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kb0fhp

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Everything posted by kb0fhp

  1. Peanut oil is a good choice - as is canola oil. Both have really nice cooling curves, with a high boiling temperature and flash.
  2. The idea is to remove the decarb, as it can effect the results. Typically a couple of good swipes with 240 grit paper to remove about 0.003" is more than adequate - unless you really decarbed the surface. A mirror finish isn't necessary - although you will get better results that way. THe problem is the preload. If a light preload is used, then the results are more variable because of the soft surface. If a higher preload is used, then the results are better, because the loading dominates the thin decarb layer. Large forging shops - one that forge things the size of desks - usually use a Brinnell tester because the impression is large, and the loading is high to compensate for the decarburization layer. You are doing the right thing by working to get it to read the same as your test blocks. Realistically, the best you will be able to achieve is +/- 1.5 times the accuracy of the test block when reading the hardness of your parts. Improving the surface finish of your part before taking the hardness reading will only reduce the variability. Also, as a general rule, it is a good idea to take 4 hardness readings, throwing away the first one. You then average the last three. THe reason for this is to take out any backlash in the system..... Good Luck
  3. OK - you indicated that when you quenched in water - it was very hard, and very brittle, but when you quenched in transmission fluid - it did not get hard. It has nothing to do with "burning the carbon out of the rope" - if hard and brittle - you created martensite. If decarburization were present, then it would have a soft surface...Typically wire rope is made from high manganese steel. This is very hardenable and has high hardenability. It is not surprizing that the material was brittle when quenching in water. Transmission fluid is typically a straight mineral oil that is viscous and has some anti-oxidants in it to help it from breaking down at temperature. It is a LOUSY quenchant. It will be slow quenching. Use a good quenching oil that has some anti-oxidants and speed improvers. You could probably go to a heat treat shop and ask for a couple of gallons of their used quench oil - anything would be better than transmission fluid. Brownells has some good quench oils that work well. If you want to go the cheap route - try a heat treater and get some of their used oil. You did not indicate what temperature of the oil. For this type of oil, it will get faster if it is heated up to approximately 160F or so. Hotter than that, it will get slower. The reason is pretty simple. As the oil is heated up, the viscosity decreases, and it wets the part better. But as you heat the oil up, the vapor phase gets longer and more stable. Up to about 160F, speed improves because the improved wetting of the oil dominates. Above this temperature, the oil will get slower because the length of the vapor phase dominates.
  4. The salt used depends on the temperature required. Use of a salt pot is easy, but requires a lot of attention to safety....
  5. Personally, I like grounded thermocouples. The primary reason is accuratcy and quickness of response. The ungrounded probes work, but do not respond as quickly, and they tend to read a few degrees lower in temperature. The reson for that is that the ungrounded probes have the thermocouple inside, but are insulated from the outside of the shield. So you get a lag in response, and because of the insulation, a lower temperature. But either will work. I have found that the grounded thermocouples are also less sensitive to electrical noise. THe thicker the thermocouple, the longer it will last. It will also lag more because of larger thermal inertia. You just have to have it in the heat longer. K couples are good in the normal heat treating range of 1200-1750F. You need to get a R or S couple if you want accuracy and life at your forging temperatures of 2200F. K will work, but use a THICK one. Also at the higher temperatures, K couples will drift more over time. Scott
  6. Well a lot it depends on the type of metallurgy you do.....in my case: I managed a large heat treat shop producing landing gear for the F/A-18 and also was responsible for heat treatment of aluminum sheet metal, forgings and extrustion. I spent 90% of my time on the shop floor. I did this for 13 yrs. While working, I got my MS Metallurgical Engineer, and then transferred to the laboratory, where I started doing failure analysis and support for crash investigations. More time at my desk writing reports, but lots of laboratory time using an SEM, Microscopes, polishing equipment, all that neat stuff. There was also an incredible adreniline rush because we never knew what would fail at any time. At that point it would be a large effort - very concentrated to get the job done right. I was also going to school full-time working on my PhD. Once I got my PhD in Metallurgical Engineering (Microstructure development of thick plate 7XXX aluminum as a function of quench rate and aging), I quit and started working for a much smaller firm that supplies metal working fluids (coolants, quenchants, etc) to industry. In this job I write a lot of practical papers on heat treating and quenching (it you get Heat Treating Progress or Industrial Heating - you have seen some of my articles). I also go to conferences and conventions where I get to play "booth babe". I make lots of presentations to all levels - shop guys to corporate people. It is essentially a marketing position. I travel to heat treaters (captive and commercial) all over the world - from Beijing to Zagreb, making recommendations on process improvements, quenchants, racking, etc. I travel extensively - 1,000,000 seat miles in the past 5 yrs. Pay and location varies. For the midwest, a starting Metallurgical Engineer will start at about $50-60K/yr - higher on the east and west coast. Locations are typically concnetrated in a few areas - aerospace in the midwest around Witchita, KS, and on the West coast in CA and WA. There is also a large concentration of aerospace in Montreal, Quebec. This is mostly aluminum. The automotive heat treating is generally concentrated in locations around the midwest - but not necessarily around Detroit. Substantial amounts are now occuring in China, Mexico and India. The midwest is still a good place for a metallurgist - for the automotive, agicultrural and other applications. The south has a high proportion of bearing applications, with the TX area high in drill pipe applications. Foundaries and Forge shops are all over - mostly in the larger cities in the midwest. There are still a lot of large forge shops in the PA region where they use large (150,000 ton presses and larger)...A lot of closed die work is still done in the MA and CT regions. One trend that has become evident, is that a lot of shops have eliminated their metallurgists and engineering people as "non-value added". The onus falls on the supplier to solve the problems. However, the consulting business is booming because of this - the advent of the Just in Time Metallurgist. If you decide to get a metallurgical engineering degree - watch the school. There are only a few left that still have a metallurgy degree - University of Missouri-Rolla is a good practical school, and there is also Colorado School of Mines. Michigan State and a few others still offer either metallurgy and metallurgical Engineering degrees. Not a lot of people graduate with Met Eng degrees - when I graduated with my BS, only 250 people in the entire US graduated - I think the number is similar now. That number has not substantially changed. BUT, there is usually a strong market for them, with many getting 5-10 job offers when they graduate. I don't regret my decision to become a metallurgist - I have the opportunity to go into a large number of fields - mining, basic metal production, heat treating, forging, and R&D and marketing. Because it is a small field - you will meet many of the people over and over again and it is like a small community. The international community is also excellent - and I have good friends all over the world - China, Japan, US, Europe (especially Germany and France where heat treating is held in high esteem). I hope that answers your questions. I can answer more off-line if you wish. Scott
  7. Thank you - I have Pirotechnica, but I do not have On Divers Arts.....Thank you! Scott
  8. Activated charcoal, and a couple of percent sodium or potassium carbonate makes an excellent case-hardening compound. Using a steel box, lay a bit of the charcoal in it (about an inch), then place the workpiece on top of the charcoal. Cover the work piece with charcoal mixture, then close the lid of the box. Heat the contents to about 1600-1700F, and hold for several hours (after the box get red/orange). The depth of the case is dependant on the time at temperature (the term for this is called pack carburizing). Once held for the appropriate amount of time, the work piece can be removed and quenched (preferrably in a medium speed oil) as it will have a tendancy to crack in water. The part can then be tempered to the desired hardness. Alternatively, the part can then be air-cooled, then reheated to the austenitizing temperature, held there for the appropriate amount of time, then quenched and tempered. Either is an acceptable method and both are used commercially. Scott
  9. Thank you Al - I appreciate it. There are some interesting observations there (along with the BS). The use of salts is very interesting. In modern applications, most of the salts used are Fluorides - typically in 1-5% concentrations. The purpose of these is to raise the Ledenfrost temperature (the onset of nucleate boiling), and defeat the vapor phase. I really appreciate the reference. Scott
  10. I may have cross-posted this - if so I apoligize. I am a PhD metallurgist with years of experience in heat treating and failure analysis. My primary specialty is quenching (aluminum and steel) - water, oils, salt and polymers. I have been asked by Advanced Material and Progress Magazine to write and article on the history of quenching. I have many references prior to 200 AD or so, but little from about 200AD to 1850. Can any one provide me with a good set of references regarding the history of quenching? I suspect much of the dearth of information is because little was written down, or because of guild protection of intellectual property. I woud really appreciate it. If anyone has any questions regarding heat treating, quenching or other similar topic - feel free to ask me. I would be glad to help. Thanks Scott MacKenzie, PhD aka KB0FHP
  11. Houghton International, Valley Forge is the largest supplier of quench oils for commercial and captive heat treaters. They sell salt, quenchants (oil, polymer and water additives) for quenching, as well as a variety of other metal working fluids.
  12. Hi - I am a newbie. I am a degreed metallurgist with many years practical experience in heat treating, failure analysis and the like. I have been asked by Materials and Process Magazine published by ASM International to write an article on the history of quenching. I have lots of information prior to about 200AD, and lots after about 1850 when people were trying to quantitfy quenching. BUT, I have a real paucity of information from about 200AD to 1850. I have the usual suspects, Pryotechnica and De Re Metallurgica - but I have found little other than this. Can any one help provide some literature and bibliography of good references? I would really appreciate it. BTW, if anyone has any questions regarding heat treating - please feel free to ask - I would be more than Happy to help. Scott MacKenzie, PhD aka KB0FHP
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