Programing an oven

[Smithy]

I am a new maker that is using 1084. I have a couple of ovens (left over from another life) and they are both programmable. My questions are:

1. In normalizing, can I program a routine that will allow me to take it up to 1600, stop and let it cool for 2 hrs, then take it back to 1500 and let it cool for 2 hours, and then take it up to 1200 and stop, letting the blade cool in the oven?

2. What program should I set up for hardening, the ramp and holding time till I quench?

3. Can I set up a program to temper the blades and, if so, what should it be?

4. Is it easier to use a torch and watch for color as I will only be doing 2-3 blades at a time?

As always TIA...Teddy

 

[Barry Clodfelter]

If you are talking about an automated process in number one i don't think that will happen. I believe you will want your blade to cool to at least black if not room temp before the between normalization temps. I have a rampmaster controller on an Evenheat oven and I think it could be programmed to reach the temps but I have never tried it I just bump the temp up or down manually.

2. I ramp up at 9999 to get there as quickly as possible and set the hold for like 1 hour. I will only harden up to 5 blades at one time and an hour gives plenty of time to get them all done. Then I will stop the program when I'm done.

3. Depends on your controller. But it should and should also be specific for the steel you are tempering. I have 4 programs set up with different temps for the steels I work with.

 

[timgunn1962]

I'm no knifemaker, but I've been doing some testing on my homebuilt HT ovens and the following is my take on things.

1/ The cooling rate is very likely to be much slower than would normally be the case for normalizing. Effectively, I think you'd be running annealing cycles, rather than normalizing cycles, by cooling with the oven.

2/ Probably ramp up as per the HT recipe you have chosen to follow and hold at the final Austenitizing temperature indefinitely, switching off once you've quenched the last blade and closed the oven.

3/ In most cases with simpler steels, I'd load the oven cold and ramp up to temperature slowly; perhaps an hour to reach tempering temperature. The slow ramp helps to overcome any tendency for the blade temperature to rise ahead of the oven temperature, due to radiative heating from the elements. Hold for the recommended time and switch off to cool with the oven. The temperature and time will be whatever the HT recipe you are following calls for. For multiple tempers or more complex regimes, it's very much a case of follow the recipe.

4/ Maybe, but the probability is that you'll get much tighter control with the oven, leading to much more consistent results.

You don't say what your ovens were originally intended for. If it was ceramics, be aware that you are likely to see greater short-term temperature swings than would be the case with a dedicated knifemaking oven. Typically, the controller output cycle time is around 30 seconds on a ceramics kiln, whereas a more typical value for a knife kiln would be 2 seconds. The thermal mass of the kiln loading is usually much greater for ceramics and this tends to damp out any swings. Ceramics are much less sensitive to relatively small changes in temperature anyway, so they don't need such fine temperature control. I don't think you'll notice a difference when Austenitizing, but burying the bldes in a tray of dry sand for tempering (to damp out the swings) and extending the tempering time to allow the sand/blades to reach an even temperature throughout is a good idea.