There are several ways to forge an axe I will try and explain one method:
the fist step is to find a piece of mild steel about 3 inches by 5 inches by 3/8 of an inch (7.5mm by 125 mm 9.5 mm.) and a piece of high carbon steel about 4 inches by 1 inch by 3/8 of an inch. (100mm by 25mm by 9.5 mm)
Heat and spread both ends of the the 3 inch of the steel into a fan shape. Make sure both fans are the same size and shape. Fold the mild steel in half leaving room for an eye for the handle. Heat and taper the long sides the steel to a point.
Start forge welding the mild steel from about 1/3 the distance from the eye to just about 3/4 inch (19mm)from the edge of the fan shape. Shape the hole the the wood handle is inserted in.
Match the steel to the curve of the of the fan. Forge weld the mild steel and high carbon steel together. Harden and temper the edge of the axe. Grind the axe to its final edge.