Description
Factory-Direct ERW Square Tubes — S355JR and Q235B grades produced on-site with full mill test traceability and CE EN 10219 compliance for European project buyers.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S355JR / Q235B / SS400 ERW Square Steel Tube |
| Product Type | Welded Square Steel Tube (ERW) |
| Steel Grade | S235JR, S355JR, Q235B, SS400, A36 |
| Standard | ASTM A500, EN 10219, EN 10210, JIS G3466, GB/T 6728 |
| Section Shape | Square |
| Outer Diameter or Side Length | Customized |
| Wall Thickness | Customized |
| Length | 6m / 8m / 12m (Customized) |
| Technique | ERW (Electric Resistance Welded), Cold Rolled |
| Surface Treatment | Cold Rolled, Galvanized (optional) |
| Tolerance | ±1% |
| Ends | Plain / Customized |
| Surface Structure | Normal spangle (NS), Minimized spangle (MS), Spangle-free (FS) |
| Application | Building structures, machinery manufacturing, infrastructure, vehicle manufacturing |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Structural trusses, beam-to-column connections, greenhouse frames, bridge support members |
| Machinery Manufacturing | Machine tool frames, conveyor support structures, automation equipment frameworks |
| Vehicle & Transport | Trailer chassis, RV frames, auxiliary structural members |
| Commercial Building | Handrails, storage racks, interior decorative frameworks |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
±1% tolerance on cold rolled ERW square tubes determines whether your frame passes dimensional inspection or triggers on-site rework.
When structural engineers specify S355JR square tubes per EN 10219, they calculate load capacity based on nominal wall thickness. A supplier shipping material at the lower edge of acceptable tolerance — or worse, outside it — creates a cascade of problems: connection plates don’t align, weld prep dimensions shift, and the entire assembly sequence stalls. I’ve seen project teams in West Africa hold an entire container at the port because the wall thickness measured 0.3mm below spec on three random samples. The mill certificate looked perfect on paper, but the physical material told a different story. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
For buyers consolidating structural steel from multiple product categories — pipes, beams, plates — dimensional consistency across all members becomes critical. A square tube that’s nominally 100×100mm but arrives at 98mm creates gaps at welded connections that no amount of field adjustment can fix cleanly.
How S355JR and Q235B Match Structural Frame Requirements
S355JR square tubes serve load-bearing frames in commercial buildings and industrial facilities where higher yield strength reduces member sizes and overall weight. The S355JR ERW square steel tube supplier base in China produces this grade to EN 10219 standards, ensuring compatibility with European structural design codes. For projects in regions following GB or JIS specifications, Q235B and SS400 provide equivalent performance at lower cost points. Cold rolled finish delivers the dimensional accuracy that bolted connections demand, while galvanized options address corrosion exposure in outdoor or high-humidity environments.
Engineering Compliance and Certification Pathways
Structural hollow sections must comply with regional building codes — EN 10219 for cold-formed welded sections in Europe, ASTM A500 for North American projects, and GB/T 6728 for domestic Chinese construction. CE certification to EN 10210/EN 10219 is non-negotiable for EU market entry; customs authorities routinely reject shipments lacking proper Factory Production Control documentation. [NEED_CITE: CE marking requirements for structural steel hollow sections] Material traceability through heat numbers on mill test certificates allows project inspectors to verify chemical composition and mechanical properties against the specified grade. For infrastructure projects requiring third-party verification, SGS or BV inspection before shipment provides independent confirmation of compliance.
Understanding Steel Grade Selection and ERW Process Characteristics
The S-series grades (S235JR, S275JR, S355JR) follow European EN standards with increasing yield strength — selecting S355JR over S235JR allows thinner wall sections for equivalent load capacity, reducing material weight and shipping costs. Q235B (Chinese GB standard) and SS400 (Japanese JIS standard) occupy similar strength ranges but differ in chemical composition limits and testing protocols. ERW welding produces a longitudinal seam through electric resistance heating without filler metal, creating a cost-effective alternative to seamless tubes for structural applications where internal pressure is not a design factor. Cold rolling after welding improves surface finish and tightens dimensional tolerance to ±1%, critical for precision fabrication work. [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500 standards]
Galvanized surface treatment adds zinc coating for corrosion protection in outdoor applications, while spangle-controlled finishes (normal, minimized, or spangle-free) address aesthetic requirements for architectural exposure. The choice between cold rolled and galvanized depends on service environment — indoor structural frames typically use cold rolled, while outdoor infrastructure members benefit from zinc protection.
Hidden Costs of Material Non-Conformance
Ordering S355JR square tubes that arrive with Q235B chemistry creates structural liability — the lower yield strength may pass visual inspection but fails under design loads, forcing complete member replacement. Missing or incomplete mill test certificates delay customs clearance for weeks, demurrage charges accumulate, and project timelines slip. [NEED_CITE: consequences of missing material certification in construction projects] Negative tolerance abuse — where actual wall thickness consistently falls below nominal — reduces load capacity and voids structural engineer sign-off. The cost of re-inspection, replacement material, and schedule delay typically exceeds any initial price savings from questionable suppliers.
Why Procurement Teams Source S355JR ERW Square Tubes From Us
Factory-direct pricing eliminates trading company margins — our three production lines running simultaneously deliver monthly capacity exceeding 20,000 tons across 2,800+ specifications. Every batch carries original mill test certificates with full heat number traceability; our in-house laboratory conducts three-stage inspection covering chemical composition, mechanical properties, and dimensional verification. CE certification to EN 10210/EN 10219 and ISO 9001:2015 quality management ensure compliance documentation meets European and international requirements. Third-party inspection through SGS or BV is available upon request before shipment. For non-standard sizes or custom lengths beyond our stock range, typical production lead times apply with flexible MOQ starting from 1 ton for trial orders. Professional export teams handle container loading optimization — consolidating square tubes with beams, plates, and pipes in mixed containers reduces shipping costs for multi-category procurement.
Documentation & Compliance
- Mill test certificate documenting S355JR chemical composition and mechanical properties per EN 10219, with heat number traceability
- CE certificate confirming EN 10210/EN 10219 compliance for structural hollow sections entering European markets
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report available for independent verification before shipment
- Material traceability documentation linking each bundle to specific heat numbers and production batches
- Complete customs documentation including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Cold rolled S355JR square tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Galvanized square tubes packed with waterproof wrapping to preserve zinc coating integrity in humid shipping conditions
- Container loading optimization for 6m/8m/12m lengths maximizes payload while maintaining weight distribution for heavy structural sections
- Custom cutting services available for non-standard lengths, reducing on-site waste and handling
- Heat number and steel grade markings stenciled on each bundle for site identification and inspection traceability
- FOB, CIF, and DDP shipping terms available with professional documentation handling for customs clearance
Requesting Quotation and Technical Verification
Submit your specification requirements — steel grade, dimensions, wall thickness, length, quantity, and destination port — to receive competitive factory-direct pricing with volume discount consideration. For non-standard sizes outside our 2,800+ specification stock range, custom production quotes include lead time and MOQ confirmation. Mill test certificates and CE documentation are provided with every order; third-party inspection arrangements can be confirmed before production begins.
Start Your S355JR ERW Square Steel Tube Inquiry
Send specifications via email or WhatsApp to receive pricing and material certification within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxinjiyuan.com
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
Frequently Asked Questions
Q: How do S355JR, Q235B, SS400, and A36 compare across different international standards?
A: These grades represent equivalent strength ranges across different standard systems — S355JR (EN 10219, European), Q235B (GB/T 6728, Chinese), SS400 (JIS G3466, Japanese), and A36 (ASTM A500, American). While yield strength ranges overlap, chemical composition limits and testing protocols differ. Our mill test certificates specify the exact grade produced, and we can provide equivalence documentation for project engineers reviewing material substitutions.
Q: Can you provide mill test certificates and arrange third-party inspection?
A: Every batch ships with original mill test certificates documenting chemical composition and mechanical properties with full heat number traceability. Third-party inspection through SGS or BV is available upon request — we coordinate inspection scheduling at our facility before shipment, and the inspection report is included in your documentation package.
Q: What is the minimum order quantity for non-standard square tube sizes?
A: MOQ starts from 1 ton for both standard and custom specifications. For non-standard dimensions outside our 2,800+ specification stock range, custom production applies with typical lead times confirmed at quotation stage. Trial orders are welcome for new customers evaluating material quality before committing to larger volumes.
Q: When should I choose cold rolled versus galvanized surface treatment?
A: Cold rolled finish provides dimensional accuracy and smooth surface for indoor structural applications, painted finishes, or fabrication work where surface appearance matters. Galvanized treatment adds zinc coating for corrosion protection in outdoor environments, high-humidity conditions, or applications where maintenance access is limited. Spangle-free galvanized options address aesthetic requirements for architectural exposure.
Q: How do you optimize container loading for heavy square tubes?
A: Our export team calculates optimal loading plans based on your specific dimensions and lengths, maximizing container payload while maintaining weight distribution. For mixed procurement — square tubes combined with beams, plates, or pipes — we consolidate multiple product categories in single containers, reducing per-unit shipping costs and simplifying customs documentation.
