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Tim Mitchell

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Tim Mitchell last won the day on December 10 2017

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About Tim Mitchell

  • Birthday 08/06/1975

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    New South Wales, Australia
  • Interests
    blacksmithing, knifemaking, wootz manufacture, carpentry, astronomy.

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  1. Right you are Jerrod! Thanks for clarifying. I agree that smelts are very complex with more variables and unpredictability than a crucible steel melt.
  2. 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.
  3. 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
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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
  11. 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.
  12. 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.
  13. 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.
  14. 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.
  15. Gary, there were many sizes of ingots depending on the different uses and also the process used and the location.... and the century. Some ingots were round flat loaves, others were egg shaped, others were as you describe (from Hyderabad). The crucibles were sometimes fully closed and sealed, other times they had a hole in the lid to insert a rod, and other times there was no crucible at all (a bloomery furnace floor melt). The furnaces were in some cases open, heating the crucibles from below, some cases closed fully as you describe (at Merv) and some times able to be uncovered, checked and covered once again such as was used at Hyderabad in their round the clock process. It was there that they needed to know if the crucibles were ready to remove because of the cyclical process. As you can see, there were many different processes used in many different locations over a time period of close to 2000 years. Some crucibles were shaken, others were not but the final product was not controlled by the shaking, it was just a monitoring method. Much has been written on the web by misinformed individuals and some hold the understanding, incorrectly, that there was one "Wootz Process" which there was not. The only things that were consistent between all the Pulad/Bulat/Wootz processes was that a high carbon steel was produced and solidified into an ingot through medium to slow cooling and the resulting ingot was forged out into blades, tools or other useful items. Some ingots did not produce patterning due to insufficient dendritic structure in the ingot (through quick solidification), through incorrect forging temperatures, or through the ingots being so small that there was not enough reduction of thickness in the ingot to make the pattern visible. The ingots from southern India and Sri Lanka didn't produce a watered pattern as the ingots were rod like and too small in diameter, they were made into scissors, punches etc. There are few true researchers in this field and even some of the historical information can not be relied upon 100%. First hand accounts are the only accounts which are significant and what people said of the ingots in the past may or may not be true. It is a difficult task to weed out the facts from hearsay and rumour. Cheers, Tim.
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