Description
Factory-direct galvanized tube supply — Q235B and Q345B grades rolled and hot-dip galvanized on our own 3 production lines, shipped with full ASTM documentation and no trading markup.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B Galvanized Square/Rectangular Steel Tube |
| Product Type | Galvanized Square and Rectangular Steel Tube |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400 |
| Standard | ASTM |
| Section Shape | Square / Rectangular |
| Wall Thickness | 0.5–200mm |
| Length | 12m (standard) |
| Technique | Hot Rolled / Cold Rolled |
| Surface Treatment | Galvanized (Zinc Coated) |
| Tolerance | ±1% |
| Ends | Plain |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Invoicing | By Theoretical Weight |
| Application | Steel structures, Construction frames, Machinery, Scaffolding, Furniture, Petrochemicals |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Facade | Glass curtain wall framing, architectural column cladding, roof truss systems |
| Infrastructure | Scaffolding tubes, bridge support frames, utility pole bases |
| Machinery Manufacturing | Conveyor structures, equipment base frames, hydraulic support columns |
| Petrochemicals | Pipe rack supports, platform grating frames, cable tray structures |
| Steel Structure Fabrication | Portal frames, mezzanine beams, warehouse column systems |
What Rounded Corners Cost You on a Galvanized Frame Order
Sharp-corner galvanized square and rectangular tubes eliminate on-site grinding and filler welding that rounded-corner profiles demand.
When a facade contractor receives standard rectangular tubes with R≥2t corners, the visible joints on a glass curtain wall frame never sit flush. The crew spends hours grinding and filling before the architect signs off. I watched a Middle East project reject an entire batch of rounded-corner galvanized tubes because the corner radius showed through the powder coating — the rework cost doubled the original material price. As a Customized Galvanized Square Rectangular Steel Tube supplier, we produce patented sharp-corner profiles that hold true 90-degree edges through the galvanizing bath, so the frame arrives on site ready to bolt. [NEED_CITE: dimensional tolerance requirements for cold-formed structural hollow sections]
Matching Galvanized Tubes to Corrosive and Structural Environments
Hot-dip galvanizing deposits a metallurgically bonded zinc-iron alloy layer that outperforms pre-galvanized coatings in continuous outdoor exposure. For a Customized Galvanized Square Rectangular Steel Tube supplier serving coastal infrastructure, the zinc coating must survive salt spray without flaking at cut edges or weld zones. Our Q345B grade tubes carry the higher yield strength needed for heavy-load scaffolding and bridge supports, while Q235B serves lighter furniture and interior framing where weight savings matter. The ±1% tolerance holds across wall thicknesses from 0.5mm thin-wall decorative sections to 200mm heavy structural profiles.
Engineering Compliance and Grade Selection for Load-Bearing Frames
Structural engineers specifying galvanized hollow sections must verify that the steel grade meets the project’s governing code — ASTM for North American jobs, EN 10219 for European specifiers, and GB/T 6728 for domestic Chinese projects. Q235B roughly corresponds to S235JR and ASTM A36 in yield behavior, while Q345B aligns with S355JR and ASTM A572 Gr.50 for higher-load applications. [NEED_CITE: steel grade equivalence tables between GB ASTM and EN standards] Choosing the wrong grade means either overpaying for unnecessary strength or failing structural inspection. Third-party inspection by SGS or BV confirms chemical composition and mechanical properties before the container is sealed, preventing customs rejection at destination ports.
Steel Grade, Galvanizing Process, and Wall Thickness Explained
The Q-series grades (Q195 through Q345B) follow the Chinese GB system where the number indicates minimum yield strength in MPa. Q235B delivers reliable formability for bending and punching services, making it the default choice for scaffolding and furniture frames. Q345B adds manganese and micro-alloying elements for higher strength in heavy construction without increasing section size. Hot-dip galvanizing immerses the formed tube in molten zinc at approximately 450°C, creating a coating thickness of 45–85μm that provides 20+ years of corrosion protection in rural atmospheres and 10–15 years in industrial coastal zones. [NEED_CITE: hot-dip galvanized coating thickness and corrosion protection lifespan data] Wall thickness tolerance at ±1% means a specified 5.0mm wall measures between 4.95mm and 5.05mm — tight enough for precision machinery frames yet compliant with ASTM dimensional standards. Invoicing by theoretical weight, calculated from outer dimensions and wall thickness, gives predictable cost control regardless of minor galvanizing coating variation.
Hidden Costs of Wrong Grade Selection and Missing Certificates
Ordering Q235B when the structural drawing calls for Q345B triggers a cascade: the engineer rejects the mill test certificate, the inspector halts installation, and the contractor faces delay penalties. Conversely, specifying Q345B for a light-duty furniture application wastes 20–30% on material cost with no structural benefit. Missing CE marking or incorrect EN standard references on the certificate block EU customs clearance entirely — the container sits at port accumulating demurrage charges while paperwork is corrected. [NEED_CITE: EU customs rejection rates for steel products missing CE documentation] A Customized Galvanized Square Rectangular Steel Tube supplier must provide heat-number traceability from raw coil to finished galvanized tube, so every piece on site matches its test certificate.
Why Project Buyers Source Galvanized Tubes from Our Jinan Mill
We roll and galvanize on our own 3 production lines covering 2,800+ specifications, so there is no trading company markup between the mill price and your purchase order. Our in-house physical and chemical laboratory tests every heat for composition and mechanical properties before galvanizing, and issues the mill test certificate with heat-number traceability. The patented sharp-corner rectangular tube technology — backed by 41 invention patents — produces true 90-degree edges that standard mills cannot achieve, critical for architectural facades and glass curtain walls. Full international certifications including ISO 9001:2015, Lloyd’s CE (EN 10210/10219), Singapore FPC, and SGS/BV verification cover exports to 50+ countries. Custom non-standard sizes, cutting, punching, and bending services are completed in-house, eliminating the need for secondary fabrication at destination. Professional container loading with anti-damage measures protects the galvanized coating during ocean transit.
Documentation & Compliance
- Mill test certificate documenting Q235B/Q345B chemical composition (C, Mn, Si, P, S) and yield/tensile strength per ASTM standards, traceable by heat number
- CE certificate per EN 10210/EN 10219 for hot-finished and cold-formed structural hollow sections, required for EU project compliance
- ISO 9001:2015 quality management system certificate covering the full production process from raw material incoming inspection to galvanized finished product
- SGS or BV third-party inspection report verifying dimensional tolerance, coating thickness, and surface quality before container sealing
- Material traceability tag on each bundle showing heat number, steel grade (Q235B/Q345B), size, and production date
- Complete customs export documents: commercial invoice, packing list, bill of lading, and certificate of origin for destination port clearance
Packaging, Loading & Delivery
- Q235B/Q345B galvanized square and rectangular tubes bundled with high-tensile steel strips and edge protectors to prevent zinc coating abrasion during handling
- Seaworthy packaging with waterproof paper wrapping and plastic caps on tube ends to block moisture ingress during ocean transit
- Container loading optimized for 12m standard length tubes, with wooden chocks and anti-slip mats to prevent shifting and corner damage in 20ft and 40ft containers
- Custom cutting to project-specified lengths available before galvanizing, reducing on-site waste and labor for scaffolding and frame assembly
- Heat number and steel grade (Q235B/Q345B) stenciled on each bundle for site identification and inspection traceability
- FOB Jinan/Qingdao, CIF destination port, or DDP door-to-door delivery terms available with full export documentation
Getting Your Galvanized Tube Quote and Mill Test Certificate
Send your drawing or specification sheet listing section shape, outer dimensions, wall thickness, steel grade (Q235B/Q345B), surface treatment, quantity, and destination port. We respond within 12 hours with unit pricing, MOQ confirmation, lead time, and shipping terms. Product samples and mill test certificates from recent Q235B/Q345B galvanized production runs are available for your quality review before contract signing.
Frequently Asked Questions
Q: What is the difference between Q235B and Q345B for galvanized square and rectangular tubes?
A: Q235B offers good formability and weldability for light to medium structural applications like scaffolding and furniture frames. Q345B provides higher yield strength for heavy-load construction, bridges, and machinery frames where reduced section size is needed. Both grades galvanize well with consistent zinc coating adhesion.
Q: Can you produce non-standard sizes for galvanized square and rectangular tubes?
A: Yes, custom non-standard dimensions are available beyond the standard size range. Our 3 production lines cover 2,800+ specifications with wall thicknesses up to 200mm. Low MOQ of 5 tons applies, and we provide cutting, bending, and punching services to your project requirements.
Q: What is the difference between hot-dip galvanized and pre-galvanized coating?
A: Hot-dip galvanizing immerses the formed tube in molten zinc, creating a metallurgically bonded coating of 45–85μm with superior corrosion resistance and edge protection. Pre-galvanized (electro-galvanized) applies a thinner zinc layer that is less durable in outdoor or corrosive environments. Hot-dip is specified for structural and outdoor applications.
Q: How does invoicing by theoretical weight affect my cost calculation?
A: Theoretical weight is calculated from the specified outer dimensions, wall thickness, and length using standard steel density. This gives predictable pricing regardless of minor variations in galvanizing coating thickness or mill tolerance. Actual weight may vary slightly, but theoretical weight invoicing simplifies budget control for project procurement.
Q: What certifications do you provide for EU customs clearance?
A: We supply CE marking per EN 10210 (hot-finished) and EN 10219 (cold-formed) standards, required for structural steel products entering the EU market. Complete mill test certificates, ISO 9001:2015 certification, and third-party inspection reports from SGS or BV are included. All documents are provided before shipment to prevent customs delays.
Request Your Galvanized Tube Specification Review
Submit your project dimensions, steel grade, and quantity to receive a detailed quotation with mill test certificate sample and production lead time.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxjypipe.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjypipe.com
