Description
Factory-Direct Bulk Supply — Every Q235 Q345 ERW square steel tube rolls off our own production lines in Jinan, shipped with original mill test certificates and no middleman markup.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345 ERW Square Steel Tube |
| Product Type | Square Steel Tube (ERW) |
| Steel Grade | Q195, Q215, Q235, Q345, S235JR, GR.B-D, STK500 |
| Standard | GB/T 3091, BS 1387, DIN EN 10025, EN 10219, JIS G3444, ASTM A53, BS EN 10255, API, ANSI B36.10M |
| Section Shape | Square |
| Size Range | 10 mm × 10 mm – 500 mm × 500 mm |
| Wall Thickness | 0.6 mm – 20 mm |
| Length | 1 m / 4 m / 6 m / 8 m / 12 m (or customized) |
| Technique | Hot Rolled / Cold Rolled ERW |
| Surface Treatment | Bare, Oiled, 3PE Coating, Printed, or Customized |
| Tolerance | ±1%, ±5%, ±10% |
| Ends | Plain, Beveled, Threaded with Couplings/Sockets |
| Application | Steel structures, Construction frames, Machinery, Scaffolding, Furniture, Fluid pipe, Gas pipe |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, bridge support columns, warehouse portal frames |
| Machinery Manufacturing | Conveyor structures, equipment bases, crane boom sections |
| Scaffolding & Shoring | Scaffold uprights, cross braces, formwork support systems |
| Furniture & Interior | Display rack frames, mezzanine structures, industrial shelving |
What Negative Wall Tolerance Really Costs on a 500mm Square Tube Order
A 1.2mm shortfall on a 12mm wall turns a 20-ton shipment into a 19-ton weight gap at destination port.
I watched a Nigerian bridge project stall for three weeks because the ERW square tubes arrived at Lagos with wall thickness measuring 10.8mm instead of the specified 12mm. The third-party inspector flagged it, customs held the containers, and the contractor had to air-freast replacement brackets just to keep the crane schedule alive. When you source a Q235 Q345 ERW square steel tube supplier who tolerates aggressive negative偏差, that weight difference compounds across every piece in the bundle — and your project budget absorbs the loss, not the mill. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching Structural Load Paths in Belt & Road Frame Assemblies
Our 500×500mm Q345 sections carry the primary vertical loads in warehouse portal frames across Southeast Asia, while the 100×100mm Q235 tubes handle secondary bracing where weldability matters more than yield strength. The ERW seam runs straight along the flat face, giving fabricators a predictable weld joint when gusset plates meet the tube corner — no hidden seam orientation surprises during on-site bolting.
Engineering Compliance Across EN, ASTM, and GB Frameworks
A Q235 Q345 ERW square steel tube supplier serving mixed-standard projects must map grade equivalence correctly: Q235 aligns with S235JR for European portal frames under EN 1993, while Q345 covers AISC-compatible structures where higher yield is specified. Our in-house lab tests every heat against the chemical composition limits in EN 10219 and GB/T 3091, then issues certificates that satisfy both EU notified bodies and African port customs inspectors. [NEED_CITE: steel grade equivalence mapping between GB Q-series and EN S-series]
Why ERW Weld Seam Integrity Defines Square Tube Performance
The electric resistance welding process fuses the steel strip edges under heat and pressure without filler metal, creating a seam whose tensile strength matches the parent material when properly controlled. For Q345 grades running at 12mm wall thickness, the cold-rolling pass before welding ensures the corner radius stays tight — critical when your structural engineer specifies sharp-corner geometry for moment-resisting connections. Hot-rolled ERW handles the heavier 16–20mm walls where forming force matters, while cold-rolled delivers the dimensional accuracy scaffolding contractors demand on 2–6mm sections.
The Hidden Price of Unverified Mill Certificates
When a shipment arrives without heat-number traceability or shows chemical composition outside the S235JR carbon equivalent limit, the engineer cannot sign off on the structural steelwork — period. You face re-inspection costs, potential re-melting orders with 45-day lead times, and liquidated damages from the main contractor. Choosing a Q235 Q345 ERW square steel tube supplier who provides SGS-verified mill test certificates before loading eliminates that risk entirely. [NEED_CITE: structural steelwork acceptance criteria requiring traceable mill certificates]
Why Project Buyers Keep Coming Back for Repeat Orders
We run three production lines simultaneously, holding 2,800+ specifications in ready stock so your 40-foot container of 200×200×6mm Q235 tubes ships within days, not weeks. Every bundle carries your heat-number stencils, and our export team consolidates mixed-size loads to maximize container payload — we once fitted 27 tons of 500×500mm Q345 plus 100×100mm Q235 bracing tubes into a single heavy-test container for a West African yard. Third-party inspection by SGS or BV happens at our facility before sealing, so you receive the report with the bill of lading.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition and yield strength per GB/T 3091 and EN 10219
- CE certificate confirming EN 10210/EN 10219 compliance for structural hollow sections exported to EU markets
- ISO 9001:2015 quality management certificate covering the full ERW production and inspection process
- SGS or BV third-party inspection report verifying wall thickness, dimensions, and surface quality before container sealing
- Heat-number traceability linking each bundle to its original slab chemistry and rolling records
- Customs documentation package including packing list, bill of lading, and certificate of origin for destination port clearance
Packaging, Loading & Delivery
- Bare Q235 square tubes bundled with steel strips and edge protectors to prevent corner dents during ocean transit
- Oiled surface treatment applied to cold-rolled ERW sections to inhibit rust formation during extended sea freight
- 3PE-coated Q345 tubes wrapped in waterproof sleeves before bundling to preserve the outer polyethylene layer
- Mixed-size container loading optimized by our export team — 6-meter 200×200mm tubes nested with 100×100mm sections to reach maximum payload
- Heat number and steel grade stenciled on every bundle end for on-site identification and traceability
- FOB Jinan/Qingdao, CIF destination port, or DDP door-to-door delivery with full export documentation handling
Getting Your Bulk Quote Started
Send your specification list — section size, wall thickness, steel grade, quantity, and destination port — and we return a competitive bulk price with volume discount tiers within 12 hours. If your project requires non-standard lengths or custom end treatments, we confirm feasibility and lead time before you commit. You receive the mill test certificate template and third-party inspection scope for your approval before production begins.
Frequently Asked Questions
Q: How do I choose between Q235 and Q345 for my structural frame?
A: Q235 suits general construction and scaffolding where weldability and formability matter most. Q345 provides higher yield strength for primary load-bearing columns and beams in warehouses, bridges, and heavy machinery frames.
Q: What documents do I need for customs clearance at my destination port?
A: Every shipment includes the original mill test certificate, packing list, bill of lading, and certificate of origin. For EU markets, we add the CE certificate per EN 10210/EN 10219. SGS or BV inspection reports are available upon request.
Q: Can I order mixed sizes in one container to reduce freight cost?
A: Yes. Our export team designs loading plans that nest smaller sections inside larger ones, maximizing container payload. We handle mixed-grade, mixed-size orders from 1-ton trial quantities up to full-project bulk shipments.
Q: What surface treatment options work best for outdoor structural applications?
A: Bare tubes suit indoor or painted structures. Oiled treatment provides short-term rust protection during shipping. 3PE coating delivers long-term corrosion resistance for outdoor exposure, buried applications, or aggressive environments.
Q: How do you ensure wall thickness matches my specification?
A: Our in-house lab conducts three-stage inspection during production — at the strip edge, after welding, and on the finished tube. Every batch comes with original mill test certificates showing actual measured dimensions. Third-party SGS/BV inspection is available before loading.
Request Your Project Quote Today
Submit your Q235 Q345 ERW square steel tube specifications via email or WhatsApp, and receive a factory-direct bulk quotation with mill test certificate samples within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxinjiyuan.com
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
