The production of cold-formed square and rectangular tubes begins with a coil of steel strip. After uncoiling, the strip is slit longitudinally to the required developed width and fed into a series of driven forming rolls, which gradually bend the material until the profile closes. The two edges meet at the top and are fused together by a high-frequency induction welder; the external weld bead is immediately scarfed off to ensure a smooth surface. The tubes then pass through sizing rolls, a straightener, and a flying saw. Galvanizing, if required, is performed either at the end of the production line or as a post-processing step.
Our sizing roll settings ensure that the wall thickness of standard-grade cold-formed square and rectangular tubes remains within a ±10% range, with the capability to achieve a tighter ±7.5% tolerance for specific project requirements. Precise wall thickness control means your welding parameters remain consistent from one bundle to the next.
The standard forming process yields an external corner radius of approximately 2t. Designers can base bracket and end-plate designs directly on this figure, eliminating the need for on-site grinding—often the deciding factor in whether a framework takes one day or three days to assemble.
Cold forming induces strain hardening in the corner areas—precisely where bending loads are concentrated. Consequently, for the same weight, cold-formed profiles support greater loads than hot-rolled flat-sided profiles, making them our recommended choice for trusses and long-span frameworks.
We offer pre-galvanized strip (Z120 to Z275 g/m²) for tubes suitable for on-site cutting and drilling, as well as hot-dip galvanized tubes with coating thicknesses of 60 to 80 microns. Hot-dip galvanizing is recommended for applications involving underground installation, prolonged exposure to moisture, or contact with fertilizer runoff.
With straightness controlled to within 2 mm per meter and 0.15% of the total length, our 6-meter cold-formed square and rectangular tubes can be placed directly into assembly jigs without the need for shims.
Cold-formed square and rectangular tubes are commonly used for frameworks requiring load-bearing capacity, straightness, and rapid on-site assembly. Below are the categories we quote most frequently; if your project falls between these categories, simply send us the span and load requirements, and we will recommend the closest standard specification.
Galvanized tubes ranging from 40×40 mm to 60×80 mm are used for arches, purlins, and end walls in film and polycarbonate (PC) greenhouses. In this context, the coating is more critical than the cross-section; since the steel is constantly exposed to condensation within the greenhouse, we supply pre-galvanized Z275 steel rather than black steel.
Cold-formed tubes are widely used for ground-mounted PV arrays and "fishery-solar hybrid" projects because they allow for on-site drilling and bolting without compromising the galvanized coating. We supply cut-to-length tubes tailored to rail and purlin positions—usually pre-galvanized—requiring only localized zinc touch-ups at the cut ends.
Square tubes serve as exposed structural elements for columns, roof trusses, mezzanine floors, and temporary works; in these applications, clean corner radii and robust strength are equally important.
Guardrails, Fencing, and Site Safety Barriers: Powder-coated or hot-dip galvanized tubes are typically used for excavation edge protection, zinc-steel fencing, and workshop partitions. We have found that the corner radius is the key factor determining the visual appeal of the finished fence.
Columns and beams typically range from 30×30 mm to 80×80 mm with wall thicknesses of 1.5 mm to 2.5 mm, resulting in shelving units light enough to be moved using a pallet jack.
Machine guards, trailer frames, fitness equipment, and conveyor supports utilize this same family of profiles; Q355B steel is typically selected when the framework requires vibration resistance.
We verify that the heat number, steel grade, and mechanical properties match the quality certificate and measure the thickness at both ends of the strip. Any strip steel that does not comply with the quality certificate is rejected from the production line.
Steel strip is slit to the width calculated based on the finished cross-section, ensuring the profile dimensions are achieved precisely in a single pass and avoiding over-forming.
High-frequency induction welding is used; welding power and line speed are recorded per shift. At the start of each coil run, a section is flattened and subjected to a bend test; the production line is stopped immediately if the weld seam cracks during this test.
Sizing rolls determine external dimensions, a straightener eliminates bending and twisting, and a flying saw cuts the material to the required length.
Either pre-galvanized strip is used from the start, or the finished pipe undergoes a hot-dip galvanizing process; coating thickness is spot-checked by batch.
Before packaging, we spot-check the cold-formed square and rectangular tubes for external dimensions, wall thickness, squareness, coating weight, and surface condition. Inspection records are retained by heat number, so if your engineers ask which heat number was used for a specific project, we can provide the answer.
We are located within a major steel distribution hub, rather than operating through intermediaries or distant traders. For your project, this means two things: specification changes can be implemented in days rather than weeks, and any quality claims can be resolved directly with the mill that rolled the pipes. With extensive export experience serving Southeast Asia and the Middle East, we are well-versed in ocean shipping, packaging for hot and humid maritime routes, and English documentation.
A: Full payment is required before shipment. The factory's Spring Festival holiday runs from the 26th day of the 12th lunar month to the 8th day of the 1st lunar month; therefore, orders requiring delivery before the Spring Festival should ideally be confirmed one month in advance.
A: Drilling and punching services are available upon request. If the holes are for bolted connections, please provide the connection drawing rather than just a list of hole locations; we will verify the hole layout and corner radii before cutting the material.
A: There is no minimum order quantity; mixed specifications can be combined to fill a single container. Samples are free (freight collect); you can bend, weld, and plate a section first to decide whether to place a mass production order.
A: Yes. Each shipment includes a quality certificate listing the heat number, chemical composition, and mechanical properties, along with our own dimensional and coating inspection records. If the project requires third-party inspection, we can arrange it using the same sampling plan—simply inform us of the standards and the inspection agency when confirming the order.
A: Deliveries begin approximately 5 days after order confirmation, followed by successive batch deliveries. Finished products are bundled in a hexagonal shape, strapped with steel bands, and wrapped in waterproof film; wooden pallets are added for sea and rail transport. We can also package the goods according to your specific requirements.
A: We cut according to your cutting list, with a tolerance of approximately ±1.5 mm.
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S213 Jinghai District, Tianjin City, China
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