What Aluminum Flat Bar Is
Aluminum flat bar is a rectangular solid section produced either by hot extrusion or by slitting and rolling from coil. It is supplied in straight lengths, usually 3 m to 6 m, in widths from about 10 mm to 300 mm and thicknesses from 3 mm to 100 mm. With a density of roughly 2.70 g/cm3, about one third that of steel, the profile lets designers build stiff, light structures without the weight penalty of a steel section.
The material is valued for three properties at once: low weight, useful strength after heat treatment or work hardening, and a natural oxide film that resists atmospheric and chemical attack. It machines cleanly, takes an anodised or painted finish, and can be welded or bolted into frames and brackets.
Alloy Grades, Tempers and Mechanical Properties
The alloy and temper decide performance more than the dimensions do. The table below lists common flat bar options and typical room-temperature properties in the longitudinal direction.
| Alloy and temper | Typical tensile strength | Typical yield strength | Characteristics and typical use |
|---|---|---|---|
| 1050A H14 | about 105 MPa | about 85 MPa | Very high ductility, excellent conductivity; bus bar and general fabrication |
| 5052 H32 | about 230 MPa | about 195 MPa | Good marine corrosion resistance and formability; tanks, panels, brackets |
| 5083 H116 | about 315 MPa | about 230 MPa | High strength in welded joints; hull structure, deck fittings, cryogenic work |
| 6061 T6 | about 310 MPa | about 275 MPa | Balanced strength and machinability; machined parts, frames, jigs |
| 6082 T6 | about 310 MPa | about 260 MPa | Higher manganese for thick sections; structural and transport work |
| 7075 T651 | about 570 MPa | about 505 MPa | Highest strength, lower corrosion resistance; highly loaded aerospace fittings |
Values are typical for standard product and move with thickness, because thicker sections quench more slowly during heat treatment. Where the design depends on a guaranteed minimum, the order should state the alloy, temper, and the mechanical property that must be certified on the inspection document.
Automotive and Commercial Vehicle Applications
Weight reduction is the main driver in road transport. Replacing a steel bracket or cross member with an aluminium flat bar of equal stiffness lowers unsprung mass, which improves ride and reduces fuel or battery consumption. In electric vehicles the same logic applies to battery enclosure frames, module supports, and mounting rails, where the profile is often machined into a channel before assembly.
Chassis brackets, suspension links, and body mounting plates.
Trailer and tipper body framing, where corrosion resistance extends service life on salted roads.
Battery pack frames and thermal management brackets, using 6061 or 6082 for strength with low weight.
Interior structural rails and seat frames, using 5xxx alloys for formability and weldability.
Aerospace, Rail and Marine Applications
In aviation, flat bar is used for fittings, ribs, floor supports, and equipment racks. The high-strength 7xxx series is selected where load per unit weight is critical, while 6xxx alloys cover general structure because they combine good strength with predictable machining and corrosion behaviour. Every aerospace part is traceable to a certified heat of material and to a specific temper.
In rail and marine work, the priorities shift to fatigue life, weld integrity, and resistance to salt water. The 5083 and 5052 alloys handle hull stiffeners, deck beams, stair treads, and walkway supports. For cryogenic service, certain 5xxx sections retain useful toughness at low temperature, which is why they appear in liquefied gas equipment and cold-box framing.
Construction, Electrical and General Fabrication
Architectural and industrial projects use flat bar for window reinforcement, handrails, cladding supports, and machine guarding. Anodised or powder-coated finishes keep the appearance stable outdoors without maintenance painting, and the light weight reduces the load on fixing points.
In electrical work, 1050A and 1350 grades are selected for bus bar and conductor supports because the low alloy content keeps electrical conductivity high. Fabricators then plate or tin the contact faces to control joint resistance.
Specification practice makes the difference between a successful job and a rejected one. State the alloy and temper, the finish, the thickness tolerance, and the length tolerance on the purchase order. Confirm the straightness requirement for long bars, because a bar that twists during extrusion can be difficult to clamp in a fixture. Finally, agree on the inspection document and the marking method, so that the material arriving on site can be matched to the certificate that accompanies it.
Frequently Asked Questions
Q: What is aluminum flat bar used for?
It is a general-purpose rectangular profile used for machined parts, brackets, frames, bus bar, truck and trailer structure, marine fittings, and jigs. Because it is supplied flat and straight, it can be cut to length, drilled, and welded with minimal preparation.
Q: What is the difference between 6061 and 6082 flat bar?
Both are heat-treatable magnesium-silicon alloys with similar strength in the T6 temper. 6082 has slightly higher manganese content, which improves strength in thicker sections, while 6061 is more widely available in a broader range of widths and is easier to source in small quantities.
Q: Which aluminum flat bar alloy is best for marine use?
The 5xxx series, particularly 5052 and 5083, is preferred for marine and offshore work because it combines good corrosion resistance in salt water with high fatigue strength. 5083 also retains useful strength in welded joints, which makes it suitable for hull and deck fittings.
Q: Is aluminum flat bar stronger than steel?
Per unit weight, yes. Aluminum weighs roughly one third as much as steel, so a bar of the same mass can be far thicker and stiffer. Per unit volume, structural steel grades still show higher yield strength, which is why aluminum parts are designed with larger sections rather than compared dimension by dimension.
Q: What tempers are available for aluminum flat bar?
Common tempers include O for forming work, H32 and H116 for work-hardened 5xxx alloys, and T6 or T651 for heat-treated 6xxx and 7xxx alloys. The temper determines strength, formability, and machinability, so it should be specified together with the alloy.
Q: Can aluminum flat bar be welded?
The 6xxx and 5xxx series are routinely welded with 4043 or 5356 filler wire. The 7xxx series based on zinc is generally not welded because it suffers heat-affected zone cracking, and it is instead joined mechanically.