EN8 is a very popular grade of through-hardening medium carbon steel, which is readily machined able in any condition. EN8 is suitable for the manufacture of parts such as general-purpose axles and shafts, gears, bolts and studs
Presentation on Carburizing (Heat Treatment Process).
Presented To,
Engr. Ubaid-ur-Rehman Ghouri, Department of Industrial & Manufacturing Engineering, UET Lahore (RCET Campus).
Presented By,
Muhammad Zeeshan
Zahid Mehmood
Ali Iqbal
Muhammad Waqas
Carburzing and Different Types of CarburzingMelwin Dmello
This Presentation covers the Basic concepts of Carburzing and Different Types of Carburzing in a easy version. For more information, please refer the books mentioned in the references slide.... Thank you
Presentation on Carburizing (Heat Treatment Process).
Presented To,
Engr. Ubaid-ur-Rehman Ghouri, Department of Industrial & Manufacturing Engineering, UET Lahore (RCET Campus).
Presented By,
Muhammad Zeeshan
Zahid Mehmood
Ali Iqbal
Muhammad Waqas
Carburzing and Different Types of CarburzingMelwin Dmello
This Presentation covers the Basic concepts of Carburzing and Different Types of Carburzing in a easy version. For more information, please refer the books mentioned in the references slide.... Thank you
Heat treatment defects &and its remediesNIAJ AHMED
Heat Treatment involves various heating and cooling procedures performed to effect structural changes in a material, which turn affect its mechanical properties
PRODUCTION TECHNOLOGY
The selection of a foundry furnace depends upon the following factors:
Initial cost of the furnace
Fuel cost
Kind of metal or alloy to be melted
Melting and pouring temperature of the metal to be cast
Quantity of metal to be melted
Cost of furnace repair and maintenance
Cost of melting per unit weight of the metal
Chances of metal to absorb impurities during melting
Quantity of the finished product desired
CUPOLA FURNACE
INDUCTION FURNACE
TYPES OF FURNACES
Explosive Forming is a manufacturing technique that uses explosions to force metal into dies and molds.
The explosives are typically either detonated underwater or in direct contact with the materials.
The technique is useful for short production runs of conventionally difficult-to-manufacture parts.
In Explosive Forming a punch or diaphragm in conventional forming is replaced by an explosive charge.
Chemical energy from the explosives is used to generate shockwaves through a medium (mostly water), which are directed to deform the workpiece at very high velocities.
Comparison of Mechanical Properties of Austempered, Normalized and As-Weld Ca...IJAEMSJORNAL
More often than not, welded joints experience failure such as fracture which jeopardize their reliability and ergonomics when put in perspective. Attempting a significant improvement in the mechanical properties of welded joint through heat treatment could ensure joints stability and reduce the costs associated with constant repairs and replacements. In this study, the effects of heat treatments (austempering and normalization) on the mechanical properties of weldments were examined. The locally recycled steel sample was sourced from the Delta Steel Company Aladja, Delta State and the spectro-analysis was carried out on it. The test samples were machined as per properties for tests, fractured locally and were welded using shielded metal arc welding (SMAW) with stainless steel electrode. They were then heat treated in electric furnaces. The mechanical properties (tensile strength, yield strength, hardness and impact toughness) were determined and the microstructure examined using scanning electron microscope. They were also examined physically using hand lens. The result indicated that the austempered samples improved significantly in terms of its tensile strength, yield strength, hardness and ductility. It was also found that the untreated sample produced the greatest impact toughness. The result of the physical examination also suggested that heat treatment using oil based quenchant have the potential to inhibit rust at weld joints.
Heat treatment defects &and its remediesNIAJ AHMED
Heat Treatment involves various heating and cooling procedures performed to effect structural changes in a material, which turn affect its mechanical properties
PRODUCTION TECHNOLOGY
The selection of a foundry furnace depends upon the following factors:
Initial cost of the furnace
Fuel cost
Kind of metal or alloy to be melted
Melting and pouring temperature of the metal to be cast
Quantity of metal to be melted
Cost of furnace repair and maintenance
Cost of melting per unit weight of the metal
Chances of metal to absorb impurities during melting
Quantity of the finished product desired
CUPOLA FURNACE
INDUCTION FURNACE
TYPES OF FURNACES
Explosive Forming is a manufacturing technique that uses explosions to force metal into dies and molds.
The explosives are typically either detonated underwater or in direct contact with the materials.
The technique is useful for short production runs of conventionally difficult-to-manufacture parts.
In Explosive Forming a punch or diaphragm in conventional forming is replaced by an explosive charge.
Chemical energy from the explosives is used to generate shockwaves through a medium (mostly water), which are directed to deform the workpiece at very high velocities.
Comparison of Mechanical Properties of Austempered, Normalized and As-Weld Ca...IJAEMSJORNAL
More often than not, welded joints experience failure such as fracture which jeopardize their reliability and ergonomics when put in perspective. Attempting a significant improvement in the mechanical properties of welded joint through heat treatment could ensure joints stability and reduce the costs associated with constant repairs and replacements. In this study, the effects of heat treatments (austempering and normalization) on the mechanical properties of weldments were examined. The locally recycled steel sample was sourced from the Delta Steel Company Aladja, Delta State and the spectro-analysis was carried out on it. The test samples were machined as per properties for tests, fractured locally and were welded using shielded metal arc welding (SMAW) with stainless steel electrode. They were then heat treated in electric furnaces. The mechanical properties (tensile strength, yield strength, hardness and impact toughness) were determined and the microstructure examined using scanning electron microscope. They were also examined physically using hand lens. The result indicated that the austempered samples improved significantly in terms of its tensile strength, yield strength, hardness and ductility. It was also found that the untreated sample produced the greatest impact toughness. The result of the physical examination also suggested that heat treatment using oil based quenchant have the potential to inhibit rust at weld joints.
Effect of Heat Treatment on Corrosion Behavior of Spring SteelsEditor IJCATR
The experimental work deals with the effect of heat treatment on the corrosion behaviour of spring steels. In this study the
heat treatments like hardening, normalizing and tempering were done for spring steels to obtain martensitic matrix, pearlitic structure
and tempered martensitic matrix respectively. After heat treatment the microstructural studies were carried out for the samples using
SEM. Hardness measurements were done. The corrosion behaviour of all heat treated samples in HCl at different concentration (1.5N,
2N and 2.5N) was determined using Tafel extrapolation technique. The variation in the corrosion rates due to the effect of heat
treatment was noted. The results indicate that for fully martensitic matrix the corrosion rate is minimum and for pearlitic structure its
maximum. As tempering time is increased the corrosion rate increases correspondingly. The corroded microstructural images were
also taken using SEM and analysed.
Effect of Subzero Treatment on Microstructure and Material Properties of EN...IJMER
Cryogenic treatment of steels has been widely used for enhancing mechanical properties
like hardness, toughness and stable metallurgical structure. Application such as gears, kicker rods,
bolts are made of medium carbon alloy steels like EN-24 steel. In these applications, percentage of
retained austenite has considerable effects on the life of the material. A comparative study on
conventionally heat-treated (CHT) and shallow cryogenic treated (SCT) EN-24 steel was done to
evaluate the effect of shallow cryogenic treatment (SCT) on hardness, toughness and the amount of
retained austenite present in the structure of EN24 steel. The microscopic structure of cryogenic
treated EN24 steel revealed the formation of carbides, both primary and secondary carbides. An
estimated amount of 15% retained austenite after CHT tempered condition was less than 2% after SCT
tempered condition. Tensile test fractography of subzero treated (SCT) specimen revealed ductile
fracture. The maximum hardness observed in case of SCT tempered samples was 415BHN, 15%
increase from CHT tempered samples. The maximum impact strength observed in case of SCT
tempered samples was 240kJ/m2, 11% increase from CHT tempered samples. Further SCT tempered
samples, tempered at 650°C resulted in ductility increase by 55% as compared to CHT tempered
samples without sacrificing hardness.
Influence of Heat Treatment on Mechanical Properties of Aisi1040 SteelIOSR Journals
This investigation is concerned to evaluate the influence of heat treatment on mechanical behavior of AISI1040 steel; it is one of the grades of medium carbon steel of American standard containing 0.40% carbon in its composition. Specimen of quenched/hardened AISI1040 steel was tempered at temperature (650,450&250℃) for 60, 90&120 minutes to modify desired properties. The mechanical behavior, particularly, ultimate tensile strength, yield strength and elongation were investigated using universal testing machine; while the hardness measurement was done on Rockwell hardness testing machine of heat treated specimens. Result shows that the ultimate tensile strength and the yield strength decrease while the elongation increases with an increase in tempering temperature and tempering time of different tempered specimen. The hardness of quenched/hardened specimen decreases with an increase in tempering temperature and tempering time. Furthermore, increasing temperature and lowering time produces approximately same result as decreasing temperature and increasing time.
Study and Analysis on Heat Treatment Process and Microstructure of Low Carbon...IJARTES
Low carbon steel is easily available and cheap
having all material properties that are acceptable for many
applications. Heat treatment on low carbon steel is to improve
ductility, to improve toughness, strength, hardness and tensile
strength and to relive internal stress developed in the material.
Here basically the experiment of harness and ultimate tensile
strength is done to get idea about heat treated low carbon steel,
which has extensive uses in all industrial and scientific fields
Effect of Subzero Treatment on Microstructure and Material Properties of EN24...IJMER
Cryogenic treatment of steels has been widely used for enhancing mechanical properties
like hardness, toughness and stable metallurgical structure. Application such as gears, kicker rods,
bolts are made of medium carbon alloy steels like EN-24 steel. In these applications, percentage of
retained austenite has considerable effects on the life of the material. A comparative study on
conventionally heat-treated (CHT) and shallow cryogenic treated (SCT) EN-24 steel was done to
evaluate the effect of shallow cryogenic treatment (SCT) on hardness, toughness and the amount of
retained austenite present in the structure of EN24 steel. The microscopic structure of cryogenic
treated EN24 steel revealed the formation of carbides, both primary and secondary carbides. An
estimated amount of 15% retained austenite after CHT tempered condition was less than 2% after SCT
tempered condition. Tensile test fractography of subzero treated (SCT) specimen revealed ductile
fracture. The maximum hardness observed in case of SCT tempered samples was 415BHN, 15%
increase from CHT tempered samples. The maximum impact strength observed in case of SCT
tempered samples was 240kJ/m2, 11% increase from CHT tempered samples. Further SCT tempered
samples, tempered at 650°C resulted in ductility increase by 55% as compared to CHT tempered
samples without sacrificing hardness
Effect of Hardness and Wear Resistance on En 353 Steel by Heat Treatment IJMER
En 353 steel is an easily available and cheap material that is acceptable for heavy duty
applications. Heat treatment on En 353 steel is improved the ductility, toughness, strength, hardness and
relive internal stress in the material. Spectrographic method is used to analyze the composition of the
alloy material. The experimental results of hardness and dry wear testing on pin-on-disc are done to get
idea about heat treated En 353 steel. It is found that the hardness and wear resistance of the En 353 steel
is improved after the heat treatment and the microstructure is changed from ferrite to martensite.
Study on Influence of heat treatment on Tribological properties of mild steeldbpublications
A study was made on the effect of heat treatment upon the mild steel. Total six samples were prepared for each test (hardness test, tensile test, microstructure test and wear test) from those two was tested as received and rest four were subjected to different heat treatment that are annealing and normalizing (heated on a temperature of 850 degree Celsius). The hardness of all sample was measured by Rockwell hardness testing machine. Wear measurement was done on pin-on disc wear machine. Tensometer was used to find out the ultimate stress and strain of the sample. The result of tensile test showed that the strength is decreased by heat treating and the surface hardness is also decreased by heat treatment. Microstructure of the mild steel specimens shows the grain boundary of the particles and the content of % of carbon present. It justifies the experimental results of tensile test and hardness test. Surface Hardness is the measure of resistance that any material applies. As the specimen gets soft on treating the hardness also gets decreased. Tensile strength of any specimen is specified as how much stress the material can withstand before breaking. As the metal gets soft after heat treatment the load required for breaking goes on decreasing. Wear test is carried out to see the variation in wear measurement and coefficient of friction as the mesh size of paper are varied. More soft the surface of material is more wear is seen and vice-versa.
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Pile Foundation by Venkatesh Taduvai (Sub Geotechnical Engineering II)-conver...
STUDY OF MICRO STRUCTURE OF HEAT TREADTED EN8 STEEL
1. Sakib Ali
Saqueeb Ali
Anis Haider
Md Javed Raja Ansari
Muddasir Ali Mondal
Sourav Kumar Mahato
130207075
130207079
140307132
140307136
140307137
140307145
2. 1. Abstract
2. Introduction
3. Objective
4. Introduction To En-8 Steel
5. Properties Of En-8 Steel
6. Heat Treatment Process
7. Universal Testing Machine
8. Sample Preparation
9. Optical Microscope
10.Comparison Of Microstructures
11.Inference
12.Reference
3. Steels are generally heat treated in order to achieve desired changes in
their microstructure and mechanical properties. The effect of heat
treatment cycle on the microstructure and some mechanical properties of
EN8 steel have been studied and presented in this presentation. The
heat treatment cycles given are Annealing, normalizing, hardening and
tempering are the most important heat treatments often used to modify
the microstructure and mechanical properties of engineering materials
particularly steels.
Sample of steel is purchased and various specimens are prepared for
tests of mechanical properties, the changes in properties are examined
and studied. Finally the heat treated sample was examined in the
microscope. In the specimen, grains were differentiated and impurity
particle could be seen clearly. The microstructure of the specimen was
snapped on 100X, 200X, 500X, and 1000X. Then, analysis and
comparison of the microstructure is done.
4. Heat treatment and microstructure studies have always been
a wide area of research for mechanical engineers
We come across steel in our life on an everyday basis. We
can find its influence in our life in almost everything we do,
we use or we look at. The steel used for this research
however is a medium carbon EN-8 steel AISI 1040. It is
alloyed and it is used to make things like shafts, keys,
stressed pins. The steel with its immense practical
applications are an important component in everybody's life.
EN8 is a very popular grade of through-hardening medium
carbon steel, which is readily machined able in any
condition. EN8 is suitable for the manufacture of parts such
as general-purpose axles and shafts, gears, bolts and studs.
5. To treat the En 8 steel in quenching annealing and normalizing.
To treat the En 8 steel in single tempering after quenching annealing
and normalizing .
To measured tensile strength by universal testing machine (UTM) .
To compare the hardness of En8 steel after quenching annealing and
normalizing.
To compare the micro-structure of the specimen after different heat
treatment process.
6. EN8 is an alloyed medium carbon steel grade with
reasonable tensile strength. It is normally supplied in the cold drawn or
as rolled condition. Tensile properties can vary but are usually
between 500-800 N/mm². EN8 is widely used for applications which
require better properties than mild steel but does not justify the costs of
an alloy steel. EN8 can be flame or induction hardened to produce a
good surface hardness with moderate wear resistance.
7. EN8 carbon steel is a common medium carbon and medium tensile steel, with
improved strength over mild steel, through-hardening medium carbon steel.
Readily machinable in any condition.
It can be further surface-hardened by induction processes, producing
components with enhanced wear resistance.
In its heat treated forms possesses good homogenous metallurgical structures,
giving consistent machining properties
Suitable for the manufacture of parts such as general-purpose axles and shafts,
gears, bolts and studs.
Good heat treatment results on sections be achievable.
8. Max Stress 700-850N/mm^2
Yield stress 465N/mm^2 min
Max Elongation 16% min
Impact KCV 28 Joules min
Hardness 201-255 Brinell
MECHANICAL PROPERTIES
10. The sample was received as a round bar. Later on it was cut to desired
specified measurement as per our requirement. Later the specimens
were undergone through various heat treatment processes.
Heat treatment is a combination of timed heating and cooling
applied to a particular metal or alloy in the solid state in such
ways as to produce certain microstructure and desired
mechanical properties. The heat treatment of steel was done at
different temperatures of 950OC, 975OC, 1000OC, 1025OC by
using muffle furnace. At each temperature 6 samples were kept to
be heated.
11. A furnace is a device used for high-
temperature heating.
A furnace used for many things, such
as the extraction of metal from ore or
in oil refineries and other chemical
plants.
The heat energy to fuel a furnace may
be supplied directly by
fuel combustion, by electricity such as
the electric arc furnace, or
through induction heating in induction
furnaces.
It serves as a reactor to provide heats to
the reaction. The design of the furnaces
varies, however the basic features are
most common among all of them.
12. Specimen of EN-8 steel rod was first preheated at 15OC per minute to 950OC
in a furnace and then held there for 30 minutes such that the temperature
homogeneity occurs at all section of the specimens for austentization. After
holding for 30 minutes, switch off the furnace and open the furnace door to
allow the samples to cool inside the furnace until red heat is gone. Take out the
samples and air cool to 65OC in air take out the samples which are at the
austenitizing temperature, submerge in oil bath, and water quenched to the
room temperature.
13. To remove any preexisting anomalies of material properties, the sample were
first subject to a careful annealing cycle: preheating to 950OC, hold for 15
min. slow (stepwise) heating to 950OC; 200-400-600-800-950OC; hold for 15
min at each step. Holding for ½ hrs at 950OC, slow cooling and switch off
furnace. Leave samples inside until cooled to 480OC. brisk cooling open
furnace door, cool to room temperature.
14. Normalizing process for steels is defined as heating the steel to
austenite phase and cooling it in the air. It is carried out by
heating the steel approximately 500C above the upper critical
temperature followed by cooling in air to room temperature, or at
no greater than 1 bar pressure using nitrogen if the process is
being run in a vacuum furnace. Normalizing temperatures usually
vary from 8100c to 9300C.
15. Temper the EN8 component immediately after quenching whilst tools are still
hand warm. Re-heat the EN8 component to the tempering temperature then
soak for one hour per 25 millimeter of total thickness (2 hours minimum) Cool
in air. For most applications tempering of EN8 will be between 550-660°C.
16. Sl.
No.
Heat Treated Sample Force (KN)
1.
Quenching
(Without Tempering) 251
2.
Annealing
(Without Tempering) 152
3.
Normalizing
(Without Tempering) 168
4.
Quenching
(With Tempering) 207
5.
Annealing
(With Tempering) 118
6.
Normalizing
(With Tempering) 165
Heat treated samples were
tested for various mechanical
properties. Average HRC
readings were determined by
taking several readings at
different positions on the
samples, using Rockwell
hardness tester. For tensile
properties, standard tensile
specimens were loaded into
400-KN Universal Testing
Machine hooked up to a data
logger.
17. A machine used to test specimens for tensile strength,
compressive strength, shear strength and to perform bend test
along other important laboratory tests. The primary use of the
testing machine is to create the stress strain diagram.
Once the diagram is generated, a pencil and straight edge or
computer algorithm can be
used to calculate
yield strength,
Young's Modulus,
tensile strength
or total elongation.
18. Tool Steel
Material
Sample Mark Rockwell
Hardness
C-HRC
Rockwell
Hardness
B-HRB
Brinell
Hardness
HB
EN-8
Annealing
12 91 187
Annealing with
Tempering
1 82 155
Quenching
42 113 392
Quenching
with Tempering
63 - 685
Normalizing
47 115 446
Normalizing
with Tempering
22 99 234
Hardness of EN-8 Steel was determined using Brinell and Rockwell
19. Proper preparation of metallographic specimens to determine
microstructure and content requires that a rigid step-by-step process
be followed. In sequence, the steps included cutting, mounting,
course grinding, fine grinding, polishing, etching and microscopic
examination. Specimens must be kept clean and preparation
procedure carefully followed in order to reveal accurate
microstructures.
This operation was performed using a power hacksaw. this process is involve
cutting a small piece of the work piece by a tool consisting of a series of
narrowly spaced teeth, called a saw blade. Sawing is used to separate work
parts into two or more pieces, or to cut off an unwanted section of a part.
20. Grinding is the most common form of abrasive machining. It is a material cutting
process which engages an abrasive tool whose cutting elements are grains of
abrasive material known as grit. These grits are characterized by sharp cutting
points, high hot hardness, chemical stability and wear resistance. The grits are
held together by a suitable bonding material to give shape of an abrasive tool.
Metal Polishing sometimes known as Finishing or Buffing is the process of
removing scratches and abrasions from a surface, and creating the desired
brightness of finish on that surface. Polishing, like using sand paper, consists of
procedures each of which is less abrasive than the previous. A combination of
polishing buffing wheels and compounds are used with a buffing machine or a
household electric drill (pneumatic tools may also be used but only at relatively
low speeds of 4000 rpm max.)
21. The specimen was placed on the table under the fume hood with the polished
surface up.
1. The surface was cleaned with alcohol and let dried.
2. A few drops of nital solution (2%) were applied to the specimen surface
covering the entire metallic surface of the specimen using the eye dropper.
3. After 20 to 30 seconds. The etchant was rinsed into the sink with the water and
it is quickly rinsed with alcohol.
4. The sample was dried again.
The sample was examined in the optical microscope. In the specimen, grains were
differentiated and impurity particles could be seen clearly.
Metallurgical microscope was used to view the specimen at various magnifications
and the microstructural aspect of the material was noted.
The microstructure of the specimen was snapped on 100X, 200X, 500X, 1000X
zooming lenses.
22. The optical microscope, often referred to as light
microscope, is a type of microscope which
uses visible light and a system of lenses to
magnify images of small samples.
The image from an optical microscope can be
captured by normal light-sensitive cameras to
generate a micrograph.
Compound optical microscopes are typically used
to examine a smear, a squash preparation, or a
thinly sectioned slice of some material.
A common use of non-transmitted lighting is to
study the thin structure of metals and minerals,
where the light is reflected from the examined
surface.
It can produce a magnified image of a specimen
up to 1000X and, at high magnifications, are used
to study thin specimens as they have a very
limited depth of field.
23. The figure depicts microstructure of ‘As received material’ (which is
EN-8 steel prior to heat treatment) at 200X zoom, from our objective
point of view we consider this microstructure as our reference for
further analysis. We can observe from this microstructure the pearlite
and ferrite structure clearly. We can also observe non uniformity of
the grain size and its coarse nature, the ferrite and pearlite
microstructure are also non uniform. The material does not possess
good wear resistance.
24. The quenched specimens would have their austenites transformed to
martensites. These are fine, needle-like structures which are very strong and
hard, but very brittle. The transformation of austenite to martensite by a
diffusion less shear type transformation in quenching is also responsible for
higher hardness obtained and this property is attributed to the effectiveness of
the interstitial carbon in hindering the dislocation motion. After the hardened
steel tempered the prevalent martensite is an unstable structure and the carbon
atoms diffuse from martensite to form a carbide precipitate and the concurrent
formation of ferrite and cementite.
Fig. Quenching with tempering Fig. Quenching without tempering
25. If we now observed the microstructure of normalized with tempering steel we can
see the coarse grains are produced. The grain size diameter is increased.
Because of tempering the heating temp is low and cooling rate is low so nuclei
formation will be less. The grain boundary is less than the normalized steel, void
also decreases. It increases the dislocation movement because of this ductility of
the material will also increase.
Fig. Normalizing (200X) Fig. Normalizing with
tempering (200X)
26. If we observe the microstructure of annealing with that of annealing along with
tempering we can see the fine grains are transformed into coarsened grains due
to which void is decreased. The grain size diameter is increased .Because in
tempering the heating temp.is low and cooling rate is low so nuclei formation will
be less. The grain boundary is less than the annealed steel. As a result of
tempering the martensite gets transformed into tempered martensite and thus as
a result hardness of the sample decreases.
Fig. Annealing (200X) Fig. Annealing With
Tempering (200X)
27. The following conclusion has been drawn from the experimental result and discussion
is made. The EN8 steel are subjected to different heat treatment sequences:
annealing, normalizing, quenching and tempering at different temperatures at 2000C,
4000C, 6000C, 8000C, 9500C. Heat treated specimens were mechanically tested for
tensile properties, ductility, and hardness.
After quenching the tensile strength and hardness was increased due the formation
of martensitic structure. The crystal grain size was reduced.
After annealing it is observed that the hardness is reduced which softens the
specimen, the grain size is refined which in turns improves the machinability of EN8
steel.
After normalizing it is observed that uniform ferrite plus pearlite microstructure is
established and uniform grain size obtained.
Tempering the specimen after undergoing above process was found to have many
changes like the ductility and toughness was increased with some loss of strength,
hardness and ultimate tensile strength, it also possess good corrosion resistance.
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