Description
Factory-Direct ERW Square Tubes — Sourced from our own steel mill with 2,800+ specifications, eliminating third-party material gaps for Q235, Q345, and S355JR grades.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345/S235JR/S275JR/S355JR Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube (ERW) |
| Steel Grade | Q195, Q235, Q345, S235JR, S275JR, S355JR |
| Standard | ASTM |
| Section Shape | Square |
| Wall Thickness | 0.9 mm |
| Length | 6 m / 6.4 m / 12 m |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Fluid Pipe, Boiler Pipe, Drill Pipe, Hydraulic Pipe, Gas Pipe, Oil Pipe, Chemical Fertilizer Pipe, Structure Pipe |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, column supports, platform structures, stairway handrails |
| Petrochemical & Energy | Gas distribution lines, chemical fertilizer transport piping, boiler feed systems |
| Industrial Manufacturing | Hydraulic cylinder barrels, drill pipe casings, conveyor support structures |
| Oil & Gas | Oil well casing, fluid transfer lines, process piping networks |
What Wall-Thickness Tolerance Costs on a Carbon Steel Welded Square Tube Order
A ±1% tolerance on a 0.9 mm wall means the difference between passing inspection and scrapping an entire container.
When procurement teams source a Carbon Steel Welded Square Tube from overseas fabricators, the first thing a third-party inspector checks is wall thickness. A drift into negative tolerance beyond ±1% triggers rejection of the full batch — not just individual pieces. I have seen an entire shipment flagged because wall measurements averaged 0.85 mm on a 0.9 mm spec. The root cause was never the steel itself; it was a mill that did not control its ERW line closely enough. For structural frames and pressure piping, that kind of variance means rework, schedule delays, and a phone call you do not want to make. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed welded hollow sections]
Matching ERW Square Tubes to Structural and Piping Applications
This Carbon Steel Welded Square Tube in Q235, Q345, and S355JR grades serves dual roles across construction and industrial piping. The 0.9 mm wall at ±1% tolerance provides consistent fit-up for welded connections in building frames and platform structures, while the ERW seam meets the continuity requirements for fluid and gas transport lines. Hot rolled surface treatment leaves a mill scale finish suitable for further coating or direct use in indoor structural applications. Our own steel production facility means the same heat of steel that forms the tube also carries through to the mill test certificate — no broken traceability chains.
Engineering Compliance and Certification Pathways
For projects specifying ASTM standards, these ERW square tubes conform to the dimensional and chemical requirements expected in North American procurement. When the same tubes ship to EU markets, buyers typically request EN 10219 compliance documentation for cold-formed welded hollow sections, and our engineering team prepares shop drawing reviews to confirm section properties match design calculations. The ±1% tolerance on the 0.9 mm wall ensures that load-bearing calculations remain valid without derating for thickness uncertainty. For corrosive environments, the hot rolled surface can be upgraded to galvanized or painted finishes during our in-house processing — a decision that should be made before fabrication begins, not after the tubes arrive on site. [NEED_CITE: ASTM A500 structural tubing specification requirements]
Understanding Steel Grades and ERW Welding for Square Tubes
The Q-series (Q195, Q235, Q345) follows the Chinese GB standard system where the number indicates minimum yield strength in MPa, while the S-series (S235JR, S275JR, S355JR) follows the European EN system with similar yield strength designation. For a Carbon Steel Welded Square Tube, selecting between these grades depends on structural load requirements and the governing design code of the destination country. ERW welding produces a longitudinal seam through electric resistance heating, creating a weld zone that is generally narrower and more consistent than spiral-welded alternatives — making it suitable for both structural and pressure applications at this wall thickness. The hot rolled surface treatment means the tube retains its as-formed mill scale, which provides a baseline corrosion resistance for indoor and sheltered applications while offering excellent adhesion for subsequent painting or powder coating. [NEED_CITE: steel grade equivalence mapping between GB Q-series and EN S-series]
Hidden Costs of Incorrect Material Sourcing
Procuring a Carbon Steel Welded Square Tube without verified mill test certificates creates risks that surface only at the inspection stage. Material that does not match the specified grade fails structural load verification and triggers full-batch rejection. Missing heat number traceability breaks the chain required for pressure piping certification under ASME or PED frameworks. And negative tolerance drift beyond the stated ±1% means the theoretical weight used for cost estimation no longer matches actual delivered weight — a discrepancy that either inflates project costs or forces renegotiation after the container has already left the port. [NEED_CITE: material traceability requirements for pressure piping under ASME B31.3]
Why Source Your Carbon Steel Welded Square Tube from XJY Structure
Our vertical integration means the steel mill that produces the raw material also operates the fabrication workshop — there is no gap between the heat number on your mill test certificate and the tubes loaded into your container. With 2,800+ specifications in our raw material inventory, we can fulfill orders across Q195 through S355JR grades without subcontracting to third-party mills that may not maintain the same tolerance controls. Every Carbon Steel Welded Square Tube we ship carries complete quality documentation including WPS, PQR, weld maps, and dimensional inspection reports prepared by our own QC team. Our certified welders hold AWS and EN qualifications, and our processing services — CNC cutting, drilling, bending, and welding — allow us to deliver fabricated components rather than raw tubes when your project requires it. Professional loading planning handles the 6 m, 6.4 m, and 12 m lengths efficiently, maximizing container utilization while protecting the hot rolled surface during ocean transit.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345/S355JR chemical composition and mechanical properties per ASTM standard, with heat number traceability from our own steel mill
- Third-party inspection reports from SGS or BV covering dimensional verification, weld seam quality, and surface treatment compliance for your Carbon Steel Welded Square Tube order
- ISO 9001 quality management system certificate covering the full production chain from raw steel to finished ERW square tubes
- Material traceability documentation linking each tube bundle to its original heat number, rolling date, and chemical analysis report
- Complete export documentation package including packing list, bill of lading, and certificate of origin for customs clearance in EU, Middle East, and Southeast Asian markets
Packaging, Loading & Delivery
- ERW square tubes bundled with steel strips and edge protectors to preserve the hot rolled surface finish and prevent deformation of the 0.9 mm wall during handling
- Seaworthy packaging with moisture barriers for 6 m and 12 m lengths, optimized for 20ft and 40ft container loading to minimize freight cost per ton
- Heat number and steel grade markings stenciled on each bundle for on-site identification and traceability verification during inspection
- Custom cutting to project-specific lengths available before shipment, reducing on-site waste and secondary processing for your Carbon Steel Welded Square Tube installation
- FOB, CIF, and DDP shipping terms with professional oversized cargo loading plans for 12 m lengths that exceed standard container dimensions
Start Your Carbon Steel Welded Square Tube Inquiry
Share your project drawings, steel grade requirements, and target quantity to receive a detailed quotation within 24 hours — including material costs, fabrication charges, coating options, and shipping estimates. Our engineering team will review your specifications and confirm tolerance compliance before production begins.
Request a Quote with Mill Test Certificates
Send your specifications and destination port to receive pricing, lead time, and complete quality documentation for your Carbon Steel Welded Square Tube project.
Contact XJY Structure
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
