Jump to content

Tim Mitchell

  • Content Count

  • Joined

  • Last visited

  • Days Won


Tim Mitchell last won the day on December 10 2017

Tim Mitchell had the most liked content!

Community Reputation

27 Excellent

About Tim Mitchell

  • Birthday 08/06/1975

Contact Methods

  • Website URL

Profile Information

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

Recent Profile Visitors

732 profile views
  1. Jerrod, adding Mn to steels is the old fashioned way of removing sulphur from the melt, and obviously it wasn't perfect or the Persians wouldn't have gone to the expense and bother of getting their ingots from India. Can you shed some light on a better solution... other than don't have sulphur Also perhaps you could add some information from your expertise on the negative effects of MnS on steel. Ditto on the copper it isn't an issue and many blades had significant levels of copper, it acts as a hardener in small levels and adds toughness to a point.
  2. Hey Will, as Daniel said, your Phosphrous level in the ingot is way too high (maximum is 0.05%), if you want to remove P from the ingot you can add Calcium Carbonate or shell to the melt and that will help to lower the level. P in an ingot will make the lines more fuzzy and less defined, cold short and to a degree hot short. The carbides increase in number but the contrast drops. The main problem though is that you have too much Sulphur (over 0.02%) which will make your ingot crack when forging too hot or too fast. The other issue is your Silicon level is a bit high (should be below 0.1%) and it may be adding to your troubles but not as much as your Sulphur. Adding some Manganese will reduce the sulphur levels but don't add too much or you will have the pattern darken. Calcium Oxide will react with Silicon to form the flux Calcium Silicate which will separate from the steel and float on top. It seems that your steel would benefit from adding both Calcium and a bit of Manganese. So your ingot is slightly cold short (cracks when forging too cold) and hot short (cracks when forging too hot) so you really need to remelt with some shell and a bit of manganese to get those two levels down. You can reduce sulphur a bit through long high temp roasting in iron oxide but you will lose some carbon and you don't have much to lose in this ingot... so manganese is your friend at this stage. I would avoid going above 0.5% Mn, you can go to 0.9%Mn but at those levels it darkens the steel background and masks the vanadium carbides. It makes the blades more hardenable but there is a pattern trade off. Even with lower levels of manganese you will still get dark lines of manganese in the pattern being visible. It doesn't take much, perhaps even 0.1% to be visible as dark shadow lines in the pattern going across the vanadium pattern. But it is better to have some manganese lines than to have hot shortness. As I said I would suggest that you need to deal with the Sulphur by adding up to 0.5%Mn. You can use the steel as it is with the additions and have success without diluting the steel, but you will need to remelt the steel. I would add just a smidgen of carbon back in just to make up for what you have lost in forging and oxidation in the forge. Take the cracked ingot portions and remelt them with Calcium oxide and with Mn and I believe you will have success. The levels of Phosphorus are not disgustingly high, because even higher amounts were found in Ottoman blades of the same carbon content. But you have to deal with the Sulphur and the Silicon which are both too high. The benefit will be you will lose some Phosphorous at the same time.. Happy days Be aware with these analysis levels you will be getting an Ottoman kind of pattern. You can see now the benefit of getting a good analysis of your materials. With a bit of good advice you can get a good result without all the shooting in the dark that the ancients had to do. All the best and please document what you do and continue to share it with us all.
  3. I think that it would be so difficult to trademark my design even with first use as there are now so many similar designs out there and clearly not trademarked either, it would almost fall into common use in current times even though it wasn't back then. Once you trademark then you have to defend and that looks like lots of distasteful legality which I don't desire. I am considering my options for the future if this starts to become a more regular thing.
  4. Thanks Gerald, I did a search for Alpha Omega genearally and it is amazing how many people have this kind of symbol on various other businesses. When I started out 17 years ago I was the only one who had this kind of symbol in any business, all these are recent designs. He has agreed to change his design to prevent brand confusion, but looking at the number of similar designs out there this may become a problem for me in the future... It is something I will have to think about. I am not concerned with other businesses, mainly in the knifemaking field being an issue. There was another knifemaking company who did a sample run with the same sort of logo but they are not operating anymore. Thanks for the feedback, it was an area that I wanted to tread lightly with and I appreciate your thoughts.
  5. Hi all, I have been using my maker's mark on knives since around 2002 and today I came across a guy using a very similar makers mark. I am looking for some feedback concerning if I should ask him to change his mark or not. Mine is on the Ricasso and his is on the pommel of the knife. As you can see the marks are pretty close and his looks like a slightly stylized version of mine, essentially he has just lengthened the legs of the A. They look close enough to be confused by some customers which is something that I don't want. Please be free with your comments... I don't want to be a stick in the mud, but I also want to protect my mark. Cheers, Tim.
  6. AA stands for Atomic Absorbtion and it is a kind Optical Emissions Spectrometry.... Just the old time word for it
  7. 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...
  8. 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.
  9. 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.
  10. 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.
  11. 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.
  12. 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.
  13. 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.
  14. 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.
  • Create New...