clean and comes from good ore AND if you don't have too much Phosphorous in the wood you are using for charcoal. My advice is that trying to make crucible steel from bloom iron with unknown carbon content and then adding crushed charcoal into it (which donates carbon to the ingot) is like playing Russian roulette. You are flirting with disaster. Making good crucible steel in the old days was a highly skilled art and it took them much time and effort to work out what would work and how to make their raw materials produce good steel.... if it could. Also it was an art-form to forge out the ingots well without wrecking them. SO... start your time of making crucible steel with known ingredients with known carbon content and impurities and then you will have a much better chance of success.
  10. One further note... The first ingot has clear porosity issues as seen from the center and it doesn't look as well fused as the second one, that will also contribute to the crumbling of the ingot. The second one seems to be much better fused and may forge better if you give it a good roasting. The bloomery iron will also have silica in a large amount which you can help to remove using some calcium added to your ingot melt. Both calcium and magnesium added to a melt help to remove silica as flux if my memory serves me correctly.
  11. Will Urban, Firstly... well done for jumping in and having a crack at making some crucible steel. Unfortunately when you start to make alloys with inspecific amounts of elements in them you can have some failures before you have success. If you have patience and get the right advice you can have a good chance of making a good product in the end. Now for some dissecting of your process and ingredients and possible problems.... 1) you have used brown glass which contains Iron Sulphate compounds to give the glass the colour of brown, this sulphur will go into your melt and it will make your ingot hot short. Meaning it will do exactly what you show, it will disintegrate when you forge it. Use green glass for your flux not brown glass. 2) you don't know your carbon content in your ingot so you have no precise idea where Acm is. Acm (the A cementite line on an Iron-Carbon Phase Diagram) changes depending on your carbon content. So if you have no experience with forging ingots before (you need a lot of experience to forge blind as far as carbon content goes) then you will be forging either too low to get a cluster sheet formation or you will be forging too high and will lose your pattern entirely. This isn't really an issue unless you have significant impurities in your ingot that make your ingot hot short, so forging high will cause you problems. You are shooting in the dark, so the long and short of it is forge at low temperatures unless you know your ingots can handle it. 3) having sulphur in your ingot which definitely came from your glass but may have also have come from your bloomery iron, will mean that you may not be able to forge your ingots at anything more than a low temperature. The ingots which were forged with the method that you are trying to use were very pure from sulphur and so they were able to be forged higher. The ingots that had higher levels of sulphur were forged at lower temperatures and they formed more dendritic patterns. The way that they removed sulphur from ingots in the old days was to roast the ore very well before the bloom process, to add manganese to the crucible and calcium to help remove some of the sulphur from the ingot as slag. 4) you have a very pronounced dendritic pattern on the top of your ingots which tells me that you probably used a slow solidification on those ingots. You may have solidified them too slow, if you did they will cause you lots of problems to forge and they can fracture as you try to forge them. The way to try and make them forgeable is to roast them for a long time. Al used to do a 16 to 30 hour roast at 1100°C (for 1.6%C) in a can filled with iron oxide (it stops you from losing too much carbon due to oxygen contacting the ingot). The long roasting helps to homogenise the structure in the ingot, dissolving the smaller dendrites and weakening the larger ones. This helps to make the ingot more forgeable and to make the pattern more visible widening the spaces between the final cluster sheets. When you are cooling your ingots just turn the furnace off and let it cool down naturally, there are few furnaces which will keep the molten liquid in that state long enough to cause problems. If you try to ramp the fuel down you will often cause yourself problems. One caution about roasting an ingot.... You have to make sure that you are roasting the ingot above the Agr (A graphite) line on the phase diagram, which unfortunately is not shown on many diagrams. It is about 50 deg c above Acm. If you do a long roasting below this temperature you WILL cause your ingot to become filled with graphite and porosity which will ruin your ingot. You may have all or only some of these problems, I listed them so you can better identify what may have gone wrong with these ingots. If you give me some more information I will try to fine tune my advice for you. I think that you have sulphur in your ingots, I also think that you have too much carbon in your ingots and that you may have solidified them too slowly. It is hard to tell without some kind of analysis or physical inspection of the ingots but that is my hunch. Hopefully you do better next time... keep trying and you will have success. Cheers, Tim.
  12. Right you are Jerrod! Thanks for clarifying. I agree that smelts are very complex with more variables and unpredictability than a crucible steel melt.
  13. I think that Jerrod was meaning "Melt", not "Smelt" which implies a direct ore reduction. Making crucible steel in a crucible in a furnace is usually referred to as a "Melt" whereas making Iron in a Bloom Furnace is called a "Smelt". There was a kind of wootz that was made in an open bloom furnace by remelting cast iron prills from the bloom process into an ingot in a quartz grit lined furnace floor. This was done in Salem and possibly elsewhere in India by a specific caste. When the iron had cooked off enough carbon it would solidify in the bottom of the furnace and then be removed and cooled. It is unknown if this produced a significant pattern or not. These ingots fit the description of ingots that were seen by Abbott and also the ingots that were sent to Faraday and Mushet. Abbott's account seems to indicate that they are the same ingots made from the same process as described in Salem and they did produce a pattern. It was not uncommon to have quartz grit in the underside and a more ductile region on the top as described by Mushet.
  14. Thanks for the clarification Jeroen, I do remember something about them industrially using coke over the molten copper in the old days to avoid picking up Oxygen and Hydrogen. Perhaps it wasn't picking up carbon in the copper readily I was remembering, but just the effects of carbon when introduced in the melt of an Iron Carbon Copper alloy. The original research that was done on Iron copper alloys back in the late 1800s by several different researchers showed that the higher the carbon content of an iron copper alloy ingot, the more brittle it is and the less able to be forged. The copper acts as a hardener for the Iron and the carbon compounds the hardening and embrittlement effect as it is also a hardening element. I haven't gone over my copper iron alloy notes for some time, I will have to dig them out
  15. Well there we go... it just goes to show that I can't remember everything. I do recall that copper can combine with iron up to around 4%, but has problems combining after that, but that it is hardened by the presence of carbon so can lead to brittleness if it is too high in a high carbon steel like this. At 0.1% it would contribute to hardening of the steel for sure. The copper would still be segregated to a reasonable degree in the IDR though, am I correct? Seeing it is a low temp melting element. Any copper alloy in the IDR I would expect to show up darker than the pure iron dendrites under an etch like we are seeing in this picture. I did some heavy research on Copper some time ago but I can't remember all that I read.... would have to check my notes. Copper is an interesting element in Steel and Iron. Nickel is one I haven't done much research on at all.
  16. HA HA... yes well the iron carbide goes without saying. We don't normally talk about the Iron Carbide as a Carbide Forming Element because it is not an element that gets segregated in the Inter-dendritic regions. Iron carbide doesn't cause the patterning that we see in Wootz, that is from the other carbide forming elements. Ni and Cu are not really good CFEs and that is why I thought it was interesting, also as far as I know they don't exactly mix very well with iron or eachother. They don't become homogeneous and that may be one reason for the dark shaddowy patterning in the background.
  17. A friend who has had years casting bronze said to me once that you never have the burner blowing against the crucible wall when melting bronze as it is detrimental to the metal, it causes bubbles in the metal if I recall correctly. But using a propane forge should be just fine so long as you keep the temperature right and use a neutral flame. The reason that cast iron or steel won't work is that they melt at high temperatures on their own but adding some other metals in contact to them begins to alloy with them and causes them to melt. As said above, copper is one of those metals. The rule of thumb is that an alloy of a metal will always melt at a lower temperature than the pure metal itself. The second you expose molten metal to another metal you begin to have an alloy form at the contact surface, some metals are more corrosive than others and that is why you cannot use a cast iron crucible for this purpose. Ceramic is the way to go. I have some nagging memory that carbon is taken up by copper alloys and it makes them more brittle... something to check on.
  18. Thanks for the analysis of the steel Daniel, that makes things a bit clearer. The low levels of Carbide Forming Elements in the steel can do some strange things with the patterning and copper can also change things in the ingot... Nickel and Copper are actually your greatest CFEs in the analysis by a long way... very curious. It is possible that the two part patterning that you are getting is as a result of these two ingredients, at least in part. I do have a question to you though before I talk more about the final blade pattern. These pics that you shared about the 1.7% inogot... were they pics of the raw ingot surface or if not, what was your processing to get it to this stage? I know what my eyes are telling me but knowing what you did to the metal to get to this stage would help to know for sure. Don't feel bad, you have produced some really nice looking steel here, and the fact that it is different means that there is something to learn from it. learning is always good.
  19. That is a very interesting pattern that you show there in your blades Daniel. It is a pain to have one break on you though. There are few reasons why it could have broken, unless you get the structure just right the steel can break if you bend it too much, or harden it severely. Taking warps out of it is generally done with a thick heated copper block placed on the concave side of the warp or bend. Flexing the blade hard before tempering it isn't the best thing with a high carbon steel like wootz. By the way, your pattern there looks like it is a combination of grain boundary cementite over dendritic sub-structure which you have then stretched and deformed due to forging processes. It is unusual, but I suspect that you let it set at just a high enough heat for a bit too long so that the grains grew large and some cementite gravitated to the grain boundaries but not all of it. Forging then at a significantly lower temperature after that preserved both your grain boundary pattern and your coarse dendritic pattern. As I said it is very unusual to see both combined, it is mostly one or the other, but that may have something to do with your steel chemistry. It is good to see you still experimenting but understand you wanting to take a break from ingots for awhile. It is much easier to control your ingots and pattern if you know the chemistry of what you are putting into the ingots. Being consistent across all your ingots is the key to perfecting your forging technique and patterning. I am sure you will come back to the "Utsa" Crucible steel has a way of dragging you back.
  20. Doug, you do and you don't. The pattern in wootz requires specific impurities in order to form and often these come from the ore body used, however some ancient processes used to add things like chromium or manganese to the melt and also the bloomery process adds phosphorous which can cause the pattern to appear. There is no such thing as "true wootz", so long as it is made in a crucible and you end up with an ingot which you forge out it can be called Wootz or Pulad. There was even a kind of Pulad in the old days that they classified as having no pattern at all.. and they still called it Pulad, because Pulad simply means Steel. The ore body from Jordan could have been used to make Wootz / Pulad, but there is no evidence that it was used for that purpose. Just because it can make a pattern doesn't mean that it was used for that purpose... Cheers, Tim.
  21. Yes what he has recently released has made that a lot clearer for many. He recently published a paper on their work, just before he released the book. It had a big section on the mechanism of banding theories and how the "dendrite" arms could rotate in the grains and line up in cementite sheets. It was the best discussion on it that I have read ever... exactly what I would expect from John . This is the paper and it is well worth a read. https://link.springer.com/article/10.1007/s11837-018-2915-z
  22. Thanks for the feedback on the book Gary, I look forward to getting a copy soon too. I know the material in it, but having it as a record on the shelf will be good.
  23. Yes there are two that I know of on Youtube. The Mike Loades documentary about Al and a friend of mine from Jordan. The other was the Nova special about Ric making the Ulfbhert sword. Both are very good documentaries and with Al you will see there are many things that he does which reveal his process at that time, if you know what to look for.
  24. I look forward to hearing your thoughts on it. I never met Al or John, but have chatted with them quite a bit over the phone and knew Al pretty well. I am glad that he finally shared their research publicly. It was a pain knowing their research for over a decade and not being able to talk about it except in general terms. I did appreciate Al's mentoring over the years though and what they researched is an important part of our knowledge of Wootz steel.
  25. I just found out that John Verhoeven just printed a book about his and Al Pendray's work on replicating Wootz and their findings. I have yet to get a copy of it, but I know John and having read pretty much everything that he has written on the subject I know it will be well worth the money. It is currently selling for around $30 on Amazon. https://www.amazon.com/Damascus-Steel-Swords-Solving-Mystery/dp/6139884837/ref=sr_1_1?s=books&ie=UTF8&qid=1535108423&sr=1-1&keywords=john+Verhoeven Al and John focused on one specific type of patterning in Wootz, the Black Wootz or Kara Khorasan pattern. Their findings were focused on that pattern, but most of what they found out also applies to the general world of Wootz making and John, being a top notch teacher of metallurgy, will not disappoint I am sure. Tim.
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