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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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  #1  
Old 10-26-2001, 06:00 AM
edward SE
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Temper line-The saga Continues


Just getting lazy scrolling down so far in the previous thread on this topic.
But this is likely the last chapter (for this blade) because...........
Sometimes you just gotta' break it in half to see what's going on.
It broke cleanly and there was only about five degrees of permanent set in the broken halves (when I hold them together and look down the spine) and a very brittle looking cross-section.
So there we have it. Somehow I never really had a springy back.
I know the answer but still don't know what went wrong.
It's time to take a step back, spend less time on forging blades and more time on forging test pieces until I get it right. But to be honest, I am at a loss as to why I didn't get a springy back. The only variable I'm changing is to switch to an alloy which you guys say gives a more distinct line, 1084. I'll be making 'em, etching 'em, and breaking 'em. Does anyone object to making test pieces without the point or distal taper- just a constant wedge-shaped cross section about four inches long? I would also like to abbreviate the process for these first tests to just normalize, anneal, and single edge quench. I'll move up from there once I get a temper line and tough spine. Comments?
Ed E.
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  #2  
Old 10-26-2001, 06:51 AM
m l williams
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Ed, I think you are right about testing first, then making knives secondly. My suggestion is to separate areas till you find the problem. Sometimes forging and heat treating problems are not related. You might try this. Get some 1/8 or thinner flat stock of what ever steel you want to try, I would go with 5160 or 1084, but anyway, take your stock and sand off mill scale and leave flat, no forgeing. Go through your heat treating procedure i.e., normalize 3 times, anneal then harden. Temper, then sand flats. Etch to observe the temperline, then break it.This will allow you to observe grain size and flex strengths, you can get your temps nailed down in a short period of time this way. Keep notes, good ones. When you have everything like you want it forge them to shape then heat treat. If the results are not the same then adjustments to forging technique are in order. Make 'em then break 'em, over and over. It will give you amazing confidence in your blades. hope this helps mw
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  #3  
Old 10-26-2001, 12:22 PM
Joe Walters
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The only possible answer to the question "how come no springy back?" is that somehow it cooled to under 900 degrees within the 5 or 6 seconds, or your steel has something in it that made it air harden. O1 will sometimes do this. If you're having rough grain along the break line, your normalizing and or final heat are too hot. Use the magnet test and watch your steel. You have to watch for the "shadows" to play over the blade and disappear, this means you've hit ac1 and your blade should be nonmagnetic. That's excactly the right temperature to normalize and harden at (these are peculiar to each batch of steel, and even each piece of steel depending on the alloying element distribution, but usually within 50 degrees or so). Make sure your normalize 3 times, minimum, with 4 or 5 being better, especially for 5160.

1084 is my favorite steel, especially for making bold temperlines. Water and oil both work really nice, and if you want to control the shape of the temperline/hamon, use a thin clay coat on the back of the blade. The nice part about 1084 is that you have to get it under the nose of the curve in about 1 second. Miss that on the back of the blade and you'll get a temperline everytime.

Remember that you are going to be using lower temperatures with the 1084, like about 1425 to 1475 degrees F for austenizing. No distal taper won't affect a thing, provided you have a long enough soak time and the core of the steel comes up to heat. To get that refined grain Normalize, normalize, normalize, then normalize again. Once won't do it, and if you're after the best grain structure you can get, it's worth the extra time. And remember to normalize. Don't forget to normalize either, it'll stop warpage and make your steel harden alot more evenly. Then normalize the blade again. Then go to your final heat and quench. 1084 is a bit deeper hardening than most other 10XX series for some reason I can't figure out--more manganese? (at least the stuff from Admiral Steel), so watch the color on the back of the blade carefully. When it moves below a dull red go ahead and dunk the rest of the blade.

If you want a Hella-tough blade quench your 1084 into 440 degree oil and soak it there for about a half hour. Let it cool to room temp and then temper at 450. You get bainite at about a 55-58HRC, and that'll out-bend just about anything. Bainite is a really crazy structure, but you sacrifice that hard edge everyone seems to like (still can't figure out why, though).

You can coat the blade in refractory clay or furnace cement like the japanese style, get a 63RC edge and 45RC spine using a 1/8" thick clay coat with an oil quench. Takes all of the guess work out of edge quench, but it's alot more cleanup on the blade. The clay is a resist that stops the oil from cooling the back of the blade, it's not really an insulater, more of a barrier. So adjust your thickness to give higher/lower RC's on the spine.

Heat treating's fun! Remember the books aren't always right because they think in big part sizes and cross sections, and uber-clean lab steel. Every batch of steel is different, so test a piece every time you order (I once got a bar that was 1084 on one end and about 1045 on the other--lots of fun).
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  #4  
Old 10-29-2001, 07:33 AM
edward SE
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Joe,
Thanks very much. This was helpful as well as enlightening- particularly the lack of annealing in your specific process. I have been annealing in the forge at the end of the day and have gotten material so soft, it built up in my files (I do all of my rough shaping with files instead of my belt sander so the softer it is, the easier this step is in my process.) But I will do some testing with multiple normalizing and no anneal before the quench step. I assume air cooling is what we are talking about when we say anneal? Is there any other particulars of the anneal step other than letting it cool to ambient between anneals?
Yes I am moving to 1084 to get this elusive temper line and then go back to play with 5160 and then finally 52100. I am intending to quench in 140 deg mineral oil which really sticks to the blade at that temp. No vapor barrier. That tip came from Caffery and was a revolution in my process. I also intend to use his other tip to quench 1084 only once as it doesn't add much to do it more.
Comments?
Thanks,
Ed
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  #5  
Old 10-31-2001, 09:13 PM
Joe Walters
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Just let the blades cool to ambient in still air between normalizing. Your last normalizing cycle can be turned into an anneal by letting the blade slowly cool in ash, vermiculite, kitty litter, whaterver insulative stuff you've got. I do alot of drawfiling as well, but don't find a slow anneal to be necessary with 1084.

I recommend you try the multiple normalization vs. multiple quenching on a few test blades. Multiple quenching 1084 will reduce the grain size just like it does in 5160. I just never understood what the point of putting the steel through all the stresses of the quenches was, other than to reduce the grain size, which can be accomplished just by multiple thermocycling (normalizing).

Let us know how it goes. 1084 is good stuff.
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  #6  
Old 11-01-2001, 06:58 AM
edward SE
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Re: Temper line-Success


Got it.
It's so distinct, I haven't even finished rubbing, I'm only on 220 grit, and I can see it already.
I had the oil at about 180 thanks to my new heater I got from a hot plate.

It's a mystery though why the 5160 hardened at the spine.
For now I'll be using 1084 though.
Not a good time to continue experimenting.
Christmas is comming and I have to get busy on these presents.
Everyone's getting 1084 this year.

Thanks everyone for the help.
Ed E.
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