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Help CenterSquare Steel & Square Hollow Section， GB/T 6728、GB/T 3094、ASTM A500、EN10305-5
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1. Product Overview
Square steel tube (hollow section) is a long steel product with a square hollow cross-section, formed by hot rolling or cold bending/welding of steel strip or steel plate. It is widely used in construction, machinery manufacturing, steel structures, vehicles, and engineering.
2. Main Specifications
• Square tube:
20×20, 25×25, 30×30, 40×40, 50×50, 60×60, 80×80, 100×100, 120×120, 140×140, 150×150, 200×200, 250×250, 300×300 mm
• Wall thickness: 0.8–20 mm
• Length: 5.8m, 6m, 11.8m, 12m, customizable fixed length
• Tolerance:
◦ Size tolerance: ±0.5mm ~ ±2mm
◦ Wall thickness tolerance: ±0.1mm ~ ±0.5mm
3. Material Grades
• Carbon structural steel: Q195, Q235B, Q355B (16Mn), S235JR, S355JR
• High-quality carbon steel: 10#, 20#, 45#
• Alloy steel: 16Mn, Q355C/D/E
• Stainless steel: 201, 304, 316L (customizable)
4. Production Standards
• GB/T 6728 (Cold-formed square & rectangular hollow sections)
• GB/T 3094 (Seamless square steel tube)
• GB/T 1591, GB/T 700
• EN10210, ASTM A500, JIS G3466 (available on request)
5. Production Process
Hot rolled coil → Uncoiling → Leveling → Roll forming → High-frequency welding → Sizing → Cutting → Straightening → Deburring → Inspection → Packing
6. Surface & Appearance
• Surface: black iron oxide skin (mill finish), bright surface, or galvanized
• No obvious cracks, bubbles, scars, or inclusions
• Straightness: ≤2mm/m
• Weld seam smooth and uniform (for welded tubes)
7. Mechanical Properties (Typical Q235B)
• Yield strength: ≥235 MPa
• Tensile strength: 375–500 MPa
• Elongation: ≥20%
• Good weldability, bendability, and processability
8. Applications
• Steel structure buildings, workshops, warehouses
• Construction support, curtain wall, scaffolding
• Machinery frames, vehicle chassis, agricultural equipment
• Guardrails, shelves, pipelines, decorative profiles
• Shipbuilding, engineering machinery, hardware components
9. Weight Calculation
Square tube theoretical weight (kg/m)
= (Outer side – Wall thickness) × Wall thickness × 4 × 0.00785
Example:
50×50×2.0mm tube ≈ 3.01 kg/m
10. Packaging & Delivery
• Bundled with steel strips, wooden pallets or bulk
• Marked with: grade, specification, heat No., batch No., manufacturer
• Transport: by truck, train, container sea freight
• Moisture-proof, anti-collision during transportation
11. Delivery Condition
• Hot rolled / cold formed black tube
• Galvanized square tube (hot-dip galvanized / electro galvanized)
• Paint or oil coated as required
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