Dragonborn Steel is crucible steel. Crucible steel describes a number of different techniques for making steel in a crucible. Its manufacture is essentially a refining process in which another form of steel that had been consolidated by hammering, such as shear steel, is melted to give a more uniform material. Crucible steel has aroused considerable interest for well over a thousand years and there is a sizable body of work concerning its nature and production.
It's a very high quality steel, rivaling that of Damascus Steel. The steel is very bendable and flexible, due to long crystals of iron formed within the steel and braced by atoms of carbon. The Hellenes typically trade for this steel. Almost all swords produced with Dragonborn Steel are masterwork swords (+1 native bonus).
For more, see Dragonborn Technology