This specification covers the general requirements to which flat-cast, amorphous, semi-processed, iron-base magnetic core alloys must conform. These alloys shall be produced by a rapid-quenching, direct-casting process, resulting in metals with noncrystalline structure. The metallic alloys shall be made to meet specified maximum core-loss values and shall be intended primarily for commercial power frequency applications in magnetic devices. Desirable core-loss and permeability characteristics shall be developed by further heat treatment in a magnetic field. Amorphous magnetic core alloys shall be composed principally of iron with small amounts of alloying elements such as boron and silicon. Other chemical elements shall be in residual amounts or can be added to improve fabrication or the physical or magnetic properties. The material shall conform to the required physical and mechanical properties such as density, ductility, thermal expansion, thermal conductivity, volume resistivity, lamination factor, surface, edge, and pinholes. The alloy shall also conform to the magnetic property requirements such as DC induction, DC coercive field strength, DC residual induction, core loss, and specific exciting power.