What's time and temperature for A2 Tool Steel?

Leu Custom

Leu Custom

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Jun 2, 2007
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For all you guys out there who use A2 tool steel, What temperature do you guys use for a first, second and perhaps a 3rd temper to yield a hardness of 60 RC? I'd be austenizing the knife at 1800 degrees.

If someone has a excellent recipe for getting a nice hard tough blade for A2, I would appreciate it very much. Thank you!
 
When austenitized at 1800F you will get a Rc60 with a 450 temper. Unless you can test the Rc after each temper, all three should be at 450. However, many makers make the first tempers about 25 degrees lower than the last one, just to play it safe.

Preheat to 1450F and hold for 10 min. Raise to 1800F and soak for 20 min. Air cool in rapid air or plate quench. Cool to 120F. Temper immediately (at 200F if you are doing a cryo, or 425F if no cryo). Cool to room temp and re-temper two more times at 450F for a total of three tempers.
Stacy
 
bladsmth,

That was about the most easily understood recipe i have ever come across! Dumb question, if I austenize at 1725 or even 1750 or 1775, what tempering temperatures would i need to do?

Should something at RC60 chip out rather than fold over say trying to cut a piece of brass rod?

Thanks!

Pohan

PS. I have heard that you can actually austenize A2 hotter than 1800 degrees...is this true?
 
So does it matter the thickness of the blade being soaked at 1800 degrees for 20 minutes or not? I use 1/16" up to 3/8" thick. Thanks!
 
Leu Custom said:
So does it matter the thickness of the blade being soaked at 1800 degrees for 20 minutes or not? I use 1/16" up to 3/8" thick. Thanks!
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I would err on the long side for soak times. That is 20 minutes once the blade has reached temperature. Nothing very bad happens if it soaks for 40 minutes, but it is bad if it only soaks for five. Not the case for simple 10xx steels, but complex steels have a lot of elements that need to dissolve which require time.
 
The Rc for 1700, 1750, and 1800 are close to the same when tempered at 450. 1700 and 1750 may be about half a point lower (at most). 1800 will be closer to Rc61 on the first temper.
Do not exceed 1800. The range is 1700 to 1800.
All soak times start when the temperature in the oven has rebounded (returned or reached the set temp).20 minutes for an A-2 blade is plenty, but as Nathan said - that is twenty minutes AT 1800. With a ramp from 1450, the time starts once the oven reaches 1800. The blade will always be the oven temp (for practical purposes) during a ramp up.


Clarification requested on the pre-heat:
The pre-heat to 1450 is easiest done by putting the blade in the cool oven and ramping at a reasonable rate, say 100 to 1450 in one hour. It should not kill the blade to put it in a 1450 oven, but the slower and less shocking ramp will be better. The ramp to 1800 should be at the ovens normal rate.

Stacy
 
I have heard from Phill Hartsfield that he takes his blades above 1800 degrees. as to how much above, I don't know, but definitely above 1800'F.
 
mete: no i have never plate quenched my blades. I just make sure they are straight before I hang them up to air quench. Seems like you'd need a few vises or presses or something to do several blades at once of various sizes and lengths. Perhaps I can try it next time I do some blades with the info that bladsmth gave me. Thanks to you all.
 
No need for a vice or such to plate quench. Simply procure two aluminum plates of enough thickness and rectangle for the job. Sandwich your blade and stand upon the top plate, with shoe on. Does not take very long. It is fun to listen to the foil wrap make those snap, crackle and pop sounds. I was a long time comer to plate quenching but after trying it only a couple times am hooked on it for deep hardening steels. No need to check for straightness before plate quenching. No need to remove from packet before plate quenching. About 3/4 inch thick plates should be just fine for our purposes. I, as many know, prefer to HT only one blade at a time. I recommend that but ......

Oh, just a bit off subject, thanks for being the slowest knife maker ever. Makes feel a little better about myself. I was thinking I was the slowest.

rlinger
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This is a question I've been meaning to ask for a while: Everyone says to end the plate quench when the blades reach about 120 degrees. How long does this take?

I don't know how I'd go about actually taking the temperature of a blade in a foil envelope in between two large plates that I'm standing on :eek:
 
that would depend on how thick the blades is! 1/8 blades cool down WAAAAAAAAAAAAAY faster than say 1/4 thick stuff!
 
bladsmth: dumb question, how long should each temper at 450 degrees be for? 1st, 2nd and even 3rd?

thanks!
 
Leu Custom said:
that would depend on how thick the blades is! 1/8 blades cool down WAAAAAAAAAAAAAY faster than say 1/4 thick stuff!
Click to expand...

Yeah, I should have mentioned that :o

I'm current working on 1/8, 3/32 and 1/16 blades (no I'm not going to HT them all at once). I'd appreciate anyone's estimates for thicknesses they work with though -- everything I've done to date has been O1 with PBC and oil so I have nothing to go on.
 
bladsmth: Thanks! All along I've been doing 3 tempers at 2 hours each! Freaking drew my blade down to the hardness of a banana! Though I never exceeded 400 degrees for any of the tempers, wonder why it isn't hard as it should be?
 
i'd suggest instead of standing on it, put like 2 cinder blocks on it. Otherwise you'll be standing there for 5-10+ minutes depending on how thick the blades are.
 
All of the tool steel manufacturers that I know of stipulate a minimum of 2 tempers of at least 2 hours each for A2.

The one time I took A2 above 1800°F the blades did not harden properly and I had to redo them.
 
Steve - for larger items, 2 hours would be recommended. For these thin blades, one hour minimum, two hour max. I usually temper two hours.

Leu Custom - Triple tempering is not really needed for A-2 blades. If you did three at 400F you should not have significantly lowered the Rc. I suspect that the HT went awry somewhere. Next time do a Rc before and after the tempers.

Stacy
 
I don't have an RC tester! ARGGH. What does a good one cost these days? and do they all weigh a ton ? I want to seriously look into one as it will help me refine by blademaking!

Thanks!
 
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