Hardness; the Brinell hardness shall not exceed 230 HB for pipes and 250 HB for fittings and accessories.
The below stated materials characteristics must be tested and inspected in the process control system when pipes, fittings and accessories are being manufactured, and must reserve these process demonstrated samples and verifiable process records.
Mechanical Properties
 Testing for Ductile Iron Pipe |
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| Nominal diameter mm | Tensile strength N/㎡ | Yield strength N/㎡ | Elongation% | Hardness HB | Water Pressure test MPa | Air-tight test MPa |
| ≤300 | ≥420 | ≥300 | ≥10 | ≤230 | 5 | ≥0.6 Mpa |
| 300—600 | ≥420 | ≥300 | ≥10 | ≤230 | 4 | ≥0.6 Mpa |
| 700—1000 | ≥420 | ≥300 | ≥10 | ≤230 | 3.2 | ≥0.1 Mpa |
| 1200 | ≥420 | ≥300 | ≥7 | ≤230 | 2.5 | ≥0.1 Mpa |
The above-stated materials characteristics must be tested and inspected in the process control system when pipes, fittings and accessories are being manufactured, and must reserve these process demonstrated samples and verifiable process records.
Ductile cast iron has excellent resistance to impacts and shocks than grey cast iron due to its spheroidal graphite microstructure.
Ductile cast iron possesses about two times greater tensile strength than grey cast iron, and also has considerable degree of ductility together since its metal matrix is ferrite as a result of heat treatment.
The chemical structure of ductile cast iron are same as grey cast iron, ductile cast iron has anti-corrosive properties of cast iron products and strength similar to carbon steel.
Microscopic Photos for Ductile Iron and Gray Iron
By the microscopic photos as above Magnification show the differences in structure between ductile cast iron and grey cast iron.
Under the microscope, the structure is mainly composed of metal matrix and graphite.
In the grey cast iron, the graphite is spread in flake shape, thus being liable to brittle.
In the ductile cast iron, the graphite is spread in spherical shape, thus giving desirable strength.
The ductile cast iron pipes have high bursting resistance against internal pressure and ductile iron pipe has excellent resistance to water hammer.
The ductile cast iron has high corrosion resistance properties and longer service life than grey cast iron.
When installing pipe, the machinability and workability are excellent to cast iron pipes.
