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Right choice is (b) False

The best explanation: Core WIRES and rods are meant for small or slender cores which do not have sufficient STRENGTH to bear the LOAD and pressure of molten metal during the pouring operation. So these types of cores are supported by embedding the wires and rods into the core PARTS which are called as core wires.

The correct option is (b) False

Explanation: In dielectric core BAKER systems, a dielectric material is used that should have a high value of K (K is the dielectric constant of the material), which basically provides the REQUIRED electrical properties to operate the SYSTEM efficiently. More the value of K, then more will be the EFFECT of baker system on the BAKING cores.

Right CHOICE is (c) LESS than 0.5%

The EXPLANATION is: In furan-no-bake SYSTEM, there is very less amount of clay content present in it. The cores and mixture are found to CONTAIN less than 0.5% of clay.

Correct choice is (b) 375°F – 450°F

To ELABORATE: 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.

Right option is (b) False

To explain: In the injection moulding process, alloy cores are used in the moulding box instead of any sand cores. In the process, the plastic is getting injected into the moulding box and then after solidification, the casted POLYMER is TAKEN out from the moulding box with the cores still in it. And then the core is MELTED and washed out from the moulding box.

Right option is (C) After molten metal is poured

The best explanation: Chaplet becomes a PART of CASTING by melting. Chaplet melts and becomes a part of it. Chaplets are a type of metal shape which are positioned between MOLD and core SURFACE.

Correct answer is (a) True

Easy explanation: The main advantage of dielectric core BAKER is that they are very FASTER in operation and have good control of maintaining the temperature. After baking of cores in dielectric baker, they are further smoothened by using dextrin material, SOMETIMES water soluble binders are ALSO used for this purpose.

Correct answer is (B) Small sized-limited production

The best I can explain: Small sized cores are made manually in the hand FILLED core boxes. For MAKING large sized PRODUCTS for mass production, these cores cannot be employed.

The CORRECT answer is (b) False

To explain: For the removal of cores from the MOULDING box, several methods can be used. But for low cost and minimizing the CASTING erosion, a caustic bath is used which is also known as mechanical agitation. In this method, a solution of sodium or potassium hydroxide is used for the breaking of a CORE material. But this method CONSUMES too much time for processing the large and complex cores.

The correct answer is (c) Cores are PERMANENT & semi-permanent

For EXPLANATION I would say: Cores can be permanent and SOMETIMES they can also be semi-permanent and are destroyed in order to remove the CASTING from MOLD.

The correct choice is (a) Mold CAVITY

Explanation: The material in PLACE of the question MARK is a mold cavity. INSIDE this mold cavity, there some place into which, while operating, the mold is kept.

The correct option is (b) False

Explanation: GREEN sand cores are generally preferred for simple, small and medium castings. The process of making green sand cores do not consume much of TIME. The process is ACCOMPLISHED quickly that causes less strength in green sand cores as compared to that of DRY sand cores. Dry sand cores usually take longer time in making of themselves.

The CORRECT option is (B) RAM up core

Easiest explanation: Ram up core cannot be classified under the type of core HARDENING PROCESS employed, while the remaining can be classified under it.

The correct choice is (a) True

Easy explanation: In dielectric baker systems, the HEATING of core is done by placing them in the electrostatic field. The dielectric material generates heat in the system that is DIRECTLY supplied to the CORES. In this system, there should be no interruption of any metallic material, so cement plates are WIDELY used instead of metallic plates in the baking system for supporting the cores.

Correct option is (b) False

The best explanation: After baking of cores in dielectric CORE bakers, FINISHING operation is a must before they set in the moulding box. Finishing is the last process which completes the formation of a core. This is a process in which bumps or other sand projections are REMOVED from the surfaces of cores by FILING them in a FIXTURE.

The CORRECT answer is (B) USED to create cores

To EXPLAIN: Core boxes are those elements or tools which are used to create cores.

Correct option is (c) c

The best I can explain: A CORE is that element which is USED in moulding processes to make hollow cavities or holes or to give SPECIAL CONTOURS on the casting which are difficult or expensive to be machined.

Right choice is (a) RADIATOR chaplet

Explanation: The following FIGURE represents a radiator chaplet. This PARTICULAR chaplet holds a very important duty, WHEREIN it helps the cores by SUPPORTING them.

The correct choice is (a) Completely true

To explain I would say: Due to the DIRECT pouring of MOLTEN metal (of ELEVATED temperature) the cores are subjected to severe thermal and mechanical conditions and PROPER steps must be taken to avoid pattern or mold spoliation.

Correct choice is (B) HOT air

The explanation: On a rack type CORE OVEN, for proper baking of the core, hot air is circulated over the cores. Odourless air or COMPRESSED air or cool air cannot be of much help here.

Correct answer is (b) BAKING

The best I can explain: Baking is a PROCESS that takes PLACE after quite a lot of preliminary operations. After the cores are prepared, the cores are then placed on the plates and moved forward for baking.

Correct answer is (a) 5%

The explanation: Green SAND cores are made of green sand which mainly contains water or moisture nearly about 5% and 15 to 30 % of clay. It IMPARTS very high permeability to the core material and hence reduces the chance of defects such as shrinkage or voids in the casted parts. Green sand cores are not dried but usually baked by dielectric bakers to maintain the moist content.

Right answer is (a) Core OVENS

Explanation: Core ovens are the equipment which can be used for the making of limited productions. It is also a good CHOICE if the PRODUCTION is going to be a MASS one.

Right CHOICE is (c) Left and right hand core boxes

For EXPLANATION: The following FIGURE represents two core boxes, in which one is facing to the right, while the other is facing is towards the left. HENCE, it DEPICTS left and right hand core boxes.

Right answer is (a) True

The EXPLANATION: Chaplets design should be OPTIMIZED because if they are too small they will melt completely and will make the core to move, but if they are too big then their whole part will not melt and fuse with the poured molten metal. So, USE of chaplets must also be minimized because they MAY cause defects or PRODUCE a weak point in the casting components.

Correct answer is (b) False

For explanation: The CORE prints are mainly PROVIDED on the mould so that the cores are SECURELY positioned in the mould cavity. The design of the core print is made in such a WAY to take care of the weight of the core while pouring of molten metal; it also ensures that the core is not shifted during the ENTRY of molten metal into the mould cavity.

The correct answer is (b) False

The explanation is: Dry sand cores are basically produced by HEATING the green sand cores nearly about 110 ⁰C. These cores have high strength rigidity and excellent thermal STABILITY. These cores can be easily baked by dielectric CORE bakers and NORMALLY stored for a long period of TIME to make them more stable than the green sand cores. Dry sand cores generally used for large castings production.

Correct ANSWER is (B) 2%

For explanation: In Nishiyama PROCESS, 2% of finely powered FERROSILICON is made to mix with SODIUM silicon bonded sand to ensure that hardening occurs.

Right choice is (d) SODIUM CARBONATE

The explanation is: When sodium SILICATE is made to react with carbon dioxide gas, it is known to YIELD sodium carbonate and silica GEL.

The correct option is (a) Cores

The explanation: Core has a variety of USES. For the making of long PASSAGEWAYS in a casting core a best SUITABLE and CHEAP.

The CORRECT answer is (b) False

For EXPLANATION I would say: BIG cores are set up quite easily with the help of CRANES, WHEREAS when small cores are to be set up, they are set in molds using a hand.

Correct answer is (c) BUOYANT FORCE

Explanation: The force EXPERIENCED by the cores inside the molds is a buoyant force, which is the UPWARD force EXERTED by a fluid. This force is available due to poured molten metal.

Correct choice is (c) Shell core

The explanation is: 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.

Right CHOICE is (C) Oil bonded cores

Explanation: Oil bonded cores are produced by adding SILICA and a small AMOUNT of LINSEED oil, and then polymerized.

The correct choice is (a) DRY SAND core

Easy 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.

Correct option is (b) Dump CORE box

Best EXPLANATION: The given figure REPRESENTS a dump core box which is used for making rectangular or trapezoidal cores.

Right ANSWER is (a) True

The explanation: In the production of very COMPLEX shapes of castings, GREEN sand cores are not compatible as they are made of low STRENGTH and cannot bear forces for a long period of TIME. So generally, dry sand cores are commonly used for producing complex shapes of castings instead of green sand cores.

Correct answer is (a) True

To explain I would say: Cores are generally coated with refractory or protective materials by PERFORMING several operations like BRUSHING, dipping and spraying, which greatly improves the REFRACTORINESS and SURFACE finish of the cores. The coating material on cores also RESTRICTS the liquid metal from entering into the pores of a core.

The CORRECT OPTION is (c) Three

The best explanation: Core PRINTS or core seats are used for the location of a core. For this, an amount of three core prints or core seats are enough to properly locate a core.

Right OPTION is (C) 400°F – 500°F

To explain I would say: Whenever any material is heated to a temperature HIGH for its PROPERTIES, there is a change in its chemical and physical aspects seen. Core oils and organic binders USED in backing the core, change their physical properties at 400°F – 500°F.