T5
Cooled from the press and artificially aged. Good balance of conductivity and stiffness, lowest cost, and the temper most extruders stock for busbar.
Electrical flat bar guide
6063 Aluminium Busbar and Electrical Flat Bar
6063 busbar is an extruded aluminium flat bar that trades a little conductivity (about 53 – 58 % IACS depending on temper) for a smooth surface, tight dimensions and easy bending. It is the practical choice for panel, switchgear and inverter busbars where currents are moderate and appearance or plating quality matters. This guide explains tempers, conductivity, sizing and how to specify it.
- Alloy
- 6063 (EN AW-6063, A96063)
- Tempers
- O, T4, T5, T6, T66
- Conductivity
- ≈ 53 – 58 % IACS
- Standards
- ASTM B221 · EN 755-2 · EN 755-5
Why 6063 is used for busbar
A busbar has two jobs: carry current with acceptable temperature rise, and hold its shape between supports. Pure aluminium grades such as 1350 and 1060 do the first job best; 6063 does the second job better while keeping roughly 85 – 95 % of their conductivity.
6063 is the most extruded aluminium alloy in the world, which matters for busbar buyers in three ways. First, almost any rectangular section with square or radiused edges can be produced from an existing die, so tooling cost is rarely an issue. Second, 6063 leaves the press with a very clean, uniform surface, which gives consistent results when the bar is tin- or silver-plated at the joints. Third, it bends and punches readily, so one bar can be formed into the offsets and risers a compact panel needs.
The trade-off is conductivity. The magnesium and silicon that make 6063 heat-treatable also scatter electrons, so a 6063-T6 bar has noticeably higher resistance than a 1350 bar of the same size. For a busbar this means a slightly larger cross-section or a slightly lower current rating. Where the bar must carry very high current with minimal losses, 6101 or 1350 is usually the better choice; where moderate current, rigidity and finish matter, 6063 is hard to beat on cost.
6063 chemical composition (wt %)
Limits below are the registered Aluminum Association values, followed by ASTM B221 and EN 573-3 (EN AW-6063, AlMg0.7Si). For electrical bar, producers aim for the lower end of the iron and the transition elements (Mn, Cr, Ti), because each of these lowers conductivity more strongly than magnesium and silicon do.
| Element | Minimum | Maximum | Effect on a busbar |
|---|---|---|---|
| Silicon (Si) | 0.20 | 0.60 | Forms Mg2Si with magnesium; excess Si in solution lowers conductivity |
| Iron (Fe) | — | 0.35 | Impurity; kept low for conductivity and surface quality |
| Copper (Cu) | — | 0.10 | Impurity |
| Manganese (Mn) | — | 0.10 | Strong conductivity penalty; kept low in electrical bar |
| Magnesium (Mg) | 0.45 | 0.90 | Main strengthening element with Si |
| Chromium (Cr) | — | 0.10 | Strong conductivity penalty; kept low |
| Zinc (Zn) | — | 0.10 | Impurity |
| Titanium (Ti) | — | 0.10 | Grain refiner; minimised in conductor grades |
| Others, each / total | — | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder | About 98.5 – 99.3 % |
Conductivity and strength of 6063 by temper
Conductivity and strength move in opposite directions. Ageing to peak strength (T6) precipitates Mg2Si finely, which raises strength but leaves more solute in the matrix than an over-aged or annealed bar. The figures below are typical values for planning; the mill certificate reports the measured conductivity for each lot.
| Temper | Typical conductivity | Typical resistivity at 20 °C | What it is used for |
|---|---|---|---|
| 6063-O | ≈ 58 % IACS (≈ 34 MS/m) | ≈ 29.7 nΩ·m | Heavily formed parts; low strength |
| 6063-T5 | ≈ 55 % IACS (≈ 32 MS/m) | ≈ 31.3 nΩ·m | Common general busbar temper |
| 6063-T6 | ≈ 53 % IACS (≈ 31 MS/m) | ≈ 32.5 nΩ·m | Stiffer bar, long spans, bolted joints |
Minimum mechanical properties for extruded bar are set by EN 755-2 (and ASTM B221 in the US). The values below are the EN 755-2 minimums for 6063 bar and profiles; design to these, not to the higher typical values.
| Temper | Thickness | Tensile Rm min | Yield Rp0.2 min | Elongation A min |
|---|---|---|---|---|
| T4 | ≤ 25 mm | 130 MPa | 65 MPa | 14 % |
| T5 | ≤ 3 mm | 175 MPa | 130 MPa | 8 % |
| T5 | 3 – 25 mm | 160 MPa | 110 MPa | 7 % |
| T6 | ≤ 10 mm | 215 MPa | 170 MPa | 8 % |
| T6 | 10 – 25 mm | 195 MPa | 160 MPa | 8 % |
| T66 | ≤ 10 mm | 245 MPa | 200 MPa | 8 % |
Some sellers advertise "6063" busbar at 65 % IACS. No 6063 bar can reach that: even unalloyed EC aluminium (1350) is specified at 61.0 – 61.8 % IACS. Treat any claim above about 58 % IACS for 6063 with suspicion and ask for a measured certificate.
Physical properties (T6)
- Density
- 2.69 – 2.70 g/cm³
- Thermal conductivity
- About 200 W/m·K
- Coefficient of thermal expansion
- 23.4 µm/m·°C (20 – 100 °C)
- Modulus of elasticity
- 68.9 GPa
- Melting range
- About 615 – 655 °C
Which temper should you specify?
T6
Solution treated (often on the press) and aged to peak strength. Choose it for bars that span long distances between insulators, carry heavy short-circuit forces or are bolted at high torque.
T4
Naturally aged and relatively soft. Useful when the bar will be bent tightly and then aged to T6, or when maximum formability is needed.
T66
A higher-strength 6063 variant from tighter chemistry control. Rarely needed for busbar; it costs conductivity.
O
Fully annealed. Highest conductivity of the 6063 tempers but too soft for most self-supporting bars; used for flexible links and shaped connectors.
Over-aged tempers
Some buyers ask for a bar aged past peak strength to recover a few points of conductivity. Agree the target conductivity and minimum strength in writing before ordering.
Common 6063 busbar sizes, weight and resistance
Flat busbar is usually specified as thickness × width in millimetres. The table gives the cross-section, mass per metre (density 2.70 g/cm³) and calculated DC resistance per metre at 20 °C for 6063-T6 at 53 % IACS. AC resistance is higher because of skin effect, particularly for thick bars at 50/60 Hz.
| Size t × w (mm) | Area (mm²) | Mass (kg/m) | DC resistance (µΩ/m) |
|---|---|---|---|
| 3 × 25 | 75 | 0.203 | 433.7 |
| 4 × 40 | 160 | 0.432 | 203.3 |
| 5 × 30 | 150 | 0.405 | 216.9 |
| 5 × 50 | 250 | 0.675 | 130.1 |
| 6 × 60 | 360 | 0.972 | 90.4 |
| 8 × 80 | 640 | 1.728 | 50.8 |
| 10 × 50 | 500 | 1.350 | 65.1 |
| 10 × 80 | 800 | 2.160 | 40.7 |
| 10 × 100 | 1000 | 2.700 | 32.5 |
| 12 × 120 | 1440 | 3.888 | 22.6 |
| 15 × 150 | 2250 | 6.075 | 14.5 |
| 20 × 200 | 4000 | 10.800 | 8.1 |
To compare with other conductors, use resistance per metre rather than area. For equal DC resistance, a 6063-T6 bar needs about 1.9 times the cross-section of a copper bar and about 1.15 times that of a 1350 bar, yet it still weighs only about 57 % as much as the copper bar. Final current ratings should be confirmed by temperature-rise testing of the assembly, for example under IEC 61439-1.
Production routes and supply range
Typical supply range
- Thickness
- About 2 – 40 mm for extruded flat bar; thicker on request
- Width
- About 10 – 200 mm extruded; wider bars sawn from plate
- Length
- Mill lengths up to about 6 m, or cut to length
- Edges
- Square, radiused corners or full-round edges
- Tolerances
- EN 755-5 (rectangular bar) or ASTM B221 / ANSI H35.2; tighter on request
- Packing
- Bundles with interleaving, wooden cases for plated or finished bar
Extruded flat bar
The normal route. A standard die gives consistent dimensions and a smooth surface; best value on any meaningful quantity.
Sawn from plate
For widths beyond the extrusion range, very thick sections or small quantities of odd sizes. Edges are machined rather than extruded.
Radiused-edge bar
Rounded corners reduce local electric-field concentration and make plating and insulation sleeving more reliable.
Fabricated busbar
Cut, punched, drilled, bent and plated to drawing so the bar arrives ready to install.
Bending, joining and surface treatment
Bending
Flatwise bends in T5/T6 normally need an inside radius of about 1 × thickness for bars up to 12 mm and 2 × thickness above that; edgewise bends need more. Run a trial bend on the first lot.
Punching and drilling
6063 punches cleanly. Deburr holes at joints, because burrs reduce contact area and raise joint resistance.
Bolted joints
Aluminium creeps under constant clamp load. Use Belleville (conical) washers or wide flat washers, contact grease and the torque from your joint design, and avoid plain spring washers.
Plating
Tin plating is the usual joint finish; silver for high-current or high-temperature joints; nickel where hardness and corrosion resistance matter. Plating needs a zincate or similar pre-treatment on aluminium.
Copper connections
Never bolt bare aluminium straight to bare copper in damp conditions. Use plated surfaces, bimetallic washers or copper-clad aluminium transition pieces.
Insulation
Epoxy powder coating, heat-shrink sleeving or insulating paint are applied after fabrication for touch-safe or compact layouts.
6063 compared with other aluminium busbar grades
| Grade | Typical conductivity | Strength | Best use |
|---|---|---|---|
| 1350 / 1370 | 61 – 62 % IACS | Low | Maximum conductivity, heavy-current runs |
| 1060 | ≈ 61 % IACS | Low | Rolled and extruded high-conductivity bar |
| 6101-T6 / T61 / T63 | 55 – 59.5 % IACS (specified) | Medium | Bus conductors needing strength and guaranteed conductivity |
| 6060-T5 / T6 | ≈ 54 – 57 % IACS | Medium-low | European extruded busbar |
| 6063-T5 / T6 | ≈ 53 – 55 % IACS | Medium | Panel and switchgear bar, good finish |
| 6082-T6 | ≈ 42 % IACS | High | Structural busbar, long spans, heavy loads |
In short: choose 1350 when every watt of loss matters, 6101 when you need conductivity guaranteed by ASTM B317, 6063 for general panel work, and 6082 only when the bar is also a structural member.
How to specify 6063 busbar
- Define the sectionThickness, width, edge shape and length, or a drawing of the fabricated bar.
- State temper and conductivityFor example "6063-T5, conductivity ≥ 55 % IACS measured at 20 °C". Stating the minimum conductivity is more useful than the temper alone.
- Add finish and processingPlating type and thickness, insulation, holes and bends.
- Agree tests and documentsConductivity, tensile and bend tests as required; mill test certificate to EN 10204 3.1.
- Confirm delivery termsEXW, FOB, CIF or DAP, with export packing suited to the finish.
References and standards
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- EN 755-2 – Extruded rod/bar, tube and profiles: mechanical properties
- EN 755-5 – Extruded rectangular bar: tolerances on dimensions and form
- IEC 61439-1 – Low-voltage switchgear and controlgear assemblies: general rules
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits
6063 aluminium (aluminum) busbar: FAQ
What is the conductivity of 6063 busbar?
Typically about 55 % IACS in T5 and about 53 % IACS in T6, roughly 31 – 32 MS/m. Annealed 6063 reaches about 58 % IACS. Ask for the measured value on the mill certificate if your design depends on it.
Is 6063 or 6101 better for busbar?
6101 is the dedicated conductor alloy: ASTM B317 guarantees minimum conductivity (55 – 59.5 % IACS by temper). 6063 is cheaper, more widely extruded and has a better surface, but its conductivity is not guaranteed by its product standard. Use 6101 when conductivity is a contractual requirement.
Can 6063 busbar be bent?
Yes. In T5 or T6, flatwise bends with an inside radius of about one thickness are normal for bars up to 12 mm. For tighter bends, form in T4 and age afterwards.
Does 6063 busbar need plating?
Not for the bar body, which forms a protective oxide film. Joint surfaces are commonly tin- or silver-plated, or cleaned and greased just before assembly, to keep contact resistance low and stable.
How much does a 6063 busbar weigh?
Multiply thickness × width (mm) × 0.0027 to get kg per metre. A 10 × 100 mm bar weighs about 2.7 kg/m, compared with about 8.9 kg/m for copper of the same size.
Do you supply 6063 busbar outside India?
Yes. Metline ships busbar worldwide from Mumbai with mill test certificates and export packing.
Need 6063 busbar cut, punched or plated?
Send the section, temper, conductivity target, finish and quantity, and we will reply with a clear quotation.
