It is my second review on my project with partially completed results with data.

1. Comparative studies on properties
of mould sands of different mesh
sizes.
UNDER GUIDANCE BY R. NAIDU SIR
By
N.C. Umesh

2. Backdate
 My project is comparative studies on properties of mould sands at
different composition of moisture, binder and grain size.
 Different mould sands have different clay content which shows different
properties based on mesh size.
 Since sand are grains are heat resistant with minimum size of 0.02mm
which is ideal for most foundry practice.
 Angularity and granulometry of particles are decisive for volume weight,
porosity and ensuing permeability and penetrability of a mixture, thermal
conductivity of a mixture and affect even strength of moulds and cores to
a large extent.

3.  Mould sands commonly mixed with binder and water at certain percentage for
providing industrial casting requirements.
 Binders are added to give cohesion to moulding sands and it provide strength to
the moulding sand and enable it to retain its shape as moulding cavity.
 For various testing of mixed composition mould of different sized sands,
specimen is prepared using sand rammer , specimen tube and specimen pusher.
 Different composition analysis are…

4. Water in
total(%)
water
ml
Binder in
total(%)
Binder
gms
sand in
total(%)
sand
gms
1 6.92 25 9.97 36 83.11 300
2 8.10 30 10.8 40 81.1 300
3 10.32 40 12.37 40 77.31 300

5. Testing methods for mould specimen
 Grain size analysis:
Grains size and shape effect various properties of mould.
 Clay content test
Nature clay plays important role on properties.
 Hardness test:
Hardness of the mould surface tested with the help of an “indentation hardness tester”
 Air permeability test:
Helps to determine the escapebility of gasses through mould.
 Green Strength test:
Combination of grain size and composition gives strength to mould.

6. Grain size analysis
 The grain size, distribution, grain fitness are determined with the help of the
fitness testing of moulding sands. The apparatus consists of a number of
standard sieves mounted one above the other, on a power driven shaker.
 Commonly, its is named as sieve analysis machine.
 Here,aside from grain size determination, we collect different mesh size sands
at different platform for further experimental.
 Different microns effect volume matrix distribution of mould specimen.

7. Clay content
 Clay influences strength, permeability and other moulding properties. It is responsible for
bonding sand particles together.
 Common procedure:
1. Separate 50 gms of dry moulding sand and transfer wash bottle.
2. Add 475cc of distilled water + 25cc of a 3% NaOH.
3. Agitate this mixture about 10 minutes with the help of sand washer.
4. After the sand mixture has settled for about 10 minutes, Siphon out the water from the wash
bottle and repeat till clear mixture obtain.
5. Dry the settled down sand.
6. the clay content determined from the difference in weights of the initial and final sand samples.
 Percentage of clay content = (W1-W2)/(W1) * 100
Where, W1-Weight of the sand before drying,W2-Weight of the sand after drying.

9. Hardness test
 Hardness of the mould surface tested with the help of an “indentation hardness
tester”. It consists of indicator, spring loaded spherical indenter.
 The mould hardness is measured by a method similar to the brinell hardness
test.
 A spring loaded steel ball with a mass of 0.9kg is indented into the standard
specimen
 The depth of indentation can be measured on the dial guage which show units
from 0 to 100.
 when no penetration occurs , then the mould hardness of 100 and when it sinks
completely the reading is zero indicating a very soft mould.

11. Permeability test
 The quantity of air that will pass through a standard specimen of the sand at a
particular pressure condition is called the permeability of the sand.
 Following are the major parts of the permeability test equipment:
1. An inverted bell jar, which floats in a water.
2. Specimen tube, for the purpose of hold the equipment
3. A manometer (measure the air pressure)
 It consists of cylindrical water tank in which an inverted bell or air holder ,
properly balanced is floating . by properly opening the three way value , air
which is trapped under the bell will flow through the specimen.

12.  Steps involved are:
 1. The air (2000cc volume) held in the bell jar forced to pass through the sand
specimen.
 2. At this time air entering the specimen equal to the air escaped through the
specimen
 3. Take the pressure reading in the manometer.
 4. Note the time required for 2000cc of air to pass the sand
 5. Calculate the permeability number
 6. Permeability number (N) = ((V x H) / (A x P x T))
 Where,
V-Volume of air (cc),H-Height of the specimen (mm),A-Area of the specimen (mm2),P-Air pressure (gm
/ cm2),T-Time taken by the air to pass through the sand (seconds)

14. Green strength Test
 Strength of mould sample are determine in 3 ways
1. Compression strength
2. Shear strength
3. Tensile strength
 The moulding sand contains moisture is called green sand.The green sand
particles must have the ability to cling each other to give sufficient strength to
the mould. This is called green strength.
 Generally, test is carried out in universal tensile machine.

15.  Green compression strength:
Green compression strength or simply green strength generally refers to the stress required to
the sand specimen under compressive loading. The sand specimen taken out of the specimen tube
immediately (any delay causes the drying of the sample which increases the strength) put on the
strength testing machine and the force required to cause the compression failure is determined.
 Green shear strength:
With a sand sample similar to the above test, a different adapter is fitted in the universal machine so
that the loading now be made for the shearing of the sand sample. The stress required to shear the
specimen along the axis is then represented as the green shear strength.

17. Results and discussion
GRAIN SIZE CLAY CONTENT HARDNESS PERMEABILITY COMPRESSION
STRENGTH
SHEAR
STRENGTH
425 microns 12% 58 50 1.7 0.84
300 microns 12% 65 126 1.22 0.72
212 microns 12% 74 - 0.81 0.64
For this, we prepared composition with 25ml water conent, 36g binder percentage

18.  AS we can see in above tabular column :
• With increase in mesh size, hardness of mould sample increase.
• Permeability number increase along with mesh size, which decrease escape chances of
air.
• As we come down the mesh line, strength will also lower because angurality of grains
change with mesh sizes.
 Thus we can draw near point graph line for comparison between sands.