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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making. |
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#1
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Can't get O1 hard enough
Yesterday I tried to H.T. a large bowie blade (1/4 x 1/3/4 x 12 lg) O1 Starret stock. After rough grinding the blade, I normalized the blade by placing it in the oven and bringing it slowly up to 1475 letting the blade soak for 10 minutes at temp. I removed the blade and let it cool to room temp in a warm, still area. I placed the blade back in the oven (oven temp was 800 deg). brought it up to temp let it soak for 10 minutes and quenched in 4 gallons of 130 deg Quenchall brand mineral oil. I moved the blade up and down in the oil until it quit smoking and then lowered it into the oil until it reached the temp of the oil. I removed it, wiped the oil off and tested it with a file, It by no means skated on the edge. It did offer some resistance to the file but not what I would expect. I cleaned off the scale and tested on a Rockwell tester it came in at about 59.5 to 61. I was expecting about 65. I tried this proceedure 3 times with the same results. So what am I doing wrong?
Jerry |
#2
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Jerry,
You should have taken it out of the 1450 degree oven and quenched it directly into the 130 degree oil. I don't understand what you were doing with the 800 degree stuff. My copy of the Heat Treater's Guide says to; Heat slowly. Preheat to 1200 degrees. Austenitize at 1450 to 1500 degrees F for 10 to 30 min, then quench in oil. Quenched hardness, 63 to 65 HRC. For thin cross sections like blades, your 10 minute soak at temperature should be quite sufficient. Most people seem to temper their O-1 at approx. 400 degrees. __________________ Christopher Meyer, Shenipsit Forge |
#3
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Chirs: What you described is in escence what I did except I used 1475 deg. The 800 deg was to describe the temp that the oven had cooled back down to while the blade was cooling from the normalizing cycle. it had no particular significance; It could have been any temp. it's just the temp that the oven was when I put the blade back in. I mentioned it because I tried to describe all of the conditions present at the time.
thanks for the reply, Jerry |
#4
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Jerry,
Sorry about that, I missed the part in your original post where you brought it back up to temperature from the 800 degrees. I thought that you were quenching from 800 degrees. Assuming that the steel was spheroidized annealed when you started (which is how my O-1 comes from the mill), I think you should have just quenched it after the initial heat to 1450 degrees. Once you heated it up and let it cool to room temperature, you probably needed to normalize and/or anneal it before you tried to harden it. Hopefully Kevin or Mete will pipe in, since they are the experts. By the way, the Heat Treater's Guide says; Normalizing. Heat to 1600 degrees F. Holding time, after uniform heating, varies from about 15 min for small sections to about 1 hour for large sections. Work is colled from temperature in still air. __________________ Christopher Meyer, Shenipsit Forge |
#5
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Chris, No prob. sometimes when I try to explain something it will sound perfectly reasonable to me but not to anyone else
1600 for annealing?? no kidding?. The Timken Latrobe data sheet has it as 1425-1450 with about a 3.5 hour ramp to temp. I wonder what's different? Maybe they have there own special alloy They also have an Austenizing temp of 1475-1500. I will admit that I did skip the preheat step in the hardning cycle, and my ramp was proably more like 1/2 hour, Maybe starting at that 800 deg had somethiong to do with it. But ya know guys heat treating with a torch don't do any of those things and still get good results. Jerry |
#6
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Jerry,
The difference in annealing temperature recommendations led me to check Starrett's website. I could not find the info, but it reminded me that the label on the steel does have some information. I scanned the label and I'll post it here in case anyone needs the info. Notice that the label says "For further information, see catalog." Naturally, the online catalog says "Heat Treatment and Tempering Data available upon request." __________________ Christopher Meyer, Shenipsit Forge Last edited by Chris Meyer; 02-21-2006 at 05:10 PM. |
#7
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Thanks for posting that Chris. I did a search on O1 H.T. instructions and it seems that the methods vary as to the manufacturer, so i guess that one doesn't just buy O1 or any other steel and assume that it Heat treats just like any other steel with the same ANSI number. I still can't figure how someone using a torch gets better results than I can using a controled temperture source.
Jerry |
#8
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"I still can't figure how someone using a torch gets better results than I can using a controled temperture source."
Jerry, not to offend anyone, but I doubt they can. __________________ Christopher Meyer, Shenipsit Forge |
#9
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ive used a torch on O1 quite a few times...im not saying my results are better but each time a file skated over it with no probs. i dont have a rockwell tester here so im not sure what they are coming in at.
i do almost always use a water quench (oil fumes were a very bad thing in my old shop) im not doing anything special and if i had an oven here i would certianly use it over a torch. my process is close to yours but with shorter soak times, and i eyeball the steel to judge the temp. to me it seems like your method would skate a file too. |
#10
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For O-1 in a blade you don't have to worry about preheating . You should have left the furnace at austenitizing temperature after normalizing . What do you mean "up and down in the oil" ? It should be held completely under the oil but agitated up and down or back and forth [not side to side]. NO 1600F for normalizing ! Use 1500 F. You are starting out with spheroidized annealed , decarb free stock. Are you sure you're letting it soak 10 minutes from the time it's FULLY at temperature ? It may take a long time to get to the 1475-1500 F in some furnaces . Make sure the furnace is fully at temperature put in the steel ,make sure the steel is fully at temperature ,time 10 minutes and quench !
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#11
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Hi mete, thanks for the reply,
Quote:
Jerry |
#12
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If this is O1, the problem is in the soak temp or time, and not in the quench. The O1 I work with reaches a consistant 64.5HRC with little effort. On heating methods and ability to hold temp I would reffer folks to another thread here:http://www.knifenetwork.com/forum/sh...ad.php?t=33595
The issues involved in soaks for the 1095 pictured there is amplified much more with O1. industry has some narrow parameters and also has different measures of success because of it. All samples in the other thread snapped clean like they were fully martensitic, the pearlite plagued ones took more force as they were all broken untempered, and all dulled my file like they were glass, but the Rockwell tester gave me hints as to which ones would have the least gray splotchy fields under the microscope. |
#13
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Oh yes, BTW, I austenitize spheroidized O1 at 1500F for at least 5 minutes after the rebound of the salts and then quench into oil or low temp salts. I was at less than 3 minutes when all I had was the files, I have been pushing the soak time out after a few years of comparing HRC values, now I am certain I will start pushing it out some more after observing the actual structures within the steel. Files, breaking and looking, Rockwell testing, microscopes, each step up in the analysis tools gives me a more complete and accurate look at results, and as I have said many times before- there are times I wish I had just stuck with the file and remained happy and unfettered with these burdens.
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#14
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Kevin, thanks for the reply and the link. Although I got lost in the discussion I believe that I got the general idea. I will experiment with the time and austenizing temp to see if I can bring the Rc up. As far as snapping and looking at the grain structure I don't have access to the equiptment to see beyond if it is fine grain or coarse grain. Is the edge flex test (a.ka. the brass rod test) a good indicator as to the condition of the metal. Of coarse this test can only be done after tempering but it seems to me that the conditiion after quench and after the tempering cycles has to be directly related. I'm not looking for short cuts (other than picking the brains of people way more knowledgeable than myself) just looking for a valid way of telling what I have using the resourses that I have available to me. which are files and a Rockwell tester plus the typical bladesmith tests.
Jerry |
#15
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No reasonable smith should need anything more than some files and the ability to do Rockwell testing, microscopes are ludicrous overkill by neurotics like myself. The brass rod can tell you a littel bit about the heat treatment, just be very aware that it is much more heavily effected by blade geometry than by the heat treat. Breaking the steel and having a look is one of th simplest tests that require no extra equipment, if you can see the grains they are too big. The fracture should be smooth and clean, jagged bits and ridges indicate some pearlite in the martensite.
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blade, forge, knife |
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