Forge floor question

[Dr.O]

I will not be welding in this forge, but doing some heat treating. I've never built or used a forge, but all the makings are in my shop.

Materials in hand are ,ceramic fiber, IFB, hard brick, itc-100, itc-213, satainite, sairbond, ins-tuff,

This will be a 7" diameter shell, 10" deep, one inch blanket.

Here is what I'm thinking



Regarding the floor only.

I know hard brick will be more durable, but being I'm using this strictly for heat treating, would the softer insulating brick be better than rigidized blanket, with sairbond, and ITC-100?

 

[Stacy E. Apelt - Bladesmith]

If doing only HT, I would just use the wool blanket all the way around. If you want the floor to have a small flat place, shape that in when applying the satanite there*. Keeping the basic shape of the chamber round will aid in more even flame flow. Evenness of heat is what you need in a HT oven. If all the sides, including the floor, are the same material, the heating will be more even. If there are no changes in curvature, then the flame will heat all these surfaces evenly.

BTW, I would raise your burner a tad so the flame comes in just about the top of the chamber in the sketch. The top of the burner tube should be on a chord that is about 1/4" below the tangent of the chamber circle. What that means in bladesmith-talk is - Draw a line that touches the top of the chamber circle. That is the tangent. Draw a parallel line below it. That is a chord, and is the axis and angle the burner should be on. The top of the burner tube should rest on this line.
Your sketch is very close to this, but I wanted to let you know how to determine the placement and angle in a full size drawing.
It should be placed 1/3 the distance from the rear of the forge and angled 15° forward, too.

*Now, for a trick on how to get a really nice flat chamber floor:
When ready to put on the first coat of satanite ( or the rigidizer if you are using it) on the kaowool, take a piece of 1/4" steel bar that is 1.5-2" wide and is an inch or so longer than the chamber length. Wrap it in Saran wrap. When the satanite is applied, set the wrapped bar where the floor will be. It will make a perfect straight and flat floor. Remove it when that coat of satanite is dry, and apply the final coats of refractory as normal.