Description
Factory-direct pricing, no middlemen — Every Q235 Q345 Carbon Steel Square Tube 15-800mm Wall 1-50mm Factory Direct rolls off our own ERW and seamless lines, shipped with original mill test certificates and CE marking for EU project compliance.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Carbon Steel Square Steel Tube |
| Product Type | Square Steel Tube / Hollow Section |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400, ASTM A53, ASTM A106, S235JR, S275JR, S355J2 |
| Standard | ASTM A53, ASTM A106, API 5L, EN Standard, GB Standard, JIS |
| Section Shape | Square / Rectangular |
| Size Range | 15mm × 15mm – 800mm × 800mm |
| Wall Thickness | 1mm – 50mm (or Customized) |
| Length | 6000mm / 12000mm (or Customized) |
| Technique | ERW / Hot Rolled / Cold Rolled / Seamless (SMLS) / LSAW / SSAW |
| Surface Treatment | Black Painted / Varnished / Galvanized (Hot-Dip / Electro) / 3LPE / 3LPP Coated / Oiled |
| Tolerance | ±1% |
| Ends | Plain / Beveled (as required) |
| Processing Service | Welding / Punching / Cutting / Bending / Decoiling |
| Application | Construction / Oil & Gas / Automotive / Machinery / Shipbuilding / Fluid, Gas, Oil transport |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors & Construction | Structural frameworks for high-rise buildings, scaffolding systems, bridge support columns |
| Machinery Manufacturers | Hydraulic cylinder barrels, pneumatic system housings, conveyor frame fabrication |
| Oil & Gas | Pipeline transmission lines, drilling platform support structures, fluid transport conduits |
| Shipbuilding | Marine piping networks, offshore platform structural members, deck support frames |
| Automotive | Chassis structural components, exhaust system frames, roll cage fabrication |
What Negative Tolerance Costs When Your Square Hollow Section Fails Site Inspection
A wall thickness deviation beyond ±1% turns a compliant shipment into a port rejection.
Global buyers routinely face material arriving with actual wall thickness below the specified minimum — the third-party inspector measures, the numbers don’t match the purchase order, and the entire container sits at the destination port. For structural frames carrying design loads calculated on nominal dimensions, this gap between theoretical weight and actual承载 capacity creates liability that no amount of price discount can offset. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
How Full-Range Dimensions Match Structural Frame Requirements
Our Carbon Steel Square Tube Supplier covers side lengths from 15mm × 15mm up to 800mm × 800mm with wall thickness spanning 1mm to 50mm, allowing EPC contractors to source both small-bore hydraulic lines and large-section structural columns from a single production facility. The ±1% tolerance range holds across ERW, seamless, and LSAW manufacturing routes, meaning a project specifying Q345B for main load-bearing frames and Q235B for secondary bracing receives consistent dimensional accuracy regardless of steel grade selection.
Engineering Compliance and Certification Pathways
Structural hollow sections destined for European projects must carry CE marking conforming to EN 10210 (hot-finished) or EN 10219 (cold-formed) — without this documentation, customs clearance fails regardless of material quality. [NEED_CITE: CE marking requirements for structural steel hollow sections under EU Construction Products Regulation] North American projects typically require ASTM A53 or A500 compliance with mill test certificates showing chemical composition and mechanical properties traceable to heat numbers. Our in-house physical and chemical laboratory tests every production batch before shipment, generating original MTC documentation that satisfies both EU notified body requirements and third-party inspectors like SGS or BV.
Steel Grade Selection and Manufacturing Process Fundamentals
The Q-series (Q195, Q235, Q345) follows Chinese GB standards where the number indicates minimum yield strength in MPa — Q345B delivers higher load-bearing capacity than Q235B for the same cross-section, allowing designers to reduce wall thickness and structural weight. European S-series grades (S235JR, S275JR, S355J2) and American ASTM A53/A106 serve equivalent functions in their respective regulatory frameworks, with grade selection driven by project specification requirements rather than material availability. ERW (Electric Resistance Welded) tubes suit structural applications where cost efficiency matters, while seamless (SMLS) pipes serve high-pressure oil & gas transmission where weld integrity becomes critical. Hot-dip galvanizing provides sacrificial zinc coating for outdoor or marine environments, whereas black painted or oiled finishes work for indoor structural frames where corrosion exposure remains limited.
Hidden Costs of Sourcing Without Verified Mill Test Certificates
Material arriving without proper MTC documentation forces buyers into reactive mode — either paying for retroactive third-party testing at destination ports or accepting unverified material into structural assemblies. [NEED_CITE: consequences of missing mill test certificates in international steel procurement] Steel grade misidentification between Q235 and Q345 creates load-bearing discrepancies that structural engineers cannot approve, triggering redesign costs and project delays that dwarf any initial price savings from unverified suppliers. Certification gaps compound when customs authorities hold shipments lacking CE documentation for EU-bound cargo or proper certificates of origin for preferential tariff claims.
Why Project Procurement Teams Source Carbon Steel Square Tube Supplier From Our Facility
Our three dedicated production lines cover over 2,800 specifications in square and rectangular hollow sections, eliminating the fragmented sourcing that forces buyers to coordinate multiple vendors for different size ranges and steel grades. The proprietary sharp-corner rectangular tube technology — backed by 41 invention patents — fills dimensional gaps that standard rolling mills cannot achieve, allowing architects to specify tight-radius corners for aesthetic and structural connection requirements. Every shipment includes original mill test certificates generated from our in-house laboratory, with chemical composition and mechanical properties traceable to specific heat numbers for full material accountability. We hold CE certification under EN 10210/10219, ISO 9001:2015, and Singapore FPC, with SGS and BV third-party inspection available upon request for projects requiring independent verification. Custom non-standard sizes and wall thicknesses beyond catalog offerings accommodate specialized engineering requirements without the extended lead times typical of mills focused on high-volume standard production.
Documentation & Compliance
- Mill test certificate documenting Q235B/Q345B chemical composition and mechanical properties per GB standards, traceable to heat number
- CE certificate confirming EN 10210/EN 10219 compliance for structural hollow sections destined for European Union projects
- ISO 9001:2015 quality management system certificate covering production processes and inspection protocols
- SGS or BV third-party inspection report available for pre-shipment verification of dimensions, surface treatment, and material properties
- Material traceability documentation linking each tube to specific heat numbers and production batch records
- Complete customs documentation package including packing list, bill of lading, and certificate of origin for tariff preference claims
Packaging, Loading & Delivery
- Q235 and Q345 square tubes bundled with steel strips and edge protectors to preserve surface treatment during ocean transit
- Hot-dip galvanized tubes wrapped with waterproof paper and plastic film to prevent zinc coating damage from moisture exposure
- 6000mm and 12000mm lengths loaded with optimized container stowage plans maximizing payload while maintaining weight distribution
- Custom cut-to-length services available for 15mm × 15mm through 800mm × 800mm sections, reducing on-site waste and handling
- Heat number and steel grade stenciled on each tube bundle for site identification and material traceability verification
- FOB, CIF, and DDP shipping terms with professional loading supervision and real-time tracking for 50+ country destinations
Submit Specifications for Quotation and Material Verification
Project procurement teams should provide target dimensions (side length, wall thickness, length), steel grade requirements, quantity, and destination port to receive detailed pricing with delivery timelines and applicable certification documentation. Our team responds within 12 hours with Proforma Invoice including payment terms, production schedule, and mill test certificate confirmation. Non-standard specifications and custom wall thickness requests receive technical review for feasibility and lead time assessment.
Request Your Carbon Steel Square Tube Quote With Mill Test Certificate
Send your specifications via email to admin@sdxjysteel.com or contact us at +86 188 5315 7756 (WhatsApp/WeChat available) to receive pricing, certification documentation, and delivery confirmation for your project requirements.
Frequently Asked Questions
Q: How do Q235/Q345 Chinese grades compare to S235JR/S355J2 European and ASTM A53 American standards?
A: The Q-series follows GB standards where the number indicates minimum yield strength in MPa, while S-series follows EN standards and ASTM follows US specifications. Material equivalence depends on chemical composition and mechanical property requirements — we provide grade comparison documentation and can supply mill test certificates showing compliance with your specified standard.
Q: Can you provide Mill Test Certificates and arrange third-party inspection by SGS or BV?
A: Yes, every production batch undergoes testing in our in-house physical and chemical laboratory, generating original mill test certificates documenting chemical composition and mechanical properties. Third-party inspection by SGS or BV is available upon request for pre-shipment verification of dimensions, surface treatment quality, and material properties.
Q: What is the minimum order quantity for non-standard sizes and custom wall thickness?
A: We cover over 2,800 specifications with wall thickness up to 50mm and custom non-standard sizes available. MOQ depends on specific dimensions and steel grade requirements — provide your specifications for detailed assessment of production feasibility and minimum quantities.
Q: When should I specify hot-dip galvanized versus black painted or oiled surface treatment?
A: Hot-dip galvanizing provides sacrificial zinc coating suitable for outdoor exposure, marine environments, or corrosive conditions. Black painted or varnished finishes work for indoor structural applications with limited corrosion exposure. Oiled surfaces prevent rust during transit and storage for tubes requiring further processing or painting at destination.
Q: Do your products carry CE marking for European Union project compliance and customs clearance?
A: Yes, our structural hollow sections hold CE certification under EN 10210 (hot-finished) and EN 10219 (cold-formed) standards, with documentation confirming compliance for EU construction projects. We also hold Lloyd’s Register EU CE certification and Singapore FPC for regional project requirements.
