ASTM B279-13(2019)

Standard Test Method for Stiffness of Bare Soft Square and Rectangular Copper and Aluminum Wire for Magnet Wire Fabrication

SIGNIFICANCE AND USE
3.1 This test method is designed as an inspection or acceptance test of new bare soft square and rectangular wire intended for subsequent fabrication into magnet wire.
Note 1: Since the applied unit stress and the time of application are constant for all wire sizes, the test enables comparisons of stiffness to be made between wires of the same or different size on the basis of the permanent elongation resulting from the application of a low unit stress.
SCOPE
1.1 This test method, known as the low-stress elongation (LSE) test, covers the procedure for determining the stiffness of bare soft square and rectangular copper and aluminum wire in terms of the permanent elongation resulting from the application of a tensile stress.  
1.2 The SI values for the mass of the specimen are regarded as the standard. For all other properties, the inch-pound values are to be regarded as standard and the SI units may be approximate.  
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Sep-2019
• ICS: 29.060.10 - Wires
• Technical Committee: B01 - Electrical Conductors
• Drafting Committee: B01.02 - Methods of Test and Sampling Procedure

Relations

• Replaces: ASTM B279-13 - Standard Test Method for Stiffness of Bare Soft Square and Rectangular Copper and Aluminum Wire for Magnet Wire Fabrication
• Effective Date: 01-Oct-2019
• Refers: ASTM E4-14 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2014
• Refers: ASTM E4-10 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2010
• Refers: ASTM E4-09a - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Nov-2009
• Refers: ASTM E4-09 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Apr-2009
• Refers: ASTM E4-08 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Dec-2008
• Refers: ASTM E4-07 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jan-2007
• Refers: ASTM E4-03 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 10-Aug-2003
• Refers: ASTM E4-02 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 10-Nov-2002
• Refers: ASTM E4-01 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 10-Apr-2001
• Refers: ASTM E4-99 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 10-Apr-2001
• Referred By: ASTM B48-00(2021)e1 - Standard Specification for Soft Rectangular and Square Bare Copper Wire for Electrical Conductors
• Effective Date: 01-Oct-2019
• Referred By: ASTM D1676-17 - Standard Test Methods for Film-Insulated Magnet Wire
• Effective Date: 01-Oct-2019
• Referred By: ASTM B324-01(2021) - Standard Specification for Aluminum Rectangular and Square Wire for Electrical Purposes
• Effective Date: 01-Oct-2019

Overview

ASTM B279-13(2019) is the internationally recognized Standard Test Method for Stiffness of Bare Soft Square and Rectangular Copper and Aluminum Wire for Magnet Wire Fabrication. Issued by ASTM International, this standard specifies the low-stress elongation (LSE) test-a procedure for determining the stiffness of bare soft copper and aluminum wires. Primarily intended as an inspection or acceptance test, it measures permanent elongation resulting from a prescribed tensile stress, providing a basis for comparing wire stiffness across various sizes and materials.

Key Topics

• Test Purpose: Ensures quality and consistency for bare soft square and rectangular wires used in magnet wire manufacturing. The LSE test is designed to detect variations that may affect downstream fabrication processes.
• Test Method Overview: The stiffness is measured by applying a low, constant unit stress to a wire specimen and recording the resulting permanent elongation. The process involves:
  • Cutting and preparing the wire specimens to specified lengths
  • Measuring specimen mass and marking a standardized gage length
  • Applying a specified tensile load using a calibrated testing machine
  • Measuring the elongation after load removal
• Comparison Across Sizes and Materials: Since the applied stress and time of application are standardized, the test allows reliable comparison of stiffness between different wire cross-sections and materials.
• Units and Measurements: The standard employs SI values for specimen mass; other properties use inch-pound units as the primary standard. Some SI values may be approximate.
• Inspection and Acceptance: As an acceptance test, compliance with ASTM B279 offers assurance to manufacturers and users of raw magnet wire regarding structural uniformity and suitability for further processing.

Applications

ASTM B279 is vital for stakeholders involved in the production, inspection, and use of bare soft square and rectangular copper or aluminum wires, particularly in the magnet wire industry. Key applications include:

• Magnet Wire Manufacturing: Ensures raw wires possess adequate stiffness for successful insulation, winding, and operation in coils, transformers, motors, and electromagnetic devices.
• Quality Control: Offers a standardized method for incoming wire inspection, reporting permanent elongation and mechanical consistency.
• Purchasing and Procurement: Supports purchasing decisions by providing clearly defined acceptance criteria for suppliers and customers trading in bare conductor wire products.
• Comparative Assessment: The standard enables direct comparisons of mechanical performance, facilitating material selection and process optimization.
• Regulatory and Export Compliance: Adherence to ASTM B279 demonstrates compliance with international standardization principles, supporting smooth trade and regulatory approval in global markets.

Related Standards

Organizations applying ASTM B279 may also refer to:

• ASTM E4 – Practices for Force Verification of Testing Machines: Cited for calibration requirements of the tensile testing equipment used in the LSE test.
• Other ASTM Conductor Standards: Such as those covering round wire, finished magnet wire specifications, and additional metallurgical properties.
• International Guidelines: The standard is aligned with WTO Technical Barriers to Trade (TBT) Committee principles, ensuring international acceptability.

Keywords: ASTM B279, magnet wire, copper wire, aluminum wire, wire stiffness, low-stress elongation, wire inspection, wire acceptance test, quality control, conductor testing, rectangular wire, square wire

For organizations seeking to ensure the quality and uniformity of bare copper and aluminum wires used in electrical and electronic applications, ASTM B279-13(2019) provides a proven and recognized methodology for testing and documentation.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B279 − 13 (Reapproved 2019)
Standard Test Method for
Stiffness of Bare Soft Square and Rectangular Copper and
Aluminum Wire for Magnet Wire Fabrication
This standard is issued under the fixed designation B279; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Apparatus
1.1 This test method, known as the low-stress elongation 4.1 Tensile testing machines used for the low-stress elonga-
(LSE) test, covers the procedure for determining the stiffness tion test shall conform to the requirements of Practices E4.
of bare soft square and rectangular copper and aluminum wire
5. Test Specimens
in terms of the permanent elongation resulting from the
application of a tensile stress.
5.1 The test specimens shall be taken from the finished reel
or coil with a minimum amount of handling and distortion,
1.2 The SI values for the mass of the specimen are regarded
retaining the original curvature of the package to the greatest
as the standard. For all other properties, the inch-pound values
extent possible. Test specimens having the full cross-sectional
are to be regarded as standard and the SI units may be
area of the wire shall be used. The standard gage length for the
approximate.
measurement of elongation of wire shall be 10 in. (254 mm).
1.3 This international standard was developed in accor-
The total length of the specimens shall be at least equal to the
dance with internationally recognized principles on standard-
gage length plus the length of wire required for the full use of
ization established in the Decision on Principles for the
the grips employed.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
6. Procedure
Barriers to Trade (TBT) Committee.
6.1 Straighten the test specimens carefully by hand with a
minimum amount of distortion or cold work. Improperly
2. Referenced Documents
prepared test specimens often cause unsatisfactory test results.
2.1 Thefollowingdocumentformsapartofthistestmethod
6.2 Cut off a test specimen of sufficient length as described
to the extent referenced herein:
in 5.1. Measure the length to the nearest 0.01 in. (0.25 mm)
2.2 ASTM Standards:
with any measuring device accurate to 0.1 % (Note 2). Mea-
E4 Practices for Force Verification of Testing Machines
sure the mass of this specimen to the nearest 0.01 g on a
balance accurate to 0.1 %. The load required to apply a stress
3. Significance and Use
to the specimen equal to 15 000 psi (103 MPa) for copper, and
3.1 This test method is designed as an inspection or accep- 8 000 psi (55 MPa) for aluminum shall be obtained from the
tancetestofnewbaresoftsquareandrectangularwireintended
following:
for subsequent fabrication into magnet wire.
KW
P 5
L
NOTE 1—Since the applied unit stress and the time of application are
constant for all wire sizes, the test enables comparisons of stiffness to be
where:
made between wires of the same or different size on the basis of the
permanent elongation resulting from the application of a low unit stress.
P = Required load, lbs (N),
W = mass of specimen, g,
L = length of specimen, in., and
1 K = 102.74 for copper specimens, length in in., required
This test method is under the jurisdiction of ASTM Committee B01 on
Electrical Conductors and is the direct responsibility of Subcommittee B01.02 on
load in lb, or
Methods of Test and Sampling Procedure.
K = 11 612.7 for copper specimens, length in mm, required
Current edition approved Oct. 1, 2019. Published October 2019. Originally
load in N, or
approved in 1953. Last previous edition approved in 2013 as B279 – 13. DOI:
K = 180.5 for aluminum specimens, length in in., required
10.1520/B0279-13R19.
For referenced ASTM
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