Casting Questions and Answers – Salvaging Techniques – 2

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This set of Casting Questions & Answers for Exams focuses on “Salvaging Techniques – 2”.

1. Which of the following parts of castings are mostly salvaged with defective cast cooling bumps?
a) Piston
b) Cylinder
c) Connecting rods
d) Gas turbine parts
View Answer

Answer: d
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.
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2. In salvaging of castings, cooling fluid used can be directly exposed to the hot castings to enhance heat transfer.
a) True
b) False
View Answer

Answer: b
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.

3. A metallic powder is basically used as a coating for the heat transfer enhancement.
a) True
b) False
View Answer

Answer: a
Explanation: 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.

4. Which of the following types of inspection is mostly used for the identification of cast bumps on the castings?
a) Radiography
b) Eddy current method
c) Visual inspection
d) Dimensional inspection
View Answer

Answer: c
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.

5. In salvaging process, the metallic particles used for enhancing heat transfer may stick to the surface areas of casting by melting itself.
a) True
b) False
View Answer

Answer: b
Explanation: 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.
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6. In electric arc wire spray process, the atomizing air pressure is the only significant variable for controlling the surface layers.
a) True
b) False
View Answer

Answer: a
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.

7. In salvaging of castings, the metallic powder coating can improve the heat transfer by_____
a) 5-10%
b) 10-30%
c) 30-50%
d) 100%
View Answer

Answer: c
Explanation: 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.

8. Without knowing the conditions or details about the castings, salvaging can even destroy or damage the whole casting.
a) True
b) False
View Answer

Answer: a
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.

9. By using electric arc wire spray process, salvaging of white cast iron becomes very easy.
a) True
b) False
View Answer

Answer: b
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.
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10. In electric arc wire spray process, preheating of metal before welding is mainly done to prevent surface cracking.
a) True
b) False
View Answer

Answer: a
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.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn