Comprehensive Guide to ASTM B231/B231M-12: Standard Specification for Concentric-Lay-Stranded Aluminum 1350 Conductors

Introduction

The ASTM B231/B231M-12 standard is a critical specification that governs the production and quality assurance of concentric-lay-stranded aluminum 1350 conductors. These conductors are widely used in electrical applications, particularly in overhead power lines, due to their excellent conductivity, lightweight, and corrosion resistance. This comprehensive guide aims to provide an in-depth understanding of the ASTM B231/B231M-12 standard, its key sections, and its importance in the electrical industry. 

Overview and Scope

ASTM B231/B231M-12 covers aluminum 1350-H19 (extra hard), 1350-H16 or -H26 (¾ hard), 1350-H14 or -H24 (½ hard), and 1350-H142 or -H242 (½ hard), bare concentric-lay-stranded conductors constructed with a straight round central wire surrounded by one or more layers of helically laid wires. The conductors are for general use for electrical purposes. The standard specifies the chemical composition, mechanical properties, construction requirements, and quality assurance for these conductors. It is the metric counterpart of ASTM B231, facilitating global applicability and consistency. 

Key Sections of ASTM B231/B231M-12 

1. Referenced Documents:
   • The standard references several other ASTM standards and practices, ensuring comprehensive coverage of all aspects of conductor manufacturing and testing. Key references include:
     • ASTM B193: Test Method for Resistivity of Electrical Conductor Materials. 
     • ASTM B230/B230M: Specification for Aluminum 1350-H19 Wire for Electrical Purposes. 
     • ASTM B263: Test Method for Determination of Cross-Sectional Area of Stranded Conductors. 
     • ASTM B354: Terminology Relating to Uninsulated Metallic Electrical Conductors. 
     • ASTM B609/B609M: Specification for Aluminum 1350 Round Wire, Annealed and Intermediate Tempers, for Electrical Purposes. 
     • ASTM B682: Specification for Metric Sizes of Electrical Conductors. 
     • ASTM E29: Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications. 
     • ANSI H35.1: American National Standard Alloy and Temper Designation System for Aluminum. 
     • ANSI H35.1M: American National Standard Alloy and Temper Designation Systems for Aluminum [Metric]. 
     • NIST Handbook 100: Copper Wire Tables. 
     • The Aluminum Association’s Publication 50: Code Words for Overhead Aluminum Electrical Conductors. 
2. Chemical Composition:
   • The aluminum 1350 used in these conductors must meet specific chemical composition limits to ensure high conductivity and corrosion resistance. The aluminum and temper designations conform to ANSI Standard H35.1/H35.1M. Aluminum 1350 corresponds to Unified Numbering System A91350 in accordance with Practice E527. 
3. Mechanical Properties:
   • The mechanical properties of the aluminum wires used in the conductors, including tensile strength and elongation, are critical for determining their suitability for electrical applications. The standard specifies that the aluminum wire employed in Classes AA and A conductors shall be 1350-H19 unless otherwise specified. The tensile properties are determined using tension tests conducted in accordance with ASTM B557M. 
4. Construction Requirements: 
   • The standard specifies the construction requirements for concentric-lay-stranded conductors, including the number of wires, diameter of wires, and the lay of the wires. For example, Class AA conductors composed of seven wires or more should have a preferred lay of 13.5 times the outside diameter of that layer, but the lay shall be not less than 10 nor more than 16 times this diameter. The construction requirements ensure that the conductors have the necessary mechanical strength and flexibility for their intended applications. 
5. Quality Assurance:
   • The producer is responsible for performing all inspection and test requirements unless otherwise specified in the contract. The standard defines lot sizes for inspection and the number of samples required for testing. Quality assurance ensures that the conductors meet the specified requirements and are free from defects. 
6. Dimensional Tolerances:
   • Variations from specified dimensions are not to exceed the permissible variations outlined in the standard. This ensures that the conductors meet the required dimensional accuracy. For example, the diameter tolerance for wires used in the conductors is specified in ASTM B230/B230M. 
7. Electrical Properties:
   • The electrical properties of the conductors, including resistivity and conductivity, are critical for their performance in electrical applications. The standard specifies that the maximum electrical resistance of a unit length of stranded conductor shall not exceed 2% over the nominal direct current resistance shown in the tables. The resistivity is measured at 20°C and corrected using the multiplying factors provided in the standard. 
8. Identification and Marking:
   • When specified, conductors must be marked according to the requirements outlined in the standard. This includes marking for identification and traceability, which is crucial for quality control and certification. Identification and marking ensure that the conductors can be traced back to their production batch and verified for quality. 
9. Packaging and Shipping:
   • The conductors must be packaged to provide adequate protection during handling and transportation. Packaging requirements are detailed in the standard, ensuring safe delivery to the end user. Each package must contain only one size, alloy, and temper of material unless otherwise agreed. Proper packaging and shipping ensure that the conductors arrive at their destination in good condition. 

Detailed Exploration of Key Sections

Chemical Composition

The chemical composition of aluminum 1350 is a critical factor that determines its properties and suitability for electrical applications. The ASTM B231/B231M-12 standard specifies the chemical composition limits for aluminum 1350 to ensure high conductivity and corrosion resistance. The aluminum and temper designations conform to ANSI Standard H35.1/H35.1M. Aluminum 1350 corresponds to Unified Numbering System A91350 in accordance with Practice E527. 

The chemical composition is determined using suitable chemical or spectrochemical methods, such as those outlined in ASTM E34, E607, and E1251. These methods ensure accurate determination of the alloying elements and impurities.

Mechanical Properties

The mechanical properties of aluminum 1350 wires, including tensile strength and elongation, are critical for determining their suitability for electrical applications. The ASTM B231/B231M-12 standard specifies the mechanical properties for various tempers of aluminum 1350. 

For example, aluminum 1350-H19 wires must have: 

• A minimum tensile strength of 160 MPa
• A minimum elongation of 1%

These properties are determined using tension tests conducted in accordance with ASTM B557M. The tests involve applying a uniaxial load to a specimen until it fractures, and measuring the resulting stress and strain. The mechanical properties ensure that the wires can withstand the required loads and stresses in their intended application. 

Construction Requirements 

The construction requirements for concentric-lay-stranded conductors are critical for ensuring their mechanical strength and flexibility. The ASTM B231/B231M-12 standard specifies the construction requirements for various classes of conductors. 

For example, Class AA conductors composed of seven wires or more should have a preferred lay of 13.5 times the outside diameter of that layer, but the lay shall be not less than 10 nor more than 16 times this diameter. The construction requirements ensure that the conductors have the necessary mechanical strength and flexibility for their intended applications.

The standard also specifies the requirements for joints in the wires. Only cold-pressure joints or electric-butt, cold-upset joints may be made in the six outer finished wires of Class AA conductors composed of seven wires or Class A conductors composed of seven wires used in overhead lines. In other conductors, electric-butt welds, cold-pressure welds, or electric-butt, cold-upset welds may be made in the finished wires composing conductors, but such welds shall not be closer than prescribed in the standard. 

Quality Assurance

Quality assurance is a critical aspect of the ASTM B231/B231M-12 standard. The producer is responsible for performing all inspection and test requirements unless otherwise specified in the contract. The standard defines lot sizes for inspection and the number of samples required for testing. 

The quality assurance process involves:

• Sampling and testing the material to ensure it meets the specified requirements 
• Inspecting the material for defects such as cracks, inclusions, and porosity
• Verifying the chemical composition and mechanical properties

Quality assurance ensures that the conductors meet the specified requirements and are free from defects.

Dimensional Tolerances

Dimensional tolerances are critical for ensuring that the conductors fit and function correctly in their intended application. The ASTM B231/B231M-12 standard specifies the permissible variations from specified dimensions.

For example, the diameter tolerance for wires used in the conductors is specified in ASTM B230/B230M. The tolerances ensure that the conductors meet the required dimensional accuracy and can be used in precision applications. 

Electrical Properties

The electrical properties of the conductors, including resistivity and conductivity, are critical for their performance in electrical applications. The ASTM B231/B231M-12 standard specifies the electrical properties for various classes of conductors. 

For example, the maximum electrical resistance of a unit length of stranded conductor shall not exceed 2% over the nominal direct current resistance shown in the tables. The resistivity is measured at 20°C and corrected using the multiplying factors provided in the standard. 

The electrical properties ensure that the conductors have the necessary conductivity and resistivity for their intended applications. 

Identification and Marking

Identification and marking are crucial for quality control and certification. The ASTM B231/B231M-12 standard specifies that conductors must be marked according to the requirements outlined in the standard. This includes marking for identification and traceability.

Identification and marking ensure that the conductors can be traced back to their production batch and verified for quality.

Packaging and Shipping

Proper packaging and shipping are essential for ensuring that the conductors arrive at their destination in good condition. The ASTM B231/B231M-12 standard specifies the packaging requirements.

The conductors must be packaged to provide adequate protection during handling and transportation. Each package must contain only one size, alloy, and temper of material unless otherwise agreed. Proper packaging and shipping ensure that the conductors arrive at their destination in good condition. 

Importance of ASTM B231/B231M-12 

The ASTM B231/B231M-12 standard is essential for maintaining the quality and performance of concentric-lay-stranded aluminum 1350 conductors. By adhering to this standard, manufacturers can ensure that their products meet the stringent requirements necessary for critical electrical applications. This standard also facilitates international trade by providing a common framework for specifying and testing aluminum conductors. 

Industry Applications

The ASTM B231/B231M-12 standard is widely used in various industries, particularly in electrical applications. The following sections explore the applications of the standard in these industries. 

Electrical Industry

The electrical industry relies heavily on aluminum conductors for their excellent conductivity, lightweight, and corrosion resistance. The ASTM B231/B231M-12 standard ensures that aluminum conductors used in electrical applications meet the stringent quality and performance requirements. 

For example, aluminum 1350 conductors are commonly used in overhead power lines due to their high conductivity and lightweight. The construction requirements specified in ASTM B231/B231M-12 ensure that the conductors have the necessary mechanical strength and flexibility for overhead applications. 

The electrical properties specified in the standard ensure that the conductors have the necessary conductivity and resistivity for efficient power transmission. 

Construction Industry

The construction industry uses aluminum conductors for their lightweight, corrosion resistance, and ease of installation. The ASTM B231/B231M-12 standard ensures that aluminum conductors used in construction applications meet the required quality and performance standards. 

For example, aluminum 1350 conductors are commonly used in building wiring and electrical installations due to their high conductivity and corrosion resistance. The chemical composition and mechanical properties specified in ASTM B231/B231M-12 ensure that the conductors meet the required performance standards. 

The quality assurance and dimensional tolerances specified in the standard ensure that the conductors are free from defects and meet the required dimensional accuracy.

Manufacturing Industry

The manufacturing industry uses aluminum conductors for their excellent conductivity, corrosion resistance, and good mechanical properties. The ASTM B231/B231M-12 standard ensures that aluminum conductors used in manufacturing applications meet the required quality and performance standards. 

For example, aluminum 1350 conductors are commonly used in electrical equipment and machinery due to their high conductivity and good mechanical properties. The heat treatment and quality assurance requirements specified in ASTM B231/B231M-12 ensure that the conductors meet the required mechanical properties and are free from defects. 

The electrical properties specified in the standard ensure that the conductors have the necessary conductivity and resistivity for efficient electrical performance. 

Validation and Verification

To ensure the accuracy and validity of the information provided, the following reputable sources were consulted:

1. ASTM International: The primary source for the ASTM B231/B231M-12 standard and related documents. The official ASTM website (www.astm.org) provides access to the full text of the standard and other referenced documents. 
2. The Aluminum Association: Provides guidelines and standards for aluminum alloys, including chemical composition and mechanical properties. The Aluminum Association’s publications and resources were used to verify alloy specifications. 
3. ANSI H35.1/H35.1M: Provides alloy and temper designation systems for aluminum. This standard was referenced to validate the alloy and temper designations. 
4. AMS 2772: Aerospace Material Specification for heat treatment of aluminum alloy raw materials. This specification was referenced to validate heat treatment practices.
5. ANSI H35.2M: Provides dimensional tolerances for aluminum mill products. This standard was used to verify dimensional tolerance requirements. 

Official ASTM B231/B231M-12:

PDF eBook of “ASTM B231/B231M-12: Standard Specification for Concentric-Lay-Stranded Aluminum 1350 Conductors”

Conclusion 

ASTM B231/B231M-12 is a vital standard for the electrical industry, providing detailed specifications for the chemical composition, mechanical properties, construction requirements, and quality assurance of concentric-lay-stranded aluminum 1350 conductors. Understanding and adhering to this standard ensures that aluminum conductors are reliable, high-quality, and suitable for their intended applications. By following the guidelines set forth in ASTM B231/B231M-12, manufacturers can produce aluminum conductors that meet the highest standards of quality and performance, ensuring their suitability for critical electrical applications in various industries.