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Posts posted by kb0fhp

  1. Cool - I started playing with HKL just before I got laid off. EBSD is really neat stuff. You may want to pick up the text Electron Backscatter Diffraction in Material Science edited by Schwartz, Kumar and Adams, Kluwer Academic Press. It was $79 on Amazon. You may be able to get it via library loan.....


    I used EBSD to identify textures in aluminum, and tiny precipitates at grain boundaries for my PhD.....

  2. Try Shewmon's Diffusion in Solids - a good if not dense book on duffusion. I believe it will have the data you need for a variety of different diffusion couples. It MAY give the grain boundary enhanced rate - else it may just have the rate in a standard couple. One fairly decent method is to use EDXF in an SEM to measure rates - apply different times, and measure the depth of penetration at the grain boundaries. Use element mapping and measure the penetration at the grain boundaries.


    Out of curiousity, what is the application?


    You may want to ask the moderator to move the post to the metallurgy forum.



  3. Jacob:


    For a good explaination of what is happening during quenching, try looking for the file "Houghton on Quenching" - it is a good non-commercial overview of quenching and what happens to steel during heat treatment. The file is available in the archives and you should be able to find it with a search. I would also recommend the Timken "Handbook for Metallurgists", which is also available in the archives....


    I am with you. I travel a lot (so far over 175K seat miles this year - all domestic), and I would much rather talk to the person at the ticket counter than go through one of the check-in kiosks.....you generally get better service too.



  4. Park #50 is a low viscosity (about 45 SUS at 100F) oil, with a flash temperature of about 285F. This is a very low viscosity oil, and is really suitable for cold (below 120F) quenching. I was not able to determine the speed of the oil, but suspect it is a fairly fast oil based strictly on the viscosity. I do not think that it has any speed improvers or antioxidants - but I am not sure. I know many of the people at Park personally - it is a small industry, and they are a good competitor.


    Personally, I prefer a thicker oil that I can run at higher temperatures to take advantage of the benefits of reducing the temperature differential (resulting in lower distortion and residual stress). It also has a higher flash temperature (at least 350F), which provides a bit of added protection.


    We offer a variety of oils - at viscosities from about 70 SUS (very light oil) to 2500 SUS (slightly less thick than molasses), suitable for temperatures from ambient to roughly 400+F for petroleuem based oils, to canola based products. They are available in speeds from very fast to very slow. They are available in 5 gallon quantities - up to multiple tanker loads. In my heat treating shop - we only used Houghton products. They are available directly or via distributor.


    I didn't mean to turn this into a sales pitch - if you have specific questions, please PM me and I will help you select the best oil for the application. Take a look at the file "Houghton on Quenching" - which I believe is buried in the archives. If you can't find it - I can email it to you, or give you a CD. It covers the basics of quenching, and is very non-commercial in nature - and we want to keep it that way. It will answer a lot of questions that people have on quenching. I used it as an undergraduate in metallurgy at Ohio State and Carnegie Mellon.



  5. The Curie temperature in Nickel is used as a comparative measure of oil speed. A nice article, which explains how it is applied to oil spped analysis is shown here.


    This test is called the GM Quenchometer test, and is a very common test.


    Ac3, is the temperature where ferrite completely changes to austenite - and is the upper bound on the two phase field of ferrite and austenite. Ac3 is also called the critical transformation temperature - short for Austenite transformation critical temperature. It is also roughly the Curie temperature for most steels. Attached is a chart showing how the curie temperature changes for steels. This image is from S.L. Semiatin and D.E. Stutz, Induction Heat Treating of Steel, American Society for Metals, 1986:






    While the critical temperature (you also need to specify pressure) for gas and liquids is one definition - where all three phases, gas, liquid and solid exist at the same time, the Ac3 is the critical temperature where austenite transforms to ferrite or vice versa. I hope this helps.



  6. Standard metallurgist answer - it depends. But assuming a fully quenched structure, the hardness will be HRC 57 at 475F, HRC56 at 500F, and HRC55 at 525.....But there is some variation on chemistry, tester calibration, etc. I would expect that the hardness will in the range of 54-58. Differences of one HRC are not really statistically measureable or significant. Even using a calibrated test block of impecable quality, it is stil accurate to +/- 1 HRC - and most machines are +/- 1.5 the test block tolerance......


    Hope I didn't cause you too many questions...



  7. Just to add my two cents worth - my company can also supply quench oil - all types - from very fast quench oil to very slow oil-based quenchants, canola based quenchants, polymer quenchants, marquenching oils, etc.


    PM me if you are interested, and I can direct you to the proper contact.



  8. Indium,tin and bismuth are all conductors so an alloy of them would also be. Field's metal is also expensive but I may have to try it real soon.



    Trouble with those metals, is that they cause either solid metal embrittlement - or liquid metal embrittlement. Results in the quenchant diffusing into a short way into the steel, coating the grain boundaries, and causing the stuff to be very brittle. Results in an intergranular fracture to the depth of the penetration.....

  9. Somewhere on my old books I read that the one of the faster quenchant is the mercury-quicksilver, since the thermal conductivity is very high; did someone here ever done some test?



    MErcury was used - as was molten lead. Still is being used for limited applications. Very fast and uniform heat transfer - something like quenching in a salt bath but much faster - there is also the benefit that the heat transfer is all conduction.


    But the people that did do this, and now responsible for an EPA super-fund clean up.....


    There are better, safer things to do now....

  10. OK - depending on the etchant, steel does dfferent things. Using a standard 2-5% Nital Etch (Nitric Acid in Methanol- water works too but not as well) - untempered martensite will not etch. As tempered martensite - it will get darker. Pearlite etches dark. This is a standard etch for steel metallography. Other etchants behave differently....Have to check some old books to see what others do...

  11. Lost foam is easy - and a lot of fun. You make the pattern from syrofoam - and pile sand around it....make a little hole to pour the melt - allow to gass off - and out comes a nice piece. Things as complicated at engine cylinder heads are made that way...


    The brittleness of the copper could be from P or O.....polishing it and looking at it under polarized light at magnification. If it is bright ruby red it is CuO and oxygen. P won't show anything....

  12. I understand - I am interested in the making of the bloom, as well as many of the older methods. One thing I have always toyed with, is making a small blast furnace...I have built small cupolas when I was in college - melted enough iron that we were able to cast a small cast iron bathtub - including the claw feet. Being a metallurgist - it always gets lonely when I don't have hot metal around. As a summer student I used to work on the melt shop floor of a blast furnace, and shoveled alloying elements in one of the last open hearth furnaces in the US - now long gone.


    There are many old smelting furnaces in the area that I live - some I have found just driving around. I would be interested in the specifications of the furnace. If I can find a smelting operation near me - I would love to see it in operation (and pester with dumb questions).



  13. OK - I understand that....


    I was just curious, since a simple blast furnace design using hematite can be accomplished....


    I absolutely understand about the fuel consumption - it takes a lot of fuel to create molten iron. Now, that said, do you do any sort of energy balance to make sure that you have enough fuel to create the bloom, and adequate flux to help reduce the hematite? Being the lazy geek that I am, I want to make sure that it works (or at least has a better chanceof working) the first time.


    I think I can did out some old notes I did a long time ago on reducing iron.....



  14. They say that from lighting the burn to when it is at the right temp takes 3 hrs. Then they kept feeding the beast between Midnight and 6am.


    The 28kg of hematite are loaded 500g at a time.


    The participants had spent the afternoon breaking charcoal into pieces of the right size.


    They keep the iron "froth" (in the tub) to seed the next burn (but no details on that).



    Maybe I am missing something.....IF the idea is to reduce the hematite and produce molten iron at about 1%C - why not make a small blast furnace? The principles are the same, the difference is that you can tap the hot iron in to a series of pigs. A lot of the calculations have been published, and a lot of the things to increase efficiency have been published - like preheating the blast air, etc.


    Or is the idea to make steel like the ancients did?


    I don't mean to be impertinent - just curious.



  15. I didn't beleive it at first either. But I had nice round dimples (no jokes), and when I sectioned them, I found a nice deformed layer, like what would occur in a brinnel hardness test. THe pressures from cavitation are impressive - several Gpa - and remember, aluminnum is soft with very little strength at temperature....I remember inspecting every piece before quench and found nothing - but after quenching, it was dimpled like a ball peen hammer hit it...thinking about writing a paper on it if I can find the time.....

  16. Decarburization can be a problem in molten salt at elevated temperatures of austenitizing. It could from a salt bath that needs neutralization. One easy way to check is called the razor blade test. Take a steel razor blade - not a stainless one, and immerse it in the salt for an appropriate mount of time for your blade or part. Remove the razor blade, and quench it in cold water. Wearing gloves and safety glasses, put the razor blade in a vise, and use a pair of pliers to bend it. If the blade snaps, decarburization is not a problem. If it bends and deforms, then the bath needs rectification.



  17. It is POSSIBLE to get cavitation induced deformation during quenching of aluminum. However, I have only seen this is deep quench tanks - 20 feet or so, in polymer quenchants, when the solution was absolutely saturated with dissolved air. In one case it was determined to be caused by air agitation. The second case was caused by saturating the solution with air to prevent bacteria from growing in the polymer quench.


    It is often called pitting, but close examination of the pits by way of a cross-section thru the pit showed that it was more of a dimple, with deformation at the edge of the dimple.


    The pressures created during bubble collapse are very large and are easily enough to cause dimpling of soft hot aluminum (remember aluminum is heat treated near its liquidus). I have not seen the same phenomina in steels. I don't expect to see it in steels because of the hot strength of the steel.


    One possible source of pitting is the quenchant. Remember, the hot surface of the steel is very active. The presence of large amounts of salts in the quenchant could conceivably cause pitting.....


    Can you post a picture of the pitting so we all can see? It is hard to make a determination from description alone.





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