Description
Factory-Direct Carbon Steel Tubes — 2,800+ specifications in stock with wall thickness up to 20mm, shipped with full EN10219 and ASTM A500 mill test certificates.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Carbon Steel Square and Rectangular Pipe |
| Product Type | Square / Rectangular Steel Tube (Welded) |
| Steel Grade | Q195, Q215, Q235, Q345, #20, #45 |
| Standard | EN10219, EN10210, GB/T 6728, JIS G3466, ASTM A500, ASTM A36 |
| Section Shape | Square / Rectangular |
| Size Range | Square pipe 20×20mm–500×500mm; Rectangular pipe 20×40mm–300×500mm |
| Wall Thickness | 1.2mm–20mm |
| Length | 3m–12m (random or customized) |
| Technique | Hot Rolled / Welded |
| Surface Treatment | Pre-galvanized (40–80g/m²), Hot dipped galvanized (200–600g/m²), or per customer requirement |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Construction / Building materials, Steel structures, Solar structure components, Fence posts, Greenhouse frames, Machinery manufacturing, Glass curtain walls |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Structural frames for warehouses, commercial buildings, and multi-story residential projects |
| Steel Structure Fabrication | Column and beam assemblies, truss systems, mezzanine platforms |
| Solar Energy | Mounting structures for ground-mounted and rooftop photovoltaic systems |
| Agricultural Infrastructure | Greenhouse skeleton frames, livestock fencing posts, irrigation support structures |
| Machinery Manufacturing | Conveyor frames, equipment bases, protective guard structures |
| Architectural Facades | Glass curtain wall sub-frames, decorative building envelopes |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on 10mm wall means the difference between passing structural inspection and failing load calculations.
When procurement teams order carbon steel square and rectangular pipes for load-bearing frames, the wall thickness variance directly impacts moment of inertia and buckling resistance. I’ve seen projects where tubes arrived with actual wall 0.8mm below nominal — on a 500×500×20mm column, that’s 15% less steel than specified. The structural engineer recalculates, the fabricator stops cutting, and suddenly you’re paying air freight for replacement material from China while the site sits idle. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
The other hidden cost is certification rejection. EU customs and third-party inspectors measure wall thickness at multiple points. If your mill test certificate says 10mm but the caliper reads 9.1mm, the entire container gets held at port. I’ve watched clients lose three weeks of project timeline because their supplier couldn’t guarantee consistent wall thickness across 2,800+ specifications.
Matching Carbon Steel Square and Rectangular Pipe to Structural Load Requirements
For building frames and solar mounting structures, Q235 and Q345 grades provide the yield strength needed to resist wind loads and snow accumulation without excessive deflection. The 20×20mm to 500×500mm size range covers everything from purlin supports to main columns, while the 1.2mm–20mm wall thickness allows engineers to optimize weight-to-strength ratios. When these tubes are hot-dip galvanized with 200–600g/m² zinc coating, they withstand coastal and industrial environments where corrosion would compromise structural integrity within five years.
Engineering Compliance and Certification for Global Projects
Structural hollow sections must meet EN 10219 for European projects and ASTM A500 for North American applications. The carbon steel square and rectangular pipe we supply carries CE marking under EN10210 and EN10219, with mill test certificates documenting chemical composition and mechanical properties per heat number. [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500 standards] For projects requiring third-party verification, we arrange SGS or BV inspection before shipment, ensuring the material matches the structural calculations submitted to local authorities.
Steel Grade Selection and Welding Process Fundamentals
Q235 corresponds to S235JR in the EN system and offers 235 MPa minimum yield strength — suitable for non-critical structural members and light-duty frames. Q345 (equivalent to S355JR/S355J2) provides higher strength for main load-bearing columns and beams, reducing cross-section size while maintaining structural performance. The welded manufacturing process uses high-frequency electric resistance welding, creating a continuous longitudinal seam with mechanical properties matching the base metal. Pre-galvanized tubes with 40–80g/m² zinc coating work for indoor applications, while hot-dip galvanized with 200–600g/m² provides corrosion protection for outdoor exposure, burial, or marine environments.
The Hidden Cost of Material Non-Conformance
Ordering carbon steel square and rectangular pipe based on price alone often leads to three failure modes: wall thickness below tolerance, steel grade misidentification, and missing or falsified mill test certificates. When a 355 MPa yield strength tube arrives with actual 280 MPa, the structural frame passes visual inspection but fails under load testing — requiring complete disassembly and replacement. [NEED_CITE: consequences of non-compliant structural steel in construction projects] EU customs rejects shipments without valid CE certificates under EN10219, stranding containers at port for weeks while documentation is corrected. The fabricator who cuts tubes without verifying heat numbers risks mixing grades, creating weld joints with mismatched carbon equivalents that crack under stress.
Why Procurement Teams Choose Our Factory
We operate three production lines covering 2,800+ specifications, allowing you to source all tube sizes from one factory rather than coordinating multiple suppliers. Our in-house physical and chemical laboratory tests every heat for dimensional accuracy, tensile strength, and chemical composition before issuing mill test certificates. The 41 invention patents include China’s first sharp-corner rectangular tube technology, providing superior corner quality for architectural applications where rounded corners create aesthetic and structural problems. We hold full international certifications — ISO 9001:2015, Lloyd’s CE under EN10210/EN10219, Singapore FPC, and SGS/BV verification — ensuring your carbon steel square and rectangular pipe clears customs in 50+ countries. Custom non-standard sizes and定尺切割 are available with low MOQ, and our loading team uses specialized techniques to prevent tube deformation during container transit.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345 chemical composition and yield strength per EN10219 and ASTM A500
- CE certificate confirming compliance with EN10210 and EN10219 for European market access
- ISO 9001:2015 quality management system certificate covering production and testing processes
- SGS or BV third-party inspection report verifying dimensional tolerance and surface treatment thickness
- Material traceability by heat number linking each tube to specific chemical and mechanical test results
- Complete customs documentation including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Carbon steel square and rectangular pipe bundled with steel strips and edge protectors to preserve galvanized coating during ocean transit
- Hot-dip galvanized tubes wrapped with waterproof paper and plastic film to prevent white rust formation during storage and shipping
- Container loading optimized for 3m–12m lengths with wooden chocks and steel wire lashing to prevent shifting and surface damage
- Custom cutting services available for specific project lengths, with cut ends deburred and marked with heat number and steel grade
- Professional container loading team ensures maximum weight utilization while maintaining tube integrity for 20×20mm–500×500mm sizes
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination to final destination
Requesting Quotation and Technical Documentation
Submit your specifications including size, wall thickness, steel grade, surface treatment, quantity, and destination port to receive a detailed quotation with unit price, lead time, and shipping terms. We provide mill test certificates and third-party inspection reports for review before contract signing, ensuring the carbon steel square and rectangular pipe meets your project requirements. For non-standard dimensions or custom lengths, our technical team reviews drawings and provides fabrication solutions within 12 hours.
Frequently Asked Questions
Q: How do Q235 and Q345 steel grades correspond to EN and ASTM standards?
A: Q235 is equivalent to S235JR in EN10219 and ASTM A53 Grade A, while Q345 corresponds to S355JR/S355J2 in EN10219 and ASTM A500 Grade B/C. We provide mill test certificates documenting the chemical composition and mechanical properties to confirm grade equivalence for your project specifications.
Q: Can you provide mill test certificates and arrange third-party inspection?
A: Yes, we issue EN 10204 3.1 mill test certificates for every shipment, documenting chemical composition and mechanical properties by heat number. Third-party inspection by SGS or BV can be arranged before delivery to verify dimensional tolerance, surface treatment thickness, and material conformity.
Q: Do you accept non-standard dimensions and what is the minimum order quantity?
A: We produce custom non-standard sizes beyond the 20×20mm–500×500mm range with wall thickness up to 20mm. The minimum order quantity is 1 ton, and custom sizes typically require 15–25 days production time depending on specifications.
Q: What is the difference between pre-galvanized and hot-dip galvanized surface treatment?
A: Pre-galvanized tubes have 40–80g/m² zinc coating applied before forming, suitable for indoor applications. Hot-dip galvanized tubes have 200–600g/m² zinc coating applied after forming, providing superior corrosion resistance for outdoor, buried, or marine environments.
Q: How do you pack square and rectangular pipes for container shipment to prevent damage?
A: Tubes are bundled with steel strips and edge protectors, with hot-dip galvanized surfaces wrapped in waterproof paper. Our loading team uses wooden chocks and steel wire lashing to secure bundles in containers, preventing shifting and surface damage during ocean transit.
Get Your Carbon Steel Square and Rectangular Pipe Quote Today
Send your specifications to admin@sdxjypipe.com or contact us via WhatsApp at +86 188 5315 7756 to receive pricing, mill test certificates, and delivery schedules within 12 hours.
