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Help CenterSteel Pipe & Tube & Galvanized Steel Pipe，Q235B、Q195、Q215A/B、Q355B
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Galvanized Steel Pipe Product Specification
Galvanized steel pipe refers to welded steel pipe coated with hot-dip or electro-galvanized layer. The zinc coating isolates the steel substrate from air and moisture, greatly improving corrosion resistance and service life. Hot-dip galvanized steel pipe is widely used in engineering, while cold-dip galvanized steel pipe is prohibited for water supply and other critical applications.
1. Product Classification & Manufacturing Process
1.1 Hot-dip Galvanized Steel Pipe (Mainstream Type)
After degreasing and pickling to remove oxide scale, the steel pipe is immersed in molten zinc liquid at 450℃±5℃ for 1 to 2 minutes. A dual protective layer consisting of zinc-iron alloy layer and pure zinc layer is formed on the surface.
Advantages: Uniform and compact coating with strong adhesion. For pipes with wall thickness over 6 mm, the zinc layer thickness is no less than 85 μm. It can withstand 720 hours of neutral salt spray test without red rust, and its service life exceeds 30 years in rural environments.
1.2 Cold-dip Galvanized Steel Pipe (Electro-galvanized, Restricted Use)
Zinc layer is deposited on the pipe surface via electrolysis. The zinc thickness ranges from 10 to 50 g/m², and the coating is poorly bonded to the substrate.
Disadvantages: Poor corrosion resistance and easy peeling. It also poses environmental risks. It has been banned for drinking water pipeline use in China since 2000, and is only applied to temporary or low-standard projects.
2. Material & Execution Standards
2.1 Base Material
Main grade: Q235B (mild carbon steel, balanced strength and cost performance)
Alternative grades: Q195, Q215A/B, Q355B (high strength grade)
2.2 Implementation Standards
National Standard: GB/T 3091-2025, applicable to low-pressure fluid delivery (water, gas, air, etc., working pressure ≤ 1.6 MPa)
Galvanized layer requirements: Total zinc coating weight ≥ 300 g/m² (customized ≥ 500 g/m² available); average thickness ≥ 80 μm, local thickness ≥ 70 μm.
3. Common Specifications & Parameters
3.1 Dimension Specification (DN = Nominal Diameter)
| Nominal Diameter DN | Outer Diameter (mm) | Wall Thickness (mm) | Typical Application |
|---|---|---|---|
| DN15 (1/2") | 21.3 | 2.75 | Domestic water supply & drainage, small pipelines |
| DN20 (3/4") | 26.9 | 2.75 | Domestic water supply, gas pipeline |
| DN25 (1") | 33.7 | 3.25 | Building fire protection, heating & ventilation |
| DN50 (2") | 60.3 | 3.5 | Municipal fire protection, industrial fluid delivery |
| DN100 (4") | 114.3 | 4.0 | Urban water supply, large-diameter pipelines |
3.2 Length & Weight
Standard fixed length: 6 meters (tolerance: ±10 mm). Custom lengths of 9m and 12m are acceptable.
Weight calculation: Weight of galvanized pipe = Theoretical weight of black steel pipe × galvanizing coefficient (Coefficient: 1.064 - 1.028 for wall thickness 2.0 - 4.5 mm).
3.3 Mechanical Properties
Tensile strength: ≥ 300 MPa, retaining original compression and impact resistance.
Hydrostatic test: Test pressure 2.5 - 5.0 MPa for DN15-DN100, hold pressure for 15 seconds without leakage.
Bend test: Pipes below DN50 show no cracks after 90° bending.
4. Key Features
Excellent Corrosion Resistance: Based on sacrificial anode protection principle. Zinc corrodes preferentially to protect the steel substrate when the coating is damaged. Outdoor service life reaches 20-30 years, 3 to 5 times longer than ordinary steel pipes.
Safe & Eco-friendly: Non-toxic zinc layer, compliant with standards for drinking water delivery systems.
Easy Installation: Compatible with thread connection, welding and flange connection, suitable for conventional construction methods.
Cost-effective: Lower price compared with stainless steel pipes, with balanced performance for most low-pressure working conditions.
5. Application Fields
Construction Engineering: Fire pipelines, heating & ventilation systems, scaffolding, roof drainage pipes.
Municipal Engineering: Urban water supply, gas transmission, road guardrails, tunnel pipelines.
Industrial Field: Cable protection pipes, mechanical frames, heat exchange pipes, petroleum delivery pipes.
Agriculture: Greenhouse frames, farmland irrigation pipelines, breeding fences.
6. Packaging & Marking
Packaging: Bundled with steel strips. Standard 6m pipes are fitted with plastic end caps to protect threads and prevent moisture and rust.
Marking: Specifications, material grade, standard number, production date and manufacturer information are marked on each bundle. Product quality certificates are provided together.
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