Use Of Various 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 a large number of hard and brittle Fe3C, white cast iron is hard, brittle and difficult to process. Therefore, it is rarely used directly in industrial applications, and only used for a few parts that require wear resistance and are not impacted, such as wire drawing die, ball mill iron ball, etc. It is mostly used as billet for steel making and malleable cast iron.

Gray cast iron

Most or all of the carbon in cast iron exists as free flake graphite. The fracture is gray. It has good casting performance, good machinability, good abrasion resistance and good wear resistance. In addition, it has simple melting ingredients and low cost. It is widely used to manufacture castings and wear-resistant parts with complex structures.

According to different matrix structure, gray cast iron can be divided into three types: ferrite based gray cast iron, pearlite ferrite based gray cast iron and pearlite based gray cast iron.

Because there is 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 a large number of small notches on the steel matrix, which reduces the bearing area and increases the crack source. Therefore, the gray cast iron has low strength and poor toughness, and cannot be processed by pressure. In order to improve its performance, a certain amount of inoculants such as ferrosilicon and calcium silicon are added to the molten iron before casting to refine the pearlite matrix.

malleable iron

Malleable cast iron is a white cast iron blank made of iron carbon alloy with low carbon and silicon content. After a long time of high-temperature annealing treatment, the cementite decomposes into flocculent graphite, i.e. malleable iron is a kind of graphitized white cast iron.

Malleable cast iron can be divided into two types according to the microstructure after heat treatment; One is black core malleable iron and pearlescent malleable iron. The structure of black core malleable iron is mainly ferrite (f) basic + flocculent graphite; The structure of pearlite malleable cast iron is mainly pearlite (P) matrix + flocculent graphite. The other type is white core malleable cast iron. The structure of white core malleable cast iron depends on the section size. Ferrite is the matrix of small section, ferrite is the surface area of large section, pearlite and annealed carbon are the core.

Graphite becomes fine and evenly distributed. Cast iron after this inoculation treatment. It is called inoculated cast iron.

Ductile iron

A certain amount of spheroidizing agent (commonly used ferrosilicon, magnesium, etc.) is added before pouring molten iron (nodular cast iron) to spheroidize graphite in cast iron. Because carbon (graphite) exists in the cast iron matrix in the form of spheroids, the tensile strength, yield strength, plasticity and impact toughness of nodular cast iron are greatly improved by improving its splitting effect on the matrix. It has the advantages of wear resistance, shock absorption, good process performance and low cost. It has been widely substituted for malleable cast iron and some cast steel and forged steel parts, such as crankshaft, connecting rod, roller, automobile rear axle, etc.