The main differences between gray cast iron and ductile iron are reflected in material structure, physical properties and application scenarios.The specific differences are as follows:
1. Graphite morphology and internal structure
Gray cast iron: The internal graphite is distributed in flakes. This structure easily causes stress concentration, resulting in high brittleness and weak impact resistance of the material.
Ductile iron: By adding spheroidizers (such as magnesium, rare earth, etc.), the graphite is distributed in a spherical shape, which reduces the stress concentration effect and significantly improves the toughness and fatigue resistance of the material.
2. Physical properties comparison
Performance index Gray cast iron Ductile cast iron
Tensile strength Low (about 31K) High (about 60K), close to cast steel
Yield strength No clear yield point, direct fracture High (about 40K)
Ductility Poor, easy to brittle fracture Good, strong plasticity
Vibration absorption ability Excellent, suitable for shock absorption scenes Weak, but better than cast steel
3. Processing and appearance distinction
Cutting surface observation:
Gray cast iron: The cut surface is gray and rough, and the luster is dull.
Ductile cast iron: The cut surface has fine bright spots and large particles.
Filing test:
Gray cast iron: The filing resistance is small, the chips are gray and black and easy to stain fingers black.
Ductile cast iron: The filing resistance is slightly large, the chips are bright and the degree of blackening is light.
Knocking sound identification:
Gray cast iron: The sound is low and the duration is short.
Ductile iron: crisp sound with lingering sound.
Application scenarios
Gray cast iron:
Suitable for low-load, shock-absorbing parts, such as machine tool bases and internal combustion engine cylinder blocks.
Not suitable for high stress or impact environments (such as building structures and large containers).
Ductile iron:
Widely used in high-strength and corrosion-resistant scenarios, such as municipal pipelines, valves, and automobile crankshafts.
Because its corrosion resistance is better than cast steel, it is often used in sewage treatment plant gates and high-pressure water supply systems.
Cost and process
Gray cast iron: The production process is simple, the cost is low, and it is suitable for mass production.
Ductile iron: Nodularizers and more stringent heat treatment processes are required, the cost is higher, but the overall performance is better.
Of course, if you need a large number of custom ductile iron or gray cast iron parts, you can choose Mulan Metal. Mulan Metal has 12 years of casting experience, customers in more than 30 countries, and complete certificates, which can meet the customized casting needs of customers from different countries.
Here is our OEM cast iron parts Display：
