Hot Rolled Steel Channel Purlins for Roofing serve as heavy-duty, load-bearing structural members for roofs and walls. Unlike cold-formed thin-walled C- or Z-purlins, they are formed as a single, integral unit directly from hot-rolled steel. This process eliminates internal stresses associated with cold forming and ensures uniform thickness across the web and flanges, making them the ideal replacement choice when the load-bearing capacity of light-gauge steel purlins is insufficient.
Raw Material Compliance: Virgin Hot Rolled Steel Channel Purlins for Roofing are rolled in strict accordance with National Standard GB/T707; the use of recycled/re-rolled non-standard materials is prohibited, and excessive negative wall-thickness deviation is strictly prevented.
Finished Product Processing: Virgin channel steel undergoes fixed-length cutting, stress relief, precision web punching, and end-face deburring; the mechanical properties of the hot-rolled base material remain unaltered, with processing limited to precision finishing for assembly.
Suitable Applications: Steel beam or concrete ring beam bases, heavy-load roofing, suspended platforms for roof-mounted equipment, high-temperature auxiliary facilities in smelting plants, and renovation of aging portal rigid-frame structures.
Prohibited Applications: Standard new light-load factory buildings (spans under 15m) and steep-slope roofs with continuous overlapping; these scenarios offer poor cost-effectiveness and structural suitability.
Indoor Dry/Dust-Free Environments: Sandblasting/rust removal followed by composite paint coating.
Outdoor Humid/Coastal/Chemical Environments: Hot-dip galvanizing for long-term corrosion protection.
No. 8 Channel Steel: 80×43×5mm (Primary material for small-scale renovation projects)
No. 10 Channel Steel: 100×48×5.3mm (Primary material for general heavy-load roofing)
No. 12 Channel Steel: 120×53×5.5mm (Specialized for equipment platforms and areas with heavy snow accumulation)
Round Steel Tie Rods: Φ12, Φ14 Q235 hot-dip galvanized round steel with thread-rolled ends; due to the high hardness of the channel steel web, on-site drilling is prohibited—bolt holes must be pre-fabricated in the factory.
Sleeve struts: Φ32×2.0 welded steel pipe; used for rigid corner support of diagonal tie rods to counteract local shear stress.
Roof knee braces: L40×4 or L50×5 equal-leg angle steel; connects purlins to main beams to resist overturning caused by wind suction.
Purlin cleats: 3.0–5.0 mm hot-rolled steel plate (cut and bent) with pre-drilled bolt holes.
Fastening bolts: M14 or M16 hot-dip galvanized high-strength bolts; sized to fit the large-diameter installation holes in the channel steel.
Direct compatibility: Standard standing-seam color steel sheets, lapped color steel roof panels, and glass wool/rock wool insulation layers.
Matching trim/flashings: Ridge caps, eave flashing, and roof expansion joint trim.
Main material selection: No. 8 hot-rolled channel steel purlins (standard lengths of 6–9 m).
Auxiliary materials: Φ12 single-row simple tie rods; no additional knee braces.
Anti-corrosion treatment: Sa2.5 grade sandblasting + epoxy primer + two coats of topcoat (film thickness ≥80 μm).
Applicable conditions: Roof load ≤0.8 kN/m²; no suspended equipment; dry inland regions.
Main material selection: No. 10 or No. 12 thickened channel steel; purlin spacing reduced as required. Auxiliary materials: Φ14 closely spaced tie rods; angle steel knee braces installed at 100% of purlin locations.
Anti-corrosion treatment: Spray painting for indoor use; hot-dip galvanizing for outdoor use.
Applicable conditions: Roof supports additional loads such as ventilators, photovoltaic systems, or maintenance personnel traffic.
Material Selection: Sizes ranging from No. 8 to No. 12 (selected based on requirements).
Anti-corrosion Standard: Purlins, tie rods, knee braces, and purlin brackets all feature a galvanized coating thickness of ≥120μm to eliminate galvanic corrosion between components.
Installation Details: Anti-corrosion gaskets are installed between purlin brackets and main beams to break the path for electrochemical corrosion.
Hot Rolled Steel Channel Purlins for Roofing: The hot-rolled base material has uniform wall thickness and no residual stress from cold forming; it withstands lateral heavy-object impacts and concentrated snow loads without section buckling or denting.
C/Z Purlins: Thin-walled and cold-formed; concentrated loads exceeding limits cause immediate bending or tearing, making them unsuitable for suspending equipment.
Channel Steel Purlins: Densely rolled base material; no lateral twisting occurs during short-term exposure to temperatures up to 400°C, making them suitable for boiler rooms and smelting workshops.
C/Z Purlins: Thermal stress releases rapidly in thin-walled sections, leading to easy lateral buckling and collapse; often fails fire safety inspections.
Channel Steel Purlins: Sufficient web thickness allows for arbitrary drilling and welding of pipeline supports without compromising the section's overall load-bearing capacity.
C/Z Purlins: A single hole with a diameter exceeding 12mm significantly reduces flexural strength, severely limiting future modifications.
Cost and Self-Weight Limitations: For the same span, self-weight is over 60% higher than C-section steel, increasing main beam and foundation construction costs by 12%–15%.
Structural Limitations: Flat flanges prevent overlapping for extended lengths, making them unsuitable for continuous load-bearing designs on steep-slope roofs.
Visual Inspection: Check for channel steel twisting, flange cracking, edge/corner deformation, and surface delamination.
Parameter Verification: Spot-check web thickness and flange width tolerances; verify mill material quality certificates; conduct spectral re-testing for Q235B grade steel.
Cut-to-Length: Precision plasma cutting; cut-face perpendicularity deviation ≤ 1mm.
Stress-Relief Punching: Hole placement ≥ 1.5 times the hole diameter from the flange; avoid the central web stress-weak zone to prevent tearing under load.
End-Face Grinding: Remove burrs from cut edges and holes to prevent damage to the anti-corrosion coating during transport and injuries to installation personnel.
Paint Coating Route: Shot blasting (Sa2.5) for rust removal → dust blow-off → epoxy primer spraying → double-layer topcoat spraying → 72-hour ambient temperature curing.
Hot-Dip Galvanizing Route: Acid pickling/degreasing → water rinsing → flux immersion → hot-dip galvanizing at 450–460°C → air cooling/passivation → grinding of surface zinc nodules.
Dimensional & Geometric Inspection: Full inspection of straightness, twist/deflection, and hole spacing.
Anti-Corrosion Spot Check: On-site thickness verification using paint film and galvanizing layer thickness gauges.
Storage & Packaging: Steel pallet bundling; marking with model, material, and anti-corrosion specifications; moisture-proof stretch-wrap packaging for sea transport.
|
Channel Size |
Height h(mm) |
Leg Width b(mm) |
Web Thickness d(mm) |
Theoretical Weight(kg/m) |
|
8# |
80 |
43 |
5.0 |
8.045 |
|
10# |
100 |
48 |
5.3 |
10.007 |
|
12# |
120 |
53 |
5.5 |
12.059 |
Material: Q235B hot-rolled carbon structural steel
Mechanical Strength: Yield strength ≥ 235 MPa; tensile strength 375–500 MPa
Thermal Expansion Coefficient: 1.2 × 10⁻⁵/°C; expansion gaps required for long-span roofing
Paint-based anti-corrosion: Total composite coating thickness ≥ 80 μm
Hot-dip galvanizing: ≥ 80 μm for standard inland areas; ≥ 120 μm for coastal or chemical corrosion zones
1. Can Hot Rolled Steel Channel Purlins for Roofing replace Z-shaped purlins for steep-slope roofing?
Answer: No. Channel steel features flat flanges, which causes eccentric loading on sloped roofs and prevents continuous load-bearing through overlapping; this makes the purlins highly prone to overturning over time, so they are suitable only for flat installation.
2. Do auxiliary components for coastal projects require separate galvanizing?
Answer: Yes. Potential differences between different steel materials accelerate corrosion; HAISHENG applies the 120 μm galvanizing standard to all auxiliary components by default, so customers do not need to source them separately.
3. What is the difference between on-site hole drilling and factory pre-drilling for channel steel?
Answer: On-site drilling lacks stress relief, creating a high risk of web tearing; factory pre-drilling follows national standards for hole spacing without compromising structural load-bearing capacity, and is a mandatory requirement for overseas projects.
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