Description
Factory Direct Pricing — Seamless square and rectangular tubes produced from our own billet through to finished hollow sections, eliminating third-party material sourcing.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q195-Q345 Seamless Square Steel Tube |
| Product Type | Seamless Square / Rectangular Steel Tube (Hollow Section) |
| Steel Grade | Q195, Q235, Q345, 10#, 20#, 45#, S235JR, S275JR, S355JR, SS400, Gr.B, Gr.50 |
| Standard | ASTM, API, CE, ISO 9001 |
| Section Shape | Square / Rectangular |
| Wall Thickness | 0.9 mm (full range available per inquiry) |
| Length | 6 m / 6.4 m / 12 m |
| Technique | Seamless (pierced billet, hot rolled / cold rolled / cold drawn) |
| Surface Treatment | Hot Rolled |
| Tolerance | ±1% |
| Ends | Plain (default) |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| 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 | Building frames, column supports, truss systems, platform structures |
| Industrial Facilities | Hydraulic pipelines, boiler tubes, conveyor frameworks, machine base structures |
| Energy & Petrochemical | Oil and gas transmission lines, chemical fertilizer plant piping, drill pipe assemblies |
| Mechanical Engineering | Equipment frames, crane booms, structural supports for heavy machinery |
What Negative Tolerance Actually Costs on a Seamless Square Tube Order
A ±1% tolerance on wall thickness sounds precise — until a third-party inspector measures 1.5 mm under spec at the weld joint.
Overseas buyers sourcing seamless square steel tubes from China often discover that fabricators purchasing raw material from third-party mills cannot guarantee consistent wall thickness across the full cross-section. When a 12-meter column arrives at a Middle East job site with localized thinning beyond acceptable limits, the entire batch fails dimensional inspection. Rework, replacement, and reshipping costs multiply — and the project schedule slips by weeks. [NEED_CITE: EN 10210 tolerance requirements for hot-finished hollow sections]
How Seamless Construction Meets Structural Load Requirements
Seamless square and rectangular tubes eliminate the longitudinal weld seam found in ERW products, providing uniform strength distribution across all four corners. For structural frames and load-bearing columns, this means predictable performance under compression and bending loads. Our Q345 and S355JR grades deliver higher yield strength for applications requiring reduced section sizes while maintaining load capacity. The ±1% wall thickness tolerance ensures that engineering calculations remain valid across the entire tube length. As a Seamless Square Steel Tube Supplier with vertically integrated production, we control quality from billet piercing through final dimensional inspection.
Engineering Compliance and Certification for Global Projects
Structural hollow sections used in building frames and industrial facilities must comply with regional engineering codes — EN 1993 for European projects, AISC standards for North American construction, and local building authority requirements in Middle East and Southeast Asian markets. CE certification under EN 10210 / EN 10219 is mandatory for EU market entry, while ASTM A500 and A106 specifications govern North American structural and pressure applications. Our mill test certificates document chemical composition and mechanical properties per the specified standard, with heat number traceability from raw billet to finished tube. Third-party inspection by SGS or BV is available for projects requiring independent verification. [NEED_CITE: steel grade equivalence between Q-series, S-series, and ASTM standards]
Steel Grade Selection and Manufacturing Process
The Q-series (Q195, Q235, Q345) follows Chinese GB standards, where the number indicates minimum yield strength in MPa. Q345 offers approximately 50% higher yield strength than Q235, making it suitable for structural applications requiring reduced weight or higher load capacity. The S-series (S235JR, S275JR, S355JR) follows European EN standards and provides equivalent performance with guaranteed impact toughness at specified temperatures. ASTM Gr.B and Gr.50 serve North American markets with similar strength gradations. Our seamless manufacturing process — piercing solid billets followed by hot rolling or cold drawing — produces tubes with no weld seam, uniform grain structure, and consistent mechanical properties around the entire cross-section. Hot-rolled surface treatment provides a mill scale finish suitable for painting or further coating. For applications requiring corrosion resistance, additional surface treatments such as galvanizing or specialized coatings can be applied during processing.
The Hidden Cost of Unverified Material Certification
Purchasing seamless square steel tubes without verified mill test certificates creates risk across the entire supply chain. When material traceability breaks down — because the fabricator sourced steel from an unverified third-party mill — projects face customs delays, failed inspections, and potential structural safety concerns. Engineering consultants specifying S355JR for a load-bearing frame expect documented proof that the delivered material meets EN 10219 requirements. A missing or forged certificate halts construction until replacement material arrives. [NEED_CITE: material traceability requirements in EN 1090 structural steel fabrication]
Why Project Teams Specify Our Seamless Square Steel Tube
Our own steel mill produces 2,800+ specifications of raw material, eliminating the gap between material supplier and fabricator. Every seamless square and rectangular tube we deliver carries a mill test certificate traceable to the original heat number — no third-party sourcing, no certification gaps. Our fabrication workshop provides CNC cutting, drilling, welding, and bending services, allowing project teams to receive finished components ready for assembly. Certified welding procedures (WPS/PQR) and qualified welders ensure that any on-site or in-shop modifications maintain structural integrity. Complete quality documentation packages — including dimensional inspection reports, coating reports, and material certifications — satisfy the most stringent EPC and general contractor requirements. Professional loading and lashing for oversized cargo ensures that 12-meter tubes arrive at the job site without transit damage.
Documentation & Compliance
- Mill test certificate documenting Q345 chemical composition and mechanical properties per GB/T 1591, with heat number traceability from billet to finished tube
- CE certificate confirming compliance with EN 10210 for hot-finished seamless hollow sections, required for European Union market entry
- ISO 9001 quality management system certificate covering the entire production process from raw material procurement through final inspection
- SGS or BV third-party inspection report available for projects requiring independent verification of dimensional accuracy and material properties
- Material traceability documentation linking each tube to its original heat number, chemical analysis, and mechanical test results
- Complete customs documentation including packing list, bill of lading, and certificate of origin for smooth import clearance
Packaging, Loading & Delivery
- Seamless square tubes bundled with steel strips and edge protectors to preserve the hot-rolled surface finish during ocean transit
- 6-meter and 12-meter lengths optimized for 20-foot and 40-foot container loading, maximizing payload while preventing transit damage
- Plain ends capped to prevent debris ingress and protect internal surfaces during storage and transportation
- Heat number and steel grade clearly marked on each tube for on-site identification and traceability verification
- FOB, CIF, and DDP shipping terms available, with professional loading plans for oversized cargo and project-specific delivery schedules
- Non-oiled surface condition suitable for immediate painting or coating upon arrival at the fabrication shop or job site
How to Request a Quotation for Your Project
Submit your project drawings (PDF or DWG format), specifying steel grade, section dimensions, wall thickness, length, quantity, and destination port. Our engineering team reviews your requirements within 24 hours and provides a detailed quotation including material cost, fabrication services, surface treatment, packaging, and shipping. Mill test certificates and third-party inspection options are confirmed at the quotation stage to ensure compliance with your project specifications.
Start Your Seamless Square Steel Tube Order Today
Share your project specifications and receive a detailed quotation with mill test certificate documentation within 24 hours.
Contact: 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 difference between Q345 and S355JR steel grades?
A: Q345 follows Chinese GB/T 1591 standards, while S355JR follows European EN 10025 standards. Both offer similar yield strength levels (approximately 345 MPa minimum), but S355JR includes guaranteed impact toughness at room temperature (27J at 20°C). For European projects requiring CE certification, S355JR is the specified grade. For projects in China, Middle East, or Southeast Asia without EN requirements, Q345 provides equivalent structural performance at competitive pricing.
Q: Can you provide third-party inspection for seamless square tubes?
A: Yes, we arrange third-party inspection by SGS, BV, or other internationally recognized inspection agencies. The inspection covers dimensional accuracy, wall thickness verification, surface quality, and material certification review. Third-party inspection reports are issued before shipment, providing independent verification for your project quality requirements. Inspection costs are quoted separately based on the scope and duration of the inspection.
Q: What is the minimum order quantity for custom sizes?
A: Our standard minimum order quantity is 25 tons for stock sizes and standard specifications. For custom non-standard sizes, special wall thickness, or non-standard lengths, the minimum order quantity depends on the production requirements and may range from 25 to 50 tons. Custom sizes require additional production setup time, and lead times are confirmed at the quotation stage based on the specific requirements.
Q: Do you provide shop drawing and engineering support?
A: Yes, our engineering team provides shop drawing review, material optimization, and fabrication sequencing support. We can prepare detailed shop drawings for your approval before fabrication begins, ensuring that all dimensions, connections, and processing requirements match your project specifications. Our engineering support helps reduce RFI delays and prevents costly rework during fabrication and installation.
Q: How do you ensure material traceability for seamless square tubes?
A: As a vertically integrated manufacturer with our own steel mill, we maintain complete material traceability from raw billet to finished tube. Each seamless square tube carries a heat number that links to the original chemical analysis, mechanical test results, and production records. Our mill test certificates document the full traceability chain, satisfying the most stringent project requirements for material certification and quality documentation.
