Report Exp 5

7/30/2019 Report Exp 5

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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#top


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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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