D2

Brad Lilly

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Hopefully I'm not repeating another thread. I was looking at the knife steel reference page for D2 and the temper range is 400 - 1000 deg. I'm building a D2 blade (little over 1/8" thick on the spine, 3" long blade) and wanted to see what you guys think would be a good temperature for tempering. I don't have quench plates so I was thinking I could use my compressor to air cool the blade or should I hold out for plates?

Thanks
Brad
 
As far as tempering, that will depend on your as quenched hardness. Plates would be best but D2 is an air hardening steel so just letting it cool on a rack or hook will work. Circulating some air will help it cool quicker. For tempering, most of the time 400 will put you in the 61-62 range, 450 will be in the 60-61 range, & 500 will put you in the 59-60 range. Here is how I would do it with the equipment you've described.

1. Heat to 1200 and equalize.
2. Heat to 1450 and equalize.
3. Heat to 1875 and soak for 30 minutes.
4. Air cool.
5. Dry Ice/Alcohol bath for 30 minutes.
6. Double temper at 450 for 2 hours per cycle.

The freeze isn't necessary but may make up for any loss of hardness by skipping the plate quench. It will definitely improve the percentage of RA you convert into Martensite. Try a test blade and see how it performs. You may have to lower or raise the tempering temp. to get where you wanna be. Let me know how it works out for you.
 
I normally heat treat D2 according to the Carpenter data sheet.

Place blade in furnace at 1850
Equalize
Soak 25 minutes (30 minutes covers both)
Plate quench
Cold treatment
Temper between 400-500 depending on the hardness I'm after. I normally get 62 at 400 and 59 at 500 give or take .5


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Thanks James your method is very similar it seams Darrin has a slower ramp up to full temp. I just bought a couple feet of 1" aluminium flat bar. I figure I can check it for flatness on my granite block. If it is out too much I will dress it up in my mill. How critical is the cold treatment? I don't have any place to find liquid nitrogen or dry ice.
 
A freeze isn't necessary but helps convert a greater percentage of retained Austenite into Martensite, if you can find the stuff needed to do it. I just use a small cooler. Warren is correct, the meat dept. in your local grocery may have some and if they don't they can probably tell you where you can find some.
 
emm whats the equalizing you guys keep talking about?

I'm new to HTing btw and my main steel so far is D2
 
I think I made out fine. I don't have a rockwell tester but it is too hard to file. Thanks again guys for the info.
 
SHOKR, equalizing is when you allow the furnace and the steel to "settle" into a specified temp. Most furnaces will overshoot the target temp. by a few degrees and then slowly fall back to the desired temp. Once the furnace settles down to the proper temp. then you can hold that temp. for a few minutes to let the temp. of the steel come to the same temp. as the furnace. 5 minutes is usually enough but may vary from furnace to furnace. Blade mass also has a great deal to do with it too.

Brad, sounds like things came out good. Give it a good workout and then you can tweak things if necessary.
 
thanks Darrin

so you're saying lets say if i want to soak the blade for an hour i ought to leave it for (example) hour and 5 mins, right?
 
The equalizing referred to in many spec sheets is generally there in reference to industrial parts and processes. I believe it is largely to insure the part goes through phase changes, more or less as a unit, often somewhere around 1400F. This can be important if, for instance, the part is thick and the core is lagging behind the heat of the exterior - or similarly, if the HT is by forge or industrial oven, where the temperature may climb so fast that the workpiece lags in temperature,

For knifemakers, we are dealing with a thin part that isn't going to have much difference between the inside and outside. The electric kilns we use heat up so slowly, that the workpiece temperature is unlikely to have any meaningful difference. The blade pretty much self-equalizes as it heats.

I would suggest that with something as thin as a knife blade, in something as slow as the kilns we use, that no equalization is necessary. If you do use a short equalizing step, it probably meets the test of "do no harm".

Rob!
 
thanks! that makes sense!

I found that ppl debate leaving the bladei n from the start or waiting until oven reaches temp then putting the blade inside, not sure what differences this would create if any, but on my first(only) HT trial so far i had the piece of steel in from the start. so as you said probably no need for equalizing

Brad, sorry if I hijacked the post
 
I strongly suggest to have the oven very well equalized at the austenitization temperature before putting the blade in.
Quick to the aus temp. is way to go...then soak accordingly to your carbides condition
 
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