Rectangular Hollow Structural Steel Tubes

Rectangular Hollow Structural Steel Tubes are widely used in applications such as steel beams and columns, curtain wall framing, enclosure frameworks, equipment racks, guardrails, and construction machinery. They serve effectively as primary load-bearing components while also being suitable for various architectural shapes and enclosure structures.

Product Features

I. Structural and Mechanical Characteristics

1. The hollow rectangular cross-section provides high stiffness against bending and lateral displacement in both directions. It offers superior resistance to torsion and lateral deformation compared to circular tubes or standard structural steel shapes, ensuring robust overall structural stability.

2. The uniform cross-sectional shape and flat faces ensure even load distribution. Individual tubes can withstand significant vertical and horizontal loads, often serving directly as primary load-bearing members.

3. Available in welded and seamless types: Welded rectangular tubes offer high cost-effectiveness for standard operating conditions; seamless rectangular tubes, lacking weld seams, provide superior strength, pressure resistance, and fatigue performance, making them ideal for heavy-load and cyclic loading scenarios.

II. Appearance and Installation Characteristics

1. Flat outer surfaces facilitate splicing, overlapping, and flush mounting. They fit tightly against color-coated steel sheets, panels, and enclosure components, ensuring clean finishing and edge sealing during construction.

2. Sharp edges and a uniform profile combine load-bearing functionality with aesthetic appeal, making them suitable for architectural facades, landscape frameworks, and other design-oriented projects.

3. For a given load-bearing capacity, they are lighter than solid steel sections, effectively reducing the overall structural load and saving on material costs.

III. Processing and Connection Characteristics

1. They can be cut, beveled, bent, drilled, and welded. Secondary processing is straightforward, facilitating convenient on-site construction.

2. Versatile connection methods—including welding, bolting, and riveting—feature simple joint designs and high installation efficiency.

3. Extensive range of specifications, covering everything from small decorative tubes to large-section load-bearing tubes, allowing for flexible selection.

IV. Corrosion Resistance and Performance Characteristics

1. Supplied in a "black" (uncoated) state; compatible with various anti-corrosion treatments such as hot-dip galvanizing, cold galvanizing, painting, and powder coating, making them suitable for both indoor and outdoor environments (dry or wet).

2. Good cold and hot workability; stable mechanical properties within standard operating temperature ranges.

V. Product Limitations

1. Stress concentration occurs at the corners; these areas are prone to fatigue damage under severe impact or repeated cyclic loading.

2. Poor suitability for fluid transport; rarely used for piping systems, as they are primarily designed for structural load-bearing and framework applications.

3. High production costs for large-specification, thick-walled seamless rectangular tubes result in prices significantly higher than those of welded versions.

Uses and Scope of Application

I. Primary Uses

1. Key Structural Components

Used for factory frames, portal frames, box-section beams and columns, vertical columns, trusses, and floor supports; a core load-bearing material in steel construction.

2. Building Envelopes and Curtain Walls

External wall framing (girts/studs), skylight frames, door and window frames, roof purlins, and edge-trim framing; integrates seamlessly with profiled steel sheets and other panel materials.

3. Enclosures and Protective Facilities

Factory perimeter fencing, road guardrails, stair handrails, balcony railings, site hoarding frames, and safety net posts.

4. Equipment and Machinery Frames

Machinery bases, equipment racks, workbench frames, warehouse racking, container frames, and vehicle chassis frameworks.

5. Engineering and Temporary Facilities

Stage trusses, greenhouse frameworks, temporary construction site hoarding, shoring/support structures, and modular building frameworks.

6. Decorative and Architectural Structures

Landscape structures, outdoor architectural features, interior decorative framing, and display cabinet/booth frameworks; combines load-bearing capability with aesthetic appeal.

II. Application Scope of Rectangular Hollow Structural Steel Tubes

1. Steel Structure Engineering: Beams, columns, and bracing systems for industrial plants, warehouses, stadiums, and prefabricated buildings.

2. Architectural Decoration: Building curtain walls, doors and windows, interior/exterior architectural features, and exhibition stands.

3. Municipal & Transportation: Road guardrails, municipal construction hoardings, landscape pergolas, and bus shelter frameworks.

4. Machinery Manufacturing: Frames for general-purpose equipment, construction machinery, agricultural machinery, and logistics equipment.

5. Warehousing & Logistics: Heavy-duty racking, storage platforms, and container auxiliary structures.

6. Agriculture, Forestry & Horticulture: Greenhouses, livestock shelter frameworks, and agricultural fencing.

Selection Guide

· Welded Rectangular Tubes: Mainstream product type offering high cost-performance; widely used for standard applications such as general load-bearing, building envelopes, decoration, and guardrails.

· Seamless Rectangular Tubes: Superior strength, fatigue resistance, and pressure-bearing capacity; primarily used for heavy-duty applications, cyclic loading, high-specification machinery frames, and heavy-duty engineering components. 

Key Performance Parameters

Implementation Standards: GB/T 6728-2017 "Cold-formed hollow structural sections"; GB/T 3094-2012 "Cold-drawn seamless square and rectangular steel tubes"

I. Common Materials and Mechanical Properties

Additional General Parameters:

· Modulus of Elasticity: 2.06 × 10⁵ MPa

· Density: 7.85 g/cm³

· Standard Operating Temperature: -20°C to 200°C

II. Specification and Dimension System

1. Designation Method

External Dimensions: Length × Width × Wall Thickness (Unit: mm); Example: 100×50×3.0

2. Mainstream Size Categories

· Small (Decoration / Enclosure / Guardrail): 20×10, 30×20, 40×20, 50×30; Wall thickness: 1.2–2.5 mm

· Medium (Keel / Purlin / Standard Beams & Columns): 60×40, 80×40, 80×60, 100×50; Wall thickness: 2.0–5.0 mm

· Large (Primary Columns & Beams / Heavy-duty Trusses): 120×80, 150×100, 200×100, 250×150; Wall thickness: 4.0–12.0 mm

3. Lengths and Tolerances

· Standard Lengths: 6 m, 9 m, 12 m; custom lengths available

· External Dimension Tolerance: ±0.8%

· Wall Thickness Tolerance: Standard welded pipe ±10%; Seamless pipe ±7.5%

4. Theoretical Weight Calculation Formula

W (kg/m) = 0.00785 × [(B + H) × 2 − 4t] × t (B = Long side, H = Short side, t = Wall thickness)

III. Structural Mechanical Properties

1. Rectangular Hollow Structural Steel Tubes rectangular sections offer high bidirectional bending stiffness (along both strong and weak axes) and superior lateral stability and torsional resistance compared to single profiles like circular tubes or H-beams, resulting in robust overall structural stability.

2. Processing Characteristics

· Bending Test: Capable of 90° cold bending at room temperature without cracking or delamination at the bend.

· Flattening Test: Withstands compression to specified dimensions without wall cracking.

1. Stress Characteristics: Slight stress concentration occurs at the corners; not suitable for applications involving high-frequency alternating impact loads.

IV. Product Classification and Performance Differences

V. Surface Treatment and Corrosion Protection

1. Standard Condition: Black finish (hot-rolled oxide surface).

2. Common Corrosion Protection Methods: Hot-dip galvanizing, cold galvanizing, electrostatic powder coating, anti-corrosion painting, and fluorocarbon coating.

3. Hot-dip Galvanizing Reference: Average zinc coating thickness ≥85 μm; outdoor durability exceeds 15 years.

VI. Connection Methods

· Primary: Bevel welding, full-penetration welding (mainstay for construction).

· Secondary: High-strength bolted connections, self-tapping screws, riveting.

· Compatible with various steel structural assemblies, including color steel sheets, H-beams, and angle steel.

VII. Suitable and Prohibited Applications

Suitable

Industrial plant beams and columns, curtain wall framing, enclosure frameworks, guardrails and fencing, warehouse racking, equipment frames, landscape structures, and prefabricated steel structures.

Not Suitable

High-pressure fluid transport, high-temperature/high-pressure piping, and main structures of heavy-duty equipment subject to severe impact or high-frequency fatigue.