Description
Direct mill supply for right-angle structural tubes — Q235B and Q345B sharp corner square and rectangular steel tubes rolled to ±1% tolerance, shipped with original heat-number traceable mill test certificates.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B Sharp Corner Square & Rectangular Steel Tube |
| Product Type | Special-Shaped ERW Tube (Sharp Corner / Right-Angle) |
| Steel Grade | Q235B, Q345B |
| Standard | GB; equivalents EN10219 / ASTM A500 / JIS G3466 available upon request |
| Section Shape | Square / Rectangular (Sharp Corner / Right-Angle) |
| Size Range (Width) | 150–625 mm |
| Length | 5–15 m (standard 5.8 m / 6 m / 12 m) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / HDG (Hot-Dip Galvanized) |
| Tolerance | ±1% |
| Processing Service | Cutting, Bending, Welding, Punching, Decoiling |
| Invoicing | By Theoretical Weight |
| Application | Construction building / Structural frames / Machinery / Steel fabrication |
| Origin | China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Building frames, column-to-beam nodes, curtain wall support structures |
| Steel Fabrication | Welded structural frames, base plates, connection brackets for EPC projects |
| Machinery | Equipment bases, conveyor frames, machine guards requiring right-angle geometry |
| Infrastructure | Bridge walkway supports, solar mounting structures, industrial platform framing |
What Sharp Corner Tolerance Costs on a Structural Frame Order
A 2 mm corner-radius deviation can force on-site grinding across hundreds of nodes.
When fabricators receive rounded-corner hollow sections for connections designed around sharp 90-degree joints, the mismatch surfaces require field grinding or filler plates before bolting can proceed. On a mid-rise steel frame, this adds days of labor and introduces quality-control variables that inspectors flag. The Q235B Q345B sharp corner square rectangular steel tube supplier you choose must guarantee right-angle geometry within ±1% — otherwise your erection sequence stalls at every beam-column intersection. Missing or unverifiable mill test certificates compound the problem: without heat-number traceability, the entire batch faces rejection at customs or during third-party inspection at the port [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements].
How Right-Angle Geometry Matches Tight Structural Nodes
Sharp corner square and rectangular tubes eliminate the gap between standard rounded-corner RHS profiles and the 90-degree connection plates specified in structural drawings. For steel fabricators building column-to-beam moment connections or base-plate assemblies, this means full bearing contact without field modification. Our ERW forming process produces consistent right-angle corners across the full 150–625 mm width range in both Q235B and Q345B grades, with hot-rolled or HDG surface options depending on whether the tubes serve indoor frames or outdoor corrosive environments. Each Q235B Q345B sharp corner square rectangular steel tube ships with dimensional reports confirming corner radius and flatness — critical for projects where weld prep and bolt-hole alignment depend on predictable geometry.
Engineering Compliance and Surface Treatment Selection
Structural frames in seismic zones or high-wind regions require verified yield strength and documented chemical composition per the governing code — whether that is GB for domestic Chinese projects, EN10219 for European exports, or ASTM A500 for North American specification. Q235B corresponds broadly to S235JR and ASTM A36, while Q345B aligns with S355JR and ASTM A572 Gr. 50 in general structural applications [NEED_CITE: steel grade equivalence between GB, EN, and ASTM standards for structural hollow sections]. For outdoor or marine-adjacent structures, HDG galvanizing provides decades of corrosion protection without maintenance, while hot-rolled black finish suits indoor, painted, or fire-protected frames. CE certification under EN10219 is mandatory for European customs clearance, and third-party inspection by SGS or BV before shipment satisfies most EPC contractor quality plans.
Steel Grade and ERW Process Fundamentals
Q235B and Q345B represent the two most widely specified carbon structural grades in Chinese steel construction. Q235B offers adequate strength for non-critical framing, bracing, and secondary structures, while Q345B provides higher yield capacity for primary load-bearing members, long-span beams, and heavy equipment bases. The ERW welding process produces a continuous longitudinal weld seam with consistent mechanical properties across the tube profile — making it suitable for structural applications where seamless tubes would add cost without performance benefit. Sharp corner forming requires specialized roll-pass design to achieve true 90-degree internal angles without excessive thinning at the corner radii, which is why tolerance control and mill test certificate verification matter more for right-angle tubes than for standard rounded RHS. HDG coating after forming ensures full zinc coverage including the weld seam and corner zones, providing uniform corrosion resistance across the entire cross-section.
Hidden Costs of Unverified Sharp Corner Tube Procurement
Ordering sharp corner tubes without confirmed dimensional tolerance reports risks receiving products with oversized corner radii that fail to seat properly against connection plates — forcing rework or structural redesign after delivery. Missing mill test certificates mean the steel grade cannot be verified, creating liability exposure if the structure fails inspection or if customs authorities demand proof of compliance with EN10219 or ASTM A500 standards. Negative tolerance abuse — where actual wall thickness falls below the ordered specification — reduces load capacity and may violate engineering codes, yet remains invisible without ultrasonic measurement or independent inspection [NEED_CITE: structural hollow section tolerance standards and compliance verification]. The cost of replacing rejected tubes on-site, combined with project delays and re-inspection fees, typically exceeds any initial price savings from unverified suppliers.
Why Project Procurement Teams Source Sharp Corner Tubes Through XJY Plate
Every Q235B Q345B sharp corner square rectangular steel tube we supply rolls from dedicated sharp-corner forming mills with verified roll-pass tooling — not converted rounded-corner lines that produce inconsistent right angles. Our in-house quality lab issues original mill test certificates showing heat number, chemical composition, and mechanical properties for every batch, with full traceability from coil to finished tube. We maintain ready stock across the 150–625 mm width range in both hot-rolled and HDG finish, eliminating the 8–12 week mill lead times that delay project schedules. Custom cutting to project-specified lengths, bending to drawing angles, and punch-hole patterns reduce fabricator shop-floor processing and lower total installed cost. Professional heavy-cargo loading using flatbed trailers and open-top containers prevents corner damage during transit — a critical detail for sharp corner tubes where edge protection differs from standard RHS handling. ISO 9001:2015 certification and CE marking under EN10219 ensure compliance for European and international projects, while SGS or BV third-party inspection is available before shipment for EPC contractor quality requirements.
Documentation & Compliance
- Mill test certificate documenting Q235B or Q345B chemical composition and mechanical properties per GB standard, with heat number traceability to the original coil
- CE certificate confirming compliance with EN10219 for cold-formed structural hollow sections, required for European Union customs clearance
- ISO 9001:2015 quality management system certificate covering the full production and inspection process
- SGS or BV third-party inspection report available upon request, covering dimensional verification, surface coating thickness, and visual weld seam inspection
- Material traceability documentation linking each tube bundle to its heat number, production date, and mill test certificate
- Export customs documents including packing list, bill of lading, and certificate of origin for import clearance at destination port
Packaging, Loading & Delivery
- Sharp corner Q235B Q345B tubes bundled with high-tensile steel strips and edge protectors to preserve right-angle geometry and HDG zinc coating during ocean transit
- HDG galvanized tubes wrapped with waterproof cloth and separated by rubber spacers to prevent zinc surface scratching and white rust formation
- Standard 5.8 m, 6 m, and 12 m lengths optimized for 20ft and 40ft open-top container loading, with weight distribution calculated to avoid overweight penalties
- Custom cut-to-length service available for 5–15 m requirements, with cut ends deburred and protected against corrosion
- Each bundle labeled with heat number, steel grade (Q235B or Q345B), section dimensions, and length for site identification and traceability
- FOB, CIF, and DDP shipping terms available, with professional flatbed and break-bulk logistics for project cargo exceeding container capacity
Start Your Sharp Corner Tube Procurement
Submit your section dimensions, steel grade (Q235B or Q345B), surface treatment preference, quantity, and destination port to receive a detailed quotation with mill test certificate samples and shipping terms within 12 hours. For non-standard sizes or custom processing requirements including bending and punching, share your fabrication drawings for engineering review and lead-time confirmation.
Request Quotation and Mill Test Certificates
Send your Q235B Q345B sharp corner square rectangular steel tube specifications to receive pricing, MTC samples, and delivery schedules.
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjyplate.com
Frequently Asked Questions
Q: What is the difference between Q235B and Q345B for sharp corner structural tubes?
A: Q235B is a general-purpose carbon structural grade suitable for secondary framing, bracing, and non-critical load-bearing applications. Q345B offers higher yield strength for primary structural members, long-span beams, and heavy equipment bases where load capacity is critical. Both grades are available in sharp corner square and rectangular sections from 150–625 mm width.
Q: Can you provide mill test certificates for European or North American projects?
A: Yes. Every shipment includes original mill test certificates showing chemical composition and mechanical properties per GB standard. For European projects, we supply CE-certified tubes under EN10219. For North American specifications, equivalent grading to ASTM A500 or A572 is available upon request with cross-reference documentation.
Q: What surface treatment options are available for sharp corner tubes?
A: We supply Q235B and Q345B sharp corner tubes in hot-rolled black finish for indoor or painted applications, and hot-dip galvanized (HDG) for outdoor or corrosive environments. HDG provides uniform zinc coverage including corner radii and weld seams, ensuring consistent corrosion protection across the entire cross-section.
Q: Do you offer custom cutting and processing for sharp corner tubes?
A: Yes. We provide cut-to-length service for 5–15 m requirements, bending to project-specified angles, punch-hole patterns per fabrication drawings, and welding prep. Custom processing reduces shop-floor labor for steel fabricators and ensures dimensional accuracy for tight structural connections.
Q: How do you verify sharp corner tolerance and dimensional accuracy?
A: Each Q235B Q345B sharp corner square rectangular steel tube undergoes dimensional inspection covering width, height, wall thickness, corner radius, and straightness within ±1% tolerance. Dimensional reports are available with shipment. Third-party inspection by SGS or BV can be arranged before loading for EPC project quality requirements.
