Malleable cast iron pipe fittings (Malleable Iron fittings) and ductile cast iron grooved pipe fittings are two common types of cast iron pipe fittings. They differ significantly in materials, manufacturing processes, performance, and applications. Below is a detailed comparison:
1. Malleable Cast Iron Pipe Fittings (Malleable Iron Fittings)
Material & Manufacturing Process
- Material: White cast iron (low carbon, low silicon).
- Process: High-temperature annealing (malleableization) converts brittle cementite in white cast iron into flake-like graphite, improving toughness and machinability.
- Forming: Casting followed by complex heat treatment.
Performance
- Good toughness: Resists impact, suitable for small, complex-shaped fittings.
- Moderate strength: Tensile strength ~300–400 MPa (lower than ductile iron).
- Pressure resistance: Suitable for low-to-medium pressure systems (≤1.6 MPa).
- Corrosion resistance: Requires galvanizing or coatings.
Connection Method
- Threaded connections: Used in gas, plumbing, and fire sprinkler systems.
Applications
- Low-pressure systems: Building water supply, gas pipelines, small valves, elbows, and tees.
2. Ductile Cast Iron Grooved Pipe Fittings
Material & Manufacturing Process
- Material: Ductile iron (magnesium/rare earth additives create spherical graphite).
- Process: Direct casting without complex heat treatment.
Performance
- High strength: Tensile strength 500–800 MPa (close to steel).
- High toughness: Combines cast iron corrosion resistance with steel-like flexibility.
- Pressure resistance: Suitable for medium-to-high pressure systems (≥2.5 MPa).
- Corrosion resistance: Better than standard cast iron (often epoxy-coated).
Connection Method
- Grooved connections: Use clamps and rubber seals for fast installation.
Applications
- High-pressure systems: Municipal water supply, industrial pipelines, large-diameter fire mains.
Key Differences
| | Aspect | Malleable Iron Fitting | Ductile Iron Grooved Fittings |
| | Graphite Form | Flake-like | Spherical |
| | Strength | 300–400 MPa | 500–800 MPa |
| | Pressure | ≤1.6 MPa | ≥2.5 MPa |
| | Connection | Threaded | Grooved clamps/flanges |
| | Size Range | DN15–DN100 | DN80–DN2000 |
What are the types, standard classifications, and pros/cons of Malleable Iron pipe fittings and grooved pipe fittings?
1. Malleable Iron Pipe Fittings
Types：Threaded fittings: Elbows (90°/45°), tees, reducers, couplings, caps. Functional fittings: Valves, locknuts.
Standards
- China: GB/T 3287-2011, GB/T 3289.x series.
- International: ASTM A197 (U.S.), EN 10242 (Europe), JIS B2301 (Japan).
Pros & Cons
- Pros: Low cost, easy threaded installation, good for low-pressure systems.
- Cons: Limited strength, corrosion-prone, small size range (DN15–DN100).
2. Ductile Iron Grooved Pipe Fittings
Types：Grooved fittings: Elbows, tees, reducers, mechanical couplings. Flanged fittings: Blind flanges, valve adapters.
Standards
- China: GB/T 13295-2019, CJ/T 156-2001.
- International: ISO 2531, EN 545, AWWA C110 (U.S.).
Pros & Cons
- Pros: High strength/pressure resistance, quick grooved installation, large sizes (DN80–DN2000).
- Cons: Higher cost, heavy weight, requires groove-cutting tools.
Comparison Summary
| Aspect | Malleable Iron Fittings | Ductile Iron Grooved Fittings |
| | Application | Low-pressure,small, frequent maintenance | High-pressure, large-scale projects |
| | Cost | Low | High |
| | Installation | Simple (threaded) | Requires grooving tools/clamps |