Description
Factory-Direct S235/S355 Welded Square Steel Tube — Every batch shipped with original mill test certificates and CE marking per EN 10219, eliminating middleman markups and customs delays.
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 | ASTM, EN 10219, EN 10210 |
| 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) |
| Technique | Welded ERW |
| Surface Treatment | Pre-galvanized / Hot-dipped galvanized / Bare / Oiled |
| Tolerance | ±1% |
| Ends | Plain (default) |
| Invoicing | By Theoretical Weight |
| Application | Steel structures / Construction frames / Machinery / Scaffolding / Furniture / Building material |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, scaffolding systems, structural columns, roof trusses |
| Machinery Manufacturing | Conveyor frames, equipment support structures, machine bases |
| Steel Trading & Wholesale | Multi-specification bulk stock for regional distribution |
| Commercial Building | Furniture frameworks, interior structural partitions, facade supports |
What Missing CE Certificates Cost on an EN 10219 Square Tube Order
A single missing CE mark can hold an entire container at EU customs for weeks.
Importers sourcing S235/S355 welded square steel tube for European projects frequently discover — after the cargo arrives — that the supplier’s EN 10219 compliance was self-declared without third-party verification. The result: customs holds, demurrage charges, and project delays that dwarf the original price difference between a certified and uncertified supplier. Beyond customs, engineers specifying EN 10219 cold-formed hollow sections require full material traceability by heat number, something that generic “mill certificates” from unverified sources simply cannot provide [NEED_CITE: EN 10219 cold-formed hollow section compliance requirements for EU market access].
Matching S235/S355 ERW Square Tube to Structural Frame Requirements
S235 and S355 grades under EN 10219 serve distinct load-bearing tiers in structural frames. S235 welded square steel tube handles standard commercial building loads — partitions, mezzanine supports, light scaffolding — where yield strength requirements stay moderate. When projects escalate to industrial warehouses, crane runways, or seismic-zone structures, S355 becomes the baseline grade, delivering higher yield capacity without increasing section dimensions. The ERW welding process ensures consistent seam quality across the full 10×10 to 600×600 mm range, with in-house three-stage inspection covering weld formation, dimensional verification, and pre-shipment sampling. Our production lines run simultaneous ERW welding across multiple size brackets, meaning a single order mixing 50×50×3 scaffolding tubes and 300×300×12 structural columns ships from one coordinated batch.
Engineering Compliance Across EN 10219, EN 10210, and ASTM Frameworks
Structural engineers specifying hollow sections typically reference EN 1993-1-1 for design calculations, but material delivery compliance falls under EN 10219 for cold-formed welded products or EN 10210 for hot-finished equivalents. The distinction matters: EN 10219 permits cold-forming after welding, which affects corner mechanical properties and residual stress distribution compared to hot-finished profiles [NEED_CITE: differences between EN 10219 cold-formed and EN 10210 hot-finished hollow sections]. For projects requiring ASTM A500 Grade B or C, our S355 welded square steel tube meets equivalent chemical and mechanical thresholds, allowing procurement consolidation across European and North American specifications. Surface treatment selection — pre-galvanized for indoor structural work, hot-dipped galvanized for outdoor or high-humidity environments, bare with mill oil for painted finishes — directly influences long-term corrosion performance and maintenance intervals.
Understanding S235 vs. S355 Grade Selection and ERW Weld Integrity
The S-series designation under EN 10210/EN 10219 indicates minimum yield strength at nominal thickness: S235 delivers 235 MPa, S355 delivers 355 MPa. This grading system parallels the Chinese Q-series (Q235 ≈ S235, Q345 ≈ S355) and ASTM A500 Grade B/C, though exact chemical composition limits and impact testing requirements differ across standards [NEED_CITE: steel grade equivalence between EN 10219 S-series and GB Q-series]. ERW welded square tube production forms the section from coiled strip, welding the seam through high-frequency electric resistance — the process creates a heat-affected zone along the weld line that requires controlled cooling to maintain toughness. Wall thickness tolerance of ±1% applies across the 0.8–30 mm range, but buyers should note that theoretical weight invoicing assumes nominal dimensions; actual over-thickness increases piece weight without changing the billed quantity, while under-thickness risks structural non-compliance. Pre-galvanized coating (typically 40–80 μm) provides basic corrosion protection for indoor applications, while hot-dipped galvanizing (60–120 μm) covers all surfaces including the weld seam for outdoor structural exposure.
Hidden Costs of Welded Square Tube Procurement Errors
Specifying S235 when structural calculations demand S355 does not surface until load testing or inspector review — by then, replacement costs include not just new material but demolition, re-fabrication, and schedule penalties. Similarly, accepting welded square steel tube without verified mill test certificates creates downstream liability: if a project inspector requests heat-number traceability and the supplier cannot produce it, the entire batch becomes unusable regardless of actual material quality [NEED_CITE: consequences of missing material traceability in structural steel procurement]. Negative tolerance abuse — where actual wall thickness falls below the specified minimum — reduces load capacity and violates EN 10219 dimensional requirements, yet remains invisible without ultrasonic or caliper verification at receipt.
Why Procurement Teams Source S235/S355 Welded Square Steel Tube From Xinjiyuan
Our Jinan facility operates three dedicated ERW welding lines producing square and rectangular tubes from 10×10 mm to 600×600 mm, with monthly capacity exceeding 20,000 tons across 2,800+ stock specifications. Every S235/S355 welded square steel tube order ships with original mill test certificates documenting chemical composition and mechanical properties per heat number — not generic compliance statements. CE certification under EN 10210 and EN 10219 is maintained and auditable, with SGS or BV third-party inspection available before shipment for buyers requiring independent verification. Factory-direct pricing eliminates trading company margins, and volume discount programs activate for recurring procurement partners. Our export team handles container loading optimization — consolidating mixed-size square tube orders into minimal container counts — and manages full customs documentation including certificates of origin for preferential tariff markets.
Documentation & Compliance
- Mill test certificate documenting S235/S355 chemical composition and yield strength per EN 10219, traceable by heat number
- CE certificate covering EN 10210 and EN 10219 compliance for EU market access and project specification approval
- ISO 9001:2015 quality management certificate covering production process and inspection procedures
- SGS or BV third-party inspection report available upon request for independent pre-shipment verification
- Material traceability documentation linking each bundle to specific heat numbers and production dates
- Full customs document package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- S235/S355 welded square steel tube bundled with steel strips and edge protectors to prevent coating damage during ocean transit
- Pre-galvanized and hot-dipped galvanized surfaces wrapped with waterproof paper and plastic film to preserve zinc layer integrity
- Container loading plans optimized for 5.7 m and 6 m standard lengths, maximizing payload per 20ft or 40ft container
- Bare or oiled tubes bundled with anti-rust paper interlayers for humidity protection during extended storage or transit
- Each bundle labeled with heat number, steel grade (S235/S355), section dimensions, and wall thickness for site identification
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination for project sites
Start Your S235/S355 Welded Square Steel Tube Inquiry
Submit your section dimensions, wall thickness, steel grade, surface treatment preference, and destination port — our team responds within 12 hours with factory-direct pricing, production lead time, and available mill test certificate formats. For non-standard sizes outside the 10×10 to 600×600 mm range or custom lengths, share your drawing specifications for feasibility review and tooling assessment.
Request Factory-Direct Pricing With Mill Test Certificates
Send your specifications to admin@sdxinjiyuan.com or contact via WhatsApp at +86 188 5315 7756 for immediate quotation and CE/ISO certification copies.
Frequently Asked Questions
Q: How do S235 and S355 grades under EN 10219 compare to Q235/Q345 and ASTM A500?
A: S235 corresponds closely to Q235 in yield strength, while S355 aligns with Q345. ASTM A500 Grade B approximates S235, and Grade C approximates S355, though chemical composition limits and impact testing requirements vary across standards. We supply all three grading systems and can provide cross-reference documentation for your project specification.
Q: Do your CE certificates meet EU import and project compliance requirements?
A: Yes. Our CE certification covers both EN 10210 and EN 10219 standards, with Factory Production Control (FPC) audited by notified bodies. Every shipment includes CE marking documentation and original mill test certificates traceable by heat number, satisfying EU customs and structural engineering inspection requirements.
Q: Can you produce non-standard square or rectangular dimensions, and what is the MOQ?
A: We produce custom section sizes beyond the standard 10×10 to 600×600 mm range, subject to tooling feasibility and minimum tonnage per size. Standard specifications carry a 1-ton MOQ from ready stock; custom orders typically require higher minimum quantities depending on section complexity and steel grade.
Q: When should I specify hot-dipped galvanized versus pre-galvanized surface treatment?
A: Pre-galvanized coating (applied before tube forming) suits indoor structural applications with limited moisture exposure. Hot-dipped galvanizing (applied after forming) covers all surfaces including weld seams and corners, making it appropriate for outdoor structures, coastal environments, or high-humidity industrial settings where long-term corrosion resistance is critical.
Q: How is theoretical weight invoicing calculated, and what tolerance applies?
A: Invoicing by theoretical weight uses nominal dimensions and standard steel density (7.85 g/cm³) per EN 10219 formulas. Dimensional tolerance is ±1% across the size range. Actual weight may vary slightly from theoretical calculation, but billing remains based on nominal specifications regardless of measured over- or under-thickness within tolerance limits.
Get Your S235/S355 Welded Square Steel Tube Quote Today
Email your project specifications to admin@sdxinjiyuan.com or message +86 188 5315 7756 on WhatsApp — receive factory-direct pricing, available stock confirmation, and mill test certificate samples within 12 hours.
