Description
Factory-Direct Galvanized Hollow Sections — Every Q235B and Q345B welded square and rectangular steel tube ships with original mill test certificates and CE EN 10219 documentation, eliminating middlemen markups and customs clearance delays.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B / Q345B Welded Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (Hollow Section) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, St37, St37-2, St35, St35.4, St42, St52.4 |
| Standard | GB |
| Section Shape | Square / Rectangular |
| Length | 6 m / 12 m |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Galvanized |
| Tolerance | ±1% |
| Processing Service | Cutting, Welding, Punching, Bending |
| Invoicing | By Theoretical Weight |
| Oiled or Non-oiled | Non-oiled |
| Application | Steel structures, Construction frames, Metal building materials, Prefab houses, Fluid pipe, Gas pipe, Structure pipe |
| MOQ | 25 Tons |
| Origin | China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Steel structure frames for industrial plants, warehouse skeletons, equipment support platforms |
| Construction Companies | Prefab house columns and beams, metal building purlins, high-rise structural bracing |
| Machinery Manufacturers | Conveyor system frames, automation equipment bases, precision hollow section assemblies |
| Infrastructure Developers | Bridge handrail posts, solar panel mounting structures, utility pole foundations |
What Negative Tolerance Exceedance Costs on a Galvanized Structural Frame Order
A 0.5mm wall-thickness shortfall turns a compliant shipment into rejected scrap at the project site.
When galvanized welded square and rectangular steel tubes arrive with wall thickness below the specified tolerance, third-party inspectors flag the entire batch — regardless of whether the steel grade itself is correct. On Middle East prefab projects, I have watched containers of hollow sections get held up because the actual weight diverged significantly from theoretical invoicing weight, triggering compliance audits that delayed steel frame erection by weeks. The hidden cost is not just the material replacement; it is the re-fabrication labor, the crane idle time, and the cascading delay to follow-on trades. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
How Galvanized ERW Hollow Sections Match Prefab and Structural Frame Demands
The hot-dip galvanized coating on these Q235B and Q345B welded square and rectangular steel tubes provides corrosion resistance that extends service life in exposed environments — coastal construction sites, industrial zones with chemical exposure, and outdoor prefab assemblies where repainting is impractical. The ERW welding process produces a consistent longitudinal seam that maintains structural continuity under compressive and bending loads typical of building frames. With ±1% dimensional tolerance, the tubes fit precisely into pre-engineered connection plates and base brackets, reducing on-site adjustment time.
Structural Compliance and Certification Requirements for Global Projects
Load-bearing steel structures require hollow sections that conform to recognized engineering standards — EN 10219 for European markets, ASTM A500 for North American specifications, and GB standards for domestic Chinese projects. The galvanized welded square and rectangular steel tube in Q235B and Q345B grades meets these framework requirements when supported by proper mill test certificates documenting chemical composition and mechanical properties. For projects in the EU, Lloyd’s Register CE certification under EN 10210 and EN 10219 is often mandatory for customs clearance and structural approval. [NEED_CITE: CE marking requirements for structural steel hollow sections under EN 10210]
Understanding Q-Series and St-Series Steel Grades in Welded Hollow Sections
The Q235B and Q345B designations follow the Chinese GB standard system, where the number indicates minimum yield strength in MPa. Q235B offers moderate strength suitable for general structural frames and prefab house skeletons, while Q345B provides higher yield strength for heavier load-bearing applications. These grades correspond roughly to S235JR and S355JR in the European EN system, and St37 and St52 in the German DIN framework — though exact equivalence requires verification against project specifications. The ERW welding technique creates a longitudinal seam through electric resistance welding, which is cost-effective for standard structural hollow sections and maintains consistent mechanical properties along the tube length. Hot-dip galvanizing applies a zinc coating that provides both barrier protection and sacrificial cathodic protection against corrosion.
The Hidden Costs of Sourcing Non-Compliant Galvanized Hollow Sections
Purchasing galvanized welded square and rectangular steel tubes without verified mill test certificates or proper CE documentation creates multiple downstream risks: customs authorities may hold shipments pending material verification, third-party inspectors may reject batches that fail dimensional checks, and structural engineers may refuse to approve frames built from untraceable steel. The cost of re-ordering compliant material, paying demurrage charges, and rescheduling construction crews far exceeds any initial price savings from uncertified suppliers. [NEED_CITE: steel grade equivalence verification between GB Q-series and EN S-series standards]
Why Project Procurement Teams Choose Our Galvanized Hollow Section Supply
Every galvanized welded square and rectangular steel tube we produce undergoes testing in our in-house physical and chemical laboratory, with results documented in original mill test certificates provided per batch. Our factory-direct model eliminates trading company markups, while our 2,800+ specification range covers square and rectangular sections across multiple wall thicknesses and lengths — reducing the need to coordinate with multiple suppliers. We hold Lloyd’s Register CE certification under EN 10210 and EN 10219, ISO 9001:2015 quality management certification, and can arrange SGS or BV third-party inspection upon request. Our proprietary sharp-corner rectangular tube technology fills gaps in the global market for sections requiring tight corner radii, and our professional loading team optimizes container stowage to minimize freight costs for 6m and 12m lengths.
Documentation & Compliance
- Mill test certificate documenting Q235B and Q345B chemical composition, yield strength, and tensile properties per GB standard
- Lloyd’s Register CE certificate under EN 10210 and EN 10219 for European market structural compliance
- ISO 9001:2015 quality management system certificate covering production and testing processes
- SGS or BV third-party inspection report available upon request for independent verification
- Material traceability by heat number linking each tube to its original steel coil and production batch
- Complete customs documentation package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Galvanized welded square and rectangular steel tubes bundled with steel strips and edge protectors to preserve zinc coating during ocean transit
- Non-oiled surface finish requires careful handling to prevent white rust formation; bundles wrapped in waterproof paper for container shipping
- 6m and 12m lengths loaded in 20ft and 40ft containers with optimized stowage plans to maximize payload while maintaining weight distribution
- Cut-to-length, punching, and bending services available to reduce on-site fabrication waste and labor costs
- Each bundle marked with heat number, steel grade, and dimensional specifications for site identification and traceability
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination to 50+ countries
Submit Specifications for Galvanized Hollow Section Quotation
Provide your required steel grade (Q235B, Q345B, or equivalent), section dimensions, wall thickness, total quantity, and destination port to receive a detailed quotation including unit price, production lead time, and applicable certifications. We will confirm mill test certificate availability, CE documentation requirements, and container loading optimization before contract signing.
Request Your Galvanized Hollow Section Quote Today
Send your specifications via email or WhatsApp to receive a comprehensive quotation with mill test certificate samples and delivery timeline within 12 hours.
Email: admin@sdxjysteel.com
WhatsApp: +86 188 5315 7756
