Cast iron is mainly divided into white cast iron, gray cast iron, malleable cast iron and ductile iron. The following are the uses of various cast irons. Let's explore it together!

Various uses of cast iron

✔️White cast iron

All carbon in white cast iron exists in the form of infiltrated carbon body (Fe3c), because the fracture is bright white. Therefore, it is called white cast iron. Due to the large amount of hard and brittle Fe3c, white cast iron has high hardness, high brittleness and is difficult to process. Therefore, it is rarely used directly in industrial applications, and is only used for a few parts that require wear resistance without impact, such as wire drawing dies, ball mill iron balls, etc. Mostly used as a billet for steelmaking and malleable cast iron.

✔️Grey cast iron

Most or all of the carbon in cast iron exists as free-state flake graphite. The fracture is grey. It has good casting performance, good machinability, wear reduction and wear resistance, plus it has simple melting ingredients and low cost, and is widely used in the manufacture of complex structural castings and wear-resistant parts.

Gray cast iron is divided into three categories according to the different matrix structure: ferrite-based gray cast iron, pearlite-ferrite-based gray cast iron and pearlite-based gray cast iron.

Due to the presence of flake graphite in gray cast iron, graphite is a component with low density, low strength, low hardness, and zero plasticity and toughness. Its existence is like the existence of a large number of small gaps in the steel matrix, which reduces the bearing area and increases the crack source, so the gray cast iron has low strength and poor toughness, and cannot be processed under pressure. In order to improve its performance, a small amount of inoculants such as ferrosilicon and silicon calcium are added to the molten iron before casting to refine the pearlite matrix.

✔️Malleable cast iron

Malleable cast iron is made of iron-carbon alloys with low carbon and silicon content into white cast iron blanks, and then after long-term high-temperature annealing treatment, the cementite is decomposed into flocculent graphite. Treated white cast iron.

Malleable iron is divided into two categories according to the different microstructure after heat treatment; one is black-heart malleable iron and pearlescent malleable iron. The black-heart malleable iron structure is mainly ferrite (F) + flocculent graphite; the pearlitic malleable iron structure is mainly pearlite (P) matrix + flocculent graphite. The other type is white-heart malleable cast iron. The structure of white-heart malleable cast iron is determined by the size of the section. The small section is based on ferrite, the surface area of ​​the large section is ferrite, and the core is pearlite and annealed carbon.

Graphite becomes fine and evenly distributed, cast iron after this inoculation treatment. Called inoculated cast iron.

✔️Ductile Iron

Add a certain amount of nodularizing agent (commonly used ferrosilicon, magnesium, etc.) before the molten iron (ductile pig iron) is poured to spheroidize the graphite in the cast iron. Since carbon (graphite) exists in the cast iron matrix in a spherical shape, improving its splitting effect on the matrix, the tensile strength, yield strength, plasticity and impact toughness of ductile iron are greatly improved. It has the advantages of wear resistance, shock absorption, good process performance and low cost. It has now widely replaced malleable cast iron and some cast steel and forged steel parts, such as crankshafts, connecting rods, rollers, and rear axles of automobiles.

Conclusion

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