Effect of Pre-Strain on Micro-Structural Behavior and Mechanical Properties of a Medium Carbon Steel
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Date
2023-07
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G. B. Pant University of Agriculture & Technology, Pantnagar-263145
Abstract
The aim of this experimental work was to investigate the “Effect of Pre-Strain on
Micro-Structural Behavior and Mechanical Properties of a Medium Carbon Steel”. The
specimens were austenized for soaking time of 4 hours at temperatures 1100°C and 900°C,
then quenched in water. Specimens are subjected pre-strain value 0%, 4%, 7% and 10% of
elongation for tensile test before tempering. Then specimens were tempered at temperatures
500°C and 300°C for soaking time 2 hours and cooled in air. After cooling tensile test and
hardness test were performed. Tempering and cooling rate have been proven to affect and
improve the micro-structure and mechanical properties of medium carbon steel (MCS). Thus,
tempering is employed to get desirable qualities of MCS such as increased toughness,
ductility or removal of residual stresses. The changes in mechanical behavior as compared
with untreated specimens are explained in terms of changes in UTS, Yield strength, hardness,
elongation, ASTM number and grain size. Results show that the mechanical Characteristics
can be changed and improved by tempering for a particular application. It was also found that
the Yield strength and UTS decreases as grain size increases with increase in deformation.
UTS and hardness increases by increasing pre-strain value while deformation decreases.
Hardness of specimen increased after quenching. To reduce this hardness tempering process
was applied and specimen became tougher. With the increase in grain size the percentage
elongation also increase. MCS changes from ferrite and pearlite structure to austenite
structure when heated over critical temperature. Sudden quenching in water changes its
structure austenite to martensite structure. Also the structure of steel is changed by tempering.
Some of the extra carbon atoms that were bound in the crystal lattice during quenching have
been released during tempering. As a result, tiny, finely scattered carbide particles precipitate
within the steel matrix. These carbides prevent dislocations from moving, increasing the
steel's strength and hardness.
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Theses of M. Tech