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8/4/2019 Work Shop Pratice - My
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WORK SHOP PRATICE
ME/MT/CH/RE 1962 – SKILL
DEVELOPMENT
A H VITHANAGE
100560P
CHEMICAL AND PROCESS ENGINEERING
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Practical 1 : Machining of Thread and Taper
Machining processes used in the practical are as follows
1. Facing
2. Drilling
3. Taper Turning
4. Threading
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Practical 2 : Welding
Shielded Metal Arc Welding (SMAW)
Shielded Metal Arc Welding uses a consumable electrode coated in flux
(flux – potash, charcoal, coke, borax, lime, lead sulfide and etc) to lay the weld. Electric current
from the welding power supply, is used to form an electric arc between the electrode and the
metal to be joined. As the weld is laid, the flux coating of the electrode vaporizes and then
becomes a layer of slag, which protects the weld area from atmosphere.
Because of the simplicity of both its process and equipment, shielded
metal arc welding is one of the most popular of various welding processes. Although there are
new welding methods being developed, shield metal arc welding continues to be used
extensively in the construction of steel structures and in industrial fabrication. This welding
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process is used primarily to weld iron and steels, but aluminium, nickel and copper alloys can
also be welded with this method.
Purposes of the coating of the electrode used in shielded metal arc welding
Gives off gases as it decomposes to prevent weld contamination
Introduces deoxidizers to purify the weld
Causes weld-protecting slag to form
Improves the arc stability
Provides alloying elements to improve the weld quality
Oxy-Fuel Gas Welding
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Oxygen-acetylene welding was developed by two French engineers in
1903. In oxy-fuel gas welding fuel gases and oxygen is used to weld metals. Apart from welding
this method can also be used to cut metals too. Pure oxygen is used to increase the flame
temperature to allow localized melting of the material (e. g. steel) in a room environment. A
common propane/air flame burns at about 3,630 °F (2,000 °C), a propane/oxygen flame burns at
about 4,530 °F(2,500 °C), and an acetylene/oxygen flame burns at about 6,330 °F (3,500 °C).
In oxy-fuel welding, a welding torch is used to weld metals. Welding
happens when the two pieces of metals are heated to a temperature that produces a shared pool of
molten metal. The molten pool is generally supplied with additional metal called filler. Filler
material depends upon the metals to be welded.
Resistance Spot Welding
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Resistance spot welding is a process in which contacting metal surfaces
are joined by the heat obtained from resistance to electric current flow. Work-pieces are held
together under pressure exerted by electrodes. Normally the sheets are in the 0.5 to 3 mm (0.020
to 0.12 in) thickness range. The process uses two shaped copper alloy electrodes to concentrate
welding current into a small "spot" and to simultaneously clamp the sheets together. Forcing a
large current through the spot will melt the metal and form the weld. As the huge energy is
delivered to the spot in a very short time, welding occurs without excessive heating to the rest of
the sheet.
It is used in a wide range of industries but notably for the assembly of
sheet steel vehicle bodies where more than 100 million welds are made per day in Europe alone.
High quality welds can also be made in stainless steels, nickel alloys, aluminium alloys and
titanium for aerospace application.
Practical 3 : Sheet Metal Forming
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Industrial applications of sheet metal
1. In Airplane wings
2. For vehicle bodies
3. For conductor pipes and gutters
4. Used in the making of air conditioners to provide the self-contained unit for the
refrigeration system
5. For tables and storage units
6. Manufacturing of toys
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Practical 4 : Wood Work