This set of Foundry test focuses on “Fettling and Cleaning of Castings”.
1. _________ is the name given to the removal of cores from the casting.
Explanation: Fettling is the name of the process to cover all those operations which help to give the casting a good appearance after the casting has been shaken on a vibrator and then taken out of the sand mould.
2. __________ portions sticking out of inside the castings are removed by poking and action of the metal rod.
Explanation: It may be difficult to remove dry sand and hardened cores in the absence of suitable equipment. Hammering or vibrations imparted to the cores does not loosen and break them up. Hence they are removed by poking action using a metal rod.
3. Steel castings require considerable more cleaning than those of iron and brass.
Explanation: Steel castings, because of their high melting and pouring temperatures and consequent burning of the sand in contact with the molten metal, the possibility of forming of the scales is high. Hence they require more cleaning.
4. _____________ is used for removing adhering sand from the castings.
b) Air blasting
c) Wire brush
d) All of the mentioned
Explanation: Rumbling or Trumbling employs a barrel which is rotated at a certain speed and the castings are put and the sand is removed. Air blasting is a method in which air is supplied at a high speed to remove the sand. Wire brush does the same operation. Hence all the above are used to remove the sand.
5. Wire brush is used for non-ferrous production.
Explanation: A wire brush consists of hardened steel wires embedded in a block of wood. The materials on which it can be used as grey cast iron, malleable cast iron, steel castings etc where normal clean strip is sufficient and full cleaning operation may be avoided.
6. ______________ is used as an abrasive in the shot blasting method.
b) Coal tar
c) Chilled iron grit
Explanation: Chilled iron grit or grit is made by crushing shot. It has irregular sharp edges which act as thousands of tiny chisels and produce more of the scrubbing action than shots in a shot blasting method.
7. ____________ force is responsible for cleaning in mechanical blast method.
a) Gravitation force
b) Tensile force
c) Centrifugal force
d) Shear force
Explanation: The centrifugal force aid in issuing a stream of abrasive particles which impinges on castings being trumbled on an apron conveyor. Due to this high speed action of the centrifugal impellers, the particles are cleaned.
8. ____________ involves a danger of retaining acid in small interstices of castings.
a) Shot blasting method
d) Hydro blasting
Explanation: Pickling is one of the methods used in chemical cleaning of the castings manufactured. Pickling makes use of dilute acids for removing sand from the surface and inaccessible pockets of the castings. Hence, there is a danger of retaining a little amount of acid.
9. ____________ castings are pickled in hydrofluoric acids.
Explanation: Iron that is the ferrous castings are pickled in hydrofluoric acid (48% of hydrofluoric acid and 25 parts of water). Hydrofluoric acids attack sand on the castings and hence the cleansing becomes easy.
10. Automatic shot blasting plants are capable of high production rates.
Explanation: The automatic shot blasting process is a continuous shot blast cleaning operation can be approached by skip loading and by dual turntable plants so that loading and unloading of the castings can take place outside the work chamber when the blasting is going on. Hence, it can be used for a high production rate.
Sanfoundry Global Education & Learning Series – Foundry and Forging.
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