Description
Factory-Direct ERW Square Tube Supply — S355JR 40x40x3mm hollow sections produced on our own ERW lines with original mill test certificates for every heat number.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S355JR ERW Welded Square Steel Tube |
| Product Type | ERW Welded Hollow Section — Square |
| Steel Grade | S235JR, S355JR, A36, SS400, Q235B |
| Standard | EN 10219, ASTM A500, JIS G3466, GB/T 6728 |
| Section Shape | Square |
| Side Length | 40×40 mm (4×4 inch) |
| Wall Thickness | 3 mm (12 Gauge) |
| Length | Customized per order |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Cold Rolled / Hot-Dip Galvanized (optional) |
| Tolerance | ±1% on dimensions |
| Ends | Plain (default) |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Invoicing | By Theoretical Weight |
| MOQ | 1 Ton (trial order accepted) |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, trusses, column supports, greenhouse structures |
| Machinery Manufacturing | Machine tool frames, conveyor supports, automation equipment bases |
| Commercial Fabrication | Stair handrails, security window frames, display racks |
| Vehicle Manufacturing | Trailer chassis, RV structural frames |
What ±1% Tolerance Means When 40×40 Frames Must Align on Site
A 1 mm deviation on a 40 mm side multiplies across every joint in a structural grid.
When procurement teams source S355JR ERW welded square steel tube from fragmented suppliers, dimensional inconsistency becomes the first failure point on site. Weld fit-up gaps widen, bolt holes misalign, and field crews waste hours grinding and re-fitting. Beyond geometry, material traceability gaps — missing heat numbers, unverifiable steel grades — trigger customs holds and third-party inspection rejections. [NEED_CITE: EN 10219 cold-formed welded hollow section dimensional tolerance requirements]
How 40×40×3mm ERW Square Tube Meets Structural Fabrication Demands
The 40×40 mm profile with 3 mm wall thickness occupies a practical range for light-to-medium structural frameworks — stiff enough to serve as load-bearing columns and truss members in greenhouse and canopy structures, yet compact enough for furniture frames and machinery bases. The ERW welding process produces a continuous longitudinal seam with consistent weld integrity, while the ±1% dimensional tolerance ensures that cut lengths mate cleanly during on-site assembly. For projects in corrosive environments, hot-dip galvanizing can be applied post-production, with coating thickness verified before dispatch. As a S355JR ERW welded square steel tube supplier, we ship every batch with mill test certificates tied to the original heat number.
Engineering Compliance and Certification Pathways
Structural applications governed by EN 1993 (Eurocode 3) require hollow sections conforming to EN 10219 or EN 10210 — our S355JR and S235JR grades meet these standards, with CE certification covering the EN 10219/10210 scope for European market entry. For North American projects specifying ASTM A500 Grade B or C, the A36 and equivalent grades in our range provide compliance without separate sourcing. [NEED_CITE: steel grade equivalence mapping between EN 10219 and ASTM A500] Third-party inspection through SGS or BV is available for pre-shipment verification, and our documentation package includes everything customs authorities require — from mill test certificates to certificates of origin. Custom cut-to-length service eliminates secondary cutting on site, reducing waste and labor costs for EPC contractors.
Steel Grade Selection and ERW Process Fundamentals
The S-series grades (S235JR, S355JR) follow the European EN standard system, where the number indicates minimum yield strength in MPa — S355JR delivers higher load-bearing capacity than S235JR, making it suitable for structural frames subject to greater stress. The Q-series (Q235B) and ASTM A36 represent Chinese and American equivalents respectively, commonly specified in domestic and North American projects. SS400, per JIS G3466, serves Japanese-standard projects across Southeast Asia. ERW welding involves forming steel coil into square profile and fusing the seam through electrical resistance — this method produces tight dimensional accuracy and smooth surface finish compared to SSAW, at lower cost than seamless alternatives for non-high-pressure applications. [NEED_CITE: ERW vs seamless vs SSAW steel tube manufacturing process comparison] Surface treatment selection depends on the service environment: cold rolled finish suits indoor or painted applications, while hot-dip galvanizing provides zinc coating protection for outdoor exposure, coastal structures, and agricultural buildings.
Hidden Costs of Sourcing the Wrong Grade or Missing Documentation
Specifying S235JR when structural calculations demand S355JR creates a latent safety risk — the lower yield strength may pass visual inspection but fail under design loads, exposing the project to structural failure and liability. Conversely, over-specifying S355JR for non-structural applications inflates material costs unnecessarily. Missing or incomplete mill test certificates cause customs delays at destination ports, particularly in markets with strict import verification — African and Middle Eastern authorities routinely hold shipments lacking proper documentation. [NEED_CITE: steel import documentation requirements for African and Middle Eastern customs] Negative tolerance abuse — where actual wall thickness falls below specification — reduces load capacity while invoicing remains on theoretical weight, a practice that transfers hidden cost to the buyer.
Why Procurement Teams Choose Our S355JR ERW Welded Square Steel Tube Supply
We operate three dedicated ERW production lines in Jinan, producing monthly capacity exceeding 20,000 tons — this factory-direct model eliminates trading margins and enables volume-based pricing for long-term partners. Every heat of steel carries an original mill test certificate documenting chemical composition and mechanical properties, traceable from coil to finished tube. Our inventory covers 2,800+ specifications across square, rectangular, round, and section steel categories, allowing consolidated container loading for multi-product project orders. CE certification under EN 10210/10219 and ISO 9001:2015 quality management ensure compliance for regulated markets, while SGS/BV third-party inspection is arranged on request. Custom lengths, non-standard dimensions, and processing services — cutting, punching, bending — are handled in-house, reducing lead times and secondary processing costs.
Documentation & Compliance
- Mill test certificate documenting S355JR chemical composition and yield strength per EN 10219, traceable to original heat number
- CE certificate covering EN 10219/EN 10210 cold-formed welded hollow sections for European customs clearance
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report available for pre-shipment verification of dimensions, coating thickness, and mechanical properties
- Material traceability documentation linking each bundle to its heat number and production batch
- Complete customs document package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- S355JR and S235JR square tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Galvanized 40x40x3mm tubes wrapped with waterproof material to preserve zinc coating integrity in humid conditions
- Container loading optimized for 40×40 mm profile — nested stacking maximizes payload per 20ft or 40ft container
- Custom cut-to-length service available, with bundles labeled by specification, steel grade, and heat number
- Plain-end tubes capped at both ends to prevent debris ingress; galvanized tubes coated with anti-fingerprint treatment
- FOB, CIF, and DDP shipping terms supported, with professional export team handling documentation and port coordination
How to Initiate Your S355JR ERW Welded Square Steel Tube Inquiry
Submit your specification requirements — including steel grade, dimensions, wall thickness, quantity, surface treatment preference, and destination port — and receive a detailed quotation within 12 hours. Our team provides mill test certificate samples, confirms certification requirements for your market, and coordinates third-party inspection scheduling. For project buyers requiring multi-category steel supply, we consolidate pipes, plates, beams, and fabricated components into shared containers, reducing logistics costs and simplifying procurement.
Request Your Factory-Direct Quotation Today
Send your specifications via email or WhatsApp to receive bulk pricing, lead time confirmation, and sample mill test certificates for your S355JR ERW welded square steel tube order.
Email: admin@sdxinjiyuan.com
WhatsApp: +86 188 5315 7756
