Description
Factory-direct welded square tubes — Produced from our own steel mill with full material traceability from billet to finished Q235 welded square steel pipe, eliminating third-party sourcing gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 Welded Square Steel Pipe |
| Product Type | Welded Square Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q255, Q275, Q345 |
| Standard | ASTM, JIS, DIN, GB/T 6728 |
| Section Shape | Square / Rectangular |
| Size Range | 300×300 mm – 500×500 mm |
| Wall Thickness | 0.5 – 30 mm |
| Length | 6 – 12 m |
| Technique | Hot Rolled / Cold Rolled; Welded |
| Surface Treatment | Black / Oiled; Galvanized / Painted upon request |
| Tolerance | ±1% |
| Ends | Plain / Beveled |
| Application | Steel structures, construction frames, bridges, industrial structures |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| General Construction | Building frames, column-beam assemblies, multi-story structural supports |
| Industrial Facilities | Warehouse roof trusses, factory platform structures, equipment support frames |
| Infrastructure | Bridge handrails, sound barrier posts, highway sign gantries |
| EPC Projects | Pipe rack structures, conveyor support frames, modular plant foundations |
What Negative Wall Tolerance Costs on a 300mm Structural Frame Order
Tolerance drift beyond ±1% turns theoretical weight savings into on-site rejection.
When overseas buyers receive welded square tubes with wall thickness below specified minimums, local third-party inspectors flag the entire batch. I have seen 300×300 shipments held at West African ports because negative tolerance exceeded acceptable limits — the material could not pass local re-inspection regardless of mill paperwork. For Q235 welded square steel pipe in structural applications, dimensional accuracy directly affects load-bearing calculations and welding joint fit-up. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
Matching Large-Section Square Tubes to Structural Frame Requirements
For 300×300 to 500×500 mm sections used in primary building frames, the Q235 welded square steel pipe provides adequate yield strength for non-seismic zones while maintaining weldability across thickness ranges from 0.5 to 30 mm. The hot-rolled production route delivers consistent corner radii that align with standard gusset plate connections, while cold-rolled options offer tighter dimensional control for precision machinery frames. Our integrated mill-to-fabrication workflow means the same quality system tracks material from steelmaking through final welding inspection.
Engineering Compliance and Certification Pathways
Structural projects requiring ASTM compliance for North American markets or EN standards for European destinations need documented material equivalence. Q235 corresponds to S235JR in EN system and approximates ASTM A36 in carbon content, though exact mechanical property matching requires project-specific verification. [NEED_CITE: steel grade equivalence tables between GB, EN, and ASTM standards] For welded hollow sections in load-bearing applications, third-party inspection reports from SGS or BV validate dimensional compliance before shipment. Surface treatment selection — black, oiled, galvanized, or painted — depends on corrosion environment and project timeline, with hot-dip galvanizing adding 2-3 weeks to production but extending service life in coastal or industrial atmospheres.
Understanding Q-Series Steel Grades and Welded Tube Manufacturing
The Q-series designation (Q195 through Q345) indicates minimum yield strength in MPa, with Q235 representing the most widely specified grade for general structural applications due to its balance of formability, weldability, and cost. Q345 offers higher strength for reduced section requirements but demands more careful welding procedure control. Welded square tubes are formed from hot-rolled coil, slit to width, then continuously formed and welded via high-frequency induction or submerged arc processes. The weld seam quality directly affects structural integrity — our certified welding procedures per AWS and EN standards ensure full penetration with documented NDT verification. Wall thickness tolerance of ±1% applies across the 0.5-30 mm range, though thicker sections above 20 mm typically require specialized forming equipment.
Hidden Costs of Unverified Material Sources
Purchasing welded square tubes from trading companies without mill ownership creates material traceability gaps that surface during customs clearance or site inspection. Missing heat number documentation, inconsistent chemical composition across batches, or unverified welding procedures can trigger project delays, re-inspection costs, or complete batch rejection. [NEED_CITE: material traceability requirements for structural steel in international construction projects] For Q235 welded square steel pipe in structural applications, the cost difference between verified mill-direct sourcing and broker-supplied material is often offset by reduced inspection fees, faster customs clearance, and elimination of replacement shipping costs.
Why Source Directly from an Integrated Steel Producer
Our facility operates three production lines with over 2,800 specifications in stock, allowing same-week dispatch for standard sizes while custom orders maintain typical production lead times. The vertically integrated model — from steelmaking through final fabrication — means one quality system covers the entire production chain, with mill test certificates issued directly from our laboratory rather than aggregated from multiple suppliers. We hold ISO 9001:2015 certification, EN 10219 compliance for European markets, and AWS-certified welding procedures validated by third-party auditors. Our engineering team reviews shop drawings before production begins, identifying potential fabrication conflicts that cause field rework. Professional loading teams handle oversized components up to 12-meter lengths, optimizing container utilization for 300-500mm sections while protecting surface treatment during ocean transit.
Documentation & Compliance
- Mill test certificate documenting Q235 chemical composition and mechanical properties per GB/T 6728, with heat number traceability to original steelmaking batch
- CE certificate confirming EN 10219 compliance for cold-formed welded hollow sections destined for European Union markets
- ISO 9001:2015 quality management system certificate covering entire production process from raw material inspection through final dimensional verification
- SGS or BV third-party inspection report validating wall thickness, dimensional tolerance, and surface treatment quality before shipment
- Material traceability documentation linking each bundle to specific heat numbers, production dates, and inspection records
- Complete customs documentation including packing list, bill of lading, and certificate of origin formatted for destination country requirements
Packaging, Loading & Delivery
- Q235 welded square steel pipes bundled with high-tensile steel strips at maximum 4-ton intervals, with edge protectors preventing surface damage during handling
- Black or oiled surface treatment preserved through waterproof wrapping for ocean transit, with galvanized tubes receiving additional plastic sleeve protection
- 300×300 to 500×500 mm sections loaded in dedicated containers with wooden chocking to prevent movement, optimizing 20ft or 40ft utilization based on 6m or 12m lengths
- Custom cutting to project-specific lengths available within 6-12m range, with cut ends deburred and marked per bundle identification requirements
- Heat number and steel grade stenciled on each tube end, with bundle tags showing specification, length, weight, and production batch for site verification
- FOB, CIF, or DDP terms available with door-to-door logistics coordination for project sites requiring direct delivery to construction locations
Initiating Your Procurement Process
Submit project specifications including section size, wall thickness, steel grade, quantity, and destination port to receive detailed quotation with mill test certificate preview. Our engineering team reviews shop drawings within 24 hours, confirming dimensional feasibility and suggesting material optimizations for your structural application. Third-party inspection arrangements and certification requirements are confirmed before production begins, ensuring compliance with your project’s quality standards.
Request Factory-Direct Pricing for Q235 Welded Square Steel Pipe
Share your project drawings and specification requirements to receive quotation with material certification and production timeline. Contact our export team at admin@xjystructure.com or reach us via WhatsApp at +86 188 5315 7756 for technical consultation and pricing.
