Do not use ingots for this recipe if possible. Breaking an ingot down into nine nuggets will usually give you more Metallum overall allowing you to get a much more fair conversion ratio. You will, however, lose the "bonus" aspects of the ingots (e.g. Copper Ingot has six Metallum and two Victus vs. nine Copper Nuggets with one Metallum each).
You are now able to transform other metals into iron nuggets.