Description
Factory Direct Supply — Own steel mill and fabrication workshop under one quality system, delivering Q235B Q355B hot dip galvanized flat steel with full material traceability from raw slab to finished bar.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q355B Hot Dip Galvanized Flat Steel |
| Product Type | Galvanized Flat Steel Bar |
| Steel Grade | Q235A, Q235B, Q355B |
| Standard | GB, EN, ASTM, AISI, JIS G3302 |
| Section Shape | Flat Bar |
| Width | 45mm–2200mm |
| Thickness | 0.15mm–6.00mm |
| Length | 6m–12m (or customized) |
| Technique | Hot Rolled Based |
| Surface Treatment | Hot Dip Galvanized (Z121–Z180) / Electro-Galvanized |
| Spangle Type | Zero Spangle |
| Skin Pass | Yes |
| Oiled or Non-oiled | Non-oiled |
| Tolerance | ±1% |
| Hardness | Hard |
| Processing Service | Decoiling, Bending, Cutting, Punching, Welding |
| Application | Construction and structural support / Industrial manufacturing / General fabrication and hardware / Scaffolding / Framing and brackets |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Structural Support | Framing members, connecting plates, bracket assemblies, scaffolding uprights and ledgers |
| Industrial Manufacturing | Machinery base frames, equipment guards, stiffening ribs for fabricated enclosures |
| General Fabrication & Hardware | Custom brackets, strapping, hinges, reinforcement plates for welded assemblies |
Where Coating Thickness Variance Becomes a Site Rejection
Z121–Z180 hot dip galvanized coating must hold uniform thickness across the full width — or the flat bar fails acceptance before it ever gets welded.
When buyers source galvanized flat stock through traders, the zinc coating is often the first variable to slip. I have seen shipments arrive with Z80 material labeled as Z180 — the buyer only discovered it when the local inspector flagged the coating weight on the first bundle. Re-galvanizing on-site costs more than the original material, and the project schedule absorbs the delay. With Q235B Q355B hot dip galvanized flat steel produced under a vertically integrated system, the coating line sits within the same facility that rolls the base metal, so every heat number traces back to one mill test certificate. [NEED_CITE: hot dip galvanizing coating thickness standards per ASTM A123]
Matching Flat Bar Geometry to Structural Connection Details
Flat bars in Q235B and Q355B grades serve as connection plates, bracket stiffeners, and framing members where precise width and thickness matter for bolt-hole alignment and weld fit-up. The ±1% tolerance combined with skin-pass treatment keeps the bars flat enough for CNC punching without spring-back distortion. For scaffolding and industrial framing, the zero spangle hot dip galvanized finish provides consistent corrosion resistance across humid or coastal job sites — and because our fabrication workshop handles custom cutting, bending, and punching in-house, the flat bars arrive at the site ready to install rather than requiring secondary processing.
Engineering Compliance Across International Standards
Structural flat bars used in load-bearing frames must conform to the mechanical and chemical requirements of the governing code — whether that is EN 10025 for European projects, ASTM A36 for North American specifications, or GB/T 700 for domestic Chinese construction. Q235B Q355B hot dip galvanized flat steel supplied under multiple standard designations allows project engineers to specify the grade that matches their local code while sourcing from a single mill. Third-party inspection by SGS, BV, or TUV verifies both the base metal chemistry and the galvanized coating weight before shipment, which satisfies the documentation requirements for CE-marked structural components entering the EU market. [NEED_CITE: EN 1090 execution class requirements for structural steel components]
Steel Grade Selection and Galvanizing Process Fundamentals
Q235A, Q235B, and Q355B represent the most widely specified carbon structural grades in the Chinese steel system. Q235B offers reliable weldability and formability for general fabrication, while Q355B provides higher yield strength for applications where weight optimization or heavier loading matters. The hot dip galvanizing process immerses the rolled flat bar in a molten zinc bath, metallurgically bonding the zinc to the steel surface — this produces a coating that resists mechanical damage better than electro-galvanized alternatives. The Z121–Z180 coating range covers environments from indoor industrial framing (Z121) to outdoor structural exposure in humid or mildly corrosive atmospheres (Z180). Zero spangle finish eliminates the visible crystalline pattern, giving a uniform matte appearance preferred in architectural and exposed structural applications.
The Hidden Cost of Unverified Coating and Tolerance
Ordering galvanized flat bars without verified coating weight or dimensional tolerance creates downstream risk that rarely shows up in the purchase price. A bar that measures below minimum thickness due to excessive negative tolerance reduces the load-bearing cross-section — a problem that passes visual inspection but fails structural calculation review. Similarly, a zinc coating below the specified Z-value corrodes faster than the design life predicts, leading to premature maintenance or replacement. Material certification gaps compound the issue: when the mill test certificate does not trace to a specific heat number, customs authorities in strict-markets may hold the shipment for additional testing, delaying the entire project timeline. [NEED_CITE: material traceability requirements under EN 10204 inspection documents]
Why Project Buyers Source Directly from an Integrated Mill
Q235B Q355B hot dip galvanized flat steel flows from our own steel production facility through our dedicated galvanizing line and fabrication workshop — one material stream, one quality system, one point of accountability. The mill maintains its own理化 laboratory for chemical composition and mechanical testing, issuing mill test certificates with full heat number traceability for every shipment. With over 2,800 specifications in raw material inventory, we can fulfill mixed-size orders without waiting for third-party procurement. Certified welding procedures and qualified welders handle any fabrication processing — cutting, bending, punching, welding — to project-specific drawings. Complete quality documentation packages include WPS, PQR, dimensional inspection reports, and coating thickness measurements, satisfying the requirements of international general contractors and EPC firms across the EU, Middle East, Southeast Asia, and Africa.
Documentation & Compliance
- Mill test certificate documenting Q235B/Q355B chemical composition and mechanical properties per GB/T 700, with full heat number traceability from our own steel mill
- Third-party inspection report from SGS, BV, or TUV verifying hot dip galvanized coating weight (Z121–Z180) and dimensional tolerance per project specification
- ISO 9001 quality management system certificate covering the integrated production process from hot rolling through galvanizing and fabrication
- CE compliance documentation for structural steel components entering the European market, including Declaration of Performance per EN 1090
- Material traceability records linking each bundle to its original heat number, rolling schedule, and galvanizing batch
- Complete export documentation package: commercial invoice, packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Galvanized flat bars bundled with steel strips and edge protectors to preserve the zero spangle zinc coating during ocean transit and handling
- Seaworthy packaging with waterproof wrapping for 6m–12m lengths, optimized for 20ft and 40ft container loading with weight distribution calculated per bundle
- Custom cutting to project-specified lengths available before shipment, reducing on-site waste and secondary cutting labor
- Each bundle marked with heat number, steel grade (Q235B/Q355B), dimensions, and coating class for immediate site identification and traceability
- FOB, CIF, and DDP shipping terms available with professional oversized cargo loading plans and complete export documentation tracking to final destination
Starting Your Procurement Process
Share your project drawings, steel grade requirements, coating specification, and target quantity to receive a detailed quotation including material, fabrication, coating, packing, and shipping costs. Our engineering team reviews your specifications and responds within 24 hours with a preliminary assessment and shop drawing timeline. Confirm your required standards, third-party inspection preferences, and destination port to finalize the delivery schedule.
Request a Quotation with Mill Test Certificate
Submit your flat bar specifications, steel grade, coating class, and quantity to receive pricing and complete material documentation.
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
