ASTM A901-03(2008)

    Standard Specification for Amorphous Magnetic Core Alloys, Semi-Processed Types

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    1. Scope

    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/A 773M.

    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.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    A34/A34M Practice for Sampling and Procurement Testing of Magnetic Materials

    A340 Terminology of Symbols and Definitions Relating to Magnetic Testing

    A370 Test Methods and Definitions for Mechanical Testing of Steel Products

    A664 Practice for Identification of Standard Electrical Steel Grades in ASTM Specifications

    A700 Practices for Packaging, Marking, and Loading Methods for Steel Products for Shipment

    A712 Test Method for Electrical Resistivity of Soft Magnetic Alloys

    A773/A773M Test Method for dc Magnetic Properties of Materials Using Ring and Permeameter Procedures with dc Electronic Hysteresigraphs

    A900/A900M Test Method for Lamination Factor of Amorphous Magnetic Strip

    B490 Practice for Micrometer Bend Test for Ductility of Electrodeposits

    C693 Test Method for Density of Glass by Buoyancy

    D3455 Test Methods for Compatibility of Construction Material with Electrical Insulating Oil of Petroleum Origin


    ICS Code

    ICS Number Code 29.030 (Magnetic materials); 29.100.10 (Magnetic components)

    UNSPSC Code

    UNSPSC Code 31380000(Magnets and magnetic materials)


    DOI: 10.1520/A0901-03R08

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