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Laboratory work -7
Topic: Cast iron microstructure analysis.
The purpose of the work:
to study the microstructure
analysis of cast iron
Necessary tools and materials:
1. Metallographic microscope.
2. Cast iron samples with different composition.
3. Circle and ruler.
4. Atlas of microstructures of
metals and alloys
Theoretical information
Depending on the state of carbon in the cast iron, it is divided into white gray,
very fine, malleable cast iron.
White cast iron contains carbon in the form of cementite. Gray, very fine, malleable
cast iron contains a large part of the carbon rod in the free state, that is, in the form
of graphite.
White cast irons are divided into types according to their structure and carbon
content:
a) Pre-eutectic cast irons (2.14-4.3%S), their
structures consist of pearlite,
secondary cementite and ledeburite (Fig. 1, a).
b) Eutectic cast iron (4.3%S), its structure consists only of ledeburite (Fig. 1,
b).
c) Post-eutectic cast irons (4.3-6.67% S), their structures consist of primary
cementite and ledeburite (Fig. 1, c).
Gray cast irons are also called ductile irons because of their high moldability.
Gray cast iron is divided into the following types according to the structure of the
metal base: