Description
Direct Mill Supply with Full Traceability — XJY Structure produces Q235, Q345, S235JR, and S355JR seamless square and rectangular steel tubes in-house, backed by our own steel mill and fabrication workshop, eliminating third-party sourcing gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345/S235JR Seamless Square and Rectangular Steel Tube |
| Product Type | Seamless Square and Rectangular Hollow Section |
| Steel Grade | Q195, Q235, Q345, S235JR, S275JR, S355JR, 10#, 20#, 45#, SS400, Gr.B–Gr.50 |
| Standard | GB, ASTM |
| Section Shape | Square / Rectangular |
| Size Range | Custom per drawing or standard size range |
| Wall Thickness | 0.9 mm and above |
| Length | 6 m / 6.4 m / 12 m |
| Technique | Seamless (Hot Rolled / Cold Drawn) |
| Surface Treatment | Hot Rolled (Black / Non-oiled) |
| Tolerance | ±1% – ±2% |
| Ends | Plain |
| Application | Construction Structure, Fluid Pipe, Boiler Pipe, Drill Pipe, Hydraulic Pipe, Gas Pipe, Oil Pipe, Chemical Fertilizer Pipe, Structure Pipe |
| MOQ | 25 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Structural columns, beam assemblies, building frames, and platform supports for commercial and industrial buildings |
| Industrial & Energy | Hydraulic system piping, oil and gas transmission lines, boiler structures, and chemical plant process piping |
| Machinery & Equipment | Drill pipe, mechanical processing shafts, and heavy-duty equipment support structures |
What Negative Tolerance Really Costs on a Seamless Hollow Section Order
Wall-thickness deviation beyond ±1% triggers rejection at third-party inspection and customs holds.
When overseas buyers source seamless square and rectangular tubes from China, the most frequent complaint is not price — it is dimensional inconsistency. A batch that looks fine on the mill test certificate can arrive at site with wall thickness falling below the lower tolerance limit, causing NDT failure, weld rejection, or outright customs detention. For structural frames carrying design loads per EN 1993 or AISC, even a small wall-thickness shortfall means the entire member must be recalculated or replaced. [NEED_CITE: dimensional tolerance requirements for seamless hollow sections in structural applications]
How Seamless Process Meets Structural Load Requirements
Seamless square and rectangular hollow sections produced by hot rolling or cold drawing carry no longitudinal weld seam, which means uniform wall strength around the entire perimeter — critical for columns and beam members subject to multi-directional loading. The GB ASTM Standard Seamless Square Rectangular Steel Tube Supplier range from XJY Structure covers Q195 through Q345 and S235JR through S355JR, allowing engineers to match yield strength class to design load without switching suppliers. Wall thickness from 0.9 mm upward with ±1%–2% tolerance control ensures that theoretical weight calculations align with actual delivered weight, avoiding budget overruns on tonnage-based contracts.
Engineering Compliance Across GB and ASTM Frameworks
Structural projects in the EU require CE marking under EN 10210 or EN 10219, while North American infrastructure specifies ASTM A500 or A53. The GB ASTM Standard Seamless Square Rectangular Steel Tube Supplier from XJY Structure provides material that conforms to GB and ASTM standards, with full chemical composition and mechanical property documentation per heat number. For projects in Southeast Asia, the Middle East, and Africa, buyers often need dual certification — and our in-house quality system generates WPS, PQR, weld maps, and dimensional inspection reports that satisfy both EN and ASTM audit requirements. [NEED_CITE: steel grade equivalence between EN and ASTM standards]
Steel Grade Selection and Process Fundamentals
The Q-series (Q195, Q235, Q345) follows the Chinese GB system where the number indicates minimum yield strength in MPa. The S-series (S235JR, S275JR, S355JR) follows the European EN system with similar yield strength designation but different impact testing requirements — JR denotes 27J impact energy at 20°C. ASTM grades such as Gr.B through Gr.50 use ksi-based yield strength. Seamless hot-rolled tubes offer thicker wall capability and better surface finish for structural exposure, while cold-drawn tubes deliver tighter dimensional tolerance for precision machining and hydraulic applications. Surface treatment as hot-rolled black finish suits indoor structural use or projects where painting or galvanizing will be applied on site. [NEED_CITE: seamless vs welded hollow section performance in structural applications]
Hidden Costs of Sourcing Without Mill Traceability
Buying seamless hollow sections from a trader who sources from multiple mills creates a documentation gap — heat numbers on the MTC may not match the actual material, and third-party inspectors will flag the discrepancy. The result is not just a delayed shipment; it is potential structural safety liability if non-conforming material is welded into a load-bearing frame. Projects requiring EN 1090 or AISC certification cannot accept material without full traceability from billet to finished tube. [NEED_CITE: material traceability requirements for EN 1090 structural steel fabrication]
Why Project Teams Source from XJY Structure
XJY Structure operates as the fabrication division of Shandong Xin Jiyuan Special Steel Tube Co., Ltd, meaning the GB ASTM Standard Seamless Square Rectangular Steel Tube Supplier you deal with controls the entire chain — from steelmaking to finished tube to fabricated assembly. Our own mill produces 2,800+ specifications of raw material, so there is no gap between material supplier and fabricator. Every batch carries a mill test certificate with chemical composition and mechanical properties traceable by heat number. We hold ISO 9001 certification and support SGS, BV, or TÜV third-party inspection before shipment. For projects requiring EN 1090 or ASTM compliance, our engineering team reviews shop drawings, optimizes material usage, and prepares complete QC documentation packages including weld maps and coating reports.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345/S235JR/S355JR chemical composition and mechanical properties per GB/ASTM, traceable by heat number
- ISO 9001 quality management certificate covering the full production process from billet to finished seamless tube
- SGS or BV third-party inspection report available upon request, covering dimensional checks, wall-thickness measurement, and surface quality
- Material traceability report linking each tube bundle to its original heat number and mill production record
- Customs documentation package including packing list, bill of lading, and certificate of origin for destination-country clearance
- CE certificate available for EN 10210/EN 10219 compliance on projects requiring European market access
Packaging, Loading & Delivery
- Seamless square and rectangular tubes bundled with steel strips in seaworthy packaging, sized to fit 20ft and 40ft containers for 6 m / 6.4 m / 12 m lengths
- Hot-rolled black finish tubes protected with anti-rust oil or non-oiled per project specification, with edge protectors to prevent surface damage during transit
- Container loading optimized by our logistics team to maximize weight utilization within shipping limits, reducing per-ton freight cost for bulk orders
- Custom cutting available to project-specified lengths beyond standard 6 m / 6.4 m / 12 m, with cut ends deburred and marked
- Each bundle labeled with heat number, steel grade, size, and length for easy site identification and traceability verification
- FOB, CIF, and DDP terms supported with door-to-door tracking for overseas project sites
Start Your Project Inquiry with Drawings and Specifications
Submit your project drawings in PDF or DWG format along with steel grade, size, wall thickness, quantity, and destination port. Our engineering team responds within 24 hours with a preliminary assessment, detailed quotation covering material, fabrication, coating, packing, and shipping costs, plus a shop drawing timeline and production schedule. For non-standard dimensions or custom fabrication requirements, we provide engineering support for material optimization and fabrication sequencing.
Request Your Quotation and Mill Test Certificate
Send your specifications and drawings to receive a detailed quote with full material documentation.
Mobile/WhatsApp/WeChat: +86 188 5315 7756 | Email: admin@xjystructure.com
