Heat treating and plate quenching ?'s

jbblount

jbblount

Joined
Aug 15, 2010
Messages
273
I'm ready to try out this oven I built. I've found a few different ways to heat treat 440c. But if you want I would like to hear how you do it.

I've also read that the blade can warp. Please tell me how to avoid this. I've ground the blade and left .040" at the edge.

I ordered alluminum plates from USAknifemarkersupply for plate quenching. I also got some heat treat foil from them too.

Any help will be appreciated. I really don't want to screw this up this close to finishing the knife.

Thank Brad.
 
Depends on who you talk to. Use a recognized acceptable heat treat recipe. A tip that helped me was to put my aluminum plates in the freezer overnight prior to heat treating, then, when quenching between the plates, use compressed air to blow between the plates.

Warping shouldn't be a problem if the blade was straight to start with and you ground both sides fairly evenly.

Tear yourself a piece of paper towel about 1/4" X 1/4" and put inside your foil pouch prior to sealing it. Use double folds when sealing your pouch.

.040 is a fairly thick edge for 440C. You may discover that grinding to the final thickness is not as easy as you think. Remember, keep everything cool as you grind.

Cryo if possible (not totally necessary, but will assist in getting the most from your steel).

I'm sure others will chime in and shoot my theory to "snotz", but maybe some of this will help.

Robert
 
Robert Dark said:
Depends on who you talk to. Use a recognized acceptable heat treat recipe. A tip that helped me was to put my aluminum plates in the freezer overnight prior to heat treating, then, when quenching between the plates, use compressed air to blow between the plates.

Warping shouldn't be a problem if the blade was straight to start with and you ground both sides fairly evenly.

Tear yourself a piece of paper towel about 1/4" X 1/4" and put inside your foil pouch prior to sealing it. Use double folds when sealing your pouch.

.040 is a fairly thick edge for 440C. You may discover that grinding to the final thickness is not as easy as you think. Remember, keep everything cool as you grind.

Cryo if possible (not totally necessary, but will assist in getting the most from your steel).

I'm sure others will chime in and shoot my theory to "snotz", but maybe some of this will help.

Robert
Click to expand...


Thanks for the reply. So you think I should grind it down to about .020 before heat treating? I thought leaving it thick might help keep it from warping.
 
Place heavy weight on the plates while you are quenching. That is a good way to prevent warping
 
Clean and wrap in HT foil.
Place in 1000F oven and allow to equalize - about 15 minutes
Ramp to 1400F at 1000F/Hr and soak for 15 minutes,
Ramp to 1900F at 9999F/Hr , and soak for 30 minutes.
Remove and plate quench in the foil. Keep clamped for at least 10 minutes.
Remove from foil, snap temper at 300F for 30 minutes.
Do a sub-zero or cryo quench, and then temper for 2 hours at 400-450F.
Cool to room temp, and repeat temper cycle.
 
Thanks Jsteele.



bladsmth said:
Clean and wrap in HT foil.
Place in 1000F oven and allow to equalize - about 15 minutes
Ramp to 1400F at 1000F/Hr and soak for 15 minutes,
Ramp to 1900F at 9999F/Hr , and soak for 30 minutes.
Remove and plate quench in the foil. Keep clamped for at least 10 minutes.
Remove from foil, snap temper at 300F for 30 minutes.
Do a sub-zero or cryo quench, and then temper for 2 hours at 400-450F.
Cool to room temp, and repeat temper cycle.
Click to expand...

Thank you Bladsmth. I dont think I'm going to be able to cryo quench yet. It'll still be good without it right?
 
With a sub-zero treatment (dry ice) at -105°F, it is actually just the bottom of the quench. It does not gain anything from staying at that temp for more than long enough to equalize ( become completely at temperature). Fifteen to thirty minutes is plenty long enough. Overnight won't do any more, but you sort of hate to waste the dry ice, so most of us leave it there until the dry ice is gone.
All that happens at that temperature is the conversion of any retained austenite.
In a cryo treatment, at below -300°F, a soak of several hours is beneficial because the carbides change structure, which is a slower process.
 
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