Hot Rolled Carbon steel square tube 20x20x1.5mm ASTM A500 Grade B ERW Hollow Section 6m Mill Length

This 20 x 20 x 1.5 mm carbon steel square tube is rolled from slit hot rolled coil, formed on a precision ERW mill and welded along one corner only, so the section behaves as a single closed hollow shape rather than four separate plates. At 0.87 kg per metre it is the lightest practical size we run for frame work, and the wall is heavy enough to take a tapped fixing without crushing, which is the first thing buyers ask about at this weight.

The grade is ASTM A500 Grade B, the cold formed welded structural tubing specification used across North America for hollow sections carrying load. Yield is 46 ksi (317 MPa) minimum, well above the 33 ksi of the ERW mechanical tubing that is sometimes substituted on price. Each coil is checked for carbon and manganese before slitting, and the finished tube is straightened and cut to a 6 m mill length with square cut ends so it can go straight into a saw or a sleeve joint on site.

• Wall Kept Inside Tolerance: 1.5 mm nominal wall is held to plus or minus 10 percent, and the outside corner radius stays at twice the wall, so mating parts do not need reaming.
• Scarfed Inside Weld: The internal weld flash is removed to within 0.2 mm of the wall surface, which keeps the bore clear for cables, wiring and threaded inserts.
• True Hot Rolled Surface: Mill finish with a light protective oil, free of the roll marks and oxidation patches that appear when coil is stored under damp conditions.
• Straightness and Twist Control: Straightness is held to 1 mm per metre after rotary straightening, and twist is limited to 1 degree over 6 m so frames square up on the jig first time.
• Consistent Weld Penetration: Weld power and line speed are logged per coil, and a flattening test is run every shift to confirm the seam does not open under load.
• Cut to Any Length: Standard 6 m mill length in stock, with 12 m, fixed cut lengths and 45 degree mitre ends available on request.

Light structural framing is the main use: greenhouse and polytunnel hoops, shelving uprights, display rack frames, machine guards, handrail infill and light trailer bodies. It is also a common choice for furniture frames and shop fittings where the tube is powder coated after fabrication, and for cable or wiring conduit in agricultural buildings where a closed section is preferred over channel. On the load side, a 20 x 20 x 1.5 mm Grade B section is normally used as a secondary member braced by the main frame rather than as a primary beam, and we will confirm the section properties for your span if you send the drawing.

Tubes are bundled hexagonally to a maximum of 2 tons per bundle, secured with three steel strips and one plastic band, wrapped in waterproof paper and covered with a PVC sleeve for sea freight. Every bundle carries two tags with heat number, size, wall and grade. Mill test reports to EN 10204 3.1 are issued with each shipment, and third party inspection by SGS or BV can be arranged before loading. We hold ISO 9001, CE and CNAS certification, and a pre shipment sample of 300 mm is available free of charge, with courier cost on the buyer side.

One practical note on this size: because the wall is thin, the cut end collapses easily if the tube is gripped in a vice without a soft jaw, and welders tend to burn through at 1.5 mm on the corner. We recommend a 2.0 mm wall for any application where the joint is welded rather than bolted, and we can supply both walls from the same coil in one container if the project needs a mix.