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Steel Pipe & Tube & Galvanized Steel Pipe，Q235B、Q195、Q215B、Q355BNegotiableMOQ: 5 Metric Tons -
Steel Pipe & Tube & Galvanized Steel Pipe，Q235B、Q195、Q215B、Q355BNegotiableMOQ: 5 Metric Tons
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Steel Pipe & Tube & Galvanized Steel Pipe，Q235B、Q195、Q215B、Q355BNegotiableMOQ: 5 Metric Tons
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Galvanized Steel Pipe Product Specification
1. Product Overview
Galvanized steel pipe is manufactured from low-carbon straight seam welded steel pipe via hot-dip galvanizing for anti-corrosion treatment (the mainstream product for engineering; cold-galvanized pipes are prohibited by the Ministry of Housing and Urban-Rural Development for main water supply and gas pipelines). Relying on the sacrificial anode anti-corrosion principle of zinc coating, it isolates air, moisture and acid-base medium to realize long-term rust prevention. Widely applied in fire protection, water supply & drainage, gas supply, HVAC and steel structure projects, manufactured in accordance with national standard GB/T3091-2025 Welded Steel Pipes for Low-Pressure Fluid Transportation.
2. Base Material & Chemical Composition
2.1 Common Steel Grades
Standard grade: Q235B (for general engineering); optional customized grades: Q195, Q215B, Q355B (thickened high-pressure type)
2.2 Reference Chemical Composition (per national standard)
C ≤0.22%, Mn ≤1.4%, Si ≤0.35%, S ≤0.045%, P ≤0.045%. Low-carbon structure features excellent ductility for welding, threading and machining.
2.3 Mechanical Properties
Yield Strength: Q235B ≥235MPa, Q355B ≥355MPa; Tensile Strength ≥375MPa; eligible for cold bending, threading, cutting and flange welding processing.
3. Production Process (Hot-Dip Galvanizing per National Standard)
Raw black pipe inspection → degreasing & oil removal → pickling for oxide skin removal → water rinsing → flux dipping (ammonium chloride + zinc chloride) → drying → hot dipping in molten zinc at 450℃±5℃ for 1~2 minutes → air cooling → passivation & sealing → trimming, hydrostatic test, finished inspection → packing & warehousing
Cold galvanizing (electro-galvanizing): Zinc coating formed by electrolysis under ambient temperature with thin coating (10～30g/㎡) and poor adhesion, only applicable for temporary steel structure and electrical conduit; forbidden for portable water and fire service pipelines.
4. Technical Specification of Zinc Coating (GB/T3091-2025)
Coating Weight: Standard ≥300g/㎡, customized heavy anti-corrosion ≥500g/㎡
Coating Thickness: Average ≥80μm, single point ≥70μm
Adhesion: No peeling or falling off after hammer impact test; no substrate exposure after ≥4 times copper sulfate immersion test
Surface Appearance: Silver-grey finish; minor zinc bumps and water grain marks acceptable, no bare iron, blisters or missing galvanized patches.
5. Dimension Specification (Nominal DN, Outer Diameter & Wall Thickness)
Standard fixed length: 6 meters per piece, customized length (3m/9m/12m) available; classified into Standard Wall & Extra Thick Wall types:
| Nominal DN | Inch Size | Outer Diameter(mm) | Standard Wall(mm) | Extra Thick Wall(mm) |
|---|---|---|---|---|
| DN15 | 1/2" | 21.3 | 2.75 | 3.25 |
| DN20 | 3/4" | 26.9 | 2.75 | 3.50 |
| DN25 | 1" | 33.7 | 3.25 | 4.00 |
| DN32 | 1-1/4" | 42.4 | 3.25 | 4.00 |
| DN40 | 1-1/2" | 48.3 | 3.50 | 4.25 |
| DN50 | 2" | 60.3 | 3.50 | 4.50 |
| DN65 | 2-1/2" | 76.1 | 3.75 | 4.50 |
| DN80 | 3" | 88.9 | 4.00 | 4.75 |
| DN100 | 4" | 114.3 | 4.00 | 5.00 |
| DN150 | 6" | 168.3 | 4.50 | 6.00 |
Tolerance: Wall thickness ±10% for standard pipe, ±12.5% for extra thick pipe; outer diameter tolerance ≤±0.8% of nominal OD.
6. Factory Inspection Items
Hydrostatic Pressure Test: Test pressure 3.0MPa for pipes ≤DN150 (OD168.3), 5.0MPa for larger sizes; no leakage or bulge permitted under pressure holding.
Bend Test: 90° cold bend test for pipes ≤DN50 without crack occurrence.
Zinc Coating Test: Gravimetric coating weight test & copper sulfate immersion test.
Dimensional Spot Check: Random inspection on OD, wall thickness, length and straightness.
7. Core Product Advantages
Superior Anti-corrosion Performance: Metallurgical bonded zinc-iron alloy coating; service life 20~30 years in rural environment, 10~15 years in humid industrial area, far longer than black welded pipe & paint-coated pipe.
Convenient Installation: Pipe ends available for threading, flange connection or welding; full matching pipe fittings in stock.
Safe & Eco-friendly: Non-toxic recyclable zinc coating; no inner rust debris shedding, compliant with sanitary requirement for low-pressure fluid delivery.
Cost-effective: Higher upfront cost than bare black pipe, while eliminating regular anti-rust painting expense for long-term lower life-cycle cost.
8. Application Scope
Fire Protection Engineering: Fire hydrant pipeline & sprinkler main piping (specified pipe for national fire code)
Fluid Conveyance: Municipal tap water, city gas, compressed air and low-temperature steam (≤1.6MPa low-pressure fluid)
HVAC & Heating: Construction site heating pipeline and factory circulating water system
Auxiliary Steel Structure: Greenhouse frame, guardrail, electrical conduit, equipment support and embedded pipeline for curtain wall.
9. Storage & Installation Precautions
Storage: Keep under covered warehouse, elevate off ground; avoid long-term open-air exposure under rain and sunlight.
Connection: Use PTFE tape for threaded joint; touch-up with zinc-rich paint on welding spots after weld completion for supplementary anti-corrosion.
Restricted Usage: Not recommended for concentrated strong acid/alkali chemical liquid or high-pressure & high-temperature service over 1.6MPa.
10. Delivery Terms
Standard spot goods in 6m fixed length, shipped from Tianjin Port with lead time 5~7 working days. Customization on non-standard wall thickness, length and heavy zinc coating is acceptable; one-stop supply of matched fittings (elbow, tee, nipple etc.) available.
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