warpage on thin 440C

J

JDW

Well-Known Member
I have 2 fillet knives to make, these will be 4th and 5th fillet knives for me, the last 2 gave me some problems warping in the heat treat, that I done after grinding the bevels, one was bad and had to be remade, the other one was very slight, so I thought this time that I would grind after heat treating, after getting both ready to HT, I done only one to see what would happen, yep it warped pretty bad. So I hope to straighten it with the clamp past straight and temper another cycle trick that I have read about. But how can I keep these 1/16" thick blades from warping? They are 440C, and I plate quench. When I removed the foil from the blade, I could straighten it and watch it slowly go back to the same curve, so I over straightened it, and the same thing, by then it was to cold to do again. Any suggestions would be appreciated.
Dale
 
First question is are your quench plates flat,check them with a straight edge,they could be causing your warp.
During your HT do you soak at 1200 deg for 15-20 minuets and at austinizing temp for 30 or more.
Leave them between the plates until room temp. Just a few ideas.
Stan
 
Thanks Stan for the reply. Yes my plates are flat, and I preheat to 1200, hold for 15 minutes, and raise to 1880 and hold for 30 minutes, but I do remove the blades from the plates before they are room temp, I try to catch that stage when they are some what buttery to straighten any warp, but this time it just slowly went back to the same bow that it had when it was removed from the foil pack. The only time that I have had warpage is on this 1/16" thick 440C. There is another thing that I noticed last night, the blade tip is carburized about 3/4" back, and I found a tiny pin hole in the foil at the blade tip, do you think that could cause the warpage? I know it caused the decarb, but don't know about the warpage. This blade will end up in my kitchen knives even if I get it straight, due to the decarb on the point, regrind it a little shorter and use her for slicing venison back strap, been wanting to make another one for myself anyway.
Thanks again.
Dale
 
I don't think the hole had any thing to do with the warpage,More than likely it's uneven cooling.with 1/16" stock I leave it between the plates till completely cool.
Stan
 
Stan, I thought the same thing about the hole. I treated the second blade today, and left it between the plates untill it was cool, with the same results, exactly the same, the bend is the same direction, and about the same amount, I am about to pull my hair out. I have one more to try, this time while profiling and ginding the scale off, I did not let it get hot, ground a little and cool it off, that is the last thing that I know to try, maybe stress from profiling is the cause.
Thanks for the help.
Dale
 
What type of plates are you using? Are they the same size? How are they set up?

I've not done any time of plate quenching before, but I wonder if on plate is drawing heat out faster than the other plate and causing an uneven cooling effect?
 
I am cooling my blades for at least 45 min and that has worked fine with AEB-L, CPM154CM and 440C. I had the same problem until i leaved them in 45 min betven the blocks.

Seved
 
If you grind bevels how does one get the knife to make uniform contact with cooling blocks? It would have to be at the same time and with the same amount of contact to prevent problems, unless I just don't understand.

In any case I have been oil quenching 440C.


ernie
 
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ARCustoms. You may be on to something, it just hit me thinking about your post. My bottom plate lays on a bench, and I place a fan blowing across them, the top plate may be cooling faster than the bottom one, that could explain every blade warping exactly the same. My plates are 1 inch aluminum, exactly the same size, they are set up laying flat, I place the blade still in the foil pack, on the bottom plate, spine down and then lay it over flat and slap the top plate on and clamp tight, the last one was left in place till it was cool, maybe 3 minutes. Ernie. On these thin blades, I have not been grinding any bevels, they are totaly flat against the plates. Seved, I have had no problems with 1/8" and thicker A2, D2, 440C just leaving them in for a minute or so, I like to get blades down to around 120 degrees then into the temper oven before they cool past that, but these I have been letting get room temp before removing. I may try leaving them between the plates longer on the next one.
Thanks to all for your responces, and thoughts. I have got to figure this out, it is driving me crazy.
Dale
 
Well, just an update, I suspended my quench plates 6 inches above the bench top, to allow free air flow around them from my fan, and still have the neatest little curve in the blade, a friend told me I was making left handed fillet knives, not to change a thing, unless I wanted a right hander. Theres one in every crowd!
I think that when I lay my foil pack on the bottom plate, that in the few seconds that it takes me to get the top plate in place, and clamped, it has already cooled unevenly enough to cause the warp. How can this be eliminated? Any other ideas would be appreciated. I wonder what an oil quench on 1/16" 440C would do for warpage? Anybody doing that on the thin stuff? Or maybe just still air, no plates?
Thanks to all for the input, and advice.
Dale
 
Dale
Try it with out clamping them.I don't clamp my quench plates,but they are 12X12X1-1/2" aluminum.Place the blade down and set the top plate and just hold hand pressure on the top plate for about 2 minuets.You got me scratching my head also.
Stan
 
My first thought would be internal stress in the steel from the steel mill.

I mostly do carbon steels and I run into this problem a lot with 3/32" 1095. I would have the same problem as you...it would consistently warp the same direction when cut from the same sheet. Sometimes it would even start warping before heat treating, when I am grinding the bevels.

What I did was start normalizing the steel prior to grinding and heat treating. Simply doing 1-2 normalizing cycles eliminated the problem for me.

Perhaps give that a try and see if it helps.

Also keep a record of exactly what you are doing. For example when you are cutting the blank out of the pieces of steel are you having the edge face the same direction each time? If so then if its internal stress it should warp it the same direction. If you cut one blade out and the edge faces to the left, then the next blade the edge faces to the right...they should warp opposite directions if its from stress in the steel. Same thing with your quench plates. Pay attention to which plate is on which side of the knife and which side of the knife is put down on the quench plate first, etc. Then you'll know if one of the quench plates is causing a problem, or you laying the knife down and one side cooling before you can get the 2nd plate on top. That way you can rule it out one at a time.

Good luck! These things can frustrate the heck out of ya.
 
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