Unfortunately, it is rather brittle, and worse, it can't be bent or shaped in any way once it has solidified. Hammering on red hot, even white hot, cast iron will simply break it. Steel, iron with a small amount of carbon dissolved inside its structure, combines the best of both worlds. It can be cast into moulds from the furnace, shaped when red hot, and it holds an edge when it has been sharpened, even under fairly heavy use. Steel is clearly the prince of ferric metals, but it's not easy to make.
Carbon is the major variable that distinguishes between wrought iron, steel, and cast iron.
Because the smelting furnace doesn't let the operator control the carbon content with any degree of precision. The job of the smelting furnace is to reduce the metal from its chemically combined state to a metallic state. Iron is a reasonably common substance in the earth, but as any owner of an old car will attest, most of the time it takes the form of rust, iron oxide. In the smelter, iron oxides and other chemically combined forms of iron have their chemical bonds broken. This allows the iron atoms to combine into a mass of metal.