View Full Version : Rehardening ATS-34?


s mcfall
02-20-2002, 12:26 PM
ok, my test piece of ats-34 came out at 57-58 rockwell - i used 1970deg for 1hr, can one reharden or do i have to fully anneal it first? any suggestions? longer soak times?
anybody do their own heattreating of this steel that might give me their recipie?

thanks,
stan

Don Cowles
02-20-2002, 01:41 PM
Don't know how big your test piece was, Stan, but if it was an average knife blade, 1 hour is too long and could have "cooked" the steel. Ten minutes is plenty of time at temperature for a 1/8" blade, twenty max for thicker.

What did you use to test the hardness?

s mcfall
02-20-2002, 01:44 PM
a digital tester that we have here in our shop....ok...10 - 20 min. i read some instructions somewhere 1 hr...but i think that you are right....so, i cant reharden?

stan

SIGGI
02-20-2002, 01:47 PM
Ok, next question.

Why does all of the information that I have read say to preheat at 1400/1500 for 30 min and then 1950/1975 for 1 hour?

oops, two questions.

Tempering heat is also a variable that has been listed as high as 950 and down to 475 range. What are your suggestions and experiences?

Thanks,

Bob Sigmon

s mcfall
02-20-2002, 02:08 PM
i went back to the K&G catalogue and thats where i got my information from.....we should get paul bos on these forums,
then we would have it all covered:)

Don Cowles
02-20-2002, 03:11 PM
Virtually all of the instructions from the steel mills are intended for sections much thicker than knife blades, hence a longer time at temperature is suggested.

Hitachi (ATS34 manufacturer) has published such a broad range of tempering temperatures because you have some options in the finished product. Lower range= higher rust resistance. Higher range= another point of hardness. Depends on what you want.

I have talked to Paul Bos about this on a few occasions. We are singing from the same book.

If the steel is in fact "cooked," toss it and start over.

JerryO13
02-20-2002, 05:05 PM
I think most steel mill info is for a 1" square of steel. Hey but what do I know

Cactusforge
02-20-2002, 06:35 PM
I would ecko getting Mr Paul on the fourms we would all learn a LOT Gib

s mcfall
02-21-2002, 07:11 AM
Don, so 10-20min max at temp, is the preheat still the same ie:1400-1500 for 30 min or should i reduce that also, if so how long should it be? thanks for the help by the way...i am soooo glad for these forums :)

Stan

Don Cowles
02-21-2002, 07:31 AM
Stan, I do not pre-heat ATS34. I put the blades in a cold oven, ramp up to 1950-1975, hold for 10 minutes, then air quench. I temper once at 425 for 2 hours as soon as the blades are cool enough to pick up (still around 150 deg. F), cryo treat, temper again at 425, and a third time at 400.

Shotgunone
02-21-2002, 08:41 PM
Well I ain't no expert and certainly wouldn't want to argue with those here with more experience but here is what I do.

On 3/32 inch and 1/8 inch ats. Start in cold oven. Preheat to 1450 and let it soak for 30 minutes. This is to releave stress, and lessen warpage. I have tried going to harding temp and have warped the crap out of the steel. For me it seems to help going for reducing the stress. Then take it up to 1950. Let it soak for 15 -20 minutes for 3/32 and about 30 minutes for 1/8. Remove and press it in my flat jawed vise to rapid quench it below 1000 (all the glowing color is gone). Take it out of the bag and finish cooling in still air. When I can handle it with my bare hands I straighten and flatten the steel as needed. Checking my blades between two precision ground plates. Temper twice at 950 for 2 hrs each time.

You are using a foil heat treat wrap on the blades right?

s mcfall
02-22-2002, 06:51 AM
i dont need to use foil wrap..i have access to a hydrogen furnace....thanks for your all your guys help.