Description
Factory-direct supply, no trading middlemen — Our own steel mill produces the raw Q235 and ASTM A500 Grade B strip, then rolls and galvanizes it into finished square tubes under one roof, giving you full material traceability from slab to shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 GI Square Hollow Section |
| Product Type | Galvanized Square and Rectangular Steel Tube |
| Steel Grade | Q235, Q195, Q215, Q345, ASTM A500 Grade B/C, S235JR, S355JR, St37, St52 |
| Standard | ASTM A500, GB/T 6728, EN 10219, EN 10210, JIS G3466, BS EN, DIN |
| Section Shape | Square / Rectangular |
| Size Range | 20×20 mm – 100×100 mm (standard); up to 1000 mm per supplier detail |
| Wall Thickness | 0.6 mm – 28 mm |
| Length | 1 m – 12 m or customized |
| Technique | ERW (Electric Resistance Welded) / Hot Rolled |
| Surface Treatment | Hot Dip Galvanized (Zinc Coating 30–275 g/m²) |
| Tolerance | ±1% |
| Ends | Plain / Beveled / Threaded with couplings |
| Application | Steel structures, construction frames, fencing, machinery frames, trailers, agricultural equipment, industrial equipment, sign posts, furniture |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Structural frames, scaffolding uprights, support columns for warehouses and industrial sheds |
| EPC & Prefabrication | Prefabricated steel building modules for Middle East, Southeast Asia, and African project sites |
| General Fabrication | Machinery frames, trailer chassis, fencing posts, and agricultural equipment supports |
| Commercial & Signage | Highway sign posts, lighting pole bases, and outdoor furniture frames |
Why Zinc Coating Thickness Still Fails Third-Party Inspection on Site
A galvanized square tube that passes mill inspection can still fail on-site复检 if the coating was applied to substandard base metal or stripped during transit.
I once received a batch of hot dip galvanized tubes in Dubai where the zinc layer scraped off under a fingernail. The supplier had used pre-galvanized strip and re-dipped it — a shortcut that looks fine at the factory gate but fails the moment a third-party inspector drags a coating thickness gauge across the surface. With an ASTM A500 Gr.B hot dip galvanized square tube supplier that controls its own steel production, the base metal chemistry is locked before galvanizing begins, so the zinc-iron alloy layer bonds properly and hits the 30–275 g/m² range consistently. [NEED_CITE: hot dip galvanizing coating adhesion requirements per ASTM A123]
Matching Load-Bearing Requirements for Structural Frame Applications
When an ASTM A500 Gr.B hot dip galvanized square tube is specified for warehouse columns or industrial building frames, the engineer is balancing axial load capacity against corrosion exposure. The hot dip zinc coating at 30–275 g/m² handles atmospheric corrosion for decades in most non-coastal environments, while the ERW seam — when produced under certified WPS — delivers corner integrity that matches the parent metal. Our fabrication workshop reviews shop drawings before cutting begins, so beam-to-column connections land on the correct flat face rather than a rounded corner, eliminating field rework.
Compliance Pathways for EU, North American, and Belt & Road Projects
Different markets demand different certification chains. EU projects require CE marking per EN 10219 or EN 10210, which means the mill must hold a Factory Production Control certificate and issue Declaration of Performance documents. North American buyers specify ASTM A500 Grade B or C and expect mill test certificates traceable by heat number. Belt & Road EPC firms often accept GB/T 6728 with SGS or BV third-party inspection. [NEED_CITE: EN 10219 cold-formed structural hollow sections certification requirements] An ASTM A500 Gr.B hot dip galvanized square tube supplier that ships to all three regions must maintain parallel documentation systems — not just one certificate template.
Steel Grade Selection: Q235 vs S235JR vs ASTM A500 Grade B
The Chinese Q235 grade roughly corresponds to European S235JR and American ASTM A500 Grade B in yield strength class, but the chemical composition limits — particularly carbon, manganese, and sulfur — differ slightly across standards. For welded structures, sulfur and phosphorus caps matter more than nominal yield, because high sulfur increases hot-cracking risk during MIG or SAW welding. Our mill issues separate MTCs for each standard, so a buyer specifying S355JR for a European warehouse gets the correct manganese-to-carbon ratio without substitution surprises. [NEED_CITE: steel grade equivalence between GB, EN, and ASTM structural steel standards]
The ERW process used for these square and rectangular tubes produces a longitudinal weld seam that, when properly normalized, achieves mechanical properties matching the parent strip. Hot rolled variants offer thicker walls up to 28 mm for heavy-duty trailer chassis or machinery frames where corner sharpness and weld seam uniformity under load are critical.
The Hidden Cost of Wrong Grade or Missing Certification
Specifying Q235 when the structural drawing calls for ASTM A500 Grade B may seem like a minor substitution, but the difference in elongation and impact toughness can cause a connection to fail brittle fracture under seismic or wind load. Worse, if the mill test certificate does not match the heat number stamped on the tube, the inspector rejects the entire batch — and replacing 20 tons of galvanized square tubes after customs clearance means paying for the material twice plus project delay penalties. [NEED_CITE: structural steel material traceability requirements per EN 10204]
Vertically Integrated Production Eliminates Material Gaps
Our own steel mill produces the hot rolled coil in Q235, Q345, and equivalent grades, then our fabrication division cuts, welds, and galvanizes it into finished square and rectangular hollow sections. This means one quality system covers the entire chain — no third-party coil supplier inserting off-grade material, no separate galvanizer cutting corners on zinc bath temperature. We hold CE certification per EN 10210 and EN 10219, ISO 9001 registration, and accept SGS, BV, or TÜV inspection before shipment. Custom lengths up to 12 m and non-standard dimensions beyond the 20×20 to 100×100 mm range are available with typical production lead times, and our engineering team reviews shop drawings for material optimization before fabrication begins.
Documentation & Compliance
- Mill Test Certificate documenting Q235 or ASTM A500 Grade B chemical composition and mechanical properties per GB/T 6728 or ASTM A500, traceable by heat number
- CE certificate per EN 10219 and EN 10210 for structural hollow sections destined for EU member states
- ISO 9001 quality management system certificate covering the integrated steel production and fabrication process
- SGS or BV third-party inspection report verifying zinc coating thickness, dimensional tolerance, and weld seam quality before shipment
- Material traceability sheet linking each bundle to its heat number, coil certificate, and galvanizing batch record
- Complete customs documentation including packing list, bill of lading, and certificate of origin for destination-country clearance
Packaging, Loading & Delivery
- Hot dip galvanized Q235 square tubes bundled with steel strips and edge protectors to prevent zinc coating damage during ocean transit
- Surface protection maintained by avoiding contact with bare steel or acidic materials; bundles wrapped in waterproof cloth for container shipping
- Loading optimization for 20×20 mm to 100×100 mm sections: nested stacking maximizes 20ft container payload while keeping weight within road transport limits
- Custom cut-to-length service available for 1 m to 12 m requirements, with beveled or threaded ends prepared per drawing specification
- Each bundle labeled with heat number, steel grade (Q235 / ASTM A500 Gr.B), size, and gross/net weight for site identification
- FOB, CIF, and DDP terms available with professional oversized cargo loading and complete export documentation
Getting Your Quotation and Material Certification in Motion
Send your project drawings in PDF or DWG format along with the specified steel grade, quantity, and destination port. Our engineering team responds within 24 hours with a detailed quotation covering material, galvanizing, packing, and freight — plus a shop drawing timeline and production schedule. If your project requires non-standard dimensions or specific certification packages for EU or North American compliance, we confirm feasibility and lead time before you commit.
Request Your ASTM A500 Gr.B Hot Dip Galvanized Square Tube Quote Today
Submit your specifications, steel grade, and target quantity to receive a detailed quotation with mill test certificate preview and production timeline.
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
Frequently Asked Questions
Q: What is the difference between Q235, S235JR, and ASTM A500 Grade B?
A: These three grades belong to different standard systems — Chinese GB, European EN, and American ASTM — but fall within the same yield strength class. The main differences lie in chemical composition limits, particularly for carbon, manganese, sulfur, and phosphorus. We issue separate mill test certificates for each standard so your specified grade is delivered exactly as called for on the drawing.
Q: How does hot dip galvanizing compare to pre-galvanizing for corrosion protection?
A: Hot dip galvanizing immerses the finished tube in a molten zinc bath, producing a coating of 30–275 g/m² with a zinc-iron alloy layer that bonds metallurgically to the steel surface. Pre-galvanized tubes are made from already-coated strip, so the weld seam and corners have thinner coverage. For structural applications exposed to weather or industrial atmospheres, hot dip provides significantly longer service life.
Q: Can you produce non-standard sizes outside the 20×20 to 100×100 mm range?
A: Yes. Our supplier detail lists capabilities up to 1000 mm side length and wall thickness up to 28 mm. Non-standard dimensions carry a separate MOQ and typical production lead times, which we confirm after reviewing your drawing and quantity requirements.
Q: How do you ensure material traceability from steel mill to finished galvanized tube?
A: Every bundle is tagged with a heat number that links back to the original coil certificate, chemical composition report, and galvanizing batch record. Our integrated mill-to-fabrication model means no third-party material enters the production chain, so the certification path remains unbroken from raw steel to shipped product.
Q: What third-party inspections do you accept before shipment?
A: We accept SGS, BV, and TÜV inspection at our facility before loading. The inspection covers zinc coating thickness, dimensional tolerance, weld seam quality, and visual surface condition. The inspection report is included in the shipping documentation package for your customs clearance and project handover.
