Description
Factory-Direct Rectangular Tubes — Q345B RHS produced on our own ERW and seamless lines, shipped with original mill certificates and no trading markup.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q345B Rectangular Steel Tube |
| Product Type | Rectangular Steel Tube (Hollow Section RHS) |
| Steel Grade | Q345B, Gr.B, S235, S275, S355, STK400 |
| Standard | ASTM A500, ASTM A53, GB/T3091 |
| 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 or Seamless |
| Surface Treatment | Black Painting / Galvanized / Varnish / Bare |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Construction Pipe, Building Pipe, Curtain Wall Pipe, Support Tubes, Structure Pipe |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial Construction | Building frames, column supports, mezzanine structures |
| Architectural Facade | Curtain wall mullions, cladding support tubes, canopy frames |
| Industrial Infrastructure | Equipment support structures, conveyor frames, platform handrails |
| Machinery Manufacturing | Machine base frames, hydraulic support columns, load-bearing brackets |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on a Q345B rectangular steel tube is the difference between passing structural inspection and rebuilding an entire bay.
When procurement teams source rectangular hollow sections from fragmented suppliers, the wall thickness often drifts into negative territory beyond acceptable limits. I have seen 6m lengths of what was labeled Q345B arrive at a Southeast Asian job site where the actual wall measured below the minimum allowed by the engineer’s calculation sheet. The entire batch had to be downgraded, the project delayed by weeks, and the buyer absorbed air-freight costs for replacement material. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
How Q345B RHS Matches Structural Load Requirements
The Q345B rectangular steel tube in sizes from 15mm×20mm up to 700mm×800mm covers the full spectrum from light architectural supports to heavy industrial columns. For curtain wall systems, the smaller sections in 1–3mm wall thickness provide adequate rigidity while keeping dead load minimal. When the same project requires main structural columns, the 300mm×400mm and larger sections in 10–30mm wall thickness deliver the moment of inertia that engineers specify for seismic and wind load zones. Our production lines run both ERW welded and seamless processes, so buyers can choose cost-efficiency for standard structural frames or seamless for higher-pressure applications.
Engineering Compliance and Surface Protection Selection
Structural frames in coastal or industrial environments face corrosion that bare steel cannot withstand. Hot-dip galvanized Q345B rectangular steel tubes provide zinc coating protection for outdoor structures, while black painting or varnish suits indoor applications where appearance matters less than cost. For European market projects, CE certification under EN 10210 (hot-finished) or EN 10219 (cold-formed) is mandatory for customs clearance — missing this documentation means the container sits at the port until compliance is proven. [NEED_CITE: CE marking requirements for structural hollow sections in EU construction products regulation] The steel grade selection between Q345B, S355, and ASTM A500 Gr.B must align with the project’s design code, and mill test certificates must trace each batch back to the heat number for audit compliance.
Steel Grade Equivalence and Production Process Selection
Q345B is the Chinese standard grade equivalent to S355JR in the European system and closely matches ASTM A500 Grade B in the American system. The yield strength hierarchy matters: S235 serves light-duty applications, S275 handles moderate structural loads, and S355 or Q345B is specified for main load-bearing members where higher strength reduces section size and weight. ERW welded tubes are produced by forming steel coil into rectangular shape and welding the seam — cost-effective for standard structural applications. Seamless rectangular tubes are manufactured from round seamless pipes through cold-drawing processes, offering uniform wall thickness and no weld seam for critical applications. Surface treatment choice depends on the environment: galvanized coating protects against atmospheric corrosion for 20+ years in moderate environments, while bare or painted tubes require on-site maintenance schedules.
Hidden Costs of Sourcing Without Verified Certification
Buying Q345B rectangular steel tubes without original mill test certificates creates risk that surfaces only during project inspection. If the chemical composition does not match Q345B requirements, the structural engineer cannot approve the material, forcing replacement at the buyer’s expense. Missing CE EN 10219 certification for European projects triggers customs holds that delay the entire construction timeline. [NEED_CITE: steel grade equivalence between Chinese GB and European EN standards] Third-party inspection by SGS or BV before shipment catches material non-conformance at the factory, not at the destination port where return logistics become prohibitively expensive.
Why Project Buyers Source Q345B RHS from Xinjiyuan
We operate three production lines running simultaneously with monthly capacity exceeding 20,000 tons, producing Q345B rectangular steel tubes in every size from 15mm×20mm to 700mm×800mm. Our factory-direct pricing eliminates trading company markups, and volume discount programs reward long-term procurement partnerships. Every batch ships with original mill test certificates documenting chemical composition and mechanical properties, with SGS or BV third-party inspection available on request. We hold CE EN 10210/EN 10219 and FPC certification for European market compliance, plus ISO 9001:2015 quality management certification. Our inventory covers 2,800+ specifications across all major steel product categories, enabling consolidated container loading when buyers need rectangular tubes, round pipes, and section steel in the same shipment. Professional export documentation and container loading optimization ensure that 11.8m lengths fit efficiently into 40ft containers without damage.
Documentation & Compliance
- Mill test certificate documenting Q345B chemical composition (C, Si, Mn, P, S) and mechanical properties per GB/T 1591
- CE certificate confirming compliance with EN 10210 for hot-finished or EN 10219 for cold-formed rectangular hollow sections
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report verifying dimensional tolerance, surface coating thickness, and material traceability
- Heat number traceability linking each Q345B rectangular steel tube bundle to the original steelmaking batch
- Complete customs documentation including packing list, bill of lading, and certificate of origin for destination country clearance
Packaging, Loading & Delivery
- Q345B rectangular steel tubes bundled with steel strips and edge protectors to prevent zinc coating damage during ocean transit for galvanized orders
- Black painted or varnished tubes wrapped in waterproof cloth to preserve surface finish during container loading and unloading
- 6m and 11.8m lengths loaded in 20ft and 40ft containers with optimized stacking plans to maximize payload while preventing deformation
- Random length or cut-to-order rectangular tubes available for projects requiring specific dimensions to reduce on-site waste
- Heat number and steel grade Q345B stenciled on each bundle for site identification and traceability verification
- FOB, CIF, and DDP shipping terms available with professional export team handling customs clearance and door-to-door logistics
Request Your Q345B Rectangular Tube Quotation
Submit your project specifications including section size, wall thickness, steel grade, surface treatment, and destination port to receive a competitive bulk quotation within 12 hours. We will provide original mill test certificates, confirm CE/EN certification for your market, and propose optimized container loading for your order quantity.
Get Factory-Direct Pricing with Mill Certificates
Email your inquiry to admin@sdxinjiyuan.com or contact via WhatsApp at +86 188 5315 7756 with your Q345B rectangular steel tube requirements.
Frequently Asked Questions
Q: What is the steel grade equivalence between Q345B, S355, and ASTM A500 Grade B?
A: Q345B is the Chinese standard grade that closely matches S355JR in the European EN system and ASTM A500 Grade B in the American system. All three grades serve structural applications with similar yield strength ranges, and our mill test certificates document the specific chemical composition and mechanical properties for your project’s design code compliance.
Q: Can you provide CE EN 10219 certification for European market projects?
A: Yes, our Q345B rectangular steel tubes carry CE certification under EN 10219 for cold-formed hollow sections and EN 10210 for hot-finished sections, with FPC (Factory Production Control) certification. This documentation is mandatory for European customs clearance and project compliance, and we provide the complete certificate package with every shipment.
Q: What is the minimum order quantity for Q345B rectangular steel tubes?
A: We accept flexible MOQ starting from 1 ton for trial orders, with volume discount programs for long-term partners placing regular bulk orders. Standard sizes are available from ready stock for urgent delivery, while custom non-standard sizes typically require 15–25 days production lead time.
Q: How do you ensure wall thickness tolerance meets ±1% specification?
A: Our in-house quality control lab conducts three-stage inspection during production, and we provide original mill test certificates documenting dimensional measurements for each batch. Third-party inspection by SGS or BV is available on request to verify wall thickness, outer dimensions, and surface coating thickness before shipment.
Q: Can you consolidate rectangular tubes with other steel products in one container?
A: Yes, we supply all major steel product categories including round pipes, section steel, and steel plates, enabling consolidated multi-product container loading. Our professional export team optimizes container loading plans to maximize payload while protecting surface finishes and ensuring efficient delivery to your project site.
