Electrical Heat Treatment Oven
Introduction: Electrical Heat Treatment Oven
I am making knifes as a hobby. For hardening my first knifes a used my old charcoal grill. It works, but was not that precisely and also not really comfortable.
So I desiced to build my own electrical heat threatment oven. And this process I will show you here:
Step 1: Material Needed
* fire light bricks (number depends on oven size)
* kanthal wire
* PID controller
* K-type Thermocoupple
* solid state relay with heatsink
* high temperature refractrory cement
* ceramic connectror
* some electrical cable
* power switch
* some hand tools (drill, saw, grater)
* Optional: PC fan with 12V power supply
* Optional: wood for the platform
In my case, I get the old kiln from my aunt, <PERSON> gives me most of the parts for my oven.
Step 2: Optional: Disassembling the Old Kiln
I get the old kiln from my aunt. So I decided to use as much as possible from the kiln. To do that, I have to disassemble everything.
I want to use the old kanthal wire. To remove it, you have to be very carefull because it breaks very easily. By heating up the wire with a torch you can make it softer, so it will bend and not brake. By heating up the wire I remove one layer after the other.
At the end. I have enough bricks to build the oven and at least one kanthal wire which is long enough.
Step 3: Build Up the Oven
At first, I need a big base plate. Therefor I used parts of the old base plate. I marked the saw lines and used and old bucksaw. You can use a saw which is specially made for cutting these bricks. But I don't have one and also I didn't want to buy one. The old bucksaw works fine, but after all that cutting, the saw is really done.
My base plate is around 20x10 inches, but you can scale it however you want. Important point is here, larger oven needs much more time for heating up, so you need more power or more time.
After the base plate is finished, I cut all off the bricks to size. First cut the ends off to get rectaangular bricks, then cut to the right length. With high temperature refractrory cement I filled up the gaps in the base plate to get a smooth surface and I also use it to stick the bricks toghether.
As next step I put the kanthal wire in the slots. Again be carefull to not break it. 34
I drilled two holes in the brick on the backside to put the wire throught. There will be the connection to the control unit by using the ceramic connector.
My oven sits on a wooden plate. I also build a frame out of wood that holds everything together. If you are able to work with metal, you can also use angle iron or something like that. I have no welding machine, so wood was easier. I put two more layers of thinner bricks between the inner bricks and the wooden frame because I am not sure how hot the bricks become on the outer side. So to be safe I made the walls thicker. These layers and also the bricks on top where only stacked without using cement. You can fix them with cement, but I think it is not necessary. By looking on the picture you can see some gaps between the stones. I think and hope this does not effect the function of the oven. The gaps were a result of the free-hand cutting of the bricks. By using new bricks or spend some more time on cutting really straight you can avoid the gaps. But in my case, I can't cut off more material to get 90° cuts, because if I do that the bricks become to small.
Step 4: Wiring Everything
After the oven is build up, we have to focus on the electrical part.
IMPORTANT: The oven is running with 230 V (I live in Europe). Working with mains voltage is really dangerous. Make sure you know what you are doing, or ask someone who knows it.
I made a small case out of 15 mm plywood. My front panel has cutouts for the PID controller and the main switch. The back panel and one side panel have cutouts for two pc fans for cooling.
In the picture you can see a small 12V power supply for the fans, the solid state relay (SSR) and the PID controller. Two cables run out of the box. One to the K-type thermocouple and one to the kanthal wire.
For cooling, the SSR is mounted to a heatsink. 98