Description
I started out loading containers at the warehouse in Wu*e they shipped out. Learned the hard way what bad loading does — once we sent a 20ft container of 25×25 black square tubes to a buyer in Dubai, no proper bracing inside, and when they opened it at Jebel Ali, half the pieces were bent and the black finish was scraped raw. The whole lot got rejected. That experience pushed me from the loading yard into sales, because I realized the product is only as good as how it arrives. Now every square tube and rectangular pipe we ship, I check the loading plan myself.
Factory-Direct Pricing, No Broker Markup — every Q235B and S355 square rectangular steel tube we produce ships straight from our Jinan mill, cutting out trading company margins on orders of any size.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B / Q355 / S235 / S355 Square and Rectangular Steel Tube |
| Product Type | Square and Rectangular Steel Tube (Seamless & ERW Welded Hollow Sections) |
| Steel Grade | Q235, Q235B, Q355, St37, St52, S235JR, S355JR, S355JOH, S355J2H, ASTM A500 Gr.A/B/C/D, STK400, SS400, C250, C350, C460 |
| Standard | ASTM A500, EN 10219, EN 10210, JIS G3466, AS1163, GB/T 6728 |
| Section Shape | Square & Rectangular |
| Size Range | Square 12×12 mm – 800×800 mm; Rectangular 10×20 mm – 800×1000 mm |
| Wall Thickness | 0.5 – 60 mm |
| Length | 1 – 12 m (up to 24 m available) |
| Technique | ERW (Welded); Seamless options available |
| Surface Treatment | Bare, Oiled, Black Painting, Hot Rolled, Galvanized (30–550 g/m²), Color Painting |
| Tolerance | ±1% dimensional; ovality <1%, deflection <1/2000 |
| Ends | Plain End |
| Application | Steel structures, curtain walls, machinery, scaffolding, furniture, greenhouse, fencing |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Architecture | Building frames, glass curtain wall mullions, architectural facade supports, column sections |
| Steel Structure Fabrication | Portal frames, truss members, bracing tubes, base plate connections |
| Machinery Manufacturing | Conveyor structures, crane booms, equipment bases, hydraulic frame components |
| Infrastructure & EPC | Bridge handrails, sound barrier posts, solar panel mounting structures, fencing posts |
| Commercial & Industrial | Scaffolding systems, shelving racking, warehouse mezzanine frames, greenhouse framing |
What Dimensional Tolerance Costs on a Structural Frame Order
A 2 mm deviation on an 800×800 square tube can force on-site rework across an entire elevation.
When procurement teams source a square rectangular steel tube without verifying tolerance claims against EN 10219 or ASTM A500 requirements, the consequences cascade. Curtain wall contractors find mullion connections misaligned, forcing field-cutting and re-welding that delays facade closure by weeks. Steel fabricators discover that out-of-square sections create cumulative angular errors across portal frames, requiring shimming or full member replacement. [NEED_CITE: EN 10219 cold-formed structural hollow section dimensional tolerance requirements] The problem compounds when mixed batches arrive from different mills with inconsistent ovality — sections that should bolt together cleanly end up requiring custom adapter plates.
Matching Section Geometry to Facade and Frame Engineering
A square rectangular steel tube with true sharp-corner geometry eliminates the rounded-corner gaps that plague standard rectangular hollow sections in curtain wall applications. When mullion tubes meet transom connectors at 90-degree angles, sharp-corner profiles sit flush without filler plates or grinding, reducing assembly time on high-rise facade projects. For structural frames carrying vertical and lateral loads, the flat-to-flat dimension consistency across our 2,800+ specifications means engineers can rely on published section properties without derating for corner radius uncertainty.
Structural Compliance and Surface Protection Across Environments
Load-bearing square rectangular steel tube members must satisfy both dimensional standards and material certification requirements dictated by the project’s governing code. For European projects, EN 10219 cold-formed hollow sections require CE marking and factory production control documentation that confirms steel grade, chemical composition, and mechanical testing per heat number. [NEED_CITE: CE marking requirements for structural steel hollow sections under EN 10219] In corrosive environments — coastal construction, industrial plants, agricultural structures — galvanized coating at 30–550 g/m² provides sacrificial protection that bare or oiled finishes cannot match. For interior or painted architectural applications, black painting or hot-rolled mill scale offers a stable base for topcoat systems. Steel grade selection directly affects load capacity: S355JR delivers higher yield strength than S235JR in the same section size, allowing lighter members or longer spans without increasing cross-section dimensions.
Steel Grade Selection and Manufacturing Process Explained
The Q-series (Q235B, Q355) follows Chinese GB standards where the number indicates minimum yield strength in MPa, while the S-series (S235JR, S355JR, S355J2H) follows European EN standards with impact toughness designations — JR for +20°C, J0 for 0°C, J2 for −20°C. ASTM A500 Grades A through D represent a North American specification system with progressively higher strength requirements. These grade systems are not directly interchangeable without cross-referencing chemical composition and mechanical property tables. [NEED_CITE: steel grade equivalence between GB Q-series, EN S-series, and ASTM A500] ERW welded tubes suit most structural and architectural applications at lower cost, while seamless options serve higher-pressure or critical-load scenarios where weld-line integrity is a concern. Surface treatment choice depends on the service environment: hot-dip galvanizing provides decades of corrosion resistance without maintenance, while oiled or bare finishes work for interior applications or projects receiving field-applied coating systems. Wall thickness tolerance at ±1% means that a specified 10 mm wall will measure between 9.9 mm and 10.1 mm — tight enough for structural calculation confidence without the cost premium of precision-machined sections.
Hidden Costs of Specifying the Wrong Grade or Skipping Certification
Ordering Q235B when the structural engineer specified S355JR creates a yield strength shortfall that may not surface until third-party inspection or load testing — at which point the entire batch becomes non-conforming material requiring replacement. Missing CE documentation on an EN 10219 order blocks customs clearance at EU ports, triggering demurrage charges and project delays that dwarf the original material cost. [NEED_CITE: consequences of non-compliant structural steel documentation in European construction projects] Negative tolerance abuse — where actual wall thickness falls below the specified minimum — reduces load capacity while the theoretical weight invoicing still charges for full section mass, creating a double cost penalty: structural underperformance and financial overpayment.
Why Procurement Teams Consolidate Tube Orders With Us
Our mill operates three production lines covering 2,800+ specifications in square and rectangular profiles, meaning a single purchase order can combine 25×25 small sections with 800×800 heavy members without splitting across multiple suppliers. The patented sharp-corner rectangular tube technology — backed by 41 invention patents — fills a gap that standard mills cannot address, delivering right-angle profiles for architectural facades where rounded corners create unacceptable visual and connection gaps. Every shipment includes mill test certificates generated by our in-house physical and chemical laboratory, with third-party inspection via SGS or BV available before container sealing. Full international certification — ISO 9001:2015, Lloyd’s CE per EN 10210/EN 10219, Singapore FPC — ensures customs clearance across 50+ export markets without documentation disputes. Custom non-standard sizes, cutting, and professional container loading with anti-damage bracing address the loading damage pain point that causes rejection at destination ports.
Documentation & Compliance
- Mill test certificate documenting Q235B/S355JR chemical composition and yield strength per GB/T 6728 or EN 10219 for each heat number
- CE certificate per EN 10210/EN 10219 confirming factory production control for structural hollow sections exported to European markets
- ISO 9001:2015 quality management certificate covering the full production process from raw material incoming inspection to finished tube testing
- SGS or BV third-party inspection report with dimensional measurements, visual examination, and witness testing available upon request
- Material traceability documentation linking each tube bundle to its heat number, chemical analysis, and mechanical test results
- Export customs documents including packing list, bill of lading, and certificate of origin formatted for destination-country clearance requirements
Packaging, Loading & Delivery
- Square and rectangular tubes bundled with steel strips and edge protectors, sized to match container internal dimensions for 12 m or custom-cut lengths
- Galvanized square rectangular steel tube surfaces protected with plastic end caps and separation layers to prevent zinc coating abrasion during transit
- Container loading plans optimized by section size — small 25×25 tubes nested within larger 400×400 sections to maximize payload per 20ft or 40ft container
- Custom cutting to project-specific lengths between 1–24 m, with cut ends deburred and marked with heat number and steel grade
- Bundle identification tags showing steel grade (Q235B/S355JR/A500 Gr.B), section dimensions, wall thickness, length, and heat number for site traceability
- FOB, CIF, and DDP shipping terms available with professional tube loading crews who brace sections against container walls to prevent bending during ocean freight
Starting Your Procurement Process
Submit your square rectangular steel tube requirements — section dimensions, wall thickness, steel grade, surface treatment, quantity, and destination port — and receive a detailed quotation within 12 hours including unit pricing, lead time, and shipping terms. Request mill test certificates and third-party inspection arrangements before committing to production, and confirm that your order meets all certification requirements for your destination market.
Request a Quotation With Full Mill Test Documentation
Provide your section specifications and steel grade requirements to receive pricing, certification confirmation, and delivery scheduling.
Mobile/WhatsApp/WeChat: +86 188 5315 7756 | Email: admin@sdxjypipe.com
Frequently Asked Questions
Q: How do Q235B, S235JR, and ASTM A500 Gr.B compare across different standard systems?
A: These grades represent equivalent structural steel specifications from Chinese GB, European EN, and American ASTM systems respectively. Q235B and S235JR share similar yield strength levels, while ASTM A500 Gr.B aligns closely with both. We supply all three grade systems and provide cross-reference documentation to confirm chemical composition and mechanical property equivalence for your project specification.
Q: Can you arrange SGS or BV third-party inspection before shipment?
A: Yes. Third-party inspection through SGS or BV is available for any order. The inspection covers dimensional verification, visual examination, wall thickness measurement, and witness testing. Full inspection reports with photographs are provided before container sealing.
Q: Do you produce non-standard sizes outside the typical range?
A: Yes. Beyond our standard 2,800+ specifications covering 12×12 mm to 800×800 mm square and 10×20 mm to 800×1000 mm rectangular sections, we produce custom non-standard dimensions including extra-large diameters, heavy wall thicknesses up to 60 mm, and non-standard lengths up to 24 m with low minimum order quantities.
Q: What surface treatment options are available and how do I choose?
A: We offer bare, oiled, black painted, hot rolled, galvanized (30–550 g/m² zinc coating), and color painted finishes. Galvanized suits outdoor or corrosive environments requiring long-term protection. Bare or oiled finishes work for interior applications or projects receiving field-applied coatings. Black painting provides a stable base for architectural topcoat systems.
Q: Do your products carry CE marking for European market import?
A: Yes. Our square rectangular steel tube products carry Lloyd’s CE certification per EN 10210 and EN 10219, with factory production control documentation that satisfies EU customs clearance requirements. Singapore FPC certification is also available for projects in regulated Asian markets.
Request Your Square Rectangular Steel Tube Quotation Today
Send your section dimensions, steel grade, surface treatment, and quantity to receive pricing with mill test certificates within 12 hours.
Mobile/WhatsApp/WeChat: +86 188 5315 7756 | Email: admin@sdxjypipe.com
