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Structure Mechanical Properties Relationship In Steels

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Anoka Technical College

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MSE320 Lab 3 Fall 2020
Page 1 of 12
Structure-Mechanical Properties
Relationship in Steels
Amjad Alenzi
Abstract:
The main aim of this experiment is to investigate the association between heat treatment
process, microstructure and mechanical properties (hardness and toughness) of a medium
carbon steel. The carbon steel will undergo six routes of heat treatment that include furnace
cool, air cool, water quenching, water and tempered 150 °C, water and tempered 350 °C, and
water and tempered 550 °C. Izod impact test, Rockwell hardness test, and the sample
preparation for hardness test and microstructure analysis were conducted and the results were
recorded and analyzed in the proceeding sections of this report.
1. Introduction
The microstructural components in steel are referred to as pearlite, ferrite, martensite,
cementite, and austenite (Voort, 2010). Steel is a widely used metal and it s mostly used as a
structural material because it is cheap, readily available, has good quality operating
properties. The method of severe plastic deformation in steel has led to the development of
the unique properties of steel and has consequently led to the formation of nanocrystalline
and sub-micro structures in large semi-products (Kuziak et al., 1997). The properties of steel
that is subjected to severe plastic deformation at increased temperature develop under various
simultaneous processes that exert opposite force on its ductility and strength.
2. Experimental Work
2.1. Materials
An A36 or 4140 steel Izod/Charpy impact test specimen was used.
2.2. Procedure
There were six heat treatment routes that were used and each heat treatment samples were put
through the Izod impact test. Each tested sample was then sectioned, mounted, polished, and
etched for hardness and microstructure examinations. The specimens were put in the furnace
for an hour at 925 °C during the autenitizing procedure. The samples were then treated using
the six heat treatment techniques.
The samples were prepared for the microstructure analysis and hardness test by mounting
them in Bakelite and then ground, polished, and etched for microstructural evaluation.

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MSE320 Lab 3 Fall 2020
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3. Results and Discussion
The hardness of the samples was calibrated using the average of the three tests utilizing the
hardness test. The Hall-Petch equation illustrated below was used to determine the hardness
of the steel.


where d is the average grain diameter.
There generally are two types of impact tests: drop weight and pendulum. In this experiment,
the Izod impact test was performed which is a part of the pendulum test. The Izod test is a
strength test that determines the impact resistance of materials. It is almost similar to the
Charpy impact test with the exception that in the Izod test, the specimens are held in the
cantilevered beam configuration. Impact tests are used to determine a materials ability to
absorb energy during plastic deformation. Temperature influences the impact value of a
material. The lower the temperature, the lower the impact energy of a material.
Figure 1: Graph of Hardness vs Tempering Temperature
Material have varying behaviors when they are under different loads. The Vickers hardness
test is used in the determination of a material’s hardness in the micro-hardness, load range.
The Knoop test is used to test the hardness of thin layers of materials so that brittle materials
do not crack. The Rockwell hardness test is used to test the permanent depth of indentation
on a material when a load is place on it. The Brinell hardness test is primarily used to test the
hardness of the alloys of cooper and aluminum (low force) and the hardness of cast irons and
steel at higher forces than in copper and aluminum alloys. The Rockwell B scale is more
effective for the material used because we want to identify the permanent depth of
indentation that the indenter has on the material.
The indentations on a Rockwell test are spaced so that no new indentation is affected by a
previous indentation. Figure 1 is a graph of hardness vs the tempering temperature. The lower
the tempering temperature the higher the hardness value of a material.
84
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102
0 2 4 6 8 10 12 14 16
Hardness vs Tempering Temperature
Quenched + Tempered 150 °C Quenched + Tempered 350 °C
Quenched + Tempered 550 °C

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MSE320 Lab 3 Fall 2020 Structure-Mechanical Properties Relationship in Steels Amjad Alenzi Abstract: The main aim of this experiment is to investigate the association between heat treatment process, microstructure and mechanical properties (hardness and toughness) of a medium carbon steel. The carbon steel will undergo six routes of heat treatment that include furnace cool, air cool, water quenching, water and tempered 150 °C, water and tempered 350 °C, and water and tempered 550 °C. Izod impact test, Rockwell hardness test, and the sample preparation for hardness test and microstructure analysis were conducted and the results were recorded and analyzed in the proceeding sections of this report. 1. Introduction The microstructural components in steel are referred to as pearlite, ferrite, martensite, cementite, and austenite (Voort, 2010). Steel is a widely used metal and it s mostly used as a structural material because it is cheap, readily available, has good quality operating properties. The method of severe plastic deformation in steel has led to the development of the unique properties of steel and has consequently led to the formation of nanocrystalline and sub-micro structures in large semi-products (Kuziak et al., 1997). The properties of steel that is subjected to severe plastic deformation at increased temperature develop under various simultaneous processes that exert opposite force on its ductility and strength. 2. Experimental Work 2.1. Materials An A36 ...
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