Description
Gate Check
Product draft identifier: Q235B/Q345B Galvanized Square/Rectangular Steel Tube — not null. Proceeding.
—
Factory-direct galvanized square and rectangular tubes — raw material from our own mill, fabricated and inspected under one roof before shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B Galvanized Square/Rectangular Steel Tube |
| Product Type | Square / Rectangular Hollow Section (SHS/RHS) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400, DC51D+Z, DC52D+Z, DC53D+Z |
| Standard | ASTM |
| Section Shape | Square / Rectangular |
| Size Range | Wall Thickness 0.5–200 mm |
| Length | 12 m |
| Technique | Hot Rolled / Cold Rolled |
| Surface Treatment | Galvanized (Zinc Coated) |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Machinery / Scaffolding / Furniture / Fluid transport |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & EPC | Building frames, column-to-beam assemblies, portal frames for industrial warehouses |
| Infrastructure | Scaffolding systems, temporary support structures, bridge handrails |
| Machinery & Equipment | Machine bases, conveyor support frames, hydraulic equipment stands |
| Furniture & Interior | Display racks, mezzanine flooring supports, decorative structural elements |
Why Galvanized Coating Thickness Decides Site Acceptance Before the First Bolt Is Tightened
A zinc layer below specification triggers third-party rejection at destination — re-coating on site costs more than the tubes themselves.
When Q235B galvanized square steel tubes arrive at a Middle Eastern project site and the coating measures 40 μm against a 65 μm requirement, the entire batch fails inspection. Local hot-dip re-galvanizing means dismantling, transporting, re-processing, and reinstalling — weeks of delay on a critical path schedule. The root cause is rarely the steel grade; it is an uncontrolled galvanizing bath or skipped post-coating measurement. [NEED_CITE: EN ISO 1461 hot-dip galvanized coating thickness requirements]
How Q235B and Q345B Grades Match Structural Load Paths in Frame Construction
Q235B galvanized square steel tube in standard wall thicknesses serves well for secondary structures — purlins, bracing, and non-load-bearing frames where corrosion resistance matters more than peak strength. When the structural engineer specifies Q345B, the higher yield strength allows thinner walls for the same load capacity, reducing dead weight on portal frames and mezzanine systems. The galvanized zinc coating protects both grades equally in outdoor and semi-exposed environments, making them suitable for warehouse cladding supports and scaffolding where wet conditions persist.
Engineering Compliance and Certification Requirements for Galvanized Hollow Sections
Structural hollow sections used in load-bearing frames must comply with dimensional and tolerancing standards relevant to the destination market. For European projects, EN 10219 cold-formed hollow section requirements govern tolerances, sectional properties, and technical delivery conditions — and CE marking under EN 1090 is mandatory for structural steel components entering the EU. [NEED_CITE: EN 10219 cold-formed hollow section requirements] ASTM-compliant tubes serve North American and Middle Eastern EPC specifications where AISC and AWS welding procedures are the baseline. Material traceability by heat number, combined with third-party inspection reports from SGS or BV, closes the documentation gap that causes customs holds and site rejections.
Steel Grade Selection and Galvanizing Process: What Buyers Need to Know
The Q-series grades (Q195 through Q345B) follow the Chinese GB/T standard system, where the number indicates minimum yield strength in MPa. Q235B is the most widely specified grade for general structural work — comparable in application scope to S235JR in the EN system or ASTM A36 in the US system. Q345B offers higher strength for heavier load conditions, similar in positioning to S355JR or ASTM A572 Gr 50. The DC51D+Z through DC53D+Z grades are cold-rolling substrate steels with zinc coating, selected when formability matters — bending, flaring, or deep-drawn connections in light-gauge framing.
Hot-rolled square and rectangular tubes are formed from coil or plate, then welded along the longitudinal seam. The hot-rolled process produces thicker walls suited to primary structural members. Cold-rolled (cold-formed) tubes offer tighter dimensional tolerance and smoother surface finish, preferred for visible architectural applications and precision machinery frames. The galvanized zinc coating — applied by hot-dip or pre-galvanizing — provides sacrificial corrosion protection that outperforms painted black tube in humid, coastal, or industrial atmospheres.
Hidden Costs of Procuring Galvanized Tubes Without Verified Coating and Grade Documentation
When a buyer accepts the lowest quote without requiring a mill test certificate or coating thickness report, the risk transfers entirely to the project site. A tube stamped Q345B but actually rolled from Q235B substrate will deflect under design load — a structural safety failure that no amount of re-inspection can fix after erection. Missing or forged material certificates trigger customs rejection at destination ports, especially in markets enforcing EN 1090 or AISC compliance. [NEED_CITE: steel grade equivalence between EN and ASTM standards] Negative tolerance abuse — where wall thickness falls below the stated ±1% range — reduces load capacity and voids engineering sign-off. The real cost is never the unit price difference; it is the crane rental, the schedule extension, and the liability exposure.
Why Project Procurement Teams Source Q235B Galvanized Square Steel Tube from XJY Structure
Our vertical integration eliminates the material traceability gap. The raw steel for every Q235B and Q345B galvanized square steel tube we ship comes from our own mill with three production lines and over 2,800 specifications in stock — meaning the heat number on the mill test certificate traces directly back to our furnace records, not a third-party trader’s paperwork. Our fabrication workshop handles CNC cutting, drilling, bending, and welding (MIG/MAG/SAW) in-house, so a single purchase order covers raw tube and finished fabricated components under one quality system. Every batch passes through our in-house理化 laboratory for coating thickness verification before release — no shipment leaves without a measured zinc layer report attached to the MTC. We hold CE EN 1090 certification for structural steel fabrication, ISO 9001 quality management, and we coordinate SGS or BV third-party inspection at the buyer’s request. Professional loading plans for oversized and heavy fabricated assemblies minimize container waste and prevent coating damage during ocean transit.
Documentation & Compliance
- Mill test certificate documenting Q235B/Q345B chemical composition and mechanical properties per ASTM, traceable by heat number
- CE certificate confirming EN 10219 and EN 1090 compliance for galvanized structural hollow sections entering EU markets
- ISO 9001 quality management certificate covering the full production chain from raw steel to finished galvanized tube
- SGS or BV third-party inspection report verifying zinc coating thickness, dimensional tolerance, and surface quality
- Material traceability sheet linking each bundle to its heat number, rolling date, and galvanizing batch record
- Complete customs documentation package: packing list, bill of lading, certificate of origin, and commercial invoice
Packaging, Loading & Delivery
- Q235B and Q345B galvanized square and rectangular tubes bundled with steel strips and edge protectors to preserve the zinc coating during handling and ocean transit
- Plain-end tubes packed in seaworthy bundles with waterproof wrapping, sized for 20ft and 40ft container loading at 12 m standard length
- Galvanized surface protected by anti-scratch interleaving and nylon slings — no bare chain contact that would damage the zinc layer
- Custom cut-to-length service available: tubes cut to project-specific dimensions before packing, reducing on-site waste and secondary cutting
- Each bundle labeled with heat number, steel grade (Q235B/Q345B), section dimensions, wall thickness, and gross/net weight
- Delivery terms FOB, CIF, or DDP to project site; professional lashing plans for heavy fabricated assemblies shipped on flat racks or breakbulk
How to Request a Quotation with Full Material and Coating Documentation
Send your project drawings (PDF or DWG), steel grade requirement (Q235B, Q345B, or DC51D+Z through DC53D+Z), section dimensions, wall thickness, total tonnage, and destination port. We return a detailed quotation within 24 hours, including material cost, fabrication charges, coating specification, packing method, and shipping terms — with shop drawing review and production schedule attached. Confirm your required certification package (CE EN 1090, SGS/BV inspection, or project-specific MTC format) at inquiry stage so documentation is prepared in parallel with production.
Frequently Asked Questions
Q: What is the difference between Q235B and Q345B galvanized square steel tube in structural application?
A: Q235B is specified for general structural frames, bracing, and secondary members where moderate strength is sufficient. Q345B offers higher yield strength, allowing thinner wall sections for the same load capacity — preferred for primary portal frames, heavy-duty mezzanine systems, and crane support structures. Both grades receive the same galvanized zinc coating treatment for corrosion protection.
Q: Can you provide mill test certificates and third-party inspection for galvanized tubes?
A: Yes. Every shipment includes a mill test certificate documenting chemical composition and mechanical properties, traceable by heat number. We also coordinate SGS, BV, or TÜV third-party inspection at our facility before shipment, covering dimensional checks, coating thickness measurement, and visual surface inspection.
Q: What is the minimum order quantity for Q235B galvanized square steel tube?
A: The MOQ is 5 tons per order. For mixed-size orders, we can combine multiple section dimensions and wall thicknesses within one shipment to meet the minimum, supporting project-based procurement where multiple specifications are needed.
Q: Do you offer custom cutting, drilling, and welding services on galvanized tubes?
A: Yes. Our fabrication workshop provides CNC cutting, plasma cutting, drilling, bending, and MIG/MAG/SAW welding on galvanized square and rectangular tubes. Shop drawings are prepared for your approval before production begins, and all fabricated components receive coating touch-up per AWS standards at welded zones.
Q: How do you ensure the galvanized coating thickness meets project specifications?
A: Every batch is measured with a calibrated coating thickness gauge before packing. Results are recorded on the inspection report attached to the mill test certificate. If your project specifies a minimum zinc layer (e.g., 65 μm per EN ISO 1461), we verify compliance tube by tube and hold non-conforming material in the warehouse.
Get Your Q235B Q345B Galvanized Square Steel Tube Quote with Full Certification
Submit your section dimensions, steel grade, wall thickness, and destination port to receive a detailed quotation and mill test certificate sample within 24 hours.
Contact: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Website: www.xjystructure.com
