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Help CenterSquare Steel ， Rectangular Tube，S235JR、S355JR（EN10219）、ASTM A500 Gr.B/C、A53 Grade B、SS400、STK400、STKR490、ST37、ST52
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1. Product Overview
Square tube, fully named Square Hollow Section (SHS), is a hollow structural steel pipe. It is produced by cold forming steel strips followed by high-frequency welding and shaping. Featuring equal four-sided cross-section and neat right angles, it combines high strength with light weight, serving as a core general profile for construction, machinery and steel structure industries. Rectangular Hollow Section (RHS) can be supplied together for one-stop purchasing.
Core Advantages
Uniform stress bearing: Symmetrical square cross-section delivers superior bending and compression resistance than round tubes, ensuring outstanding structural stability.
Convenient processing: Easy to cut, weld, drill and bend for high on-site assembly efficiency.
Cost-saving: Hollow structure reduces self-weight under identical load-bearing requirements, lowering material and transportation costs significantly.
Neat appearance: Smooth right-angle edges ideal for exposed frames and decorative applications.
Diverse anti-corrosion options: Black finish, oil coating, paint coating and hot-dip galvanized finishes are available to suit all indoor and outdoor scenarios.
2. Production Process
Raw hot-rolled/cold-rolled steel strip → Uncoiling & leveling → Cold forming → High-frequency ERW longitudinal welding → Weld grinding & smoothing → Straightening & shaping → Fixed-length cutting → Non-destructive testing (eddy current/ultrasonic inspection) → Anti-rust treatment → Finished product inspection → Packing & delivery
General engineering grade: High-frequency welded square tubes with cost performance advantages.
High-precision grade: Cold-drawn seamless square tubes with weld-free surface and tiny dimensional tolerance.
Heavy-load heavy-duty grade: Hot-formed thick-wall square tubes for bridges and large equipment bases.
3. Material Grades
Chinese National Standard GB/T 6728
Q195: Thin-wall lightweight type for shelves, furniture and simple enclosures.
Q235B: General carbon steel for factory buildings, guardrails and ordinary steel structures (mainstream market grade).
Q355B/C/D/E: High-strength low-alloy steel for engineering machinery, bridges and large-span workshops.
20#/45# Seamless Square Tube: Precision equipment and hydraulic supports.
International Equivalent Grades for Export
European Standard: S235JR, S355JR (EN10219)
American Standard: ASTM A500 Gr.B/C, ASTM A53 Grade B
Japanese Standard: SS400, STK400, STKR490
German Standard: ST37, ST52
4. Complete Specification Parameters
4.1 Size Range
Square side length: 10×10mm ~ 600×600mm, customized extra-large diameters acceptable
Wall thickness: 0.7mm ~ 20mm, full coverage of thin, medium and heavy wall thicknesses
Standard lengths: 6m, 9m, 12m (6m/12m preferred for export); customizable cut lengths from 0.5m to 26.5m
4.2 Dimensional Tolerance
Side length deviation ±0.5%, wall thickness deviation ±5%, straightness ≤1.5mm/m, free of distortion, warped corners and burrs on flat cut ends.
4.3 Mechanical Properties
| Material Grade | Yield Strength | Tensile Strength | Elongation |
|---|---|---|---|
| Q235B | ≥235MPa | 375–500MPa | ≥21% |
| Q355B | ≥355MPa | 470–630MPa | ≥21% |
5. Surface Finishes
Black Mill FinishAs-produced black oxide surface coated with anti-rust oil, lowest cost, suitable for indoor steel structures and factory columns.
Hot-dip Galvanized Square TubeZinc coating weight 60–275g/㎡, anti-corrosion service life 20–50 years, applicable for outdoor solar brackets, guardrails, greenhouses and coastal projects.
Painted / Powder CoatedRed/grey/black anti-rust paint for good appearance and rust resistance, used for furniture and decorative frames.
Bright Polished Cold-drawn FinishSmooth oxide-free surface for precision equipment and medical machinery frames.
6. Implementation Standards
China: GB/T 6728-2017 Cold-formed Hollow Structural Sections for Construction, GB/T 3094 Cold-drawn Special-shaped Steel Tubes
Europe & America: EN 10219, ASTM A500, ASTM A501
Japan: JIS G3466
Available Certifications: ISO9001, CE, SGS material test reports, original mill certificates can be provided.
7. Application Fields
Building Steel StructureFactory columns, floor supports, curtain wall keels, temporary construction enclosures, scaffolding, bridge guardrails
Machinery ManufacturingFrames of construction machinery, machine tool bases, automated equipment frames, conveyor guide rails, agricultural machinery chassis
Transportation & LogisticsTruck carriage borders, auxiliary container frames, bus and forklift supports
Photovoltaic & Agriculture IndustrySolar photovoltaic brackets, greenhouse frames, breeding fences, farm protection frames
Civil DecorationWarehouse storage racks, office furniture, fitness equipment, stage trusses, outdoor leisure tables and chairs
8. Packing, Delivery & After-sales Service
Packing: Bundled with steel strapping, 1–3 tons per bundle; galvanized tubes lined with waterproof plastic film, plastic end caps to prevent collision damage; custom wooden pallet packaging available upon request.
Minimum Order Quantity: 10 tons for regular orders; small spot goods can be delivered in small batches.
Lead Time: 5–7 days for in-stock items, 7–12 days for customized special specifications.
Quality Inspection: Batch-by-batch chemical composition test, mechanical tensile test and flattening test before delivery; material certificates and customs documents attached.
After-sales Service: Free replacement or return for non-compliant size and material; full logistics tracking service provided.
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