Description
Factory-direct ERW hollow sections — 2,800+ specifications in ready stock with original mill test certificates for every Q235 batch shipped.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 Carbon Steel Square & Rectangular Tube |
| Product Type | Square / Rectangular Steel Tube (SHS / RHS) |
| Steel Grade | Q195, Q215, Q235, Q345, 10#, 20# |
| Standard | EN10219, EN10210, ASTM A500, ASTM A53, ASTM A106, GB/T 6728, JIS G3466 |
| Section Shape | Square / Rectangular |
| Size Range | 10×10 – 500×500 mm |
| Wall Thickness | 0.9 – 25 mm |
| Length | 6 m / 9 m / 12 m (customized available) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Cold Rolled (Galvanized, Painted, Oiled available) |
| Tolerance | ±1% |
| Ends | Plain / Cut / Welding / Bending / Punching |
| Application | Steel structures, Construction frames, Transmission towers, Piling, Pipeline engineering, Mechanical industry, Municipal projects |
| MOQ | 500 KG |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, scaffolding structures, piling supports, municipal road barriers |
| Industrial & Mechanical | Machinery frames, conveyor structures, equipment bases, warehouse racking |
| Energy & Utilities | Power transmission tower members, oil and gas pipeline supports, solar mounting structures |
| Steel Fabrication | Welded assemblies, cut-to-length components, punched connection plates |
Where Dimensional Tolerance Decides Structural Fit-Up on Site
A ±1% tolerance on a 500×500 SHS means the difference between bolt holes aligning and cutting beams open.
When procurement teams source Q235 Carbon Steel Square Rectangular Tube from fragmented suppliers, wall thickness variations compound across container loads. A 2 mm deviation on a 10 mm wall changes the theoretical weight by nearly a fifth — and on a transmission tower with hundreds of connection nodes, that deviation means field rework, delayed erection, and structural engineer sign-off delays. We have seen containers arrive with tubes that look right from outside but fail fit-up because the internal corner radius was never controlled to EN 10219 cold-formed hollow section requirements [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance].
Matching Q235 ERW Hollow Sections to Structural Load Paths
Q235 Carbon Steel Square Rectangular Tube in the 100×100 to 300×300 mm range with wall thickness between 4 mm and 10 mm serves as primary compression members in portal frames and secondary bracing in industrial buildings. The ERW weld seam runs along the flat face rather than the corner, which matters when these tubes are welded to gusset plates — the full-width bearing surface distributes load without the stress concentration that round tubes create at tangent points. For transmission tower applications, the flat faces allow direct bolted connections without custom saddle plates, cutting fabrication time on each node.
Engineering Compliance and Certification Requirements
Structural frames destined for European markets must conform to EN 10219 for cold-formed welded structural hollow sections, while North American projects typically specify ASTM A500 Grade B or C. The Q235 grade maps closely to S235JR under EN standards, though project engineers should verify chemical composition requirements for welding compatibility — specifically carbon equivalent values for thicker walls above 12 mm [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500]. CE certification under EN 10210/EN 10219 with FPC (Factory Production Control) documentation is mandatory for customs clearance into EU member states, and missing this paperwork typically holds containers at port for weeks.
Understanding Q235 Grade and ERW Process Characteristics
The Q-series carbon steel grades (Q195 through Q345) follow the Chinese GB/T 700 standard, where the number indicates minimum yield strength in MPa. Q235 sits in the middle of this range, offering adequate strength for general structural work while maintaining excellent weldability and formability — properties that make it the default choice for construction frames and mechanical structures across Asia, Africa, and South America. The ERW (Electric Resistance Welded) process forms the tube by rolling flat strip into a closed section and fusing the seam through electrical resistance heating without filler metal. This produces a consistent weld zone with minimal heat-affected area, keeping the mechanical properties uniform around the entire cross-section. For wall thickness above 6 mm, the ERW seam undergoes ultrasonic testing to ensure full penetration, while thinner walls rely on the inherent consistency of the high-frequency welding current.
Hidden Costs of Unverified Material and Missing Documentation
Purchasing Q235 Carbon Steel Square Rectangular Tube without original mill test certificates creates downstream liability that far exceeds any initial price saving. When material cannot be traced back to heat numbers, project inspectors reject entire batches — and replacing 20 tons of tube after customs clearance costs multiples of the original material value in demurrage, re-shipping, and schedule penalties. Negative tolerance abuse (where actual wall thickness falls below the ordered specification) reduces load-bearing capacity and violates EN 10219 requirements, exposing the structure to failure under design loads [NEED_CITE: consequences of negative tolerance abuse in structural hollow sections].
Procurement Confidence Through Direct Factory Control
Every Q235 Carbon Steel Square Rectangular Tube we supply comes from our own three production lines running simultaneously, meaning you deal with the manufacturer rather than a trading intermediary adding margin and obscuring accountability. Our in-house laboratory issues original mill test certificates documenting chemical composition and mechanical properties for each heat number, and we welcome SGS or BV third-party inspection before shipment — a practice that has built repeat orders across 50+ countries. With over 2,800 specifications maintained in ready stock, we can consolidate square tubes, rectangular tubes, plates, and sections into single container loads, eliminating the coordination overhead of managing multiple suppliers. Custom lengths, punched holes, and bent configurations are processed in-house, so your fabrication drawings go directly to our production floor without intermediate handling.
Documentation & Compliance
- Mill test certificate documenting Q235 chemical composition (C, Mn, Si, S, P) and yield strength per GB/T 6728 and EN 10219
- CE certificate covering EN 10210 and EN 10219 compliance with FPC factory production control records
- ISO 9001:2015 quality management certificate covering the full production and inspection process
- SGS or BV third-party inspection report available upon request, verifying dimensional tolerance and surface quality
- Full material traceability by heat number from steel coil to finished tube, recorded in mill test documentation
- Export customs documents including packing list, bill of lading, and certificate of origin for destination clearance
Packaging, Loading & Delivery
- Cold rolled Q235 tubes bundled with steel strips and edge protectors to prevent surface scratching during ocean transit
- Container loading plans optimized for 6 m and 12 m lengths, nesting smaller rectangular sections inside larger square tubes to maximize payload per 40ft container
- Surface protection with anti-rust oil applied before bundling for tubes destined for humid climates or extended storage
- Heat number and steel grade stenciled on each bundle tag, matching the mill test certificate for site verification
- FOB, CIF, and DDP shipping terms available with professional documentation handling for customs clearance at destination port
- Cut-to-length and end-processing (punched, beveled, or bent) completed before packaging to reduce on-site fabrication
Requesting a Quotation with Full Material Verification
Submit your specification sheet including section dimensions, wall thickness, total tonnage, steel grade preference, and destination port — we return a detailed quotation with volume-based pricing, production lead time, and sample mill test certificate within 12 hours. For non-standard sizes or custom processing requirements, our engineering team reviews your drawings and confirms feasibility with dimensional sketches before contract signing.
Get Your Q235 Hollow Section Quote with Mill Test Certificate
Send your specifications via email or WhatsApp to receive factory-direct pricing and original mill test documentation for your next project.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxinjiyuan.com
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
