Description
Factory-Direct GI SHS/RHS Supply — Q235B galvanized square steel tube produced on three dedicated ERW lines with zinc coating verified by in-house chemical laboratory before dispatch.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Galvanized Square Steel Tube |
| Product Type | Galvanized Square & Rectangular Steel Tube (GI SHS/RHS) |
| Steel Grade | Q195, Q215, Q235, Q345, 10#, 20#, 45#, 16Mn, ASTM A53 (Grade A/B), St37, St42, St35.4, St52.4 |
| Standard | BS, EN, GB, AISI, ASTM, DIN, JIS |
| Section Shape | Square / Rectangular / Round |
| Size Range | 10 mm – 1000 mm |
| Wall Thickness | 0.6 mm – 28 mm |
| Length | 1 m – 12 m |
| Technique | ERW (Hot Rolled / Cold Rolled) |
| Surface Treatment | Galvanized (Zinc Coating 30–275 g/m²); also Bare, Oiled, Color Paint, 3PE, PVC |
| Tolerance | ±1% |
| Ends | Plain / Beveled / Threaded with couplings or sockets |
| Application | Building structures, industrial frameworks, bridges, ships, boilers, pressure vessels, automotive manufacturing, general engineering structures |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & EPC | Building frames, column bracing, mezzanine support, curtain wall sub-frames |
| Infrastructure | Bridge handrails, solar mounting structures, highway sign gantries |
| Machinery Manufacturing | Conveyor frames, equipment bases, crane boom sections, hydraulic support columns |
| Industrial Engineering | Pipeline racks, platform grating supports, warehouse purlin systems |
| Automotive & Transport | Chassis cross-members, roll-over protection structures, trailer underbody frames |
What Zinc Coating Consistency Costs on a Galvanized Structural Order
A 20 μm shortfall in zinc thickness can block customs clearance or trigger on-site rejection.
I once inspected a batch of galvanized rectangular tubes bound for the Middle East — the mill certificate claimed 65 μm, but portable coating gauge readings across the bundle averaged 42 μm. The entire container was held at the destination port. For a Q235B galvanized square steel tube, buyers specify zinc coating to resist corrosion in a given environment, and inconsistent coating defeats the purpose of the entire procurement. Beyond coating weight, dimensional tolerance on wall thickness and corner geometry determines whether the tube fits the connection detail drawn by the engineer. [NEED_CITE: EN 10219 cold-formed structural hollow section dimensional tolerance requirements]
Matching Load Paths and Corrosion Zones in Structural Frames
A Q235B galvanized square steel tube with wall thickness between 2 mm and 10 mm serves as primary compression members in portal frames and as secondary bracing in industrial sheds. The galvanized zinc coating at 60–120 g/m² handles C3–C4 atmospheric corrosion environments typical of urban and light-industrial sites, while projects in coastal or chemical-exposure zones require 200–275 g/m² coating or supplementary 3PE over-galvanizing. ERW welding produces a continuous longitudinal seam that, when properly annealed and galvanized, delivers uniform coating adhesion across the weld zone — critical because the weld seam is typically the first location where coating peels under field cutting or drilling.
Structural Code Compliance and Certification for Cross-Border Delivery
Engineering specifications for galvanized hollow sections in Europe reference EN 10219 for cold-formed welded structural tubes and EN 10210 for hot-finished sections, both requiring CE marking under the Construction Products Regulation. North American projects typically call for ASTM A500 Grade B or C, while Gulf Cooperation Council tenders often accept GB/T 6728 or EN equivalents with third-party inspection. For a Q235B galvanized square steel tube exported to regulated markets, the mill test certificate must trace chemical composition and mechanical results to the heat number, and the CE declaration must cite the correct harmonized standard — missing either document delays customs clearance by weeks. [NEED_CITE: CE marking requirements for structural steel hollow sections under EU Construction Products Regulation]
Steel Grade Selection and ERW Process Fundamentals
Q235B remains the default structural grade across China, Southeast Asia, and Africa due to its balanced yield strength and weldability; it corresponds roughly to S235JR in EN and ASTM A36 in the US system, though equivalence is never exact and project engineers must confirm acceptance. Q345 (or 16Mn) steps up to higher yield for heavily loaded columns and crane-runway beams, while ASTM A53 Grade A and B serve pressure and fluid-transport applications where the galvanized coating protects against internal scaling. The ERW process — whether fed from hot-rolled or cold-rolled coil — produces a longitudinal weld that is flash-trimmed and heat-treated before galvanizing, ensuring the weld zone achieves coating adhesion comparable to the parent metal. Wall thickness tolerance of ±1% means a nominal 4.0 mm wall measures between 3.96 mm and 4.04 mm; specifying theoretical-weight invoicing avoids disputes caused by mill rolling practices that push actual thickness toward the lower limit. [NEED_CITE: steel grade equivalence mapping between GB Q-series and EN S-series]
The Hidden Cost of Unverified Coating and Tolerance
Ordering a Q235B galvanized square steel tube based on a supplier’s self-declared coating weight — without third-party verification — risks three failure modes: zinc thickness below specification accelerates corrosion and voids the project warranty; wall thickness below the tolerance band reduces load-bearing capacity and fails structural inspection; and missing or mismatched mill certificates block customs clearance in the EU, Middle East, and Australia. Replacing rejected tubes after mobilization costs multiples of the original material price in demurrage, re-fabrication, and schedule delay. [NEED_CITE: consequences of non-conforming galvanized coating in structural steel applications]
Procurement Confidence Backed by Verified Production Capability
Every Q235B galvanized square steel tube leaving our Jinan facility passes through an in-house physical and chemical laboratory that tests zinc coating weight by gravimetric method, verifies wall thickness with ultrasonic gauges, and records mechanical properties per heat number. Our three ERW production lines cover over 2,800 cross-section specifications with wall thickness up to 28 mm, eliminating the need to split orders across multiple mills. We hold 41 invention patents — including China’s original sharp-corner rectangular tube technology — and maintain Lloyd’s CE certification under EN 10219 and EN 10210, Singapore FPC, and ISO 9001:2015, so export documentation matches the destination market’s regulatory framework. SGS and BV third-party inspections are arranged on request before container sealing, and our loading teams use purpose-built cradles and edge protectors to prevent zinc coating damage during ocean transit.
Documentation & Compliance
- Mill Test Certificate documenting Q235B chemical composition (C, Mn, Si, S, P) and yield/tensile results per GB/T 6728 or EN 10219, traceable to heat number
- CE Certificate issued under EN 10219 (cold-formed) or EN 10210 (hot-finished) for EU customs and construction product compliance
- ISO 9001:2015 quality management certificate covering ERW welding, galvanizing, and dimensional inspection processes
- SGS or BV third-party inspection report verifying zinc coating weight, wall thickness, and visual quality before shipment
- Material traceability sheet linking each bundle to its heat number, coil origin, and galvanizing batch
- Export customs package: commercial invoice, packing list, bill of lading, and certificate of origin formatted per destination requirements
Packaging, Loading & Delivery
- Q235B galvanized square tubes bundled with high-tensile steel strips and fitted with rubber edge protectors to preserve the zinc coating against friction during transit
- Zinc-coated surfaces wrapped in waterproof VCI film for ocean shipments to prevent white-rust formation in humid container environments
- Container loading optimized by nesting square sections of compatible side lengths (e.g., 50×50 inside 100×100) to maximize payload per 20ft or 40ft HC
- Cut-to-length service available for 1 m – 12 m requirements, with saw-cut ends deburred and re-galvanized touch-up applied to exposed edges
- Each bundle tagged with heat number, steel grade Q235B, section dimensions, wall thickness, and gross/net weight for site identification
- Shipping terms FOB Qingdao, CIF destination port, or DDP project site with full export documentation and container tracking
How to Initiate a Project Inquiry for Galvanized SHS/RHS
Submit your required section dimensions, wall thickness, steel grade, zinc coating weight, total tonnage, and destination port — we return a detailed quotation with unit pricing, production lead time, and applicable certification within 12 hours. For non-standard sizes outside the 10–1000 mm range or wall thickness beyond 28 mm, our engineering team provides a feasibility assessment and custom tooling timeline. We arrange SGS or BV pre-shipment inspection at your request and confirm container loading plans before sealing.
Frequently Asked Questions
Q: How does Q235B compare to S235JR and ASTM A36 for structural use?
A: Q235B is the Chinese national standard carbon structural grade with minimum yield strength at 235 MPa for thickness up to 16 mm. It is broadly comparable to S235JR under EN 10025 and ASTM A36 under US standards, though chemical composition limits and impact testing requirements differ. Project engineers should confirm acceptance of Q235B as an equivalent grade in the structural specification before ordering.
Q: What zinc coating weight should I specify for outdoor structural applications?
A: For indoor or sheltered environments (C2 corrosion category), 30–60 g/m² is sufficient. For outdoor urban and industrial exposure (C3–C4), 80–120 g/m² provides long-term protection. Coastal, marine, or heavy-industrial zones (C5) require 200–275 g/m² or a supplementary 3PE coating over the galvanized layer.
Q: Can you produce non-standard sizes outside the published range?
A: Yes. Our three ERW lines and custom roll-tooling capability allow production of non-standard side lengths and wall thicknesses beyond the 10–1000 mm / 0.6–28 mm published range. MOQ for custom tooling depends on section complexity and typically starts at 5 tons per size.
Q: What documentation do you provide for EU customs clearance?
A: We supply Mill Test Certificates per EN 10204 3.1, CE marking under EN 10219 or EN 10210 as applicable, and can arrange Lloyd’s or third-party verification. The CE declaration of performance and DoP are included in the shipping document package.
Q: How do you prevent zinc coating damage during container loading?
A: Galvanized tubes are bundled with rubber-padded edge protectors, separated by timber dunnage, and secured with nylon straps to avoid steel-to-steel contact. Our loading supervisors photograph each layer during stuffing and provide a loading report before container sealing.
Secure Your Q235B Galvanized Square Steel Tube Supply
Send your section schedule, steel grade, coating requirement, and destination port to receive a quotation with mill test certificate preview and certification confirmation.
Mobile/WhatsApp/WeChat: +86 188 5315 7756 | Email: admin@sdxjypipe.com
