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Correct option is (C) 30-50%

For explanation I would SAY: In order to boost heat transfer by salvaging of castings, the average coating THICKNESS of metallic particles must be at least about 0.2 mm and less than about 0.4 mm. This metallic coating provides 30-50% improvement in heat transfer which forms the casting defects free and highly EFFICIENT.

The correct answer is (a) Hotspots

The best I can explain: Hot SPOTS are a type of metallurgical defect. Occurs due to the CHILLING of the casting.

Correct option is (c) Rolling

The best I can EXPLAIN: In salvaging TECHNIQUES, when a particular part has to be welded. Before the beginning of the WELD, the defective part has to be PREPARED for it. Chipping, grinding and gouging are a few types of doing it.

Correct answer is (B) False

The best explanation: In case of steel CASTINGS, the salvaging operation is PREFERRED as a cost of salvaging is much CHEAPER than the total conversion, while in case of grey cast iron castings, sometimes the salvaging operations are costlier than the conversion process. Salvaging is only preferred when it is economical for the castings.

Correct CHOICE is (a) True

To explain: Salvaging techniques, use the generated WASTE from casting processes in useful means by performing VARIOUS operations on it like, welding, BRAZING and so on. Welding operation for salvaging is most suited for high alloy steels and more to iron.

Correct CHOICE is (a) True

Best explanation: When approaching casting repair or salvaging, it is very important to know exactly which are the MATERIAL and the CONDITION of the object. By trying any welding or another PROCEDURE without sufficient PREVIOUS information about the casting, it may damage or destroy the whole casting.

The correct choice is (b) 175°F

The explanation is: SODIUM silicate is a TYPE of impregnant, USED for salvaging. The use of sodium silicate to immerse in the cast is termed as IMPREGNATION. The temperature at which this immersion should take place is between 175°F to 200°F.

Right answer is (a) True

Easy explanation: Salvaging is one of the most costs affecting constituent and an avoidable operation. Salvaging can be avoided if the casting process takes PLACE in the correct manner and ACCORDING to the design considered. The success of the PRODUCTION of castings is indirectly PROPORTIONAL to the EXTENT of salvaging carried out.

The correct answer is (a) True

Explanation: There is some sort of preparation required to the defective parts of the METAL before it is put for welding. When non-ferrous materials are to be PREPARED, filling serves as an option, before it is welded. Grinding is also ONE of the OPTIONS for preparing non-ferrous materials.

Correct option is (d) Gas turbine parts

The explanation: In salvaging of gas turbine castings, parts are EXPOSED to the one side where high-temperature fluid medium has cast-in bumps on an opposite cooling surface side to increase heat transfer RATE. This MAKES uniform cooling of the casted PRODUCT to have negligible defects in the casting.

Correct answer is (d) Oxy-hydrogen welding

The EXPLANATION: In CASTING processes, there are many occasions on which a LOT of material is wasted. Among the following, TIG welding, MIG welding and GAS welding, are a few METHODS used in salvaging welding.

Right choice is (d) 800°F

Explanation: The process of soldering is very much similar to that of brazing, EXCEPT for the temperature DIFFERENCE. In the soldering process, the SOLDER GETS melted, when the temperature goes below 800°F.

Right choice is (a) Thermal resistance

The EXPLANATION is: When FILLER metals are CONSIDERED, ONE has to be very careful while operating on it, as they play an important role in the weld characteristics. The thermal resistance has to be TAKEN into account, but not as much as chemical resistance or corrosion resistance or the appearance of it.

Correct CHOICE is (a) Swell

The explanation: Heavy metallostatic FORCES cause the mould wall to move back and result in an increment in dimensions if the casting. Good ramming techniques are USED to eliminate this defect.

Right CHOICE is (a) True

Best EXPLANATION: Despite the continuous technological GROWTH, a certain percentage of CASTINGS always possesses imperfections that further cause defects in the CASTING product. The salvaging is always carried out using electrodes, whose composition is more or less similar to the base composition of the casting.

Correct answer is (a) True

The explanation is: A coating containing particles such as metallic particles or its powder is APPLIED to the defective AREA. This sets in INTIMATE contact with the area and BRAZED by an electric arc wire sprayed thermal process. The selected SIZE of metallic particles depends on the provided heat transfer enhancement.

The correct ANSWER is (c) Casting yield

Easy explanation: The quality of production, PROTECTION of environment, SAFETY and protection of humans and machines in working conditions are integral part of management system. Integrated management system is the system which integrates management systems into ONE continuous system. Casting yield is another CONCEPT which does not considered in integrated management system.

Correct option is (B) False

For explanation: A COOLING MEDIUM like COOLANT air from the compressor or steam is commonly directed to the casting along one or more casting surfaces. This flow for cooling is considered as backside flow, where the cooling medium is not directly exposed to the high temperature of surfaces of the casting.

The correct option is (a) True

Easiest explanation: Electric arc wire SPRAY process normally used within the ranges of about 100-500 amps of electric current and an AIR PRESSURE of about 1.3-5.5 bar to ATOMIZE the molten wire metal and to propel droplets into contact with the defectively cast AREAS. And the atomizing air pressure is the only significant variable for controlling the surface layers of castings.

Right answer is (b) Welding

The best explanation: It is OBSERVED that, when the material which has been wasted, to be ABLE to bring it to USE, with the help of salvaging techniques, welding serves as the most APPROPRIATE operation than all others.

The correct answer is (b) False

The EXPLANATION: In electric arc wire SPRAY process, welding process is sought for casting repair or salvaging of a certain metal, the weld-ability of the casting metal should be GOOD ENOUGH to accomplish the salvaging process. But in the case of WHITE cast iron, it has no weld-ability that means it cannot be salvaged by having electric arc wire spray process.

Correct OPTION is (a) True

To ELABORATE: The decision for rejection or replacement of casting should be BASED upon not only the presence of defects in the casting itself but also on the significance in relation to the functioning or working of the casting PRODUCT. This makes salvaging of casting products more easy and efficient.

The correct option is (b) False

The best explanation: The surrounding has negligible affects on the castings. The defects are majorly caused by unsuitable raw MATERIALS USED in MOULDING, using improper tools, equipment, patterns. And SOMETIMES FAULTY organization and lack of training for the workers can also lead to the inducement of defects in the castings.

Correct option is (c) Visual inspection

Explanation: The surface areas of CASTING manifested by ONE or more partially cast bumps are first identified by visual inspection or sometimes by thermo-graphy. After identification, the areas are cleaned and the defective bumps are removed by the machining OPERATIONS LIKE grinding and grit blasting.

Right choice is (B) Run out

Best explanation: Run out is not a GAS defect, INSTEAD it is a moulding MATERIAL defect.

Correct CHOICE is (b) False

For explanation I would say: In the SALVAGING process, the metallic particles are always chosen to withstand the casting operating CONDITIONS while providing a high thermal conductivity that ENHANCES heat TRANSFER. The metallic particles must withstand the casting or part operating temperature while not diminishing other part properties.

The correct answer is (a) True

Easiest explanation: In salvaging of the casting metal, the weld-ability may depend on SPECIAL techniques. For example, preheating before welding is MAINLY done to prevent CRACKING due to thermal stresses and to reduce residual stresses, distortion and HARDNESS of the casting metal. This makes ELECTRIC arc wire spray process easy and reliable.

Correct ANSWER is (c) Silicon carbide

To explain I would SAY: Caulking and impregnation are one of the techniques used for salvaging defective castings. Among the following, linseed OIL, sodium silicate and SYNTHETIC resins are regularly used as IMPREGNANTS, but not sodium carbide.

Correct CHOICE is (b) 2 hours to 4 hours

Explanation: In impregnation TECHNIQUE of SALVAGING casts, the MATERIAL has to be kept immersed inside the sodium silicate solution at a temperature between 175°F to 200°F, for about 2 hours to 4 hours.

Correct OPTION is (b) False

Best explanation: It is very important to mention the correct qualifications of criterion USAGE of quality improvement tools. Separation of casting in parts takes PLACE to investigate all the spheres of formation easily and usage of products to make an ACCURATE INSPECTION, but it may increase the time for inspection of castings.

Right choice is (a) True

Easiest EXPLANATION: Sand inclusion is ONE of the most FREQUENT causes for rejection of casting. It is very difficult to diagnose, as this TYPE of defect normally occurs at varying positions in the casting which is caused by eroding of sand by a metal stream and then float to the surface of the casting. So it is not easy to ATTRIBUTE to a local cause.