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Shape: round wire vs flat tape
Copper-clad steel selection guide, part 4 of 8
Rule: round first; above about 200 mm² consider flat. Based on IEEE 80-2013, DL/T 1312-2023, DL/T 2727-2023.
- Corrosion: at equal base material and copper content, round wire lasts roughly twice as long against corrosion as flat tape (estimating life in proportion to copper thickness) – because, at equal copper content, the layer on tape is only about half as thick (see the table below).
- Cost: round wire needs no rolling to shape after casting, and plating is not thinned at edges.
- Welding: the curved surface seats better in the mould; exothermic welds are more uniform.
- Where tape earns its place: at large cross-sections it is less stiff and easier to bend. A supplementary choice where the bending requirement is specific and the section exceeds 200 mm².
| What happens when round wire is rolled flat | Before | Copper after rolling | Loss of corrosion resistance |
|---|---|---|---|
| Ø14 / 0.6 mm → 30:4 aspect ratio (equal area, 34×4.5 mm) | 0.60 mm | 0.33 mm | > 40% |
| Ø14 / 0.8 mm → 30:4 | 0.80 mm | 0.44 mm | > 40% |
| Ø14 / 0.6 mm → 10:1 (equal area, 39.2×3.9 mm) | 0.60 mm | 0.30 mm | ≈ 50% |
| Ø14 / 0.8 mm → 10:1 | 0.80 mm | 0.39 mm | ≈ 50% |
Assumptions: total cross-section and copper cross-section unchanged, copper distributed uniformly around the flat section – the most favourable case for tape; in real rolling the broad faces thin more and the corners thicken, so the minimum local copper thickness is lower still. In all four cases the rolled product costs more than the original round wire. On life-cycle cost, tape is markedly poorer value than round wire.
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