You heat a patch of air to the great temperatures of a forge. You can hold up metal to that area and soften it just as a real forge would and then work the metal appropriately. Only items placed in the heated area by the caster are affected; the heat doesn’t affect anything else, and it can’t be felt by living creatures at all. This spell, along with a portable anvil, greatly lessens the difficulty for a craftsman repairing equipment in the field.
Enhancement: If air forge is cast using a spell slot higher than 2nd level, it heats a number of cubic feet of air equal to the spell slot used.