Description
Factory-Direct SHS/RHS Supply — 3 production lines in Jinan running Q235B and Q345B square and rectangular steel tube with original mill test certificates on every heat.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Q345B Carbon Steel Square and Rectangular Tube |
| Product Type | Square and Rectangular Steel Tube (SHS / RHS) |
| Steel Grade | Q195, Q215, Q235, Q345 (Q355), #20, #45; Equivalent: S195, S235JR, S355JR, A53 Grade A/B, A500 Grade A/B/C, STK400, SS400, ST42.2, S355J2H, S355J0H |
| Standard | EN 10219, EN 10210, GB/T 6728, JIS G3466, ASTM A500, ASTM A53, ASTM A36, ASTM A106 |
| Section Shape | Square / Rectangular / Round |
| Size Range | Square: 20×20 mm – 500×500 mm; Rectangular: 20×40 mm – 300×500 mm |
| Wall Thickness | 0.5 – 30 mm (1.2 – 20 mm for welded sections) |
| Length | 3 – 12 m (random or fixed) |
| Technique | Hot Rolled / ERW / Seamless |
| Surface Treatment | Hot Rolled, Pre-galvanized (40–80 g/m²), Hot-dip Galvanized (200–600 g/m²), Black / Oiled / Custom |
| Tolerance | ±1% |
| Ends | Plain / Beveled / Custom |
| Application | Construction structures, solar mounting, machinery, shipbuilding, greenhouse, fence, power engineering, highway railings, bridges |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, bridge girders, highway railings, solar mounting structures |
| Industrial & Machinery | Equipment frames, pressure vessels, lifting structures, conveyor supports |
| Agricultural & Commercial | Greenhouse frames, fence posts, warehouse portal frames |
When Q235B and Q345B Land on the Same Drawing, Which Grade Actually Ships
Substituting Q235B for Q345B on a load-bearing frame does not show up until the structure deflects under service load.
Procurement teams frequently receive drawings specifying Q345B (S355JR) for primary columns and Q235B (S235JR) for secondary bracing — then discover the supplier has shipped a single grade across the entire order to simplify production. The result is either over-specification cost on bracing members or, worse, under-strength columns that fail third-party inspection on site. A Q235B Q345B square and rectangular steel tube supplier must be able to segregate grades by heat number, provide separate mill test certificates for each, and map Chinese GB grades to EN and ASTM equivalents so that customs and engineering reviewers accept the documentation without delay [NEED_CITE: steel grade equivalence between EN and ASTM standards].
Matching Wall Thickness and Section Size to Structural Load Paths
A 200×200×8 mm Q345B SHS carries a fundamentally different load than the same section in Q235B — the grade difference alone changes the design resistance by roughly 50 percent. On solar mounting structures and greenhouse frames, thin-wall ERW tubes (0.5–3 mm) in Q235B keep material cost low where wind load governs and seismic demand is minimal. On building frames and bridge parapets, hot-rolled seamless or heavy-wall ERW sections in Q345B at 8–30 mm wall thickness meet the yield requirements of EN 1993 and AISC 360 without upsizing the section. The Q235B Q345B square and rectangular steel tube range from 20×20 to 500×500 mm covers both categories from a single purchase order, with grade segregation enforced at the mill test stage.
Compliance Requirements Across Export Markets
EU project specifiers require CE marking under EN 10210 (hot-rolled) or EN 10219 (cold-formed welded) — without the Declaration of Performance, the container sits at Rotterdam or Hamburg until the importer posts a bond or arranges re-certification. North American buyers reference ASTM A500 Grade B/C for structural hollow sections and ASTM A53 for line applications; the chemical composition and tensile requirements differ from GB/T 6728, so a mill test certificate written to the Chinese standard alone will not satisfy the engineer of record [NEED_CITE: EN 10219 cold-formed hollow section requirements]. Australian and Middle Eastern tenders frequently call for AS/NZS 1163 or JIS G3466 equivalence, which the Q235B/Q345B grade family covers through S235JR/S355JR and STK400/SS400 mappings. Third-party inspection by SGS or BV before shipment closes the gap between mill output and site acceptance.
Grade Equivalence and Production Process Explained
Q235B maps to S235JR (EN) and roughly to ASTM A36/A53 Grade A; Q345B (now designated Q355B under the updated GB standard) maps to S355JR/S355J2H and aligns with ASTM A500 Grade B/C. The yield step from 235 MPa-class to 355 MPa-class matters most on compression members and moment-resisting frames, where the higher grade allows smaller sections and lighter tonnage per meter. ERW production suits thin-wall to medium-wall SHS and RHS up to approximately 20 mm, while seamless and hot-rolled processes handle the heavy-wall range (8–30 mm) where weld-line integrity under cyclic loading becomes a concern. Surface treatment choice follows the corrosion environment: black or oiled for indoor structural frames, pre-galvanized (40–80 g/m²) for covered agricultural structures, and hot-dip galvanized (200–600 g/m²) for outdoor highway railings, solar mounts, and coastal installations where salt spray governs design life. Sharp-corner rectangular tubes, produced on dedicated forming passes, improve connection fit-up on bolted moment joints and give cleaner visual lines on exposed architectural frames.
The Real Cost of Shipping the Wrong Grade or Missing Paperwork
A container of Q345B tubes that tests as Q235B at the destination does not just fail acceptance — it forces the contractor to either re-procure at air-freight cost or redesign the structure with the lower grade, which usually means thicker sections, more welding, and a delayed handover. Missing CE documentation on an EU-bound shipment triggers customs holds that run into weeks; missing mill test certificates on an ASTM-specified order means the engineer will not sign off on the structural steel submittal. Tolerance abuse on wall thickness (beyond the stated ±1 percent) erodes section modulus and reduces fire resistance ratings, a defect that only surfaces during destructive testing at the lab stage — long after the tubes have been cut and welded [NEED_CITE: structural steel tolerance requirements EN 10219].
Why Buyers Return for Repeat Orders
Every heat of Q235B and Q345B tube leaving Jinan passes through an in-house laboratory that checks yield, tensile, and impact properties against the mill certificate before the container is sealed — a step that catches grade mix-ups before they become site failures. The factory runs three production lines simultaneously with monthly capacity above 20,000 tons, covering over 2,800 stock specifications so that standard sizes ship within days rather than weeks. MOQ starts at 1 ton for trial orders and scales to full-container bulk shipments, with split-shipment flexibility for projects drawing down stock over multiple months. CE certification under EN 10210 and EN 10219, ISO 9001:2015 registration, and SGS/BV third-party inspection on request satisfy the documentation requirements of EU, Middle Eastern, and Southeast Asian tenders. Professional export handling covers container loading optimization for mixed-size orders, complete customs documentation, and door-to-door logistics coordination — reducing the number of counterparties a buyer manages from five to one.
Documentation & Compliance
- Mill test certificate documenting Q235B or Q345B chemical composition and mechanical properties per GB/T 6728, with EN/ASTM equivalence noted
- CE certificate covering EN 10210 hot-rolled and EN 10219 cold-formed welded hollow sections, with Declaration of Performance
- ISO 9001:2015 quality management certificate covering production and inspection processes
- SGS or BV third-party inspection report available per heat, covering dimensional check, visual inspection, and witness testing
- Full material traceability by heat number from slab to finished tube, linked to the mill test certificate
- Export customs documents including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Black and oiled Q235B/Q345B tubes bundled with steel strips and edge protectors, sized to suit 20ft and 40ft containers based on the 3–12 m length range
- Pre-galvanized and hot-dip galvanized RHS separated by coating class with interleaving protectors to prevent zinc surface damage during ocean transit
- Mixed-size container loading plans optimized for SHS and RHS combinations, maximizing payload per container while keeping individual bundle weights within crane and forklift limits
- Fixed-length cutting to project-specified dimensions within the 3–12 m range, with each bundle marked by heat number, steel grade, and section size
- FOB, CIF, and DDP shipping terms available from Chinese ports to destination, with full export documentation and real-time shipment tracking
Getting a Firm Quote with Mill Test Documentation
Send the section size, wall thickness, steel grade (Q235B or Q345B or equivalent EN/ASTM designation), total tonnage, and destination port — a detailed quotation with volume pricing, production lead time, and payment terms follows within 12 hours, together with a sample mill test certificate format for the specified grade and standard.
Request Your Quotation and Mill Test Certificate
Submit your specification list by email or WhatsApp to receive pricing, certification documents, and container loading plans for your Q235B Q345B square and rectangular steel tube order.
Email: admin@sdxinjiyuan.com | WhatsApp: +86 188 5315 7756
Frequently Asked Questions
Q: How do Q235B and Q345B map to European EN and American ASTM steel grades?
A: Q235B corresponds to S235JR under EN standards and is broadly equivalent to ASTM A36 and A53 Grade A. Q345B (Q355B) corresponds to S355JR or S355J2H under EN standards and aligns with ASTM A500 Grade B/C. Mill test certificates note the equivalence for cross-standard procurement.
Q: Do you provide original mill test certificates and accept third-party inspection?
A: Every shipment includes an original mill test certificate covering chemical composition and mechanical properties per the applicable standard (GB/T 6728, EN 10219, or ASTM A500). SGS and BV third-party inspection is available on request before shipment.
Q: Can you produce non-standard dimensions with a low trial order quantity?
A: Standard sizes from 20×20 mm to 500×500 mm are held in ready stock. Non-standard dimensions and custom lengths within the 3–12 m range are produced to order, with a minimum order quantity of 1 ton for trial purposes.
Q: Which surface treatment should I specify for my project environment?
A: Black or oiled finish suits indoor structural frames; pre-galvanized (40–80 g/m²) fits covered agricultural and warehouse structures; hot-dip galvanized (200–600 g/m²) is recommended for outdoor applications exposed to moisture or salt spray, such as solar mounts, highway railings, and coastal installations.
Q: How do you handle container loading for mixed-size tube orders?
A: The export team prepares a loading plan that combines SHS, RHS, and round sections in one container, optimizing weight distribution and cube utilization. Each bundle is marked with heat number and grade for easy identification at the destination.
Get Your Project Priced with Full Certification
Share your size list, grade requirement, and destination — receive a quotation with mill test certificate samples and a container loading plan within 12 hours.
Email: admin@sdxinjiyuan.com | WhatsApp: +86 188 5315 7756
