Introduction to Basic Manufacturing Processes and ... - always yours

114 Introduction to Basic Manufacturing Processes and Workshop Technology
a resistance pyrometer or a thermo couple. All the radiations are concentrated by concave
mirror upon the hot junction of a thermo couple. Mirror placed in inclined position is used
to indicate whether correct focus can be obtained.
6.10 POURING PRACTICES
Molten metal is collected in ladles from furnaces and skimmed properly before pouring into
the mould. Some of the pouring practices are shown in Fig 6.9.
6.10 QUESTIONS
1 What are the general principles of the melting practice?
2 What important factors are considered during melting?
3 What are the factors which govern the selection of a suitable type of furnace for melting a
particular metal?
4 What characteristics a refractory material should possess to make it suitable for use in
furnaces? How many types of refractory are there?
5 Sketch a blast furnace. Describe its construction and working.
6 Make a neat sketch of a cupola, indicating its various zones and describe the following:
(i) Construction
(ii) Preparation before operations
(iii) Charging method
(iv) Different zones and their functions
(v) Operation
(vi) Advantages
(vii) Limitations and
(viii) Application.
7 What do you mean by basic and acid cupolas? Where each type is preferred and why?
8 How is air requirement for cupola calculated
9 Why is the flux used during melting of metals in cupola?
10 How do you determine the thermal efficiency of a cupola furnace?
11 How will you specify a cupola furnace?
12 What necessary precautions are required in operating the cupola?
13 What are the expected gains in or losses of the various constituents of metal charge during
melting and how are these constituents controlled?
14 Why does a cupola sometimes get jammed up? How can it be prevented?
15 Explain with the help of neat sketches the construction and working of the following types
of crucible furnaces: (a) A coal fired pit furnace, (b) An oil fired tilting furnace, and (c) A gas
fired crucible furnace
16 What are crucible furnaces? Where are they preferred and why?
17 What are the different types of electric furnaces? Describe anyone of them.
18 Describe crucible furnaces.
19 Write short notes on the following:
(a) Open-hearth furnace and (b) Resistance furnace.