Description
Factory-Direct ERW Square Steel Tube — S355JR and Q235B grades produced on dedicated lines with in-house lab testing before every shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S355JR / Q235B ERW Square Steel Tube |
| Product Type | Welded Square Steel Tube (ERW) |
| Steel Grade | S235JR, S355JR, Q235B, SS400, A36 |
| Standard | ASTM A500, EN 10219, EN 10210, JIS G3466, GB/T 6728 |
| Section Shape | Square |
| Technique | ERW (Electric Resistance Welded) |
| Length | Customized |
| Surface Treatment | Cold Rolled / Galvanized (optional) |
| Tolerance | ±1% |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Invoicing | By Theoretical Weight |
| Oiled or Non-oiled | Non-oiled |
| Application | Steel structures, machinery manufacturing, infrastructure construction, vehicle manufacturing, home decor and furniture |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Factory building frames, stadium roof trusses, commercial center column structures |
| Machinery Manufacturers | Machine tool frames, conveyor support structures, automation equipment frameworks |
| Infrastructure Construction | Bridge auxiliary structures, stage trusses, greenhouse frames |
| Vehicle Manufacturing | Trailer chassis frames, RV structural frames |
| Home Decor & Furniture | Stair handrails, security window frames, furniture support frames |
What Negative Tolerance Actually Costs on a Structural Frame Order
A ±1% wall thickness deviation billed by theoretical weight means the buyer pays for steel that may not arrive.
I once watched an entire container of 200×200 ERW structural tubes get rejected at Jebel Ali port because the wall thickness had drifted to −1.2mm negative tolerance — the site inspector pulled out a caliper, measured three random pieces, and refused the lot. The theoretical weight on the invoice looked fine, but the actual load-bearing capacity was compromised. When ERW square steel tube is invoiced by theoretical weight without tight process control, the cost gap between what you pay and what you receive becomes a structural liability. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
Matching ERW Square Tube to Structural Frame Requirements
Square sections deliver superior torsional stiffness compared to open profiles like C-channels or U-channels — the closed geometry resists twisting under asymmetric loads, which matters when factory roof trusses or conveyor frames face dynamic forces. Our ERW square steel tube in S355JR and Q235B grades comes pre-cut and pre-punched to project drawings, reducing on-site fabrication time. The ±1% tolerance is verified in our physical laboratory before dispatch, and each bundle carries heat-number traceability back to the coil.
Engineering Compliance and Certification Pathways
Structural frames for European projects must conform to EN 10219 for cold-formed welded hollow sections, while North American specifiers typically reference ASTM A500 Grade B or C. Our S355JR tubes meet EN 10219 and EN 10210 requirements, carrying CE marking for EU customs clearance — a document gap that routinely causes port holds. [NEED_CITE: CE marking requirements for structural steel under EN 10210] For corrosion-prone environments such as greenhouse frames or coastal infrastructure, galvanized surface treatment extends service life without additional field coating. Custom cut-to-length service eliminates secondary cutting at the job site, and fixed-length bundles simplify container loading plans for heavy cargo.
Steel Grade Selection and ERW Process Fundamentals
The S-series grades (S235JR, S355JR) follow the European EN standard system where the number indicates minimum yield strength in MPa — S355JR provides higher load capacity than S235JR for the same cross-section. Q235B follows the Chinese GB system and broadly corresponds to S235JR in mechanical behavior, while SS400 (JIS) and A36 (ASTM) serve similar general structural roles. [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500] ERW welding forms the tube by rolling steel strip into a square profile and fusing the seam through electrical resistance — this process produces a clean weld line with consistent wall thickness around the section, making it suitable for structural frames where uniform load distribution matters. Cold rolled surface finish provides a smooth appearance for visible architectural applications, while galvanized coating adds zinc-layer corrosion protection for outdoor or humid environments. Wall thickness tolerance directly affects both theoretical weight invoicing and actual structural performance — tighter control means the engineer’s load calculations match the delivered product.
Hidden Costs of Unverified Square Tube Procurement
Material substitution — receiving Q235B when S355JR was specified — passes visual inspection but fails structural load testing, forcing complete frame replacement. Missing CE certificates delay customs clearance for weeks on EU-bound shipments, generating demurrage charges that exceed the steel cost itself. Excessive negative tolerance on wall thickness reduces the moment of inertia below design values, creating safety concerns that the project engineer must flag and the buyer must absorb. [NEED_CITE: consequences of dimensional non-compliance in structural hollow sections]
Why Engineering Buyers Source ERW Square Steel Tube from Xin Jiyuan
Our three dedicated production lines cover over 2,800 specifications in square and rectangular sections, so non-standard dimensions do not require separate supplier sourcing. Every batch passes through our in-house physical and chemical laboratory — tensile tests, chemical composition analysis, and dimensional checks are completed before any tube leaves the facility, with results documented in the mill test certificate. We hold CE certification under EN 10210 and EN 10219, ISO 9001:2015 registration, and third-party verification from SGS and BV — covering the documentation requirements for EU, Middle Eastern, and Southeast Asian project specifications. Our proprietary sharp-corner rectangular tube technology, backed by 41 patents, fills a gap that standard catalog products cannot address. Professional container loading plans optimize weight distribution for heavy square tube shipments, and we coordinate FOB, CIF, and DDP delivery to over 50 countries.
Documentation & Compliance
- Mill test certificate documenting S355JR or Q235B chemical composition and mechanical properties per EN 10219 or GB/T 6728
- CE certificate confirming compliance with EN 10210 and EN 10219 for structural hollow section export to EU markets
- ISO 9001:2015 quality management system certificate covering the full ERW square steel tube production process
- SGS or BV third-party inspection report available for independent material and dimensional verification
- Heat number traceability linking each bundle to its original coil test data
- Full customs document package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- ERW square steel tubes bundled with steel strips and edge protectors to prevent surface damage to cold rolled or galvanized finishes during ocean transit
- Galvanized-coated square tubes wrapped with waterproof paper and plastic film to preserve zinc layer integrity in humid port environments
- Custom cut-to-length tubes stacked by fixed dimensions for optimized container loading, maximizing weight utilization for heavy S355JR sections
- Heat number and steel grade stenciled on each bundle for on-site identification and traceability verification
- FOB, CIF, and DDP shipping terms available with professional loading plans for 20ft and 40ft containers
- Door-to-door logistics coordination to project sites across the Middle East, Southeast Asia, EU, and North America
Request a Project-Specific Quotation for ERW Square Steel Tube
Submit your section dimensions, wall thickness, steel grade, total quantity, and destination port — we respond within 12 hours with unit pricing, production lead time, applicable certifications, and mill test certificate documentation. Non-standard dimensions and custom processing requirements receive a separate technical review.
Get Your ERW Square Steel Tube Quote with Mill Test Certificate
Send your specifications via email or WhatsApp to receive a detailed quotation with full material documentation.
Company: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxjysteel.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjysteel.com
Frequently Asked Questions
Q: How do S355JR, Q235B, and ASTM A500 Grade B compare for structural frame applications?
A: S355JR (EN standard) offers higher minimum yield strength than S235JR and Q235B, making it suitable for heavier load-bearing frames. Q235B (GB standard) and SS400 (JIS standard) serve general structural purposes. ASTM A500 Grade B is the North American equivalent for cold-formed welded structural tubing. We supply all these grades and can advise on equivalence for your project specification.
Q: Can you produce non-standard square tube dimensions outside typical catalog sizes?
A: Yes. Our production lines cover over 2,800 specifications including custom non-standard dimensions. We also hold 41 patents including proprietary sharp-corner rectangular tube technology. Submit your required section size, wall thickness, and length for a feasibility review.
Q: What is the difference between galvanized and cold rolled surface treatment for ERW square tubes?
A: Cold rolled finish provides a smooth, clean surface suitable for indoor or painted applications where appearance matters. Galvanized coating adds a zinc layer for corrosion protection, extending service life in outdoor, coastal, or humid environments such as greenhouse frames and infrastructure projects. The choice depends on your exposure conditions and whether field painting is planned.
Q: How does theoretical weight invoicing work with wall thickness tolerance?
A: Our ERW square steel tubes are invoiced by theoretical weight based on nominal dimensions, with wall thickness tolerance controlled at ±1%. Each shipment is verified in our in-house laboratory, and the mill test certificate confirms actual measured dimensions. This ensures the structural performance matches the engineer’s design calculations.
Q: What certifications and documents do you provide for EU and Middle East project compliance?
A: We provide CE certification under EN 10210 and EN 10219 for EU market compliance, ISO 9001:2015 quality certificate, mill test certificates with chemical and mechanical data, and third-party inspection reports from SGS or BV upon request. Full customs documentation including packing list, bill of lading, and certificate of origin is included with every shipment.
