Description
Factory-Direct Hot Dipped Galvanized Square Steel Tube — ASTM A500 Gr.B and EN standard SHS produced on in-house ERW lines with full zinc immersion, shipped with original mill certificates.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Hot Dipped Galvanized ERW Square Steel Tube |
| Product Type | Welded Square Steel Tube (SHS) |
| Steel Grade | Gr.B, S235, S275, S355, STK400 |
| Standard | ASTM A500, ASTM A53, GB/T 3091 |
| Section Shape | Square |
| Size Range | 19mm × 19mm – 800mm × 800mm |
| Wall Thickness | 1 – 30 mm |
| Length | 5.8m / 6m / 11.8m / 12m / Random Length |
| Technique | Welded (ERW) / Seamless |
| Surface Treatment | Hot Dipped Galvanized / Black Painting / Varnish / Bare |
| Tolerance | ±1% |
| Ends | Plain |
| Invoicing | By Theoretical Weight |
| Application | Steel structures / Construction frames / Curtain wall / Support tubes / Building structures |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Curtain wall support frames, structural columns, mezzanine beams |
| Infrastructure | Bridge handrails, highway sign gantries, sound barrier posts |
| Industrial Facilities | Conveyor support structures, equipment platforms, pipe racks |
| Agricultural & Warehouse | Greenhouse framing, storage rack uprights, portal frame buildings |
Where Zinc Coating Thickness Decides Port Acceptance
A 25-micron gap between contract spec and actual reading can strand an entire container at destination customs.
Buyers sourcing hot dipped galvanized square steel tube from fragmented suppliers routinely face zinc coating disputes upon arrival. Pre-galvanized stock shipped as hot dipped, inconsistent immersion time across batches, or no independent lab verification — these are recurring issues on projects across the Middle East and Southeast Asia. When the port authority or project engineer pulls a coating thickness gauge and finds 45 microns against a 70-micron contract requirement, the entire lot gets flagged. Air-freighting replacement material or negotiating partial acceptance eats into margins that were already thin. [NEED_CITE: hot dip galvanizing coating thickness standards ASTM A123]
Matching Structural Load Paths to Square Section Geometry
Square hollow sections distribute torsional and compressive loads more evenly than open profiles, making the hot dipped galvanized square steel tube a preferred choice for moment-resisting frames and braced structures. The flat bearing surfaces simplify bolted and welded connections at nodes — no gusset plate shimming required. For curtain wall sub-frames and support tube arrays, the uniform exterior geometry allows consistent cladding attachment spacing. Our 19×19mm through 800×800mm range covers everything from light-gauge purlin bracing to heavy structural columns, with wall thickness up to 30mm for high-load transfer zones.
Engineering Code Compliance and Surface Durability
Structural designers specifying this product typically reference EN 1993-1-1 for member verification or AISC 360 for allowable stress design — the steel grades Gr.B, S235, S275, S355, and STK400 map directly to these frameworks. [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500 standards] Hot dip galvanizing provides sacrificial zinc protection rated for decades of atmospheric exposure in C3–C4 corrosion categories, eliminating the need for field painting on most outdoor structural applications. For projects shipping to the EU, CE marking per EN 10210 (seamless) or EN 10219 (welded) is mandatory for structural hollow sections; ASTM A500 Gr.B covers North American procurement. Dimensional tolerance of ±1% ensures that site-cut lengths and connection plates fit without forced alignment.
Steel Grade Selection and Welding Process Fundamentals
The five steel grades offered — Gr.B, S235, S275, S355, STK400 — span three major standard systems. Gr.B belongs to ASTM A500 and is the baseline structural grade for North American hollow section applications. S235 through S355 follow the EN 10025 / EN 10219 system, where the numeric suffix indicates minimum yield strength in MPa; S355 delivers roughly 50% higher yield than S235, directly reducing section size for the same load. STK400 is the JIS G 3466 grade used across Japanese-spec projects in Southeast Asia. ERW welding produces a longitudinal seam suitable for structural applications up to moderate wall thickness; for higher-pressure or critical dynamic loading, seamless options are available within the same size range. Hot dip galvanizing immerses the finished tube in molten zinc at approximately 450°C, creating a metallurgical zinc-iron alloy bond that outperforms electroplated or pre-galvanized coatings in adhesion and edge coverage. [NEED_CITE: hot dip galvanizing process metallurgical bond formation]
The Real Cost of Accepting Sub-Spec Galvanizing
When zinc coating falls below the specified minimum, the corrosion protection timeline collapses — a tube rated for 25 years in a C3 environment may show white rust within 3 years if the coating is 30% thinner than required. Beyond material replacement, the hidden costs cascade: project inspection rejection, customs hold at destination port, crane time wasted on re-installation, and contractual penalties for delayed handover. Certification gaps compound the problem — without original mill test certificates traceable to heat numbers, the entire batch becomes unverifiable and may need to be scrapped regardless of physical condition. [NEED_CITE: consequences of non-compliant galvanizing coating on structural service life]
Procurement Confidence Through In-House Verification
Every hot dipped galvanized square steel tube leaving our facility passes through a three-stage in-house inspection covering dimensional check, coating thickness measurement, and weld seam integrity before bundling. We operate three dedicated production lines with monthly capacity exceeding 20,000 tons, covering 2,800+ specifications — meaning your 800×800×20mm S355 order does not compete for line time with small-batch trials. Factory-direct pricing applies with no trading intermediary; volume discount tiers activate for repeat procurement partners. Original mill test certificates ship with every lot, and SGS or BV third-party inspection is available on request before container sealing. Our export team handles consolidated multi-product container loading — combining square tubes with plate, beam, or channel in a single shipment to reduce per-ton freight cost.
Documentation & Compliance
- Mill test certificate documenting Gr.B / S355JR chemical composition and yield strength per ASTM A500 or EN 10219, traceable to heat number
- CE certificate covering EN 10210 (seamless) and EN 10219 (welded) structural hollow sections for EU market access
- ISO 9001:2015 quality management certificate covering production, inspection, and dispatch processes
- SGS or BV third-party inspection report verifying zinc coating thickness, dimensional tolerance, and surface quality prior to loading
- Material traceability sheet linking each bundle to heat number, production date, and galvanizing bath record
- Full customs document package including packing list, bill of lading, and certificate of origin formatted for destination port requirements
Packaging, Loading & Delivery
- Hot dipped galvanized square steel tubes bundled with steel strips and edge protectors to prevent zinc coating abrasion during transit
- Seaworthy packaging with waterproof wrapping for ocean freight, preserving galvanizing integrity in humid container environments
- Container loading optimized by our export team — 6m and 11.8m lengths paired to maximize 20ft and 40ft GP utilization, reducing per-ton shipping cost
- Random length or cut-to-order options available within the 5.8m–12m range, with bundle weight matched to destination crane capacity
- Each bundle labeled with heat number, steel grade (Gr.B / S355 / etc.), size, and coating specification for site identification
- FOB, CIF, and DDP terms available with professional documentation handling for customs clearance at destination port
Submit Specifications for Bulk Quotation
Send your size schedule, steel grade requirement, total tonnage, and destination port to receive a factory-direct quotation with volume pricing, typical production lead times, and mill test certificate confirmation. For non-standard dimensions or mixed-container orders combining square tube with other structural sections, our engineering team will provide a consolidated loading plan within one working day.
Frequently Asked Questions
Q: How do S235, S275, and S355 compare to Gr.B and STK400 across different standard systems?
A: These grades belong to three separate standard families — S235/S275/S355 follow EN 10025 and EN 10219 (European), Gr.B follows ASTM A500 (North American), and STK400 follows JIS G 3466 (Japanese). The numeric suffix in EN grades indicates minimum yield strength in MPa. [NEED_CITE: steel grade equivalence tables between EN ASTM and JIS structural steel standards] We supply all five grades from stock and can provide cross-reference documentation for project engineers verifying material substitution.
Q: What is the difference between hot dipped galvanized and pre-galvanized square tubes?
A: Hot dip galvanizing immerses the finished tube in molten zinc, creating a metallurgical bond with coating thickness typically exceeding 70 microns. Pre-galvanized tubes are made from already-coated coil, resulting in thinner zinc at the weld seam and cut edges. Hot dipped galvanizing provides superior edge coverage and longer corrosion resistance for outdoor structural applications.
Q: Can I order non-standard sizes or custom lengths?
A: Yes. Our standard range covers 19×19mm to 800×800mm with wall thickness 1–30mm. For dimensions outside this range or specific cut lengths, we accept custom orders with flexible MOQ starting from 1 ton. Typical production lead times apply for non-standard specifications.
Q: What certification documents are provided for EU customs clearance?
A: Every shipment includes original mill test certificates, and our CE marking per EN 10210 / EN 10219 satisfies EU structural steel regulations. Third-party inspection by SGS or BV is available before loading. Full export documentation including certificate of origin is prepared by our export team.
Q: How is invoicing calculated for galvanized square tubes?
A: We invoice by theoretical weight based on the specified dimensions and wall thickness, calculated per the standard formula for square hollow sections. This provides transparent pricing independent of actual weight variation within tolerance.
Request Your Factory-Direct Quotation Today
Submit your specification sheet — including size, wall thickness, steel grade, quantity, and destination port — to receive competitive bulk pricing with original mill test certificates and full export documentation.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
Website: www.sdxinjiyuan.com
