Description
Factory-direct ERW welded square steel tube supplier — S355JR and Q235B sections produced in-house from billet to finished tube, eliminating third-party material sourcing gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S355JR / Q235B ERW Square Steel Tube |
| Product Type | ERW Welded Square Steel Tube |
| Steel Grade | S235JR, S355JR, Q235B, SS400, A36 |
| Standard | ASTM A500, EN10219, EN10210, JIS G3466, GB/T 6728 |
| Section Shape | Square |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Cold Rolled / Galvanized (as per customer requirement) |
| Tolerance | ±1% |
| Length | Customized |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Oiled or Non-oiled | Non-oiled |
| Invoicing | By Theoretical Weight |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial & Industrial Construction | Building frames, warehouse columns, truss systems, platform structures |
| Machinery Manufacturing | Machine tool frames, conveyor supports, automation equipment bases |
| Infrastructure | Bridge auxiliary structures, stage trusses, greenhouse frames |
| Vehicle Manufacturing | Trailer chassis, RV frames, transport equipment structures |
| Architectural & Decorative | Stair handrails, furniture frames, facade support systems |
Where Negative Tolerance on an ERW Welded Square Steel Tube Turns a Budget Order into a Claim
Invoicing by theoretical weight while actual wall thickness sits at the lower tolerance boundary creates a gap between what the buyer pays for and what the structure actually carries.
When overseas general contractors order S355JR square tubes for warehouse frames, they calculate load capacity based on nominal dimensions. If the fabricator sources from a mill that pushes wall thickness to the negative tolerance edge, the structural engineer’s safety margin shrinks without anyone noticing until third-party inspection at destination. I have seen 200×200 shipments arrive with weight shortfalls exceeding one ton per container — the negative tolerance was legal on paper, but the client’s structural calculations assumed nominal wall. The rework cost and delay far exceeded the price difference between a reliable ERW welded square steel tube supplier and the cheapest offer on the inquiry list. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
How S355JR and Q235B ERW Welded Square Steel Tube Sections Match Structural Frame Demands
Square hollow sections formed through the ERW process deliver high torsional rigidity with uniform wall distribution across all four faces — a property that matters when columns and beams must resist multi-directional loading in warehouse frames and industrial platforms. The flat internal surfaces simplify connection plate welding and bolt-through detailing, reducing fabrication time at the contractor’s workshop. Our own mill produces the strip coil that feeds the ERW forming line, so chemical composition and mechanical properties remain consistent across heat numbers — the ERW welded square steel tube you receive carries the same material pedigree from billet to finished section.
Engineering Compliance and Certification Pathways for ERW Welded Square Steel Tube
Structural frames designed under EN 1993 require hollow sections conforming to EN 10219 (cold-formed) or EN 10210 (hot-finished) — the ERW process used here falls within the EN 10219 scope, and CE marking under this standard is mandatory for EU market entry. For North American projects specifying ASTM A500 Grade B or C, the same production line can supply compliant sections with matching documentation packages. Corrosion environment dictates surface treatment: cold rolled finish suits indoor structural applications where painting follows on-site, while galvanized coating extends service life in outdoor infrastructure and agricultural buildings. Custom cut-to-length and pre-punched sections reduce secondary processing at the construction site, though dimensional verification against approved shop drawings remains essential before dispatch. [NEED_CITE: ASTM A500 structural tubing specification requirements]
Steel Grade Selection and ERW Welding Process Fundamentals
The S-series grades (S235JR, S355JR) follow the European EN standard system where the number indicates minimum yield strength in MPa — S355JR offers higher load-bearing capacity than S235JR, making it the default choice for primary structural members in multi-story frames and long-span trusses. The Q-series (Q235B) follows the Chinese GB system and remains widely specified across Southeast Asian and African projects where Chinese engineering standards are accepted. SS400 (JIS) and A36 (ASTM) serve Japanese-standard and American-standard projects respectively. The ERW welding process forms the tube by rolling flat strip into a square profile and fusing the seam through electrical resistance heating — no filler metal is added, and the weld zone is normalized during the process. This produces a continuous seam with properties closely matching the parent metal, suitable for structural applications where the weld line does not become the weak point. Wall thickness tolerance of ±1% applies across the full section, though buyers should confirm whether invoicing by theoretical weight aligns with their project’s actual-weight verification protocol.
Hidden Costs When ERW Welded Square Steel Tube Material Certification Falls Short
Ordering S355JR sections without verified mill test certificates per heat number means the structural engineer cannot confirm yield strength compliance — and inspectors at destination will reject the shipment regardless of visual quality. Material traceability gaps between the tube supplier and the original steel producer create documentation voids that delay customs clearance in markets requiring EN 10219 or ASTM A500 compliance certificates. When wall thickness deviates beyond the stated tolerance range, connection details designed for nominal dimensions no longer fit, forcing on-site rework or component replacement — costs that never appeared in the original purchase order. [NEED_CITE: material traceability requirements for structural steel in international construction projects]
Why Project Procurement Teams Source ERW Welded Square Steel Tube from Our Facility
Our production starts from our own steel mill with three rolling lines and over 2,800 raw material specifications in stock — the strip coil that becomes your S355JR square tube never passes through a third-party trader, so chemistry and mechanical properties stay within our controlled range. In-house NDT testing and a理化 laboratory issue mill test certificates documenting chemical composition and mechanical properties per heat number, available for third-party verification by SGS, BV, or TÜV at any production stage. CE certification under EN 10219 covers our cold-formed hollow sections for EU projects, while ISO 9001 governs the full quality management system from incoming material inspection to final dimensional checks. We offer CNC cutting, punching, and bending services that convert raw tubes into fabrication-ready components — reducing the contractor’s workshop processing time. Professional loading plans account for square tube geometry and wall thickness to prevent deformation during ocean transit, and complete export documentation travels with every shipment.
Documentation & Compliance
- Mill test certificate documenting S355JR or Q235B chemical composition and mechanical properties per heat number, conforming to EN 10219 or ASTM A500 as specified
- CE certificate under EN 10219 for cold-formed structural hollow sections, required for EU market entry and project handover
- ISO 9001 quality management system certificate covering the full production chain from steel mill to finished ERW welded square steel tube
- SGS or BV third-party inspection report available upon request, covering dimensional checks, visual weld inspection, and coating thickness measurement
- Full material traceability from billet heat number to finished tube bundle, supporting project-specific quality dossiers
- Export documentation package including packing list, bill of lading, and certificate of origin for customs clearance at destination port
Packaging, Loading & Delivery
- S355JR and Q235B square tubes bundled with steel strips and edge protectors to preserve surface condition during ocean transit
- Galvanized sections receive additional wrapping to prevent zinc coating abrasion between adjacent tubes in the bundle
- Loading plans optimized for square tube geometry, maximizing container payload while preventing deformation of thin-walled sections
- Custom cut-to-length service available, with each bundle labeled by steel grade, heat number, and dimensional specification
- Heat number and steel grade stenciled on each tube end for on-site identification and traceability verification
- FOB, CIF, and DDP shipping terms available, with professional oversized cargo handling for long-length sections
How to Request a Quotation for Your ERW Welded Square Steel Tube Requirement
Share your project drawings or specification list — including steel grade, section dimensions, wall thickness, total quantity, surface treatment preference, and destination port — and we respond within 24 hours with a detailed quotation covering material, fabrication, coating, packing, and shipping costs. If your project requires shop drawing review or custom cutting and punching, our engineering team will confirm fabrication feasibility before you commit. We also provide mill test certificate samples and CE documentation for your compliance review at the inquiry stage.
Frequently Asked Questions
Q: What is the difference between S355JR, Q235B, and ASTM A500 Grade B for structural applications?
A: S355JR follows the European EN system with minimum yield strength of 355 MPa, Q235B follows the Chinese GB system with 235 MPa yield, and ASTM A500 Grade B is the American standard equivalent. The correct grade depends on your project’s governing engineering code and the structural engineer’s specification. We supply all three and can provide grade equivalence documentation for your approval.
Q: Can you provide third-party inspection before shipment?
A: Yes. SGS, BV, and TÜV inspections are available at any production stage — from raw material verification through dimensional checks and coating measurement. The inspection scope and acceptance criteria are agreed before production begins, and the report travels with the shipment documentation.
Q: Do you offer custom cutting, punching, and bending services?
A: Yes. Our fabrication workshop provides CNC cutting, plasma cutting, drilling, punching, and bending services to your approved shop drawings. This converts raw ERW welded square steel tube into fabrication-ready components, reducing your on-site processing time.
Q: How do you handle invoicing — theoretical weight or actual weight?
A: Our standard invoicing is by theoretical weight based on nominal dimensions and standard density. If your project requires actual-weight invoicing, we can arrange over-the-scale verification before packing. We recommend confirming the invoicing method at the quotation stage to avoid discrepancies at destination.
Q: What surface treatment options are available?
A: We offer cold rolled finish (suitable for indoor applications where painting follows on-site), hot-dip galvanized coating (for outdoor and corrosive environments), and custom painting per your project specification. The choice depends on the service environment and the project’s corrosion protection standard.
Get Your ERW Welded Square Steel Tube Quotation with Mill Test Certificate
Submit your specification list — steel grade, dimensions, quantity, surface treatment, and destination — to receive a detailed quotation and documentation package within 24 hours.
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
