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Ed Caffrey's Workshop Talk to Ed Caffrey ... The Montana Bladesmith! Tips, tricks and more from an ABS Mastersmith. |
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#16
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If you had a set of RC files, you could test the RC. There are special sets of files where each hardened to a different RC. You try to file a little of your blade until you find one that will cut it. The blade is then between the RC of the file that did cut the blade and the next lowest one that didn't.
That being said, however, you'll soon learn by reading the acrhives of the Forums that RC is not the determining factor in how a blade performs. It's much more complicated than that. RC is just a parameter that most people recognize and associate with the durability of a blade. One of the newest steels (Liquidmetal, I think?) doesn't even need to be hardened, and the RC is around 53. But from all accounts, it's tough as nails and holds an edge like nobody's business. Personally, I pay very little attention to the RC of a blade. I'm much more interested in whether the heat treat was performed correctly, and if the particular heat treat formula has been thoroughly tested by the maker to ensure that the blade performs to the highest standard possible. 'Notherwords, test that blade to destruction, and you'll have a very good idea about how well you were able to heat treat the blade. Then make a few more, varying the HT formula a little. You know, two tempers instead of one, freeze the blade between tempers, three tempers instead of two, etc... Eventually, you'll hit on a real winner as far as heat treat goes. And RC won't really matter to you. |
#17
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THANKS
HEY JAMEY, THANKS FOR THE HELP YOU HAVE GIVEN ME. A LITTLE STORY YOU MIGHT BE INTRESTED IN, I MADE A KNMIFE FOR A FRIEND OF MINE ABOUT 2 YEARS AGO OUT OF A SPRING FROM A PICKUP. NEVER PAYING ANY ATTENTION TO HEAT TREATING.I REALLY HAD NO IDEA THAT IT WAS IMPORTANT UNTIL KNOW.BUT HE HAS SKINNED MANY ANIMALS WITH IT AND SAY'S IT HOLD'S A GREAT EDGE AND HE HAS MANY GREAT HANDMADE KNIVES AND SOME NICE FACTORY MADE KNIVES TO?? I GUESS I GOT LUCKY.
THANKS ROB __________________ rdlp |
#18
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That spring already had a good heat treat and temper applied. That's what makes it a spring. It probably would have held a much better edge with new heat treatment applied. Springs are tempered at a higher temp than knife blades. This makes them softer, but tougher and...well...springy.
And about the help...don't mention it! Glad to be of assistance. |
#19
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I thought I might tag (cough hijack cough) this thread for a bit in the direction of really refining the o1 heat treat (thermal cycling through to quenching). Most often for o-1 you hear about holding at the austentizing temp 1400-1500 for a period of time (10 min) then quenching. (after thermal cycling of course). It is of course more difficult to do in a coal or charcoal forge without thermal indicator such as pyrometers and tempstiks. I've been reading around and have come away with the idea that it might be easier, especially in the coal and charcoal to do a spheroidal anneal (heat to yellow, hold 10 min, quench, immediate sub critical anneal >1250F) for a small grain structure full of carbon. Then do a curie point (non-magnetic, ~1350F for O1) quench (instead of specifically needing to bath it at 1450F for ten minutes to austentize).
The problem this seeks to solve is both the large grain structures as well as the carbon out-of-solution-migration that can occur between curie point and the austentizing point. The problems this might introduces is grain growth at temps or too long a soak (over 10 min or over 1500F). So, would currie point thermal cycling ("normalizing", non-mag to ambient) following the speroidal anneal, followed by currie point anneal (non-mag into preheated vermiculite) work to straighten out all of the kinks? (spheroidal [yellow] anneal, 2xcurrie anneal, currie anneal). Hoping this will solve grain sizing "oops", carbon migration problems during forging, and internal stresses that can all be problems of applying heat to steel. |
#20
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I mispoke a bit, (spheroidal [yellow] anneal, 2xcurrie anneal, currie anneal) should be :
(spheroidal [yellow] anneal, 2xcurrie normalize, currie anneal). This would be followed by a currie quench. (as opposed to a 1500 soak, then quench) The currie normalize, anneals, and quenches would be conducted as soon as non magnetic to try and prevent heating the steel beyond non-mag. [Also, a neat trick for us solid fuel forgers is a oval steel / iron pipe in the hot zone of the tuyere to provide a more even heat and a visible knife during heat treat. Just let the pipe get hot before you put in the knife or you will get lotsa scale. BTW you put the blade in the hot pipe and observe colors carefully. the pipe should be dull red to cherry before you put the blade in it to prevent a too fast thermal climb in the knife steel. I'll be trying a little walnut shell in the pipe later to try and reduce the scale production.] |
#21
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foxfyre anneal
I think I know what you are describing, I have tried this before. Basicly, you are creating highly tempered martensite. I tried this with 1095 and it was a wonderful steel to work with . What I noticed most was how nice it filed... no pinning and it was very smooth after using the files. It drilled better too. haven't tried it with O-1 yet. Afterward, I heat treated as normal and was very satisfied with the results. Hope this helps.
Hello Ed, It's been a long time since I've been here. Had to use my initials so they'd let me on. Hello to Mike H. also. Dennis Tingle ABS JS |
#22
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Quote:
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#23
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Heh, who said it was easy? I'll probably never get it 100%.
I have a small question about the triple quench that maybe one of you guys can answer. (It's related! I promise! ) Coming from a curie quench for say o-1 or even 5160, you have a large probability that the austenitization was not complete when you quenched. So you'll end up with old perlite/cementite and new martensite, right? So you try again the same time, though this time you're starting with slightly smaller particles which creates smaller austenite (since it grows at the grain boundaries). Both perlite/cementite and martensite particles are consumed to austenite, but not all because you quench again at curie. Now you end up with less perlite/cementite, some old martensite, and some new martensite. Aaaand repeat that again for much less perlite/cementite, less old old martensite, some old martensite, and some new martensite. (this is assuming that you are able to heat the steel fast enough so as to avoid any significant growth of perlite, if perlite can grow... i'll have to reread that section) So is that right? feel free to knitpick but it should always be followed with a "because". |
#24
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You are correct that there is a chance that austenization did not completely take place, if the torch heat treatment was done poorly. More likely the soak time was insufficient to get all the carbon you need in the matrix. Martensite is not a particle. In my opinion (and the opinion of a scientific journal or two), seeing large increases in performance from triple quenching probably means the heat treatment was insufficient on the first try. Some gains in toughness and yield strength can be seen if it is done right. The mechanism for refinement works as follows, or at least a simplified version: austenite is formed and then you quench to martensite, which prevents the austenite grains from growing anymore. When it is re-austenitized, new austenite grains are formed instead of simply growing the original grains (as would happen with a long austenitization), this is then repeated for a uniform grain structure until the large grains have been replaced by small ones. The reason that there is a point where the grains start to get larger rather than smaller is because after a few quenches those first formed grains that were small are growing through new austenizations are growing with each new quench, so at some point your average grain size starts to go up.
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blade, forge, forging, heat, heat treatment, knife, knives, switchblade |
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