Description
Factory-direct ERW hollow sections — Q235B rectangular and square tubes rolled on our own lines with original mill test certificates shipped per container.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Rectangular Hollow Section |
| Product Type | Welded Rectangular Steel Tube (RHS/SHS) |
| Steel Grade | Q235B, Gr.B, S235, S275, S355, STK400 |
| Standard | ASTM A500, ASTM A53, GB/T 3091 |
| Section Shape | Square and 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 wall / Support tubes / Building structures |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Building & Construction | Curtain wall frames, column supports, roof trusses, mezzanine structures |
| Infrastructure | Bridge handrails, highway sign gantries, utility pole bases |
| Industrial Fabrication | Conveyor frames, machine bases, equipment support structures |
| Commercial Structures | Warehouse purlins, shopping center canopies, parking structure frames |
What Wall-Thickness Tolerance Actually Costs on a Structural Frame Order
A ±1% tolerance on a 30mm wall saves tons of rework and avoids customs rejection at destination port.
Global buyers sourcing structural hollow sections regularly face material that arrives thinner than declared — not by accident, but because the mill pushed negative tolerance to the edge to cut cost per ton. I once watched a 50×100 rectangular tube shipment get flagged at destination when the third-party inspector pulled calipers on random pieces and found walls consistently below the lower bound. The entire container sat in port for eleven days while arguments flew across email chains. On a Q235B rectangular hollow section order running 1–30mm walls, that ±1% tolerance is not a marketing line — it is the difference between a frame that passes structural inspection on arrival and one that triggers a full re-measurement audit. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed welded hollow sections]
Matching Q235B RHS to Structural Frame and Curtain Wall Loads
A Q235B rectangular hollow section in the 100×200mm to 300×500mm range with 6–16mm walls carries typical curtain wall and building frame loads without requiring higher-grade steel, keeping procurement cost predictable. The ERW welding process produces a consistent longitudinal seam that handles the bending moments common in vertical column and horizontal beam applications. For projects spanning both dry indoor environments and exposed exterior conditions, switching between black painting and hot-dip galvanized surface treatment on the same order lets procurement teams match corrosion protection to each zone without splitting the purchase across multiple suppliers.
Engineering Compliance and Certification Requirements
Structural frames designed under EN 1993 or AISC guidelines require traceable material certification — the Q235B rectangular hollow section ships with heat-number-linked mill test certificates covering chemical composition and mechanical properties per GB/T 3091, with equivalent grading available in S235/S275/S355 for EN 10219 compliance and Gr.B for ASTM A500 projects. [NEED_CITE: steel grade equivalence mapping between GB Q235B and EN S235JR] For Middle East and Southeast Asian infrastructure tenders, CE certification under EN 10210/EN 10219 is often a mandatory customs document rather than a quality preference. Fixed lengths of 6m and 12m align with standard container dimensions, reducing on-site cutting waste, while random length options serve fabrication shops that optimize nesting from raw stock.
Understanding Q235B and Multi-Grade ERW Welding
Q235B sits at the entry point of Chinese structural steel grades, offering adequate yield performance for non-heavy-load building frames and support structures at lower cost than S-series or ASTM equivalents. When a project specification calls for S235, S275, or S355, the递增 yield strength across these grades allows engineers to reduce wall thickness while maintaining load capacity — a direct weight and cost saving on large-volume rectangular hollow section orders. The ERW welding process forms the tube by rolling flat strip into shape and welding the longitudinal seam through high-frequency current, producing a clean internal bead suitable for most structural applications without the cost premium of seamless manufacturing. Surface treatment selection follows environment: bare or varnished tubes serve indoor structural frames where appearance is secondary, black painting provides basic rust prevention for covered outdoor structures, and hot-dip galvanizing extends service life in coastal or industrial atmospheres where corrosion accelerates. [NEED_CITE: ERW welded versus seamless hollow section application comparison]
The Hidden Cost of Buying Hollow Sections Without Verified Tolerance
Purchasing a Q235B rectangular hollow section based on price alone, without confirmed wall tolerance and traceable mill certificates, creates downstream costs that dwarf the initial savings. Material that fails dimensional inspection at destination triggers port storage fees, re-sorting labor, and potential rejection — all while the project schedule burns through crane rental and crew standby days. Certification gaps — missing CE marks for European tenders or incomplete mill test reports for Middle East customs — turn a straightforward delivery into a weeks-long documentation scramble. [NEED_CITE: structural steel certification requirements for international construction projects]
Why Bulk Buyers Source Q235B Rectangular Hollow Sections From Us
Our three production lines run Q235B rectangular hollow sections alongside S-series and STK grades, meaning a single order spanning multiple steel grades and wall thicknesses ships from one facility with unified quality control rather than fragmented sourcing. Every batch carries original mill test certificates tied to heat numbers, and our in-house lab runs three-stage inspection before any container closes — a process refined after early export lessons taught us that trust is built on documentation, not promises. With over 2,800 specifications in ready stock, standard sizes ship within days while custom orders in non-standard dimensions or specific lengths complete within typical production lead times. We hold ISO 9001:2015, CE (EN 10210/EN 10219), and FPC certifications, and welcome SGS or BV third-party inspection on any order at buyer’s request. Professional export documentation and container loading optimization ensure that a mixed order of 6m and 12m Q235B rectangular hollow sections maximizes payload per container without damaging surface treatment during transit.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition (C, Mn, Si, S, P) and mechanical properties per GB/T 3091, linked to heat number
- CE certificate covering EN 10210/EN 10219 for European market structural hollow section compliance
- ISO 9001:2015 quality management certificate covering production and inspection processes
- SGS or BV third-party inspection report available on request, covering dimensional checks and visual weld seam examination
- Material traceability report mapping each bundle to heat number, production date, and test results
- Full customs document package: packing list, bill of lading, certificate of origin, and commercial invoice
Packaging, Loading & Delivery
- Q235B rectangular hollow sections bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Galvanized tubes wrapped with waterproof paper and plastic film to preserve zinc coating integrity through humid port storage
- Mixed-size container loading optimized for 6m and 12m lengths, maximizing payload while protecting plain-end tubes from deformation
- Heat number and steel grade stenciled on each bundle for on-site identification and traceability verification
- FOB, CIF, and DDP shipping terms available with professional export team handling customs clearance and port coordination
- Random length and cut-to-order options available for fabrication shops requiring specific nesting dimensions
Getting Your Q235B Rectangular Hollow Section Quote Moving
Submit your specification list — section dimensions, wall thickness, steel grade, total tonnage, and destination port — and receive a detailed quotation with volume pricing, production timeline, and mill test certificate confirmation within 12 hours. For non-standard dimensions or mixed-grade orders, our team provides a consolidated loading plan showing how multiple specifications fit into shared containers.
Start Your Q235B Rectangular Hollow Section Inquiry
Send specifications and quantity to receive factory-direct pricing and mill test certificate samples.
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
Frequently Asked Questions
Q: What is the difference between Q235B, S235, and ASTM A500 Gr.B for rectangular hollow sections?
A: Q235B is the standard Chinese structural grade per GB/T 3091, S235 is the European equivalent per EN 10219, and Gr.B is the American standard per ASTM A500. All three serve similar structural applications with comparable yield performance, and we supply each grade from the same production lines with appropriate certification for your target market.
Q: Can I get third-party inspection before shipment for my Q235B rectangular hollow section order?
A: Yes, SGS and BV third-party inspections are available on request. The inspection covers dimensional verification, wall thickness measurement, visual weld seam examination, and review of mill test certificates before container loading.
Q: What is the minimum order quantity for custom sizes outside your standard range?
A: We accept trial orders starting from 1 ton for standard specifications in ready stock. For non-standard dimensions or custom lengths outside 5.8m/6m/11.8m/12m, minimum quantities depend on production setup requirements — contact us with your specification for a detailed response.
Q: How do you ensure wall thickness tolerance on ERW welded rectangular tubes?
A: Every production batch undergoes three-stage in-house inspection including caliper measurement at multiple points along the tube length. We maintain ±1% tolerance on wall thickness and provide original mill test certificates with each shipment for independent verification at destination.
Q: Can I order mixed surface treatments in a single shipment?
A: Yes, we consolidate black painted, galvanized, and bare tubes within the same container order. Each surface treatment is packaged separately with appropriate protection to prevent coating damage during transit.
