Heat treating A-2 and D-2

Possum

Possum

Joined
Jan 27, 2000
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266
Howdy There ....!
Got a small proplem, bought a filing jig recently and plate that is the guide for running the file agaisnt isnt very hard. I try to harden it when I was told that it was A-2. Placed in furnace and took it up to 1850 for 40 mins. and then let air cool. took it back to hardness machine to check the difference and there was only two points increase, 32 to 34. I want it to be around high 50's or 60's. Think that it may be D-2 instead A-2, if so how do I heat treat d-2? I would certainlt appreciate any and all information on the subject. It is a great filing jig and I would to get it to work properly.
Thank for any help...!
Later "Possum":cool:
 
Possum,

D2 steel:

Harden at 1850 F. - soak about 15 minutes. (you can equalize at about 1475 F. for about 9 or 10 minutes before hardening but do not exceed 15 minutes on the equalize.)

Rapid air cool to about 150 F. but no less than 125 F. before immediately tempering, or at least snap tempering (do not still air cool - still air will not harden well).

Snap temper at 50 degrees less than temper temp. for 2 hours minimum

RC 60 : temper at 400 F. for 2 hours minimum

RC 58 : temper at 600 F. for 2 hours minimum

RC 56 : temper at 1000 F. for 2 hours minimum

Tempering more than once is good and you can not over temper as far as amount of temper time is concerned.

I didn't find any hardening temp's for A2 steel but the temper temp's are basically the same. I have not done A2 yet but have done D2. Some one here can give you the A2 specs if you need them.

EDIT: I found this on A2 - Preheat to 1200 and soak (this is probably for equalizing and although it does not say, I would not allow to equalize more than 15 minutes), harden at 1750 - 1800 F. for 1 hour per inch of greatest thickness. Again, as with all tool steels, do not allow to drop below 125 F. before immediately tempering or snap tempering.

Roger
 
Snap Temper:

It is a means of stabilizing and relieving stress caused by heat treat and quench and is performed prior to the first temper and typically (as I understand) done at a temperature of 25 to 50 degrees F. less than the temper temperature. It is performed only once and for a minimum of the same amount of time the temper cycle is performed.

Roger
 
1850 F is too hot for A2. Generally, the High 1700s are the limit. I do A2 at 1780, freeze overnight and temper three times at 400F for HRC 61, 500F for HRC 60. Maximum strength for A2 is in the HRC 60-61 range.
For D2, you can harden between 1800 and 1900 F. I like it at ~1875. D2 gains the most from cold treatments of the common knife steels and I do the freeze treatment immediately after quenching. Temper at 400 F for HRC 61-62. Maximum strength for D2 is At HRC 60
 
Possum: A2 Austenitizing temp is 1750F. D2 Austenitizing temp is 1850F. Soak times for both should be 40 minutes for 1/4" thickness, 30 min for 3/16". Your parts MUST be wrapped in foil or they will be ruined by decarb.
Still air cooling isn't the best for either-press quenching will yield a higher hardness and a better microstructure.
Temper once before Cryo.

RJ Martin
 
Bohler/Uddeholm reccommends A2 be hardened between 1700F and 1780F and D2 between 1810F and 1920F. The higher heat hardening gives higher hardness, while the lower temps yield tougher steel.
Freezing or cryo and the tempering also provide a lot of latitude in the process.
Using an oil quench also helps the process, as it is significantly faster than air. I also use Turco solution from K&G with these tw3o steels, avoiding time spent unwrapping from foil.
The Turco burns off at temperatures higher than 1900F though.
 
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