air quench / warping

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oconeedan

Joined
May 23, 2009
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I am having a problem with warping. I am using ATS-34, I know that you are supposed to use thick alum. plates to air quench after pulling them out of the oven, I don't have any.
I am using 1/4" steel bars between cement blocks.
I am also putting 3 blades into foil pouch, to save on foil and keep them from getting scaly.
Today, 2 out of the 3 in the pack warped.
I put them in vise and heated dull red with mapp gas torch, and straightened them.
Questions:
1)now that they are straight, do I need to re heat treat in the oven before tempering? (I am guessing I do)
2)Do I need the thick aluminum plates or can they be steel?
3)Do I need to put one blade per foil envelope, and quench one at a time?

Thanks in advance, for your help.

Dan
 
Im guessing the two outside blades are the ones that warped. Im not sure if it matters whether you use aluminum or steel blocks. What happens when packing multiple blades is the ones on the outside will begin to cool faster than the inside and warpage is bound to happen.Yes you do need to re heattreat, I don't think it matters on the plates as long as they are flat, and yes one blade per envelope. Be conservative with your wrap but don't be cheap. It will cost you more in the long run.
 
Sometimes plate quenching itself causes the blade to warp depending on how you ground the blade out and how thin it is.

on top of warping in the usual manner the blade can also warp from left to right or right to left when it's being sandwiched between the plates.

Personally, I say, cut the foil packet open, check for straightness and just hang the blade up to air cool. Try doing this with your garage door closed ! Any breeze coming from one side will also cause the blade to warp.
 
Thank you for the replys so far. Hmm, should have mentioned they warped from one side to other, I didn't know there was any other way.

I used to not grind at all until after heat treated, thought it would be easier to grind most of the way first while it was still annealed. And easier on belts.

Maybe I ought to go back and not grind until afterwards. And do as JBS Toolmaker says, and individually wrap.

Thanks for your help.

Any more suggestions are welcomed. Dan
 
oconeedan said:
Thank you for the replys so far. Hmm, should have mentioned they warped from one side to other, I didn't know there was any other way.

I used to not grind at all until after heat treated, thought it would be easier to grind most of the way first while it was still annealed. And easier on belts.

Maybe I ought to go back and not grind until afterwards. And do as JBS Toolmaker says, and individually wrap.

Thanks for your help.

Any more suggestions are welcomed. Dan
Click to expand...

Normally a blade warps from side to side when it's sitting on it's belly or spine, but I have seen blades warp from left to right and vice versa when the blade is laying flat ! :eek:
 
JBS TOOLMAKER said:
I have also heard of people keeping there plates in the freezer and taking them out right before use. Have you tried this?
Click to expand...

My first thought would be that steel coming out of the kiln at 1950/2000 degrees and put between 0/32 degrees aluminum plates would introduce a lot of thermal shock.
Kind of like brine quenching O-1. some folks mite be able to pull it off.
But Aluminum dissipates cooled fast to.:confused:
 
JBS TOOLMAKER said:
I have also heard of people keeping there plates in the freezer and taking them out right before use. Have you tried this?
Click to expand...

I have done this ! Causes some major crazy warping if the blades are thin and if the blade is ground chisel grind for instance ! Works better with thicker blades I gotta say. Either way, kinda too violent of a quench if you ask me these days ! Quenches REAL REAL fast.

Has never caused any visible cracks on the surface of the A2 I heat treated though. Just warping ! (which can be straightened out easily), but almost somewhat defeats the purpose of plate quenching !
 
bikermikearchery said:
My first thought would be that steel coming out of the kiln at 1950/2000 degrees and put between 0/32 degrees aluminum plates would introduce a lot of thermal shock.
Kind of like brine quenching O-1. some folks mite be able to pull it off.
But Aluminum dissipates cooled fast to.:confused:
Click to expand...

This is what I thought. I can see it possibly with ats-34 since it can be oil quenched. But I have heard of people doing it on D-2 and A-2 seems a bit fast.
 
I use thick copper bars(because I have them) instead of aluminum. I always put the bars in the freezer several hours prior to HTing. Have never had any warping issues, and copper dissipates heat much faster than Al. Just my experience though, and fwiw the only SS I HT is CPM 154....
Matt Doyle
 
I clamp mine between aluminum plates for a bit then take them out and wearing gloves straighten while they are still hot. Have even straightened a big one that had fell over and was badly warped by placing it on a piece of aluminum and tapping with a brass hammer. Always have options ready.
 
I plate with the very handle-end of the packet sticking out from the plates. This allows me to snip the packet once all color is gone and use pliers to grab the butt of the blade and pull it out to check for straightness while still hot before replating.

--nathan
 
bikermikearchery said:
Aluminum dissipates heat much faster than steel.
Click to expand...

Well yes and no. Aluminum conducts heat 3X faster, but is also has about 1/3rd the thermal mass (heat capacity), meaning it heats up faster while absorbing heat. Since a major factor in quench speed is the delta t, the ability of the steel plate to absorb more heat per amount temperature rise probably somewhat reduces the apparent performance advantage of aluminum. Aluminum is faster, but not as much as you might think. Steel works fine in most applications (though perhaps not this one).

If you want really fast quench plates, 110 copper would be ideal. High conduction and high thermal mass.

Surface area of contact is just as important in heat conduction. Smooth flat plates that contact the blade well is important, as is keeping the plates flat to the blade (no rocking - I like to use left over drops in the corners to keep things flat). BTW, a lot of extrusions are not very flat if you look at them.

Plates cool faster than air - so any air quench steel will quench okay in any plate material. Borderline oil quench steel like ATS 34 may justify using aluminum over steel and paying careful attention to your contact surface area. Especially when you consider the effect of quench speed on free chromium.
 
We have been freezing our aluminum plates in order to quench 3V and M4. We havent noticed any problems at all, but we do the grinding after we heat treat the blanks. We could not get the hardness we were looking for in the CPM 3V until we tried freezing the plates. On the CPM 3V if we use room temperature aluminum it comes out from between the plates at 58 RC.

We have aluminum plates that are 2X6X18 and steel plates that are 1X6X18. On CPM S30V and CPM M4 we don't notice any difference between the two types of plates and use them interchangeably. Haven't tried frozen steel plates yet but it is coming. On the frozen aluminum plates you can quench three or four blades one right after another and the plates will still be cold. Two blades on room temperature steel and the plates will be hot.
 
Hmathews said:
We have been freezing our aluminum plates in order to quench 3V and M4. We havent noticed any problems at all, but we do the grinding after we heat treat the blanks.
Click to expand...

Man that has got to be a BLAST w/M4!:eek:
Matt Doyle
 
Matt it comes out flat, but it isn't much fun to grind and polish. Charlie just finished a hunter out of M4 and he was using a diamond stone to polish it. It worked pretty well.
 
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