Intermediate-strength aluminium alloy wire sits between pure electrical-grade 1350 wire and high-strength 6201 alloy: it is noticeably stronger than 1350 while keeping conductivity close to 57 – 58.5 % IACS. It is used to build all-alloy conductors that need more span or sag performance than AAC without the resistance penalty of standard AAAC. Metline supplies the full family of overhead conductor wires and stranded AAC, AAAC, ACSR and ACAR conductors to ASTM, IEC, EN and BS standards, worldwide.
Every overhead conductor is a compromise between conductivity and strength. Pure aluminium (1350) conducts best but is relatively weak; heat-treated Al-Mg-Si alloy (6201-T81) is twice as strong but loses about 15 % of its conductivity. Intermediate-strength alloys fill the gap between the two.
They are aluminium-magnesium-silicon (6101-type) or iron-bearing compositions with lower alloy content than 6201, processed so that more of the magnesium and silicon stay out of solid solution. The result is a wire with tensile strength typically in the range of about 230 – 290 MPa and conductivity of 57 – 58.5 % IACS, depending on the class and diameter. Some national standards define two classes on exactly those conductivity floors; IEC 62641:2022 also added further alloy designations to the international system alongside the established 1350 and 6201 types.
For a utility, the practical gain is a conductor that runs cooler and with lower losses than standard AAAC at the same current, while keeping much of AAAC's span and sag capability and its freedom from a steel core. That makes it attractive for distribution feeders and sub-transmission lines where both energy losses and pole or tower spacing matter.
| Wire type | Typical tensile strength | Minimum conductivity | Main use |
|---|---|---|---|
| 1350-H19 (hard-drawn EC) | about 160 – 200 MPa | 61.0 % IACS | AAC, aluminium layers of ACSR and ACAR |
| Intermediate-strength alloy | about 230 – 290 MPa | 57.0 – 58.5 % IACS | Low-loss all-alloy conductors, ACAR-type designs |
| 6201-T81 (high-strength AAAC) | about 305 – 330 MPa | 52.5 % IACS | AAAC, reinforcing core of ACAR |
| Galvanised steel core wire | 1,300 – 1,900 MPa (by grade) | about 8 – 9 % IACS | Strength member of ACSR |
Tensile figures are indicative; the specified minimum for each wire depends on diameter and is set by the governing standard (for example ASTM B230 for 1350-H19 and ASTM B398 for 6201-T81).
Concentric strands of 1350-H19 only (ASTM B231, IEC 61089 A1). Highest conductivity per unit area and the lowest cost per amp, but limited strength. Best for short urban spans, substation buses and coastal sites where steel would corrode.
Strands of 6201-T81 or equivalent heat-treated alloy (ASTM B399, EN 50182). Roughly twice the strength of AAC, a hard surface that resists damage, and no galvanic couple. A common replacement for ACSR on distribution and sub-transmission lines.
1350 layers around a galvanised or aluminium-clad steel core (ASTM B232, EN 50182). The highest strength-to-cost ratio for long spans, river crossings and heavy ice, at the cost of extra weight and some corrosion risk in the core.
1350 outer layers around a 6201 alloy core (ASTM B524). Better conductivity than AAAC and better strength than AAC, with no steel. The mix of wires can be tuned for a given strength-to-resistance target.
Intermediate-strength wire is used either as a single-material all-alloy conductor, giving a low-loss alternative to AAAC, or in combination with 1350 wires in ACAR-style constructions. When you compare offers, ask for rated tensile strength, DC resistance at 20 °C and mass per kilometre for each option, rather than relying on conductor names alone.
| Property | 1350-H19 | Intermediate-strength alloy | 6201-T81 |
|---|---|---|---|
| Density at 20 °C | 2.703 g/cm³ | 2.703 g/cm³ | 2.690 – 2.703 g/cm³ |
| Resistivity at 20 °C (max.) | 28.264 nΩ·m | about 29.5 – 30.2 nΩ·m | 32.840 nΩ·m |
| Temperature coefficient of resistance | 0.00403 /°C | about 0.0038 /°C | 0.00347 – 0.0036 /°C |
| Coefficient of linear expansion | 23 × 10⁻⁶ /°C | 23 × 10⁻⁶ /°C | 23 × 10⁻⁶ /°C |
| Modulus of elasticity (single wire) | about 68 GPa | about 68 GPa | about 69 GPa |
| Typical continuous operating temperature | 75 – 90 °C | 80 – 90 °C | 80 – 90 °C |
North American conductors are sized in AWG or kcmil (1 kcmil = 0.5067 mm²) and identified by code words; IEC and EN sizes use metric areas. The tables give approximate values for common ASTM sizes; final data is taken from the conductor standard you specify.
| AAC size | Code word | Strands | Area (mm²) | Approx. mass (kg/km) |
|---|---|---|---|---|
| 1/0 AWG | Poppy | 7 | 53.5 | 148 |
| 3/0 AWG | Phlox | 7 | 85.0 | 234 |
| 336.4 kcmil | Tulip | 19 | 170.5 | 470 |
| 477 kcmil | Cosmos | 19 | 241.7 | 666 |
| 795 kcmil | Arbutus | 37 | 402.8 | 1111 |
| 1272 kcmil | Narcissus | 61 | 644.5 | 1786 |
| ACSR size | Code word | Stranding (Al/steel) | Total area (mm²) | Approx. mass (kg/km) | Approx. rated strength (kN) |
|---|---|---|---|---|---|
| 4/0 AWG | Penguin | 6/1 | 125.1 | 433 | 37.1 |
| 336.4 kcmil | Linnet | 26/7 | 198.4 | 689 | 62.7 |
| 477 kcmil | Hawk | 26/7 | 281.1 | 975 | 86.7 |
| 795 kcmil | Drake | 26/7 | 468.5 | 1,628 | 139 |
| Standard | Covers |
|---|---|
| ASTM B230 / B398 | Hard-drawn 1350-H19 wire; 6201-T81 alloy wire |
| ASTM B231 / B232 / B399 / B524 | AAC; ACSR; AAAC; ACAR concentric-lay conductors |
| IEC 62641:2022 | Aluminium and aluminium alloy wires for stranded conductors (replaces IEC 60104, IEC 60889 and IEC 62004) |
| IEC 61089 | Round-wire concentric-lay overhead conductors (A1, A2, A3, A1/S1A and related) |
| EN 50182 | European overhead line conductors of round wires |
| BS 215 / BS 3242 | Legacy British AAC/ACSR and AAAC tables, still cited in many tender documents |
| DIN 48201 | Legacy German conductor tables, still used in some regions |
Many tenders still name withdrawn national standards. That is not a problem as long as the governing document is stated clearly; the wire and conductor can be produced and tested to the cited tables.
It describes an alloy wire stronger than 1350-H19 (about 160 – 200 MPa) but weaker than 6201-T81 (about 305 – 330 MPa), with conductivity of roughly 57 – 58.5 % IACS instead of 52.5 % for 6201. It trades a little strength for noticeably lower resistance.
It is an all-alloy conductor, so it belongs to the AAAC family in construction, but the wire has higher conductivity and lower strength than standard 6201-T81 AAAC. Sag-tension calculations must use its own rated strength and modulus.
For long spans, large river or valley crossings, and heavy ice or wind loading, where the steel core's strength allows fewer or lower towers. In corrosive coastal sites and on short to medium spans, AAAC or intermediate-strength all-alloy conductors usually give a longer, maintenance-free life.
Metal is the largest part of the cost. Conductor prices are usually built from the LME aluminium price plus a regional premium, a conversion charge for drawing and stranding, drums and freight.
Conductor type and size (or wire alloy and diameter), governing standard, total length and length per drum, drum type, any grease requirement, inspection needs and the delivery destination.
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