1. Why the air already present inside the corebox is necessary to be evacuated before pressurised air is blown into it?
a) The air has comparatively low pressure hence, distortion occurs
b) Hot tears will occur on the surface
c) It will cause poor sand distribution and poor compaction
d) Nothing will happen as the pressure of incoming air neutralises inside air pressure
Explanation: The air inside the corebox does not get enough time to escape hence sand distribution and compaction is poor.
2. Why should the finishing of the core be made good enough?
a) The intricate shapes made are difficult for machine finishing
b) The size of the cavities and contours must be accurate to enable perfect assemblies
c) It reduces machining cost and time invested for that
d) All of the mentioned
Explanation: The cores are used where machining cost or time is the foundation or is difficult to achieve and hence finishing is done on the core itself.
3. Which of the following core cannot be classified by the nature of core material employed?
a) Dry sand core
b) Shell core
c) Sodium silicate core
d) Oil bonded core
Explanation: Dry sand core is a core which comes under state or condition of core, while all other types of cores come under nature of core materials employed.
4. Which of the following will not be classified under the type of core hardening process employed?
a) Nishiyama process
b) Ram up core
c) Furan no-bake system
d) Cold set process
Explanation: Ram up core cannot be classified under the type of core hardening process employed, while the remaining can be classified under it.
5. Which of the following core cannot be classified under the shape and position of the core?
a) Balanced core
b) Ram up core
c) Shell core
d) Horizontal core
Explanation: Among the following, shell core is the core which cannot be classified under shape and position of the core, while the remaining others can be classified under it.
6. Which of the following cores are produced by mixing silica?
a) Green sand cores
b) Dry sand cores
c) Oil bonded cores
d) Resin bonded cores
Explanation: Oil bonded cores are produced by adding silica and a small amount of linseed oil, and then polymerized.
7. In resin bond cores, the core is baked at what temperature?
a) 275°F – 390°F
b) 375°F – 450°F
c) 485°F – 645°F
d) 775°F – 880°F
Explanation: For such types of operations, the core is known to be backed at a good amount of temperature. In resin bond cures, the core is baked in the core box at a temperature range of 375°F – 450°F.
8. In hot box process, core box is heated up to what temperature?
a) 220°F – 300°F
b) 250°F – 320°F
c) 350°F – 500°F
d) 420°F – 550°F
Explanation: In the hot box process, core box is known to be made up of cast irons or steels or aluminium metal. It is heated in between the temperature range of 350°F – 500°F.
9. Sodium silicate reacts with carbon dioxide to give what?
a) Sodium dichromate
b) Sodium sulphide
c) Sodium bicarbonate
d) Sodium carbonate
Explanation: When sodium silicate is made to react with carbon dioxide gas, it is known to yield sodium carbonate and silica gel.
10. Silica gel is formed when sodium bicarbonate reacts with carbon monoxide.
a) True
b) False
Explanation: Silica gel is formed along with sodium carbonate when sodium silicate reacts with carbon dioxide.