Description
Mill-Direct S355 ERW Tubes — vertically integrated production from raw slab to finished SHS/RHS eliminates third-party sourcing gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S235/S355 Welded Square Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (SHS/RHS) |
| Steel Grade | Q195, Q215, Q235, Q345, GR.A, GR.B, S235, S355 |
| Standard | EN 10219, EN 10210, GB/T 6728, JIS G3466, ASTM (supplier-declared) |
| Section Shape | Square / Rectangular |
| Size Range | 10×10 mm – 600×600 mm |
| Wall Thickness | 0.8 – 30 mm |
| Length | 5.7 m / 6 m (standard); customizable |
| Technique | Welded ERW |
| Surface Treatment | Pre-galvanized / Hot-dipped galvanized / Bare / Oiled |
| Tolerance | ±1% |
| Invoicing | By Theoretical Weight |
| Application | Steel structures, construction frames, machinery, scaffolding, furniture, infrastructure projects, industrial platforms |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial Construction | Building frames, column supports, beam assemblies for multi-story structures |
| Industrial Facilities | Warehouse roof trusses, mezzanine platforms, conveyor support frames |
| Infrastructure | Bridge handrail posts, sound barrier columns, solar panel mounting structures |
| Machinery & Equipment | Crane boom sections, hydraulic press frames, agricultural machinery chassis |
| Scaffolding & Access | Load-bearing scaffolding uprights, temporary structure bracing |
What Negative Tolerance Costs on a 600mm SHS Order
A wall thickness running 6.8mm instead of 8mm means the entire container gets rejected at site inspection.
Overseas buyers sourcing S235 S355 welded square steel tube from fragmented suppliers face a recurring problem: mill certificates look clean on paper, but actual wall thickness drifts deep into negative tolerance. When a Middle East contractor received 200×200×8mm welded square tubes for a warehouse project, their on-site inspector caught wall thickness at 6.8mm — the whole shipment failed acceptance. Rework and replacement cost double the original material price. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed welded hollow sections]
Beyond wall thickness, missing or falsified MTCs create customs clearance delays in EU markets where EN 1090 CE marking is mandatory. Fragmented procurement — buying tubes from one trader, having them fabricated elsewhere — breaks the material traceability chain that auditors demand.
Matching Section Dimensions to Structural Load Paths
S235 S355 welded square steel tube in the 10×10 to 600×600mm range covers everything from light-gauge furniture frames to heavy-duty industrial column sections. The 0.8–30mm wall thickness span means a single supply source can handle both non-structural cladding supports and primary load-bearing members. For EPC projects across the Middle East and Southeast Asia, having one manufacturer produce both the 50×50×3mm bracing tubes and the 400×400×16mm main columns under the same quality system eliminates grade mixing errors at the fabrication yard.
Engineering Compliance Across International Standards
Structural frames designed to EN 1993 require hollow sections conforming to EN 10219 or EN 10210, with full CE marking for EU market entry. S235 S355 welded square steel tube produced under these standards carries certified weld procedures (WPS/PQR) and in-process NDT testing that satisfies third-party inspectors from SGS, BV, or TÜV. [NEED_CITE: EN 10219 cold-formed welded hollow section structural requirements] For projects targeting North American specs, ASTM A500 Grade B/C equivalence can be confirmed through chemical composition cross-reference. The ±1% dimensional tolerance ensures shop drawings match as-delivered sections, preventing fit-up problems during bolted or welded connections.
Understanding ERW Weld Quality and Grade Selection
The ERW (Electric Resistance Welding) process forms square and rectangular sections by cold-bending steel strip and welding the seam under pressure — producing a continuous weld bead that runs the full tube length. S235 and S355 designations follow the European EN system where the number indicates minimum yield strength in MPa; S355 delivers higher load capacity than S235, making it the preferred choice for primary structural members. [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500 standards] The Q-series grades (Q235, Q345) follow Chinese GB/T 6728 standards and remain widely specified across Belt & Road infrastructure projects. Surface treatment selection depends on the installation environment: pre-galvanized tubes suit indoor or moderate corrosion conditions, hot-dipped galvanized sections handle coastal or industrial atmospheres, while bare or oiled tubes work for applications where field welding or post-fabrication coating is planned.
Hidden Costs of Unverified Material Procurement
Purchasing S235 S355 welded square steel tube without verified MTCs or third-party inspection creates cascading project risks. Material that fails dimensional checks at the destination port triggers customs holds, demurrage charges, and potential rejection. Welding procedures qualified for S355JR will not perform identically on off-grade material with unexpected carbon equivalent values — creating structural safety concerns that only surface during load testing or, worse, after project handover. [NEED_CITE: material traceability requirements for structural steel in EN 1090 execution classes]
Why Project Teams Source From Our Mill
Our vertically integrated operation combines raw steel production with dedicated structural tube fabrication — meaning the same facility that rolls the coil also forms, welds, and inspects the finished S235 S355 welded square steel tube. Every heat number traces back to the original slab chemistry, and our in-house laboratory issues EN 10204 3.1/3.2 mill test certificates before shipment. With over 2,800 specification combinations in inventory, we consolidate mixed-size orders into single-container shipments, reducing per-ton freight costs for projects requiring both small-bore bracing and large-section columns. Ultrasonic testing on every batch catches wall thickness deviations before loading — the same inspection protocol that prevents the 6.8mm-versus-8mm rejection scenario. Professional packing with edge protectors preserves galvanized coatings during ocean transit, while custom cutting to exact project lengths minimizes on-site waste.
Documentation & Compliance
- Mill test certificate documenting S235JR or S355JR chemical composition and mechanical properties per EN 10219, traceable by heat number
- CE certificate confirming EN 10210/EN 10219 compliance for structural hollow sections entering EU markets
- ISO 9001 quality management certification covering both steel production and tube fabrication processes
- SGS or BV third-party inspection reports available for pre-shipment dimensional and coating thickness verification
- Full material traceability linking each tube bundle to its original heat number and rolling record
- Export documentation package including packing list, bill of lading, and certificate of origin for customs clearance
Packaging, Loading & Delivery
- S235 S355 welded square steel tube bundled with high-tensile steel strips and edge protectors to prevent coating damage during handling
- Hot-dipped galvanized sections wrapped with waterproof paper and secured on wooden skids to preserve zinc layer integrity during ocean freight
- Mixed-size container loading optimized for 6m standard lengths, with smaller sections nested inside larger SHS/RHS to maximize payload per shipment
- Custom cut-to-length service available for projects requiring non-standard lengths, with kerf allowance calculated per order
- Each bundle labeled with heat number, steel grade, section dimensions, and wall thickness for immediate site identification
- FOB, CIF, and DDP shipping terms supported with complete export documentation and door-to-door tracking for project sites across the Middle East, Southeast Asia, and Africa
Requesting Quotation and Technical Review
Submit your project drawings (PDF/DWG), required steel grades, section dimensions, wall thickness, surface treatment preference, and destination port to receive a detailed quotation including material cost, fabrication charges, coating fees, and freight estimates. Our engineering team reviews shop drawings within 24 hours and confirms production scheduling based on approved specifications.
Start Your S235 S355 Welded Square Steel Tube Order
Share your project specifications and required quantities to receive pricing with full mill test certificates.
Company: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
Frequently Asked Questions
Q: What is the difference between S235, S355, and Q235 steel grades?
A: S235 and S355 follow the European EN standard system where the number indicates minimum yield strength in MPa. Q235 follows the Chinese GB/T system and is roughly equivalent to S235 in mechanical properties. For projects requiring higher load capacity, S355 provides greater yield strength than both S235 and Q235.
Q: Can you provide third-party inspection before shipment?
A: Yes, we accept SGS, BV, and TÜV third-party inspections for dimensional checks, coating thickness measurement, and visual weld inspection. The inspection report is issued before container loading and included in the shipping documentation package.
Q: What is the minimum order quantity for custom sizes?
A: The MOQ is 1 Ton. We can produce non-standard section dimensions and custom lengths beyond the standard 5.7m or 6m, subject to production scheduling confirmation.
Q: How do you ensure wall thickness meets the specified tolerance?
A: Every production batch undergoes ultrasonic thickness testing at multiple points along the tube length. Results are recorded in the mill test certificate. Our ±1% dimensional tolerance ensures the delivered wall thickness matches the ordered specification within acceptable limits.
Q: What surface treatment options are available for corrosive environments?
A: We offer pre-galvanized coating for moderate protection, hot-dipped galvanizing for heavy-duty corrosion resistance in coastal or industrial atmospheres, and bare/oiled finishes for applications requiring field welding or post-fabrication painting.
