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Help CenterSteel Pipe & Tube & Cast Iron Pipe，HT，GB/T9439、GB/T12772，QT，GB/T13295，ZG，GB/T11352
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Product Specification of Cast Pipes（Updated with Material Grade）
1. Product Overview
Cast iron pipe is manufactured from high-quality pig iron via smelting, spheroidization/inoculation treatment, centrifugal casting or continuous pouring. It is categorized into three main types: Ductile Iron Pipe for pressure service, Grey Cast Iron Pipe for drainage and High Silicon Corrosion-resistant Cast Pipe. Combining superior anti-corrosion property & vibration-damping performance of cast iron and high strength & toughness of steel, cast pipes serve as core pipeline materials for municipal water supply & drainage, gas transmission and industrial fluid conveyance. Production complies with domestic standards GB/T13295-2019, GB/T12772-2016, as well as international norms ISO2531, EN545 and EN598.
1.1 Classification by Material & Material Grade
(1) Ductile Iron Pipe (for water & gas supply)
Material Grade: QT450-10 (China GB), EN-GJS-450-10 (EU Standard), ISO JS450-10Molten iron is treated with magnesium or rare-earth magnesium nodulizer to form spherical graphite structure, delivering steel-level performance at cast iron cost. Wall thickness grades K7/K8/K9 are commonly adopted domestically (Grade K9 as standard for engineering). Working pressure reaches up to 6.0MPa with complete specifications ranging DN80~DN2600; standard single length is 6 meters, while 5m or 8m customized lengths are available.Mechanical Properties: Tensile strength ≥420MPa, Elongation ≥7%, Yield strength ≥300MPa, Brinell Hardness HB140~210.
(2) Grey Cast Iron Pipe (for gravity drainage only)
Material Grade: HT200 (China GB), EN-GJL-200 (EU Standard)Featured with flake graphite structure, it stands out for outstanding noise reduction and cost efficiency yet relatively high brittleness with maximum allowable working pressure ≤0.3MPa. Widely applied for building rainwater & sewage gravity drainage in residential zones, specification DN50~DN1200, fixed length 3m or 6m.Mechanical Properties: Tensile strength ≥150MPa with no elongation requirement.
(3) High Silicon Cast Pipe (for severe corrosive medium)
Material Grade: STSi15 (China GB high silicon cast iron grade)Silicon content ranges from 14% to 16%, featuring excellent resistance to strong acid and industrial wastewater, suitable for chemical sewage pipeline and pickling process piping.
1.2 Classification by Casting Technology
Water-cooled Metal Mold Centrifugal Casting (Dominant Process): High-speed centrifugal forming produces compact pipe wall free of blowholes with uniform wall thickness (tolerance ≤5%) and smooth inner surface Ra3.2~6.3, preferred for potable water and gas pipelines.
Continuous Sand Casting: Horizontal continuous pouring with low production cost, major processing technique for small & medium bore grey drain pipes.
Resin Sand Molding: Outdated craft with rough surface, only sporadically used for non-standard low-pressure pipelines and being phased out gradually.
1.3 Classification by Joint Type
Type T Push-in Flexible Joint (Most Popular for Construction): Sealed by EPDM rubber gasket. Allowable deflection: 4° for DN200~DN300, 3° for DN350~DN600, 2° for DN≥700. Capable of accommodating uneven foundation settlement with seismic resistance up to Grade 9, easy for assembly and disassembly.
Type N1/X Self-anchored Joint: Built-in anti-pullout locking structure, designed for overhead pipelines, steep slope and river-crossing piping to prevent pipe separation.
Flanged Joint: Sealed via bolt and rubber gasket, applicable for PN10/PN16 high-pressure working condition to connect valves, water pumps and steel pipes.
Traditional rigid cement joint: Obsolete, only seen in sporadic old pipeline renovation projects.
2. Internal & External Anti-corrosion Coating Configuration
2.1 Ductile Iron Pipe for Potable Water Supply
Inner Lining: Cement Mortar Coating (ISO4179 compliant): Centrifugally coated silicate cement lining, minimum thickness ≥3mm for DN≤300, ≥5mm for DN＞300. Smooth inner surface avoids scaling and secondary water pollution.
External Coating: Zinc Spraying + Asphalt Paint: Zinc coating ≥130g/㎡ works as sacrificial anode for corrosion protection; outer asphalt layer isolates soil acid-base erosion, guaranteeing over 50-year underground service life.
2.2 Sewage & Rainwater Drainage Cast Pipe
Thickened cement mortar or epoxy ceramic inner lining, regular asphalt outer coating; optional 3PE anti-corrosion coating (epoxy primer + adhesive + PE outer sheath) for pipeline buried in heavily corrosive soil.
2.3 Gas Transmission Cast Pipe
Bare inner surface without lining or thin epoxy coating; standard 3PE outer anti-corrosion layer against soil electrochemical corrosion and ground settlement damage.
3. Regular Specification List (National Standard)
| Nominal Diameter DN | Outer Diameter(mm) | K9 Wall Thickness(mm) | Normal Working Pressure | Single Pipe Length | Applicable Material Grade |
|---|---|---|---|---|---|
| DN100 | 118 | 6.1 | 1.6MPa | 6m | QT450-10/EN-GJS-450-10 |
| DN300 | 326 | 8.6 | 1.6MPa | 6m | QT450-10/EN-GJS-450-10 |
| DN600 | 635 | 10.9 | 1.0MPa | 6m | QT450-10/EN-GJS-450-10 |
| DN1000 | 1048 | 13.5 | 0.8MPa | 6m | QT450-10/EN-GJS-450-10 |
Note: K7/K8 have thinner wall than K9 for low-pressure irrigation and water diversion; Grade C (C25/C30) classified by pressure is widely exported to European & American markets. Grey drain pipes adopt HT200; anti-corrosion acid-resistant pipes adopt STSi15.
4. Production Flow Chart
Pig Iron from Blast Furnace → Medium Frequency Furnace Melting → Chemical Composition Adjustment → Spheroidization & Inoculation → Water-cooled Metal Mold Centrifugal Casting → High-temperature Annealing (eliminate casting stress) → Pipe End Machining → Hydrostatic Pressure Test → Curing of Inner Cement Mortar Lining → External Zinc Spraying & Asphalt Coating → Mark Spraying → Finished Product Storage → Re-inspection before DeliveryMandatory Factory Test: Hydrostatic test for every single pipe: Test pressure 3.2MPa for DN≤300, 2.5MPa for DN≥400; qualified with zero leakage under holding pressure.
5. Core Product Advantages
Earthquake & Settlement Resistant: Flexible joints permit ±30mm radial displacement and angular deflection to avoid cracking & leakage under ground subsidence or geological collapse.
Extra-long Service Life: 50~80 years for regular underground installation, minimum 40 years in coastal saline & chloride-containing soil, far longer than PE pipe and steel pipe.
Superior Anti-corrosion: Inherent natural resistance of cast iron against soil electrochemical corrosion; matched coatings adapt to potable water, sewage and gas conveying conditions.
Fast Construction: Type T joint can be assembled manually without welding or adhesive bonding to shorten construction cycle remarkably.
Noise Reduction & Eco-friendly: Grey & ductile iron features outstanding vibration absorption to eliminate flowing noise, ideal for indoor vertical drainage pipes.
Cost-effective: Lower procurement cost than seamless steel pipe under identical pressure rating with minimal later maintenance expenditure.
6. Application Fields
Municipal Engineering: Urban tap water network, rain-sewage separation pipeline, long-distance water diversion project, urban utility tunnel.
Gas Industry: Buried urban natural gas & coal gas distribution pipeline.
Building Water Supply & Drainage: Indoor & outdoor rainwater and sewage gravity drainage for high-rise buildings and residential communities.
Agriculture & Water Conservancy: Farmland irrigation, water conveyance pipeline for reservoir auxiliary facilities and water plant pump room.
Industrial & Mining Projects: Reclaimed water for power plants, underground mine water supply & drainage, low-corrosion industrial medium conveyance; STSi15 high silicon cast pipe for strong acid chemical pipeline.
7. Matching Fittings
Complete set of same-material ductile iron fittings including elbow, tee, reducer, flanged socket, blind flange and repair clamp for seamless sealing and one-stop procurement.Fitting Material Grade: Consistent with pipes, QT450-10 for ductile iron fittings, HT200 for grey iron fittings.
8. Storage, Transportation & Installation Guidance
Warehousing: Stack pipes on sleepers outdoors, seal pipe ends to prevent dust ingress and avoid collision on socket sealing surface by sharp hard objects.
Lifting Operation: Use soft slings instead of steel wire rope directly binding coated pipe ends.
Installation: Clean spigot surface evenly, apply lubricant on rubber gasket, insert spigot slowly into socket and reserve expansion gap; backfill with fine sand for compaction preferentially.
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