(1) Gray cast iron, in which most or all of the carbon is present in the form of free state flake graphite, has a dark gray fracture surface, some mechanical properties, and good cutting performance, and is widely used in industry

(2) White cast iron White cast iron is a kind of iron carbon alloy with little or no graphite in its structure. Its fracture is white and bright, hard and brittle, and cannot be cut. It is rarely used directly in industry to make Machine element. Due to its high surface hardness, it is also known as chilled cast iron or chilled cast iron

(3) Hemp cast iron is a type of cast iron that is between white cast iron and gray cast iron. Its fracture surface is in the form of gray white alternating pits, which has poor performance and is rarely used

2. Classification by chemical composition

(1) Ordinary cast iron refers to cast iron with alloying elements, such as gray cast iron, malleable cast iron, ductile iron, etc

(2) Alloy cast iron is a type of cast iron prepared by adding some alloying elements to ordinary cast iron to improve certain properties. Such as various corrosion-resistant, heat-resistant, and high-performance cast iron,

3. Classification by production method and organizational performance

(1) Ordinary grey cast iron, see "Grey cast iron"

(2) Inoculated cast iron is made by using "modification treatment" on the basis of gray cast iron, also known as modified cast iron. Its strength, plasticity, and toughness are much better than ordinary gray cast iron, and its structure is also more uniform. Mainly used for manufacturing large castings with high mechanical performance requirements and significant changes in cross-sectional dimensions

(3) Malleable cast iron Malleable cast iron is made from white cast iron with a composition that has undergone graphite annealing and has higher toughness than gray cast iron, also known as ductile cast iron. It cannot be forged and is commonly used to manufacture castings that withstand impact loads

(4) Ductile iron is abbreviated as ductile iron. It is obtained by adding a certain amount of spheroidizing and graphitizing agents to the molten iron during casting to form spherical graphite crystals. Compared with steel, it has similar properties except for slightly lower plasticity and toughness. It is an excellent material that combines the advantages of steel and cast iron, and is widely used in mechanical engineering

(5) Performance cast iron is a type of cast iron with certain characteristics, which can be divided into cast iron, heat-resistant cast iron, corrosion-resistant cast iron, etc. according to different uses. Most of them belong to alloy cast iron and are widely used in mechanical manufacturing. The mechanical properties of cast iron castings are related to the microstructure of the matrix and the morphology of graphite. The flake graphite in gray cast iron severely cuts the matrix, causing stress concentration at the sharp corners of the graphite, making the tensile strength, plasticity, and toughness of gray cast iron much lower than that of steel. However, its compressive strength is equivalent to that of steel, and it is also a commonly used cast iron with poor mechanical properties. At the same time, the matrix structure also has an impact on the mechanical properties of gray cast iron. The graphite flakes of ferrite matrix gray cast iron are coarse, with low strength and hardness, so they are rarely used; The graphite flakes of pearlite based gray cast iron are small, with high strength and hardness, and are mainly used to manufacture more important castings; The graphite sheet of ferrite pearlite based gray cast iron is slightly thicker than that of pearlite gray cast iron, and its performance is not as good as that of pearlite gray cast iron, casting box, and cast iron heat resistant plate. Therefore, gray cast iron with a pearlite matrix is commonly used in industry.