Cast iron classification and properties

Generally, iron castings occupied more than 50% of weight of the machine equipments, so they are very important for the industry of one country.

The classifications of the cast iron

1. White cast iron

The carbon is on the surface of ferrites with small fraction and is in the form of Fe3c, the section of white cast iron is in sliver white color, its features is hard and fragile, it is difficult to be processed with machine and little used to produce parts. The main usage: it is used as the raw materials to make steel, also can be deal to malleable irons.

2. Gray cast iron

The carbon is on the surface of ferrites with small fraction and all is in the form of graphite, the section is in grey color. It is used widely actually, it occupies 80% of the cast iron. Their features are soft, fragile, poor intensity and small gravity. It includes common gray cast iron, malleable cast iron, ductile cast iron and vermicular graphite cast iron.

3. Mottled cast iron

It is belonged to the transition tissue between the white cast iron and gray cast iron. Because its property is not very good so it is used little.

4. Ductile Iron
Ductile iron is also called as spheroidal graphite cast iron or sg iron. Because of the nodular agent, the graphite form is shown as the spherodal, so this iron will have larger elongation and higher tensile and yield strength.

The factors which affect the micro-structure and property

1. The contents of carbon

When C=0.8%, it is pearlitic grey iron, the graphite piece is small and intensity is high, so it used to produce important parts. When C<0.8% they are pearlites and ferrite gray pig iron they have high hardness and the property is good, so it suits to the common machine parts.

2. The degree of graphitization

The chemical component of cast irons, the cooling speed of cast irons crystallizes, the superheating of iron water and quiescence in high temperature all affect the graphitization.

The development of cast iron

After China joining in WTO, the cast iron foundries meet great opportunities and challenges. China has great market potential in domestic and overseas. The advanced technology has a great effect on the traditional industries, the use of artificial intelligence and net technology can improve the control system guarantee the quality of the products.

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