Description
Factory-Direct Sharp-Corner Tubes, No Trading Markup — Q345B and Q235B sharp-corner square and rectangular steel tubes produced on our own ERW and hot-rolled lines, shipped with full mill documentation to 50+ countries.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q345B / Q235B Sharp-Corner Square and Rectangular Steel Tube |
| Product Type | Sharp-Corner Square and Rectangular Steel Tube |
| Steel Grade | Q345B, Q235B |
| Standard | GB/T 6728; equivalent to EN 10219 S355JR / ASTM A500 upon request |
| Section Shape | Square / Rectangular (Sharp-Corner / Right-Angle) |
| Side Length (Width) | 150–625 mm |
| Wall Thickness | Up to 40 mm |
| Length | 5–15 m (standard 5.8 m / 6 m / 12 m available) |
| Technique | ERW (Electric Resistance Welded) / Hot Rolled |
| Surface Treatment | Hot Rolled (Oiled / Non-Oiled options) |
| Tolerance | ±1% (dimensional) |
| Processing Service | Bending, Cutting, Decoiling, Punching, Welding |
| Application | Construction building / Steel structures / Structural frames / EPC project procurement |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Steel structure frames for industrial plants, warehouse portals, equipment support gantries |
| Construction Companies | High-rise building columns, beam-to-column moment connections, bridge support piers |
| Machinery Manufacturers | Equipment bases, conveyor frame uprights, crane boom sections requiring true 90° corners |
| System Integrators | Automation rack structures, material handling frames, modular scaffolding systems |
Where Corner Radius Tolerance Decides Site Assembly Speed
A 4 mm difference in corner radius can force full-batch re-cutting on a steel frame job.
I remember a shipment of sharp-corner rectangular tubes to a Saudi structural project — the drawings called for R≤2 mm internal corners, but the mill ran them at R6 using a conventional forming pass. On-site, the beam-to-column splice plates would not sit flush; every connection had to be torch-cut and re-welded, burning twenty-plus days off the schedule. Since then, I check internal corner radii on every sharp-corner tube before it leaves the floor. For buyers sourcing a Q345B sharp-corner square and rectangular steel tube supplier, this is the kind of dimensional gap that no catalogue photo will reveal — only a supplier running dedicated sharp-corner forming dies and holding ±1% tolerance on all critical dimensions can close it. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching True 90° Corners to Moment-Connection Detailing
Structural moment frames and machinery bases depend on flat bearing surfaces at tube corners. The patented sharp-corner forming process on our Q345B sharp-corner square and rectangular steel tube production lines produces internal radii tight enough for gusset plates and end-plates to seat without gap-filling welds. Wall thicknesses up to 40 mm across the 150–625 mm width range cover everything from light conveyor uprights to heavy industrial portal columns — all from one factory source holding 2,800+ standard and non-standard specifications.
Structural Code Compliance and Corrosion Environment Selection
Load-bearing frames designed to EN 1993 or AISC require verified steel grade equivalence and traceable mill certificates. Q345B maps to S355JR under EN 10219 and ASTM A500 Grade C on request, so the same tube can serve EU, North American, and GCC projects without re-ordering. For outdoor or coastal exposure, hot-rolled oiled finish provides transit protection; buyers needing longer-term corrosion resistance can specify galvanizing or paint systems as post-processing. CE certification under EN 10210 / EN 10219 clears EU customs without supplementary testing, while Singapore FPC covers Southeast Asian port entry. [NEED_CITE: steel grade equivalence between GB Q345B, EN S355JR, and ASTM A500]
How ERW Forming and Hot Rolling Shape the Final Profile
The Q345B and Q235B grades sit in the low-alloy high-strength and carbon structural categories respectively — Q345B delivers higher yield capacity for primary frames, while Q235B suits secondary bracing and non-critical supports. ERW welding produces a continuous longitudinal seam with consistent mechanical properties across the section, ideal for the 150–625 mm width range where seamless alternatives become cost-prohibitive. Hot rolling adds grain refinement through controlled temperature deformation, improving toughness for thicker walls up to 40 mm. The sharp-corner forming sequence uses multi-pass calibrated rolls to push the internal radius toward zero without cracking the outer fibre — a proprietary technique backed by 41 patents, several of which filled gaps in global sharp-corner tube specifications. Surface options stay practical: oiled hot-rolled finish for indoor or short-transit jobs, with decoiling, cutting, punching, and welding available in-house before dispatch.
The Hidden Cost of Unverified Corner Radii and Grade Substitution
Ordering sharp-corner tubes from a supplier without dedicated forming tooling often means receiving conventional radius corners marketed as “sharp.” On-site, this triggers re-cutting, re-welding, and schedule slippage — costs that dwarf any per-tonne price saving. Worse, unverified grade substitution (e.g., shipping Q235B against a Q345B order) passes visual inspection but fails structural load testing, forcing member replacement after erection. Missing or incomplete mill test certificates delay customs clearance on CE-marked shipments, sometimes by weeks. [NEED_CITE: consequences of non-compliant steel hollow sections in structural engineering projects]
Why Procurement Teams Return for Sharp-Corner Tube Orders
Our three dedicated production lines run sharp-corner forming dies in-house, so the R≤2 mm corners your drawings specify are the corners you receive — verified by our own physical and chemical laboratory before any tube is bundled. With 2,800+ specifications in stock and custom non-standard sizes available, you consolidate pipe, plate, section steel, and fabrication from a single factory rather than coordinating five vendors. Every shipment carries original mill test certificates tied to heat numbers, CE documentation under EN 10210 / EN 10219 for EU compliance, and third-party SGS or BV inspection reports on request. Professional loading plans optimize container weight for the 150–625 mm section range, and our export team has handled door-to-door logistics to 50+ countries across the EU, North America, the Middle East, India, and Southeast Asia for nearly two decades.
Documentation & Compliance
- Mill test certificate documenting Q345B or Q235B chemical composition and mechanical properties per GB/T 6728, with EN 10219 / ASTM A500 equivalence stated upon request
- CE certificate covering EN 10210 and EN 10219 for sharp-corner square and rectangular hollow sections entering EU member states
- ISO 9001:2015 quality management certificate covering the full production and inspection workflow
- SGS or BV third-party inspection report available at factory prior to container loading
- Full heat-number traceability from slab to finished tube, reflected on every certificate and packing list
- Customs document package including packing list, bill of lading, and certificate of origin for the destination country
Packaging, Loading & Delivery
- Q345B and Q235B sharp-corner tubes bundled with high-tensile steel strips and edge protectors to preserve the hot-rolled oiled surface and prevent corner denting during ocean transit
- Cut-to-length service available across the 5–15 m range, with standard 5.8 m / 6 m / 12 m lengths pre-sorted to maximize 20ft and 40ft container payload
- Heat number and steel grade stencilled on each tube end for on-site identification and traceability matching against mill test certificates
- In-house bending, cutting, punching, and welding completed before packing, reducing secondary fabrication at the project site
- FOB, CIF, and DDP shipping terms with professional container loading plans optimized for the 150–625 mm width and up-to-40-mm wall thickness profile
Ready to Lock in Sharp-Corner Tube Specs and Mill Certificates
Send your section dimensions, steel grade (Q345B or Q235B), quantity, and destination port — we return a detailed quotation including unit price, production lead time, applicable certifications, and loading plan within 12 hours. Non-standard sizes outside the 2,800+ catalogue and custom cut-to-length requests are quoted with the same mill test certificate and CE documentation package.
Request Your Sharp-Corner Tube Quotation and Mill Test Certificate Today
Submit your specifications via email at admin@sdxjysteel.com or WhatsApp at +86 188 5315 7756 to receive pricing, certification documents, and container loading confirmation.
Frequently Asked Questions
Q: How does Q345B compare to S355JR and ASTM A500 Grade C for structural use?
A: Q345B is the Chinese GB/T 6728 equivalent of EN 10219 S355JR and ASTM A500 Grade C. All three grades occupy the same yield strength class for structural hollow sections. We state the equivalence on mill test certificates so your engineer can approve substitution without additional testing.
Q: Can I order sharp-corner rectangular tubes in non-standard sizes outside the 150–625 mm catalogue?
A: Yes. Our factory holds 2,800+ standard specifications and runs custom non-standard sizes on dedicated forming lines. Send your drawing with outer dimensions, wall thickness, length, and corner radius requirement — we confirm feasibility and lead time before contract.
Q: What surface treatment options are available for Q345B sharp-corner tubes in corrosive environments?
A: Standard delivery is hot-rolled with oiled or non-oiled finish for indoor or short-transit protection. For outdoor, coastal, or industrial atmosphere exposure, galvanizing or painted coatings can be applied as post-processing. We advise based on your project environment and design life.
Q: Which certifications are included for EU customs clearance?
A: Every EU-bound shipment carries the CE certificate under EN 10210 and EN 10219, mill test certificates with heat-number traceability, and a full customs document package. SGS or BV third-party inspection is available at factory before loading if your project specification requires it.
Q: How is invoicing calculated — theoretical weight or actual weight?
A: We invoice based on theoretical weight calculated from the ordered dimensions and wall thickness per the applicable standard. Actual delivered weight may vary within the ±1% dimensional tolerance stated in the specification. Negative tolerance practice follows GB/T 6728 unless your purchase order specifies otherwise.
Get Your Q345B Q235B Sharp-Corner Square and Rectangular Steel Tube Quote with Full Mill Documentation
Email admin@sdxjysteel.com or message +86 188 5315 7756 on WhatsApp with your section sizes, steel grade, and quantity — we return pricing, CE and ISO certificates, and container loading confirmation within 12 hours.
