Description
Factory Direct Mill Source — Raw steel from our own production lines feeds directly into ERW square tube fabrication, eliminating third-party material gaps for S235JR, A36, and S355 grades.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S235JR / A36 / S355 / SS400 ERW Welded Square Steel Pipe |
| Product Type | Welded Square Steel Tube (ERW) |
| Steel Grade | S235JR, A36, S355, SS400, Q235B |
| Standard | ASTM A500, EN10219, EN10210, JIS G3466, GB/T 6728 |
| Section Shape | Square |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Cold Rolled / Galvanized (optional per customer requirement) |
| Tolerance | ±1% |
| Length | Customized |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Invoicing | By Theoretical Weight |
| Oiled or Non-oiled | Non-oiled |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Building & Construction | Steel frame structures for factories, stadiums, and commercial centers including trusses, beams, and columns |
| Machinery Manufacturing | Machine tool frames, conveyor support frames, and automation equipment bases requiring high torsional stiffness |
| Home Decor & Furniture | Stair handrails, security window frames, and structural furniture frames |
| Infrastructure | Auxiliary bridge structures, stage trusses, and greenhouse support frameworks |
| Vehicle Manufacturing | Trailer chassis and recreational vehicle frame structures |
Where Negative Tolerance Exceeds the Limit — And Costs You Three Weeks at Port
A 0.4mm wall thickness deviation on a 50×50×3 ERW square tube held an entire shipment at Jebel Ali for 21 days.
When overseas buyers source welded square steel tubes from China, the distance between the mill and the job site makes quality verification nearly impossible until the containers arrive. Third-party re-inspection at destination ports routinely catches wall thickness negative tolerance exceeding acceptable limits — and by then, rework is not an option. The S235JR S355 ERW welded square steel tube supplier you choose must control raw material procurement and fabrication under one quality system, not source blanks from unknown mills and weld them in a separate workshop. [NEED_CITE: EN 10219 cold-formed structural hollow section dimensional tolerance requirements]
How ERW Square Tubes Match Structural Frame Demands
S235JR and S355 grades in ERW welded square steel tube form deliver the torsional rigidity that structural frames demand — whether you are erecting warehouse columns in Southeast Asia or building conveyor support structures in a Middle East industrial plant. The electric resistance welding process produces a clean, consistent seam that integrates into moment-resisting connections without introducing stress concentrations typical of lower-quality welds. Our fabrication division handles cutting, punching, and bending to project-specific dimensions, so your site crew receives components ready to bolt — not raw stock that needs secondary processing under tropical heat.
Engineering Compliance Across EN, ASTM, and JIS Frameworks
Structural steel procurement for international projects must satisfy the design code of the destination country. EN 10219 governs cold-formed welded structural hollow sections for European projects, while ASTM A500 applies to North American construction, and JIS G3466 covers general structural use in Japanese-spec infrastructure. The S235JR S355 ERW welded square steel tube supplier must provide mill test certificates traceable to each heat number, along with CE marking documentation for EU customs clearance. [NEED_CITE: steel grade equivalence mapping between EN 10219 and ASTM A500 standards] Choosing the correct surface treatment — galvanized for coastal or high-humidity environments, cold rolled for indoor structural applications — directly affects long-term corrosion performance and maintenance intervals.
Understanding ERW Welding, Steel Grade Selection, and Tolerance Impact
The ERW process passes electric current through the steel strip edges to create a forge weld without filler material, producing a seam strength that approaches the parent metal. This makes ERW welded square tubes suitable for structural applications where seam integrity matters — unlike SSAW pipes designed for large-diameter fluid transport. Steel grade selection directly affects load-bearing capacity: S235JR serves general structural purposes, while S355 offers higher yield strength for heavily loaded columns and long-span trusses. The Q235B grade aligns with Chinese domestic projects, while SS400 meets Japanese industrial specifications. Wall thickness tolerance of ±1% ensures that theoretical weight invoicing matches actual structural performance — a critical factor when engineers calculate dead load and connection design. [NEED_CITE: ERW versus seamless versus SSAW welding process comparison for structural applications]
The Hidden Cost of Unverified Material Sources
Purchasing ERW square tubes from a trader who sources steel from multiple uncontrolled mills creates a chain of liability gaps. When wall thickness falls below minimum specification, the structure fails load testing. When chemical composition deviates from the declared grade, welding procedures produce brittle joints. When mill test certificates cannot be traced to actual heat numbers, customs authorities reject the shipment or the project engineer refuses to sign off. [NEED_CITE: consequences of non-compliant structural steel in international construction projects] These failures do not show up in the purchase order — they surface during third-party inspection at destination, during structural loading tests, or years later when corrosion penetrates an inadequately protected surface.
Why Sourcing From an Integrated Mill and Fabrication Facility Matters
Our own steel production facility operates three production lines with over 2,800 specifications of raw material in stock, feeding directly into the XJY Structure fabrication division. This vertical integration means the S235JR, S355, and A36 steel grades in your order come from our own melt shop — not from a third-party merchant whose material certificates you cannot verify. Every ERW welded square steel tube undergoes dimensional inspection with calibrated thickness gauges before leaving the workshop, because we learned the hard way that a 0.4mm deviation at destination port means a three-week delay and a damaged reputation. Our engineering team reviews shop drawings, optimizes material usage, and prepares complete quality documentation packages including WPS, PQR, weld maps, and coating reports — the same documentation that EU and Middle East project inspectors require.
Documentation & Compliance
- Mill test certificate documenting S235JR, S355, and A36 chemical composition and mechanical properties per EN10219 and ASTM A500, traceable to individual heat numbers
- CE certificate confirming EN10219 / EN10210 compliance for structural hollow sections entering European Union markets
- ISO 9001 quality management system certification covering the full production chain from raw steel to fabricated components
- SGS or BV third-party inspection reports available for dimensional verification, welding quality assessment, and coating thickness measurement before shipment
- Complete material traceability linking each S235JR S355 ERW welded square steel tube bundle to its original heat number and production batch
- Full customs documentation package including packing list, bill of lading, and certificate of origin for smooth port clearance
Packaging, Loading & Delivery
- ERW welded square steel tubes bundled with high-tensile steel strips and edge protectors to maintain ±1% dimensional tolerance during ocean transit
- Galvanized surface treatment preserved through waterproof wrapping and separation layers preventing zinc coating abrasion between nested tubes
- Custom-length S355 and S235JR tubes loaded with optimized container stowage plans maximizing 20ft and 40ft payload while protecting tube ends from deformation
- Heat number and steel grade stenciled on each bundle for on-site identification and traceability verification during project installation
- FOB, CIF, and DDP shipping terms available with professional oversized cargo loading plans for long-length structural members exceeding standard container dimensions
Getting Your Quote With Full Material Certification
Share your project drawings in PDF or DWG format along with required steel grades, section dimensions, quantities, and destination port. Our engineering team responds within 24 hours with a detailed quotation covering material, fabrication, surface treatment, packing, and shipping costs — including the complete mill test certificate and CE documentation package your project inspector will require.
Start Your S235JR S355 ERW Welded Square Steel Tube Inquiry
Submit your specifications and steel grade requirements to receive a detailed quotation with full mill test certification.
Company: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Frequently Asked Questions
Q: What is the difference between S235JR and S355 steel grades for ERW welded square tubes?
A: S235JR and S355 are both European standard structural steel grades under EN 10219, but S355 offers higher yield strength than S235JR, making it suitable for heavily loaded structural members such as long-span trusses and high-rise columns. Both grades are available in our ERW welded square steel tube range with full mill test certification and CE compliance documentation.
Q: Can you provide third-party inspection before shipment for overseas buyers?
A: Yes, we welcome SGS, BV, or TUV third-party inspection for dimensional verification, welding seam quality assessment, surface treatment coating thickness measurement, and material traceability checks. The S235JR S355 ERW welded square steel tube supplier should always support independent verification — we schedule inspections after fabrication completion and before container loading.
Q: How do you handle negative tolerance on wall thickness for ERW square tubes?
A: Our production maintains ±1% dimensional tolerance on all ERW welded square steel tubes, verified by calibrated ultrasonic thickness gauges on every bundle before dispatch. Each mill test certificate documents actual measured wall thickness against the ordered specification, ensuring compliance with EN10219 and ASTM A500 requirements.
Q: What surface treatment options are available for corrosion protection?
A: We offer cold rolled finish for indoor structural applications and hot-dip galvanized coating for outdoor, coastal, or high-humidity environments. Surface treatment selection depends on your project’s environmental exposure conditions and design service life requirements. Our fabrication team can advise on the appropriate treatment based on your application.
Q: Do you provide custom cutting and fabrication services for ERW square tubes?
A: Yes, our fabrication division offers CNC cutting, punching, bending, and welding services to project-specific drawings. We can deliver S235JR, S355, and A36 ERW welded square steel tubes pre-cut to your required lengths with connection holes drilled and ends prepared — reducing on-site fabrication time and material waste at your project location.
Request Your Quotation With Full Certification Package
Send your project drawings and steel grade specifications to receive pricing with complete mill test certificates and export documentation.
Company: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
