Description
Factory-Direct Supply, No Middlemen — every seamless square and rectangular steel tube ships straight from our 3 production lines with mill test certificates attached.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345/S355JR Seamless Square and Rectangular Steel Tube |
| Product Type | Seamless Square and Rectangular Hollow Section |
| Steel Grade | Q195, Q235, Q345, S235JR, S275JR, S355JR, ASTM A53, ASTM A106 |
| Standard | ASTM A53, ASTM A106 |
| Section Shape | Square, Rectangular, Round |
| Size Range | Custom sizes available across 2800+ specifications |
| Wall Thickness | Customizable |
| Length | 6 m, 12 m |
| Technique | Cold Rolled, Hot Rolled, Galvanized, Seamless |
| Surface Treatment | Hot Rolled, Galvanized, Custom finish |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures, Construction frames, Machinery, Fluid transport, Scaffolding, Furniture |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Architecture | Building frames, glass curtain wall supports, architectural facades |
| Industrial Machinery | Conveyor structures, equipment bases, hydraulic cylinder housings |
| Infrastructure | Bridge components, industrial platforms, scaffolding systems |
| Fluid Transport | Pipeline systems, oil and gas conveyance, water distribution networks |
| Furniture & Decoration | Structural frames for commercial furniture, display systems |
Where Wall-Thickness Tolerance Decides Structural Acceptance
A ±1% tolerance on seamless square and rectangular steel tube means the difference between passing inspector sign-off and tearing down a frame.
Project engineers specifying Q345 or S355JR hollow sections for load-bearing frames expect dimensional consistency across hundreds of meters. When wall thickness drifts beyond tolerance, connection plates don’t align, bolt holes miss, and entire sections get rejected at the welding stage. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
We’ve seen orders from Southeast Asian EPC contractors arrive with tubes that looked right on paper but failed caliper checks on site — the supplier had quoted “standard tolerance” without defining it. Our seamless square and rectangular steel tube holds ±1% across every batch, verified by our in-house physical and chemical laboratory before shipment.
Matching Structural Frames and Machinery Bases to Engineering Loads
Seamless square and rectangular steel tube in Q345 and S355JR grades carries higher load capacity than welded alternatives at equivalent wall thickness, making them suitable for construction frames bearing multi-story loads and machinery bases subject to vibration. The seamless manufacturing process eliminates the weld seam — the traditional weak point under cyclic stress — so these tubes perform reliably in scaffolding systems and industrial platforms where fatigue resistance matters. Custom sizes across our 2800+ specification range mean project teams can source exact dimensions without redesigning connections around stock availability.
Engineering Compliance and Certification Requirements
Structural frames destined for EU markets require CE marking under EN 10210 or EN 10219, and our seamless square and rectangular steel tube carries Lloyd’s CE certification covering both standards. North American projects typically specify ASTM A53 or ASTM A106, which we produce with full mill test documentation. [NEED_CITE: steel grade equivalence mapping between ASTM and EN standards] For projects in Singapore or Southeast Asia, we hold Singapore FPC certification, removing a common customs clearance barrier. Every heat number is traceable from raw material to finished tube, so inspectors can verify chemical composition and mechanical properties against the original mill test certificate.
Steel Grade Selection and Manufacturing Process Explained
The Q-series (Q195, Q235, Q345) follows the Chinese GB standard system, where the number indicates minimum yield strength in MPa — Q345 delivers higher load capacity than Q235 for the same cross-section. The S-series (S235JR, S275JR, S355JR) follows EN standards and is required for EU projects; S355JR offers roughly 50% higher yield strength than S235JR, allowing thinner walls and lighter structures. ASTM A53 and A106 serve North American fluid transport and structural applications respectively.
Seamless manufacturing starts from solid billet, pierced and drawn to final dimensions without any welding. This produces uniform grain structure around the entire cross-section — critical for high-pressure fluid transport and load-bearing columns where weld defects could propagate under stress. Hot rolled seamless tube offers cost efficiency for standard structural use, while cold drawn seamless tube delivers tighter dimensional tolerance and smoother surface finish for precision machinery applications.
Surface treatment choice depends on the operating environment: hot rolled finish suits indoor structural frames where appearance is secondary; galvanized coating protects outdoor scaffolding and facades from atmospheric corrosion; custom finishes address specific chemical exposure or aesthetic requirements.
Hidden Costs of Incorrect Material Sourcing
Ordering seamless square and rectangular steel tube without verified mill test certificates risks material substitution — a supplier may ship Q235 when Q345 was specified, and the difference won’t show until load testing or structural inspection. [NEED_CITE: consequences of steel grade mismatch in structural engineering] Missing CE documentation blocks EU customs clearance regardless of physical quality, forcing return shipment or destruction at origin. Negative tolerance abuse — where wall thickness sits consistently below nominal — reduces load capacity and triggers rejection during third-party inspection, delaying project timelines by weeks.
Why Procurement Teams Source From Us
Our 3 production lines cover 2800+ specifications in seamless square and rectangular steel tube, so project teams sourcing mixed-size orders for construction frames and machinery bases deal with a single factory rather than coordinating multiple suppliers. We hold 41 invention patents including China’s original sharp-corner rectangular tube technology — relevant when architectural facades require clean 90-degree corners that standard rounded-corner tubes cannot deliver. Every shipment includes mill test certificates from our in-house laboratory, and we arrange SGS or BV third-party inspection on request. Full international certifications — ISO 9001:2015, Lloyd’s CE (EN 10210/EN10219), Singapore FPC — cover major import markets across 50+ countries. Custom non-standard sizes and定尺 cutting reduce on-site waste, while our professional container loading team prevents the bending and surface damage that plague poorly packed tube shipments.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345/S355JR chemical composition and yield strength per ASTM A53/A106 or EN standards
- CE certificate covering EN 10210 hot-finished and EN 10219 cold-formed hollow sections for EU market clearance
- ISO 9001:2015 quality management certificate covering full production and inspection process
- SGS or BV third-party inspection report available for project-specific verification requirements
- Material traceability by heat number linking each seamless square and rectangular steel tube to its original billet and test results
- Complete customs documentation including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Seamless square and rectangular steel tube bundled with steel strips and edge protectors, preserving plain ends and surface treatment during ocean transit
- Galvanized tubes receive additional plastic wrapping to prevent zinc coating abrasion from contact with adjacent bundles
- Container loading optimized by length (6 m or 12 m) and cross-section to maximize weight utilization while preventing shifting during 30+ day sea voyages
- Custom cutting to project-specific lengths available, reducing on-site waste and handling for construction frame assembly
- Heat number and steel grade marked on each tube end for site identification and inspection traceability
- FOB, CIF, and DDP shipping terms available; professional loading team prevents the corner damage and bending that cause destination rejection
Getting Your Quotation and Mill Test Certificate
Submit your seamless square and rectangular steel tube requirements — steel grade, dimensions, wall thickness, quantity, and destination port — and receive a detailed quotation with unit pricing, production lead time, and shipping terms within 12 hours. We provide sample sections and mill test certificates for quality confirmation before contract signing, and arrange third-party inspection for projects requiring independent verification.
Start Your Seamless Steel Tube Procurement
Send your specifications to admin@sdxjypipe.com or reach us via WhatsApp at +86 188 5315 7756 for quotation and mill test certificate review.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
www.sdxjypipe.com
