Description
Factory-Direct ERW Hollow Sections — Every Q235 Q345 ERW welded square rectangular steel tube supplier order ships with original mill certificates and full dimensional inspection reports.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345 Welded Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (ERW Hollow Section) |
| Steel Grade | Q195, Q215, Q235, Q345 |
| Standard | ASTM A213, DIN EN 10217-1 |
| Section Shape | Square / Rectangular |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / Slightly Oiled |
| Tolerance | ±1% |
| Length | 6m / 6.4m / 12m (customizable) |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Invoicing | By Theoretical Weight |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, column supports, roof truss systems, scaffolding structures |
| Oil & Gas / Chemical | Fluid transport pipelines, gas distribution lines, chemical fertilizer conveyance |
| Machinery & Equipment | Machine frames, conveyor supports, hydraulic cylinder sleeves, drill pipe casings |
| Industrial Fabrication | Boiler tube assemblies, structural bracing, equipment skids |
What Negative Tolerance Really Costs on a Structural Frame Order
A ±1% tolerance on wall thickness is the difference between passing site inspection and scrapping an entire container.
Global buyers sourcing welded hollow sections repeatedly face material that arrives below specified wall thickness. When a 4.0mm nominal wall measures 3.2mm on arrival, the structural frame fails load verification and the entire shipment becomes dead stock. Missing mill test certificates compound the problem — customs holds the cargo, the project timeline collapses, and the buyer absorbs demurrage plus replacement freight. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching ERW Hollow Sections to Structural and Fluid Applications
Q235 and Q345 grades cover the majority of structural framing and low-to-medium pressure fluid transport requirements across developing markets. The ERW welding process produces a consistent longitudinal seam that handles the bending and punching operations typical in on-site fabrication. For buyers assembling multi-category project orders, sourcing a Q235 Q345 ERW welded square rectangular steel tube supplier with in-house cutting and bending capability eliminates coordination gaps between pipe, plate, and section suppliers.
Engineering Compliance and Certification Requirements
Structural applications across EU markets require EN 10219 compliance for cold-formed welded hollow sections, while North American projects reference ASTM A500 or A213 depending on the application type. The Q345 grade provides higher yield capacity than Q235, making it suitable for load-bearing columns and heavy machinery frames where deflection limits are tight. Surface treatment selection — hot rolled versus oiled — depends on whether the tubes will undergo further galvanizing or will serve in indoor structural roles. Third-party inspection from SGS or BV confirms chemical composition and dimensional accuracy before shipment, preventing customs rejection at destination ports. [NEED_CITE: steel grade equivalence between Chinese GB and international EN/ASTM standards]
Understanding Q-Series Steel Grades and ERW Welding
The Q-series designation follows the Chinese GB/T 700 standard, where the number indicates minimum yield strength in MPa — Q235 yields at 235 MPa while Q345 reaches 345 MPa. This grading system parallels the European S-series (S235JR, S275JR, S355JR) and American A36/A572 framework, though exact chemical composition boundaries differ slightly between standards. ERW welding uses electric resistance to fuse the strip edges without filler metal, producing a clean seam suitable for structural applications and moderate-pressure fluid conveyance. The ±1% dimensional tolerance on these tubes ensures that theoretical weight invoicing aligns closely with actual delivered weight, reducing disputes over material quantity. Hot rolled surface finish provides a mill scale coating that offers short-term corrosion resistance during storage and transit, while slight oiling adds protection for longer ocean freight durations. [NEED_CITE: ERW welding process characteristics for structural hollow sections]
Hidden Costs of Sourcing Without Verified Tolerance
When wall thickness falls below specification due to excessive negative tolerance, the structural member cannot carry its designed load — forcing engineers to either reject the shipment or redesign the entire frame. Certification gaps create a different failure mode: cargo without proper mill test certificates gets held at customs, sometimes for weeks, while the project waits. Material traceability issues mean that if a structural member fails during service, the buyer cannot prove which heat of steel was used, exposing them to liability claims. [NEED_CITE: material traceability requirements for structural steel in construction projects]
Why Buyers Choose Xin Jiyuan for ERW Hollow Sections
Every production run passes through three-stage in-house quality inspection covering dimensional accuracy, weld seam integrity, and surface condition before release. Original mill test certificates accompany each batch, documenting chemical composition and mechanical properties traceable to the specific heat number. The facility maintains ready stock across 2,800+ specifications, enabling split shipments and urgent replenishment without waiting for production slots. For buyers requiring non-standard lengths or custom processing — cutting, punching, bending — the three production lines handle these operations in-house rather than outsourcing to third-party fabricators. Long-term partners receive volume-based pricing reviews every six months, with consolidated container loading available for buyers combining hollow sections with plates, beams, and other steel categories in a single shipment.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345 chemical composition and mechanical properties per GB/T 700, traceable by heat number
- CE certificate confirming compliance with EN 10210/EN 10219 for European market structural applications
- ISO 9001:2015 quality management certificate covering the full production and inspection process
- SGS or BV third-party inspection report available upon request for independent verification of dimensions and material properties
- Full customs documentation package including packing list, bill of lading, and certificate of origin
- Material traceability sheet linking each tube bundle to its production heat number and inspection records
Packaging, Loading & Delivery
- Q235/Q345 ERW tubes bundled with steel strips and edge protectors to maintain ±1% dimensional integrity during ocean transit
- Hot rolled surface tubes shipped with slight oil coating to prevent rust formation during extended container voyages
- 6m and 12m lengths optimized for 20ft and 40ft container loading plans, maximizing payload per shipment
- Custom cutting to project-specific lengths available before shipment, reducing on-site waste and secondary processing
- Each bundle labeled with heat number, steel grade (Q235/Q345), dimensions, and bundle weight for site identification
- FOB, CIF, and DDP shipping terms available with professional export documentation handling
Ready to Verify Tolerance and Certification Before You Order
Submit your specification sheet — including section dimensions, wall thickness, steel grade, length, and destination port — to receive a detailed quotation with mill test certificate samples and dimensional tolerance confirmation. For non-standard sizes or custom processing requirements, the engineering team provides fabrication drawings and lead time estimates within one working day.
Get Your Q235 Q345 ERW Hollow Section Quote with Mill Certificates
Send your specifications via email or WhatsApp to receive pricing, tolerance confirmation, and sample mill test certificates within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxinjiyuan.com
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
Frequently Asked Questions
Q: How does Q235 compare to S235JR or A36 in international projects?
A: Q235 follows the Chinese GB/T 700 standard with minimum yield strength of 235 MPa, chemically and mechanically similar to European S235JR and American A36. For projects requiring EN or ASTM compliance, we provide cross-reference documentation and can arrange third-party verification to confirm equivalence for your market’s structural codes.
Q: Can I verify material authenticity before the shipment leaves China?
A: Yes. Every batch includes original mill test certificates with heat number traceability. We also accommodate SGS or BV third-party inspection at our facility before loading, providing independent verification of chemical composition, dimensions, and wall thickness.
Q: What is the minimum order quantity for custom lengths or processing?
A: Standard MOQ is 5 tons. For custom cutting, punching, or bending to your project drawings, we work from your fabrication schedule and confirm feasibility before production. Trial orders for new specifications are accepted to support sample verification.
Q: How do you handle negative tolerance on wall thickness?
A: Our production maintains ±1% dimensional tolerance on wall thickness and outer dimensions. Each batch undergoes three-stage inspection including ultrasonic wall thickness measurement. We invoice by theoretical weight but guarantee that actual measurements fall within the stated tolerance range.
Q: What surface treatment options are available for these ERW tubes?
A: Standard options include hot rolled finish with mill scale or slight oil coating for corrosion protection during transit. For outdoor or corrosive environments, we can arrange hot-dip galvanizing as a secondary processing step, with full coating thickness documentation provided.
