Description
Factory-direct ERW square tubes — 2,800+ specifications in stock with mill test certificates for every heat.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345 ERW Square Steel Pipe |
| Product Type | Square Steel Pipe (ERW) |
| Steel Grade | Q195, Q215, Q235, Q345, S235JR, GR.B-D, STK500 |
| Standard | GB/T3091-2001, EN10219, ASTM A53, JIS G3444:2004, BS EN10255-2004 |
| Section Shape | Square |
| Size Range | 10mm×10mm – 500mm×500mm |
| Wall Thickness | 0.6mm – 20mm |
| Length | 1m / 4m / 6m / 8m / 12m (customizable) |
| Technique | Hot Rolled / Cold Rolled ERW |
| Surface Treatment | Bare / Oiled / 3PE Coating / Printed / Customized |
| Ends | Plain / Beveled / Threaded with Couplings or Sockets |
| Tolerance | ±1% / ±5% / ±10% |
| Application | Structure Pipe / Steel Structures / Construction Frames / Machinery |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, bridge support columns, scaffolding uprights |
| Facade & Curtain Wall | Architectural steel framing, right-angle exposed structures |
| Machinery Manufacturing | Conveyor structures, equipment bases, hydraulic support frames |
| Steel Structure Fabrication | Portal frames, truss members, purlin systems |
Where Wall-Thickness Tolerance Decides Acceptance on Site
A single heat failing dimensional tolerance can reject an entire container at third-party inspection.
I once saw a batch of thick-wall tubes get rejected because the wall deviation exceeded the allowable negative tolerance — the client’s SGS inspector flagged every piece, and the whole shipment had to be re-rolled. For Q235 Q345 ERW Square Steel Pipe orders, buyers in the EU and Middle East increasingly demand EN 10219 compliance with verifiable MTCs per heat number [NEED_CITE: EN 10219 cold-formed structural hollow section dimensional tolerances]. When tolerance documentation is vague or missing, customs brokers in regulated markets hold the cargo, and project timelines slip. The cost is never just the steel — it is the crane idle time and the re-fabrication that follows.
Matching Structural Frames and Facade Requirements
Q235 Q345 ERW Square Steel Pipe in side lengths from 10×10mm to 500×500mm covers everything from light machinery bases to heavy structural columns. For facade contractors, the availability of sharp-corner profiles means exposed steel frames achieve clean right-angle lines without additional grinding or filling. Wall thickness options from 0.6mm to 20mm let engineers specify precisely for load-bearing versus non-load-bearing zones, reducing material waste on large-scale projects.
Engineering Compliance and Surface Protection
Structural frames designed to EN 1993 or AISC standards require verified steel grades with traceable chemistry [NEED_CITE: steel grade equivalence between GB Q-series and EN S-series standards]. Q235 maps to S235JR for general construction, while Q345 serves higher-load applications. For outdoor or corrosive environments, 3PE coating or oiled surface treatment extends service life without hot-dip galvanizing costs. Custom cut-to-length service eliminates on-site welding for standard connections, and beveled or threaded ends support direct mechanical joining.
Steel Grade Selection and ERW Process Characteristics
The Q-series (Q195–Q345) follows Chinese GB standards, with yield strength increasing from Q195 to Q345 — this directly affects load-bearing capacity for columns and beams. S235JR and STK500 provide EN and JIS equivalents for international projects, avoiding grade-substitution errors during procurement. ERW welding produces a longitudinal seam suitable for structural applications up to moderate wall thickness, offering cost advantages over seamless for non-pressure uses. Hot-rolled surfaces accept coatings directly, while cold-rolled finishes provide tighter dimensional control for precision machinery components [NEED_CITE: ERW versus seamless steel tube application guidelines].
Hidden Costs of Incorrect Grade or Missing Certification
Specifying Q235 when the structural engineer called for Q345 means lower yield strength and potential deflection under design loads — discovered only after fabrication, when replacement means dismantling welded assemblies. Missing CE marks or incomplete EN 10219 references block EU customs clearance regardless of physical quality. Negative tolerance abuse — where actual wall thickness falls below the stated minimum — reduces load capacity and fails third-party inspection, triggering full-container rejection and re-rolling costs borne by the buyer who trusted an unverified mill certificate [NEED_CITE: structural hollow section inspection requirements for import compliance].
Procurement Confidence from Mill to Site
Every Q235 Q345 ERW Square Steel Pipe order ships with in-house laboratory test reports covering chemical composition and mechanical properties per heat number. Our 41 invention patents include China’s original sharp-corner rectangular tube technology, now applied across 2,800+ specifications with wall thickness up to 40mm for heavy structural work. Full CE certification under EN 10210/10219 and ISO 9001:2015 ensure smooth customs clearance in EU and regulated markets. Third-party inspection through SGS or BV is arranged on request before container sealing. Professional loading with anti-damage measures prevents bending and surface scratches during ocean transit, while custom non-standard sizes accept orders from 1 Ton MOQ.
Documentation & Compliance
- Mill Test Certificate documenting Q235 or Q345 chemical composition and yield strength per GB/T3091 or EN10219
- CE certificate confirming EN 10210/EN 10219 compliance for structural hollow sections entering EU markets
- ISO 9001:2015 quality management certificate covering production and inspection processes
- SGS or BV third-party inspection report verifying dimensional tolerance and surface quality before shipment
- Material traceability by heat number linking each bundle to its production batch and test results
- Export customs documents including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- ERW square tubes bundled with steel strips and edge protectors to maintain 10-500mm side dimensions during handling
- Oiled or 3PE-coated surfaces wrapped with moisture barriers to prevent corrosion during ocean transit
- Container loading optimized for 6m and 12m lengths to maximize payload while preventing inner-tube deformation
- Custom cut-to-length service available for 1m to 12m requirements, reducing on-site cutting waste
- Heat number and steel grade stenciled on each bundle for site identification and inspection traceability
- FOB, CIF, and DDP shipping terms with professional container loading and door-to-door tracking
Start Your Procurement with Verified Specifications
Submit your Q235 Q345 ERW Square Steel Pipe requirements — including side length, wall thickness, steel grade, surface treatment, quantity, and destination port — to receive a detailed quotation with unit pricing, production lead time, and mill test certificate samples. Non-standard sizes and custom lengths are confirmed within 12 hours, with third-party inspection options available before shipment.
Request Quotation and Mill Test Certificate
Send your specifications to admin@sdxjypipe.com or contact via WhatsApp at +86 188 5315 7756 for pricing, certification confirmation, and delivery scheduling.
Frequently Asked Questions
Q: How do Q235 and S235JR steel grades compare for structural applications?
A: Q235 and S235JR share similar yield strength levels and chemical composition ranges, making them functionally equivalent for general construction frames and machinery structures. Q235 follows Chinese GB standards while S235JR meets EN 10219 requirements for EU market imports.
Q: What is the minimum order quantity for custom non-standard square tube sizes?
A: The MOQ is 1 Ton for both standard and custom specifications. Non-standard side lengths or wall thicknesses outside the 10×10mm to 500×500mm range enter production with typical lead times of 15–25 days after deposit confirmation.
Q: Which surface treatment is best for outdoor structural applications?
A: For outdoor exposure, 3PE coating provides the strongest corrosion protection for buried or submerged structures, while oiled surfaces suit temporary protection during transit. Hot-dip galvanizing is available for long-term atmospheric corrosion resistance in coastal or industrial environments.
Q: Do your square tubes carry CE certification for EU customs clearance?
A: Yes, all structural hollow sections carry CE certification under EN 10210 and EN 10219 standards, with mill test certificates documenting compliance. Third-party inspection reports from SGS or BV are available upon request for additional verification.
Q: How do you prevent damage during container loading for long-length tubes?
A: We use professional loading techniques with wooden separators, steel banding, and edge protectors to prevent bending and surface scratches. 12m lengths are loaded with inner supports to maintain straightness, and each container is photographed before sealing for shipment documentation.
