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Faculty of Engineering
Industrial Engineering Department
Metrology Laboratory
Exp. #1
Angular Measurement
Sine bar
Student Name : Jalal Abu Taha
ID # : 20090029037
Date : 21 / 2 / 2012
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Objectives:
1. Selecting a representative specimen.
2. Grinding and polishing the specimen.
3. Etching the polished mirror-finished surface of a specimen to reveal
its structure.
4. Using the metallurgical microscope.
5. Examining the structure of the specimen under the microscope, and
To be able to understand the behaviour of the grains when exposure
the rays come from microscope.
Materials and Equipments:
We used in this lab (grinder-polisher machine) it a disk like shape and it
rotatets in specific velocity we can determine it manually, in grinder
machine we use a salt paper with different grades (120-1200) to make the
specimen smoothest start from 1200, and we use water (H2O) continuously
during and after grinding for different reasons like: (to keep the surface
clean and to cold the specimen).
But in polisher machine we use fine piece of cloth like velvet cloth to make
the surface smoother and during this process we used (diamond spray),
which it is a very hard material with small grains and toxic odour, which
make the surface of the specimen smoother and has a mirror like surface.
In Etching process we used a chemical materials (Natal and HNO3) these
chemicals attack the boundaries to make it appears when we using
Microscope.
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In the final step we used (Metallurgical Microscope) which connected with a
computer and includes two lens:
1. Fixed piece lens, which has a fixed magnification
2. Objective lens, which has vary magnification (5X 100X).
Fig(1): metallurgical microscope
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Fig(2): metallurgical microscope dimensions
We used in this lab a steel cylindrical shape specimen, with a diameter of
20mm or 20 mm square and a thickness not more than 12 mm, see fig
below:
fig(3): geomtry of specimen
Procedure:
You will have a ready cylindrical specimen with a diameter 20mm and
thickness 12 mm, I mean you didnt do the cutting step and mounting step.
After that take the specimen and go to grinder machine which contains sand
paper, then during use hand-grinding operations on progressively finer
grades of sand paper, the specimen should be washed in water and rotated
through 90 at each change of sand paper, to prevent the carry-over of
relatively coarse grinding particles from a paper to the next finer grade sand
12 mm
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paper, and be careful to your fingers because you may be hurt yourself if
you dont catch the specimen correctly, notice that water is very important in
this step for cleaning the surface and remove the grinding particles that
produces from grinding and to colder the specimen to avoid deformation that
may be happened cause high temperature.
Then wash the ground surface of the specimen with water, clean it with
alcohol, and dry it with an air dryer, in order to prevent any dirt or
contamination or grinding particles from being carried over the polishing
cloth in the next step.
After that polish the ground surface of the specimen using the rotating disk
polishing machine, a constant drip of suspended polishing powder in water
is necessary to keep the cloth covering the disk wetted thoroughly , during
the polishing operation. The machine should rotate with a reasonable speed
and light pressure should be used in pressing the surface of the specimen
against the wetted cloth of the disk. Scratches may be formed on the
polished surface, if a heavy pressure is applied, caused by the deeply
embedded grit particles in the cloth. Moreover, the use of light pressure andreasonable rotating polishing machine speed are less likely to cause the
specimen being suddenly thrown by the centrifugal force of rotation across
the laboratory.
After finished this step clean the specimen with alcohol, shake it to remove
the surplus alcohol, and then dry it with the air dryer. Never touch the
specimen surface by the fingers.
Then use proper method to apply the Etching solution to the prepare surface
of the specimen, by immersion of the surface in the Etching solution, after
etching wash quickly the etched surface with water, then swab it with
alcohol and dry it.
After that put the specimen under the objective lens of the metallurgical
microscope and use the proper magnification power, then sketch the micro-
structure of the etched surface of the specimen, as it observed through the
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eye-piece lens of the metallurgical microscope. A photograph of the etched
surface will be quicker and better, if it is available.
fig(4):Specimen have a morphous surface
Results and Discussion:
Fig (5): metallurgical microscope
Metallurgical Services offers it's expertise on study of metallography
structure of metals. A CARL ZEISS microscope with a computer interface,instant micrograph under magnification ranging from 50X to 1000X can be
obtained for detailed study and analysis.
From metallurgical microscope that we see above we obtain the following
images for the grains:
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Fig(6): microstructures grainsof Aluminum Fig(7): microstructures grainsof Annealed Mild
Steel
Fig(8): microstructures grainsof Cast Iron. Fig(9): microstructures grainsof Cold Worked
Copper
Fig(10): microstructures grainsof MartensiteFig(11): microstructures grainsof Mild Steel
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Fig(10): microstructures grainsof Stainless
steel1
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As we show the grains have different colors, from white to black with
different grades, the rays (light) which come from microscope interact with
grains, and the grains which appears in dark black it is absorbs more light
and the grains which appears in white reflects all light and dont absorb
anything, so we reach from this that as the grains absorbs more light theyappears darker, and the grains which absorbs less light they appears lighter
(white), and rest of the grains appears between black and white degrees
subject to absorbing amount of light.
Metallurgical Services offers it's expertise on study of metallography
structure of metals. A CARL ZEISS microscope with a computer interface,
instant micrograph under magnification ranging from 50X to 1000X can be
obtained for detailed study and analysis.
Test Facilities
Instruments No. Make
Metallurgical Microscope (AXIOVERT 100 A) 1 German
Microscope Magnification (100 - 400) 1 Indian
Back To Top
Charges
Test
Rate per Specimen
(Rs) Rates from 1st
April 2008
Micro / Inclusion (Method A) Examination per location 300/-
Inclusion Rating Method D 2500/-
Micro Examination with 3 copies of photograph 350/-
Only Photograph - 3 Copies 200/-
Mounting Charges for small pieces 50/-
Macro Examination on Plate
Upto 25mm thick
Above 25mm thick
120/-
150/-
http://www.metallurgicallab.com/metallographic_testing.html#tophttp://www.metallurgicallab.com/metallographic_testing.html#top7/30/2019 Report Exp 5
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Macro Examination on Pipes / Tubes
Upto 4" NB
Over 4" NB to 8" NB
Over 8" NB to 12" NB
Over 12" NB to 18" NB
Over 18" NB
120/-
140/-
170/-
200/-
225/-
Macro Examination on Mock-up sample 175/-
Macro Examination on Forging 275/-
Macro Examination on Fillet 175/-
Failure AnalysisCharges on
request
Macro Examination with Photographs 450/-
Step Macros without photographs (each step) 1000/-
Step Macro with photograph (each step) 1250/-
Macro Measurement (MLP / Penetration, etc) each 150/-
Depth of Attack 500/-
Micro for Duplex Grain Structure 450/-
Ferrite by Metallograph 1800/-
Banding Index 1700/-
Internetallic Phases 750/-
Inclusion Rating E & S, Method D 2500/-
Inclusion Rating E & S, Method A 250/-
Nodule Count, Nodularity / area fraction 1000/-
Area Fraction (three phase) 2500/-
Mesh Size 250/-
Coating / plating thickness / mesh size 250/-
Austenitic Grain Size with photographs (up to 3 samples) 5,500/-
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Every additional sample 3000/-
Etching reagents compositionMetals and alloys which
can be etched
Etchingtime
(seconds)
Nitric (natal)Conc. Nitric acid Absolute
methyl or ethyl alcohol4 cc
96 ccCarbon steels and cast
irons10-30
Picric (picral)Picric acid Absolute methyl
or ethyl alcohol4 gm96 cc
Carbon steels and low
alloy steels (etch pearlite,do not reveal ferrite
grains)
15-60
Hydrochloric+ nitric acid+water
Hydrochloric acidnitric acid
waterpicking retainer (flour trace)
(used about 70-80C)
10 cc3 cc
100 cc18/8 stanless steel 15-60
Ferric chlorideFerric chloride
conc. Hydrochloric acidwater
10 gm30 cc200 cc
Copper and its alloys suchas bronzes, high zinc
brasses and aluminum
bronzeAluminum hydroxide+
hydrogen peroxide
Aluminum hydroxidewater
hydrogen peroxide
5 parts5 parts2 parts
Copper and its alloys
Hydrofluoric acid+ nitricacid
Hydrofluoric acidnitric acid
2 cc5 cc
100 ccAluminum an its alloys
Ethylene glycol+ nitricacid
Ethylene glycolDistilled water
Conc. Nitric acid
75 cc24 cc1 cc
Magnesium and its alloys
15-60(usedfreshly
preparedsolution)
Table (1): Etching reagents for micro-examination
Conclusions:
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This lab was very successful and able to achieve its goals, we become
having a deeper understand for microstructures of metals, we become
familiar with metallurgical microscope and knowing it has focal force (50X-
1000X), and we knew that the mirror like surface for metals reflect the light
so we cant see the structure under microscope unless we do etching process.
We learnt that the high temperature affect to the microstructure, so we tried
to decrease it as much we can by water, and removing grinding object is
important step.
We was very pleased when we saw microstructure grains with different
grades between black and white because we have deeper understand of the
structure.
Now we have ability to make conversion between several tests with base on
tables and pictures we got them from internet:
(www.tcreng.com), (www.metallurgiclab.com/metallographic testing)
The resources of error in this lab was:
- Human resources , I mean may be the person who make the experiment
dont follow procedure exactly and make something wrong, like using water
during grinding, using diamond spray, rotate the specimen 90 each steps,
finger touch as we mention in the procedure.
- The surface finish of specimens, we have more accurate reading when the
surface finish become better, and we have wrong reading if the surface finish
isnt good, I mean the surface must be mirror like surface before etching
step.
- May be the microscope or computer or other device have defects, or
etching solution isnt suitable for the specimen, or time of etching is wrong,
size of specimen..etc
Suggestions:
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I suggest that to make deeper understand for this experiment we must let the
student to participate in the lab and do some possible steps of the lab such as
grinding or polishing, the student can do it without helping because it is easy
test and not complex.
The chairs in the lab must be more comfortable to ensure that the student
will rest and then will have more understand.
References
Strength and mechanics of material book
Manual of lab material.
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