electric furnace questions

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Sep 11, 2005
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Is it necessary to have 2 ovens when heattreating a blade, one for hardening and one for tempering? Ive read that steel should be tempered as soon as the temperature reaches room temp or a little higher, is this an absolute must or can you wait with the tempering a few minutes until the oven cools down. how long does it take for lets say an Evenheat oven to cool down (to tempering temps) if you just open it and turn it off? (a matter of minutes or seconds?)

Is it possible to use the same oven to do both tasks? The ovens are expensive does everybody here have 2 :confused:
 
i do my tempering the next day cooling the evenheat from 2050 just takes to long + cpm3v calles for 3 tempers at 1000 2 hours each
that makes for a long day
maybe im just lucky that i havent cracked anything yet
 
butcher_block said:
i do my tempering the next day cooling the evenheat from 2050 just takes to long + cpm3v calles for 3 tempers at 1000 2 hours each
that makes for a long day
maybe im just lucky that i havent cracked anything yet

I think that the CPM steels are generally more stable at full hard than some of the high carbon content non-stainless steels. I've heard that 1095 can crack just sitting around waiting to be tempered, but I've never seen it happen. Mind you, I've only seen a large handful of blades made from 1095 go through the process, and tempering was usually within an hour or so of quench.

-d
 
On somewhat related note, PID controllers have a "calibration" setting
when it drives the spiral and learns it's thermal characteristics, at different
temperatures.

In my home made oven I don't ever see the temp over/undershoot the
preset by more that 2-3F, all the way up to 1900F.

You can drive the temp up as agressively as you can with "full current on"
mode - only start slowing down when you get close to the preset temperature.
 
butcher_block said:
i do my tempering the next day cooling the evenheat from 2050 just takes to long + cpm3v calles for 3 tempers at 1000 2 hours each
that makes for a long day
maybe im just lucky that i havent cracked anything yet

how long doeas it take for it to cool down, a day or so?

oh yeah if anyone have any more info, its welcome
 
no not all day but it does take some time maybe 3-4 hours to 300-400 i heat treat after work so im not sticking around to watch it cool all the way off after 1100 pm
next morning its back at room temp tho :D
most the time i run 2 steel types in on night because after the kiln is hot i can ramp it right back up to full heat quickly

like i ll run some 440c 1950f first then some cpm3v or cpm154
till im ready with the 2nd set of blades the temp is back around 1500 or so
its nice because thats about the preheat stage for some of my cpm blade stock
 
You also have to be careful -- with the oven door open, it might cool down to where the temp says 350, but if you close the door, it can shoot back up a couple hundred degrees as the heat radiates out of the firebricks. I had to let my evenheat cool to about 250 today before I could temper at 410. It took about 40 minutes to get from 1425 down to 250 with the door open. A fan would make the cooldown quicker, but would shorten the life of the heating coils. I've heard it is best for the health of the oven to let the oven cool down with the door closed -- that would take many, many hours -- maybe all day??
 
M Wadel said:
Is it necessary to have 2 ovens when heattreating a blade, one for hardening and one for tempering? Ive read that steel should be tempered as soon as the temperature reaches room temp or a little higher, is this an absolute must or can you wait with the tempering a few minutes until the oven cools down. how long does it take for lets say an Evenheat oven to cool down (to tempering temps) if you just open it and turn it off? (a matter of minutes or seconds?)

Is it possible to use the same oven to do both tasks? The ovens are expensive does everybody here have 2 :confused:

If you want to use the same oven for austenizing and tempering, I suggest you pull the blades out of the quench tank or whatever medium you quench in and stick them in an old toaster oven at 200 to 300°F until your HT oven cools down to the desired tempering temperature. This will temper that nice brittle martensite and keep it the blades from cracking until you do a formal temper at the recommended termerature. Since every knife steel I know of requires at least 300°F for a temper it won't hurt them at all.

Jim A.:)
 
If your blades aren't too large,an old Fry Daddy or deep fryer with any type of oil set at 250 to 300 will hold the blades for as long as you like,while the oven cools.
You can even use a fryer to temper your blades if your fryer has a good regulation of the temperature. Use a good frying thermometer.
 
Chant said:
I've heard it is best for the health of the oven to let the oven cool down with the door closed -- that would take many, many hours -- maybe all day??
this is how we did things when i was in the pottery shop
slow cool= longer coil life
not sure how true that might be but im going on the safe side till i hear more
also just for the info im oil quenching 440c and cpm3v then sticking them right in the home freezer till the next day for temper :eek:
no problems yet:thumbup:
 
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