Description
Vertically Integrated Mill & Fabrication — Seamless square and rectangular steel tubes produced from our own billet through finished section, with heat-number traceability across every delivery.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B / Q345B / S235JR / S355JR / SS400 Seamless Square and Rectangular Steel Tube |
| Product Type | Seamless Square and Rectangular Steel Tube (Seamless Hollow Section) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400, S235JR, S355JR |
| Standard | ASTM |
| Section Shape | Square, Rectangular, Round |
| Size Range | Wall Thickness 0.5–200 mm |
| Length | 12 m |
| Technique | Cold Rolled / Hot Rolled / Seamless |
| Surface Treatment | Hot Rolled (Consumer’s Requirement) |
| Tolerance | ±1% |
| Ends | As per customer requirement |
| Application | Construction building material, Steel structures, Architectural decoration, Furniture manufacturing, Fluid pipe, Boiler pipe, Drill pipe, Hydraulic pipe, Gas pipe |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Structural Steel Fabrication | Building frames, column and beam assemblies, truss systems for commercial and industrial construction |
| Petrochemical & Energy | Fluid transfer lines, gas piping, hydraulic systems, boiler circuits in refinery and power plant projects |
| Infrastructure & EPC | Platform structures, stairway supports, conveyor frames for transport and logistics facilities |
| Architectural & Interior | Decorative hollow sections, furniture frames, exhibition structures requiring clean geometry |
What Wall-Thickness Tolerance Costs on a Seamless Square and Rectangular Steel Tube Order
A ±1% tolerance on heavy-wall seamless sections is the difference between passing third-party inspection and losing a container at the port.
When buyers source seamless square and rectangular steel tubes from overseas fabricators, the most common failure point is not the steel grade itself — it is the wall thickness drifting into negative tolerance beyond what the purchase order allows. On a 200 mm wall section, even a small percentage shift changes the theoretical weight, the load-bearing calculation, and ultimately the inspector’s verdict. I have seen entire shipments held at destination because the fabricator’s mill ran light on wall and the buyer’s engineer refused to sign off. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements] With our own mill running three production lines and over 2,800 raw material specifications in stock, every tube is measured root-to-tip before it leaves the workshop, and the report travels with the cargo.
How Heavy-Wall Seamless Sections Match Structural and Pressure Applications
Seamless square and rectangular steel tubes in Q235B, Q345B, S235JR, and S355JR grades carry load through uniform wall geometry without a weld seam — a critical advantage when the section must resist torsion, internal pressure, or cyclic fatigue. For steel frame structures and building material applications, the seamless process delivers consistent bending strength across the full 12 m length. In fluid, gas, hydraulic, and boiler pipe systems, the absence of a longitudinal weld removes the weakest point under internal pressure. Our vertically integrated supply chain means the billet chemistry is controlled from our own steel mill, so the finished seamless square and rectangular steel tube carries full heat-number traceability back to the original cast.
Engineering Compliance and Certification Pathways for Global Projects
Structural engineers specifying seamless square and rectangular steel tubes for load-bearing frames typically reference design codes such as EN 1993 or AISC, which demand documented material properties and dimensional conformity. For European markets, compliance with EN 10219 or EN 10210 cold-formed and hot-formed hollow section standards governs tolerance, chemistry, and impact testing requirements. [NEED_CITE: steel grade equivalence between EN 10219 and ASTM standards] In North America, ASTM A500 and A53 remain the default specification for structural hollow sections. The ±1% wall thickness tolerance on our seamless sections supports compliance across these frameworks, while the 12 m standard length reduces on-site splicing for long-span structures. Third-party inspection through SGS, BV, or TÜV can be arranged before shipment to satisfy project-specific QA protocols.
Steel Grade Selection and Seamless Manufacturing Process
The Q-series (Q235B, Q345B) and S-series (S235JR, S355JR) represent Chinese and European structural steel grading systems respectively, with SS400 covering the Japanese equivalent. Moving from Q235B to Q345B or from S235JR to S355JR increases the minimum yield strength, allowing engineers to reduce section size for the same load — a direct cost saving on tonnage and welding hours. The seamless manufacturing process, whether hot rolled or cold rolled, produces a hollow section with no longitudinal weld, giving superior torsional resistance and more uniform stress distribution compared to ERW alternatives. [NEED_CITE: seamless vs ERW hollow section structural performance comparison] Surface treatment remains hot rolled as standard, with oiled or non-oiled finish available depending on the downstream coating requirement. For architectural decoration and furniture manufacturing, the smooth hot-rolled surface and regular geometry of seamless sections reduce preparation work before painting or powder coating.
Hidden Costs of Buying Seamless Hollow Sections Without Verified Traceability
Choosing a supplier who cannot prove heat-number traceability from billet to finished tube creates risk at three points: customs clearance, engineering inspection, and long-term structural integrity. Material certificates fabricated after shipment do not satisfy EN 10204 3.1 requirements, and inspectors at major ports increasingly reject documentation that cannot be cross-referenced to the producing mill’s records. [NEED_CITE: EN 10204 3.1 inspection document requirements for structural steel] Wall thickness outside tolerance forces the buyer into a choice — accept reduced load capacity or pay for re-fabrication. Negative tolerance beyond the specified ±1% range means the actual weight delivered is less than invoiced, a cost that only becomes visible when the third-party surveyor weighs the bundle.
Why Engineering Procurement Teams Source Seamless Square and Rectangular Steel Tubes From XJY Structure
Our own steel mill with three production lines and over 2,800 raw material specifications means we control chemistry and tolerance from the billet stage — not just the finishing stage. Every seamless square and rectangular steel tube leaves our workshop with a mill test certificate showing chemical composition and mechanical properties tied to the original heat number. We hold ISO 9001 certification and can arrange SGS, BV, or TÜV third-party inspection before loading. The ±1% wall thickness tolerance is verified by ultrasonic measurement on every piece, not sampled. For projects requiring custom end finishing, specific surface treatment, or non-standard lengths, our engineering team reviews shop drawings and confirms feasibility before the contract is signed. Professional loading plans for oversized and heavy-wall sections ensure container utilization is maximized without damaging the tube ends during ocean transit.
Documentation & Compliance
- Mill Test Certificate documenting Q235B / Q345B / S235JR / S355JR chemical composition and mechanical properties per ASTM, with heat number traceability to our own steel mill
- CE certificate covering EN 10219 / EN 10210 compliance for seamless square and rectangular steel tubes exported to European Union markets
- ISO 9001 quality management system certificate covering the full production process from billet procurement through finished tube dispatch
- SGS or BV third-party inspection report available upon request, covering dimensional checks, wall thickness measurement, and visual surface inspection
- Material traceability sheet linking each bundle to the original heat number, production date, and test batch
- Full customs documentation package including packing list, bill of lading, and certificate of origin for seamless square and rectangular steel tube shipments
Packaging, Loading & Delivery
- Seamless square and rectangular steel tubes bundled with steel strips and edge protectors, sized to suit the 12 m standard length and wall thickness up to 200 mm
- Non-oiled hot rolled surface protected by waterproof wrapping for ocean transit, preventing rust formation on Q235B and Q345B grades during extended shipping
- Container loading plan optimized for heavy-wall seamless sections, maximizing payload within the 5 Ton MOQ while protecting tube ends from impact damage
- Heat number and steel grade marked on each tube end with stenciled identification, matching the mill test certificate for on-site verification
- FOB, CIF, and DDP delivery terms available, with door-to-door logistics coordination for EPC projects across the Middle East, Southeast Asia, and Africa
- Custom cutting to non-standard lengths available upon request, with cut ends deburred and protected before bundling
How to Request a Quotation for Seamless Square and Rectangular Steel Tubes
Submit your project drawings, required steel grade (Q235B, Q345B, S235JR, S355JR, or SS400), wall thickness, and destination port — our engineering team responds within 24 hours with a detailed quotation including material, fabrication, coating, and shipping costs. For projects requiring third-party inspection or specific certification documentation, confirm the requirement at inquiry stage so the mill test certificate and inspection arrangement are included in the production plan.
Start Your Seamless Square and Rectangular Steel Tube Inquiry Today
Send your specifications and drawings to receive a detailed quotation with full mill test certificate documentation and production schedule.
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
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
Frequently Asked Questions
Q: What is the steel grade equivalence between Q235B, S235JR, and SS400 for seamless square and rectangular steel tubes?
A: Q235B (Chinese GB standard), S235JR (European EN standard), and SS400 (Japanese JIS standard) are broadly equivalent in yield strength and chemical composition for general structural applications. The primary difference lies in the impact testing requirements and the specific standard framework referenced in the project specification. Our mill test certificate documents the exact chemistry and mechanical properties so your engineer can verify compliance with the governing design code.
Q: When should I specify seamless square and rectangular steel tubes over ERW welded alternatives?
A: Seamless sections are preferred when the application involves internal pressure, torsional loading, or cyclic fatigue — conditions where a longitudinal weld seam represents a potential failure point. For heavy-wall sections above standard ERW capacity, the seamless process also provides more uniform wall thickness distribution. Our production covers wall thickness up to 200 mm in seamless process, suitable for high-load structural and mechanical applications.
Q: How does XJY Structure guarantee material traceability for seamless square and rectangular steel tubes?
A: Every tube is produced from billet sourced through our own steel mill, with the heat number recorded at each production stage. The mill test certificate issued with each shipment documents the chemical composition and mechanical properties linked to that heat number. Third-party inspection through SGS, BV, or TÜV can be arranged before shipment to independently verify the material properties and dimensional accuracy.
Q: What surface treatment options are available for seamless square and rectangular steel tubes?
A: Standard delivery condition is hot rolled with non-oiled finish. Depending on the project environment and downstream coating requirement, oiled finish, painted coating, or galvanized treatment can be arranged. For architectural decoration and furniture manufacturing applications, the smooth hot-rolled surface provides an excellent base for powder coating or liquid paint application.
Q: What is the delivery timeline and packing method for oversized seamless square and rectangular steel tubes?
A: Typical production lead times apply once the contract and deposit are confirmed and shop drawings are approved. Standard length is 12 m, bundled with steel strips and edge protectors for seaworthy packaging. Heavy-wall and oversized sections are loaded according to a professional stowage plan to maximize container utilization and protect the tube ends during ocean transit. Full export documentation and tracking are provided until site delivery.
