Description
Factory-Direct Sharp-Corner Tubes — As the original inventor of right-angle rectangular steel tubes in China, we hold 41 patents for this proprietary forming process and ship Q235B Q345B sharp corner square rectangular steel tube orders to 50+ countries with full mill test documentation.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B / Q345B Sharp Corner Square & Rectangular Steel Tube |
| Product Type | Sharp Corner Square and Rectangular Steel Tube |
| Steel Grade | Q235B, Q345B |
| Standard | GB/T 6728 |
| Section Shape | Square / Rectangular (Sharp Corner / Right-Angle) |
| Side Length / Width | 150–625 mm |
| Length | 5–15 m (Standard: 5.8 m / 6 m / 12 m) |
| Technique | ERW (Electric Resistance Welded) / Hot Rolled |
| Surface Treatment | Hot Rolled / HDG (Hot-Dip Galvanized) |
| Tolerance | ±1% (dimensional) |
| Processing Service | Bending, Cutting, Decoiling, Punching, Welding |
| Application | Construction building, Steel structures, Architectural facades, Glass curtain walls, High-end steel structures |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Architectural Facade Contractors | Glass curtain wall framing, building exterior steel skeletons, decorative column wraps |
| Steel Structure Fabricators | Beam-to-column connections, portal frame members, mezzanine floor supports |
| High-Rise Construction | Core tube bracing, transfer truss chords, elevator shaft framing |
| Machinery Manufacturers | Equipment base frames, conveyor support structures, crane boom sections |
Why True 90-Degree Corners Decide Whether a Curtain Wall Looks Finished
Standard ERW rectangular tubes produce rounded corners with R≥2t — visible as uneven gaps at every joint on a glass facade.
When facade contractors receive ordinary rectangular tubes and try to weld them into curtain wall grids, the rounded corners create inconsistent joint widths that no amount of grinding can fix. The visual result is a wavy, unprofessional appearance across the entire building face. Sourcing a Q235B Q345B sharp corner square rectangular steel tube with genuine right-angle geometry eliminates this problem at the forming stage, not the installation stage. Beyond aesthetics, sharp corners provide full bearing contact at bolted connections, which matters for load transfer in steel structure frames [NEED_CITE: cold-formed steel hollow section dimensional tolerance requirements].
How Sharp-Corner Geometry Matches Facade and Structural Demands
A glass curtain wall system requires steel framing members that sit flush against mullion brackets and anchor plates — any corner rounding creates a gap that must be filled with shims or weld buildup, adding labor cost and introducing inconsistency. The patented sharp-corner forming process behind this Q235B Q345B sharp corner square rectangular steel tube produces true 90-degree internal and external corners, allowing direct bearing contact without secondary machining. For HDG-coated units used in exterior applications, the right-angle geometry also ensures more uniform zinc distribution at corner zones compared to rounded-corner tubes where inner radii can trap air during galvanizing.
Structural Code Compliance and Certification Pathways
Engineering projects in the EU require hollow sections conforming to EN 10219 (cold-formed) or EN 10210 (hot-formed), with CE marking validated through Factory Production Control audits. For North American projects, ASTM A500 Grade B or C equivalence is typically specified. Q235B roughly corresponds to S235JR under EN 10025, while Q345B aligns with S355JR in yield strength class — but formal equivalence must be documented through mill test certificates referencing chemical composition and mechanical test results [NEED_CITE: steel grade equivalence mapping between GB and EN standards]. Our in-house physical and chemical laboratory tests every production batch, and third-party inspection through SGS or BV can be arranged before shipment to satisfy project-specific quality plans.
Understanding Q235B and Q345B for Structural Tube Selection
Q235B is a mild carbon steel with minimum yield strength suitable for non-load-bearing facade framing, interior structures, and general fabrication where high stress is not expected. Q345B offers a higher yield strength class, making it the preferred choice for primary structural members in steel buildings, bridge components, and heavy-duty machinery frames. Both grades are fully weldable using standard SMAW, GMAW, and FCAW processes. The ERW welding technique used for these tubes produces a longitudinal weld seam that is normalized online, ensuring the weld zone matches the base metal in strength and ductility. For projects requiring corrosion resistance without field painting, HDG surface treatment provides a zinc coating that protects both the outer surface and the internal cavity of the tube.
The Hidden Cost of Accepting Rounded Corners as “Sharp”
Procuring tubes marketed as “sharp corner” that actually carry R≥2t rounding leads to three compounding costs on site: facade contractors spend extra labor grinding and filling joints, structural engineers must recalculate connection capacity due to reduced bearing area, and project inspectors may reject material that does not match the approved shop drawings. When certification documents reference the wrong standard — for example, a CE mark citing EN 10219 for a hot-formed product — customs authorities in regulated markets can hold the entire shipment [NEED_CITE: EU customs requirements for steel construction product certification]. These are not theoretical risks; they are recurring issues we have documented across hundreds of container shipments to EU, Middle East, and Southeast Asian job sites.
What Makes Our Supply Chain Different for This Product
We developed the sharp-corner rectangular tube forming technology that filled a gap in both domestic and international markets — 41 invention patents back this claim. Our production lines cover 2,800+ specifications with wall thickness up to 40mm, meaning non-standard sizes that other mills refuse to quote are routine production for us. Every order ships with mill test certificates generated from our own laboratory, and we hold Lloyd’s CE certification under EN 10210/10219, Singapore FPC, and ISO 9001:2015 — so documentation matches the product, not the other way around. For export orders, our loading teams use purpose-built cradles and edge protectors to prevent corner damage during container stuffing, a detail that matters when right-angle geometry is the entire reason you chose this product.
Documentation & Compliance
- Mill test certificate documenting Q235B or Q345B chemical composition (C, Mn, Si, S, P) and tensile test results per GB/T 6728
- CE certificate under EN 10219 / EN 10210 with Factory Production Control number for EU customs clearance
- ISO 9001:2015 quality management system certificate covering the full production process
- SGS or BV third-party inspection report available upon request, covering dimensional checks, coating thickness measurement, and visual inspection
- Heat number traceability from raw coil to finished tube, marked on each piece and reflected in test documentation
- Export customs documents including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Sharp-corner Q235B Q345B tubes bundled with high-tensile steel strips and separated by rubberized edge protectors to preserve right-angle corners during transit
- HDG-coated units wrapped in waterproof PE film at corners and edges to prevent white rust formation from condensation during ocean shipping
- Container loading optimized for 5.8 m and 6 m standard lengths in 20ft containers, with 12 m lengths loaded in 40ft OT or flat-rack units using timber chocks
- Custom cutting to project-specific lengths available before shipment, with cut ends deburred and marked with heat number and steel grade
- Shipping terms FOB, CIF, or DDP to destination port, with full tracking provided from mill gate to job site
Start Your Procurement With the Right Information
To receive an accurate quotation and sample mill test certificate for this Q235B Q345B sharp corner square rectangular steel tube, submit your required dimensions (side length, wall thickness, length), steel grade preference, surface treatment choice, and destination port. For non-standard sizes outside the 150–625 mm range or wall thickness beyond standard offerings, our engineering team will confirm feasibility and lead time within one working day.
Request a Quote with Mill Test Certificate
Send your specifications to admin@sdxjypipe.com or contact us via WhatsApp at +86 188 5315 7756 for pricing, certification confirmation, and container loading plans.
