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Oops...blade warp during heat-treat
- Thread starter Burchtree
- Start date
I presume you mean what you wrote - "the blade" - not tang??
I am real sorry because I know how sick it is after all that work. To the best of my limited knowledge - - you are screwed, except for straightening with a hand held propane torch and re-heat treating.
The experienced knife makers will chime in and have good advise for both us. I too am interested. I just don't know how to get it back to 'true' straight again.
I will say this: getting it out of the heat and into the quench requires gentle speed while not letting gravity bend the steel. Also how you quench can warp the steel. I could go on about that but won't now.
rl
I am real sorry because I know how sick it is after all that work. To the best of my limited knowledge - - you are screwed, except for straightening with a hand held propane torch and re-heat treating.
The experienced knife makers will chime in and have good advise for both us. I too am interested. I just don't know how to get it back to 'true' straight again.
I will say this: getting it out of the heat and into the quench requires gentle speed while not letting gravity bend the steel. Also how you quench can warp the steel. I could go on about that but won't now.
rl
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- Aug 12, 2002
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- 2,259
There are ways of straightening, which I'm sure someone else will chime in with.
My question would be as to whether or not you had normalizing cycles before the heat treat. That's one of best steps to help reduce chances of warping. Or so I've been told anwyays, and haven't had any blades noticably warped yet(caliper and perfect straight edge may show different, but nothing I've noticed, and nothing that's shown up compared to scales flattend on disc sander.
My question would be as to whether or not you had normalizing cycles before the heat treat. That's one of best steps to help reduce chances of warping. Or so I've been told anwyays, and haven't had any blades noticably warped yet(caliper and perfect straight edge may show different, but nothing I've noticed, and nothing that's shown up compared to scales flattend on disc sander.
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- Nov 24, 1999
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By this point there isn't much you can do besides anneal, straighten, normalize, and re heat treat.
If you do a search of this forum on warped blades, you should come up with some threads with some things you can do.
There is a method of using 3 peices of pin stock or dowel rod in a vice to take out bends, I think it is usually done right after quenching though, so its probably too late to try it now. I haven't been brave enough to try it.
Make sure when you quench that you drop the blade in point first and hold it straight up and down. Don't make any lateral motion.
If your edge quenching you want to make sure the blade is still straight up and down so that the axis from blade to spine is perpendicular to the oil.
If you do a search of this forum on warped blades, you should come up with some threads with some things you can do.
There is a method of using 3 peices of pin stock or dowel rod in a vice to take out bends, I think it is usually done right after quenching though, so its probably too late to try it now. I haven't been brave enough to try it.
Make sure when you quench that you drop the blade in point first and hold it straight up and down. Don't make any lateral motion.
If your edge quenching you want to make sure the blade is still straight up and down so that the axis from blade to spine is perpendicular to the oil.
Not to be augumentative since I probably am the one of lessor experience but presuming he started with annealed O1 and the fact that it is O1 means, doesn't it, that it should not be normalized after anneal??? I might suggest an equalize session before reaching 1475 F. but then he most probably was using a forge or similar source for HT. That might make it difficult to equalize.
As for quenching, I have been running mine in a cutting motion in the oil, however (was it Mike - edit: no, it was Matt) lifting up and down in the oil, so long as there is sufficient depth, makes good sence to me because it is obviuos there would be less chance for lateral movement.
rl
As for quenching, I have been running mine in a cutting motion in the oil, however (was it Mike - edit: no, it was Matt) lifting up and down in the oil, so long as there is sufficient depth, makes good sence to me because it is obviuos there would be less chance for lateral movement.
rl
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- Mar 15, 2002
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- 5,368
I guess a little more information is needed. I checked the older threads, but I'm not sure what the dowel thing is used to "unwarp" blades. I differentially heated it with an edge quench. The blade is about 9 inches long. The weird thing is that the blade didn't warp left or right, if you turn the edge toward you it makes a elongated "S" shape. It's just on the edge though, it doesn't carry on into the spine.
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- Jul 21, 2001
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That is an interesting kind of warp. It may indicate the grain grew, making the edge longer, the extra length had to go somewhere so it made an s curve. I have heard of it in heavy testing, chopping kind of stuff after extended hits, but niver seen it. I would suggest simply grinding her straight if it is possible to keep enough hard for a blade. Our multiple quench 52100 blades get shorter in the edge as the grain gets finer. You have seen something that is rare, enjoy the experience, keep it in mind and someday you may have an answer.
If a blade is going to break straightening it, you are better off to have it break at that time rather than when you need it.
If a blade is going to break straightening it, you are better off to have it break at that time rather than when you need it.
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I won't be able to grind it out, it's a pretty wide side-to-side "s." The warp is on the swell (it's a recurve) so I'd lose some of my swell if I ground it out. I guess I'll either anneal and do over, or temper it and vise it between two blocks. If it doesn't work, then I'll have an even short knife. 
Ain't it fun?
Ain't it fun?
Here's another beginner chiming in 
Maybe a hot spot on the blade?
What are you using for heating? Someone here recommended placing a pipe in the forge to get a more even heat.
I bought a 12" piece of 2" black pipe. I had to fiddle around with it's placement in the forge (raised it up on chips of firebrick, adjusted the flame to hit about 3/8ths of the way from the front, ...)
In any case that is working MUCH better. It heats up the steel more slowly and evenly - I don't get bright spots on the blade. Also I know the temp in the forge (sort of) by the color of the pipe.
FFT,
Steve
Maybe a hot spot on the blade?
What are you using for heating? Someone here recommended placing a pipe in the forge to get a more even heat.
I bought a 12" piece of 2" black pipe. I had to fiddle around with it's placement in the forge (raised it up on chips of firebrick, adjusted the flame to hit about 3/8ths of the way from the front, ...)
In any case that is working MUCH better. It heats up the steel more slowly and evenly - I don't get bright spots on the blade. Also I know the temp in the forge (sort of) by the color of the pipe.
FFT,
Steve
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- Nov 24, 1999
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- 4,981
Ahhh...That kind of warp, I've done that one myself too! I did it by overheating the blade in that spot. The warp actually started to show up as I was heating it (with a torch and fire bricks)and was really bad after quenching. I had the edge a little too thin in that spot but it was mostly caused by the torch being focused on that particular spot.
Wasn't anything to do but grind it out. Knife is ugly as hell, but its kind of nice really. I keep it on the work bench and beat the living heck out of it everyday, don't feel bad at all either
There is a harline fracture right at the edge where the warp was in front of the bolster. It doesn't seem to effect it much.I'm certain it would fail one of Ed's flex tests. I used it to cut some 4"pvc pipe the other day (not corrogated, white ground pipe)and all sorts of other abusive stuff.
I think you'll just have to make this one a beater/test knife.
You'll want to look over how you heat your blades too. Make sure your not concentrating the heat on any one spot any more than absolutely necessary, and try to have the spine closer to the flame than the cutting edge if you can.
Wasn't anything to do but grind it out. Knife is ugly as hell, but its kind of nice really. I keep it on the work bench and beat the living heck out of it everyday, don't feel bad at all either
There is a harline fracture right at the edge where the warp was in front of the bolster. It doesn't seem to effect it much.I'm certain it would fail one of Ed's flex tests. I used it to cut some 4"pvc pipe the other day (not corrogated, white ground pipe)and all sorts of other abusive stuff.I think you'll just have to make this one a beater/test knife.
You'll want to look over how you heat your blades too. Make sure your not concentrating the heat on any one spot any more than absolutely necessary, and try to have the spine closer to the flame than the cutting edge if you can.
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I like the pipe idea. Right now I've got about 20 firebricks set up in a tall retangular fashion. It's heated by a fishcooker burner that resides at the bottom. It seems to get consistent heat, and it worked on the first heat-treat, but something just got fowled this time. I might try that pipe idea if this doesn't work after it's annealed and fixed.
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I'm new to this forum but as a metallurgist maybe I can add some info. There was a comment about normalizing after annealing -- they achieve about the same thing -so do one or the other ,not both. - There is also a practice by some to normalize two or three times. If it is properly normalized there is no need to do it more than once. In hardening - The knife should be supported uniformly in the furnace so that it doesn't sag. The quench should be done point down.
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I took a chance last week and decided to temper the unfinished blade and see if I couldn't smooth out the "wrinkles." Well, I couldn't.
Heard a snap and gave it two hairline cracks. I drew a blue line to show the two cracks. I've already taken it off, and am now making a slightly smaller knife.
BTW -- I edge quench, so I can't do the tip-down quench.
Heard a snap and gave it two hairline cracks. I drew a blue line to show the two cracks. I've already taken it off, and am now making a slightly smaller knife.
BTW -- I edge quench, so I can't do the tip-down quench.
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Originally posted by Burchtree
I took a chance last week and decided to temper the unfinished blade and see if I couldn't smooth out the "wrinkles." Well, I couldn't.
Heard a snap and gave it two hairline cracks. I drew a blue line to show the two cracks. I've already taken it off, and am now making a slightly smaller knife.
BTW -- I edge quench, so I can't do the tip-down quench.
One side effect transformation of austentite to martensite is a increase in volume over that of austentite and pearlite. This phenomenon is primarily what gives the Japanese clay coated, successively/repeatedly interupted single quench swords their curvature.
I think this is what caused the crack. My theory is dependent on if I am reading that picture right, and that wavy line is the hardening line. Because of the depth of the hardened area, the expansion stresses from the quench, normally adsorbed in an edge quench by the softer crystalline forms, had nowhere to go, and resulted in a "buckling". The later temper did not soften it enough, resulting in the cracking when you tried to straighten it.
Did you temper after the quench, or did you wait until before you tried to straighten it?
Where was the "middle" and "sides" of the S? I am guessing that the cracks ocurred was where the curve was changing it's direction.
As far as this occuring in blades during heavy test chopping:
In a blade with retained austentite, something similar could happen as a result of work hardening, which causes a transformation to martensite.
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Unfortunately, I didn't try to correct the warp until the next day. I tempered it, then tried to smooth out the "S" curvature. That's when the crack occurred. The "S" was right at the swell where the crack was, but it only extended up to the top of the hardened steel. Anyway, I've been seeking the advice of Mr. Buxton, and am ready to start round two of the newly-shortened street fighter.