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Help CenterSquare Steel & Square Steel Tube，Q235B、Q355B、SPHC、STKR400、STKR490
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1. Product Overview
Square tube, full name Square Hollow Structural Section (SHS), is square hollow steel with equal four sides. It is manufactured by cold forming & high-frequency welding of steel strip/plate, or seamless hot extrusion. Square tube & rectangular tube are collectively called hollow sections.
Featuring hollow lightweight structure, excellent bending and torsion resistance, square tube consumes less raw material than solid steel under equal load, effectively cutting project cost. It can be processed by cutting, bending, punching, welding, hot-dip galvanizing and other secondary treatments, widely used in steel structure, machinery frame, infrastructure, photovoltaic and decoration industries.
We supply ERW square tubes, submerged arc welded heavy-wall large-size square tubes and seamless square tubes with sufficient spot stock. Shipment from Tianjin Port within 5–7 working days for standard sizes. Complete mill test certificates, mechanical test reports and third-party SGS inspection documents are available.
2. Applicable Standards
Chinese National Standards
GB/T 6728-2017 Cold formed hollow structural sections for construction GB/T 3094 Cold drawn special-shaped steel tubes GB/T 6725 General technical requirements for cold formed sections
International Standards
ASTM A500, EN 10219/EN 10210, JIS G3466, AS1163
Certificates
Mill Test Certificate (MTC), CE, ISO, BV, SGS test reports
3. Product Classification by Production Process
3.1 ERW High-Frequency Welded Square Tube (Mainstream)
For medium & small size thin-wall tubes, side length ≤200mm, wall thickness 1.0–6mm Advantages: High production efficiency, cost-effective, straight tube body, smooth weld Applications: Factory secondary beams, guardrails, billboards, door & window frames, small equipment supports
3.2 Submerged Arc Welded Square Tube
For large size heavy-wall tubes, side length ≥100mm, wall thickness ≥6mm Advantages: Deep weld penetration, high weld strength, strong load & pressure resistance Applications: Large factory columns, bridge supports, heavy machinery base, energy storage steel structure
3.3 Seamless Square Tube
Formed by hot extrusion of round tube without welding seam, top performance on pressure & impact resistance Advantages: Free of welding defects, suitable for heavy load, high pressure & low temperature working conditions Applications: Construction machinery, hydraulic equipment, low-temperature engineering, precision equipment frames
4. Main Material Grades
Carbon steel square tube: Q195, Q235B (SS400, S235JR), for decoration & light structure
Low alloy high strength square tube: Q355B/Q355C/Q355D (S355JR), high bearing capacity, anti-cracking under low temperature, ideal for factory, PV & bridge
Quality carbon seamless square tube: 20#, 45#, for mechanical processing & precision equipment
Stainless steel square tube: 304, 316L, anti-corrosion for chemical, marine & outdoor decoration
5. Specification Parameters
Side size range: 10×10mm ~ 800×800mm
Wall thickness range: 0.6mm ~ 32mm, full range of thin, standard, heavy & extra heavy wall
Standard length: 6m/9m/12m, custom cut-to-size 1–12m available, length tolerance ±50mm
Optional surface treatment
Black bare tube with anti-rust oil: Low cost, for indoor structure
Hot-dip galvanized tube: Zinc coating 40–600g/㎡, outdoor anti-corrosion for PV brackets & municipal guardrails
Electro-galvanized, painted, polished, pickling & passivation (for stainless steel)
6. Core Product Advantages
Superior mechanical performance: Symmetrical square cross-section with uniform stress on four sides, better bending & torsion resistance than round tube, stable bearing capacity for construction
High dimensional accuracy: Good straightness, neat edges, small machining allowance, no cracking during bending
Complete size stock: Thin-wall decorative, heavy load thick-wall, extra large seamless tubes in stock, fast production for special sizes
Diverse anti-corrosion solutions: Bare tube, galvanized & painted options for indoor, outdoor, humid & acid-alkali environment
Traceable quality: Each bundle marked with heat number, material grade & size; flattening, tensile, impact and UT inspection supported
7. Packing, Shipment & Trade Terms
Export packing: Bundled with steel strips, wrapped with inner VCI anti-rust paper & outer waterproof film; large sizes fixed on fumigated wooden pallets with edge protectors against collision
Marking: Each bundle labeled with material grade, side size, wall thickness, length, net weight, heat batch number & applicable standard
Loading Ports: Tianjin Port, Qingdao Port
Lead time: 5–7 days for spot goods; 7–15 days for customized heavy-wall / seamless / galvanized tubes
Payment Term: 30% TT deposit, balance TT against copy of bill of lading; LC not accepted
Trade Term: FOB, CIF, CFR, EXW negotiable
8. Main Application Fields
Building Steel Structure: Factory columns, floor secondary beams, curtain wall keel, canopy supports, container frames
Municipal Engineering: Road guardrails, PV brackets, overpass handrails, outdoor billboards, wall frames
Machinery Manufacturing: Equipment base, conveyor frame, construction machinery chassis, machine tool protective frame
Decoration & Furniture: Door & window frames, storage racks, iron art guardrails, exhibition booths, furniture tubes
New Energy Industry: Load-bearing frame for energy storage equipment, auxiliary wind power supports, PV power station steel structure
Chemical & Marine Industry: 304/316 stainless square tubes for anti-corrosion equipment & seawater treatment accessories
9. Pre-Delivery Inspection Items
Dimension & visual inspection: Side length, wall thickness, straightness, flat end surface, weld appearance
Mechanical test: Tensile test (yield strength, tensile strength, elongation), flattening test, impact toughness
Anti-corrosion test (galvanized tube): Zinc coating thickness, salt spray test
Optional test: Spectrum chemical analysis, ultrasonic weld flaw detection, third-party SGS inspection
Shipping documents: Mill test certificate, factory inspection report, full customs clearance documents supplied with cargo
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