View Full Version : Warped D2
08-28-2010, 10:04 PM
I've got a D2 blade that warped. I'm trying the old "clamp it past straight and temper it again" trick. If that doesn't work, what are my options? Can D2 be re-heat treated? What would I do to anneal or soften it so I could get it bent back straight?
08-29-2010, 11:49 AM
You can try some method of cold straightening; I take what you mean by "clamp it past straight" is bending it over three rods in a vice, which is one way of doing it. Any steel that can be heat treated can be heat treated again. You could try heating the blade back up the the tempering temperature that you use and seeing if that give you enough heat to facilitate straightening. I tried it one time with 9260 and found that it wasn't enough heat. You may have to heat it back up to non-magnetic, if that doesn't work, and straighten the blade before if fully air quenches. I have never worked with D2 but I would re-austinize and air quench again after I got it straight just to make sure it wants to stay that way. Now, that said, there is no guarentee that the blade will not crack in the process any more than one can guarantee the the blade won't crack the first time. I did have a 9260 blade that I had to reheat to straighten only to find, after grinding the fire scale off, that the edge had cracked about 1/2" deep into the blade. Though I must said, other than that, it looked real good.
08-29-2010, 12:25 PM
FWIW, clamping it past straight and then running it through a temper cycle got 98% of the curve out. I reset the clamps to capture that last 2%, and have it tempering again. Still, no one really answered my question for next time. Metallurgically, can D2 handle a simple re-austentize and quench, without any other steps (annealing, stress relieving, etc.)?
08-30-2010, 09:19 AM
It does not answer your question but I am very interested in what type of jig you have that can be put in an oven for the "Clamping it past straight" part.
08-30-2010, 11:08 AM
Not much of a jig. I make some file blades, so I have all kinds of file stubs sitting around. I usually take a piece of a file the full length of the blade, and a stub the length of the handle. I clamp all three (blade, file, stub) together with one or two clamps, with the curve of the blade going away from the file. Then I take another clamp and clamp the blade tip back past straight. I throw the whole contraption in the oven on my second tempering cycle, usually 400-450. Let it temper for two hours, then undo the clamps, and most of the time the blade is straighter than it was before. Sometimes you don't get it right and have to do it again.
Rough diagram of the setup as it goes into the oven. X's are clamps. Longest line is full length file. Short middle line is file stub.
Bottom line is warped blade, clamped past straight.
08-30-2010, 02:18 PM
Got it. Thanks.
08-30-2010, 11:16 PM
That li'l trick has saved the day many a time for me. Worst one I ever did took 3 or 4 cycles to get there. Most of them straighten up good in one cycle.
08-30-2010, 11:27 PM
How do you avoid the warpage in the first place?
What caused the warpage in the first place?
08-31-2010, 07:14 AM
I've learned a couple warping lessons. One, it seems like on my 1080 blades that those with an edge quench or clay quench want to warp more often. A full hard blade is less likely to warp in my experience. Two, don't lay a blade down on one side after the quench. Either stand it up on the spine, or put it on a wire rack. If you take a fresh quenched blade and lay it on your anvil, etc., it will warp. Three, normalize multiple times prior to heat treat if the blade is forged. As far as this particular blade, it was a 6 inch hunter of 1/8 D2, and I put it in the foil packet along with a small 3.5" keychain knife, also of 1/8 D2. After the soak, I pulled the packet out and put it on my wire rack to air quench. My suspicion is that the small blade held some heat that made the larger blade cool unevenly. Uneven martensite formation is what causes the warping. That's also why they say don't agitate in the quench side to side, only tip to butt or edge to spine. If you're stirring sideways, one side of the blade will cool faster, and you'll warp. There may be other reasons and cures for warping, but I can verify that what I've said in this post is true in my experience, may not be universal, but is not just some jibberish I learned on the internet.
08-31-2010, 10:58 AM
I think you are right. I don't put more than one blade in a foil pouch and I would open it right away and take the blade out to cool. The foil can sometimes draw and cause warpage. I thin one of the easiest things you can do is to have you grinds as symmetric as they can be on each side. If I ever get warpage, it is usually the tang. I taper every tang. I will clamp it "Flat" against a piece of D2 I have and in one temper cylcle it is usually straight. You can always just heat treat it again without any other steps. I've done it and the blade was fine. I've done it one CPM 154 too.
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