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Correct option is (b) False

Explanation: Since the SHELLS are thin, and pouring of molten METAL into the shells may cause an imbalance which further leads to failure of the castings. So to AVOID this, it may require some outside SUPPORT to withstand the pressure of the molten metal and to form the castings efficiently with PROPER balance.

The correct option is (b) False

The explanation is: When manufacturing by slush casting, it is very DIFFICULT to control the strength and other MECHANICAL properties accurately because of the formation of irregularities at the inside portion of the casting. Properties can be enhanced or IMPROVED by PROVIDING heat treatment to the metal casting.

The correct choice is (b) False

To ELABORATE: It is not POSSIBLE to make un-symmetric shape of casting in centrifugal casting, only certain shapes which are axi-symmetric and having CONCENTRIC HOLES are suitable to make in the centrifugal casting. And equipment are also expensive, so this method is suitable only for large scale production.

Correct choice is (a) True

Explanation: A large amount of heat will be absorbed by the mould material as the METALLIC mould would be used. So for the continuous extraction of heat, it is important to MAKE PROVISION in the construction of the mould. This is mainly done to increase mould life and to have better casting cycle TIMES.

Correct option is (a) Grey CAST iron

The explanation is: In gravity die CASTING, fine-grained grey cast iron is the most generally used die material. Sometimes alloy cast iron, alloy steels (H11 and H14) and C20 STEEL are also used as die material for very large volumes and large parts. For small volume production of ALUMINIUM and magnesium, mould made of GRAPHITE is preferred.

Right choice is (d) FLUIDITY of pouring melt

For explanation: The mould material is basically selected on the considerations of the SIZE of the casting, pouring temperature and the frequency of the casting cycle, which all together DETERMINE the total heat to be borne by the die. Fluidity of the pouring melt can be dependent on the shape of mould, but it is TOTALLY independent for the SELECTION of moulding material.

The correct OPTION is (d) Gooseneck

Easy EXPLANATION: A gooseneck is used for the pumping of liquid metal into the die cavity. It is made of ductile iron or of CAST steel. The gooseneck is SUBMERGED in the holding furnace containing the molten metal. Then a PLUNGER which is hydraulically operated moves up in the gooseneck to open the entry port for the entry of liquid metal into the gooseneck.

Correct answer is (a) Slush casting

Explanation: Slush casting is USED to MAKE casting which is actually HOLLOW projections. HENCE, it is ALSO called a hollow casting.

The correct option is (c) Aluminium oxide

To elaborate: After the preparation of the sand mixture by ADDING sodium silicate to the sand, the next step is to add ADDITIVE, in which mainly aluminium oxide is added and sometimes molasses are also added to impart the favorable PROPERTIES and for the improvement in the collapsibility of the sand mix.

The correct choice is (b) False

For explanation: Extended holding time NEVER MAKES the castings of good strength; even it may CAUSE wall cracking and problems with punch withdrawal due to THERMAL contraction of the casting. So a rule is set in the squeeze casting that the maximum holding time is about one second per mm of SECTION thickness.

The correct choice is (b) False

To explain I would say: The COOLING rate of the molten metal is mainly increased during the SOLIDIFICATION stage of the squeeze casting. The instant contact between the melt and the die surface produces a rapid heat transfer condition that MAKES the casting of good harden-ability with FINE grain structure.

Right CHOICE is (a) True

Explanation: In continuous casting, DEPENDING on properties required by object, different cooling RATES are provided. For example, intense cooling by water sprays makes the casting of fine structure and with good HARDNESS, and if the air cooling is done then the casting of a coarse structure is MADE with good ductility in it.

Right choice is (b) False

The EXPLANATION: Not only SAND moulds, the metallic moulds can also be USED in the centrifugal casting process for large scale production. As inducing of high TEMPERATURE of metallic mould can be AVOIDED by water circulation through it and sticking problem can also be solved by casting of non-sticking materials.

Correct ANSWER is (b) Low-pressure die casting

The best explanation: Low-pressure die casting has been ADOPTED generally for the casting of aluminium and magnesium BASED alloys. Usually a permanent mould or sand moulds are also possible, but this method makes the casting totally free from shrinkage defects and also ENSURES proper SOLIDIFICATION naturally.

Right option is (b) Gravity die CASTING

For explanation I would say: As a simple shape of the casting can be produced by gravity die casting, so conventionally gravity die casting is best suited for casting connecting rods and PISTONS of the automobile. MANY other COMPONENTS like stators, gear blanks, aircraft FITTINGS etc. can also be produced easily by gravity die casting.

Correct answer is (B) False

For EXPLANATION: Not all materials can be casted easily by gravity DIE casting essentially because of the MOULD material. The problem of sticking arises due to the application of metallic mould; so much of lubricant is required, still cannot be suited for every metal. This casting method is APPLICABLE to some metals only.

Right ANSWER is (a) True

The best I can explain: In gravity die casting, a fined-grained casting with good SURFACE FINISH of the order of 4 microns can be produced. Close dimensional tolerances can also be obtained and with a better appearance of the casting. It is also economical for large scale production as the labour involved in the mould PREPARATION is reduced.

Right choice is (b) False

Explanation: It is true that water cooling results into higher EXTRACTION of heat from the castings, but its application arises some PROBLEMS. The likely problems with the cooling water circulation are the formation of scales INSIDE the cooling channels and their SUBSEQUENT blocking after some use. That’s why SOMETIMES water cooling is less preferred than the air cooling.

Right answer is (a) True

The best I can explain: The GATING and risering systems used in the permanent mould casting are very similar to that of the sand casting. In fact, to get the proper gating arrangement, it is desirable FIRST to experiment with various gating systems in sand casting and then finally ARRIVE at the correct gating system for the METALLIC mould.

The correct option is (B) Mueller

The best I can explain: Sand, hexa and additives, which are all dry, are mixed inside a Mueller for a period of 1 minute, then the liquid resin is added and mixing is done for another 3 minutes. Then by INTRODUCING COLD or warm air into the Mueller, mixing is continued till all the liquid is removed from the mixture and coating of the grains is achieved to the DESIRED degree.

Right answer is (a) True

The best explanation: The MOLTEN metal is poured into the MOULD in requisite quantity through a movable pouring basin. The thickness of the PIPE determined by the amount of metal poured into the mould. Then after the COMPLETION of pouring, mould is rotated at its operational speed till it solidifies to form the requisite TUBING.

Right option is (a) True

To elaborate: Low-pressure DIE casting METHOD is not economical for small-scale PRODUCTION because the dies and machines are very expensive, and the other parts like riser tube and the device used for compressing gas make the casting PROCESS very expensive. So the economy in production is possible only when LARGE quantities are produced.

Correct ANSWER is (b) False

Best explanation: The material does not get wasted in slush casting, instead this process saves a lot of molten METAL by collecting it and that is reused for the other slushing STEPS. This process makes the casting lighter in WEIGHT by saving the molten metal; HENCE this process is good in an economical way.

Right answer is (a) True

To ELABORATE: In Co2 moulding, moulds and cores of varied sizes and shapes can be formed, this is mainly ACHIEVED by the using of binder SODIUM silicate that can binds the sand in any SHAPE and size, and that is further tightened by the passing of Co2 gas. This makes the moulding PROCESS very fast and flexible, so this process is more economical, where speed and flexibility is the prime requirement.

Right answer is (c) Permanent mould casting

For EXPLANATION: Permanent mould casting is the only PROCESS that does not REQUIRE CORES to be used for hollow PROJECTIONS.

The correct option is (c) Air in the cavity

Easy explanation: The major problem with die casting is the air left in the cavity after closing of die. Since the air cannot escape out so it REMAINS inside the casting. This RESULT in the GENERATION of blisters, which basically appears on the surface of the castings, when the casting is heat treated. This problem can be solved by implementing a vacuum die casting method.

Correct CHOICE is (a) True

Best explanation: The operations in the CONTINUOUS CASTING cannot be done manually, so a higher extent of automation is introduced in this technique to perform the operations easily. For example, torch cutters, water sprayers, TUNDISH, metallic rollers etc. are the automatic devices which are USED to make the process fast and easy.

Correct answer is (a) True

To elaborate: At initial, a dummy STARTER bar is kept in the mould BOTTOM. After starting of a PROCESS, as the metal level rises to a desirable height then the starter bar is WITHDRAWN from the system. The initial metal freezes onto the starter bar as well as the periphery of the mould, and then this solidified shell supports the liquid metal as it moves DOWNWARDS.

Correct answer is (a) Pouring vessel

To EXPLAIN I WOULD say: Tundish is a REFRACTORY LINED intermediate pouring vessel.

Right choice is (a) True

To elaborate: In slush casting, it is not easy to CONTROL the internal geometry of the castings because when the MOULD is inverted some of the material remains sticks to the solidified WALL of the casting, which results into the FORMATION of IRREGULARITIES at the interior part of the casting, which then requires expensive machining.

The correct ANSWER is (a) True

For explanation: NORMALLY a slush CASTING is produced by pouring of molten metal into an OPEN top permanent mould and then the mould is inverted after the FORMING of a solid thin layer in the mould. The mould is reheated and the hollow casting is safely taken out from the mould for further processing.

Right option is (b) False

Explanation: Firstly the PATTERN is removed completely from the mould then the process of POURING of molten metal OCCURS in the investment casting. For the REMOVAL of pattern from the mould, HEATING is done to melt the pattern. Then the melted wax is completely drained through the sprue by inverting the mould.

Correct choice is (d) ZINC stearate

Easy explanation: Some lubricants such as zinc stearate and calcium stearate are added to the resin sand mixture to improve the flowability of the sand, which helps in COVERING of maximum part of the metallic PATTERN efficiently and ALSO permit easy release of the shell from the pattern.

Right CHOICE is (a) 0.3-1.5 bars

For EXPLANATION: USUALLY the gauge is set to a range of 0.3-1.5 bars while providing pressure to the molten metal to RAISE it in the riser.

Correct option is (b) False

Explanation: The squeeze CASTING has very low gas entrapment, lower shrinkage cavities, lower die costs, and very high quality of surface with fine details of CASTINGS. Also, it produces fine grain SIZE to IMPROVE the mechanical properties of the castings. Aluminum and copper alloys component can be manufactured easily by this method with high productivity.

Correct ANSWER is (b) 2 to 6 %

Best explanation: No other things like clay, water and resins are added to the sand except sodium silicate, which reacts with the sand MIX to increase the flow-ability to fill up corners and INTRICATE contours. Then the Co2 is supplied to the mould and reaction takes PLACE as follows:

Na2SiO3 + Co2—–>SiO2 + Na2Co3

Where, SiO2 is having gelling action (Silica gel).

Correct choice is (b) False

Best explanation: MOULD oscillation leads to a generation of shape defects of the casting. But the internal defects like blow holes, DIAGONAL CRACKS or any kind of cracks are originated in the cast product DUE to the mechanical and thermal stresses which are CAUSED by the non-uniform cooling of casting in the secondary zone.

Correct choice is (c) Chills

The explanation: When the heavy sections of casting are made then they are likely to interfere with the PROGRESSIVE solidification, this interference can be avoided by using chills SUPPORTED by heavy air blast to remove excess of heat. ALSO, the cooling channels can be provided at the necessary points to get PROPER temperature distribution.

Right OPTION is (b) False

Best explanation: In semi-centrifugal casting method, complicated but axi-symmetric shapes of casting can be possible to make and this is ACCOMPLISHED by POURING of molten METAL into the mould, which is rotated about a vertical axis. And the rotating speeds used in this process are not as high as in the case of true centrifugal casting.

The correct OPTION is (B) 10 to 25

Explanation: In CONTINUOUS casting process, the liquid steel is poured into a double-walled, bottomless water-cooled mould where a solid skin is formed quickly and a semi-finished skin emerges from the open mould bottom. The skin formed in the mould is APPROXIMATELY 10 to 25 mm in thickness.

Right option is (b) Way of pouring molten metal

Best explanation: Die CASTING is almost the same as permanent mould casting, in that both the processes use reusable METALLIC dies. Die casting involves the PREPARATION of components by injecting molten metal at high pressure into a metallic die; this way of pouring of molten metal distinguishes die casting from the permanent mould casting.