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Help CenterSquare Steel & SHS Square Hollow Section，GB/T6728-2017、EN10219、ASTM A500、JIS G3466、GB/T34201、EN10210、ASTM A501、
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Steel Billet，Main Materials Q195, Q235B, Q355B, 20#, 45#, SS400, A36, S235JR,NegotiableMOQ: 1 Metric Ton
1. Product Overview
Square Tube, full name Square Hollow Section (SHS), together with matching Rectangular Hollow Section (RHS), is hollow structural steel with square cross-section. It is manufactured from hot/cold rolled steel strips or seamless round billets via cold bending & high-frequency welding or hot extrusion process. Featuring standard 90° right-angle edges, high torsional stiffness, light dead weight and strong load-bearing capacity, it boasts excellent performance in cutting, drilling, welding and bending. Widely applied in steel construction, engineering machinery, PV brackets, vehicle chassis, storage racks and other load-bearing & decorative structures, it is a universal structural profile worldwide.
2. Production Process Classification & Specifications
2.1 Cold Formed ERW Square Tube (Main In-Stock Type)
Applicable Standards: GB/T6728-2017, EN10219, ASTM A500, JIS G3466
Process Flow: Strip uncoiling → roller cold forming → high-frequency resistance welding → sizing & straightening → fixed-length cutting
Square Size Range: 10×10mm ~ 500×500mm
Wall Thickness: 1.0mm ~ 30mm; thin wall 1.0–3.0mm, heavy wall 4–30mm
Standard Length: 5.8m, 6m, 12m; custom fixed length 3–18m available
Surface Finish: Black bare surface with slight oxide scale, anti-rust oil coated optionally
Advantages: Complete sizes, short lead time, cost-effective for general indoor & outdoor structures
Applications: Factory frames, guardrails, storage racks, PV brackets, furniture frames
2. Hot Rolled Seamless Square Tube (For Heavy Load & High Pressure)
Applicable Standards: GB/T34201, EN10210, ASTM A501
Process Flow: Round billet heating & piercing → hot extrusion into square shape → high-temperature finishing
Square Size Range: 40×40mm ~ 800×800mm
Wall Thickness: 3.0mm ~ 60mm, ultra-heavy wall for heavy load bearing
Advantages: Weld-free structure, uniform mechanical performance, superior compression, impact and fatigue resistance
Applications: Heavy machinery bases, bridge load-bearing components, large equipment supports, hydraulic frames
3. Common Material Grades, Properties & Applications
3.1 Ordinary Carbon Square Tube (Economical General Grade)
Grades: Q195, Q235B (Equivalent to S235JR, ASTM A500 Gr.B, STK400)Low carbon steel with easy welding and good plasticity, cost-efficient; for indoor steel structures, temporary supports, guardrails and storage racks.
3.2 Low Alloy High Strength Square Tube (Heavy-Duty Outdoor Grade)
Grades: Q355B/C/D (Equivalent to S355JR, ASTM A500 Gr.C, STKR490)High yield strength, excellent low-temperature impact toughness, resistant to wind & snow load; for PV brackets, vehicle chassis, container frames, outdoor factories and bridge auxiliary components.
3.3 High-Quality Carbon / Alloy Seamless Square Tube (Precision Machinery)
Grades: 20#, 45#, 40CrAdjustable strength & hardness after quenching and tempering heat treatment; for heavy-duty equipment frames, hydraulic supports and special machinery fittings.
4. Optional Surface Treatments
Black bare tube with anti-rust oil: Original factory finish, short-term rust protection, lowest cost for indoor structures
Hot-dip galvanized tube: Zinc coating weight 200–600g/㎡, long anti-corrosion service life; for coastal areas, outdoor PV brackets, guardrails and municipal projects
Electro-galvanized / paint & powder coating: Thin zinc layer or colored coating for decoration & rust prevention, applied to equipment housings and decorative frames
5. Core Technical Quality Indicators
Dimensional ToleranceStrict compliance with GB, ASTM and EN standards on side length, wall thickness, straightness and twist; smooth weld bead without excess weld metal, neat right angle without corner collapse
Mechanical Properties
Q235B: Yield strength ≥235MPa, Tensile strength 375–500MPa, Elongation ≥21%
Q355B: Yield strength ≥355MPa, Tensile strength 470–630MPa, qualified low-temperature impact test
Weld QualityFull weld fusion without slag inclusion, cold joint or crack; UT ultrasonic testing available for heavy wall tubes
Surface StandardFree of deep scratches, pits, lamination and cracks; uniform galvanized layer without missing plating or sagging
6. Auxiliary Processing Services
Fixed-length saw cutting: Custom cutting to required length, smooth burr-free cutting surface
Punching, bending & bevel processing: Pre-fabrication of mounting holes and welding bevels with matched equipment
Hot-dip galvanizing OEM service: Galvanizing processing supplied with bare tubes
Sand blasting & rust removal: Remove oxide scale from black tubes to improve paint adhesion
7. Packaging, Delivery & Foreign Trade Terms
7.1 Seaworthy Export Packaging
Standard bundling: Square tubes bundled and fastened with steel strips, 1–3 tons per bundle; size, material grade and heat number sprayed on tube ends
Moisture-proof export package: Wrapped with anti-rust paper inside, overall covered by moisture-proof film, fixed on fumigated solid wood pallets to resist seawater corrosion and collision
Thin-wall small-size tubes: Extra plastic film wrapping for full protection
7.2 Delivery Lead Time
Standard in-stock black square tubes: Shipment within 5–7 daysSeamless heavy wall tubes, galvanized processing and customized special sizes: 7–15 days
7.3 Shipping Ports
Tianjin Port and Qingdao Port, supporting full container 40GP/40HC and LCL shipments. Complete export documents supplied: Material Test Certificate, English third-party inspection reports (SGS/BV), Packing List, Commercial Invoice; FTA Certificate of Origin can be issued.
7.4 Payment Terms
30% TT advance payment, balance settled before shipment. Letter of Credit (LC) is not acceptable.Minimum order quantity: 1 ton, mixed loading of multiple sizes & grades supported.
8. Downstream Application Industries
Steel Construction: Portal frames of factory buildings, floor supports, canopies, guardrails and fence columns
New Energy Industry: PV ground & rooftop brackets, auxiliary frames for wind power equipment
Transportation & Logistics: Truck chassis, container frames, heavy-duty storage racks
Engineering Machinery: Frames for agricultural machinery, air compressors, pumps and hydraulic equipment
Municipal Decoration: Road guardrails, bus stations, landscape steel structures and equipment housings
9. Core Product Advantages
Full size coverage: Complete stock from 10×10 to 500×500mm, one-stop supply of thin wall, heavy wall, seamless and welded square tubes
Diverse material options: Ordinary carbon, low alloy, high-quality carbon & alloy steel available to meet light & heavy load scenarios
Strong processing adaptability: Support cutting, welding, bending, punching, heat treatment and galvanizing deep processing for easy fabrication
Reliable quality: Raw materials from formal steel mills, physical & chemical test reports attached for each batch, fully traceable heat numbers, third-party inspection acceptable
Mature export service: Standardized moisture-proof seaworthy packaging, full set of English customs clearance documents, compliant with procurement standards worldwide
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