ASTM B664-18(2023)

Standard Specification for 80 % Silver-20 % Graphite Sliding Contact Material

ABSTRACT
This specification defines the criteria for composition and other requirements for sliding contact materials or brushes with a nominal composition by weight of 20% silver and 80% graphite. Materials shall adhere to specified requirements for chemical composition, density, shear strength, and microstructure. They shall also conform to typical values of Rockwell superficial hardness and specific resistance.
SCOPE
1.1 This specification defines the criteria for composition and other requirements for brushes with a nominal silver content of 80 %, by weight, with the balance being substantially graphite.  
1.2 The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to become familiar will all hazards including those identified in the appropriate Safety Data Sheet (SDS) for this product/material as provided by the manufacturer, to establish appropriate safety, health, and environmental practices, and determine the applicability of regulatory limitations prior to use.  
1.4 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: 31-Mar-2023
• ICS: 77.120.99 - Other non-ferrous metals and their alloys
• Technical Committee: B02 - Nonferrous Metals and Alloys
• Drafting Committee: B02.05 - Precious Metals and Electrical Contact Materials and Test Methods

Relations

• Refers: ASTM E18-18 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Jul-2018
• Refers: ASTM E18-17 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Jul-2017
• Refers: ASTM E18-12 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Dec-2012
• Refers: ASTM B613-76(2012) - Standard Guide for Preparing Specifications for Miniature Brushes of Composite Materials for Sliding Electric Contacts
• Effective Date: 01-May-2012
• Refers: ASTM E18-11 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Nov-2011
• Refers: ASTM E18-08a - Standard Test Methods for Rockwell Hardness of Metallic Materials <a href="#fn00002"></a>
• Effective Date: 15-May-2008
• Refers: ASTM E18-08 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 15-Jan-2008
• Refers: ASTM E18-07 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Apr-2007
• Refers: ASTM B613-76(2006) - Standard Guide for Preparing Specifications for Miniature Brushes of Composite Materials for Sliding Electric Contacts
• Effective Date: 01-Jun-2006
• Refers: ASTM E18-05e1 - Standard Test Methods for Rockwell Hardness and Rockwell Superficial Hardness of Metallic Materials
• Effective Date: 01-Apr-2005
• Refers: ASTM E18-05 - Standard Test Methods for Rockwell Hardness and Rockwell Superficial Hardness of Metallic Materials
• Effective Date: 01-Feb-2005
• Refers: ASTM E18-03e1 - Standard Test Methods for Rockwell Hardness and Rockwell Superficial Hardness of Metallic Materials
• Effective Date: 10-Jun-2003
• Refers: ASTM E18-03 - Standard Test Methods for Rockwell Hardness and Rockwell Superficial Hardness of Metallic Materials
• Effective Date: 10-Jun-2003
• Refers: ASTM E18-00 - Standard Test Methods for Rockwell Hardness and Rockwell Superficial Hardness of Metallic Materials
• Effective Date: 10-Jan-2002
• Refers: ASTM E18-02 - Standard Test Methods for Rockwell Hardness and Rockwell Superficial Hardness of Metallic Materials
• Effective Date: 10-Jan-2002

Overview

ASTM B664-18(2023): Standard Specification for 80 % Silver-20 % Graphite Sliding Contact Material sets forth the composition and performance criteria for sliding contact materials, commonly known as brushes, featuring a nominal composition of 80% silver and 20% graphite by weight. This international standard, developed by ASTM, ensures that the materials used for electrical sliding contacts or brushes meet stringent requirements for quality, durability, and electrical performance.

This specification addresses the key properties necessary for reliable operation in electrical machines and components, such as chemical composition, density, shear strength, microstructure, hardness, and electrical resistance.

Key Topics

• Material Composition

  • Silver: 80 ± 3% by weight
  • Graphite: balance
  • Total metal impurities must not exceed 1%
  • Maximum ash content (per NEMA CB-1): 5%

• Physical Properties

  • Density: Minimum 5.15 g/cm³, verified by measurement and weight method (NEMA CB-1)
  • Shear Strength:
    • Normal/transverse: Minimum 2000 psi (14 MPa)
    • Longitudinal: Minimum 1000 psi (6.9 MPa)
  • Microstructure: Must be free of structural defects such as cracks and laminations. The material should not contain abrasive particles that can create slivering in metal rings.

• Rockwell Hardness and Electrical Resistance

  • Typical Rockwell superficial hardness: 44 R15W
  • Typical specific resistance: 4 × 10⁻⁶ Ω-in. (1 × 10⁻⁷ Ω-m), determined according to NEMA CB-1

• Certification and Compliance

  • Materials must be certified by producers as compliant with the standard.
  • Safety, health, and environmental practices must be established by users in line with SDS and applicable regulations.

Applications

• Electrical Sliding Contacts:
  Used extensively in brushes for electric machines, such as motors, generators, and alternators, where reliable electrical contact and low wear are essential.

• High-Current and Low-Voltage Connections:
  Particularly viable in systems needing high conductivity and durability under sliding or rotating conditions.

• Industrial and Transportation Equipment:
  Ideal for use in rail, heavy machinery, and other equipment where robust and efficient electrical transfer is critical.

• Miniature Brushes:
  Although specific properties can differ by size, the standard provides reference values for smaller applications in electronic and precision devices.

Related Standards

• ASTM B613: Guide for Preparing Specifications for Miniature Brushes of Composite Materials for Sliding Electric Contacts.
• ASTM E18: Test Methods for Rockwell Hardness of Metallic Materials - utilized to verify brush hardness.
• NEMA CB-1: Brushes for Electrical Machines - referenced for ash content and physical testing methods.

Keywords: electrical contacts, graphite brushes, silver-graphite, sliding contacts, ASTM B664, sliding electrical contacts, industrial brushes

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ASTM B664-18(2023) provides a clear framework for manufacturers and end-users to ensure that silver-graphite sliding contact materials deliver the necessary performance and reliability for advanced electrical applications, supporting both quality assurance and international trade compliance.

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: B664 − 18 (Reapproved 2023)
Standard Specification for
80 % Silver-20 % Graphite Sliding Contact Material
This standard is issued under the fixed designation B664; 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 3. Requirements
1.1 This specification defines the criteria for composition
3.1 Chemical Composition, shall be as follows:
and other requirements for brushes with a nominal silver
Silver 80 ± 3 % (weight)
content of 80 %, by weight, with the balance being substan-
Graphite balance
Total metal impurities 1 % max
tially graphite.
Percent ash in graphite (NEMA CB-1) 5 % max
1.2 The values stated in inch-pound units are to be regarded
3.2 Physical Properties—The following lot average proper-
as standard. No other units of measurement are included in this
ties must be met. Unless otherwise agreed between the pro-
standard.
ducer and the user, the number of samples shall be five.
1.3 This standard does not purport to address all of the
3.2.1 Density—The minimum acceptable density shall be
safety concerns, if any, associated with its use. It is the 3
5.15 g/cm as determined by the measurement and weight
responsibility of the user of this standard to become familiar
method defined by NEMA CB-1.
will all hazards including those identified in the appropriate
3.2.2 Shear Strength:
Safety Data Sheet (SDS) for this product/material as provided
3.2.2.1 The shear strength for the normal and transverse
by the manufacturer, to establish appropriate safety, health,
directions shall be measured for rectangular parallelepipeds
and environmental practices, and determine the applicability
and shall be 2000 psi (14 MPa), minimum.
of regulatory limitations prior to use.
3.2.2.2 The shear strength for the longitudinal shear direc-
1.4 This international standard was developed in accor-
tion shall be measured for cylinders and shall be 1000 psi (6.9
dance with internationally recognized principles on standard-
MPa), minimum.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
3.3 Microstructure—Parts shall be visually free of structural
mendations issued by the World Trade Organization Technical
defects, cracks, etc., upon examination at 50×. The press
Barriers to Trade (TBT) Committee.
direction, as evidenced by laminations, shall be as defined by
the purchase order. Also the brush material shall not contain
2. Referenced Documents
abrasive particles that will sliver a metal alloy ring with a
2.1 ASTM Standards:
hardness ≥110 HK when the brush force is equal to 30 g or
B613 Guide for Preparing Specifications for Miniature
that necessary for 5.0 psi (34 kPa) pressure, whichever is
Brushes of Composite Materials for Sliding Electric
greater. A sliver is defined as a loose wear particle with one
Contacts
dimension ≥50× the next smaller dimension. Although sliver-
E18 Test Methods for Rockwell Hardness of Metallic Ma-
ing can be caused by coarse abrasive particles, other pa
...