Description
Factory-Direct Carbon Steel Square Steel Tube — Full Range 20-610mm in Stock
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Carbon Steel Square Steel Pipe |
| Product Type | Square and Rectangular Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q345, 10#, 20# |
| Standard | GB/T 6728, EN 10210, EN 10219, JIS G3466, ASTM A106, ASTM A335 |
| Section Shape | Square / Rectangular |
| Size Range | 20mm–610mm |
| Wall Thickness | 0.6mm–20mm |
| Length | Standard export length or as per customer request |
| Technique | ERW |
| Surface Treatment | Bare surface / Varnish painting / Galvanizing / Hot Rolled |
| Tolerance | ±1%, ±5% |
| Ends | Plain / Beveled |
| Application | Steel structures / Construction frames / Machinery / Scaffolding |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Civil Engineering | Building frames, column supports, roof trusses, bridge handrails |
| Infrastructure & Scaffolding | Scaffolding uprights, steel towers, temporary access structures |
| Machinery Manufacturing | Conveyor frames, equipment bases, hydraulic cylinder housings |
| Shipyard & Marine | Deck structures, bulkhead stiffeners, ventilation ducts |
Where Wall-Thickness Tolerance Decides Project Acceptance
Negative tolerance beyond specification triggers rejection at site inspection.
I have seen entire container loads of square tubes rejected because the thinnest point measured 0.4mm below contract wall thickness. The监理 refused sign-off, and the cargo sat in the yard for three months before being sold at a loss. For Carbon Steel Square Steel Tube orders, tolerance control is not a paperwork detail — it determines whether the structure passes load calculation and whether customs releases the shipment. Inconsistent material properties and missing mill certificates cause delays that no amount of price discount can compensate for. [NEED_CITE: EN 10219 cold-formed hollow section requirements]
Structural Frame Compatibility for Load-Bearing Applications
Carbon Steel Square Steel Tube in grades Q235 and Q345 provides the yield strength range required for most building frame and scaffolding applications across Southeast Asia, Middle East, and African markets. The ERW welding process produces a continuous seam with uniform heat-affected zone, suitable for bolted and welded connections without pre-heating in most structural conditions. Our factory maintains ready stock across 2,800+ specifications, enabling split shipments for phased construction schedules without full-container commitment.
Engineering Compliance and Certification Requirements
Structural hollow sections supplied under EN 10219 must meet dimensional tolerances, chemical composition limits, and mechanical property thresholds defined for non-alloy and fine grain steels. For European projects, CE certification per EN 10210/EN 10219 is mandatory for customs clearance and structural engineer approval. [NEED_CITE: CE marking requirements for structural steel hollow sections] ASTM A500 grades serve North American specifications, while JIS G3466 covers Japanese industrial projects. Surface treatment selection — bare, galvanized, or painted — depends on corrosion environment: galvanized coating extends service life in coastal or industrial atmospheres, while bare tubes suit indoor or painted applications.
Steel Grade Selection and ERW Process Fundamentals
Q235 and Q345 represent the most widely specified grades for general structural applications, with Q345 offering higher yield strength for heavier load conditions. The Q-series (Chinese GB standard) corresponds broadly to S235/S355 in EN system and A36/A572 in ASTM, though exact chemical composition and mechanical properties require grade-by-grade verification. [NEED_CITE: steel grade equivalence between GB EN and ASTM standards] ERW (Electric Resistance Welding) forms the tube from hot-rolled coil through continuous forming and high-frequency current welding, producing a clean internal bead suitable for fluid conveyance at moderate pressures. Wall thickness tolerance of ±1% to ±5% applies depending on size range — thinner walls require tighter control to maintain structural integrity.
Hidden Costs of Incorrect Material Procurement
Procuring Carbon Steel Square Steel Tube without verified mill test certificates risks material substitution — lower-grade steel delivered as Q345 fails load testing and requires complete replacement. Missing CE documentation halts customs clearance for European destinations, incurring demurrage charges that exceed the original material cost. [NEED_CITE: customs clearance requirements for structural steel imports] Negative tolerance abuse — where actual wall thickness falls below minimum specification — compromises structural safety and voids engineering certification, regardless of theoretical weight calculations.
Why Global Buyers Source from Xin Jiyuan
We operate three production lines running simultaneously, delivering monthly capacity exceeding 20,000 tons of square and rectangular tubes without outsourcing to trading companies. Every batch ships with original mill test certificates documenting chemical composition and mechanical properties, with SGS or BV third-party inspection available for projects requiring independent verification. Our ISO 9001:2015 certification and CE marking per EN 10210/EN 10219 ensure compliance across European, Middle Eastern, and African markets. The factory maintains large ready stock covering 2,800+ specifications, supporting urgent orders and split shipments for phased construction projects. Professional export teams handle container loading optimization, documentation, and customs clearance for destinations across 50+ countries.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345 chemical composition and yield strength per GB/T 6728 or EN 10219
- CE certificate confirming compliance with EN 10210/EN 10219 for European structural applications
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report available upon request for project-specific verification
- Material traceability by heat number linking each bundle to original coil test results
- Complete customs documentation including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Square tubes bundled with steel strips and edge protectors to prevent coating damage during ocean transit
- Galvanized surfaces wrapped with waterproof paper to preserve zinc coating integrity in humid conditions
- Container loading optimized for 20ft and 40ft units, maximizing weight utilization for 20-200mm size ranges
- Cut-to-length service available for standard export lengths or project-specific dimensions up to 12 meters
- Heat number and steel grade stenciled on each bundle for site identification and traceability
- FOB, CIF, and DDP terms available with door-to-door logistics coordination for project sites
Request Quotation with Mill Test Certificate
Submit your specification sheet including outer diameter, wall thickness, length, steel grade, and destination port to receive competitive factory-direct pricing within 12 hours. We provide original mill test certificates and third-party inspection options for project compliance verification.
Start Your Carbon Steel Square Steel Tube Inquiry
Send specifications via email or WhatsApp to receive bulk pricing with volume discounts and delivery schedule.
Email: admin@sdxinjiyuan.com
Mobile/WhatsApp: +86 188 5315 7756
Frequently Asked Questions
Q: What is the difference between Q235 and Q345 steel grades for square tubes?
A: Q235 offers lower yield strength suitable for light structural applications, while Q345 provides higher yield strength for heavier load-bearing conditions. Both grades comply with GB/T 6728 standard for cold-formed welded hollow sections.
Q: Can you provide EN 10219 certified square tubes for European projects?
A: Yes, our Carbon Steel Square Steel Tube production carries CE certification per EN 10210/EN 10219, with mill test certificates documenting compliance to European dimensional tolerances and mechanical property requirements.
Q: What is the minimum order quantity for custom sizes?
A: We accept trial orders from 1 ton for standard specifications, with flexible MOQ for non-standard sizes depending on production scheduling and raw material availability.
Q: Do you offer third-party inspection for project verification?
A: SGS and BV third-party inspection services are available upon request, with inspection reports documenting dimensional verification, surface quality, and mechanical testing results.
Q: How do you handle negative tolerance in wall thickness?
A: We maintain strict tolerance control per GB/T 6728 and EN 10219 standards, with mill test certificates documenting actual measured wall thickness for each batch to ensure compliance with contract specifications.
