DIY cast heat treating oven?
 

On their way (mostly from China) are all the parts needed to cast, and control a small heat treating oven.

I have cast soundproof concrete (speakers), so I have an idea what I've gotten into, but I need to design the casting mold.

The power supply will be 15A 110V, so I bought a 1500W element. I have 2 cubic feet of 3000* concrete, so I have enough to work with.

What is a good, cost effective size? Has anyone here gone too small, or too big?

How thick should I go? I don't mind if the outside gets warm, and I don't want to make the thing unnecessarily heavy.

For simplicity, I'm going with a removable lid (at least this time). I'd rather not frame this for a door, and I have yet to get answers on whether I can cast steel into this thing, for re-enforcement or hinge mounts.

Any clues or ideas will be much appreciated. "thumbsup"

Re: DIY cast heat treating oven?
 

Heat treating is a science mixed with some voodoo and black magic. I would call the closest heat treater and see if they'd give up a few trade secrets. Don't forget that super spendy Rockwell gauge to test your finished parts with.

Re: DIY cast heat treating oven?
 

Rockwell? So, SAE doesn't recognize the "too many batteries/too much trigger" test method?

The concrete folks got back to me... too much difference in the expansion rates to get away with thinner walls/re-enforcement. This thing is gonna weigh.

The parts are all in. All I need to come up with is the best way to attach and connect the element, and then to finalize the design. The 'crete is not cheap, I'd like to make a go of the first try, if possible.

If nothing else, maybe I can make this a "Do not do this" thread.

Re: DIY cast heat treating oven?
 

Sounds like you definately have the potential to burn your house down like those who drop a frozen turkey in a fryer. Post pics when you finish this thing, I don't know what parts you're doing, but the ghetto way of heat treating is to use a propane torch, like on those soft Blitz drive cups till they're red hot and quench them in oil. They also sell a few products to coat the part with before you hit it with the torch so it will carbonize or somthing like that. I hear sugar works just as good.

Re: DIY cast heat treating oven?
 

Jeez! :roll: I'm not stupid enough to burn my house down! I'll post pics of the shop, after the firemen leave.

I've never heard of using sugar, but it makes sense... plenty of free carbon.

I'll be using it for axles, gears, and small stuff like cups. I'll also be using it to anneal, I like making tools from other tools. Got a bunch of vermiculite waiting for that.

Your method is a good one, for case hardening. I need to go deeper.

Re: DIY cast heat treating oven?
 

Cheatin, I've been thinking about your suggestion of using sugar to case harden.

If the part is heated (not cherry) enough to candy coat it, then processed, I wonder if that candy barrier will prove to isolate the part from atmospheric oxygen (prettier initial finish, higher carbon loading?), or if it will chemically accelerate oxidation. I'm not a chemist, I can't even guess... but, we'll eventually find out, here.

Thanks for chiming in, man! Gotta keep the Brain Candy bowl full. "thumbsup"

Re: DIY cast heat treating oven?
 

That isn't 'heat treating', it's annealing. If you want to temper ( harden) the metal, there are very specific colors to watch for as the metal SLOWLY gets heated. Read some threads about knife/sword building, they can be helpful. I spent a few days gathering up information before I attempted building leaf springs. It was a pretty involved process for tempering the high carbon steel but the end results were worth the research.

Re: DIY cast heat treating oven?
 

Finished the 400*c controller. 1 more (1200*c) to go.

Ebayed in the relay (SSR), the controller and the sensor... the rest is salvage. The box is an old PC power supply, painted with the dregs left in 2 spray cans. The switch now defeats the 5VDC (old phone charger), which kills the relay and the fan... allowing passive monitoring.

It holds the temp in my (nearly finished) ex-toaster oven within 2*c, so I'm almost ready to play with forming.