Description
Factory-Direct ERW Square Tubes — Every heat number verified against in-house lab results before container sealing.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S355JR / Q235B ERW Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube (ERW) |
| Steel Grade | S235JR, S355JR, S355, Q235B, SS400, A36 |
| Standard | ASTM A500, EN 10219, EN 10210, JIS G3466, GB/T 6728 |
| Section Shape | Square |
| Technique | ERW (Electric Resistance Welded) |
| Length | Customized |
| Tolerance | ±1% |
| Surface Treatment | Cold Rolled / Galvanized (optional) |
| Oiled or Non-oiled | Non-oiled |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Invoicing | By Theoretical Weight |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Steel Structure Construction | Factory building frames, stadium roof trusses, commercial center columns |
| Machinery Manufacturing | Machine tool frames, conveyor support structures, automation equipment bases |
| Home Decor & Furniture | Stair handrails, security window frames, furniture support frames |
| Infrastructure Construction | Bridge auxiliary structures, stage trusses, greenhouse frame systems |
| Vehicle Manufacturing | Trailer chassis frames, RV structural frames |
What Dimensional Tolerance Actually Costs on a Structural Frame Order
A ±1% tolerance on an ERW welded square steel tube means the difference between a frame that bolts together on-site and one that requires field rework.
When procurement teams order standard ERW tubes without verifying tolerance claims, corner deviation and wall thinning compound across dozens of members. By the time the steel reaches the job site, bolt holes no longer align, gusset plates sit at angles, and the structural fitter is cutting and re-welding connections that should have been straightforward. On a commercial center frame with hundreds of square tube connections, that tolerance drift translates directly into labor hours and crane time burned on correction rather than assembly. We have seen orders rejected at destination because the cross-section diagonal measured outside acceptable limits — not because the steel was weak, but because it was geometrically wrong. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed structural hollow sections]
Matching ERW Square Tubes to Structural and Fabrication Demands
An ERW welded square steel tube in S355JR or Q235B serves load-bearing frames where torsional resistance matters more than internal pressure containment. The flat internal surfaces and sharp external corners allow direct bearing contact with gusset plates and connection brackets — no filler shims needed. For machinery manufacturers building conveyor structures and automation equipment bases, the ±1% tolerance ensures precision jig fixtures accept every member without adjustment. When the same tube is specified for greenhouse frames or bridge auxiliary structures, the customized length capability eliminates on-site cutting waste, and the optional galvanized surface treatment handles corrosion exposure without additional field coating.
Engineering Compliance and Certification Requirements
Structural frames for factories and stadiums must comply with design codes referencing EN 10219 for cold-formed welded hollow sections or ASTM A500 for the North American market. The steel grade selection — S355JR for European-spec projects, Q235B for domestic Chinese standard structures, SS400 for Japanese-engineered facilities — determines the yield strength class the structural engineer calculates against. CE certification under EN 10210/EN 10219 is mandatory for EU market entry; without it, customs clearance fails regardless of physical material quality. [NEED_CITE: CE marking requirements for structural steel hollow sections under EN 10210] For projects requiring third-party verification, SGS or BV inspection can be arranged before shipment, with heat number traceability documented from raw coil through finished tube.
Understanding Steel Grades and ERW Welding Process
The S-series grades (S235JR, S355JR) follow the European EN standard system where the number indicates minimum yield strength in MPa for thicknesses up to 16mm. The Q-series (Q235B) follows the Chinese GB system with a similar designation logic. ASTM A36 and JIS SS400 represent the American and Japanese equivalents respectively. Cross-standard equivalence requires careful comparison of chemical composition limits and mechanical property test conditions — not just the nominal yield number. [NEED_CITE: steel grade equivalence mapping between EN 10025, ASTM A36, and GB/T 700] The ERW welding process forms the square cross-section by cold-forming a flat steel strip through progressive roll stands, then welding the longitudinal seam through electric resistance heating. This method produces tight dimensional tolerance and smooth surface finish suitable for architectural exposure, at a lower cost than seamless alternatives for non-pressure applications. The optional galvanized surface treatment adds a zinc coating layer for outdoor or humid environment corrosion protection, while cold-rolled finish provides a cleaner surface for painting or powder coating.
Hidden Costs of Procuring Without Verified Certification
Ordering ERW welded square steel tubes based on price alone, without requiring EN 10204 3.1 mill test certificates, creates exposure across the entire project chain. A tube stamped S355JR that actually delivers Q235B-level yield strength will pass visual inspection but fail structural load testing — and the cost of replacing installed members far exceeds the original material savings. Missing CE documentation blocks EU customs clearance, causing demurrage charges and project delays. Negative tolerance abuse — where wall thickness consistently falls below the nominal value — reduces load capacity and violates the structural engineer’s design assumptions. [NEED_CITE: consequences of negative tolerance abuse in structural steel procurement]
Why SD XJY Pipe for ERW Square Tube Procurement
Every heat number is verified against our in-house physical and chemical laboratory results before loading — a practice we adopted after watching a container get rejected at destination because mill paperwork did not match actual material properties. Our 3 production lines cover 2,800+ specifications, meaning your non-standard dimensions do not require sourcing from multiple suppliers. We hold CE certification under EN 10210/EN 10219, ISO 9001:2015, and Singapore FPC — covering EU, international, and Southeast Asian regulatory requirements. Third-party inspection through SGS or BV is arranged on request, with full documentation provided before vessel departure. Custom lengths, cutting, punching, and bending services are performed in-house, reducing your on-site fabrication scope. Professional container loading with anti-damage measures ensures tubes arrive without bending or surface deformation — a detail that matters when the destination crane operator expects straight members ready for installation.
Documentation & Compliance
- Mill test certificate documenting S355JR or Q235B chemical composition and mechanical properties per EN 10219 or GB/T 6728
- CE certificate confirming compliance with EN 10210/EN 10219 for structural hollow sections exported to EU markets
- ISO 9001:2015 quality management system certificate covering the full ERW welded square steel tube production process
- SGS or BV third-party inspection report available upon request, covering dimensional checks, weld seam quality, and mechanical testing
- Full heat number traceability from raw steel coil to finished tube, documented on mill test certificate
- Export customs documents including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- ERW welded square steel tubes bundled with steel strips and edge protectors to prevent corner damage during ocean transit
- Galvanized square tubes wrapped with waterproof paper and plastic film to preserve zinc coating integrity
- Custom-length tubes cut to project-specified dimensions, reducing on-site cutting waste for steel structure contractors
- Heat number and steel grade stenciled on each bundle for site identification and traceability verification
- Professional container loading plan optimized for square tube geometry, maximizing payload per 20ft or 40ft container
- Shipping terms available: FOB, CIF, or DDP to destination port or project site across 50+ countries
Ready to Verify Material Before You Commit
Submit your ERW welded square steel tube requirements — including section dimensions, wall thickness, steel grade, standard, surface treatment, quantity, and destination port — and receive a detailed quotation with mill test certificate sample within 12 hours. For non-standard sizes or custom processing (cutting, punching, bending), we provide a fabrication feasibility review before confirming lead time. Third-party inspection and certification documents are confirmed in the proforma invoice stage, not after production.
Frequently Asked Questions
Q: How do S355JR, Q235B, and A36 compare across different standard systems?
A: S355JR follows EN 10025 with a minimum yield strength designation of 355 MPa for thicknesses up to 16mm. Q235B follows GB/T 700 with a yield strength of 235 MPa. ASTM A36 specifies a minimum yield strength of 250 MPa. Cross-standard equivalence requires comparing full chemical composition and mechanical property ranges, not just the nominal yield number.
Q: Can you provide EN 10204 3.1 mill test certificates and arrange third-party inspection?
A: Yes. Every shipment includes an EN 10204 3.1 mill test certificate documenting chemical composition and mechanical properties per the applicable standard (EN 10219, ASTM A500, or GB/T 6728). SGS or BV third-party inspection is arranged on request before shipment.
Q: What is the MOQ for customized length and processing services?
A: Custom lengths, cutting, punching, and bending services are available with flexible MOQ depending on the specification and processing complexity. Submit your detailed requirements for a specific quotation.
Q: What surface treatment options are available for outdoor applications?
A: We offer cold-rolled finish (suitable for indoor or painted applications), hot-dip galvanized coating (for outdoor corrosion protection), and black non-oiled finish. The choice depends on the installation environment and project specification requirements.
Q: What shipping terms and lead times apply to custom orders?
A: We offer FOB, CIF, and DDP shipping terms. Standard sizes ship from stock; custom sizes and processed orders enter production with typical lead times confirmed at the quotation stage based on specification complexity and order quantity.
Request Your ERW Welded Square Steel Tube Quotation
Send your specifications — section size, wall thickness, steel grade, standard, quantity, and destination — to receive pricing and mill test certificate documentation.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjypipe.com
