What will hold up to the heat?

Don't know the size of the door nor the thickness. but two cast iron frames ( left and right) and fire bricks in-between should do it .

Thanks for the response, I guess I did leave out one important factor, these are carborizing furnaces, cast would become brittle quick.

Look up Inconel 909 or similar alloys.

Ceramic?

I don't believe it's about the material being used but about the way the materials are being used. If the insulated door is made up of two sheets of metal (same material), then you're definitely going to keep up the warping since you've got similar thermal expansion coefficients but the material exposed at a different temperature which means warping.

A solution could be to have these doors modified in a way that the they are allowed to contract/expand (instead of welding, screws fitting into a slot instead of a hole) and then you can stell use material which are as cheap as the temperature/atmosphere allows you to.

Hope it helps...

If the door is hollow and has the insulation inside then I would suggest applying more of the insulating material on the outside as the poster above suggests maybe use fire bricks or a high temp resistant ceramic type tile epoxied onto the outside of the door.

Good Luck, let us know how it turns out.

I tend to agree with the commentator who said they did not believe it was a materials problem. It seems more like a design problem. I'm assuming that the door surrounds the insulation. You also mention the materials of the door frame but don't really give enough information about the interaction between components to tell for sure what is going on.

I'm assuming that the warping of the door is interfering with its functioning. The fact that the problem is ?transferred? to the door's frame implicates the hinges.

If one side of the door is constantly hot during normal operations and the other varies between hot and cooler then there will be contraction on the cool side. The contraction will only cause warping if the structure is rigid. If the doors construction allows a free floating plate to contract within a floating frame or floating attactment aggraingement then the door will not warp. If the hinges allow for movement of the door member and misallignment of the door's hinge plates then the malfunction will be prevented.

Solving your problem could be as simple as putting an undersized hinge pin in the hinge. If there is interference between the curls of the opposed hinge plates then milling or even filing to increase the clearance could help solve the problem.

If a more complete solution is required to maintain the sealing of the door then look at a thermal stress compensating design that includes free floating plate or panel on the door. Traditional wooden doors always had this problem and could indicate some good design solutions. I would also encourage you to communicate with the furnace manufacturer. If you have two furnaces with this problem imagine how many they have...

Blessings,

Mr. Gee

Thanks, The door is actually a channel frame with brick inside, it operates by sliding in a channel up and down with the operator on top of the unit.

Make the frame such that you can use the outer (or perhaps only) layer of grooved bricks so the frame is entirely covered by brick on the surfaces that face the heat.

Suggest putting insulating brick (and Kaowool ceramic fiber blankting) on the outer faces of the door to protect the metal faces from the heat that causes distortion of the metal.

Ceramics are the way to go with this. Alumina and silica are the best materials to use.

The Alumina has poor thermal shock properties with out going with expensive high purity. The silica or quartz plates, depending on the process, can be reasonable.

The thermal expansion is basically nil. You can heat the plate to 1000C and immerse it in chilled water. It may sound mad when you quench it, but there will be no dimensional changes.

At one point I worked with coke oven refractories (virtually all of them were "silica brick"). If you want to see massive spalling of a ceramic material try water quenching of bituminous coke inside a red hot coke oven (coke at ~1800 F). A couple of idiot inventors actually got a US Patent on this and sold the idea to a not-too-swift corporate management (steel company unnamed). Guess what happened on the very first trial. They wiped out a coke oven wall (made of silica brick). $1.0 Million for repairs. Needless to say there were no repeat performances.

Try this sit ... it can supply ceramic door frames and even moulded doors which will work out better for you i think.Refractory Products Ceramic Fiber, Ceramic Fiber Rope, Ceramic Fiber Board, Ceramic Fiber Cloth, Silica Cloth, Insulating Fir...