Cast iron is an iron-carbon alloy containing more than […]
Cast iron is an iron-carbon alloy containing more than 2.11% carbon. It is obtained by remelting cast pig iron (part of steel-making pig iron) in a furnace and adding ferroalloy, scrap steel, and remelted iron to adjust the composition. The difference with pig iron is that cast iron is secondary processed, and most are processed into cast iron parts. Cast iron parts have excellent castability and can be made into complex parts, and generally have good machinability. In addition, it has the characteristics of good abrasion resistance and shock absorption, and low price.
According to the different forms of carbon in cast iron, cast iron can usually be divided into white cast iron, gray cast iron and hemp cast iron.
1) White cast iron
The carbon in the white cast iron is all in the form of infiltrated carbon (Fe3C), because the fracture is bright white. It is called white cast iron. Due to the large amount of hard and brittle Fe3C, white cast iron has high hardness, 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 being impacted, such as wire drawing dies, ball mill iron balls, etc. Mostly used as billets for steelmaking and malleable cast iron.
2) Grey cast iron
Most or all of the carbon in cast iron exists as free flake graphite. The fracture is gray. It has good casting properties, good machinability, wear reduction, and good wear resistance. In addition, it has simple melting ingredients, low cost, and is widely used to manufacture complex structural castings and wear-resistant parts. Gray cast iron is divided into ferrite-based gray cast iron, pearlite-ferrite-based gray cast iron, and pearlite-based gray cast iron according to the matrix structure.
There is flake graphite in gray cast iron, and graphite is a component with low density, low strength, low hardness, and plasticity and toughness tending to zero. Its existence is like the existence of a large number of small gaps in the steel substrate, which reduces the bearing area and increases the source of cracks. Therefore, gray cast iron has low strength and poor toughness, and cannot be press-processed. In order to improve its performance, add ferrosilicon, silicon calcium and other inoculants to the molten iron before pouring to refine the pearlite matrix, and the graphite becomes small and uniformly distributed. This inoculated cast iron. Inoculated cast iron