steel and clay combo a bad idea?

[downthevalley]

We are just starting out some very preliminary plans for a backyard pizza oven. We have a piece of steel laying around, and are considering bending this into a barrel type shape, then covering the steel with clay or some other type of insulation. My partner is very intent on using the steel, but I haven't really come across any designs that use both steel and clay (it would just be one piece of steel, not double layered), I'm wondering whether this might be due to this having potential to cause issues? Would the steel likely help with getting the oven hot? Anyone have experience with this or maybe an informed opinion on how it might go? Thanks all!

[david s]

Steel is way more conductive than clay , brick or refractory, so it will heat faster but also cool faster. It will also expand first and probably crack any clay mix placed on top of it. If the steel is thin it is prone to rusting pretty quickly so it needs to be relatively thick. Build it and report back.

[downthevalley]

Steel is way more conductive than clay , brick or refractory, so it will heat faster but also cool faster. It will also expand first and probably crack any clay mix placed on top of it. If the steel is thin it is prone to rusting pretty quickly so it needs to be relatively thick. Build it and report back.

Thanks for the advice! I think we'll just go ahead and build and see how it goes

[david s]

Thanks for the advice! I think we'll just go ahead and build and see how it goes

Excellent idea. Search the forum for steel ovens, there have been quite a number. Please keep us up to date with your progress so we can all benefit.

[MarcD]

I am also planning a steel inner dome build. It's my second oven build but my first steel build. My plan is to bond refractory bricks to the outside of the dome, fill the spaces, blanket the dome, then build a box around it to fill with an insulator. I'm not too worried about long term heat retention as I never used my previous oven as a slow cooker. If my bonding idea doesn't work after a few test fires then I'll change my plan but I'm honestly not too worried about cracking refractory as the dome will be inside of a box and covered with an insulator. As long as the dome heats evenly I'll be pretty happy.

My steel is 1/4 inch thick and the dome itself is 36 in with an interior height of 21 inches. The first 6 inches of the wall is vertical before the radius of the dome begins.

I'll wait until I start building the stand before starting my own thread.

[david s]

I'm sure it will work, but the highly conductive steel will expand well before the bricks have a chance to heat up. This causes the steel to expand against the bricks and as it's 1/4" thick it will have enormous power. You may find that contact points between the steel and brick will be reduced thereby slowing heat travel by conduction. This situation is exacerbated by the flat surface of each brick sitting against the curved surface of the dome as well as a reduction of contact points as soon as the steel dome has cooled a bit, which it does because its conductivity will make it contract just as fast as it expands on heating.

[MarcD]

I think I have a solid plan to deal with maintaining contact across the radius of the dome. Perhaps even trimming each brick. If my plan proves to be too time consuming I may use a castable material. I've test fired the dome to 900 degrees and the thermal expansion is not measurable by any instrument I own. While I'm certain there will be some cracking if I pour cast refractory over the structure, I think I can work around the issue. Especially with a box finish on top. I really like how Wiley did his but I feel inclined to try my own plan.