Description
Direct Mill Supply, No Middlemen — Q235B and Q345B galvanized square steel tubes produced from our own steel mill, with coating thickness verified by in-house gauges before every shipment leaves Jinan.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B / Q345B Galvanized Square Steel Tube |
| Product Type | Galvanized Square Steel Tube |
| Steel Grade | Q235B, Q345B, SS400 |
| Standard | ASTM A53, ASTM A500, ASTM A36, BS1387, EN10255, ISO65, DIN2440, JIS G3444, GB/T3091, GB/T13793 |
| Section Shape | Square |
| Size Range | 21.3mm–660mm (1/2″–26″) |
| Length | 5.8m / 6m / 11m or customized |
| Technique | Cold Rolled / Hot Rolled |
| Surface Treatment | Pre-Galvanized / Hot Dipped Galvanized |
| Tolerance | ±1% |
| Ends | Plain ends, Beveled ends, Threaded ends, Grooved ends |
| Application | Steel structures, Construction building frames, Fluid transportation, Machinery, Hydraulic systems, Power & boiler, Petrochemical |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Warehouse frames, industrial facility columns, commercial building structural supports |
| Steel Structure Engineering | EPC project trusses, platform beams, stairway handrails, connection assemblies |
| Fluid Transportation | Oil, gas, and water pipeline systems, hydraulic distribution networks |
| Machinery & Equipment | Conveyor structures, machinery frames, hydraulic cylinder housings |
| Power & Petrochemical | Boiler support structures, petrochemical pipe racks, power plant frameworks |
Where Coating Thickness Variance Costs You a Container at Customs
Inconsistent zinc coating is the single most common reason galvanized tubes fail third-party inspection at destination ports.
I have seen entire shipments of galvanized square tubes held at Jeddah because the measured coating thickness fell below the contract-specified minimum. The supplier had mixed pre-galvanized and hot-dipped batches without declaration. When the buyer’s SGS inspector pulled random samples, the variance was obvious — some tubes measured below 40μm while the purchase order required 60μm minimum. The container sat at port for weeks, demurrage accumulated, and the buyer had to negotiate a steep discount just to avoid rejection. [NEED_CITE: hot-dip galvanized coating thickness standards for structural steel]
Fragmented sourcing makes this worse. When your fabricator buys black tubes from one mill and sends them out for galvanizing, there is no single party accountable for the full chain — material chemistry, coating adhesion, and final dimensional tolerance all shift between hands. Our Galvanized Square Steel Tube Supplier operation keeps steelmaking, tube forming, and galvanizing under one roof, so every heat number traces back to our own mill test records.
How Q235B and Q345B Match Structural Frame Requirements
Q235B serves general construction frames where moderate load-bearing is sufficient — warehouse purlins, light-duty platforms, and non-critical bracing. Q345B steps in when the structural engineer specifies higher yield strength for main columns, long-span beams, or heavy-duty industrial frames. Both grades weld cleanly under standard MIG/MAG procedures, and our certified welders follow WPS qualified to AWS D1.1 and EN 1090. For projects in the Middle East and Southeast Asia, we regularly supply Q345B as a functional equivalent to S355JR under EN10219, with full chemical and mechanical documentation cross-referenced in the mill test certificate. Our Galvanized Square Steel Tube Supplier facility stocks over 2,800 specifications, so engineers do not need to redesign around stock availability.
Engineering Compliance Across ASTM, EN, and JIS Frameworks
Structural frames in the EU require EN10219 cold-formed hollow section compliance with CE marking, while North American projects specify ASTM A500 Grade B or C. Middle East tenders often accept a mix — ASTM for structural, BS1387 for fluid lines. Our Galvanized Square Steel Tube Supplier operation certifies to ASTM A53, ASTM A500, EN10255, JIS G3444, and GB/T3091 from the same production line, with documentation packages prepared per destination requirements. Dimensional tolerance holds at ±1%, verified through in-process checks at forming, welding, and post-galvanizing stages. [NEED_CITE: EN 10219 cold-formed structural hollow section dimensional tolerances] For projects requiring third-party validation, we welcome SGS, BV, or TÜV inspection at any production stage.
Steel Grade Selection and Galvanizing Process Explained
Q235B and Q345B belong to the Chinese GB/T 700 and GB/T 1591 grade systems. Q235B offers good formability and weldability for general structural use, while Q345B provides higher yield strength for load-critical members. SS400, the Japanese equivalent under JIS G3444, overlaps with Q235B in most mechanical properties. When specifying galvanized square tubes, the galvanizing method matters as much as the steel grade. Pre-galvanized tubes — coated from coil before forming — deliver uniform zinc distribution ideal for indoor or mild environments. Hot-dipped galvanized tubes, submerged in molten zinc after forming, build thicker coating at corners and weld seams, making them the correct choice for outdoor exposure, coastal projects, or industrial atmospheres. [NEED_CITE: pre-galvanized vs hot-dip galvanized coating performance comparison] The ±1% tolerance applies after galvanizing, accounting for the zinc layer build-up that can affect fit-up in bolted connections.
Hidden Costs of Buying the Wrong Grade or Coating
Specifying Q235B when the structural drawing calls for Q345B means the frame may pass visual inspection but fail load testing — a discovery that comes too late, after erection has begun. Ordering pre-galvanized tubes for a coastal warehouse in Dubai when hot-dipped was specified leads to premature corrosion at weld zones, triggering warranty claims and reputational damage with the end client. Missing or incomplete mill test certificates cause customs holds in countries that require material traceability for structural steel imports. [NEED_CITE: structural steel material traceability requirements for international projects] Every one of these failures traces back to a procurement decision made at the inquiry stage — before the first tube was even produced.
Why Project Teams Source Galvanized Square Steel Tube from Our Mill
Our vertically integrated operation eliminates the gap between material supplier and fabricator. The same facility that produces the raw steel plate and coil also forms, welds, and galvanizes the finished square tubes — so every heat number on the mill test certificate traces directly to our production records. We maintain over 2,800 specifications in stock, covering the full 21.3mm–660mm range in both Q235B and Q345B, which means project teams sourcing a Galvanized Square Steel Tube Supplier rarely face stock-out delays. Our welding procedures are qualified to AWS D1.1 and EN 1090, and our welders hold current certifications. For EU-bound shipments, we prepare CE-marked documentation per EN10210 and EN10219. Third-party inspection by SGS, BV, or TÜV is accepted at any stage. We handle professional packing for oversized square tubes, optimize container loading for mixed-size orders, and provide complete export documentation including certificate of origin for preferential customs treatment.
Documentation & Compliance
- Mill test certificate documenting Q235B or Q345B chemical composition and mechanical properties per GB/T700 and GB/T1591, with heat number traceability
- CE certificate confirming EN10219 cold-formed hollow section compliance for EU structural projects
- ISO 9001 quality management certificate covering the full production chain from steelmaking to galvanizing
- SGS or BV third-party inspection report verifying coating thickness, dimensional tolerance, and surface quality
- Material traceability report linking each bundle to its original heat number and galvanizing batch
- Complete customs documentation package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235B and Q345B galvanized square tubes bundled with steel strips and edge protectors to preserve zinc coating integrity during ocean transit
- Pre-galvanized and hot-dipped tubes separated by packaging type, with clear surface treatment labels on each bundle
- Mixed-size container loading optimized for 5.8m, 6m, and 11m lengths to maximize payload while protecting tube ends
- Custom cutting to project-specified lengths available, with cut ends deburred and touched up with zinc-rich paint
- Heat number and steel grade stenciled on each bundle, matching mill test certificate references
- FOB Jinan/Qingdao, CIF, and DDP delivery terms available with full container tracking until site arrival
Start Your Inquiry with Drawings and Specifications
Share your project drawings in PDF or DWG format along with required steel grades, dimensions, surface treatment preference, and destination port. Our engineering team reviews shop drawings, confirms material availability, and returns a detailed quotation within 24 hours — including fabrication schedule, coating specification, and complete documentation scope. For non-standard sizes or mixed-grade orders, we provide custom fabrication sequencing and container optimization before you commit.
Frequently Asked Questions
Q: What is the difference between pre-galvanized and hot-dipped galvanized square tubes?
A: Pre-galvanized tubes are coated from steel coil before forming, resulting in a thinner but more uniform zinc layer suitable for indoor or sheltered applications. Hot-dipped galvanized tubes are submerged in molten zinc after forming, building a thicker coating at corners and weld seams — the correct choice for outdoor, coastal, or industrial environments.
Q: Can Q235B and Q345B be supplied as equivalents to ASTM or EN grades?
A: Yes. Q235B overlaps with ASTM A36 and S235JR in mechanical properties. Q345B corresponds closely to S355JR under EN10219. We provide cross-reference documentation in the mill test certificate for projects requiring grade equivalence confirmation.
Q: What is the minimum order quantity for custom sizes?
A: Our MOQ is 1 Ton. For non-standard dimensions outside the 21.3mm–660mm range, we review feasibility based on your specific requirements and provide a custom production schedule.
Q: Do you provide documentation for EU customs clearance?
A: Yes. We supply CE-marked certificates per EN10219 for cold-formed structural hollow sections, along with mill test certificates, third-party inspection reports, and certificates of origin as required by EU import regulations.
Q: How do you ensure coating thickness consistency across a full order?
A: Every galvanized square tube is measured with coating thickness gauges at multiple points before packing. Results are recorded in the quality documentation package, and third-party inspection by SGS, BV, or TÜV is welcome at any production stage.
Request Your Galvanized Square Steel Tube Quotation Today
Submit your project specifications, steel grade requirements, and destination port to receive a detailed quotation with mill test certificate scope within 24 hours.
Company: 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
