Description
Factory-Direct ERW Square Tubes — Every S235JR cold-rolled section rolls through our in-house laboratory before dispatch, with full CE documentation prepared for EU customs clearance.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S235JR ERW Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube |
| Steel Grade | S235JR, S355, Q235B, A36, SS400 |
| Standard | BS, EN, GB, AISI, ASTM, DIN, JIS |
| Section Shape | Square |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Cold Rolled |
| Tolerance | ±1% |
| Oiled or Non-oiled | Non-oiled |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Delivery Time | 31–45 days |
| Invoicing | By Theoretical Weight |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Architecture | Building trusses, column frames, curtain wall steel framing, scaffolding structures |
| Machinery Manufacturing | Machine base frames, conveyor support structures, industrial equipment housings |
| Decorative & Interior | Contemporary furniture frames, minimalist partition systems, exposed structural elements |
| Infrastructure | Bridge handrail posts, sound barrier supports, solar panel mounting structures |
Where Dimensional Tolerance Decides Structural Alignment on Site
A ±1% cold-rolled tolerance keeps bolt-hole patterns matching across 12-meter runs of S235JR ERW welded square steel tube.
On a recent Southeast Asian warehouse project, the contractor specified square tubes for portal frames. The first batch arrived with wall thickness pushing the lower limit of negative tolerance — on paper it met the purchase order, but when the erector tried to bolt splice plates at 6-meter intervals, the cumulative drift meant every third connection needed reaming on site. That kind of tolerance stacking does not show up in the mill test certificate. It shows up in crane idle time and fitter overtime. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
How Cold-Rolled ERW Square Tubes Match Precision Structural Frames
Cold-rolled S235JR ERW welded square steel tube delivers the surface flatness and corner consistency that structural fabricators need when welding moment-resisting connections. The cold-rolling process compresses the surface after forming, which tightens the ±1% tolerance envelope and produces a finish that accepts paint or galvanizing without additional grinding. For curtain wall framing and machine base plates, this means the tube arrives ready for CNC punching and fillet welding — no straightening passes required. Our production lines cover over 2,800 section specifications, so non-standard aspect ratios for architectural facade grids can be rolled to order rather than forcing designers to adapt to catalog sizes.
Engineering Compliance and Certification Pathways
Structural engineers specifying S235JR under EN 10219 or A36 under ASTM A500 need documentation that travels with the shipment, not paperwork that arrives two weeks later. The S235JR grade conforms to EN 10025 for structural steel, while Q235B serves the same function under GB/T 700 for domestic Chinese projects — both are available from the same production run with separate mill test certificates. For EU market entry, CE marking under EN 10210 or EN 10219 is mandatory, and our Lloyd’s-registered CE certificates cover the full range of cold-formed hollow sections we produce. [NEED_CITE: CE marking requirements for structural steel hollow sections under CPR Regulation] Third-party inspection through SGS or BV can be arranged before container sealing, giving the buyer an independent verification point that satisfies both the engineer of record and the importing customs authority.
Steel Grade Selection and ERW Process Fundamentals
The S235JR designation indicates a minimum yield strength of 235 MPa at room temperature, with the JR suffix confirming 27 Joule Charpy impact energy at +20°C — adequate for most building frames in temperate climates. When the project moves to colder regions or heavier dynamic loading, S355 steps in with higher yield and improved low-temperature toughness. The ERW process forms the square section from cold-rolled coil through a continuous forming and resistance-welding sequence, producing a longitudinal weld seam that is then normalized to match the parent metal’s mechanical properties. Cold-rolled surface treatment follows the welding and sizing stages, compressing the outer skin to achieve the tight ±1% tolerance. This differs from hot-rolled hollow sections, which carry a mill scale finish and wider tolerance band — the cold-rolled variant suits applications where visible surface quality matters, such as exposed architectural frames or precision machinery guards. [NEED_CITE: comparison of ERW versus seamless versus SSAW manufacturing processes for structural tubes]
The Hidden Cost of Tolerance Drift and Certification Gaps
Ordering square tubes based on price per ton alone ignores what happens when the material reaches the fabrication shop. Wall thickness at the lower edge of negative tolerance reduces the section modulus, which means the structural engineer’s calculations assumed more capacity than the delivered product provides. Certification gaps create a different failure mode: a shipment without proper EN 10219 references or with mismatched heat numbers gets held at EU customs, triggering demurrage charges that exceed the original freight cost. [NEED_CITE: consequences of non-compliant steel documentation in EU construction imports] The true procurement cost includes the risk of re-welding, re-certifying, or scrapping material that looked acceptable on the invoice but failed the inspector’s caliper.
Why Fabricators and EPCs Source S235JR ERW Tubes From Our Mill
We produce the S235JR ERW welded square steel tube on three dedicated lines that cover wall thicknesses up to 40 mm — heavy enough for primary structural columns, not just secondary bracing. Every heat passes through our in-house physical and chemical laboratory before release, so the mill test certificate reflects actual test data rather than typical values. Our patented sharp-corner rectangular tube technology fills a gap that standard mills cannot address: true right-angle corners for architectural curtain walls where rounded radii create visual and connection problems. Full international certification — ISO 9001:2015, Lloyd’s CE under EN 10210 and EN 10219, Singapore FPC, and SGS/BV verification — means the paperwork matches the material, regardless of destination port. We have exported to over 50 countries, and our loading teams use custom cradles and edge protectors to prevent the surface damage that cold-rolled finishes are vulnerable to during ocean transit.
Documentation & Compliance
- Mill test certificate documenting S235JR chemical composition (C, Mn, Si, P, S) and yield strength per EN 10025-2, issued per heat number
- CE certificate registered through Lloyd’s Register, covering EN 10219 cold-formed structural hollow sections for EU market entry
- ISO 9001:2015 quality management certificate confirming systematic process control from coil intake through final inspection
- SGS or BV third-party inspection report available upon request, covering dimensional checks, weld seam integrity, and surface finish
- Material traceability linking each bundle to its heat number, with markings stenciled on both tube ends and bundle tags
- Full customs documentation package: commercial invoice, packing list, bill of lading, and certificate of origin formatted for destination requirements
Packaging, Loading & Delivery
- Non-oiled cold-rolled S235JR square tubes bundled with galvanized steel strips at intervals matched to the 6–12 meter length, preventing bundle shift during crane handling
- Edge protectors applied to all four corners of each bundle to preserve the cold-rolled surface finish against strap abrasion during ocean transit
- Container loading optimized for square section geometry, with timber dunnage separating layers to prevent contact damage and allow moisture drainage
- Heat number and steel grade stenciled on each tube end, with bundle tags showing section dimensions, wall thickness, length, and piece count for site identification
- FOB, CIF, and DDP terms available, with professional loading supervision at our Jinan facility ensuring weight distribution meets container floor-load limits
- Custom cutting to project-specific lengths available before shipment, reducing on-site waste and welding passes for the fabricator
Start Your Procurement With Verified Mill Data
Send your section dimensions, wall thickness, steel grade, and destination port — we return a detailed quotation with unit pricing, production lead time, and a sample mill test certificate within 12 hours. For non-standard sizes outside the 2,800+ catalog range, our engineering team confirms roll-tooling feasibility and delivery schedule. Third-party inspection and CE documentation requirements are confirmed at the inquiry stage, so there are no surprises at customs.
Frequently Asked Questions
Q: Can you provide mill test certificates for both EN and ASTM grade equivalents on the same order?
A: Yes. We issue separate mill test certificates for each standard designation — S235JR per EN 10025-2 and A36 per ASTM A500 — even when the material comes from the same production heat. The chemical composition and mechanical test results are documented against each standard’s specific requirements.
Q: What is the tolerance standard for your cold-rolled ERW square tubes?
A: Our S235JR ERW welded square steel tube is produced to ±1% dimensional tolerance, in accordance with EN 10219 requirements for cold-formed hollow sections. This tolerance covers outer dimensions, wall thickness, and straightness over the full piece length.
Q: Do you offer custom cutting and end preparation before shipment?
A: Yes. Processing services include cutting to specified lengths, punching for bolt connections, and end preparation for welding. These services are confirmed during the quotation stage, and the processing schedule is reflected in the production lead time of 31–45 days.
Q: Is third-party inspection available before container loading?
A: Yes. We arrange SGS or BV inspection at our facility before shipment. The inspection covers dimensional verification, surface quality assessment, weld seam examination, and review of mill test certificates. The inspection report is issued directly to the buyer.
Q: How do you handle invoicing — by actual weight or theoretical weight?
A: Our S235JR ERW welded square steel tube is invoiced by theoretical weight, calculated from the specified outer dimensions, wall thickness, and length using the standard density for carbon steel. This method provides pricing consistency regardless of minor tolerance variations within the ±1% band.
[Request Your S235JR ERW Square Tube Quotation With Mill Test Certificate]
Submit your section specifications, steel grade, quantity, and destination port to receive a detailed quotation and sample documentation within 12 hours.
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