Aluminium square tube standard sizes

Standard sizes typically range from 10mm x 10mm to 200mm x 200mm, with wall thicknesses varying from 1mm to 10mm. For general structural use, 6061-T6 is the industry standard due to its excellent strength-to-weight ratio and weldability. For architectural or decorative purposes where a superior surface finish is required, 6063-T5 is the preferred choice. Always specify the temper (e.g., T5 or T6) as it significantly impacts the mechanical properties and hardness of the tube.

B2B buyers should demand compliance with ASTM B221 or EN 755-9 standards, which define the allowable deviations in wall thickness, twist, and straightness. For high-precision applications, request 'Precision Grade' tolerances rather than 'Standard Commercial' grades. Ensure the supplier uses calibrated calipers and ultrasonic thickness gauges during the Quality Control (QC) process to verify that the outer dimensions and inner hollows meet your exact blueprints.

Depending on the application, you should choose between Anodizing (Clear or Color), which provides a hard, wear-resistant layer, and Powder Coating, which offers a wide range of RAL colors and UV protection. For marine environments, a micron thickness of 15-25μm for anodizing is essential. If the tubes are for structural frames, a Mill Finish is the most economical, but it is susceptible to surface oxidation if not stored in a dry environment.

Verify that the manufacturer holds ISO 9001:2015 certification for quality management. For construction projects in the EU, CE Marking and EN 1090-3 are mandatory. For US-bound goods, ensure the chemical composition aligns with AA (Aluminum Association) standards. Always request a Mill Test Certificate (MTC) for every batch to verify the chemical breakdown (Silicon, Magnesium, Iron levels) and mechanical test results (Tensile Strength, Yield Strength).

Aluminium is prone to surface scratching and bending. Insist on protective plastic film (PE film) on each tube and wooden crate packaging rather than simple bundles. For LCL (Less than Container Load) shipments, specify that no heavy goods should be stacked on top of the aluminium profiles. Including moisture-absorbent silica gel packs in the packaging is also recommended to prevent 'white rust' caused by condensation during long sea voyages.

Aluminium pricing is usually calculated as: LME (London Metal Exchange) Base Price + Fabrication Cost. To secure the best deal, negotiate a fixed fabrication fee and ask the supplier to provide a quote based on the LME price of the day the deposit is paid. For large-scale annual procurement, consider a formula-based pricing contract to protect both parties from sudden market spikes.

Prioritize 'Audited Suppliers' on Made-in-China.com, as these companies have undergone on-site inspections by third-party agencies like SGS or TÜV Rheinland. Review their Audit Reports to check their actual production capacity and specialized equipment (e.g., extrusion presses, CNC machines). It is highly recommended to use STS (Secured Trading Service) to ensure your payment is only released after you confirm receipt and quality of the goods.

Be aware that many countries (including the US and EU) have imposed Anti-Dumping (AD) and Countervailing Duties (CVD) on aluminium extrusions from specific regions. Before finalizing an order, check your local Harmonized System (HS) Code (typically 7604.21 or 7604.29) against current trade barriers. Consult with a professional customs broker to determine if additional tariffs apply, which could significantly impact your landed cost.