Description
Factory-Direct Welded Square Tubes — S235JR, S355, Q235B grades produced on our own ERW lines with ±1% tolerance, shipped with full mill test certificates to 50+ countries.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S235JR / S355 / Q235B Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube |
| Steel Grade | S235JR, A36, S355, SS400, Q235B |
| Standard | BS, EN, GB, AISI, ASTM, DIN, JIS, ASTM A500, EN10219, EN10210, JIS G3466, GB/T 6728 |
| Section Shape | Square |
| Technique | Welded (ERW) |
| Surface Treatment | Cold Rolled (Galvanized available upon request) |
| Tolerance | ±1% |
| Length | Customized |
| Thickness | Customized |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Invoicing | By Theoretical Weight |
| Alloy Or Not | Non-Alloy |
| Oiled or Non-oiled | Non-oiled |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Building & Construction | Trusses, beams, columns for factories, stadiums, commercial centers |
| Machinery Manufacturing | Machine tool frames, conveyor support, automation equipment |
| Home Decor & Furniture | Stair handrails, security windows, furniture frames |
| Infrastructure | Bridge auxiliary structures, stage trusses, greenhouse frames |
| Vehicle Manufacturing | Trailer chassis, RV frames |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
Tight tolerance on cold rolled welded square steel tubes determines whether your frame passes third-party inspection or gets rejected at the port.
I have seen entire container loads of square tubes held up at Santos because the wall thickness drifted beyond acceptable limits — theoretical weight invoiced, but actual weight told a different story. When tolerance widens, the structural engineer’s load calculations no longer match the material on site, and the entire batch becomes questionable [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]. Beyond the material cost, you pay for re-inspection, delayed erection schedules, and sometimes full replacement. That is why our High Strength Cold Rolled Welded Square Steel Tube Supplier capability holds ±1% tolerance as a non-negotiable baseline, verified in-house before every shipment leaves Jinan.
Matching Structural Loads and Connection Geometry
Cold rolled welded square steel tubes in S235JR, S355, and Q235B grades deliver the dimensional consistency needed for moment-resisting frames and braced structures where connection plates must sit flush against flat surfaces. The cold rolled finish provides a smooth, uniform profile suitable for exposed architectural applications, while the ERW seam runs continuously along the length without interrupting load paths. For projects combining square tubes with H-beams or channels, sourcing from a single supplier eliminates mismatched tolerances that cause fit-up problems during steel erection.
Engineering Compliance and Certification Pathways
Structural hollow sections used in load-bearing frames must comply with recognized standards — EN 10219 for cold-formed welded structural hollow sections in Europe, ASTM A500 for North American projects, and GB/T 6728 for domestic Chinese construction [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500 standards]. The High Strength Cold Rolled Welded Square Steel Tube Supplier you choose must provide mill test certificates traceable to heat numbers, CE marking for EU customs clearance, and third-party inspection reports when the project specification demands SGS or BV verification. Custom cut lengths reduce on-site welding and grinding, while punched or bent sections arrive ready for bolted or welded connections.
Steel Grade Selection and ERW Welding Principles
S235JR serves general structural applications where moderate strength and good weldability are required, conforming to EN 10025. S355 offers higher yield strength for heavier frames and longer spans, while Q235B remains the workhorse grade in Chinese-specification projects. A36 and SS400 cover ASTM and JIS requirements respectively, allowing the same physical tube to satisfy multiple international standards depending on certification documentation. The ERW welding process forms the square profile from cold rolled coil, with the longitudinal seam welded under controlled conditions and then normalized to restore uniform mechanical properties across the cross-section. Cold rolled surface treatment delivers tighter dimensional accuracy and smoother finish compared to hot rolled alternatives, making it preferable for architectural facades and precision machinery frames.
Hidden Costs of Incorrect Grade or Missing Certification
Ordering S235JR when the structural design calls for S355 means the frame may pass visual inspection but fail load testing, requiring complete dismantling and replacement. Shipping tubes without CE marking to EU ports triggers customs holds that delay projects by weeks, while missing mill test certificates prevent the client’s quality engineer from approving the material for use [NEED_CITE: CE marking requirements for structural steel under EN 10210]. Theoretical weight invoicing without tight tolerance control leads to disputes when actual weight deviates, and without proper packaging, cold rolled surfaces arrive scratched or dented, requiring costly rework or rejection.
Why Source from SD XJY Pipe
We operate three dedicated production lines covering over 2,800 specifications in square and rectangular tubes, with wall thicknesses reaching 40mm for heavy structural applications. Our in-house physical and chemical laboratory tests every heat for composition and mechanical properties before release, and we hold 41 invention patents including China’s original sharp-corner rectangular tube technology for projects requiring clean architectural lines. Full international certifications — ISO 9001:2015, Lloyd’s CE under EN 10210/EN 10219, Singapore FPC, and SGS/BV verification — ensure your High Strength Cold Rolled Welded Square Steel Tube Supplier meets the compliance requirements of regulated markets. Custom non-standard sizes, cutting, punching, and bending services reduce your on-site fabrication labor, while professional container loading with anti-damage measures prevents the bending and surface defects that plague poorly packed shipments.
Documentation & Compliance
- Mill test certificate documenting S235JR, S355, or Q235B chemical composition and mechanical properties per EN 10219 or ASTM A500 as specified
- CE certificate under EN 10210/EN 10219 for structural hollow sections entering EU member states
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report available upon request for project-specific quality verification
- Material traceability by heat number linking each tube to its original coil and test results
- Export customs documents including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Cold rolled welded square steel tubes bundled with steel strips and edge protectors to preserve surface finish during ocean transit
- Custom cut lengths loaded in dedicated containers with wooden cradles to prevent bending of long sections
- Heat number and steel grade stenciled on each tube for site identification and traceability verification
- Galvanized option available with additional packaging measures to protect zinc coating from moisture condensation
- FOB, CIF, and DDP shipping terms with professional container loading plans optimized for square tube geometry
- Typical production lead times for custom sizes, with standard specifications available from stock
Requesting Quotation and Technical Review
Submit your drawing or specification listing section size, wall thickness, steel grade, length, quantity, and destination port to receive a detailed quotation with unit pricing, production timeline, and applicable certifications. Our technical team reviews each inquiry within 12 hours and provides mill test certificate samples from recent production runs for your quality engineer’s approval. For non-standard sizes or custom processing including punching, cutting, or bending, we provide fabrication drawings for your confirmation before production begins.
Frequently Asked Questions
Q: How do S235JR, S355, Q235B, and A36 compare across different standards?
A: These grades represent equivalent structural steel specifications under different standardization systems — S235JR and S355 follow EN standards, Q235B follows Chinese GB standards, and A36 follows ASTM. We provide cross-reference documentation and can supply mill test certificates showing compliance with your required standard.
Q: What is the minimum order quantity for customized thickness and length?
A: We accept custom orders for non-standard thickness and length with flexible MOQ depending on the specific size range. Contact us with your exact requirements for a tailored quotation.
Q: What surface treatment options are available for different environments?
A: Cold rolled finish provides smooth surface suitable for indoor or painted applications. Galvanized coating is available upon request for corrosion protection in outdoor or humid environments. Hot rolled option offers cost savings for applications where surface appearance is not critical.
Q: Do your products carry CE marks for EU import clearance?
A: Yes, our structural hollow sections carry CE certification under EN 10210 and EN 10219, issued by Lloyd’s Register. We also hold Singapore FPC certification and can arrange SGS or BV third-party inspection for specific project requirements.
Q: How is theoretical weight invoicing calculated and what tolerance applies?
A: We invoice by theoretical weight calculated from nominal dimensions, with dimensional tolerance held at ±1% as standard. Actual weight verification is available through third-party inspection if required by your project specification.
Get Your High Strength Cold Rolled Welded Square Steel Tube Quotation Today
Send your specification with section size, steel grade, quantity, and destination to receive pricing and mill test certificate samples within 12 hours.
Contact: SD XJY Pipe
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
