Description
Factory-direct Q345B rectangular steel tube — vertically integrated from raw steel billet to finished welded RHS, eliminating third-party material gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q345B Rectangular Steel Tube |
| 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 | Construction Pipe / Building Pipe / Curtain Wall Pipe / Support Tubes / Structure Pipe |
| Invoicing | By Theoretical Weight |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial Construction | Steel frame structures for office buildings, shopping centers, and multi-story facilities |
| Industrial Facilities | Warehouse portal frames, equipment support platforms, conveyor structures |
| Architectural Curtain Wall | Mullion and transom support tubes, facade framing systems |
| Infrastructure | Bridge support columns, sound barrier frames, utility structure frameworks |
Where Material Traceability Gaps Cause Customs Holds
A Q345B rectangular steel tube supplier without integrated mill production creates certification voids that delay port clearance.
When structural steel tubes arrive at EU or Middle Eastern ports without heat-number-linked mill test certificates, third-party inspectors flag the shipment for re-verification. I have seen entire container loads of RHS held for weeks because the fabricator sourced black tubes from three different mills and could not provide consistent chemical composition records. The Q345B rectangular steel tube supplier who controls raw material procurement through final welding eliminates this documentation gap — every heat number traces back to a single steelmaking batch, and every weld seam carries the same WPS qualification. [NEED_CITE: EN 1090 structural steel fabrication documentation requirements]
How Wall-Thickness Tolerance Aligns with Structural Load Calculations
Engineers specifying Q345B rectangular steel tube for portal frames and curtain wall supports calculate member capacity based on nominal wall thickness. The ±1% tolerance control on our ERW welded RHS ensures that a 10mm wall section never falls below 9.9mm actual — critical when structural software assumes full-section properties for moment resistance. For curtain wall applications where 15mm×20mm to 100mm×200mm tubes carry cladding loads rather than primary structural loads, consistent wall thickness prevents deflection exceedance under wind pressure. The Q345B rectangular steel tube supplier offering integrated production maintains uniform forming pressure across the full 1–30mm wall range, avoiding the thin-wall variations that occur when fabricators outsource to multiple tube mills with different ERW line calibrations.
Compliance Pathways for International Structural Projects
Structural engineers designing to EN 1993 require hollow sections conforming to EN 10219, while AISC 360 projects specify ASTM A500 Grade B or C. Q345B rectangular steel tube in our inventory meets the chemical composition and mechanical property ranges for both S355JR and ASTM A500 Grade B through grade equivalence mapping — but the Q345B rectangular steel tube supplier must provide documentation proving this equivalence, not just verbal assurance. For projects in Southeast Asia and Africa, GB/T 3091 compliance with Q345B grade satisfies local building codes while offering cost advantages over imported S355 material. Third-party inspection by SGS or BV before shipment confirms dimensional accuracy, coating thickness for galvanized tubes, and weld seam integrity per approved WPS procedures. [NEED_CITE: steel grade equivalence between Q345B and S355JR standards]
ERW Welding Process and Surface Treatment Selection
The ERW (Electric Resistance Welding) process forms rectangular tubes by cold-rolling steel strip into shape and welding the longitudinal seam through electrical resistance heating — producing a weld zone with mechanical properties matching the base metal when proper WPS parameters are maintained. For Q345B rectangular steel tube applications in coastal or industrial environments, hot-dip galvanizing provides 45–80 micron zinc coating thickness for corrosion protection extending service life beyond painted alternatives. Black painting suits indoor structural applications where aesthetic appearance matters less than budget control, while bare tubes serve projects requiring field welding or custom coating by the contractor. The wall thickness range of 1–30mm covers both light-gauge curtain wall supports and heavy structural columns, with ERW welding maintaining consistent seam quality across the full thickness spectrum. [NEED_CITE: ERW welded hollow section manufacturing process standards]
Hidden Costs of Sourcing from Fragmented Supply Chains
Purchasing Q345B rectangular steel tube from a trading company rather than an integrated manufacturer introduces three failure modes: material certification gaps when tubes from different mills are blended into one order, dimensional inconsistency when wall thickness varies between batches, and weld quality uncertainty when the trader cannot verify WPS compliance at the actual fabrication site. These issues surface as engineering rejections during structural inspection, customs delays from incomplete MTC documentation, or field rework when tube dimensions do not match connection details. The Q345B rectangular steel tube supplier controlling the entire production chain from steel plate to finished RHS eliminates these risks through single-source accountability and complete quality documentation packages. [NEED_CITE: structural steel fabrication quality control requirements for international projects]
Why Integrated Production Reduces Procurement Risk
Our facility operates three tube production lines with 2,800+ specifications in raw material inventory, enabling same-batch procurement for orders requiring multiple Q345B rectangular steel tube sizes. The in-house metallurgical laboratory issues mill test certificates documenting chemical composition and mechanical properties for every heat number — no reliance on third-party mill documents that may not match delivered material. Certified welding procedures (WPS/PQR) and qualified welders per AWS and EN standards ensure every ERW seam meets structural code requirements. Professional loading teams calculate container weight distribution for 6m and 12m lengths, maximizing payload while preventing transit damage to galvanized coatings. Complete export documentation including packing lists, bills of lading, and certificates of origin supports customs clearance in destination countries. [NEED_CITE: vertically integrated steel fabrication supply chain advantages]
Documentation & Compliance
- Mill test certificate documenting Q345B chemical composition (C, Mn, Si, S, P content) and mechanical properties per GB/T 3091, with heat number traceability to raw steel batch
- CE certificate confirming EN 10219 compliance for cold-formed welded structural hollow sections exported to European Union markets
- ISO 9001 quality management system certification covering the full production process from material procurement through final inspection
- SGS or BV third-party inspection report verifying dimensional accuracy, wall thickness tolerance, and coating thickness for galvanized Q345B rectangular steel tube orders
- Material traceability documentation linking each tube bundle to specific heat numbers, welding records, and inspection test reports
- Complete customs documentation package including packing lists, bills of lading, certificates of origin, and fumigation certificates for wooden packaging
Packaging, Loading & Delivery
- Q345B rectangular steel tube bundled with steel strips and edge protectors to prevent coating damage during ocean transit, with bundle weight optimized for 20ft and 40ft container payload limits
- Galvanized RHS tubes wrapped in waterproof plastic sheeting with desiccant packets to prevent white rust formation during humid climate shipping
- 6m and 12m lengths loaded with wooden chocks and steel wire lashing to prevent shifting, maximizing container utilization for sizes from 15mm×20mm to 700mm×800mm
- Custom cut lengths available per project requirements, with random length orders sorted by actual measurement and marked with heat number and steel grade
- Bundle identification tags showing Q345B grade designation, size specifications, heat number, and production date for site inventory management
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination to project sites in Middle East, Southeast Asia, Africa, and South America
Requesting Quotation with Complete Technical Documentation
Submit your project drawings or specification list indicating Q345B rectangular steel tube sizes, wall thickness, length requirements, surface treatment preference, and destination port to receive a detailed quotation within 24 hours. The quotation includes material cost, fabrication charges, coating fees, packaging costs, and shipping rates with complete mill test certificate and third-party inspection documentation. For projects requiring grade equivalence verification or custom sizes outside standard ranges, our engineering team provides technical support for material selection and production scheduling. Confirm your order with a 30% deposit upon drawing approval, and receive production updates with in-process inspection photos until container loading.
Frequently Asked Questions
Q: How does Q345B grade compare to S355JR and ASTM A500 Grade B for structural applications?
A: Q345B meets the chemical composition and mechanical property ranges for both S355JR per EN 10219 and ASTM A500 Grade B through grade equivalence mapping. Our mill test certificates document the specific carbon, manganese, and silicon content for each heat number, enabling engineers to verify compliance with their project’s design standard. For European projects requiring CE marking, we provide EN 10219 compliance documentation alongside the Q345B material certification.
Q: What surface treatment options are available for Q345B rectangular steel tube in corrosive environments?
A: Hot-dip galvanizing provides 45–80 micron zinc coating thickness suitable for coastal, industrial, and outdoor applications requiring long-term corrosion protection. Black painting offers cost-effective protection for indoor structural applications, while varnish coating provides aesthetic finish for architectural exposures. Bare tubes serve projects requiring field welding or custom coating application by the contractor after delivery.
Q: How do you ensure wall thickness consistency across large orders?
A: Our ERW welding lines maintain ±1% tolerance control through continuous ultrasonic thickness measurement during production. Each bundle receives dimensional inspection reports documenting actual wall thickness at multiple points, ensuring the Q345B rectangular steel tube meets structural design assumptions. Orders requiring tight tolerance for connection details receive 100% inspection rather than sampling.
Q: Can you provide custom lengths outside the standard 5.8m, 6m, 11.8m, and 12m range?
A: Yes, we produce random lengths and custom cut-to-size Q345B rectangular steel tube per project requirements. Custom lengths incur additional cutting charges but reduce field waste and welding connections. We coordinate with your shipping forwarder to optimize container loading for non-standard lengths, maximizing payload efficiency.
Q: What third-party inspection services do you accept before shipment?
A: We facilitate inspection by SGS, Bureau Veritas, TÜV, or your nominated inspection agency at our facility before container loading. The inspection covers dimensional accuracy, wall thickness verification, coating thickness measurement for galvanized tubes, visual weld inspection, and documentation review. Inspection costs are quoted separately and charged to the buyer’s account.
Get Your Q345B Rectangular Steel Tube Quotation with Mill Test Certificates
Send your project specifications including sizes, quantities, surface treatment requirements, and destination port to receive a detailed quotation with complete technical documentation within 24 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
