According to GB/T 1179-2017 and GB/T 3428 standards, the qualification test of steel-cored aluminum stranded wire requires systematic verification of key items such as structural dimensions, mechanical properties, electrical properties, and galvanized layer quality to ensure that it meets design and operational requirements.
These two standards together constitute the core basis for judging the quality of steel-cored aluminum stranded wire: GB/T 1179-2017 specifies the overall technical conditions and test methods for the conductor, while GB/T 3428 focuses on the performance requirements of galvanized steel wire, especially providing specific indicators for tensile strength, elongation, and zinc layer quality.
The main testing process and qualification criteria are as follows:
Structural Dimension Inspection
Measure the total outer diameter of the stranded wire, the diameter of the aluminum single wire and the steel core, the pitch ratio, and the stranding direction (usually the outermost layer is right-hand Z-direction).
Use a micrometer or laser diameter gauge to ensure that the dimensional deviation is within ±1% of the nominal value. Good concentricity is required to avoid "lantern-like" or loose strand phenomena.
Mechanical Performance Testing (Core Measure: Total Tensile Strength (RTS))
Tensile tests are performed on a universal testing machine, with the loading rate controlled between 10 and 30 mm/min.
Acceptance Criteria: The measured total tensile strength (RTS) must not be lower than 95% of the nominal value, and there should be no slippage or end damage before fracture.
The fracture location should be recorded. If the fracture surface is within 1 cm of the fixture and does not meet the standard value, it can be retested (maximum 3 times).
Simultaneously, the stress, elastic modulus, and elongation at break at 1% elongation are measured for sag and tension design.
Electrical Performance Testing
The DC resistance at 20°C is measured using a four-terminal micro-ohmmeter to eliminate the influence of contact resistance.
Acceptance Criteria: The measured resistance value must not exceed 102% of the standard specified value, and the three-phase imbalance rate must be controlled within 2%.
Infrared thermal imaging can be used to assess operating temperature rise characteristics, indirectly reflecting conductivity efficiency.
Galvanized Layer Quality Inspection (Based on GB/T 3428)
Zinc Layer Adhesion Test: Tightly wrap the steel wire around a round bar of specified diameter for 8 turns, then unwrap and rewrap, checking for cracking or peeling.
Zinc Layer Weight Measurement: Use the copper sulfate etching method, requiring Class A or Class B corrosion resistance, with at least 4 etching cycles.
The zinc layer mass per unit area should be ≥86g/m² to ensure long-term corrosion resistance.
Surface and Process Inspection
Visually inspect the surfaces of the aluminum wire and steel core for smoothness, cracks, burrs, oxidation, or oil stains.
The stranding should be uniform and tight, without misalignment or loose strands. Joints should be rounded with a spacing greater than 15mm.
Other Specialized Tests (as required)
Winding Test: Verify the toughness of the single wire under repeated bending to prevent breakage during construction.
Fatigue and creep test: Simulate wind vibration and long-term load to evaluate service life, requiring a breakage rate of ≤0.5% after one million cycles.
