Description
Factory-direct pricing with no middlemen — every Q235B welded square and rectangular steel tube rolls off our own ERW lines, cutting procurement costs while maintaining full traceability from coil to finished section.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Welded Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (Hollow Section / RHS / SHS) |
| Steel Grade | Q195, Q215, Q235, Q345B, S235JR, S355JR, SS400 |
| Standard | ASTM A213, DIN EN 10217-1, ASTM, JIS, ISO 9001 |
| Section Shape | Square, Rectangular |
| Size Range | 300×300 mm |
| Wall Thickness | 1–3 mm |
| Length | 6 m / 6.4 m / 12 m / Custom |
| Technique | ERW (Cold Rolled / Hot Rolled) |
| Surface Treatment | Hot Rolled / Oiled / Non-oiled |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Construction Building Material, Steel Structures, Machinery, Furniture, Architectural Decoration |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Structural frames, load-bearing columns, scaffolding systems |
| Machinery Manufacturing | Equipment bases, conveyor frames, automation system supports |
| Architectural Decoration | Visible structural elements, furniture frames, interior support columns |
| Steel Structures | Portal frames, warehouse trusses, mezzanine floor supports |
How Negative Tolerance on Thin-Wall ERW Tubes Creates Structural Risk on Site
A 0.8 mm shortfall on a 3 mm nominal wall turns a compliant structural member into a liability.
When procurement teams order Q235B welded square and rectangular steel tube with 1–3 mm wall thickness, the ±1% tolerance window leaves almost no room for suppliers pushing negative tolerance to the edge. A 3 mm tube measured at 2.7 mm may still pass mill paperwork, but it reduces the section modulus and load-bearing capacity below what the structural engineer calculated. On a construction site, this means connection plates do not align, bolt holes drift, and the entire frame fails inspection — not because the steel grade was wrong, but because the wall was too thin to carry the designed load [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements].
Matching Thin-Wall ERW Hollow Sections to Structural and Architectural Applications
The 300×300 mm square profile with 1–3 mm wall thickness sits in a specific engineering zone: light to medium structural framing where self-weight matters more than ultimate load capacity. For machinery manufacturers building conveyor frames and automation system supports, the ERW cold-rolled surface finish eliminates the need for secondary grinding before powder coating. Construction teams using Q235B welded square and rectangular steel tube for scaffolding and mezzanine floors benefit from the ±1% dimensional consistency, which keeps modular connection systems aligned across hundreds of joints.
Engineering Compliance and Certification Requirements Across Markets
Structural hollow sections destined for EU projects must conform to EN 10219 for cold-formed welded structural tubes, while North American buyers reference ASTM A500 or ASTM A213 depending on the application. The Q235B grade maps broadly to S235JR under EN standards and SS400 under JIS, but equivalence is not automatic — chemical composition limits and testing protocols differ, and customs authorities in the EU increasingly require CE marking under EN 10210 or EN 10219 before releasing structural steel at the port [NEED_CITE: steel grade equivalence mapping between GB Q-series and EN S-series]. For projects in Southeast Asia and the Middle East, SGS or BV third-party inspection reports often serve as the de facto quality gate, since local standards may reference ASTM or EN without providing independent verification infrastructure.
Understanding Q235B, ERW Welding, and Surface Treatment Choices
Q235B belongs to the Chinese GB/T 700 carbon structural steel family, with a minimum yield point that positions it between Q195 (light-duty, non-structural) and Q345B (higher-strength structural). When the same product line also offers S235JR and S355JR, buyers are accessing the European EN 10025 grade system, where the number after “S” indicates minimum yield strength in MPa. The ERW welding process used for these tubes creates a longitudinal weld seam by pressing heated steel strip edges together under pressure — it produces a smooth, consistent surface ideal for architectural applications where appearance matters, at a lower cost than seamless alternatives. Surface treatment options range from hot-rolled (mill scale present, suitable for hidden structural work) to oiled (short-term corrosion protection during transit and storage) to non-oiled (for immediate painting or galvanizing by the buyer). The 1–3 mm wall thickness range means these tubes are classified as thin-walled hollow sections, where tolerance control becomes critical because even small deviations represent a large percentage of the total wall.
Hidden Costs When Wall Thickness and Grade Documentation Fall Short
Ordering Q235B welded square and rectangular steel tube without verifying actual wall thickness against the mill test certificate creates a cascade of downstream costs. If the delivered tubes measure below the specified tolerance, the structural engineer must either reject the shipment or recalculate the entire frame — both options delay the project and add cost. Missing or incomplete CE documentation for EU-bound shipments results in customs holds that can stretch for weeks, during which storage fees accumulate and the construction schedule stalls. Material traceability gaps — no heat number, no mill test certificate, no third-party inspection record — mean the buyer absorbs full liability if a structural failure occurs later, regardless of whether the steel itself was adequate [NEED_CITE: structural steel procurement compliance requirements under EN 10219 and ASTM A500].
Why Procurement Teams Choose Our ERW Hollow Section Production
Every Q235B welded square and rectangular steel tube we produce passes through our in-house physical and chemical laboratory at three stages: incoming coil inspection, in-process weld seam verification, and final dimensional measurement before bundling. We hold CE certification under EN 10210 and EN 10219, ISO 9001:2015 registration, and accept SGS or BV third-party inspection on any order — documentation that clears EU and Middle Eastern customs without delay. Our production lines cover over 2,800 specifications across square, rectangular, and round profiles, meaning a buyer sourcing 300×300 hollow sections can also order matching H-beams, channel steel, and custom-cut plates from a single purchase order, eliminating the coordination overhead of managing multiple suppliers. We participated in drafting China’s cold-formed steel industry standards in 2018, and our 41 invention patents include proprietary sharp-corner rectangular tube technology that delivers tighter corner radii than standard ERW dies allow. Every shipment includes professional container loading plans optimized for the 6 m, 6.4 m, or 12 m lengths ordered, reducing freight cost per ton.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition (C, Mn, Si, S, P limits) and mechanical properties per GB/T 700, with heat number traceability to the original coil
- CE certificate confirming compliance with EN 10219 for cold-formed welded structural hollow sections, required for EU customs clearance
- ISO 9001:2015 quality management system certificate covering the full production process from coil slitting to final bundling
- SGS or BV third-party inspection report available upon request, covering dimensional verification, weld seam quality, and surface condition
- Material traceability sheet linking each bundle’s heat number to the mill test certificate and production batch record
- Customs documentation package including packing list, bill of lading, and certificate of origin formatted for the destination country’s import requirements
Packaging, Loading & Delivery
- Q235B welded square and rectangular steel tubes bundled with steel strip bands and edge protectors to prevent surface damage to the hot-rolled or oiled finish during ocean transit
- Plain-end tubes stacked in nested configurations within 20ft or 40ft containers, maximizing payload for 6 m and 12 m lengths while staying within road weight limits at destination
- Oiled surface treatment applied before bundling to provide short-term corrosion protection during transit and open-yard storage at the construction site
- Custom cut-to-length service available for 6.4 m or non-standard lengths, with each piece marked with heat number, steel grade Q235B, and wall thickness for on-site identification
- FOB, CIF, and DDP shipping terms available, with professional loading plans that account for the 300×300 mm profile dimensions and 1–3 mm wall thickness to optimize container utilization
- Door-to-door logistics coordination for projects in Southeast Asia, the Middle East, and Africa, with real-time shipment tracking from our Shandong facility to the destination port
Starting Your Q235B Hollow Section Procurement
Send your specification sheet — section dimensions, wall thickness, steel grade, total tonnage, and destination port — and receive a detailed quotation within 12 hours, including unit price, applicable certifications, and estimated production timeline. For non-standard sizes or custom lengths outside the 6 m / 6.4 m / 12 m range, our technical team will confirm feasibility and provide a separate lead time.
Request Your Quotation and Mill Test Certificate
Submit your Q235B welded square and rectangular steel tube requirements via email or WhatsApp to receive pricing, certification documentation, and container loading plans.
Email: admin@sdxjysteel.com
Mobile / WhatsApp / WeChat: +86 188 5315 7756
Tel: +86 531 8573 6315
Frequently Asked Questions
Q: What is the difference between Q235B, S235JR, and SS400 for this welded square and rectangular steel tube?
A: These three grades belong to different national standards — Q235B to Chinese GB/T 700, S235JR to European EN 10025, and SS400 to Japanese JIS G3101. They share similar carbon content ranges and are often used interchangeably for light structural applications, but chemical composition limits and testing protocols differ. We produce all three grades on the same ERW lines and provide the corresponding mill test certificate for each.
Q: Can you provide a third-party inspection report for Q235B welded square and rectangular steel tube before shipment?
A: Yes. We accept SGS or BV third-party inspection on any order. The inspector verifies wall thickness against the ±1% tolerance, checks weld seam quality, confirms surface treatment condition, and reviews the mill test certificate. The inspection report is issued before the container is sealed and travels with the shipment documentation.
Q: What is the minimum order quantity for custom-length Q235B welded square and rectangular steel tube?
A: The standard MOQ is 5 tons. For custom lengths outside 6 m, 6.4 m, or 12 m, or for non-standard section dimensions, we evaluate feasibility based on our current production schedule and confirm whether the 5-ton minimum applies or if a higher quantity is needed to justify a dedicated die setup.
Q: How do you handle surface treatment for oiled versus non-oiled Q235B welded square and rectangular steel tube?
A: Oiled tubes receive a light anti-rust oil coating after the final ERW pass, which protects the hot-rolled surface during ocean transit and short-term open-yard storage. Non-oiled tubes are delivered with bare mill finish, suitable for buyers who plan to galvanize or paint immediately upon arrival. The surface treatment choice is confirmed at the quotation stage and noted on the mill test certificate.
Q: Do you provide CE certification for Q235B welded square and rectangular steel tube shipped to the EU?
A: Yes. Our CE certificate covers EN 10219 cold-formed welded structural hollow sections, and we also hold EN 10210 certification for hot-finished structural hollow sections. The CE declaration of performance, along with the mill test certificate and factory production control documentation, is included in the shipment package for EU customs clearance.
Get Your Q235B Hollow Section Quote Today
Send your section dimensions, wall thickness, steel grade, and destination port to receive a detailed quotation with mill test certificate samples and container loading plans within 12 hours.
Email: admin@sdxjysteel.com
Mobile / WhatsApp / WeChat: +86 188 5315 7756
