Description
Factory-direct pricing, zero middlemen markup — every S355JR and Q235B ERW square tube ships at mill price with full volume discount tiers applied to your order.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S355JR / Q235B ERW Square Steel Tube |
| Product Type | ERW Square Steel Tube |
| Steel Grade | S355JR, Q235B |
| Standard | EN 10219, ASTM A500, GB/T 6728 |
| Section Shape | Square |
| Size Range | 20×20 mm – 400×400 mm |
| Wall Thickness | 1.5 mm – 16.0 mm |
| Length | 6 m, 12 m, or cut-to-length |
| Technique | Electric Resistance Welded |
| Surface Treatment | Black (mill finish), hot-dip galvanized, or pre-painted |
| Tolerance | Per EN 10219 / ASTM A500 |
| Ends | Plain ends, beveled on request |
| Application | Structural frames, scaffolding, machinery, construction |
| MOQ | 1 ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, column supports, roof trusses, curtain wall sub-structures |
| Scaffolding & Formwork | Scaffold uprights, ledger braces, shoring towers |
| Machinery & Equipment | Conveyor frames, machine bases, hydraulic support structures |
| Industrial Fabrication | Warehouse purlins, equipment platforms, guardrail posts |
| Solar & Energy Mounting | PV panel mounting structures, inverter support frames |
Where Negative Wall Tolerance Costs More Than the Tube Itself
A 5% wall-thickness shortfall on a 4 mm spec turns a 3.8 mm tube into a liability on any load-bearing frame.
I have watched entire container loads of ERW square tubes arrive at West African ports with wall thickness measured at the absolute floor of the tolerance band — technically legal on paper, but structurally compromised once bolted into a multi-storey scaffold. The buyer saved $0.03 per metre on the invoice and spent three weeks re-sourcing replacement material while his crane sat idle. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements] When you source an ASTM A500 ERW square steel tube supplier who measures every batch with ultrasonic gauges before loading, that $0.03 saving stops being a gamble.
How S355JR and Q235B Square Tubes Match Structural Frame Demands
S355JR delivers higher yield strength than Q235B, making it the default choice for load-bearing columns and moment-resisting frames where deflection limits are tight. Q235B remains cost-effective for secondary structures, bracing members, and non-critical scaffolding uprights across tropical and humid climates. Both grades weld cleanly with standard MIG and stick processes, and the ERW seam on our square tubes runs through automated eddy-current inspection so the weld line never becomes the weak point. Every ASTM A500 ERW square steel tube we ship carries a heat-number traceable back to the coil certificate.
Engineering Compliance and Certification Pathways
Structural engineers specifying EN 1993 (Eurocode 3) require hollow sections that conform to EN 10219 for cold-formed welded structural tubing — our S355JR tubes meet that standard and carry CE marking under EN 10210/10219. For North American projects calling for ASTM A500 Grade B or C, we supply to that exact specification with mill test certificates documenting chemical composition and mechanical results. [NEED_CITE: ASTM A500 cold-formed welded and seamless carbon steel structural tubing specification] Customs authorities in the EU, Middle East, and South America routinely hold shipments lacking proper CE or ISO documentation — we include full certification packages in every container so your clearance agent never has to call you for missing paperwork.
Understanding the Steel Grade and Welding Process
The S-series (S235, S275, S355) follows the European EN standard system where the number after the “S” indicates minimum yield strength in MPa — S355JR therefore guarantees a defined yield floor suitable for primary structural work. Q235B follows the Chinese GB system and sits at a lower yield tier, which is why it dominates the scaffolding and light-frame market where weight-to-cost ratio matters more than raw strength. The ERW process forms the tube by rolling a flat strip into a square profile and fusing the seam with high-frequency electric current — no filler metal, no slag, and a weld zone that is often stronger than the parent material when properly controlled. [NEED_CITE: difference between ERW and seamless steel tube manufacturing processes] Wall thickness tolerance on ERW square tubes directly affects theoretical weight calculations — a tube ordered at 4.0 mm that measures 3.6 mm across the batch loses roughly 10% of its load-bearing cross-section, even though it may still fall within a loosely interpreted tolerance band.
The Hidden Cost of Buying the Wrong Grade or Missing Paperwork
Specifying Q235B on a drawing that calls for S355JR will fail structural inspection the moment the engineer checks the mill test certificate — and by then the tubes are already cut, welded, and bolted into the frame. Missing CE certificates on a shipment bound for the EU mean the container sits at Rotterdam or Lagos accumulating demurrage charges while you scramble to obtain paperwork the supplier should have provided at origin. [NEED_CITE: structural steel compliance requirements for CE marking in construction] Tubes sourced without third-party inspection reports leave you with no recourse when batch testing reveals chemistry outside the grade specification — the cost of replacing an installed structural frame dwarfs the price difference between a verified ASTM A500 ERW square steel tube supplier and an unverified one.
Why Procurement Teams Source Square Tubes From Our Mill
We run three production lines simultaneously in Jinan with a monthly capacity exceeding 20,000 tons, meaning your order does not wait behind someone else’s — a critical advantage when project timelines compress. Our in-house laboratory tests every heat for chemical composition and mechanical properties before the tube leaves the mill, and the resulting mill test certificate travels with the shipment. We stock over 2,800 standard specifications so trial orders of 1 ton and full-container bulk orders ship from the same warehouse without production queue delays. Every container we load follows a documented loading plan — square tube layers separated by timber spacers, weight distributed to prevent shifting, and lashing points secured — because I learned the hard way that a crushed container of tubes at destination costs ten times more than spending an extra hour on the loading plan. [NEED_CITE: container loading best practices for heavy steel products] We also consolidate multi-product orders — square tubes, round pipes, H-beams, and plates — into a single container so you deal with one invoice, one set of shipping documents, and one delivery window.
Documentation & Compliance
- Mill test certificate documenting S355JR or Q235B chemical composition and mechanical properties per EN 10219 or GB/T 6728, traceable by heat number
- CE certificate covering EN 10210 and EN 10219 for European market structural compliance
- ISO 9001:2015 quality management certificate covering the full production and inspection process
- SGS or BV third-party inspection report available on request for pre-shipment verification
- Material traceability linking each tube bundle to its original coil heat number and test results
- Full customs documentation package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- S355JR and Q235B square tubes bundled with steel strip ties and edge protectors to preserve surface finish during ocean transit
- Galvanized square tubes wrapped with waterproof paper and padded separators to prevent zinc coating abrasion between layers
- Container loading optimized by size range — 20×20 to 100×100 mm tubes nested to maximize cubic utilization in a 20ft or 40ft container
- Cut-to-length service available for 6 m and 12 m standard lengths, with custom lengths produced to your project drawing
- Each bundle tagged with heat number, steel grade, size, and length for on-site identification and traceability
- FOB Jinan/Qingdao, CIF, or door-to-door DDP delivery coordinated by our export team with real-time shipment tracking
How to Move From Inquiry to Loaded Container
Send your specification sheet — steel grade, size, wall thickness, quantity, and destination port — and we return a detailed quotation with volume pricing, production lead time, and payment terms within twelve hours. If your project requires non-standard dimensions or custom lengths, we provide a feasibility review and sample arrangement before you commit to a production order. Once the deposit clears, you receive production updates, pre-shipment photos, and the complete documentation package ahead of the vessel departure.
Frequently Asked Questions
Q: Can you supply S355JR and Q235B square tubes in the same container?
A: Yes. We consolidate mixed-grade and mixed-size orders into a single container with separate bundle tagging, so your project receives all required sections in one shipment with unified documentation.
Q: What is the minimum order quantity for ERW square tubes?
A: Our flexible MOQ starts at 1 ton, which supports trial orders and sample verification before you commit to full-project volumes.
Q: Do your square tubes carry CE marking for European projects?
A: All S355JR square tubes produced to EN 10219 carry CE certification under EN 10210/10219, and the certificate is included in every shipment’s documentation package.
Q: How do you ensure wall thickness meets the specified tolerance?
A: Every production batch undergoes ultrasonic wall-thickness measurement at multiple points around the cross-section, and results are recorded on the mill test certificate issued for that heat.
Q: Can you provide third-party inspection before shipment?
A: SGS and BV inspection services are available on request — we coordinate the inspection date with your nominated surveyor and include the report in the shipping documentation.
[Request Your Quotation and Mill Test Certificate Today]
Submit your specifications — steel grade, dimensions, quantity, and destination — to receive factory-direct pricing and full material certification within twelve hours.
Email: admin@sdxinjiyuan.com | WhatsApp: +86 188 5315 7756 | Tel: +86 531 8573 6315
