Description
Factory-Direct ERW Tubes, No Middlemen — Q235 Q355 ERW welded square rectangular steel tube supplier producing 20×20 to 200×200 mm with wall thickness up to 30 mm straight from our own mill.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 / Q355 ERW Welded Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (SHS / RHS) |
| Steel Grade | Q195, Q235, Q355 |
| Standard | ASTM (applicable); GB/T 6728 implied by Q-series grades |
| Section Shape | Square / Rectangular |
| Size Range | 20×20 mm – 200×200 mm |
| Wall Thickness | 1.5 – 30 mm |
| Length | 1 – 12 m (standard 5.8 m / 6 m) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / Galvanized Coating / Black (Non-oiled) |
| Tolerance | ±1% |
| Ends | Plain |
| Processing Service | Welding, Punching, Bending, Cutting, Decoiling |
| Application | Steel structures / Construction frames / Machinery frames / Scaffolding / Furniture / Bridge / Car manufacturing / Electrical installation / Mining |
| MOQ | 25 Tons (one 20ft container) |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors & Construction | Steel structure frames, scaffolding systems, high-rise building columns |
| Machinery Manufacturers | Equipment base frames, conveyor support structures, industrial platforms |
| Infrastructure & Bridge Projects | Load-bearing structural members, bridge railings, support pylons |
| Mining & Industrial | Mining equipment frames, electrical installation conduits, car manufacturing jigs |
Where Wall-Thickness Tolerance Decides Structural Integrity on a Q355 Frame Order
A ±1% tolerance on 30 mm wall Q355 ERW tubes means the difference between passing load calculations and failing site inspection.
When procurement teams source Q235 Q355 ERW welded square rectangular steel tube for structural frames, inconsistent wall thickness creates cascading problems. Thinner-than-specified walls reduce load-bearing capacity below engineering calculations, while thicker walls inflate project costs without adding value. Missing mill test certificates compound the issue — customs authorities in EU markets increasingly demand EN 10219 compliance documentation, and without proper certification, entire shipments face delays or rejection [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements].
How 30 mm Maximum Wall Thickness Expands Structural Applications Beyond Typical ERW Offerings
Most ERW welded square and rectangular tubes on the market max out at 16 mm or 20 mm wall thickness, forcing engineers to switch to seamless pipes for heavier structural applications. Our Q235 Q355 ERW welded square rectangular steel tube range extends to 30 mm wall thickness, covering 20×20 mm to 200×200 mm sections. This means EPC contractors sourcing steel structure frames for industrial buildings can specify welded tubes throughout their project without splitting orders between welded and seamless suppliers. The Q355 grade provides higher yield strength than Q235, making it suitable for bridge components and heavy machinery frames where load-bearing capacity matters.
Engineering Compliance: EN 10219, ASTM A500, and Project-Specific Certification Requirements
Structural steel procurement for international projects requires matching tube specifications to regional engineering codes. EU construction projects typically specify EN 10219 cold-formed welded structural hollow sections, while North American projects reference ASTM A500 Grade B or C. Our Q235 Q355 ERW welded square rectangular steel tube production meets both standard frameworks, with chemical composition and mechanical properties verified through our in-house physical and chemical laboratory. For projects requiring third-party verification, we arrange SGS or BV inspection before shipment. The CE certification under EN 10210/10219 ensures smooth customs clearance for European destinations, while ISO 9001:2015 quality management covers the entire production process [NEED_CITE: steel grade equivalence between EN 10210 and ASTM A500 standards].
Steel Grade Selection: Q235 vs Q355 and Their Engineering Implications
The Q-series steel grades follow Chinese GB standards, with Q235 offering minimum 235 MPa yield strength and Q355 providing 355 MPa yield strength. For general construction frames, scaffolding, and furniture applications, Q235 delivers adequate performance at lower cost. When projects demand higher load-bearing capacity — bridge structures, heavy equipment frames, or high-rise building columns — Q355 becomes the specification of choice. The ERW welding process creates a longitudinal weld seam through electric resistance heating, producing tubes with consistent mechanical properties along the length. Surface treatment selection depends on the installation environment: hot rolled black finish works for indoor applications or projects requiring field painting, while galvanized coating provides corrosion resistance for outdoor exposure or humid conditions. The ±1% dimensional tolerance ensures predictable fit-up during fabrication, reducing on-site adjustment time.
Hidden Costs of Sourcing Tubes Without Verified Mill Test Certificates
Procurement decisions based solely on unit price ignore the total cost of ownership. Tubes with actual wall thickness below specification trigger engineering re-calculations, potential redesign costs, and project delays. Missing or forged mill test certificates lead to customs holds, third-party inspection fees, and in worst cases, complete shipment rejection. When a Southeast Asian infrastructure project received Q355 tubes without proper chemical composition documentation, the entire batch required re-testing at the destination port, adding weeks to the construction timeline and thousands in testing fees [NEED_CITE: importance of material traceability by heat number in structural steel procurement].
Why Project Teams Choose Our Mill for Q235 Q355 ERW Welded Square Rectangular Steel Tube
Our factory operates three dedicated production lines covering 2,800+ specifications, including the 20×20 to 200×200 mm range with wall thickness up to 30 mm. Every batch undergoes incoming, in-process, and final inspection in our physical and chemical laboratory, with mill test certificates documenting chemical composition and mechanical properties per heat number. We hold 41 invention patents including proprietary sharp-corner rectangular tube technology that eliminates radius at corners for better structural connection. International certifications include ISO 9001:2015, Lloyd’s Register EU CE (EN 10210/10219), Singapore FPC, with SGS and BV third-party verification available. Our professional loading team develops container optimization plans for each shipment, ensuring 25-ton MOQ orders fit efficiently into 20ft containers while protecting tube surfaces during ocean transit.
Documentation & Compliance
- Mill test certificate documenting Q235 or Q355 chemical composition and mechanical properties per GB/T 6728, traceable by heat number
- CE certificate under EN 10210/10219 for European market customs clearance and structural compliance
- ISO 9001:2015 quality management certificate covering production process and inspection procedures
- SGS or BV third-party inspection report available upon request for project-specific verification requirements
- Material traceability documentation linking each tube bundle to heat number, production date, and test results
- Customs document package including packing list, bill of lading, and certificate of origin for destination port clearance
Packaging, Loading & Delivery
- Q235 Q355 ERW welded square rectangular steel tube bundled with steel strips and edge protectors to prevent surface damage during handling
- Galvanized coated tubes wrapped with waterproof paper and plastic film to preserve zinc layer during ocean transit
- Container loading plans optimized for 5.8 m and 6 m standard lengths, maximizing weight utilization within 25-ton MOQ for 20ft containers
- Custom cutting service available for non-standard lengths between 1-12 m, with cut ends deburred and protected
- Heat number and steel grade stenciled on each tube bundle for site identification and traceability verification
- FOB, CIF, and DDP shipping terms available with professional logistics coordination to 50+ countries
How to Request Quotation and Technical Documentation for Your Project
Submit your Q235 Q355 ERW welded square rectangular steel tube requirements including section size, wall thickness, length, quantity, steel grade, and destination port. We respond within 12 hours with detailed quotation covering unit price, total cost, production lead time, payment terms, and applicable certifications. For non-standard sizes outside 20×20 to 200×200 mm range or wall thickness beyond 30 mm, we provide custom manufacturing solutions based on your engineering drawings.
Get Your Q235 Q355 ERW Welded Square Rectangular Steel Tube Quote with Mill Test Certificate
Send specifications to admin@sdxjysteel.com or contact via WhatsApp at +86 188 5315 7756 for pricing and technical documentation.
Frequently Asked Questions
Q: Can you produce Q235 Q355 ERW welded square rectangular steel tube in sizes outside 20×20 to 200×200 mm range?
A: Yes, our factory covers 2,800+ specifications beyond the standard range listed. For non-standard sizes or special dimensions, submit your engineering drawings and we provide custom manufacturing solutions with MOQ depending on specification complexity.
Q: What mill test certificate documentation do you provide with each shipment?
A: Every batch includes mill test certificate documenting chemical composition (C, Si, Mn, P, S content) and mechanical properties (yield strength, tensile strength, elongation) per heat number. Certificates follow GB/T 6728 standards for Q235 and Q355 grades, with material traceability from raw material to finished product.
Q: How do you ensure Q355 tubes meet EN 10219 requirements for European projects?
A: Our Q235 Q355 ERW welded square rectangular steel tube production meets EN 10219 cold-formed welded structural hollow section standards. We hold CE certification under EN 10210/10219 issued by Lloyd’s Register, ensuring dimensional tolerance, mechanical properties, and chemical composition comply with European structural steel requirements.
Q: What is the difference between hot rolled black finish and galvanized coating for these tubes?
A: Hot rolled black finish suits indoor applications or projects requiring field painting, offering lower cost. Galvanized coating provides zinc layer protection for outdoor exposure, humid environments, or corrosive conditions, extending service life but at higher unit price. Surface treatment selection depends on your project environment and design specifications.
Q: How do you optimize container loading for 25-ton MOQ orders?
A: Our loading team develops container optimization plans based on tube dimensions and length. For 5.8 m and 6 m standard lengths, we maximize weight utilization within 20ft container capacity while ensuring proper weight distribution. Wooden wedges and steel strapping secure tubes during ocean transit, preventing movement and surface damage.
