Description
Factory-direct Q345B RHS — ERW welded rectangular hollow sections from 15×20mm to 700×800mm, shipped with in-house mill test certificates and CE documentation for EU project compliance.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q345B Rectangular Hollow Section |
| Product Type | Welded Rectangular Steel Tube / RHS |
| Steel Grade | Q345B, Gr.B, S235, S275, S355, STK400 |
| Standard | ASTM A500, ASTM A53, GB/T 3091 |
| Section Shape | Rectangular |
| Size Range | 15mm×20mm – 700mm×800mm |
| Wall Thickness | 1 – 30 mm |
| Length | 5.8m / 6m / 11.8m / 12m / Random Length |
| Technique | ERW / Welded |
| Surface Treatment | Black Painting / Galvanized / Varnish / Bare |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Curtain walls / Support structures / Building frames |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Steel structure frames for industrial warehouses and commercial buildings |
| Construction Companies | Curtain wall support systems, high-rise structural columns and beam-to-column connections |
| Machinery Manufacturers | Equipment base frames, conveyor support structures, and crane boom sections |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A Q345B rectangular hollow section that fails ±1% tolerance triggers rework, not just rejection.
When structural engineers specify wall thickness for load-bearing columns, they calculate based on the nominal dimension. If the actual wall runs thin beyond acceptable deviation, the entire section’s moment of inertia drops — and the frame may not pass final inspection. I have seen project teams discover tolerance issues only after the steel arrives on site, forcing them to reorder while the crane sits idle. For a Q345B rectangular hollow section supplier, maintaining ±1% across a 30mm wall on a 700×800mm section is not a marketing claim; it is the difference between a frame that passes ultrasonic testing and one that gets torn down. [NEED_CITE: EN 10219 cold-formed welded structural hollow section dimensional tolerances]
How ERW Welded RHS Meets Structural Load Requirements
A Q345B rectangular hollow section produced through ERW welding delivers consistent seam integrity across the full 1–30mm wall thickness range. The electric resistance welding process fuses the formed plate edges under controlled pressure, producing a weld zone that matches the base metal’s structural performance when properly inspected. For curtain wall supports and building frames, the rectangular profile provides two flat bearing surfaces that simplify bolted and welded connections — eliminating the gusset plates that round tubes often require. Our in-house laboratory tests every weld seam for continuity and dimensional accuracy before release, ensuring that each Q345B rectangular hollow section meets the load path requirements specified in structural drawings.
Engineering Compliance and Surface Protection for Project Environments
Structural frames erected in coastal or industrial atmospheres demand surface treatment decisions made before the steel leaves the mill. Hot-dip galvanized Q345B rectangular hollow sections resist corrosion in outdoor exposure conditions, while black painted or varnished finishes suit indoor structural applications where aesthetics matter less than cost control. For EU-bound projects, CE certification under EN 10210 and EN 10219 is not optional — customs authorities require it, and project inspectors will halt erection without it. [NEED_CITE: CE marking requirements for structural steel hollow sections under EN 10219] The 5.8m and 11.8m length options align with standard container dimensions, reducing on-site cutting waste and secondary processing costs.
Steel Grade Selection Across International Standards
Q345B belongs to the Chinese GB standard system and corresponds closely to S355JR in the European EN framework and ASTM A500 Grade C in the American system. When a project specification calls for S355, sourcing Q345B rectangular hollow section with proper equivalence documentation satisfies the engineer’s intent without requiring a separate procurement channel. S235 and S275 grades serve lighter structural applications where full S355 capacity is unnecessary, reducing material cost per ton. STK400 addresses Japanese-standard projects common in Southeast Asian markets. The ERW welding process maintains consistent mechanical properties across all these grades because the forming and welding parameters are adjusted per grade — not run at a single setting for all products.
Hidden Costs of Unverified Steel Procurement
Ordering a Q345B rectangular hollow section without mill test certificate traceability means the buyer absorbs every downstream risk. If the chemical composition does not match the declared grade, weld procedures may fail qualification tests — delaying fabrication by weeks. If the wall thickness falls below the tolerance band, the structural engineer must recalculate the entire frame, potentially requiring additional bracing or section upgrades. Certification gaps create customs holds that turn a planned CIF delivery into a demurrage bill. [NEED_CITE: consequences of missing mill test certificates in international steel trade] These costs never appear in the initial purchase price comparison, but they routinely exceed the per-ton savings from choosing an unverified source.
Procurement Confidence Built on Verifiable Controls
As a factory-direct Q345B rectangular hollow section supplier, we eliminate the markup layers that trading companies add between the mill and the job site. Our three dedicated production lines cover over 2,800 specifications in rectangular, square, and round profiles — meaning your 700×800×30mm section and your 15×20×1.5mm tube ship from the same facility under the same quality system. The in-house physical and chemical laboratory tests every heat number before the material advances to the welding station, producing original mill test certificates that travel with the shipment. Our proprietary sharp-corner rectangular tube technology — holding 41 patents — delivers tight corner radii that improve connection fit-up for structural frames. CE certification under EN 10210/EN 10219, ISO 9001:2015 registration, and third-party verification through SGS and BV provide the documentation package that EU, North American, and Middle Eastern project owners require.
Documentation & Compliance
- Mill test certificate documenting Q345B chemical composition and mechanical properties per GB/T 3091, with heat number traceability for every delivered length
- CE certificate confirming compliance with EN 10210 and EN 10219 for structural hollow sections destined for European Union construction projects
- ISO 9001:2015 quality management certificate covering the full ERW welding, forming, and inspection process for welded rectangular steel tubes
- SGS or BV third-party inspection report available upon request, verifying wall thickness, dimensional tolerance, and surface treatment quality before container sealing
- Material traceability report linking each bundle to its original heat number, steel grade certification, and production date for project audit requirements
- Complete customs documentation package including packing list, bill of lading, and certificate of origin formatted for destination-country import clearance
Packaging, Loading & Delivery
- Q345B rectangular hollow sections bundled with high-tensile steel strips and edge protectors, preventing zinc coating damage on galvanized surfaces during ocean transit
- Galvanized RHS wrapped in waterproof paper with desiccant inserts to preserve surface quality in humid port storage conditions before and after loading
- Container loading plans optimized for 5.8m and 6m lengths in 20ft containers and 11.8m/12m lengths in 40ft open-top or flat-rack units, maximizing payload per shipment
- Custom cutting to project-specific lengths available before shipment, reducing on-site waste and cutting labor costs for EPC contractors
- Heat number and steel grade stenciled on each tube end, with bundle tags matching the mill test certificate for immediate site identification
- FOB, CIF, and DDP shipping terms available to 50+ countries, with professional loading supervision at the port to prevent transit damage
Start Your Q345B RHS Procurement with Verified Documentation
Submit your specification sheet — including section dimensions, wall thickness, steel grade, surface treatment, quantity, and destination port — and receive a detailed quotation with delivery timeline and applicable certification package within 12 hours. For non-standard sizes outside the 15×20mm to 700×800mm range, our engineering team provides custom feasibility assessment and lead time confirmation. Request original mill test certificates and third-party inspection reports before committing to production.
Get Your Q345B Rectangular Hollow Section Quote with Full Mill Documentation
Send your specifications via email or WhatsApp to receive pricing, certification details, and production lead time.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxjysteel.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjysteel.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
Frequently Asked Questions
Q: How does Q345B compare to S355JR and ASTM A500 Grade C?
A: Q345B is the Chinese GB standard equivalent of S355JR (EN 10219) and ASTM A500 Grade C. All three grades share similar yield strength ranges and chemical composition limits, making them interchangeable for most structural applications when supported by proper mill test certificate documentation confirming equivalence.
Q: Can you provide third-party inspection before shipment?
A: Yes. SGS and BV third-party inspections are available for any order. The inspection covers dimensional verification, wall thickness measurement, surface treatment quality, and visual weld seam examination. The inspection report is issued before container sealing and travels with the shipment documentation.
Q: What is the policy for custom non-standard sizes?
A: We produce non-standard rectangular hollow sections outside the 15×20mm to 700×800mm catalog range, subject to engineering feasibility review. Custom sizes require technical drawing confirmation and may carry different minimum order quantities than standard catalog items. Contact our team with your specific dimensions for assessment.
Q: Which surface treatment is best for outdoor structural applications?
A: Hot-dip galvanized Q345B rectangular hollow sections provide the longest corrosion protection life for outdoor exposure, including coastal and industrial environments. Black painted or varnished finishes suit indoor structural frames where corrosion risk is low. Bare tubes are available for projects where the buyer applies their own coating system after fabrication.
Q: What shipping terms and documentation do you provide for EU projects?
A: We offer FOB, CIF, and DDP terms to European ports. Every EU-bound shipment includes CE certification under EN 10210/EN 10219, mill test certificates per EN 10204 3.1, packing list, bill of lading, and certificate of origin — formatted to meet EU customs and project inspection requirements.
