Description
Direct Mill Supply for Structural Hollow Sections — Every Q235B ERW square and rectangular steel tube ships with original mill test certificates and full heat-number traceability, eliminating grade confusion and customs delays for global buyers.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Carbon Steel Square and Rectangular Steel Tube |
| Product Type | Square / Rectangular Steel Tube (ERW Welded Hollow Section) |
| Steel Grade | Q195, Q215, Q235, Q235B |
| Standard | EN, JIS, ISO 9001, CE, API, BIS, SNI, Saso, PVOC, SONCAP, SABS, SIRM, TISI, KS, Gs, BSI, RoHS |
| Section Shape | Square / Rectangular |
| Size Range | 20×20 mm – 150×150 mm (e.g., 20×20, 40×40, 60×60, 80×80, 100×100, 20×50, 40×100, 100×150) |
| Length | 6–12 m |
| Technique | ERW (Electric Resistance Welded) / Hot Rolled |
| Surface Treatment | Hot Rolled, Non-oiled |
| Tolerance | ±1% / ±10% |
| Ends | Plain Ends |
| Application | Structural Pipe / Construction Building Material / Building Frames / Steel Structures / Scaffolding / Machinery Frames |
| MOQ | 1 Ton |
| Origin | China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames for high-rise structures, column supports, beam bracing systems |
| Steel Fabrication Workshops | Machinery frames, equipment bases, conveyor structures, welding platforms |
| Scaffolding & Formwork | Scaffold tube systems, formwork supports, temporary access structures |
| General Structural Engineering | Load-bearing frames, portal structures, mezzanine floor supports |
What Negative Tolerance Costs on a 100×100 Structural Frame Order
Actual wall thickness below declared tolerance triggers fabrication rework and structural rejection.
When procurement teams order Q235B carbon steel square rectangular tube for load-bearing frames, the gap between theoretical weight invoicing and actual delivered weight becomes a hidden cost center. I have seen entire container loads of 100×100 mm square tubes arrive at Middle East job sites where third-party inspectors rejected the shipment because wall thickness deviations exceeded ±10% — the steel passed visual inspection but failed ultrasonic measurement. The buyer paid for theoretical weight while receiving under-gauge material, forcing them to either accept compromised structural capacity or reorder at double the freight cost. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
How ERW Welded Hollow Sections Match Structural Frame Requirements
The Q235B grade delivers consistent yield behavior across the full 20×20 to 150×150 mm size range, making this Q235B carbon steel square rectangular tube suitable for both light-gauge scaffolding and heavier portal frame construction. The ERW welding process produces a continuous longitudinal seam with uniform strength matching the parent metal, while the hot-rolled non-oiled surface accepts field welding and painting without additional surface preparation. Our cutting service delivers exact lengths from 6–12 m stock, reducing on-site waste and welding joints in frame assemblies.
Engineering Compliance and Grade Selection for Load-Bearing Applications
Structural engineers specifying Q235B must verify equivalence with international standards when projects require EN 10219 or ASTM A500 compliance — the Q-series grades from China align with S235JR in European specifications for general structural use, though chemical composition limits differ slightly. [NEED_CITE: steel grade equivalence between GB Q235B and EN S235JR] For projects in the European Union or regions requiring CE marking, our mill provides EN-compliant test certificates documenting chemical composition and mechanical properties per EN 10219. The ±1% to ±10% tolerance range covers both precision fabrication work and general construction applications, though buyers should specify tighter limits for machined connections.
Understanding Q235B Grade and ERW Welding Process
Q235B belongs to the Chinese GB/T 700 carbon structural steel series, where “Q” denotes yield strength and “235” indicates the minimum yield value of 235 MPa at room temperature. The “B” suffix specifies the quality grade with impact testing requirements at 20°C, distinguishing it from Q235A which omits low-temperature toughness verification. ERW (Electric Resistance Welded) manufacturing heats the strip edges through electrical resistance and fuses them under pressure without filler metal, producing a weld seam with mechanical properties approaching the base material. This process suits square and rectangular profiles from 20×20 mm up to 150×150 mm with consistent corner radii and flat surfaces ideal for bolted or welded connections. Hot-rolled non-oiled surface treatment leaves the natural mill scale intact, providing temporary corrosion resistance during storage and transit while allowing direct welding without surface preparation.
Hidden Costs of Unverified Material Certification
Purchasing Q235B carbon steel square rectangular tube without original mill test certificates exposes buyers to three failure modes: material substitution where lower grades replace specified Q235B, missing heat numbers preventing traceability to production batches, and forged documents that pass visual inspection but fail laboratory verification. [NEED_CITE: consequences of missing mill test certificates in structural steel procurement] Engineering inspectors in Saudi Arabia and Nigeria routinely reject shipments lacking verifiable MTC documentation, causing port demurrage charges that exceed the material cost. Our practice of caliper-testing every tube before loading and photographing results eliminates disputes over wall thickness claims.
Procurement Advantages for Global Buyers
We operate as a dedicated plate and coil division within Shandong Xin Jiyuan Special Steel Tube Co., Ltd, maintaining large ready stock of Q235B square and rectangular tubes across the 20×20 to 150×150 mm range. Every piece carries original mill test certificates with heat number traceability, verified by our in-house quality team before dispatch. Custom cutting services deliver exact lengths from our 6–12 m stock, while professional heavy cargo logistics teams handle flatbed and open-top container loading to prevent transit damage. Third-party inspection through SGS or BV is available upon request, and our ISO 9001:2015 and CE certifications meet procurement requirements for regulated markets worldwide.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition (C, Si, Mn, P, S limits) and mechanical properties per GB/T 700
- CE certificate confirming compliance with EN 10219 for cold-formed welded structural hollow sections
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report verifying dimensional accuracy and surface quality
- Material traceability linking each bundle to specific heat numbers and production dates
- Complete customs documentation including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235B square and rectangular tubes bundled with steel strips and edge protectors to prevent corner damage during ocean transit
- Hot-rolled non-oiled surface left untreated to avoid coating damage, with bundles wrapped in waterproof paper for weather protection
- Mixed-size container loading optimized for 20×20 to 150×150 mm profiles, maximizing weight utilization within container limits
- Custom cutting to exact lengths from 6–12 m stock reduces on-site waste and eliminates field cutting for frame assemblies
- Each bundle labeled with heat number, steel grade Q235B, dimensions, and piece count for site identification
- FOB, CIF, and DDP shipping terms available with professional flatbed and open-top container loading experience
Request Quotation with Mill Test Certificate
Submit your Q235B square and rectangular tube requirements including section dimensions, wall thickness, length, quantity, and destination port to receive a detailed quotation with material specifications and mill test certificate samples. Our team responds within 12 hours with pricing, processing options, and delivery schedules tailored to your project timeline.
Start Your Q235B Hollow Section Procurement
Send specifications to receive quotations with original mill test certificates and custom cutting options.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjyplate.com
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjyplate.com
