Description
Factory-Direct ERW Tubes — Q235 Q345 galvanized square rectangular steel tube produced in-house with full mill test traceability, no broker markup.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 Q345 Galvanized Square and Rectangular Steel Tube |
| Product Type | Galvanized Square and Rectangular Steel Tube (ERW Welded) |
| Steel Grade | Q195, Q235, Q355 (also covers S235JR, S275JR, S355JR, SS400, ASTM A36) |
| Standard | GB/T 6728, ASTM A500, EN 10219, EN 10210, JIS G3466 |
| Section Shape | Square / Rectangular |
| Size Range | 20 mm – 500 mm (side length / outer diameter) |
| Wall Thickness | 1 mm – 30 mm |
| Length | 5.8 m – 12 m (6 m, 6.4 m, 12 m available) |
| Technique | ERW (Electric Resistance Welded) / Hot Rolled / Cold Rolled |
| Surface Treatment | Hot Dip Galvanized (30 g – 275 g/m²), ZAM coating, PVC coating, Black painting, Anti-rust oil |
| Ends | With or without end caps |
| Application | Steel structures, construction frames, scaffolding, machinery, furniture, fencing, greenhouse structures |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, column supports, beam bracing, pedestrian bridge railings |
| Scaffolding & Access | Scaffold uprights, ledger tubes, putlog tubes for high-rise and facade work |
| Machinery & Equipment | Machine bases, conveyor frames, hydraulic support columns, agricultural equipment chassis |
| Fencing & Enclosure | Perimeter fencing posts, security barrier uprights, animal pen frames |
| Greenhouse & Agriculture | Greenhouse skeleton tubes, irrigation support frames, shade structure posts |
How Zinc Coating Weight Decides Field Service Life for Q235 Q345 Galvanized Square Rectangular Steel Tube
Heavier zinc coating directly extends corrosion resistance in humid and coastal environments.
Procurement teams often see “galvanized tube” on a quote and assume all coatings perform equally. In reality, a 30 g/m² electroplated coating will flash-rust within months in tropical humidity, while a 275 g/m² hot-dip coating can withstand decades of outdoor exposure. Missing mill test certificates make it impossible to verify actual zinc weight against the purchase order. Negative tolerance on wall thickness compounds the problem — a tube that measures 1.8 mm instead of the specified 2.0 mm loses both structural margin and corrosion allowance simultaneously. [NEED_CITE: hot dip galvanized coating thickness standards for structural steel]
Matching Wall Thickness and Section Size to Structural Load Paths
When engineers specify Q235 Q345 galvanized square rectangular steel tube for building frames or scaffolding uprights, the critical variables are section modulus and load-bearing capacity relative to wall thickness. A 100 × 100 mm square tube at 4 mm wall thickness carries significantly different bending moments than the same outer dimension at 2 mm. Our ERW welding process ensures uniform seam quality across the full 1 mm – 30 mm thickness range, and we supply side lengths from 20 mm to 500 mm to match structural node spacing without on-site cutting waste.
Engineering Compliance and Surface Protection for Corrosive Environments
Structural frames in petrochemical plants, coastal boardwalks, or wastewater treatment facilities face chloride attack that demands both adequate zinc coating weight and proper steel grade selection. Q355 / S355JR grades provide higher yield strength for heavy-load columns, while Q235 / S235JR suffices for non-critical bracing and fencing. EN 10219 cold-formed hollow sections and ASTM A500 structural tubing carry different dimensional tolerance requirements — getting the standard wrong means customs rejection or failed third-party inspection. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed structural hollow sections] We supply CE-certified products meeting EN 10210 and EN 10219 for European projects, and ASTM A500 for North American destinations, with mill test certificates documenting chemical composition and mechanical properties per the relevant standard.
Understanding Steel Grade Equivalence and ERW Welding Quality
Q195, Q235, and Q355 belong to the Chinese GB/T 1591 system, mapping internationally to S235JR, S275JR, S355JR (EN 10025), SS400 (JIS G3101), and ASTM A36 / A500 Grade B. The yield strength hierarchy matters: Q355 delivers roughly 50 percent higher yield than Q235, allowing thinner walls for the same load — reducing weight and material cost per meter. ERW welding produces a longitudinal seam through electric resistance heating without filler metal, creating a cost-effective solution for structural and low-to-medium pressure applications. Hot dip galvanizing at 30 – 275 g/m² provides sacrificial zinc protection; ZAM coating offers superior cut-edge corrosion resistance for harsh environments; PVC coating adds chemical resistance for industrial washdown areas. Wall thickness tolerance directly affects theoretical weight calculations — a consistent negative tolerance of 0.1 mm on a 3 mm wall tube reduces actual weight by over 3 percent, impacting both structural safety margins and per-ton pricing fairness. [NEED_CITE: steel grade equivalence between EN and ASTM standards]
The Hidden Cost of Unverified Zinc Coating and Missing Certificates
Ordering galvanized square and rectangular tubes without verified coating weight or original mill test certificates creates compounding risks. Under-coated tubes fail field inspection when SGS or BV measures zinc thickness below specification, triggering full-container rejection and return freight costs that exceed the original material value. Missing heat number traceability means the buyer cannot prove material origin during structural audits, jeopardizing project handover. Negative tolerance abuse — where actual wall thickness falls below the ordered specification — reduces load capacity and violates EN 10219 or ASTM A500 dimensional requirements, potentially voiding engineering insurance coverage. [NEED_CITE: consequences of substandard galvanized coating on structural steel service life]
Why Project Procurement Teams Source Q235 Q345 Galvanized Square Rectangular Steel Tube Through XJY Plate
We operate our own ERW welding lines and hot dip galvanizing facilities, eliminating broker margins and enabling direct quality control from raw coil to finished tube. Every bundle ships with an original mill test certificate documenting chemical composition, yield strength, tensile strength, elongation, and zinc coating weight — verifiable by heat number. Our in-house理化实验室 tests every production batch before release; I personally inspect zinc coating thickness on outbound galvanized tubes because I learned the hard way that a 20-micron shortfall on a Dubai order cost us thousands in return freight. We stock over 2,800 specifications across Q195, Q235, and Q355 grades in side lengths from 20 mm to 500 mm and wall thicknesses from 1 mm to 30 mm, enabling single-source procurement for mixed-specification project orders. Custom cutting, punching, and bending services reduce on-site labor and waste. CE certification under EN 10210 and EN 10219, ISO 9001:2015 quality management, and SGS/BV third-party inspection availability satisfy European, Middle Eastern, and African import requirements. Professional flatbed and open-top container loading prevents zinc coating damage during transit — we use edge protectors and proper dunnage to preserve surface integrity across ocean freight.
Documentation & Compliance
- Mill test certificate documenting Q235/Q355 chemical composition, yield strength, and zinc coating weight per GB/T 6728 or EN 10219
- CE certificate confirming compliance with EN 10210 (hot-finished) or EN 10219 (cold-formed) structural hollow sections
- ISO 9001:2015 quality management system certificate covering ERW welding and galvanizing processes
- SGS or BV third-party inspection report verifying dimensional tolerance, zinc coating thickness, and mechanical properties
- Full material traceability by heat number linking each tube to its original coil and galvanizing batch
- Export customs documentation including packing list, bill of lading, and certificate of origin for destination-country clearance
Packaging, Loading & Delivery
- Hot dip galvanized Q235 Q345 galvanized square rectangular steel tube bundled with steel strips and edge protectors to preserve zinc coating during ocean transit
- Surface protection via anti-rust oil or end caps on cut-to-length tubes to prevent moisture ingress at open ends during storage
- Container loading optimized for 5.8 m and 6 m lengths in 20ft and 40ft open-top containers, with 12 m tubes shipped on flatbed or break-bulk vessels
- Custom cutting to project-specific lengths within the 5.8 m – 12 m range, reducing on-site welding and scrap
- Heat number and steel grade stenciled on each tube for site traceability and inspection verification
- FOB, CIF, and DDP shipping terms available with door-to-door logistics for construction sites and fabrication yards
Requesting a Project-Specific Quotation for Q235 Q345 Galvanized Square Rectangular Steel Tube
Submit your required steel grade, section dimensions, wall thickness, length, quantity, and destination port — we return a detailed quotation with material cost, processing fees, and shipping terms within 12 hours. We provide original mill test certificates before shipment for your quality verification, and third-party inspection via SGS or BV can be arranged upon request. For non-standard dimensions or mixed-specification project orders, our engineering team reviews your drawings and proposes optimized cutting plans.
Frequently Asked Questions
Q: How do Q235, Q345, and Q355 steel grades map to European EN and American ASTM standards?
A: Q235 corresponds to S235JR (EN 10025) and ASTM A36; Q355 (formerly Q345) maps to S355JR and ASTM A500 Grade B. We supply mill test certificates documenting chemical composition and mechanical properties per your specified standard, ensuring compliance with EN 10219, ASTM A500, or GB/T 6728 as required by your project.
Q: What is the difference between 30 g/m², 120 g/m², and 275 g/m² galvanized zinc coating?
A: Zinc coating weight determines corrosion resistance and service life. Light coatings around 30 g/m² suit indoor or dry environments; 120 g/m² handles moderate outdoor exposure; 275 g/m² hot dip galvanizing provides long-term protection for coastal, industrial, or high-humidity applications. We supply all three options and verify coating weight on every outbound bundle.
Q: Can I verify the mill test certificate and heat number traceability before shipment?
A: Yes. We provide original mill test certificates documenting chemical composition, mechanical properties, and zinc coating weight before or with shipment. Each certificate references a specific heat number traceable to the original steel coil and galvanizing batch. Third-party inspection via SGS or BV is available upon request.
Q: Do you supply cut-to-length tubes or small quantities without full-bundle minimums?
A: We offer custom cutting to project-specific lengths within the 5.8 m – 12 m range, along with punching, bending, and welding preparation services. Small-lot and mixed-specification orders are accepted for project procurement — contact us with your bill of materials for a tailored quotation.
Q: How are heavy galvanized tubes loaded to prevent zinc coating damage?
A: We use steel strip bundling with edge protectors, proper dunnage placement, and open-top or flatbed container loading for long-length tubes. Our logistics team plans container weight distribution to avoid overweight penalties and ensures zinc coating integrity throughout ocean transit.
Secure Your Q235 Q345 Galvanized Square Rectangular Steel Tube Supply with Verified Mill Test Certificates
Send your specifications — steel grade, section size, wall thickness, length, quantity, and destination port — and receive a detailed quotation with original mill test certificate preview within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjyplate.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjyplate.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
