ASTM B500/B500M-24

Standard Specification for Metallic Coated or Aluminum Clad Stranded Steel Core for Use in Overhead Electrical Conductors

ABSTRACT
This specification covers zinc-coated (galvanized), zinc-aluminum-mischmetal alloy-coated, and aluminum-coated (aluminized) stranded steel wire core inserted for use in aluminum conductors, steel reinforced (ACSR). Prior to stranding, the metallic coated steel wire to be used in the production of the stranded core shall meet all of the requirements of the appropriate specification. Requirements for (1) coated steel wire joints, (2) stranding of the core such as lay length and lay direction, (3) construction of ACSR, and (4) tensile properties of stranded core are detailed. The standard stranded core lengths and methods of determining rated strength and calculating loads are given.
SCOPE
1.1 This specification covers 7-wire, 19-wire, 37-wire, and 61-wire zinc-coated (galvanized), zinc-5 % aluminum-mischmetal alloy-coated or aluminum clad stranded steel core intended for use in overhead electrical conductors.  
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
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: 31-Mar-2024
• ICS: 29.240.20 - Power transmission and distribution lines
• Technical Committee: B01 - Electrical Conductors
• Drafting Committee: B01.05 - Conductors of Ferrous Metals

Relations

• Replaces: ASTM B500/B500M-22 - Standard Specification for Metallic Coated or Aluminum Clad Stranded Steel Core for Use in Overhead Electrical Conductors
• Effective Date: 01-Apr-2024
• Referred By: ASTM B856-22 - Standard Specification for Concentric-Lay-Stranded Aluminum Conductors, Coated Steel Supported (ACSS)
• Effective Date: 01-Apr-2024
• Referred By: ASTM B701/B701M-22e1 - Standard Specification for Concentric-Lay-Stranded Self-Damping Aluminum Conductors, Steel Reinforced (ACSR/SD)
• Effective Date: 01-Apr-2024
• Referred By: ASTM B549-22 - Standard Specification for Concentric-Lay-Stranded Aluminum Conductors, Aluminum-Clad Steel Reinforced for Use in Overhead Electrical Conductors
• Effective Date: 01-Apr-2024
• Referred By: ASTM B232/B232M-24 - Standard Specification for Concentric-Lay-Stranded Aluminum Conductors, Coated-Steel Reinforced (ACSR)
• Effective Date: 01-Apr-2024
• Referred By: ASTM B779-22 - Standard Specification for Shaped Wire Compact Concentric-Lay-Stranded Aluminum Conductors, Steel-Reinforced (ACSR/TW)
• Effective Date: 01-Apr-2024
• Referred By: ASTM B711-22 - Standard Specification for Concentric-Lay-Stranded Aluminum-Alloy Conductors, Steel Reinforced (AACSR) (6201)
• Effective Date: 01-Apr-2024
• Referred By: ASTM B857-22 - Standard Specification for Shaped Wire Compact Concentric-Lay-Stranded Aluminum Conductors, Coated-Steel Supported (ACSS/TW)
• Effective Date: 01-Apr-2024
• Referred By: ASTM B401-22 - Standard Specification for Compact Round Concentric-Lay-Stranded Aluminum Conductors, Steel-Reinforced (ACSR/COMP)
• Effective Date: 01-Apr-2024

Overview

ASTM B500/B500M-24 is the current ASTM International standard specification for metallic coated or aluminum clad stranded steel core used in overhead electrical conductors. This standard is essential for ensuring the quality, strength, and reliability of the steel core within aluminum conductors, steel reinforced (ACSR) cables. These cables are widely used in transmission and distribution lines for electric power utilities due to their superior mechanical and electrical properties.

The specification covers different metallic coatings for steel core wires, including zinc-coated (galvanized), zinc-5% aluminum-mischmetal alloy-coated, and aluminum-coated (aluminized) options. Both SI and inch-pound units are recognized as standard, but they are to be considered separately to maintain conformity.

Key Topics

• Types of Coatings: The standard addresses wire cores with various protective coatings:

  • Zinc-coated (galvanized)
  • Zinc-5% aluminum-mischmetal alloy-coated
  • Aluminum-clad (aluminized)

• Construction: Outlines stranded core configurations for 7-wire, 19-wire, 37-wire, and 61-wire constructions, with precise requirements for lay length, lay direction, and strand uniformity.

• Mechanical Requirements:

  • Tensile Properties: Specifies minimum requirements for rated and ultimate tensile strengths to ensure mechanical resilience under operational stress.
  • Stranding Practices: Establishes criteria for acceptable wire joints, lay lengths relative to wire diameter, and correct stranding to facilitate safe installation and maintenance.

• Quality Assurance:

  • Testing protocols for each lot or production batch to verify compliance with physical and mechanical requirements.
  • Inspection practices at the point of manufacture, unless otherwise agreed with the purchaser.

• Marking and Packaging: Requirements for clear marking of packaging, including strand construction details, lay direction, coating type, and manufacturer information for traceability.

Applications

Stranded steel core with metallic or aluminum coatings is primarily used as the strength-bearing component in overhead electrical conductors, notably aluminum conductors, steel reinforced (ACSR). Key applications include:

• Transmission and Distribution Lines: The steel core provides high tensile strength and supports long span installations common in power grids.
• Utility Infrastructure: Used by electric utilities for efficient, reliable power delivery, especially in environments requiring corrosion and weather resistance.
• High-tension Installations: Suitable for conductors exposed to heavy mechanical loads, extreme weather, or requiring enhanced durability.

The standard supports robust, long-lasting overhead conductor systems, helping utilities meet performance and safety expectations.

Related Standards

Several referenced ASTM standards ensure the quality and compatibility of steel core wires used under ASTM B500/B500M-24:

• ASTM B498/B498M: Zinc-coated (galvanized) steel core wire for overhead electrical conductors
• ASTM B502/B502M: Aluminum-clad steel core wire for overhead electrical aluminum conductors
• ASTM B606/B606M: High-strength zinc-coated steel core wire for overhead electrical conductors
• ASTM B802/B802M: Zinc-5% aluminum-mischmetal alloy-coated steel core wire for use in overhead electrical conductors
• ASTM B803/B803M: High-strength zinc–5% aluminum-mischmetal alloy-coated steel core wire
• ASTM B957/B957M and B958/B958M: Extra-high and ultra-high-strength metallic coated options
• ASTM E83: Practice for verification and classification of extensometer systems

Practical Value

Adherence to ASTM B500/B500M-24 ensures that metallic coated and aluminum clad stranded steel cores meet internationally recognized quality, strength, and manufacturing standards. Utilities, cable manufacturers, and infrastructure planners can rely on this specification to enhance the safety, reliability, and longevity of overhead electrical conductors, minimizing maintenance and maximizing operational uptime.

Keywords: metallic coated steel wire strand, steel core wire strand, aluminum clad, ACSR, overhead electrical conductors, ASTM B500/B500M-24, galvanized steel, alloy-coated steel wire.

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: B500/B500M − 24
Standard Specification for
Metallic Coated or Aluminum Clad Stranded Steel Core for
Use in Overhead Electrical Conductors
This standard is issued under the fixed designation B500/B500M; 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 B803/B803M Specification for High-Strength Zinc–5 %
Aluminum-Mischmetal Alloy-Coated Steel Core Wire for
1.1 This specification covers 7-wire, 19-wire, 37-wire, and
Use in Overhead Electrical Conductors
61-wire zinc-coated (galvanized), zinc-5 % aluminum-
B957/B957M Specification for Extra-High-Strength and
mischmetal alloy-coated or aluminum clad stranded steel core
Ultra-High-Strength Zinc-Coated (Galvanized) Steel Core
intended for use in overhead electrical conductors.
Wire for Use in Overhead Electrical Conductors
1.2 The values stated in either SI units or inch-pound units
B958/B958M Specification for Extra-High-Strength and
are to be regarded separately as standard. The values stated in
Ultra-High-Strength Class A Zinc–5% Aluminum-
each system may not be exact equivalents; therefore, each
Mischmetal Alloy-Coated Steel Core Wire for Use in
system shall be used independently of the other. Combining
Overhead Electrical Conductors
values from the two systems may result in non-conformance
E83 Practice for Verification and Classification of Exten-
with the standard.
someter Systems
1.3 This international standard was developed in accor-
3. Terminology
dance with internationally recognized principles on standard-
3.1 Definitions of Terms Specific to This Standard:
ization established in the Decision on Principles for the
3.1.1 lot, n—unless otherwise specified in the contract or
Development of International Standards, Guides and Recom-
order, a lot shall consist of all coils or reels of strand of the
mendations issued by the World Trade Organization Technical
same diameter and unit lengths submitted for inspection at the
Barriers to Trade (TBT) Committee.
same time.
2. Referenced Documents
3.1.2 production lot, n—all of the wire spools loaded into a
2.1 ASTM Standards: stranding machine that are used to produce a completed strand
B498/B498M Specification for Zinc-Coated (Galvanized)
cable.
Steel Core Wire for Use in Overhead Electrical Conduc-
4. Ordering Information
tors
4.1 Orders for material under this specification shall include
B502/B502M Specification for Aluminum-Clad Steel Core
the following information:
Wire for Use in Overhead Electrical Aluminum Conduc-
4.1.1 Length of each construction,
tors
4.1.2 Constructional description of stranded core (for
B606/B606M Specification for High-Strength Zinc-Coated
example, 7 × 0.0943 in. or 19 × 0.0977 in.) (8.1 and 8.2),
(Galvanized) Steel Core Wire for Use in Overhead Elec-
4.1.3 The multiple length of stranded core and the total
trical Conductors
number of multiple lengths per reel, if allowed (8.3 and Section
B802/B802M Specification for Zinc–5 % Aluminum-
15),
Mischmetal Alloy-Coated Steel Core Wire for Use in
4.1.4 Strength and coating type or aluminum clad (Section
Overhead Electrical Conductors
8),
4.1.5 Direction of lay of outer layer (Section 7),
This specification is under the jurisdiction of ASTM Committee B01 on
4.1.6 Packaging (Section 15), and
Electrical Conductors and is the direct responsibility of Subcommittee B01.05 on
4.1.7 Place of inspection (Section 13).
Conductors of Ferrous Metals.
Current edition approved April 1, 2024. Published April 2024. Originally
5. Material
approved in 1969. Last previous edition approved in 2022 as B500/B500M – 22.
DOI: 10.1520/B0500_B0500M-24.
5.1 The coated or aluminum clad steel wire used in the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
production of the stranded core shall, prior to stranding, meet
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
all of the requirements of the appropriate specification that
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. follows:
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B500/B500M − 24
5.1.1 Specification B498/B498M, 8.3 Recommended standard unit-stranded-core multiple
5.1.2 Specification B606/B606M, lengths are given in respective ASTM Conductor Standards.
5.1.3 Specification B802/B802M,
5.1.4 Specification B803/B803M, 9. Length Tolerance
5.1.5 Specification B957/B957M,
9.1 All lengths of stranded core shall be furnished to a
5.1.6 Specification B958/B958M, and
length tolerance of 62 %.
5.1.7 Specification B502/B502M.
10. Tensile Properties
6. Joints
10.1 The rated ultimate strength or strength at 1 % exten-
6.1 There shall be no joints of any kind made in the finished
sion of stranded core for overhead electrical conductors shall
zinc-coated, zinc-5 % aluminum-mischmetal alloy-coated or
be taken as that percentage according to the number of wires,
aluminum clad steel wires.
indicated below, of the sum of the strengths of the steel wires,
7. Lay
calculated from their specified nominal wire diameter and the
appropriate specified minimum stress at 1 % extension or
7.1 The lay length of the 6-wire layer shall not be less than
ultimate strength given in Specifications B498/B498M, B606/
16 nor more than 26 times the outside diameter of the 6-wire
B606M, B802/B802M, B803/B803M, B957/B957M, B958/
layer. (Outside diameter is three times nominal wire diameter.)
B958M or B502/B502M:
7.2 For construction containing 19 or more wires, the lay
7 2 wire strand 2 96 % of sum of components
length of the 12-wire layer shall not be less than 14 nor more
than 22 times the outside diameter of the 12-wire layer.
19 2 wire strand 2 93 % of sum of components
(Outside diameter is five times nominal wire diameter.)
37 2 wire strand 2 91 % of sum of components
7.3 For construction containing 37 or more wires, the lay
61 2 wire strand 2 90 % of sum of components
length of the 18-wire layer shall not be less than 14 nor more
10.2 Stranded steel core samples shall sustain loads equal to
than 20 times the outside diameter of the 18-wire layer.
or greater than the values computed by the method of 10.1.
(Outside diameter is seven times nominal wire diameter.)
Compliance can be shown either by testing the completed
7.4 For construction containing 61 wires, the lay length of
strand or by calculation using the strand’s individual wire
the 24-wire layer shall not be less than 14 nor more than 18
properties (for example, ultimate strength or stress at 1 %
times the outside diameter of the 24-wire layer. (Outside
extension). When calculating the strand strengths using the
diameter is nine times nominal wire diameter.)
strand’s individual wire properties, it shall be computed as the
7.5 The lay length of an
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: B500/B500M − 22 B500/B500M − 24
Standard Specification for
Metallic Coated or Aluminum Clad Stranded Steel Core for
Use in Overhead Electrical Conductors
This standard is issued under the fixed designation B500/B500M; 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
1.1 This specification covers 7-wire, 19-wire, 37-wire, and 61-wire zinc-coated (galvanized), zinc-5 % aluminum-mischmetal
alloy-coated or aluminum clad stranded steel core intended for use in overhead electrical conductors.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
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.
2. Referenced Documents
2.1 ASTM Standards:
B498/B498M Specification for Zinc-Coated (Galvanized) Steel Core Wire for Use in Overhead Electrical Conductors
B502/B502M Specification for Aluminum-Clad Steel Core Wire for Use in Overhead Electrical Aluminum Conductors
B606/B606M Specification for High-Strength Zinc-Coated (Galvanized) Steel Core Wire for Use in Overhead Electrical
Conductors
B802/B802M Specification for Zinc–5 % Aluminum-Mischmetal Alloy-Coated Steel Core Wire for Use in Overhead Electrical
Conductors
B803/B803M Specification for High-Strength Zinc–5 % Aluminum-Mischmetal Alloy-Coated Steel Core Wire for Use in
Overhead Electrical Conductors
B957/B957M Specification for Extra-High-Strength and Ultra-High-Strength Zinc-Coated (Galvanized) Steel Core Wire for Use
in Overhead Electrical Conductors
B958/B958M Specification for Extra-High-Strength and Ultra-High-Strength Class A Zinc–5% Aluminum-Mischmetal Alloy-
Coated Steel Core Wire for Use in Overhead Electrical Conductors
E83 Practice for Verification and Classification of Extensometer Systems
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
This specification is under the jurisdiction of ASTM Committee B01 on Electrical Conductors and is the direct responsibility of Subcommittee B01.05 on Conductors
of Ferrous Metals.
Current edition approved May 1, 2022April 1, 2024. Published May 2022April 2024. Originally approved in 1969. Last previous edition approved in 20182022 as
B500/B500M – 12 (2018).B500/B500M – 22. DOI: 10.1520/B0500_B0500M-22.10.1520/B0500_B0500M-24.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B500/B500M − 24
3.1.1 lot—lot, n—unless otherwise specified in the contract or order, a lot shall consist of all coils or reels of strand of the same
diameter and unit lengths submitted for inspection at the same time.
3.1.2 production lot—lot, n—all of the wire spools loaded into a stranding machine that are used to produce a completed strand
cable.
4. Ordering Information
4.1 Orders for material under this specification shall include the following information:
4.1.1 Length of each construction,
4.1.2 Constructional description of stranded core (for example, 7 × 0.0943 in. or 19 × 0.0977 in.) (8.1 and 8.2),
4.1.3 The multiple length of stranded core and the total number of multiple lengths per reel, if allowed (8.3 and Section 15),
4.1.4 Strength and coating type or aluminum clad (Section 8),
4.1.5 Direction of lay of outer layer (Section 7),
4.1.6 Packaging (Section 15), and
4.1.7 Place of inspection (Section 13).
5. Material
5.1 The coated or aluminum clad steel wire used in the production of the stranded core shall, prior to stranding, meet all of the
requirements of the appropriate specification that follows:
5.1.1 Specification B498/B498M,
5.1.2 Specification B606/B606M,
5.1.3 Specification B802/B802M,
5.1.4 Specification B803/B803M,
5.1.5 Specification B957/B957M,
5.1.6 Specification B958/B958M, and
5.1.7 Specification B502/B502M.
6. Joints
6.1 There shall be no joints of any kind made in the finished zinc-coated, zinc-5 % aluminum-mischmetal alloy-coated or
aluminum clad steel wires.
7. Lay
7.1 The lay length of the 6-wire layer of 7 and 19-wire stranded core shall be not shall not be less than 16 ornor more than 26
times the outside diameter of the 6-wire layer. (Outside diameter is three times nominal wire diameter.)
7.2 The For construction containing 19 or more wires, the lay length of the 12-wire layer of a 19-wire stranded core shall be not
shall not be less than 14 ornor more than 22 times the outside diameter of the 12-wire layer. (Outside diameter is five times nominal
wire diameter.)
B500/B500M − 24
7.3 The For construction containing 37 or more wires, the lay length of the 18-wire layer of a 37-wire stranded core shall be not
shall not be less than 14 ornor more than 20 times the outside diameter of the 18-wire layer. (Outside diameter is seven times
nominal wire diameter.)
7.4 The For construction containing 61 wires, the lay length of the 24-wire layer of a 61-wire stranded core shall be not shall not
be less than 14 ornor more than 18 times the outside diameter of the 24-wire layer. (Outside diameter is nine times nominal wire
diameter.)
7.5 The lay length of any steel layer shall not be less than the lay length of the steel layer immediately beneath it.
7.6 The steel wires shall be so stranded that when the stranded core is cut the individual wires can be readily regrouped and then
held in place by one hand.
7.7 For construction containing 19 or more wires, the direction of lay will alternate with each layer.
7.8 The direction of lay of the outer layer shall be as specified by the purchaser at the time of placing the order.
8. Construction and Recommended Standard Stranded-Core Lengths
8.1 Overhead Electrical Conductors may be constructed using steel core wire with any one of the protective coatings or aluminum
clad and associated strength grades. The acceptable core wires are produced to ASTM Specifications shown in Section 5 of this
standard.
8.2 The number and diameters of the steel wires shall conform to the requirements in respective ASTM Conductor Standards.
8.3 Recommended standard unit-stranded-core multiple lengths are given in respective ASTM Conductor Standards.
9. Length Tolerance
9.1 All lengths of stranded core shall be furnished to a length tolerance of 62 %.
...