Description
Factory-direct Q235B GI square tubes — 2,800+ specifications in ready stock with original mill test certificates for every shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Galvanized Square Steel Tube |
| Product Type | Galvanized Square Steel Tube |
| Steel Grade | Q235B, Q235, Q195, Q355, S275, S275JR, A53, ST37 |
| Standard | ASTM, BIS, JIS, ISO 9001, CE, KS, PVOC, RoHS, SABS, SASO, SNI, SONCAP, TISI |
| Section Shape | Square |
| Size Range | 30×30mm (full range available per inquiry) |
| Wall Thickness | 1.2–20 mm |
| Length | 1–12m or as customer’s request |
| Technique | Hot Rolled Based / ERW |
| Surface Treatment | Galvanized (Zinc Coated Z30–Z180) |
| Spangle Type | Zero Spangle |
| Tolerance | ±1% |
| Invoicing | By theoretical weight |
| Processing Service | Bending, Cutting, Decoiling, Punching, Welding |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, scaffolding systems, perimeter fencing, solar farm support structures |
| Industrial Fabrication | Container manufacturing, machinery frames, corrugated sheet supports, small tool frames |
| Energy & Utilities | Boiler pipe supports, wind farm access structures, utility pole bases |
| Warehousing & Logistics | Racking systems, mezzanine floors, conveyor structures |
What Zinc Coating Class Decides at Project Handover
Z30 versus Z180 is not a pricing choice — it is a corrosion lifespan decision tied to environment and inspection standards.
When a Q235B galvanized square steel tube arrives on site with zinc coating below the specified class, the third-party inspector flags it immediately. I have seen entire container loads held at project gates because the galvanizing thickness failed verification — not because the steel itself was weak, but because the surface protection could not meet the environmental exposure requirement. For coastal or high-humidity installations, Z180 provides long-term corrosion resistance that Z30 simply cannot deliver. The cost difference per ton is marginal compared to the expense of replacing corroded structural members two years into service. [NEED_CITE: hot-dip galvanized coating thickness standards for structural steel]
Matching 30×30mm GI Tubes to Structural and Fabrication Requirements
The 30×30mm profile with 1.2–20mm wall thickness serves as a versatile module for both load-bearing frames and non-structural enclosures. In scaffolding and fencing applications, the zero spangle galvanized finish provides uniform appearance and consistent corrosion protection across welded joints. For container manufacturing and machinery frames, the non-oiled surface accepts painting and powder coating without additional pretreatment. As a Q235B galvanized square steel tube supplier, we supply standard sizes from ready stock and produce custom dimensions within typical production lead times.
Engineering Compliance and Certification Pathways
Structural applications require documentation that matches the destination market’s regulatory framework. CE certification under EN 10210 and EN 10219 governs European construction projects, while BIS certification is mandatory for Indian government tenders. ASTM A53 and A500 specifications apply to North American structural and mechanical applications. Each Q235B galvanized square steel tube shipment includes mill test certificates documenting chemical composition and dimensional compliance, with SGS or BV third-party inspection available for projects requiring independent verification. [NEED_CITE: EN 10219 cold-formed structural hollow section requirements]
Steel Grade Selection and ERW Process Fundamentals
Q235B remains the dominant structural carbon steel grade in Chinese mill production, offering reliable weldability and formability for general construction. The S275 and S275JR grades provide higher yield strength for applications requiring increased load capacity, while ASTM A53 serves mechanical and pressure applications in North American markets. The hot rolled based ERW process produces square tubes with consistent wall thickness and superior corner integrity compared to cold-formed alternatives. Galvanizing with Z30–Z180 zinc coating classes allows buyers to match protection level to environmental exposure — indoor warehouse racking requires minimal coating, while outdoor infrastructure demands maximum thickness. The ±1% tolerance on wall thickness ensures predictable weight calculation and structural performance.
Hidden Costs of Incorrect Specification and Missing Documentation
Ordering Q195 when the structural engineer specified Q235B creates a yield strength shortfall that only emerges during load testing or inspection. Shipping without CE or BIS certification to regulated markets results in customs holds that delay project timelines by weeks. Accepting negative tolerance beyond ±1% reduces actual wall thickness below design requirements, compromising structural integrity while appearing cost-effective on paper. These errors surface at the most expensive stage — after the container has arrived and the project schedule cannot absorb delays. [NEED_CITE: steel grade equivalence between GB Q series and EN S series standards]
Procurement Confidence Through Factory-Direct Supply
We operate three production lines running simultaneously, delivering monthly capacity exceeding 20,000 tons of galvanized and black steel products. Every Q235B galvanized square steel tube passes through our in-house laboratory with three-stage inspection before release. Our ready stock covers 2,800+ specifications, enabling urgent orders and split shipments without waiting for production slots. Factory-direct pricing eliminates intermediary margins, with volume discount programs reviewed every six months for long-term partners. Professional export documentation handling ensures customs clearance packages are complete and compliant with destination requirements. Container loading optimization maximizes payload per shipment, reducing per-ton freight costs for bulk buyers across 50+ countries.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition and dimensional compliance per GB/T 6728
- CE certificate confirming EN 10210/EN 10219 compliance for European construction projects
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report available for project-specific quality verification
- Material traceability by heat number linking each bundle to original slab chemistry and rolling records
- Complete customs documentation including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235B galvanized square tubes bundled with steel strips and edge protectors to preserve zinc coating during ocean transit
- Zero spangle surface protected by seaworthy wrapping preventing moisture contact and white rust formation
- 30×30mm and larger profiles loaded with optimized container plans maximizing payload for 1–12m lengths
- Heat number and steel grade markings stenciled on each bundle for site identification and traceability
- Cut-to-length service available for 1.2–20mm wall thickness tubes requiring specific project dimensions
- FOB, CIF, and DDP terms supported with professional logistics coordination from Shandong ports
Securing Your Quotation with Complete Technical Requirements
Submit your specification sheet including profile dimensions, wall thickness, steel grade, zinc coating class, total quantity, and destination port to receive competitive pricing within 12 hours. Request mill test certificates and third-party inspection options upfront to confirm compliance with your project’s regulatory framework. Our team provides container loading optimization and consolidated multi-product shipment options for buyers sourcing multiple steel categories.
Request Factory-Direct Pricing and Mill Test Certificates
Send your Q235B galvanized square steel tube requirements via email or WhatsApp to receive bulk pricing, certification documentation, and delivery schedules tailored to your project timeline.
Email: admin@sdxinjiyuan.com
WhatsApp: +86 188 5315 7756
