Description
Factory-direct Q235B tubes — Mill-produced square and rectangular hollow sections shipped under EN10219 and ASTM A500 compliance with full dimensional and chemical traceability per heat number.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Square Rectangular Steel Tube |
| Product Type | Square and Rectangular Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q235B, Q345, #20, #45 |
| Standard | EN10219, EN10210, GB/T 6728, JIS G3466, ASTM A500, ASTM A36, ASTM A53 |
| Section Shape | Square / Rectangular |
| Size Range | Square 20×20mm–500×500mm; Rectangular 20×40mm–300×500mm |
| Wall Thickness | 1.2mm–20mm |
| Length | 3m–12m (random or cut-to-length) |
| Technique | Hot Rolled / Welded |
| Surface Treatment | Pre-galvanized (40–80g/m²), Hot-dip galvanized (200–600g/m²), Black / Oiled |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Construction, Steel Structures, Solar Structures, Fencing, Greenhouse Frames, Machinery, Glass Curtain Walls |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & EPC | Building frames, column supports, beam-to-column connections, roof trusses |
| Solar & Renewable Energy | Solar panel mounting structures, ground screw bases, tracker frames |
| Agricultural Infrastructure | Greenhouse skeleton frames, irrigation pipe supports, livestock fencing posts |
| Machinery & Equipment | Conveyor frame structures, machine base platforms, equipment guardrails |
| Architectural Facades | Glass curtain wall mullions, decorative facade framing, canopy supports |
Where Dimensional Tolerance Decides Structural Alignment on Site
A ±1% tolerance on a 500×500mm Q235B square tube means the difference between a beam that slides into place and one that requires on-site rework.
When procurement teams order Q235B square and rectangular steel tube for structural frames, the first failure point is rarely the steel grade — it is the dimensional inconsistency between pieces. Tubes that arrive with uneven side lengths or wall thickness variation force fabricators to re-cut, re-weld, and re-align, adding days to project timelines. On EPC sites across West Africa and Southeast Asia, I have seen entire container loads of rectangular tubes rejected because the wall thickness drifted beyond acceptable range, making connection plates impossible to bolt flush. [NEED_CITE: EN 10219 cold-formed structural hollow section dimensional tolerance requirements]
How Q235B Tubes Match Structural Frame Load Paths
Q235B square and rectangular steel tube in the 100×100mm to 300×300mm range with wall thickness above 5mm serves as primary load-bearing members in low-to-mid-rise steel structures. The closed cross-section provides torsional rigidity that open profiles cannot match, making it suitable for column-to-beam moment connections. For solar mounting structures in coastal environments, hot-dip galvanized Q235B tubes at 200–600g/m² zinc coating resist salt spray corrosion without additional painting, reducing lifecycle maintenance costs.
Engineering Compliance and Certification Requirements
Structural hollow sections used in load-bearing applications must comply with dimensional and mechanical requirements defined by EN 10219 for cold-formed welded tubes or EN 10210 for hot-finished profiles. When shipping Q235B square and rectangular steel tube to EU markets, CE certification under EN 10210/EN 10219 is mandatory for customs clearance — missing Declaration of Performance documents will hold the entire shipment at port. For North American projects, ASTM A500 Grade B or C compliance must be documented on the mill test certificate, with chemical composition and tensile test results traceable to each heat number. [NEED_CITE: CE marking requirements for structural steel hollow sections under EN 10210]
Steel Grade Selection and Manufacturing Process
Q235B sits in the mild carbon steel range with balanced weldability and formability, making it the default choice for general structural applications where extreme strength is not required. The Q-series (Q195–Q345) follows Chinese GB standards, while equivalent grades in international systems include S235JR under EN standards and ASTM A36/A500 Grade B under American specifications. Welded Q235B tubes produced through ERW or submerged arc welding offer cost advantages for non-pressure applications, while hot-rolled seamless variants serve higher-load scenarios. Surface treatment selection depends on the service environment: pre-galvanized at 40–80g/m² suits indoor or temporary structures, hot-dip galvanized at 200–600g/m² handles outdoor exposure, and black/oiled finish works for painted or concealed applications. Wall thickness tolerance directly affects theoretical weight calculation — a 5mm wall tube at negative tolerance delivers less steel per meter than nominal, impacting both structural capacity and project cost.
Hidden Costs of Incorrect Grade Specification and Missing Documentation
Ordering Q235B square and rectangular steel tube without verifying mill test certificate authenticity creates downstream risk: material that fails to meet declared chemical composition will not pass third-party inspection, triggering shipment rejection or costly re-melting. Tubes supplied without proper CE documentation face customs detention in EU ports, with demurrage charges accumulating daily. Negative tolerance abuse — where actual wall thickness falls below declared specification — compromises structural integrity and voids engineering liability coverage. [NEED_CITE: steel grade equivalence mapping between GB Q-series and EN S-series standards]
Procurement Advantages Directly from the Mill
As the original inventor of sharp-corner rectangular steel tubes in China with 41 invention patents, we produce Q235B square and rectangular steel tube across 2,800+ specifications covering wall thicknesses up to 40mm — eliminating the specification gaps that force buyers to source from multiple suppliers. Our in-house physical and chemical laboratories generate mill test certificates per EN 10204 3.1 for every heat number, with third-party inspection by SGS or BV available before container sealing. Full CE certification under EN 10210/EN 10219 and Singapore FPC approval ensure smooth customs clearance across 50+ export markets. Custom non-standard sizes, cut-to-length service, and professional container loading with anti-damage reinforcement prevent the bending and surface damage that plague improperly packed tube shipments.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition (C, Mn, Si, P, S content) and mechanical properties per GB/T 6728 or EN10219
- CE certificate of conformity under EN10210/EN10219 for structural hollow sections entering EU markets
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report verifying dimensional accuracy, surface quality, and coating thickness
- Material traceability sheet linking each bundle to heat number, production date, and test results
- Export documentation including packing list, bill of lading, and certificate of origin for customs clearance
Packaging, Loading & Delivery
- Q235B square and rectangular steel tube bundled with steel strips and edge protectors to prevent corner deformation during ocean transit
- Hot-dip galvanized tubes wrapped with waterproof paper and plastic film to preserve zinc coating integrity in humid container environments
- Container loading optimized for 6m and 12m lengths with wooden dunnage and steel wire lashing to eliminate in-transit shifting and bending
- Cut-to-length service available for 3m–12m random or fixed lengths, with bundle weight controlled to match crane capacity at destination site
- Each bundle marked with heat number, steel grade Q235B, dimensional specification, and manufacturer identification for site traceability
- Shipping terms available as FOB, CIF, or DDP with professional tube loading plans submitted for buyer approval before container sealing
Requesting Quotation and Technical Documentation
Submit your Q235B square and rectangular steel tube requirements including section dimensions, wall thickness, length, surface treatment preference, and total tonnage to receive a detailed quotation with unit pricing, production lead time, and shipping terms within 12 hours. Mill test certificates, CE documentation, and third-party inspection arrangements are confirmed at contract stage. Custom non-standard sizes and cut-to-length specifications are reviewed by our technical team for feasibility and pricing.
Frequently Asked Questions
Q: What is the difference between Q235B and S235JR for structural applications?
A: Q235B and S235JR are equivalent grades with similar yield strength levels, but they follow different standards — Q235B under Chinese GB/T 700 and S235JR under European EN 10025. Both are suitable for general structural applications, but certification requirements differ: EU projects require S235JR with CE marking under EN 10219/10210, while domestic or Belt & Road projects often specify Q235B.
Q: Can you provide hot-dip galvanized Q235B tubes with coating thickness above 400g/m²?
A: Yes, hot-dip galvanizing for Q235B square and rectangular steel tube is available at 200–600g/m² zinc coating thickness. For aggressive environments such as coastal or industrial areas, we recommend 400–600g/m² to ensure long-term corrosion resistance without additional painting.
Q: What is the minimum order quantity for custom non-standard sizes?
A: The MOQ for Q235B square and rectangular steel tube is 1 ton. Custom non-standard sizes outside our 2,800+ specification range are accepted subject to production feasibility review, with typical minimum quantities depending on section complexity and total weight.
Q: Do you arrange third-party inspection before shipment?
A: Yes, SGS and BV third-party inspection services are available upon request. Inspection covers dimensional verification, surface quality check, coating thickness measurement for galvanized tubes, and witness of mechanical testing. Inspection reports are issued before container sealing.
Q: How do you ensure tubes arrive without bending or surface damage?
A: Professional container loading plans include wooden dunnage placement, steel wire lashing, and edge protectors for bundled tubes. Hot-dip galvanized tubes receive additional waterproof wrapping. Loading photos and videos are shared with buyers before container sealing for verification.
Get Your Q235B Tube Quotation with Full Certification
Send your specification sheet including dimensions, wall thickness, steel grade, surface treatment, quantity, and destination port to receive pricing and mill test certificate samples within 12 hours.
Company: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxjypipe.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjypipe.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
