Building My First Heat Treatment Oven!!!!

[jackwrabbit]

Hello all, I'm in the process of building a heat treatment oven for knife blades and am looking for any and all help I can find. The temps will be up to ~1300°C. I am trying to stay on 120V @ <20A.

I need ramp and soak so am looking at the JLD634 as the controller.

Would I need something like the High Temperature (2370'F/1300'C) 10ft Ceramic K type Thermocouple or would is there another (cheaper) one that would work as well.

I am using K-26 insulating fire brick in a sheet metal enclosure and cutting grooves in the brick for the heating element. I haven't bought the element yet so any help on that (or anything else) would be greatly appreciated.

Jack

[Entropy]

i have read that some brick ovens embed thermocouples in the 'mortar' that lines the interior of the oven. I can say that the type thermocouple you are looking at is typically used in ovens with the ceramic insulator on the probe and ceramic beads protecting the leads. A lot of kitchen ranges even have a ceramic insulated temperature probe. Ceramic insulators are commonly used to support heating elements including infrared elements of convection-toaster ovens and space heaters.

Having said that, there are options but they won't be cheaper i would imagine. The main distinction is where you need to measure temperature. This will measure the temp of the atmosphere inside the oven near the brick. If that's good enough, then that's likely your banana. If on the other hand, you want to beasure the temps of the knives themselves or as close to them as possible, then you might look at alternatives. There are Magnesium Oxide thermocouples that are superior to ceramic industrial types like this whose insulation is good up to 3000 degrees F i recall. These would be more flexible and could be clamped to a knife for example. The K and N type thermocouple wires are the highest temp types and it is a matter of how much temperature the insulation can stand--without insulation, thermocouples tend to be unreliable. N type is a fairly recent improvement, special application, of the K type--more linear temperature response i think. So you want a K type with very high temp insulation which tends to be the limiting factor.

Okay, i just ran a price check and can get you a longer probe of 18 inches ($46.65) that has an industrial head as the one you are looking at but would reach into the oven that will:

"In tests up to 1335°C (2400°F), Super XXXXXX outperformed both the Inconel® 600 and other competing high-temperature models". If you aren't going to use the RS485 feature of the 634 then you can buy a cheaper version from lightobject without it. (i just returned one i bought from them via a mass merchandiser as i had thought it would have had the RS485 as i hope to run my profiles off a computer --be aware i am a bit stymied as the CD for the RS485 Comm is entirely in Chinese and i expect it is going to be a bear to figure that one out. The non RS485 634 version cost me about $20-30 less for which i was just refunded today as i purchased the one with the RS485 direct from them instead.

Back to the alternative: they come with sheathed probes up to 24 inches and you can get a diameter down to 1/16" which would give you a lot faster response time.

If your process is a gentle long term soak and temps are not real critical the industrial oven sold here would work okay.

It is rather unfortunate that to be of best assistance is not particularly comfortable.