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Help CenterSteel Pipe & Tube & Galvanized Steel Pipe，Q195、Q215、Q235B
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Galvanized Steel Pipe Product Detailed Description
Galvanized steel pipe is a steel product with a zinc layer coated on the surface of ordinary steel pipe. It is mainly divided into Hot-Dip Galvanized (Mainstream) and Electro-Galvanized (Eliminated Type). It features high strength, strong corrosion resistance and easy installation, widely used in low-pressure fluid transportation and structural support fields.
1. Product Classification & Manufacturing Process
1.1 Hot-Dip Galvanized Steel Pipe (Recommended)
Process Principle: Made of low-carbon steel substrate. After pickling to remove oxide scale and cleaning, the pipe is immersed in molten zinc liquid at about 450℃ to form a zinc-iron alloy layer + pure zinc layer. The coating is metallurgically bonded to the substrate with strong adhesion.
Core Advantages: Uniform coating (80-100μm), long anti-corrosion service life (20-30 years for outdoor use), high mechanical strength, the first choice for engineering projects.
1.2 Electro-Galvanized Steel Pipe (Prohibited / Eliminated)
Process Principle: Zinc layer is deposited on the steel pipe surface by electrolysis, with thin coating (10-20μm) and layered attachment to the substrate.
Core Disadvantages: Poor corrosion resistance and easy peeling. It has been explicitly eliminated by the construction department. Strictly prohibited for water and gas pipelines, only for temporary indoor non-pressure threading.
2. Substrate Material & Mechanical Properties
2.1 Steel Grade
Mainly made of low-carbon carbon structural steel complying with GB/T 700 standard:
Q195: Good plasticity, used for low-pressure and small-diameter pipelines;
Q215: Excellent comprehensive performance, general-purpose type;
Q235B: Most widely used, yield strength ≥235MPa, tensile strength 370-500MPa, elongation ≥20%;
Q345B low-alloy steel optional for high pressure and corrosive environments.
2.2 Key Mechanical Indicators (GB/T 3091-2025)
Tensile Strength: 370-500MPa
Yield Strength: ≥235MPa (Q235B)
Elongation: ≥20%
Hydrostatic Test: 2.5MPa for standard pipe, 3.0MPa for reinforced pipe, no leakage after 15 seconds pressure holding.
3. Specification Parameters (National Standard GB/T 3091-2025)
3.1 Common Specification Table (Round Pipe)
| Nominal Diameter (DN) | Inch | Outer Diameter (mm) | Standard Wall Thickness (mm) | Reinforced Wall Thickness (mm) |
|---|---|---|---|---|
| DN15 | 1/2" | 21.3 | 2.75 | 3.25 |
| DN20 | 3/4" | 26.9 | 2.75 | 3.5 |
| DN25 | 1" | 33.7 | 3.25 | 4.0 |
| DN40 | 1.5" | 48.3 | 3.5 | 4.25 |
| DN50 | 2" | 60.3 | 3.8 | 4.5 |
| DN100 | 4" | 114.3 | 4.0 | 4.75 |
3.2 General Parameters
Diameter Range: DN15-DN600 (24 inches), customized available;
Length: Standard fixed length 6 meters, customized 3-12 meters non-standard length acceptable;
Zinc Coating: Hot-dip zinc ≥275g/㎡ (double-sided), high-quality grade ≥400g/㎡, thickness ≥80μm.
4. Core Features
Strong Corrosion Resistance: The zinc layer forms physical barrier and electrochemical protection to isolate air and moisture corrosion. The service life of hot-dip galvanized pipe is 3-5 times that of black steel pipe.
Excellent Mechanical Performance: High substrate strength, impact resistance and deformation resistance, suitable for low-pressure fluid transportation (≤1.6MPa).
Convenient Installation: Available for thread, flange and welding connection. The thread is not easy to rust after galvanization with reliable sealing performance.
Cost-Effective: Moderate price, low maintenance cost, better long-term cost performance than stainless steel pipe.
Environmental & Safe: Non-toxic zinc layer, compliant with drinking water hygiene standards, applicable to domestic water supply pipelines.
5. Application Fields
Building Water Supply & Drainage: Indoor and outdoor tap water, fire sprinkler and fire hydrant pipelines (hot-dip galvanized preferred).
Gas Transportation: Low-pressure natural gas and coal gas pipelines, leakage and explosion proof.
HVAC System: Heating steam and air conditioning circulating water pipelines, high temperature resistance and less scaling.
Power & Communication: Cable protection conduit, anti-electromagnetic interference and corrosion resistance.
Agricultural Irrigation: Greenhouse support and farmland water delivery pipeline with excellent weather resistance.
Steel Structure Engineering: Scaffolding, guardrail and support column with high bending rigidity.
6. Executive Standards & Quality Inspection
6.1 Main Executive Standards
GB/T 3091-2025 Welded Steel Pipes for Low-Pressure Fluid Transportation
GB/T 700-2006 Carbon Structural Steels
GB/T 13912-2002 Metallic Coatings — Hot-Dip Galvanized Coatings on Iron and Steel Articles
6.2 Factory Inspection Items
Zinc Coating Test: Weight ≥275g/㎡, thickness ≥80μm, no red rust after 5 times copper sulfate immersion test;
Mechanical Test: Tensile, bending and flattening test, no crack or fracture;
Hydrostatic Test: Pressurized according to specifications, no leakage under pressure;
Appearance Inspection: No surface crack, missing plating or obvious scratch, uniform and bright zinc layer.
7. Installation & Maintenance Guidelines
Before Installation: Check specification, wall thickness and zinc layer quality, clean pipe orifice sundries;
Connection Method: Thread connection for small diameter (≤DN50), flange connection for medium diameter (DN65-DN150), welding connection for large diameter (≥DN200);
Maintenance: Avoid scratching zinc layer with sharp objects, regularly check interface tightness, apply anti-corrosion paint for outdoor pipelines to extend service life.
8. Purchasing Notes
Confirm Process: Prioritize hot-dip galvanized pipe, reject electro-galvanized pipe, check factory certificate marking;
Verify Specifications: Confirm nominal diameter, outer diameter and wall thickness meet design requirements, avoid non-standard products;
Check Zinc Layer: Bright and uniform surface without missing plating or peeling, magnetic thickness gauge testing thickness ≥80μm;
Inspection Documents: Provide material certificate, mechanical performance report and zinc coating test report.
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