Plate quenching

Matt Rochester

Matt Rochester

Joined
Nov 28, 2014
Messages
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So, I finally finished my oven and got my quench plates. I have some Cpm-154 that I'm going to HT. I am not going to cryo it, just harden, plate quench, and temper(unless someone can talk me into it!) My questions are 1. Do I take one blade out, plate quench, hang to finish cooling, and then get another one? 2. If I take too long between blades, plate quenching one at a time, will I mess up the HT? 3. Do i start the whole process with room temp blades in the oven, or preheat the oven first? As you can probably tell I have no previous experience with heat treating.
 
do not skip the sub-zero soak . 4# of dry ice and acetone will take you down to minus 100 degree , I got minus 104 the 1st time .

My plates are 6" wide , I freeze them 1st and put as many blades as I can on them , usually 2. I have 2 sets of plates .
 
The reason I was going to skip it was I'm not sure where to get it. Can I store it or is it a one time thing? Whats the cost?
ONeill said:
do not skip the sub-zero soak . 4# of dry ice and acetone will take you down to minus 100 degree , I got minus 104 the 1st time .
Click to expand...
 
Dry ice is cheap. Most large grocery stores will carry it. You can't really store it so buy 3-4 lbs before you heat treat. Usually cost me about 5-7$. It will get you another 1-2 points on your hardness so it's worth it.
 
Bait stores, and industial gas companies carry it around me, buts I can be hard to find in the winter here.
 
OK, here is the HT regime for CPM-154 and most stainless steels.

Pre-heat the oven to 1400F and place foil packets in oven. ( You can place them in at 1200F if you want and let them warm up to 1400 with the oven).
Hold at 1400F for 10-15 minutes to equalize.
Ramp at 9999 ( full rate) to 1950F ( between 1900 and 2000F is the normal HT range for stainless).
Soak for 30-45 minutes.
Remove one packet at a time and place in quench plates. ( close oven door immediately after removing).
After 60 seconds, remove next packet and place in plates ( removing current packet).
If plates heat up above 200F, cool off with running water to ambient and continue pressing packets until all are done. There is no rush, as the extra oven time does the waiting blades no harm.
When all blades have been plate quenched, cut open packets and remove blades. CAUTION - the foil is hardened and can cut you bad!
Mix a gallon of denatured alcohol ( home depot paint dept.) and 5# of crushed up dry ice in a metal pan that is big enough to place the blades in. It will smoke and bubble, that is OK.
Place all blades in the pan one at a time and let them sit there for 30 minutes to an hour...or until the dry ice is all evaporated.
Remove and wash off the blades.
Temper at 400F for an hour, rinse in water to cool off, and temper blades a second hour. Rinse off to cool again and the HT is done.
This should give you a blade between Rc 60 and 62. To have a little tougher and easier to sharpen blade for rough use, temper at 450F for a hardness or 59-60.


You can do the sub-zero treatment between the tempers, but it does the most good immediately after the blades reach room temp from the plates.

Let the alcohol sit in the pan and warm up to room temp. Then pour back into the can and label HT on it. It can be used over and over again for sub-zero treatments. Leave the cap loose for a day, because it is slightly carbonated. Shake the can a bit and tighten the cap the next morning.

Cryo is done at -300F or lower, sub-zero is done at -95F. A dry ice slurry reaches about -100F.

Buy the dry ice at your local large grocery store or other supplier while the blades are in the oven or just before you start the HT. Place it in a cooler, and it will last for many hours. Once crushed into chunks and put in the alcohol, it lasts about an hour or so. Acetone will work as well, but the alcohol is safer and cheaper.

The larger the quench plates, the better they work on multiple blade batches. 4X2X16" is a minimum size.
 
Tracy has great instructions - pretty much the way I do it myself.

One thing I learned the hard way - depending on how thick your blades are - when you put the blades in dry ice slurry be SURE you have the blades laying exactly on edge vertically, OR laying perfectly flat on pan to prevent warping. I'm not sure about the CPM154, but AEB-L and 13C26 are both fairly flexible when they come out of quench plates.

1"X4"X12" work good (provided overall length is less than 12") for quench plates if you will cool them in water between blades, even run water over outside of quench plates while blade is clamped TIGHT between plates. Beauty of plates you never worry about warping during quench.

Ken H>
 
Stacy said 1 hour on each temper , I believe it should 2 hours for each temper .

And a question Stacy please , why not put the blades in at the ovens cold temp , then let ramp up and equalize at a couple of temps . Example , my oven is sitting 56 degrees , put the knives is , I ramp to 1100 degrees and let sit for 10-15 mins. then I go 1500 and let sit for another 10 mins. Then to the 1950 and soak for 40 mins.

I have had the blades tested and did hit my desired range but so many talk about putting them in a preheated oven , so I wonder what I may be missing ?

Thanks for you time Stacy .

Jack ONeill
 
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So is the subzero soak just to get another point or two hardness, or are there other benefits? I'm making a gyuto for a chef to try out and give me feedback on design and performance. Is 61-62 RC going to be hard to sharpen, or would 59-60 be better?
 
In knife blade thicknesses, all buy a rare few very high alloy steels need more than one hour and more than two tempers.

The below 1000F range on heat up is the most likely area to have severe temperature swings between the reading and the actual. Once the refractory is soaked above 1000F it is more even in heating. That is why you don't start with a cold oven filled with the steel and slowly heat up.


Sub-zero reaches Mf.....that is all. It gets the steel fully hardened.
Cryo reaches the range of carbide conversion, and gives more hardness and toughness due to the carbide types.

Rc59-60 vs Rc60-62 is a matter of what you want or need. I like the upper numbers for kitchen and fillet blades, and the lower for camp and hunting blades.
 
So, at 60-62 will it be hard to sharpen? Is hardness the main factor in how hard a blade is to sharpen?
Stacy E. Apelt - Bladesmith said:
In knife blade thicknesses, all buy a rare few very high alloy steels need more than one hour and more than two tempers.

The below 1000F range on heat up is the most likely area to have severe temperature swings between the reading and the actual. Once the refractory is soaked above 1000F it is more even in heating. That is why you don't start with a cold oven filled with the steel and slowly heat up.


Sub-zero reaches Mf.....that is all. It gets the steel fully hardened.
Cryo reaches the range of carbide conversion, and gives more hardness and toughness due to the carbide types.

Rc59-60 vs Rc60-62 is a matter of what you want or need. I like the upper numbers for kitchen and fillet blades, and the lower for camp and hunting blades.
Click to expand...
 
Sharpening difficulty increases as hardness goes up. The other thing that creates sharpening difficulty is carbide type and size. Cryo and gaining a few points in hardness will thus make a blade harder to sharpen. That does not mean it is going to be impossible to sharpen, just that it will require better abrasives and skills. In the old days of Rc 52-54 carbon steel knives, and rock on the ground was a good sharpening stone, and your boots were all the strop you needed. With todays engineered steels and other alloys, workable harnesses exist up to Rc 67. A lot of high end Japanese sashimi blades are Rc 62-64.
 
Stacy, or those able to answer

What does the equalize step do? When I looked at it on a heat treat regimen I assumed it was for industrial heat treating uses where there is different thicknesses and shapes and you needed to make sure everything is heating evenly. Or does "equalize" refer to something else?
 
jobasha11 said:
Stacy, or those able to answer

What does the equalize step do? When I looked at it on a heat treat regimen I assumed it was for industrial heat treating uses where there is different thicknesses and shapes and you needed to make sure everything is heating evenly. Or does "equalize" refer to something else?
Click to expand...

It is just to let every thing equal out in temperature , the steel and oven at the same temps.
 
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