Preparation of micro specimen.
Observations & Study : -
To study the Microstructure / to do metallographic examination of
the steel under the Metallurgical microscope. It is important
to prepare a specimen.
Following is the steps tp prepare the specimen :
1. To select the area from which specimen/sample is to
be cut, when we are investigating the micro-structure, we must know the area
from which we can check out the structure of the part.
2. Cutting of specimen; that particular sample must be
cut slowly under the proper flow of cutting fluid to avoid burning of the
sample.
3. Flat/Smooth surface; specimen must be flat/smooth,
cut piece can be grind to achieve the desired results
4. Intermediate and Fine grinding: - This
is carried out by using emery papers of progressively fine grades
The emery papers should be of very good quality in respect of uniformity
of particle size. Four Grades of abrasives used are; 220 Grit, 320 Grit, 400
Grit, 600 Grit
The specimen/sample first ground on 220 grit paper, so that all
scratches of cutting/Grinding wheel can be removed.
Grinding is then continued on the no. 320 paper, again turning the
specimen through 900, and polishing until scratches are not removed. Specimen
must be grind on the emery paper until the surface of the specimen is not free
from all scratches.
5. Rough Polishing
A very small quantity of diamond spray is put on the nylon cloth, (which
is rotating) the specimen is pressed against the cloth of the rotating wheel
with considerable pressure and is moved around the wheel.
6. Fine Polishing
The Polishing compound used is alumina which is put on the specimen or
on the polishing cloth, and specimen is again moved around the wheel until
don’t achieved the surface like mirror.
7. Etching
