tempering no color

[pnumia]

I've never encountered this before. heat treated a 0-1 blade cleaned it up went to temper and have had no color show up, at all. I have not checked hardness which i will do after the next cycle. could anything be wrong?

[Doug Lester]

How are you doing your tempering? Is it in an oven or are you using a torch?

Doug

[pnumia]

in the kitchen oven 375 two hours at a time.

[Ed Caffrey]

Wow, that's odd. I know it's a dumb question, but you didn't have an element in the oven go out (assuming it's electric) ? Even if a blade isn't cleaned up well, I always see the oxide colors if the heat it there. HMMMM???

[Doug Lester]

If you have a thermomter in the oven with the knife and it's registering 375 degrees and you're not going by the setting on the dial alone then whether or not you're seeing the oxide layer the steel is tempering. Why you're not seeing the oxide layer is something I can't say. I never see the oxide layer because I never clean up the blade enough to see it.

Doug

[Ed Tipton]

pnumia...As the previous postings have already alluded to, if the heat is there, the steel would have tempered. I would clean off all scale from the blade if you have not already done so, to the point where it is bright and shiney. Doing this simply makes the temper colors easier to see, and then I would wrap it in some aluminum foil to shield it from the direct radient heat source, (either gas or electric). If you don't already have one, purchase a cheap oven thermometer ($5), rather than depend of your oven thermostat setting, and then try tempering it again. Keep adjusting the control until the oven thermometer reads what you want it to read regardless of what the control setting says. Once the temperature stabilizes, place the knife into the oven close to the thermometer. Oven controls are notorious for not maintaining correct temperature settings...which of course are critical for what we are doing.The oven thermometer should be much more accurate than the thermostat setting. Be sure to place the thermometer close to the knife because there could be temp variations within the oven itself. You should be able to clearly see the tempering color. If the color is not as dark as you would like, you can re-temper in 25 degree increments until you reach the desired temper. To do this, I would remove the knife from the oven, and then re-adjust the temp and let it stabilize at the higher setting and then try it again. For general useage, I like to temper mine at about the color of beer. Good luck.

[pnumia]

was gone to the doc all day fri.
the blade seems to have tempered ok but never did color like you would expect. it darken during the last cycle but not like it should have. i think i'm going to try to temper with whats left of the steel just to see what happens