Description
Mill-Direct ERW Tube Supply — Own steel mill and fabrication workshop produce Q235 Q355 ERW square rectangular steel tube in 20×20–200×200mm sizes with full ASTM compliance and MTC traceability.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 / Q355 ERW Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (ERW) |
| Steel Grade | Q195, Q235, Q355 |
| Standard | ASTM |
| Section Shape | Square, Rectangular |
| Size Range | 20×20 mm – 200×200 mm |
| Wall Thickness | 1.5 – 30 mm |
| Length | 1 – 12 m (standard 5.8 m / 6 m) |
| Technique | ERW (Electric Resistance Welding) |
| Surface Treatment | Black (Hot Rolled) / Galvanized Coating |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Construction frames / Steel structures / Machinery / Scaffolding / Furniture / Bridge / Mining |
| MOQ | 25 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Steel Structure & EPC | Building frames, warehouse columns, logistics center trusses |
| Industrial Construction | Equipment platforms, machinery frames, conveyor supports |
| Infrastructure | Bridge railings, mining support structures, scaffolding systems |
| Commercial Building | Furniture frames, architectural supports, mezzanine structures |
Where Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on 200×200mm Q355 ERW square rectangular steel tube means the difference between passing dimensional inspection and facing rework claims.
When sourcing from fragmented suppliers, buyers encounter inconsistent wall thickness across batches. A 200×200×8mm tube specified for load-bearing columns may arrive with actual thickness at 7.2mm — a 10% negative deviation that compromises structural integrity. Third-party inspectors flag this during site acceptance, triggering costly replacements. The root cause often traces back to mills sourcing hot-rolled coils from multiple suppliers without unified quality control. [NEED_CITE: ERW tube dimensional tolerance standards for structural applications]
How Q235 Q355 ERW Square Rectangular Steel Tube Matches Structural Frame Requirements
For warehouse and industrial building frames, Q235 provides adequate yield strength for non-critical bracing, while Q355 delivers higher load capacity for main columns and beams. The ERW welding process ensures consistent corner geometry — critical when tubes connect through gusset plates or weld directly to base plates. Our fabrication workshop produces shop drawings with precise cut lengths and hole patterns, eliminating field measurement errors. With 2,800+ raw material specifications in stock, we maintain continuous supply for multi-phase projects spanning months.
Engineering Compliance and Certification for ASTM Standard Projects
ASTM compliance governs North American construction codes, requiring documented chemical composition and mechanical properties per heat number. Q235 roughly corresponds to ASTM A36 in carbon content, while Q355 aligns with higher-strength grades used in seismic zones. Galvanized surface treatment meets corrosion protection requirements for outdoor industrial environments, while black (hot-rolled) finish suits indoor applications where field painting follows installation. Third-party inspection by SGS or BV verifies dimensional accuracy and weld seam quality before shipment. [NEED_CITE: ASTM A500 cold-formed structural tubing requirements]
Understanding ERW Welding Process and Steel Grade Selection
ERW (Electric Resistance Welding) forms tubes by rolling steel strip into shape and welding the seam through electrical resistance heating — no filler metal required. This process produces consistent wall thickness and smooth internal surfaces ideal for fluid conveyance or structural applications. Q195 serves light-duty furniture frames where forming takes priority over strength. Q235 balances weldability and strength for general construction. Q355 offers higher yield strength for heavy-load applications like crane runways or multi-story building frames. The ±1% tolerance ensures predictable weight calculations — critical when shipping 25-ton containers where theoretical weight determines freight costs.
Hidden Costs of Sourcing Non-Compliant ERW Tubes
Material certificates listing incorrect chemical composition trigger customs delays at destination ports. Negative wall thickness beyond tolerance forces engineers to recalculate load capacity, potentially requiring structural redesign. Missing heat number traceability prevents proper welding procedure qualification — welders cannot verify base metal compatibility. These issues surface during inspection, causing project delays measured in weeks, not days. [NEED_CITE: material traceability requirements for structural steel certification]
Why Source Q235 Q355 ERW Square Rectangular Steel Tube from XJY Structure
Our vertically integrated operation eliminates the gap between material supplier and fabricator. The own steel mill produces hot-rolled coils in 2,800+ specifications, feeding directly into our tube forming lines — no third-party sourcing creates quality gaps. The fabrication workshop handles CNC cutting, drilling, and welding per approved WPS, delivering finished components ready for assembly. Certified welders hold AWS/EN qualifications, with complete documentation packages including weld maps and dimensional inspection reports. Professional loading teams secure oversized tubes in containers, preventing transit damage that causes field rework.
Documentation & Compliance
- Mill Test Certificate documenting Q235/Q355 chemical composition and mechanical properties per ASTM, with heat number traceability from coil to finished tube
- ISO 9001 quality management certificate covering the entire production process from raw material inspection to final dimensional checks
- SGS or BV third-party inspection reports verifying wall thickness, corner geometry, and weld seam quality before container loading
- Material traceability records linking each tube bundle to specific heat numbers, enabling proper welding procedure qualification on site
- Complete customs documentation including packing list, bill of lading, and certificate of origin for smooth port clearance
Packaging, Loading & Delivery
- Q235 Q355 ERW square rectangular steel tube bundled with steel strips at 1–3 meter intervals, preventing bundle separation during ocean transit
- Galvanized tubes packed with edge protectors and plastic wrapping to preserve zinc coating from scratching during handling and shipping
- Container loading optimized for 5.8m and 6m standard lengths, maximizing payload within 25-ton MOQ while maintaining weight distribution
- Cut-to-length service available for 1–12m requirements, with plain ends deburred to prevent injury during field handling
- Each bundle tagged with heat number, steel grade, and dimensional specifications for immediate site identification
- FOB, CIF, and DDP terms available with professional logistics coordination for door-to-door delivery to project sites
Getting Your Q235 Q355 ERW Square Rectangular Steel Tube Quote
Share project drawings in PDF or DWG format along with steel grade requirements, surface treatment preference, and destination port. Our engineering team reviews specifications within 24 hours, providing detailed quotation including material, fabrication, coating, and shipping costs. Shop drawing approval precedes production, ensuring dimensional accuracy matches your structural design.
Request Mill-Direct Pricing with Full Documentation
Submit your Q235 Q355 ERW square rectangular steel tube specifications to receive quotation with Mill Test Certificate and third-party inspection options.
Contact:
- 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
