coal forge question

[chewbroccoli]

I'm planning on building a coal forge to start forging. so far this is my plan.

I'm not sure what to use as the grey area on the picture. I was thinking some kind of cement, but not cement because I imagine it would crack and disentigrate from the heat. perhaps some kind of fireplace mortar? also I'm not sure how to pour it with the conical area in the middle open for air. I have little experience with metal (hopefully more soon) and none with cement type materials but I do have experience with woodworking.

that pic is pretty small so here's a link to it bigger.
http://www.freewebs.com/selmac/stuff.htm

any and all advice is appreciated. thanks

 

[Fred.Rowe]

The plan looks straight forward to me. I have a nice coke forge for sale if you live within pick up distance of s/e Ohio. A ton of coke goes with it. The metalurgical type. Fred

 

[IronWolf]

Check in your area for refractory materials. a good rammable refractory is easy to form and will last years and years. but in the past, I have built forges out using sand, dirt, river clay or clay cat litter to serve as a firepot.
I would like to suggest two things about your grate though, first, I have found that drilled holes can plug up with clinker, slotted grates are easier to keep clean, and sometimes you can find cast iron drain covers 4" round and 3/8" thick for $4-5 at a hardware store. You will probably want to put the grate lower in the tuyere. A fire needs to be deep enough to work properly. a fire that is too shallow will lead to excess oxidation, pitting, and burning of steel. this can also happen if you put the steel into the fire angling down. I would suggest at least a three inch bed of coal below the steel for general work, and four inches for welding.

Good Luck
Ken