I've read, and re-read your post, and am not sure I fully understand what you're situation is, or exactly the question....but I'll give it a shot.....and if I'm not addressing the exact question, just let me know/clarify, and I'll give it another go!

Got a kitchen? <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' /> Then chances are you have another "tempering" oven. <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' />

For a "snap temper" I have the oven pre-heated, place the blade in, and leave it for 1 hour (any tempering operation outside of a snap temper is a 2 hour time frame for me) Then take it out, allow to cool to room temp, then do whatever is next. (About the only time I use a "snap temper" is when a blade is going into the LN tank (Liquid Nitrogen)...and that only applies to certain steel types.

Thanks ed for replying. Yes I have a kitchen. What I was meaning by another tempering oven was one with a PID controlled environment. Like a toaster oven set up with a PID controller and thermocouples. My conventional oven will temper but not knowing the exact temperature leaves me with a uneasy feeling for some reason. Someone told me that u can snap temper in the conventional oven until the evenheat oven cools down (it takes a really long time to cool down lol). I was asking if I had to leave the blade in the conventional oven "snap tempering" for the entire period waiting on the evenheat to cool, or and I take it out after an hour or so?

A critical bit of information is missing- what steel are we working with here? 350F may, or may not, be the temperature you want. A warp or crack from allowing an as-quenched blade go too long is indeed a disaster, but stabilized austenite by tempering before Mf (or M90+) is a nasty problem too. "Hand warm" is the suggestion on most higher carbon steels, and that is just a bit above room temp. Don't be so afraid of completing the cooling process that you don't fully harden the blade.

Your second post was moments before mine. Depending on the alloy, the temperature is more critical than time. If the temperature is below a specific stage and diffusional process of the temper times will get huge to make an equivalent change. Below 300F in simple carbon systems all that is happening is the relaxation of the body centered tetragonal nature of the hardened steel, so this is essentially just relaxing the strain of hardening. If a quenchant with good cooling curves is used there will be much less of added strain above and beyond what is necessary, so the will be less urgency. If the quenchant is too fast for the depth of hardening there will be added strain above what is needed for maximum hardness and the quicker you can relieve it the better. The first phase of tempering (as defined by temperature) will just be this relaxation, above 350F and the precipitation phases will begin and you will start to change the structures present. It is the accumulation of secondary carbides that results in the destabilization and possible conversion of retained austenite, this is why steels that could benefit from cold treatments are best snap tempered below these ranges, it allows for a "purer" martensitic conversion, which must then also be tempered again.

So in short, I know- too late, so long as the temperature is in the initial non-precipitation phase how long you leave it in the oven is not critical. An hour should be good.

I'm using O1 tool steel Kevin. I actually had a very bad experience last night when I was heat treating. I had 6 blades I needed to harden and I don't think I was successful. Here's what happened...

I went to your web site and tried to follow your process. Hopefully u can see where I failed.

I set the program on the evenheat to ramp and full power to 1600F and hold for 15min. I let soak for 10 min and pulled all blades out and hung on a nail to aircool to black. Put the blades back in the oven and continued to the second step of the program. Set at 1550F let them soak for 10min and pulled them out and hung them back on the nail to air cool to black again. Third step was soak for 10 min at 1500F and quenched in vegetable oil at 130F. I file tested all the blades and only one seemed to be hardened. The files bit in and removed material. I was beyond frustrated...and it was like midnight lol. What did I do wrong? I'm in the process of reheatreating now

This is my set up

Anything need to be changed?

|quoted:

Anything need to be changed?

After the initial normalization you can drop the temp on the second heat to 1500F or below. For the hardening heat do not exceed 1480F, and in fact 1475F should work quite well. Do not check with a file until the steel is cold. This is the catching point with using a file to determine quench effectiveness on O-1. Since most recommendations are to cool to hand warm with O-1 and temper immediately, you are following the recommended procedure, however quite often there with be a delay in the file skating until the hardening is fully complete.

This is not your quenchant, but one of two factors- improper austenite solution or decarburization. That many heats exposed to the atmosphere could very well give you decarb. Keep filing until you feel you have removed a good .010” and if the files still aggressively bites you need to look at your austenitizing heat.

Do u recommend taking decarb precautions with brownells atp 641

OK Mike, I'm confused. Why are you doing two normalization heats (1600*F) prior to the hardening quench?

I've read at a couple different places to lessen the temperature by 50 degrees each cycle

with that much time at temp in a oven I would think the decarb may be fooling you into thinking it may have not hardened, try grinding 10-15 thou off and check again, other wise what kevin said. I have found that to be the only down side of ovens, the high amount of decarb, that is why i got an argon purge on my new paragon. makes all the differance

I've completed the second hardening and tempering process. Hardening at 1480F and tempering 2 two hour cycles at 425F and I can take the blades and bend them and they don't come back to straight....