Forging and Foundry Process | Interview Question and Answers Part 4
Forging and Foundry Process | Interview , Viva ,Oral Question and Answers
121. What do you mean by Baking sand?
It is the used sand which is left on the floor after the castings have been removed from the mould.
122. What is Core sand?
The sand which carries a high silica content and Is used for making cores is known as core sand.
123. What is Molasses sand?
It is sand which carries molasses as binder.
124. Mention the advantage of Molasses sand.
It is very useful for making moulds of small castings having intricate shapes and thin sections.
125. Which sand is called as Fat sand?
Facing sand is called as Fat sand.
126. What is the effect of sand grains on foundry sand.
Sand grains has a remarkable effect on the physical properties of the foundry sand.
127. Mention the types of sand grain surfaces.
Smooth, Conchoidal / rough surfaces.
128. Why the Smooth sand grain surface is preferred?
Because such a surface renders higher permeability, sinter point and plasticity to the sand mass & the percentage of binder required is also equally high.
129. What are the different shapes of sand grains?
The commonly formed shapes are rounded, sub – angular, angular and compound.
130. For light castings which type of foundry sand is preferred?
Light or fine grained sand is used.
131. For bench work which type of foundry sand is preferred?
A medium grained sand is preferred.
132. For large iron and steel castings which type of foundry sand is used?
Heavy or close sand is used. This sand should carry a high silica content, strong bond and low proportion of time.
133. What is the purpose of adding Binders to the foundry sand?
The purpose of adding a binder to the moulding sand is to impart it sufficient strength and cohesiveness so as to enable it to retain its shape after the mould has been rammed and the pattern withdrawn.
134. Name the common binders used in foundry ?
1. Organic binders
2. Inorganic binders.
135. List the commonly used Organic binders.
3. Linseed oil
4. cereal binders
5. Resins, like phenol and urea formaldehydes.
136. List the commonly used inorganic binders
4. Ball clay
5. Fire clay
6. Fuller’s earth.
137. Which is the most widely used inorganic binders ?
Bentonite is the most widely used inorganic binder.
138. What are Additives related to foundry ?
Additives are those materials which are added to the moulding sand to improve upon some of its existing properties or to impart certain new properties to it.
139. List commonly used Additivies.
1. Coal dust
2. Sea coal
3. Cereals or cornflour
4. Silica flour
5. Wood flour
7. Dexirin and mollases
8. Fuel oil
140. Where Coal dust additives are used?
It is mainly used in the sand used for grey iron and malleable iron castings.
141. Mention the main purpose of using coal dust additives?
Its main purpose is to react chemically with the oxygen present in the sand pores and, thus, produce a reducing atmosphere at mould – metal interface & prevent oxidation of the metal
142. What is Sea coal?
It is a finely ground soft coal.
143. What is the nature of Sea coal?
It restricts the mould wall movement and improves surface finish. It reduces permeability and hot strength of the mould and requires a higher percentage of water in the sand.
144. What is Pitch additives?
It is used to improves hot strength and surface finish on ferrous castings.
145. What is the role of Water on foundry sand?
Clay content added to the foundry sand will not give the required strength and bond until a suitable quantity of water is added to it.
146. Mention the quantity of water added to foundry sand.
Quantity of water varies from 2 – 8% according to different requirements.
147. What is the necessitity of testing Foundry sand?
The moulding sand is expected to have a good properties. These properties depend upon the size and shape of sand grains, their distribution and the amount of the other constituents added to the sand. In order to control
these factors effectively a number of tests are performed .
148. Name the Sand testing Equipments used in foundry laboratory.
1. Laboratory Balance
2. Sand Rammer
3. Drying Oven
4. A sieve shaker.
149. Name the commonly performed tests on foundry test.
1. Grain fineness test
2. Moisture content test
3. clay content test
4. Test for permeability
5. Refractoriness test
6. Strength test
7. Mould harness test
8. Core hardness test
9. Compacting factor test.
150. Why Grain fineness test is conducted?
The grain size of the moulding sand provides a significant effect on its permeability. Grains of similar or uniform sizes increase permeability whereas those of different size increase compactness, i.e, reduce the
permeability. The grain size should therefore, by properly controlled through adequate testing of the sand before use
151. Mention the methods used to test grain fineness?
1. Boswell method
2. Mechanical Sieve shaker method.
152. Why Moisture content test is necessary?
Excess moisture reduces permeability and too low moisture content reduces strength. Also many other defects in castings may occur on account of unbalanced proportion of moisture content or its uneven distribution. As such the testing of moisture content is invariably a must to control the same.
153. Why Clay content test is essential?
Clay is the principal binder used in most foundry sands. It may be present in the natural sands or may be added to it. It considerably affects the strength and other properties and hence the determination of its quantity
present in the sand is necessary.
154. Name the equipment used to conducted Moisture content test.
A very simple type of instrument, offered by M/s Metrimpex, Budapest, called a Rapid Moisture teller.
155. Name the equipment used to conducted Clay content test.
The apparatus used for this purpose is Mud / Clay content tester.
156. Why Permeability test is essential?
In order to allow the escape of steam and gases formed inside the mould when molten metal is poured into the latter. Permeability depends on the shape & size of sand grains, moisture content and clay content of the sand. It is also affected by the degree of ramming of the mould sand.
157. Name the equipment used to conducted Permeability test.
Apparatus called as Permeability meter or Permeability test.
158. Give the formulae used to determine Permeability number.
P = Vh/ p.a.t
Where, P = Permeability number
V = Volume in c.c of the air passing through the specimen
h = Height of specimen in cm.
p = Air pressure
a= Area of cross-section of the specimen in sq.cm
t = Time in minutes, taken by the air to pass.
159. Why Refractoriness test is necessary ?
The extent to which this property is required in a moulding sand depends on the pouring temperature of the molten metal and the wall thick ness of the casting to be made. The refractoriness of a particular sand is determined by its sintering temperature.
160. What do you mean by Strength test of Moulding sand?
Moulding sands are usually tested for their shear strength, tensile strength, compression strength and bending strength. A well designed apparatus, called the strength tester, is used to perform these tests.
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