Guidance for using mica strip heaters

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Ryoko
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I need to make an oven to anneal aluminum strips. I am looking at using strip heaters inside a tube as a makeshift oven. But it's not clear if they'll work in a 700F environment without overheating and destroying themselves.
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R

Thread 'Induction heating of aluminum strip possible?'

I need to anneal a strip of aluminum 1" wide and 0.032" thick. The strip is 7 feet long. The way I'm currently doing it is to use the old trick of using a Sharpy to draw a black line down the part, hanging the strip vertically, then heating the strip with a propane torch from top to bottom a few inches at a time starting at the top and working my way down to the bottom until the black Sharpy mark disappears. This is a really slow process and those propane cylinders get expensive after a while.

I'd like to be able to heat the strip faster and not have an open flame which is a little hard...

I need to make an oven to anneal aluminum strips. I am looking at using strip heaters inside a long tube as a makeshift oven. The strips are 1" wide and 7 feet long. My idea is to make a tube-shaped convection oven large enough to hold the strips and be able to provide the 700-750F heat needed to anneal the aluminum. The problem I'm having is finding a suitable heat source. Finned strip heaters look like they'll do the job. But I'm not sure how to use them in an enclosed space. The two big questions I have is will the finned strip heaters survive being in a 750F environment without running away and burning themselves up. The other question is how to get power to them without frying the lead wires since the connections would be inside the oven.

An alternative under consideration is to use flat strip heaters mounted to the outside of the tube oven to heat the wall of the tube. This would presumably prevent the strip heater(s) from running away since it would act as a more substantial heat load compared to heated air.

Two different construction options are available: The first is to use 4" steel HVAC duct work (28g) for the oven. The other option is some 5" aluminum irrigation pipe I have laying around which would presumably work well with the surface mounted strip heater. But I'm not sure the 6061 aluminum would react well to 750F heat.

I tried to Google for some examples of these strips in actual service. But all I got were lots of promotional sales pics. Any suggestions or guidance would be appreciated.
 
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In order to heat the aluminum strips to 750 deg F, the heater will need to be at a higher temperature. How much higher depends on design details, but I suggest using a design temperature at the heater of at least 900 deg F.

I do not advise steel HVAC duct. That material is zinc plated steel. Check the melting temperature of zinc.
I do not advise aluminum pipe. The peak temperature is too close to the melting point of aluminum.
One possibility is insulated stainless steel stove pipe. That stuff is designed for high temperatures and is insulated. You need insulation to make this oven work. Stove pipe is available from wood stove and fireplace stores, and building supply companies such as Home Depot in the US.

Try searching Amazon for high temperature wire. That search found some affordable wire that looked like a good fit for this.