Description
Factory-Direct Galvanized Tube Supply — Q195, Q235, and Q345 hot dipped galvanized square and rectangular tubes produced on our own ERW lines with zinc coating applied in-house, no trading markup added.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q195 / Q235 / Q345 Hot Dipped Galvanized Square & Rectangular Steel Tube |
| Product Type | Galvanized Square and Rectangular Steel Tube (SHS / RHS) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, 10#, 20#, 45#, 16Mn, ASTM A53 Grade A/B, St37, St42, St35.4, St52.4 |
| Standard | BS EN, GB, AISI, ASTM, DIN, JIS, ISO 9001 |
| Section Shape | Square / Rectangular |
| Size Range | 10 mm – 1000 mm |
| Wall Thickness | 0.6 mm – 28 mm |
| Length | 1 m – 12 m |
| Technique | Hot Rolled / Cold Rolled / ERW |
| Surface Treatment | Hot Dipped Galvanized (Zinc Coating 30 – 275 g/m²); Bare, Oiled, Color Paint, 3PE available |
| Ends | Plain / Beveled / Threaded with couplings or sockets; plastic caps and steel rings available |
| Application | Structural frames, construction, industrial equipment, agricultural structures, bridge and highway components, sign posts, machinery frames |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building structural frames, bridge handrails, highway guardrail posts, warehouse skeleton columns |
| Industrial Equipment | Machine guard frames, conveyor support structures, equipment base platforms |
| Agricultural & Outdoor | Greenhouse framing, fencing posts, irrigation support structures, sign post foundations |
| Manufacturing & Fabrication | Trailer chassis members, steel furniture frames, solar panel mounting structures |
| Shipbuilding & Marine | Deck handrail posts, non-structural interior framing, cable tray supports |
Where Zinc Coating Weight Determines Whether Your Structure Survives the First Five Years
Hot dipped galvanizing at 275 g/m² delivers roughly 30 years of corrosion protection in rural atmospheres — while 30 g/m² may fail within three years in coastal or industrial zones.
I have watched project teams specify galvanized tubes without checking the actual coating weight on the mill test certificate. The purchase order says “galvanized,” the invoice says “galvanized,” but the zinc layer arriving on site measures 45 microns when the specification calls for 70 minimum. The third-party inspector flags it. Half the shipment gets rejected. Replacement material has to be air-freighted at triple the original freight cost, and the project timeline absorbs a delay nobody budgeted for. This is not a rare failure mode — it happens routinely when buyers accept supplier declarations without demanding coating weight documentation tied to heat numbers [NEED_CITE: hot dip galvanizing coating thickness standards per ASTM A123 and EN ISO 1461].
A Hot Dipped Galvanized Square and Rectangular Steel Tube Supplier who controls the galvanizing bath in-house can guarantee coating weight per batch. A trading middleman cannot.
Matching Wall Thickness and Dimension to Structural Load Requirements
Hot Dipped Galvanized Square and Rectangular Steel Tube selections for structural frames must balance load-bearing capacity against corrosion environment severity. A warehouse column in an inland dry climate may perform adequately with Q235 at 3 mm wall thickness and 60 g/m² zinc. The same column in a coastal port facility requires Q345 for higher yield strength and 275 g/m² zinc to resist salt-laden air. Our production lines cover the full 0.6–28 mm wall thickness range across 10–1000 mm side lengths, meaning a single order can supply both the light-gauge purlins and the heavy structural columns without splitting the procurement across multiple vendors.
Engineering Compliance and Certification for Cross-Border Delivery
Structural hollow sections exported to European markets must conform to EN 10210 (hot-finished) or EN 10219 (cold-formed) standards, and customs authorities in EU member states routinely request CE marking documentation before releasing construction-grade steel [NEED_CITE: CE marking requirements for structural steel under EN 10210 and EN 10219]. North American buyers typically require ASTM A500 or A53 compliance with mill test certificates showing chemical composition and mechanical properties. Our Hot Dipped Galvanized Square and Rectangular Steel Tube production carries CE certification under both EN 10210 and EN 10219, ISO 9001:2015 quality management registration, and every shipment includes original mill test certificates traceable to heat number — eliminating the documentation gaps that cause customs holds and project compliance failures.
Steel Grade Selection and ERW Welding Process Fundamentals
The Q-series grades (Q195, Q235, Q345) follow the Chinese GB standard system where the number indicates minimum yield strength in MPa. Q235 maps approximately to S235JR under EN standards and ASTM A283 Grade C under US specifications, while Q345 corresponds roughly to S355JR and ASTM A572 Grade 50 [NEED_CITE: steel grade equivalence mapping between GB, EN, and ASTM standards for structural hollow sections]. For procurement teams sourcing across multiple project regions, specifying Q235B or Q345B allows a single material to satisfy Chinese, European, and American structural codes simultaneously.
ERW (Electric Resistance Welding) is the dominant forming method for square and rectangular tubes in the 10–400 mm size range. The process forms a flat steel strip into the target cross-section and fuses the seam through high-frequency electrical current — producing a weld zone that, when properly executed, is fully consumed by the subsequent hot dip galvanizing bath. This means the zinc coating covers the weld seam as thoroughly as the parent metal, eliminating the bare-weld corrosion points that plague poorly welded tubes. Our three production lines run ERW forming, welding, and hot dip galvanizing as a continuous sequence, so every tube leaving the facility has passed through all three stages under controlled parameters.
The hot dip galvanizing process itself involves immersing the formed and welded tube in a molten zinc bath at approximately 450°C. The zinc coating weight — specified here from 30 to 275 g/m² — directly determines service life in corrosive environments. Lighter coatings suit indoor or sheltered applications; heavier coatings are essential for outdoor, coastal, or industrial atmosphere exposure.
Hidden Costs of Procuring Without Verified Coating and Certification
Accepting a lower zinc coating than specified does not show up at delivery — the tube looks galvanized either way. The failure surfaces months later when rust bleeds through at weld seams or at cut edges, triggering warranty claims and structural remediation costs that dwarf the original material savings. Similarly, shipping without proper CE documentation or without heat-number-traceable mill test certificates can result in customs detention, project work stoppages, and re-inspection fees charged to the buyer [NEED_CITE: consequences of missing CE documentation for structural steel imports into EU markets]. These are not theoretical risks. They are the standard failure pattern when buyers prioritize unit price over verification infrastructure.
Procurement Advantages of Direct Factory Supply
Purchasing a Hot Dipped Galvanized Square and Rectangular Steel Tube from the producing factory eliminates the markup layers that accumulate when material passes through trading intermediaries. Our facility in Jinan operates three simultaneous production lines with monthly capacity exceeding 20,000 tons, maintaining ready stock across 2,800+ standard specifications for immediate dispatch while custom orders in non-standard dimensions complete within typical production lead times. Every batch is tested in our in-house laboratory, and original mill test certificates accompany each shipment — no photocopies, no reissued documents. Third-party inspection through SGS or BV can be arranged before container loading at buyer request. For long-term procurement partners, volume-based discount programs and consolidated multi-product container loading reduce per-unit landed costs further. Professional export documentation handling covers customs clearance requirements for destination markets across 50+ countries.
Documentation & Compliance
- Mill test certificate documenting Q235B or Q345B chemical composition and mechanical properties per GB/T 6728, traceable to heat number
- CE certificate conforming to EN 10210 (hot-finished) and EN 10219 (cold-formed) for European market structural compliance
- ISO 9001:2015 quality management system certificate covering full production and inspection workflow
- SGS or BV third-party inspection report available upon request, covering coating thickness, dimensional tolerance, and visual examination
- Material traceability documentation linking each bundle to heat number, production date, and galvanizing bath record
- Complete customs document package including packing list, bill of lading, and certificate of origin for destination-country clearance
Packaging, Loading & Delivery
- Hot dipped galvanized Q235 and Q345 tubes bundled with steel strips and edge protectors to preserve zinc coating integrity during ocean transit
- Each bundle tagged with heat number, steel grade, dimension, and coating weight for site identification and traceability
- Container loading plans optimized for 6 m and 12 m standard lengths to maximize weight utilization within 20ft and 40ft containers
- Custom cut-to-length service available for 1–12 m requirements, with cut ends sealed to prevent zinc edge peeling
- Plastic end caps fitted on all threaded or beveled-end tubes to protect threads and prevent moisture ingress during storage
- FOB, CIF, and DDP shipping terms available with professional export team handling port coordination and door-to-door logistics
Submit Specifications for Factory-Direct Quotation
Provide your required steel grade (Q195, Q235, Q345), cross-section dimensions, wall thickness, length, zinc coating weight, and destination port — our team responds within 12 hours with bulk pricing, mill test certificate confirmation, and production lead time. Non-standard dimensions and custom coating requirements are quoted separately with technical feasibility confirmation.
Request Your Hot Dipped Galvanized Tube Quote with Mill Test Certificate
Send specifications via email to admin@sdxinjiyuan.com or contact directly at +86 188 5315 7756 (WhatsApp/WeChat available).
Frequently Asked Questions
Q: How do Q235 and Q345 steel grades compare to ASTM and EN equivalents?
A: Q235B corresponds approximately to S235JR under EN 10219 and ASTM A283 Grade C under US standards. Q345B maps roughly to S355JR under EN and ASTM A572 Grade 50. We supply mill test certificates showing actual chemical composition and mechanical properties so your engineering team can verify compliance with your local structural code.
Q: What zinc coating weight should I specify for my project environment?
A: For indoor or sheltered applications, 30–60 g/m² provides adequate protection. For general outdoor exposure, 60–120 g/m² is standard. For coastal, industrial, or high-humidity environments, 200–275 g/m² is recommended to achieve multi-decade corrosion resistance. We produce all coating weights within this range and document actual measurements on the mill test certificate.
Q: Can I order non-standard dimensions outside your catalog sizes?
A: Yes. Our ERW production lines cover 10–1000 mm side lengths and 0.6–28 mm wall thickness with custom lengths up to 12 m. Non-standard specifications are quoted with confirmed production lead times. Minimum order quantity is 1 ton for both standard and custom dimensions.
Q: What documents are included with each shipment?
A: Every shipment includes original mill test certificates traceable to heat number, packing list, bill of lading, and certificate of origin. CE certification under EN 10210/EN 10219 is provided for European market compliance. SGS or BV third-party inspection reports can be arranged before loading at buyer request.
Q: How do you optimize container loading for mixed-size orders?
A: Our export team prepares container loading plans that nest smaller-section tubes inside larger sections where dimensionally feasible, maximizing weight utilization per container. This reduces per-ton freight costs for orders combining multiple specifications. Loading plans are shared with the buyer for approval before sealing.
