Description
Factory-Direct ERW Production — Three dedicated lines with in-house physical and chemical laboratories ensure every S235/S355 welded square steel tube meets dimensional and chemical requirements before shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S235/S355 Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q345, GR.A, GR.B, S235, S355 |
| Standard | ASTM, ISO 9001, CE, BSI, BIS, JIS, GS |
| Section Shape | Square |
| Size Range | 10×10 – 600×600 mm |
| Wall Thickness | 0.8 – 30 mm |
| Length | 5.7 m / 6 m (standard) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Pre-galvanized / Hot-dipped galvanized / Bare / Oiled |
| Tolerance | ±1% |
| Invoicing | By theoretical weight |
| Alloy | Non-alloy |
| Application | Steel structures / Construction frames / Machinery / Scaffolding / Furniture / Pipeline / Industrial fabrication |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Steel structure frames for industrial plants and warehouse projects |
| Construction Companies | High-rise building columns, beam supports, and scaffolding systems |
| Machinery Manufacturers | Equipment bases, conveyor structures, and hydraulic frame components |
| Infrastructure Developers | Bridge support members and pipeline casing for underground utilities |
What Negative Tolerance Costs on a Structural Frame Order
A 0.4 mm wall deviation on a 3.0 mm specified tube can void an entire batch at port inspection.
Early in my procurement career, I watched a twenty-thousand-dollar welded square steel tube order get rejected at destination because the actual wall measured 2.6 mm against a 3.0 mm contract spec. The supplier called it “within industry practice.” The client’s engineer called it a compliance failure. When you source a S235/S355 welded square steel tube for load-bearing frames, theoretical weight invoicing only works if the tolerance stays within ±1% and the mill test certificate reflects actual chemistry and dimensions. Missing certifications or unverified negative tolerance do not just delay customs — they shift structural liability onto the buyer [NEED_CITE: EN 10219 cold-formed welded structural hollow sections tolerance requirements].
Matching ERW Square Tubes to Structural and Scaffolding Loads
ERW welded square steel tubes in S235 and S355 grades carry load through closed-section geometry, where the square profile distributes stress across four flat faces and corner radii. For scaffolding and construction frames, the 10×10 to 600×600 mm range covers everything from light-duty furniture frames to heavy industrial column members. Wall thickness from 0.8 mm to 30 mm lets engineers match section modulus to calculated loads without over-specifying material. Surface treatment selection — bare and oiled for indoor structural use, pre-galvanized for moderate corrosion environments, hot-dipped galvanized for outdoor exposure — determines service life without adding secondary coating costs.
Engineering Compliance and Certification Requirements
Structural steel procurement for EU projects requires CE marking under EN 10210 or EN 10219, which governs cold-formed welded structural hollow sections of S235 and S355 grades. North American buyers reference ASTM A500 for equivalent mechanical and chemical requirements. The S235/S355 welded square steel tube we produce carries CE certification, ISO 9001:2015 quality management, and Singapore FPC approval for Southeast Asian infrastructure tenders. Every heat number is traceable through our in-house laboratory, and third-party inspection by SGS or BV is available before shipment. For projects requiring specific length cuts or non-standard dimensions beyond the 5.7 m and 6 m standard, custom sizing is available with confirmed lead times [NEED_CITE: steel grade equivalence mapping between EN 10219 and ASTM A500 standards].
Understanding ERW Welding and Steel Grade Selection
The ERW (Electric Resistance Welded) process forms the square profile by cold-rolling steel strip into shape and welding the seam through electrical resistance heating — no filler metal, no flux. This produces a consistent weld seam suitable for structural applications where the S235/S355 welded square steel tube must maintain uniform strength around the entire cross-section. Steel grade selection follows project specification: S235 offers lower yield strength suitable for non-critical frames and furniture, while S355 provides higher yield for load-bearing columns and machinery bases. The Chinese GB equivalents Q235 and Q345 follow the same progression, and GR.A/GR.B grades serve marine and pipeline environments. Wall thickness tolerance of ±1% ensures that theoretical weight invoicing aligns with actual material delivered, preventing the cost overruns that come from uncontrolled negative tolerance.
Hidden Costs of Unverified Material and Missing Documentation
Purchasing a S235/S355 welded square steel tube without original mill test certificates risks customs rejection in EU and North American ports, where CE marking and chemical composition documentation are mandatory. Material that fails to meet the specified steel grade — whether through substitution or uncontrolled chemistry — forces on-site rework, weld procedure requalification, or complete member replacement. Negative tolerance beyond ±1% reduces actual load capacity below engineering calculations, creating structural safety concerns that surface only during inspection or under load. Certification gaps do not just delay projects; they transfer liability from supplier to buyer [NEED_CITE: consequences of non-compliant structural steel in construction projects].
Why Project Procurement Teams Source From Our Facility
We operate three dedicated ERW production lines covering 2,800+ specifications in square and rectangular profiles, with wall thickness reaching 30 mm. Our in-house physical and chemical laboratory tests every heat for composition and mechanical properties before the S235/S355 welded square steel tube leaves the mill. We hold 41 invention patents, including proprietary sharp-corner rectangular tube technology that eliminates the radius gap problem in structural connections. Factory-direct pricing means no trading margins, and our export team manages documentation, container optimization, and door-to-door logistics to 50+ countries. Custom non-standard sizes, special packaging, and third-party inspection coordination are handled in-house rather than outsourced.
Documentation & Compliance
- Mill test certificate documenting S235/S355 chemical composition and mechanical properties per EN 10219 or ASTM A500
- CE certificate under EN 10210/EN 10219 for structural hollow sections exported to European Union markets
- ISO 9001:2015 quality management system certificate covering ERW welded square steel tube production
- SGS or BV third-party inspection report available upon request for critical project verification
- Material traceability by heat number linking each S235/S355 welded square steel tube bundle to laboratory test results
- Complete customs documentation including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- S235/S355 welded square steel tubes bundled with steel strips and edge protectors to preserve galvanized coating during ocean transit
- Bare and oiled tubes wrapped in waterproof paper with steel frame support for 5.7 m and 6 m standard lengths
- Container loading optimized for 10×10 to 600×600 mm square profiles to maximize weight utilization within shipping limits
- Heat number and steel grade marked on each bundle for site identification and traceability verification
- FOB, CIF, and DDP shipping terms available with professional loading plans for heavy cargo
- Custom cutting to project-specified lengths available before packaging for scaffolding and structural frame applications
Requesting Quotation and Technical Documentation
Submit your S235/S355 welded square steel tube requirements including outer dimensions, wall thickness, steel grade, surface treatment, quantity, and destination port. We respond within 12 hours with unit pricing, delivery schedule, payment terms, and applicable certification details. For non-standard sizes or custom lengths outside the 5.7 m and 6 m standard, we provide technical confirmation and production timeline before contract signing.
Frequently Asked Questions
Q: What is the difference between S235 and S355 steel grades for welded square steel tubes?
A: S235 and S355 are European standard structural steel grades where the number indicates minimum yield strength in MPa. S355 provides higher load-bearing capacity for structural columns and heavy machinery frames, while S235 suits lighter applications like furniture and non-critical support members. Both grades are available in our ERW welded square steel tube range from 10×10 to 600×600 mm.
Q: Can you provide third-party inspection for critical project shipments?
A: Yes, SGS and BV third-party inspection is available upon request. Our in-house laboratory conducts incoming, in-process, and final inspection for every S235/S355 welded square steel tube production run, and third-party verification can be coordinated before shipment for projects requiring independent certification.
Q: What surface treatment options are available for corrosion protection?
A: We offer pre-galvanized, hot-dipped galvanized, bare, and oiled surface treatments. Pre-galvanized provides moderate corrosion resistance for indoor or sheltered applications, hot-dipped galvanized offers maximum protection for outdoor and marine environments, while bare and oiled finishes suit indoor structural use or projects requiring secondary coating.
Q: How do you handle negative tolerance and weight invoicing?
A: Our S235/S355 welded square steel tubes maintain ±1% dimensional tolerance, and invoicing is based on theoretical weight calculated from specified dimensions. We control negative tolerance through in-house laboratory testing and production line monitoring to ensure actual weight aligns with theoretical calculations, preventing the cost discrepancies that occur with uncontrolled tolerance.
Q: What certifications do you provide for EU market compliance?
A: Our welded square steel tubes carry CE certification under EN 10210/EN 10219 for structural hollow sections, ISO 9001:2015 quality management certification, and Singapore FPC approval. Mill test certificates documenting chemical composition and mechanical properties are provided with every shipment, and complete customs documentation supports EU port clearance.
Get Your S235/S355 Welded Square Steel Tube Quote
Send your specifications, steel grade, quantity, and destination to receive pricing and mill test certificate details within 12 hours.
Contact: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjysteel.com
Website: www.sdxjysteel.com
