ASTM B231 governs bare concentric-lay-stranded conductors constructed from round aluminum 1350 wires for general electrical applications. Key features include:
Covers multiple tempers: H19 (extra hard), H16/H26 (¾ hard), H14/H24 (½ hard), and H142/H242 (½ hard).
Defines layered construction: Straight round central wire surrounded by one or more helically laid wire layers.
Electrical Units:
Resistivity: SI units are standard.
Other properties: Inch-pound units are standard; SI equivalents are approximate.
Material Standards:
Aluminum 1350 corresponds to UNS A91350 (per Practice E527).
Temper designations follow ANSI H35.1.
Metric Version:
Full metric companion standard B231M is available (Note 3).
Conductor Construction:
Mandatory central wire with concentric helical layers.
Specialized Designs:
Permits sealed conductors to prevent longitudinal water propagation, optionally with covers/insulation (Note 4).
Historical Clarification:
“EC Aluminum” designation was used prior to 1975 (Note 1).
Flexibility: Supports 4 temper grades for strength/formability optimization.
Reliability: Standardized layered design ensures mechanical integrity.
Environmental Protection: Sealed variants mitigate water ingress risks.
Global Compatibility: Dual-unit system and metric counterpart (B231M) facilitate international adoption.
Electrical Distribution Systems:
Overhead power lines, substation connections.
General Conductivity Applications:
Uninsulated electrical transmission where aluminum conductivity suffices.
Humid/Water-Prone Environments:
Sealed conductors (per Note 4) for rain-soaked regions or underground transitions.
Critical Notes from Image:
Exclusively for bare conductors unless sealed per special provisions.
Not intended for ACSR cores or fully insulated cables.
