Description
Factory-Direct Mill Supply — Q235B and Q345B galvanized square steel tubes produced on dedicated ERW lines with in-house coating thickness verification before every shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B Galvanized Square Steel Tube |
| Product Type | Galvanized Square Steel Tube |
| Steel Grade | Q235B, Q345B, SS400, A53 Grade B, A500 Grade A/B/C, S355JR, STK400, ST42.2 |
| Standard | ASTM A53, ASTM A500, ASTM A36, BS 1387, EN 10255, ISO 65, DIN 2440, JIS G3444, GB/T 3091, GB/T 13793 |
| Section Shape | Square |
| Size Range | 21.3 mm – 660 mm (1/2″ – 26″) |
| Length | 5.8 m / 6 m / 11 m or custom |
| Technique | Cold Rolled / Hot Rolled (ERW) |
| Surface Treatment | Pre-Galvanized / Hot-Dip Galvanized |
| Tolerance | ±1% |
| Pipe Ends | Plain / Beveled / Threaded / Grooved |
| Processing Service | Welding, Punching, Cutting, Decoiling, Bending |
| Application | Steel structures, construction frames, fluid transport, hydraulic machinery, scaffolding |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC & Construction | Building frames, scaffolding systems, structural columns for commercial and industrial projects |
| Machinery Manufacturing | Hydraulic cylinder barrels, conveyor support frames, precision equipment bases |
| Infrastructure & Energy | Solar panel mounting structures, fluid transport lines for oil, gas and water, boiler systems |
| System Integration | Automated warehouse racking, industrial platform supports, material handling frameworks |
Why Zinc Coating Thickness Determines Whether Your Container Clears Customs
A galvanized square steel tube that fails third-party coating inspection at destination port creates weeks of delay, re-inspection fees, and potential rejection — regardless of how competitive the unit price was at origin.
Procurement teams across the Middle East and Southeast Asia regularly encounter shipments where pre-galvanized coatings measure below the specified threshold after ocean transit corrosion or improper storage at the mill. When SGS or BV inspectors pull random samples at Jeddah, Laem Chabang, or Durban, inconsistent zinc thickness triggers full-batch re-testing. The Q235B Q345B galvanized square steel tube must carry verifiable coating data on the mill test certificate, not just a general statement of “galvanized.” [NEED_CITE: hot-dip vs pre-galvanized coating thickness standards for structural hollow sections]
Matching Galvanized Square Tubes to Structural and Corrosion Environments
The Q235B Q345B galvanized square steel tube serves projects where both structural load-bearing and atmospheric corrosion resistance matter simultaneously. Pre-galvanized finishes suit indoor structural frames and light-duty scaffolding where cost efficiency outweighs extreme weather exposure. Hot-dip galvanized coatings protect outdoor infrastructure, solar mounting systems, and marine-adjacent construction where salt spray accelerates corrosion. The ±1% dimensional tolerance ensures that welded connections and bolted joints fit without on-site reaming, while plain, beveled, threaded, or grooved ends match the connection method specified in engineering drawings.
Engineering Compliance and Certification Requirements
Structural hollow sections used in load-bearing frames must conform to recognized dimensional and mechanical standards. EN 10219 governs cold-formed welded structural hollow sections in European-spec projects, while ASTM A500 covers equivalent requirements for North American construction. The Q235B Q345B galvanized square steel tube produced under GB/T 13793 meets Chinese domestic standards and can be cross-referenced to S235JR or A500 Grade B for international projects. CE certification under EN 10210 and EN 10219 is mandatory for EU market entry, and original mill test certificates documenting chemical composition and mechanical properties per heat number prevent customs holds. [NEED_CITE: EN 10219 cold-formed structural hollow section certification requirements]
Steel Grade Selection and ERW Welding Process
Q235B offers adequate strength for general structural frames and scaffolding where extreme load capacity is not required. Q345B provides higher yield strength for heavy-duty construction columns and machinery bases that must resist deflection under sustained loads. SS400 and STK400 serve Japanese-spec projects, while A53 Grade B and A500 Grade B/C align with American standards for fluid transport and structural applications. The ERW (Electric Resistance Welding) process produces square tubes from cold-rolled or hot-rolled coil with a longitudinal weld seam, offering cost efficiency and consistent wall thickness across the 21.3 mm to 660 mm size range. Pre-galvanizing applies zinc coating before final forming, resulting in a uniform but thinner layer suitable for moderate environments. Hot-dip galvanizing immerses finished tubes in molten zinc, creating a thicker metallurgically bonded coating for harsh outdoor or industrial atmospheres. [NEED_CITE: difference between pre-galvanized and hot-dip galvanized coating processes]
Hidden Costs of Procuring Without Verified Coating and Certification
Ordering galvanized square tubes based solely on price per ton — without requiring mill test certificates, third-party inspection reports, or specific coating thickness data — exposes projects to material rejection at destination. Coatings that measure below specification fail SGS/BV inspection, triggering re-testing fees, demurrage charges, and potential shipment return. Missing CE documentation blocks EU customs clearance entirely. Non-standard sizes ordered without confirmed tolerance lead to on-site cutting waste and welding rework. The Q235B Q345B galvanized square steel tube must arrive with full traceability from heat number to final coating measurement. [NEED_CITE: consequences of missing mill test certificates in international steel procurement]
Procurement Confidence Through Mill-Direct Verification
Every Q235B Q345B galvanized square steel tube ships directly from production lines in Jinan — no trading company markup, no intermediate warehouse handling that risks coating damage. The in-house physical and chemical laboratory tests incoming coil, monitors weld seam integrity during ERW forming, and measures zinc coating thickness before bundling. Over 2,800 specifications in square, rectangular, and round profiles allow consolidated procurement from a single source, reducing coordination across multiple suppliers. Proprietary sharp-corner rectangular tube technology fills gaps where standard radiused corners cannot meet architectural or mechanical interface requirements. CE certification under EN 10210/EN 10219, ISO 9001:2015 registration, and acceptance of SGS/BV third-party inspection before shipment ensure that documentation matches physical product. Professional loading plans optimize container utilization for 5.8 m, 6 m, and 11 m lengths, with door-to-door logistics to 50+ countries.
Documentation & Compliance
- Mill Test Certificate documenting Q235B/Q345B chemical composition and mechanical properties per GB/T 13793, with heat number traceability
- CE Certificate confirming compliance with EN 10210/EN 10219 for structural hollow sections exported to European markets
- ISO 9001:2015 Quality Management System certificate covering production, inspection, and coating processes
- SGS or BV Third-Party Inspection Report verifying zinc coating thickness, dimensional tolerance, and surface quality before shipment
- Material Traceability Report linking each bundle to specific heat numbers, coil origin, and galvanizing batch
- Customs Documentation Package including commercial invoice, packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235B/Q345B galvanized square steel tubes bundled with steel strips and edge protectors to preserve zinc coating during ocean transit
- Pre-galvanized and hot-dip galvanized surfaces wrapped with waterproof paper and plastic film to prevent white rust formation in humid containers
- 5.8 m and 6 m lengths loaded in 20ft containers; 11 m lengths require 40ft open-top or flat-rack optimization with professional lashing plans
- Custom cut-to-length service available for 6 m and 11 m standard lengths, with cut ends deburred and re-coated if required
- Each bundle marked with heat number, steel grade (Q235B/Q345B), size specification, and coating type for site identification
- FOB, CIF, and DDP delivery terms with real-time tracking; professional loading supervision at Qingdao port
Securing Your Quote with Complete Technical Requirements
Submit your specification sheet including square tube dimensions (side length × wall thickness), steel grade (Q235B or Q345B), surface treatment preference (pre-galvanized or hot-dip galvanized), total quantity, and destination port. Receive a detailed quotation with unit pricing, production lead time, payment terms, and applicable certification within 12 hours. Request original mill test certificates and SGS/BV inspection reports for project compliance verification before confirming the order.
Start Your Galvanized Square Tube Procurement
Send your specifications, steel grade, quantity, and destination port to receive a detailed quotation with mill test certificate options.
Contact:
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjysteel.com
Website: www.sdxjysteel.com
Frequently Asked Questions
Q: What is the difference between pre-galvanized and hot-dip galvanized square tubes, and which should I choose?
A: Pre-galvanized tubes receive zinc coating before final forming, resulting in a uniform but thinner layer (typically 40-60 μm) suitable for indoor structures and moderate environments. Hot-dip galvanized tubes are immersed in molten zinc after forming, creating a thicker metallurgically bonded coating (typically 65-100 μm) for outdoor, marine, or industrial atmospheres. Choose pre-galvanized for cost efficiency in protected environments; choose hot-dip for maximum corrosion resistance.
Q: Can you provide Mill Test Certificates and third-party inspection reports for customs clearance?
A: Yes. Every shipment includes original Mill Test Certificates documenting chemical composition and mechanical properties per heat number. SGS or BV third-party inspection is available before shipment to verify coating thickness, dimensional tolerance, and surface quality. CE certificates under EN 10210/EN 10219 are provided for EU market compliance.
Q: What steel grade equivalents exist between GB/T, ASTM, and EN standards?
A: Q235B roughly corresponds to S235JR (EN) and A36/A53 Grade A (ASTM). Q345B aligns with S355JR (EN) and A572 Grade 50 (ASTM). SS400 and STK400 follow JIS standards for Japanese-spec projects. Cross-reference tables are available upon request for specific project requirements.
Q: Do you accept custom non-standard sizes and what is the MOQ?
A: Yes. Over 2,800 specifications are available, including custom non-standard sizes outside the 21.3 mm to 660 mm range. Custom lengths beyond 5.8 m, 6 m, and 11 m are available with cut-to-length service. The MOQ is 1 Ton for standard specifications; custom non-standard sizes may require higher minimum quantities depending on production setup.
Q: What are your delivery terms and typical production lead time?
A: FOB, CIF, and DDP terms are available. Typical production lead time is 15-25 days after deposit confirmation, depending on order quantity and specification complexity. Professional loading plans optimize container utilization, and door-to-door logistics serve 50+ countries including EU, North America, Middle East, Southeast Asia, and Africa.
