Description
Factory-Direct ERW Square Tubes — Produced on three dedicated lines covering 2,800+ specifications with wall thickness up to 40 mm, shipped to EPC contractors across 50+ countries without intermediary markups.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345/S235JR/S275JR/S355JR Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube (ERW) |
| Steel Grade | Q195, Q235, Q345, S235JR, S275JR, S355JR |
| Standard | ASTM |
| Section Shape | Square |
| Wall Thickness | 0.9 mm (full range up to 40 mm available) |
| Length | 6 m / 6.4 m / 12 m |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Fluid Pipe, Boiler Pipe, Drill Pipe, Hydraulic Pipe, Gas Pipe, Oil Pipe, Chemical Fertilizer Pipe, Structure Pipe |
| MOQ | 1 Ton |
| Origin | China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Steel structure frames for industrial plants and warehouses |
| Construction Companies | Building columns, beam-to-column connections, scaffolding supports |
| Machinery Manufacturers | Conveyor frames, equipment bases, hydraulic cylinder housings |
| Infrastructure Developers | Bridge railings, sound barrier posts, utility pole foundations |
| Petrochemical Projects | Gas distribution lines, chemical fertilizer plant piping |
What Negative Tolerance Really Costs on a Structural Frame Order
A 1.5 mm wall-thickness deviation on a 6-meter column can void an entire batch at third-party inspection.
Global buyers sourcing Carbon Steel ERW Welded Square Steel Tube often discover specification gaps only after the container arrives at port. Mill certificates from the original producer may pass factory gates, but independent复检 at destination reveals inconsistencies — wall thickness running thin on inner tubes, weld seams lacking full penetration, or surface defects hidden under mill scale. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed welded hollow sections] When the structural engineer rejects the material, the project faces re-procurement delays, demurrage charges, and potential redesign costs that dwarf the original unit price savings.
Matching ERW Square Tubes to Structural and Fluid Applications
Carbon Steel ERW Welded Square Steel Tube in Q235 through S355JR grades serves dual roles in modern engineering projects. For structural frames, the flat surfaces and sharp 90-degree corners provide direct bearing contact with gusset plates and connection brackets, reducing the need for custom-fitted node connectors. In fluid and gas conveyance, the ERW weld seam — when properly controlled through in-process ultrasonic testing — delivers pressure integrity suitable for low-to-medium pressure hydraulic and pneumatic systems. Our dedicated production lines maintain ±1% dimensional tolerance across 2,800+ specifications, ensuring that 12-meter columns arrive with consistent cross-section geometry for predictable load distribution.
Engineering Compliance and Certification Requirements
Structural applications demand compliance with recognized standards: EN 10219 for cold-formed welded structural hollow sections in European markets, ASTM A500 for North American construction, and JIS G3466 for Southeast Asian projects. [NEED_CITE: steel grade equivalence mapping between EN 10219 and ASTM A500 standards] The hot-rolled surface finish on these ERW square tubes provides adequate corrosion resistance for indoor structural use, while outdoor or marine environments require galvanizing or 3PE coating applied as secondary processing. Certification traceability becomes critical at customs — CE marking under EN 10210/10219 is mandatory for EU construction projects, while SONCAP certification governs Nigerian imports and SASO applies to Saudi Arabia. Our in-house physical and chemical laboratory conducts incoming material verification, in-process weld inspection, and final dimensional checks before issuing mill test certificates.
Steel Grade Selection and ERW Welding Process
The Q-series (Q195–Q345) follows Chinese GB standards, while S-series (S235JR–S355JR) aligns with European EN specifications — both systems designate minimum yield strength in MPa. For structural frames requiring higher load-bearing capacity, S355JR or Q345 provides greater resistance to bending moments compared to S235JR or Q235. The ERW (Electric Resistance Welded) process forms the tube by rolling hot-rolled steel coil into square profile and welding the seam through electrical resistance heating — this method offers cost efficiency over seamless production while maintaining dimensional accuracy suitable for most structural and low-pressure fluid applications. [NEED_CITE: comparison of ERW versus seamless versus SSAW welding processes for structural applications] Wall thickness tolerance of ±1% means that a specified 5 mm wall may measure between 4.95 mm and 5.05 mm; buyers invoicing on theoretical weight should confirm whether negative tolerance is acceptable for their engineering calculations.
Hidden Costs of Procuring Without Verified Certification
Purchasing Carbon Steel ERW Welded Square Steel Tube without independent material verification exposes projects to multiple failure modes. Steel grade substitution — receiving Q235 when S355JR was specified — compromises structural safety margins and may trigger rejection during building authority inspection. Missing or incomplete mill test certificates cause customs holds, particularly for EU markets requiring CE documentation under EN 10219. [NEED_CITE: consequences of missing CE certification for structural steel imports into European Union] Negative tolerance exceeding contractual limits reduces actual load-bearing capacity, forcing costly reinforcement or complete replacement of installed members. Third-party inspection by SGS or BV before shipment eliminates these risks by providing independent verification of chemical composition, mechanical properties, and dimensional compliance.
Why Engineering Procurement Teams Source From Our Facility
Factory-direct pricing eliminates intermediary markups that typically add 8–12% to landed costs on international steel orders. Our three dedicated production lines cover 2,800+ specifications including non-standard dimensions and custom lengths, reducing the need to source square tubes, plates, and sections from multiple suppliers. The proprietary sharp-corner rectangular tube technology — holding 41 invention patents — fills gaps in global supply for architectural applications requiring precise 90-degree internal corners. Every shipment undergoes inspection in our in-house physical and chemical laboratory, with original mill test certificates documenting heat number traceability from slab to finished tube. We hold Lloyd’s Register EU CE certification under EN 10210/10219, ISO 9001:2015 quality management, and Singapore FPC approval — certifications that prevent customs delays across 50+ export destinations. Professional loading optimization ensures that 6-meter and 12-meter lengths maximize container utilization, reducing per-ton freight costs on FOB, CIF, and DDP shipments.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345/S355JR chemical composition and mechanical properties per ASTM standards, with heat number traceability
- CE certificate under EN 10210/10219 for structural hollow sections, required for European Union construction projects
- ISO 9001:2015 quality management system certificate covering production processes and inspection procedures
- SGS or BV third-party inspection report verifying dimensional tolerance, weld seam quality, and surface finish before shipment
- Material traceability documentation linking each bundle to specific heat numbers and production batch records
- Customs clearance package including packing list, bill of lading, and certificate of origin formatted for destination port requirements
Packaging, Loading & Delivery
- Hot rolled ERW square tubes bundled with steel strips at intervals preventing bundle separation during ocean transit, with edge protectors preserving corner geometry
- Plain-end tubes with non-oiled surface require moisture barriers in container to prevent surface rust during humid climate shipping
- 6-meter and 12-meter lengths loaded with optimized container plans maximizing 20ft and 40ft high-cube utilization for Q235 and S355JR grades
- Custom cutting to project-specific lengths available before shipment, reducing on-site waste and secondary processing costs for construction applications
- Heat number and steel grade stenciled on each tube end for site identification and traceability verification during installation
- FOB, CIF, and DDP shipping terms available with professional loading supervision and real-time container tracking to 50+ countries
Securing Quotations and Material Verification for Your Project
Submit your specification requirements including steel grade (Q235, Q345, S355JR), section dimensions, wall thickness, quantity, and destination port to receive detailed pricing within 12 hours. Request original mill test certificates and optional SGS/BV third-party inspection reports before confirming orders. Our technical team provides non-standard dimension quotations and custom processing options including cutting, punching, and bending for your structural or fluid conveyance applications.
Frequently Asked Questions
Q: What is the difference between Q345 and S355JR steel grades for structural applications?
A: Both Q345 and S355JR designate similar minimum yield strength levels in Chinese GB and European EN standards respectively. They are generally interchangeable for structural frame applications, though chemical composition ranges differ slightly. We provide grade equivalence documentation and mill test certificates showing actual test results for your specific heat number.
Q: Can you provide third-party inspection before shipment for Carbon Steel ERW Welded Square Steel Tube orders?
A: Yes, we arrange SGS or BV third-party inspection covering dimensional verification, visual weld seam examination, and review of mill test certificates. The inspection occurs at our facility after production completion but before container loading, with full report provided to you for approval prior to shipment.
Q: What is the minimum order quantity for custom non-standard dimensions?
A: Our MOQ is 1 Ton for standard specifications. Non-standard dimensions outside our 2,800+ specification range require consultation regarding production feasibility and minimum tonnage based on section size and wall thickness requirements.
Q: Do you provide CE certification for European Union construction projects?
A: Yes, we hold Lloyd’s Register EU CE certification under EN 10210/10219 for welded structural hollow sections. CE documentation is included with shipment for EU destinations, covering factory production control and product compliance with European construction product regulations.
Q: How do you handle negative tolerance on wall thickness for theoretical weight invoicing?
A: Our production maintains ±1% dimensional tolerance per specification. For orders invoiced on theoretical weight, we confirm acceptable tolerance range before production. Actual weight invoicing is available upon request, with weighbridge tickets provided at loading.
Secure Your Carbon Steel ERW Welded Square Steel Tube Supply with Verified Certification
Submit your project specifications including steel grade, dimensions, quantity, and destination to receive factory-direct pricing and mill test certificate samples within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxjysteel.com
Email: admin@sdxjysteel.com
Mobile/WhatsApp/WeChat: +86 188 5315 7756
