I have four forges. Two gas and two coal. I built all of them but one. You can build your coal forge using a Centaur Forge fire pot, some angle iron for the frame and legs, and a steel plate for the bottom. You can weld the frame and legs together in little time. Use a cutting torch, cut a hole in the steel plate for the firepot. Some plumbing and your in business. I use a hand crank blower. I built my last coal forge in less than a day.

I built a gas forge (to heat long bar's for twisting) using a large diameter scrap piece of pipe about 27" long. I used K-wool for the liner inside and I found a used blower motor from a clothes dryer for the blower. Reasearch online for ideas on the plumbing. This gas forge workes very well and heats up a long bar in no time. The only thing I don't like is after building a 40' railing for a customer I have already worn out the K-wool. I have more however and it's easy to replace.

Actually just found an arc welder in the garage the other day. Where can I purchase angle iron and steel plate? Home Depot?

Look in your phone book for a steel yard. There should be a steel yard in a town somewhere near you.