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.

1.1 This specification covers the general requirements to which flat-cast, amorphous, semi-processed, iron-base magnetic core alloys must conform.

1.2 These alloys are produced by a rapid-quenching, direct-casting process, resulting in metals with noncrystalline structure. The metallic alloys are made to meet specified maximum core-loss values and are intended primarily for commercial power frequency (50- and 60-Hz) applications in magnetic devices. Desirable core-loss and permeability characteristics are developed by further heat treatment in a magnetic field by the purchaser. The heat treatment typically consists of heating the material to a temperature of 320 to 420°C in a dry, inert atmosphere for 5 to 10 min, although soak times of up to 2 h may be used for large transformer cores. A magnetic field may be required during annealing as designated by the producer. Exact optimum annealing conditions depend on the processing of the material and the size and shape of the device.

1.3 Some of these alloys are sensitive to mechanical stress. Care must be exercised in minimizing any stresses on the material in its final application, otherwise, its magnetic properties will be impaired significantly.

1.4 This specification is developed to aid in the purchase of transformer grade amorphous strip. It provides the chemical, physical, and magnetic parameters and procedures for quality control tests.

1.5 The values stated in customary (cgs-emu and inch-pound) units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units which are provided for information only and are not considered standard.

Note 1—For more information on procedures associated with this specification, refer to the following: Practices A 34/A 34M, A 664, A 700, and B 490; Test Methods A 370 and A 773.

1.6 This standard does not purport to address the safety concerns associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.