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The correct ANSWER is (B) Casting POWDER

The explanation: In continuous casting, at the beginning of solidification of molten metal in the mould, the casting powder is added onto the top side of molten metal in the mould. This casting powder melts and penetrates between the SURFACES of the mould and solidified strand to minimize the friction, which leads to completion of the OPERATION in less time.

The correct ANSWER is (C) Centrifuging

Explanation: Centrifuging is a process which is used in order to OBTAIN higher metal pressures during solidification when the shapes of the casting are not axi-symmetrical. This process is mainly suitable for SMALL JOBS of any shape. In this method, a number of small jobs are joined together in a radial manner and then the further process of casting is done.

The CORRECT ANSWER is (a) True

For EXPLANATION I would say: As the metallic die is used which has a long life, it is of the order of 300,000 pieces for zinc and SIMILAR alloys. But for the aluminium alloys, it is approximately up to the 150,000 pieces of it. The reason is higher melting temperature of aluminium alloys that can destroy the mould with the PRODUCTION of castings.

The correct choice is (a) True

The explanation is: If the cycle time is very small, then the dies would readily get heated. Particularly in the sections such as sprues, or heavy sections of the casting, the temperature MAY be too HIGH. To MAINTAIN the required and uniform temperature, water is circulated through the HOT regions of the die.

The CORRECT option is (c) TriChloroEthylene

To explain: Before PREHEATING of the prepared mould, any of the wax remnants are DISSOLVED with the HELP of a SOLVENT such as TriChloroEthylene.

The correct answer is (b) False

Easiest explanation: Continuous passing of CO2 ALWAYS results in a strong and hard mould. More the passing of Co2 more will be the strength of the mould. Only the drawback is the decrease in permeability and COLLAPSIBILITY of the mould. Much passing of Co2 gas results into difficult breathing of the mould.

The correct option is (a) True

Easy explanation: There is no NEED for the gates and runners in the centrifugal casting process, which saves a LOT of molten metal. This MAKES the increase in casting yield, reaching almost 100%. And no any application of CORES makes the castings very economical for the large scale production.

The correct option is (C) Flash

Explanation: Flash is a TERM which is used for the EXCESS metal forced into the parting plane. Before using the castings, it is very necessary to remove flash together with any overflow PRESENT in the casting. This problem can be solved by implementing low-pressure die casting method, where the condition of excess metal cannot be possible due to UPWARD flow of molten metal.

The CORRECT answer is (a) True

To explain: In vacuum die casting, before the injection of molten metal, all the AIR PRESENTS in the die cavity is evacuated and then the die is closed. So by performing this operation, the molten metal does not experience any BACK pressure while injecting it into the die cavity, this MAKES the process easier.

Right choice is (b) False

Easy explanation: When the molten metal is ladled into the shot chamber of the MACHINE either manually by a hand LADLE or by an auto ladle, which is a form of a robotic device. This PROCESS reduces the contact TIME between the molten metal and the shot chamber, so the high melting temperature materials can be cast easily.

Correct ANSWER is (d) Jewellery and surgical instruments

To explain: As in investment casting, less mass and SIZE of casting with high complexities can be produced easily. So the jewellery and surgical instruments are produced easily in the investment casting. Other products like VANES and BLADES for a gas turbine, shuttle eyes for weaving, wave GUIDE for radars and impellers for turbo chargers can also be produced.

Correct option is (d) Trichloro-ethylene

Easy explanation: After the REMOVAL of WAX by melting and inverting the MOULD, some particles of the wax still stucked at the inside corners of the mould, and removal of them is very necessary to have castings free from defects. So, hot vapours of trichloro-ethylene are DISSOLVED with the wax remnants in the mould to remove the same.

Right option is (a) True

The BEST explanation: In SLUSH casting, ONE pour and multiple pour METHODS are used. One pour METHOD in which, finished or semi-finished products can be made by one slushing step and in multiple pour method, number of slushing steps are used for the casting that results into fast production of products.

The correct answer is (a) True

The explanation: Very carefully metered CHARGE of molten metal is POURED into the die cavity as to maintain the exact amount required for the casting. Excess of molten metal can lead to an increase in work time and the overall working EFFICIENCY is also DECREASES. So to avoid this problem, extreme CARE should be taken at the time of pouring.

Right option is (b) False

Easiest EXPLANATION: The coatings can be both of insulating type and lubricating type. The coatings can be applied thicker at surfaces, which NEED to be cooled slowly, for example, SPRUES, risers, thin sections and runners. More the thickness of the coatings less will be the heat transfer RATE from the CASTINGS.

Right answer is (b) False

The best explanation: The removal of all the gases from the DIE cavity makes a vacuum INSIDE the cavity, so there is no pressure or force inside the cavity which COULD be opposite to the injecting pressure of the molten metal. So, the molten metal enters much faster into the die, thereby decreasing the fill TIME.

Right ANSWER is (C) Keeping of pattern at too LOW temperature

To explain: When the mercury is used in place of wax as a pattern material, it has an advantage that it does not expand when changed from solid to liquid state as wax. But the main disadvantage or drawback is keeping the pattern at such low temperature, which is MAINLY responsible for its less USEFUL.

The correct option is (a) True

To elaborate: In the process of STUCCOING, DRY REFRACTORY grains such as zircon or silica are stuccoed on the liquid ceramic coating. A small shell is formed around the pattern, which is to be cured and then the process of DIPPING and stuccoing is continued with ceramic slurries to achieve a well desired thickness of the MOULD.

Right choice is (d) All of the mentioned

The explanation: In PMC the CORES can be MADE out of any of these MATERIALS.

The correct choice is (b) False

Easiest explanation: Wide adopting of continuous CASTING has changed that scenario by DIRECTLY casting of slabs, BILLETS and blooms without going through the rolling PROCESS. So in continuous casting, there is no REQUIREMENT of any rolling operation, this makes the process very fast and economical too.

Correct choice is (a) True

For explanation: In centrifugal casting, the inclusions such as slag and oxides get SEGREGATED towards the centre and can be easily removed by a machining PROCESS. And also the application of pressure on the metal throughout the SOLIDIFICATION causes the porosity to be ELIMINATED and gives rise to dense metal.

The correct ANSWER is (b) False

Explanation: Very good surface finish of the order of 1 micron can be OBTAINED in low-pressure die casting method because of application of METALLIC dies. The surfaces generated by this method of casting can be directly electroplated without any further PROCESSING. This method is economical for moderate or large SCALE production.

Correct answer is (b) False

The best explanation: When the mould cavity is FILLED with molten metal, the pressure in the crucible is removed. This ALLOWS the molten metal to flow back to the crucible through the tube. Then after solidification, the sides die opens and the TOP die is raised vertically. And the casting moves with the top die and ejected onto a TRANSFER tray.

Correct answer is (a) True

Best explanation: Low-pressure die casting is not new; some changes are adapted to the permanent mould to generate new characteristics and better properties to the casting. So in this PROCESS, the permanent mould and the FILLING system are PLACED over the furnace containing the MOLTEN ALLOY in it.

Right choice is (a) 0.3 to 1.5

For explanation: In low-pressure die CASTING, compressed gas is basically used at a pressure typically ranging from 0.3 to 1.5 bars to force the molten metal to rise slowly through the CERAMIC riser tube that is connected to the MOULD. Pressure should be below atmospheric pressure to easily PULL the molten metal into the cavity.

Correct CHOICE is (b) False

For explanation I would say: In gravity die CASTING, liquid METAL enters into the cavity by means of gravity force only, as shown in below figure. It is used to produce a simple shape of the objects made up of HIGH fluidity materials. And DUE to fast rate of cooling, fine gain structure will be developed in the castings which are having more strength and hardness.

The correct choice is (c) 100-250,000

Explanation: As a reusable metallic DIE is used as a mould that is beneficial for large scale production. A large NUMBER of CASTINGS around 100-250,000 can be produced easily without any in-between maintenance, to achieve more no. of castings sometimes repairing is required to REMOVE any distortion if produced in the mould.

Correct answer is (b) False

The explanation: Die casting mainly has two PARTS. One part is the STATIONARY half or COVER die, which is fixed to the die casting machine. The SECOND part is the moving part or ejector die that is moved out for the extraction of the casting. The casting cycle basically starts when the two parts of the die are apart.

The correct option is (B) False

To explain: Metallic core is not PREFERABLE that the sand core, because the metallic core cannot be complex with UNDERCUTS and the LIKE. Also, the metallic core is to be withdrawn IMMEDIATELY after solidification; otherwise, its extraction becomes very difficult because of its shrinkage.

Right answer is (B) False

The explanation: The moulds are pre-heated to a TEMPERATURE of 100 to 1000 ⁰C, depending on the complexity, size and the metal of the casting. This is mainly done to reduce any LAST traces of wax left off and permit proper filling of all MOULD sections, which are too thin to be filled in a cold mould.

Correct choice is (c) CENTRIFUGING

Explanation: More than a single object is connected radially through a central SPRUE in centrifuging. But the CASTINGS need not be symmetrical ALWAYS, unlike other centrifugal casting processes.

The correct CHOICE is (a) Phenol FORMALDEHYDE

The best explanation: Phenol formaldehyde is used as resin in shell MOULDING. It acts like a thermoplastic material.

Correct option is (B) False

The EXPLANATION: In slush casting, if porosity is present in the mould PART, then it can cause detrimental effects on the casting part such as pin-holing, surface gloss reduction and voids in the casting. So, EXTREME care should be taken while selecting the die or for the preparation of the same.

The correct option is (d) MOULDING material

Best EXPLANATION: In squeeze casting, time duration is MAINLY determined by the casting configuration, alloy type and heat transfer conditions. After the completion of the SOLIDIFICATION process, pressure is no longer required in the operation. Then the casting is safely taken out from the DIE for the further process of machining.

Right CHOICE is (c) STEEL rollers

The explanation is: In continuous casting, steel shell is mechanically SUPPORTED by steel rollers as it moves down through the secondary cooling zone for the complete solidification then the WATER is sprayed onto the shell surface to solidify the casting, after that it is CUT to the desired length of the billet or slab.

The correct CHOICE is (a) Tundish

Best explanation: In continuous casting process, the molten steel is collected in a ladle and kept over a refractory lined intermediate POURING vessel which is TERMED as tundish. The steel is then poured into water COOLED vertical copper MOULDS which are approximately 450 to 750 mm in length.

Right choice is (a) Crank cases

The explanation is: Crank cases are very easy to cast by low-pressure die casting, as the upward flow of molten metal reaches to every SMALL CORNER of the mould and makes the homogenous NATURE of castings. Many other COMPONENTS like magnetos, handle bar housing and other decorative items of AUTOMOBILE can also be casted by low-pressure die casting method.

Right OPTION is (c) Aluminium

The best explanation: The hot chamber die casting process is basically used for the low melting temperature ALLOYS. But, for MATERIAL such as aluminum, its high melting temperature makes it difficult to cast by hot chamber die casting process, because continuous contact of gooseneck with the MOLTEN metal can destroy the gooseneck material.

Right choice is (d) Air jets cooling

Easy EXPLANATION: The cooling RATE can affect the quality of the casting, so care should be taken to see that the casting is properly COOLED before ejecting from the DIE. For the proper cooling of the top and bottom dies of the casting system, air jets are used which circulated through the dies and takes AWAY the heat.

Correct CHOICE is (a) True

To explain: It is difficult to securely POSITION the metallic core as a single piece due to the dimensional VARIATIONS that are likely to OCCUR. So the collapsible metal cores (multiple piece cores) are sometimes used in permanent moulds, but the DESIGNER has to provide coarse tolerance on the dimensions.

Right answer is (B) False

The explanation: CORES are used in permanent mould casting for making any HOLLOW portions in the casting. The cores can be MADE out of metal or sand also when sand cores are used in the casting, the process is called semi-permanent moulding. The sand core of complex shapes can be used with undercuts easily in the casting.