Description
Factory-Direct Galvanized ERW Tubes — In-house steel production and fabrication under one roof ensure material traceability from billet to finished Q235B/Q345B square and rectangular tubes with full mill certification.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B ERW Welded Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (SHS / RHS) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, St37, St37-2, St42, St35, St35.4, St52.4 |
| Standard | GB |
| Section Shape | Square / Rectangular / Round |
| Length | 6 m / 12 m |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Galvanized |
| Tolerance | ±1% |
| Processing Service | Cutting, Welding, Punching, Bending |
| Technology | Hot Rolled / Cold Rolled / Galvanized |
| Invoicing | By Theoretical Weight |
| Place of Origin | Tianjin, China |
| MOQ | 25 Tons |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Industrial Construction | Building frames, warehouse structures, logistics center columns and beams |
| Oil & Gas Infrastructure | Fluid transport pipelines, gas distribution networks, chemical fertilizer conveyance |
| Renewable Energy | Solar panel support structures, wind turbine base frames |
| Construction Scaffolding | Scaffolding systems, temporary support structures, formwork frames |
| Mechanical Engineering | Hydraulic cylinder bodies, drill pipe casings, boiler support frames |
When Galvanized Coating Thickness Decides Site Acceptance
Zinc layer uniformity on ERW welded seams is where most shipment disputes originate.
I have seen entire container loads of galvanized square and rectangular steel tubes held at port because the weld line showed visible thinning compared to the flat surface. Third-party inspectors measure coating thickness at multiple points per piece — and the weld seam is always the weak spot. When a galvanized square and rectangular steel tube supplier cannot guarantee consistent zinc adhesion across the ERW weld, the buyer faces re-galvanizing costs on-site or outright rejection. [NEED_CITE: hot-dip galvanized coating thickness requirements for structural hollow sections]
Matching Structural Frames to Corrosive Site Environments
Galvanized ERW welded square and rectangular steel tubes in Q235B and Q345B grades serve industrial buildings and warehouse structures where atmospheric corrosion resistance matters more than extreme pressure containment. The hot-dip galvanizing process provides a metallurgical zinc-iron bond that outperforms paint systems in humid coastal or industrial atmosphere conditions. For EPC firms sourcing structural steel from China, specifying galvanized SHS/RHS eliminates the need for on-site surface treatment — cutting project timelines and removing weather dependency from the construction schedule.
Engineering Compliance and Certification Requirements
Structural hollow sections used in load-bearing frames must conform to dimensional tolerances and material certification standards that satisfy both design engineers and customs authorities. Q235B roughly corresponds to S235JR in the EN system, while Q345B aligns with S355JR — but equivalence tables alone do not satisfy port inspectors. [NEED_CITE: steel grade equivalence between GB and EN standards] CE marking per EN 10219 is mandatory for EU-bound structural steel, and the mill test certificate must show heat-by-heat chemical composition and mechanical test results traceable to the original steelmaking batch. For projects in the Middle East and Southeast Asia, third-party inspection by SGS or BV before shipment is often a contractual requirement — not an option.
Understanding ERW Welding and Galvanizing for Structural Tubes
The ERW (Electric Resistance Welded) process forms the longitudinal seam by passing high-frequency current through the steel strip edges, creating a forge-welded joint without filler metal. This method suits square and rectangular hollow sections in the small-to-medium size range where seamless manufacturing would be cost-prohibitive. Hot-dip galvanizing after ERW welding provides corrosion protection for both the base metal and the weld zone — the zinc coating typically ranges from 40 to 80 micrometers depending on immersion time and steel chemistry. The ±1% dimensional tolerance on these galvanized square and rectangular steel tubes ensures that connection plates and bolt holes align during assembly, reducing field-fit grinding and rework.
Hidden Costs of Unverified Material Certification
Ordering structural steel tubes based on price alone — without verified mill test certificates and third-party inspection — exposes the project to material rejection at destination port. I have watched 200-ton shipments of square and rectangular tubes sit in bonded warehouses because the mill cert showed S355J2 but independent lab testing revealed substandard impact toughness values. The buyer then faces three choices: pay for re-testing and accept the material, arrange return shipment at multiples of the original freight cost, or source replacement material locally at premium prices. [NEED_CITE: material certification requirements for structural steel imports] None of these outcomes saves money — and all of them delay project completion.
Why Project Buyers Source Galvanized Tubes Directly from Our Mill
We operate our own steel production facility with three production lines and over 2,800 specifications in raw material inventory — meaning the galvanized ERW welded square and rectangular steel tubes we deliver come from steel we melted, rolled, welded, and galvanized ourselves. There is no gap between material supplier and fabricator, no broken traceability chain, and no excuse for “the mill cert does not match the physical material.” Our in-house laboratory issues mill test certificates for every heat number, and we welcome SGS or BV inspection at any production stage. For projects requiring CE certification per EN 10219, we provide complete documentation packages including WPS, PQR, dimensional inspection reports, and coating thickness measurements. Professional loading teams handle oversized structural components with proper lashing and edge protection to preserve the galvanized coating during ocean transit.
Documentation & Compliance
- Mill test certificate documenting Q235B/Q345B chemical composition and mechanical properties per GB standards, with heat number traceability to the original steelmaking batch
- CE certificate confirming compliance with EN 10219 for cold-formed welded structural hollow sections, required for EU customs clearance
- ISO 9001 quality management system certificate covering the full production process from raw material incoming inspection to finished product dispatch
- SGS or BV third-party inspection report available upon request, covering dimensional checks, coating thickness measurement, and visual weld inspection
- Material traceability documentation linking each bundle to its heat number, with stencil markings on every tube for on-site verification
- Complete export documentation package including commercial invoice, packing list, bill of lading, and certificate of origin for destination customs clearance
Packaging, Loading & Delivery
- Galvanized Q235B/Q345B square and rectangular steel tubes packed in steel strip bundles with edge protectors to preserve the zinc coating during handling and ocean transit
- Six-meter and twelve-meter lengths loaded in 20-foot and 40-foot containers with optimized stowage plans to maximize payload while preventing bundle movement
- Surface protection maintained through proper separation materials between galvanized tubes and steel strapping to avoid zinc scratching or iron contamination
- Heat number and steel grade stenciled on each tube end for on-site identification and traceability verification during installation
- FOB, CIF, and DDP shipping terms available with professional loading supervision and container sealing before port departure
- Custom cutting to non-standard lengths available upon request, with MOQ of 25 tons per shipment for galvanized ERW welded square and rectangular steel tubes
Requesting Quotation and Technical Documentation
Submit your project specifications including steel grade (Q235B, Q345B, or equivalent), section dimensions, wall thickness, total tonnage, and destination port — we respond within 24 hours with a detailed quotation covering material, galvanizing, packaging, and freight costs. Our engineering team reviews your drawings and confirms shop drawing details before production begins, ensuring dimensional accuracy and compliance with your project standards. Mill test certificates, CE documentation, and third-party inspection arrangements are confirmed at the quotation stage — no surprises at the port.
Frequently Asked Questions
Q: How do Q235B and Q345B grades compare to S235JR and S355JR in European standards?
A: Q235B generally corresponds to S235JR in yield strength range, while Q345B aligns with S355JR — but formal equivalence requires cross-referencing chemical composition limits and mechanical property test methods. We provide grade comparison tables and can supply material tested to dual standards if your project requires it.
Q: Can you arrange third-party inspection before shipment?
A: Yes, SGS and BV inspection services are available at any production stage — from raw material verification through dimensional checks, coating thickness measurement, and final visual inspection. The inspection scope and acceptance criteria are confirmed in the contract before production begins.
Q: What is the minimum order quantity for galvanized ERW square and rectangular steel tubes?
A: The MOQ is 25 tons per shipment. For mixed-size orders, we can combine multiple section dimensions in one container to meet the minimum weight requirement while matching your project bill of materials.
Q: Do you provide CE certification for EU projects?
A: Yes, our galvanized structural hollow sections carry CE marking per EN 10219, and we provide the complete Declaration of Performance and factory production control documentation required for EU customs clearance and project approval.
Q: Can you cut tubes to non-standard lengths?
A: Custom cutting is available for lengths outside the standard 6-meter and 12-meter range. Cutting tolerances, minimum quantities, and additional processing costs are confirmed during the quotation stage based on your specific requirements.
Get Your Galvanized ERW Square and Rectangular Steel Tube Quotation
Send your project drawings, steel grade requirements, and destination port details to receive a comprehensive quotation with mill test certificate samples and delivery timeline within 24 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
