'Mild steel' is a broad, loosely defined term thrown around in the metals industry and usually refers the metal chemistry, most specifically carbon content. I agree with the definition in Groundhog's link, although it's not common to see the term clearly defined. Mild steel would be the most common type of steel that a hobbyist would encounter, including most structural steel and sheet metal.What exactly is "mild steel", is it hot rolled, like angel, and plate, or is it something different? I see people doing projects, and they say they used mild steel.Inquireing mind wants to know