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kb0fhp

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  1. Polyethylene glycol will not work because it doesn't have the inverse solubility that other PolyAlkylene Glycol quenchants, or other types of polymer quenchants.

     

    Polymer quenchants are the result of some pretty intense type reactions - and a lot of the feedstocks are expensive. However, the in-tank costs of the commercial quenchants are substantially cheaper than oil. For instance, using a modern quenchant at about 10% (similar to a fast oil), the cost is less that a couple of dollars per gallon. This is less than half the cost of a commersial oil quenchant.

  2. Scott,

     

    The Islamic countries used wootz steel for their blades and the cutting ability of that steel depends on the lamilar carbide structure and not so much on full conversion to martensite. I will look for sources, but from what I remember most of it was air hardened. Galloping horsemen are mentioned, but more likely windfunnels were used if anything at all.

     

    "Their scimitars are very well damasked and exceed all that the Europeans can do, because I suppose our steel is not so full of veins as the Indian steel, which they use most commonly. They forge their blades cold, and before they dip them, they rub them with allow, oil or butter to hinder them from breaking, they they temper them with vinegar and coperas, which being of a corroding nature, shows these streaks or veins, which they call Damask work." Sir John Chardin's Travels in Persia, London, 1927 pp. 270-271

     

    Check with John Verhoven, Iowa State University he has done extensive laboratory and research into wootz.

     

    The idea of applying something prior to quenching, is similar to what the Japanese did:

    al-Biruni, writing in the Kitab al-jamahir fi ma'rifat al-jawahir, in the 11th century AD, specifies what dawa is in Indian practice. He writes “…in the process of quenching the sword they coat the flat of the blade (matn) with hot clay, cow dung and salt, like an ointment, and clean the two edges with two fingers….” This is similar to the process of making Japanese blades, and the application of yakaba-tsuchi clay. wiping it off with two fingers imples the "negative" method in application of clay.

     

    I appreciate that reference - it will be a help. I have to finish this article up quickly - it is due at the publisher on Friday!

     

    Scott

     

    Richard:

     

    Thank you! I appreciate it. I really should have searched the archives prior to asking the question. I won't make the same mistake again.

     

    I subscribed to the arch-metals newsgroup - very interesting stuff. THey have been extremely helpful.

     

    I am waiting on the activation of my account in the sword forum....

     

    Thank you

     

    Scott

  3. TRULY COOL PICTURES! Would it be possible to email me copies of those pictures without the anotation? I would like to include them in an article I am writing for Advanced Materials and Process on the History of Quenching. If you could tell me how you want them to be attributed, I would appreciate it.

     

    Because of the small size of the parts, or rather the small thermal mass, the vapor phase will be very short-lived. What you are seeing is the nucleate boiling phase, and finally the convection phase. The clay (yakaba-tsuchi - right? I am trying to learn) is designed to initiate nucleate boiling quickly. The powdered charcoal mixed with the clay burns out, leaving a series of micropores - these initiate the onset of nucleate boiling quickly - so you really shouldn't see much of a vapor phase. Perhaps if the object were larger, you would see a persistant vapor phase.

     

    Scott

  4. I have been doing a lot of research, and found out a lot of information regarding quenchants used, and the methodology of quenching. However, I have not been able to find any good references for quenching from Islam. Could anyone please help - for instance with the quenchant, and the source? That would be a HUGE help. I am under a huge deadline and I shouldn't have undertaken such a huge topic with such a short deadline.

     

    Thanks you for any help that you can provide.

     

    Scott

  5. some people say there is - it is essentially a wetting stage - this was proposed by Dr. Tensi at the university of Munich. Generally it is so fast, especially for small items that it is inconsequenctial. But for larger items - like an anvil - it may be important. Really, it happens so quick that it really doesn't effect things.

  6. As you quench - there are three phases that occur: Vapor Phase, Nucleate Boiling, and finally Convection.

     

    The vapor phase is really superheated quenchant. It makes a contiuous gas film around the part. Heat transfer is very slow in this quenching stage, as heat transfer only occurs by radiation. As the part slowly cools, it reaches something called the Leidenfrost temperature. This temperature is the onset of nucleate boiling. There are a variety of things that effect this temperature, geometry, surface roughness, quenchant, etc.

     

    Nucleate boiling is very fast. It generally starts at a sharp corner and progresses as a wave front from bottom to top. Often, at the same time, another nucleate boiling wave front will form, and start a wave front working its way down the part. Heat transfer is VERY rapid - generally 10 times faster than the vapor phase. It is charectorized by the formation of bubbles that carry the heat away from the part, allowing colder quenchant to come in contact with the part. Once the parts cools down to around the boiling temperature of the quenchant, then convection occurs.

     

    Convection is a slow heat transfer mechanism, that is governed by the amount of agitation present. The greater the agitation, the faster the quench. However, this is also in the range of most of the transformation to martensite - so if too fast, then cracking can occur.

     

    Remember that distortion (with cracking being the extreme boundary condition of too much residual stress or distortion) is a function of temperature gradients. These gradients are either surface to surface, or center to surface. The larger the temperature gradient, the larger the amount of residual stress - hence uniform agitation is the key.

     

    Check out http://extranet.houghtonintl.com/HeatTreat...%20Articles.htm and select the advances on quenching article. It will show what I mean. I am sorry for being so long-winded.

     

    Hope that helps.

     

    Scott

  7. A lot depends on the steel that you are quenching. If 1080 or something like that, I would suggest warm oil about 160 or so. As you heat up oil, the viscosity goes down, and wets the part better, and the oil gets faster (but better distortion control) - but the vapor phase gets longer. Above that temperature (and it varies), the vapor phase gets longer, and the oil gets slower.

     

    Regarding water, the warmer the water, the slower the quench gets - it is also in the wrong place, so you could get poor properties, and a cracked part. If you want a fast quench - use cold water that is being agitated. You could also add a couple of percent of salt - that will help cause the vapor phase to be unstable, and make the quench faster.

     

    Hope that helps.

     

    Scott

  8. Thank you Mete - I found a translation of the Divese Arts - he mentions some interesting quenchants.....I believe he is the source for the "urine of a red headed boy quenchant", and "the urine of a goat fed ferns for 3 days...."

     

    I found some good chinese texts, which I am hoping to have translated by my counterpart in China...I will let everyone know what I come up with...

     

    Thanks

     

    Scott

  9. That actually works real well. Use a big diameter pipe nipple, and cap one of the ends. Put some charcoal in it - and then cap it lightly with another pipe cap - only one or two threads (you want to be able to release it when hot).

     

    You can also do the same thing if you ever want to try pack carburizing. I think the borax will also prevent carburization in places you dont want - for instance, you want to carburize the edge - but not the thick part of the blade.

     

    It would be worth a try. There are also stop off compounds that you can buy...I ahve my own preferences, with no commercial interest - just practical experience.

     

    Scott

  10. Absolutely - I first came to this board to learn some history. I guess I am hooked now. I would be interested in learning the history of many of the things I see here - why the specific shape, historical techniques, etc.

     

    Thanks

     

    Scott

  11. That would work fine - and prevent decarburization during normalizing and hardening.

     

    It should not scew up the hardening at all - assuming that it is a light coat (too much and it might insulate it during hardening - depending what you quench in...).

     

    I am not sure how you would remove it prior to forging....

  12. The stuff is a truly a pain to forge because it is so strong. It also has a lot of Vanadium, so it has good secondary hardness. Lots and lots of pressure! From the ASM book - HEat Treating GUide to Ferrous Materials, the recommended forging temperature is 2250F, and to stop forging if the material drops below 1650F (You would know it because the required forging pressures start to go up real fast!). Slow cooling is mandatory to prevent cracking.

     

    For a spherodizing heat treatment, heat to 1380F, then cool rapidly to 1300F, then cool to 1050F at a rate not exceeding 5F per hour. Cool in air. Alternatively, you can heat to 1380F, then cool rapidly to 1200F, and hold for 12 hours. Cool in air.

     

    Can you please explaine to me about Decarb? :blink:

    Thanks Ron

     

    Decarburization is actually the carbon coming out of the steel. It is the reverse of carburizing, where you are putting carbon in the surface of the steel. If you measure the carbon content after heat treating in air, it goes down in a very predictable manner - forming scale. It is possible after long times in air to have nothing but iron at the surface, with steel in the interior. This can also be a source of cracking, since iron is weak, and steel is strong, the residual tensile stresses cause the weak iron or ferrite to break.

     

    Here is a good picture of decarb:

     

    1090-01.jpg

     

    It shows virtually all the carbon is gone from the surface.

     

    Hope that helps.

     

    Scott

  13. Instead of the long normalization cycle, which can also contribute to banding of Chrome, I have found a good sphereodization anneal works muc better, and provides a much more uniform microstructure. Typically the normalization was done after the large forgings to make them easier to machine. BUT with the advent of much more hardenable alloys, such as 4340 Modified, 300M and the like, the cycles had to get really long to achieve the same ends as with lower hardenable alloys. Unfortunaletly, it turned out to cause other problems, such as banding of Cr, which causes local regions of much higher hardenability, and adjacent regions of lower hardenability. One of the interesting things, is this banding shows up as light and dark etching regions, which was thought to be the resons for the "Damask." It has since been proven not to be the case.

     

    Try a long spherodization anneal - you will get a uniform heat treat, and much better response to heat treat. You will also see lower distortion. It is also a lower temperature, so it is cheaper to do.

     

    We would consistantly get 300ksi ulimate tensile strength, and 285 ksi yield strengths, with 10%+ elongatiton, and 45% Reduction in area on a tensile test. We just had to make sure that we made the tensile specimens properly, with out nicks and sratches.

     

    We also made sure we quenched in a VERY slow oil - Houghton Soluble #2, which was created in the 1920s and still around. It is also one of the few oils still mentioned in BAC specifications and also McDonnell Douglas specifications.

     

    Scott

  14. Actually it is a mixture of CO, CO2, H2 and H2O (about 20%CO, 0.5%CO2) with 40% H2 (balance N2). At austenitizing temperatures the atmosphere is safe. It only becomes explosive below 1400F. But there are a variety of things you do to keep it safe - flame curtains, nitrogen purges triggered by low temperatures, etc.

     

    A carbonacuous atmosphere, such as a pipe with charcoal at the bottom will do a fine job of protecting the part, and minimizing scale. If you pack the part in carbon/charcoal - you can carburize the part if you leave it in a long time. If you need times/temperatures for carburizing, I can help with that.....

     

    Use of borax slurry, with a carbon atmosphere will go a long way to prevent decarburization. I used something similar protecting landing gear - using a borax slurry with a solvent base, making a protective paint. Once the solvent went away by evaporation, I have a nice adherant paint. The landing gear was then put in an endothermic atmosphere from cracking methanol and nitrogen. It was just a measure of insurance - if I trashed a bunch of landing gear they would have moved me into management and taken my brain away.....

  15. I liked that article - thank you.

     

    I need more information regarding etching. What is the material, what was it etched with (concentration temperature, etc), and what was the probable microstructure - martensite and pearlite? I am not sure - magic? :)

     

    I will have to do some digging in a couple of metallography/etching texts.....

  16. I saw the magnet - it was impressive. It had another magnet on the outside, with opposite polarity to counteract the field so there was minimal leakage. It was about 4 feet in diameter, with a hole about 6 inches in diameter......

     

    But it was really cool!

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