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Casting Pipe Product Detailed Specification
Casting pipes (commonly known as cast iron pipes) are metal pipes formed by melting iron water through centrifugal casting, continuous casting and other processes. They are core fluid transportation pipes for municipal, water conservancy, industrial and construction projects. Featuring high rigidity, excellent corrosion resistance, stable pressure resistance, ultra-long service life and convenient installation, the products are mainly divided into three series: gray cast iron pipe, ductile iron pipe and high silicon corrosion-resistant cast iron pipe. Each series is equipped with exclusive material models to adapt to different working conditions.
I. Core Product Classification & Complete Material Grades
This chapter specifies national standard material grades, subdivided models, material characteristics, mechanical parameters and applicable scenarios of all categories, covering all conventional and special working conditions for casting pipes.
1. Gray Cast Iron Pipe (Ordinary Casting Pipe)
With flake graphite structure, gray cast iron pipes feature high hardness, good wear resistance and low cost, but have low toughness and poor impact resistance. They are mainly applied to low-pressure and non-impact water supply and drainage scenarios as traditional general-purpose casting pipes.
1.1 Core Material Grades (National Standard)
HT150: Basic low-pressure grade with soft texture and low strength. It is only applicable to non-pressure gravity drainage and simple residential area sewage pipelines. Tensile strength ≥150MPa; no pressure bearing capacity; prone to slight deformation.
HT200 (Mainstream General Grade): General-purpose gray cast iron material with balanced comprehensive performance, qualified hardness and tightness. It is the dominant grade for building drainage and municipal rainwater pipelines. Tensile strength ≥200MPa, suitable for conventional low-pressure working conditions.
HT250: High-strength gray cast iron material with uniform wall thickness and enhanced compression resistance. It is used for large-diameter gravity sewage discharge and factory non-pressure industrial wastewater transportation, with better rolling resistance than HT200. Tensile strength ≥250MPa.
1.2 Matching Pipe Types
Classified by production process: continuous gray cast iron pipe, sand mold centrifugal gray cast iron pipe; main interface types: Type W, Type B and Type A interfaces specially for building drainage.
2. Ductile Iron Pipe (High-Performance Casting Pipe, Industry Mainstream)
Treated by spheroidization and inoculation, the graphite of ductile iron pipes presents a spherical structure. It combines the corrosion resistance and wear resistance of cast iron with the high toughness, high tensile strength, settlement resistance and impact resistance of steel, serving as the core pipe for municipal water supply, high-pressure water delivery and gas transmission.
2.1 Core Material Grades (National Standard)
QT400-15: High-toughness ductile iron grade with an elongation rate up to 15%. It has excellent resistance to foundation settlement, earthquake and torsion, suitable for water transmission pipelines in complex working conditions such as soft soil foundation, river courses and earthquake zones. Tensile strength ≥400MPa, elongation ≥15%.
QT500-7 (National Standard General Main Grade): Industry standard general material with balanced strength and toughness and high cost performance. It is widely used for urban municipal water supply main pipes, farmland irrigation and conventional water conservancy projects. Tensile strength ≥500MPa, elongation ≥7%, serving as the common base material for K7/K8/K9 grade pipes.
QT600-3: High-strength rigid ductile iron grade with high hardness and strong external pressure rolling resistance. It is applicable to deeply buried pipelines, heavy-load road pipelines, factory high-pressure water delivery and industrial circulating water pipelines. Tensile strength ≥600MPa, elongation ≥3%.
2.2 Wall Thickness & Pressure Rating Grades (Matching Material Classification)
Based on QT500-7 material, classified by pressure-bearing wall thickness: K7, K8, K9, K10, K12
K7: Light-duty, for low-pressure municipal branch pipes and residential water supply, working pressure ≤1.0MPa
K8: Medium-duty, for conventional urban water supply pipelines, working pressure ≤1.2MPa
K9: National standard standard type, first choice for engineering, general pressure resistance 1.6MPa, applicable to most municipal and water conservancy projects
K10/K12: Heavy-duty high-pressure type, for deeply buried, high-pressure water transmission and river-crossing pipelines, working pressure ≥2.0MPa
3. High Silicon Corrosion-Resistant Cast Iron Pipe (Special Anti-Corrosion Casting Pipe)
Made of special alloy cast iron, this product features excellent strong corrosion resistance for chemical acid-base and corrosive wastewater media. It has high brittleness and cannot bear impact or high pressure.
3.1 Core Material Grades (National Standard)
STSi15: Ordinary high silicon cast iron with silicon content of 14.5%~16%, resistant to dilute sulfuric acid and organic acid corrosion, suitable for low-pressure chemical wastewater transportation.
STSi15R: Heat-resistant high silicon cast iron with high temperature corrosion resistance, applicable to high-temperature chemical waste liquid and smelting corrosive flue gas pipelines.
STSi17: Upgraded high corrosion resistance grade with silicon content of 16%~18%, resistant to concentrated acid and strong corrosive media, specially used for chemical strong acid transmission.
II. Classification by Casting Process
1. Centrifugal Cast Iron Pipe (Mainstream Process)
Iron water is evenly attached to the mold wall by the centrifugal force of a high-speed rotating mold, producing pipes with dense structure, uniform wall thickness, no sand holes and good tightness. It is divided into sand mold centrifugal casting (low cost, suitable for gray cast iron pipes) and water-cooled metal mold centrifugal casting (high precision, suitable for high-performance ductile iron pipes).
2. Continuous Cast Iron Pipe
Formed by one-time horizontal continuous casting with high production efficiency and regular dimensions. It mainly adopts HT200 and HT250 gray cast iron materials, mostly used for building drainage and low-pressure rainwater pipe networks.
III. Classification by Interface Type
Flexible Type T/K Interface: Mainstream for ductile iron pipes, sealed with rubber rings, allowing ±2.5° deflection to adapt to foundation settlement. Weld-free and fast-installation, widely used in municipal engineering.
Flange Interface: Connected by flange bolts with high sealing performance, suitable for high-pressure, large-diameter pipelines and industrial pipelines requiring frequent maintenance.
Type W/B/A Clamp Interface: Special for gray cast iron building drainage, connected by stainless steel clamps with flexible disassembly and good tightness, applicable to indoor and outdoor building sewage pipelines.
IV. Core Technical Parameters
4.1 Specification & Dimension
Nominal Diameter: DN50–DN2600mm; Standard single pipe length: 6m (customizable 4–9m); Wall thickness grades: K7/K8/K9/K10/K12 (for ductile iron pipes) with national standard uniform wall thickness tolerance.
4.2 Mechanical Performance Summary of All Material Grades
Material Grade |
Tensile Strength (MPa) |
Elongation (%) |
Applicable Pressure |
Core Application |
HT150 |
≥150 |
Nearly no elongation |
Non-pressure |
Simple gravity drainage |
HT200/HT250 |
≥200/≥250 |
Nearly no elongation |
Low-pressure gravity flow |
Building & municipal rainwater and sewage drainage |
QT400-15 |
≥400 |
≥15 |
≤1.6MPa |
Complex geological & earthquake-resistant water transmission pipelines |
QT500-7 |
≥500 |
≥7 |
≤1.6MPa (K9) |
General municipal water supply & water conservancy engineering |
QT600-3 |
≥600 |
≥3 |
≥2.0MPa |
Deep-buried heavy-load & high-pressure industrial water transmission |
STSi Series |
≥100 |
Brittle material |
Low-pressure & non-impact |
Industrial strong corrosive medium transmission |
4.3 Anti-Corrosion Standard
External anti-corrosion: National standard zinc spraying ≥130g/㎡ + asphalt paint/epoxy resin coating; Inner lining: Non-toxic cement mortar lining with thickness above 3mm, anti-scaling and water corrosion-resistant, meeting drinking water safety standards. The buried service life is more than 50 years. All pipes are tested by hydraulic pressure holding test before delivery with no leakage and no cracks.
V. Production Process (Centrifugal Ductile Iron Pipe)
Iron water melting & heating (purification above 1450℃) → Spheroidization & inoculation treatment (special process for QT series) → High-speed centrifugal casting molding → Cooling & shaping → Pipe cutting, chamfering and interface finishing → Internal and external anti-corrosion spraying & lining curing → Hydraulic pressure test, metallographic inspection and dimension verification → Finished product storage and delivery.
VI. Core Product Advantages
Wide Performance Adaptability: Multiple materials and models cover non-pressure, low-pressure, medium-high pressure and strong corrosion working conditions for accurate type selection.
High Safety & Stability: Ductile iron material resists settlement, earthquake and rolling, with excellent interface tightness and zero leakage risk.
Ultra-Long Service Life: Buried service life exceeds 50 years, far longer than steel pipes and PVC pipes, with low later maintenance and comprehensive cost.
Efficient & Convenient Construction: Flexible interface requires no welding, greatly improving installation efficiency, suitable for various field and urban construction scenarios.
Green & Eco-Friendly: 100% recyclable material; cement mortar inner lining is non-toxic and harmless, complying with national drinking water transmission standards.
VII. Main Application Scenarios
Municipal Engineering: QT500-7 K9 grade ductile iron pipes for urban water supply main pipes, rainwater & sewage pipe networks and gas transmission pipelines.
Building Engineering: HT200 gray cast iron pipes for indoor and outdoor building drainage and auxiliary fire water supply systems.
Water Conservancy Engineering: QT400-15/QT500-7 pipes for reservoir water diversion, farmland irrigation, river-crossing inverted siphon and soft soil foundation pipelines.
Chemical & Industrial Engineering: QT600-3 high-pressure circulating water pipes and STSi series high silicon pipes for acid-base corrosive medium transmission.
Special Heavy-Load Scenarios: K10/K12 high-pressure ductile iron pipes for deep-buried road pipelines and factory heavy-load underground pipelines.
VIII. Installation & Maintenance Guidelines
Level the trench bottom and pave fine sand protective layer before pipe laying to prevent anti-corrosion layer scratch by hard objects; clean the interface, place the rubber ring in position and butt evenly with reserved deflection margin during flexible interface installation; backfill soil synchronously on both sides and compact in layers to avoid unilateral extrusion deformation; inspect interfaces regularly in daily use, repair damaged anti-corrosion layers in time, and prohibit long-term rolling of heavy vehicles on pipelines.
IX. Implementation Standards
National Standards: GB/T13295-2019 Ductile Iron Pipes, Fittings and Accessories for Water and Gas Pipelines, GB/T26081-2019 Ductile Iron Pipes, Fittings and Accessories for Sewage, GB/T9439 Gray Iron Castings, GB/T8491 High Silicon Corrosion-Resistant Iron Castings; International Standards: ISO2531, EN545, meeting the requirements of domestic engineering and foreign trade export.
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