Sand Control
Tests
Sand Control Tests
A large variety of sand molding materials is used in foundries for manufacturing
moulds and cores. They are:
• Molding sand,
• Backing sand,
• Facing sand,
• Parting sand, and
• Core sand
The choice of molding materials is based on their processing properties. The
properties that are generally required in molding materials are:
• Refractoriness,
• Green strength,
• Dry strength,
• Hot strength,
• Permeability, etc…..
Many factors are affecting the properties of Molding Sand, like grain shape, grain
size, grain distribution, and the content and the type of binders, additives and
moisture.
The need for systematic evaluation of the working qualities of molding sands has led
to the development of a wide range of sand control tests.
1. Tests for Raw Sand:
(a) Grain size (fineness number) and distribution.
(b) Fines content.
(c) Refractoriness.
(d) Moisture contents.
(c) Chemical analysis (Si02, alkalies, acids, etc.......).
2. Tests for Sand Mixture Contents:
a) Moisture content
b) Clay content.
3. Tests for the Sand Mixture Suitability for Molding:
a) Moldability.
b) Flowability.
4. Tests for the Sand Mixture Suitability for Casting:
a) Permeability.
b) Strength tests. (Compression, shear, bending, etc...)
c) Hardness test.
Questions and Problems
1. What properties are desirable of molding sand from the stand point of sound
castings?
2. Explain the importance of permeability of molding sands.
3. State the essential ingredients of molding sand.
4. Explain the method of determining the moisture content in molding sand.
5. What is the role played by clay in molding sand? What is the method adopted for
determining the clay content in a molding sand?
6. What is meant by grain fineness number? Explain the procedure for determining
this number for molding sand.
7. How is a standard sand test specimen prepared for testing the strength or
permeability?
8. Describe the method used for determining the permeability of any molding sand.
9. State the detriment caused to the mould properties if the molding sand contains
(a) Too much clay,
(b) Too much moisture.
10. A sample of molding sand of 50 g is weighed after washing and drying and found
to weigh 41.6 g. What would be the clay percentage in this sand sample?
11. Calculate the permeability number of a sand specimen if takes 1 min 15 s to pass
2000 cub cm of air at a pressure 6 g/sq cm, through the standard sample.
12. A certain yellow sand sample has given the following sieve distribution.
12
20
30
40
50
70
100 140
200
270
Pan
Sieve No
Retained, % 2.50 4.50 3.50 3.50 2.00 4.75 3.80 6.00 10.47 14.17 38.52
Calculate the grain fineness number and specify application for which this sand is
suitable if its sinter temperature range is 1050 - 1100 oC.
13. A sand specimen with a permeability number of 140 takes 45 seconds to pass
2000 cub cm of air at a pressure of 5 cm. Calculate the height of the sand
specimen.
14. The hypothetical molding sand sample when sieved through the standard sieves
was found to retain the following amounts of sand on the respective sieves.
Sieve No
Retained weight; g
12
20
30
40 50
0.73 1.26 1.03 1.44 2.2
70
3.57
100 140
200 270
5.77 14.15 11.13 3.98
Plot the cumulative grading curve and calculate the grain fineness number.
Pan
4.67