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Correct answer is (b) False

For explanation I would SAY: In hot chamber die casting, the holding furnace for the LIQUID metal is integral with the die casting machine, whereas in cold chamber die casting, the metal is melted in SEPARATE furnace and then POURED into the die casting machine with the help of a ladle for each casting cycle which is also CALLED shot.

Correct option is (a) Thermosetting resins

To EXPLAIN I would say: The synthetic resins used in shell MOULDING are essentially thermosetting resins, which get hardened by HEAT. Phenol formaldehyde resins are mostly used, which combines with sand to form a PROPER mixture for shell moulding. The mixture formed has high strength and RESISTANCE to heat.

The correct choice is (a) ONE

To elaborate: In CO2 moulding, mould of sand is hardened by passing of Co2 for about one minute. The Co2 gas FORMS a WEAK acid that hydrolyzes the sodium silicate (Na2O, SiO2) solution to FORM amorphous silica gel which acts as the bond and sodium silicate itself also provides some bonding action.

Correct answer is (a) Cover die

Explanation: Mainly two parts of the casting machine, one is a cover die which is FIXED to the stationary platen and ANOTHER one is EJECTOR die which is fixed to the moving platen of the casting machine. Cover die also makes contact with the NOZZLE of gooseneck or with the shot chamber in the casting machine.

The correct choice is (c) Bronze mould

Explanation: Bronze moulds are used in some CASES of the SLUSH CASTING when the better surface finish of the exterior PART is REQUIRED. When the metal hardens, the mould is broken to remove the castings. The inside of each cast retains molten texture while the exterior part is very smooth and shiny.

Right option is (a) True

The explanation is: The punch and die portion are SEPARATED at the initial of the casting process and the holding furnace holds the molten metal at the requisite temperature. After the pouring of molten metal into the CAVITY, the punch is lowered down in such a WAY that it forms a tight seal to avoid INCLUSION of any gases to the castings.

Right CHOICE is (b) Metallic roller

Explanation: After the COMPLETION of the mould, the FLASK is balanced dynamically so as to reduce the occurrence of undesirable vibrations during the casting process. And the metallic ROLLERS are used in between the rotating mould and the stationary CASING to avoid the jerks and for the damping of vibrations.

The correct option is (a) True

To explain: Since the metal is ladled into the machine from the FURNACE, so it may lose the superheat and may cause defects in the castings such as COLD shuts. Also, there is a main disadvantage in the cold chamber DIE CASTING process is the longer cycle time needed as compared to the hot chamber die casting process.

The correct choice is (C) Water channels cooling

The explanation is: As the metallic die is used in the die casting as a mould, so the extraction of heat from the molten metal will not be easy. So for maintaining PROPER die TEMPERATURE, water cooling channels are used near the castings through the COVER and ejector die. This makes the proper solidification of the castings.

Right choice is (b) False

Best EXPLANATION: Investment CASTING is a very expensive PROCESS for producing castings because of larger MANUAL labour involved in the preparation of the pattern and the mould. And this process is also limited by the size and mass of the casting. The maximum limit on the mass of casting may be of the ORDER of 5 kg.

The correct choice is (B) SHELL moulding

The best I can explain: Cylinders, cylinder HEAD, automation parts, cast tooth ETC are casted using shell moulding.

Right OPTION is (c) Sodium silicate

Best explanation: To make the mould, the prepared pattern is DIPPED into slurry made by suspending fine ceramic MATERIALS in a liquid CALLED sodium silicate or sometimes another liquid ethyl silicate is also used for the preparation of slurry. The excess liquid is allowed to DRAIN off from the pattern to have an appropriate thickness of the mould.