Do you fear in welding? Don’t worry, it is nothing. It is the process
of inter molecular bonding of two similar or dissimilar metals by
heating and brings its melting point temperature, in this condition
the external pressure may or may not be used, or third metal viz
filler rod may or may not be used. The heating is produced by electric
arc, oxy-acetylene flame or oxy-hydrogen flame etc. where the metal’s
end portion to be weld. The basic requirement of welding is i) heat
energy, ii) cleaning the edge before the welding, iii) atmospheric
contamination, iv) weld metal properties, v) application of pressure.
Heat: During welding it should required sufficient amount of heat for
fusion. Otherwise the joint may produced incomplete fusion.
Cleaning: Cleaning the welding edges should be properly maintained.
Because the unwanted materials are may be damaged the welding joints.
The unwanted materials are- oxides, nitrides, oil, grease, dirt, sand
etc. These should be properly cleaned by either mechanically or
chemically.
Atmospheric contamination: The main atmospheric contamination is
nitrogen, oxygen and humidity. During welding flux, various inert gas
or other types of gas should be used, which may helps to avoid the
reaction with these contamination.
Welding metal properties: It is very important for obtaining the
cleanness weld joint. These processes are which can be controlled with
successfully- i) de-oxidizers used during welding, ii) to mixing up
the alloy in filler rod, iii) by the controlling of base metal
composition, iv) by the post weld heat treatment.
Application of pressure: In few welding process the sufficient amount
of pressure is required for weld joint. This pressure may be obtained
from mechanically, pneumatically or hydraulically.
Advantages of welding: a) Similar or dissimilar metals can be joining.
b) The joint can produce same or more strength than base metals. c)
The welding machine portability is the good advantage for anywhere
welding. d) The welding can easily performed in very big size like
structure under budget. e) The welding is the only one process which
can make joint the broken parts easily. f) It has extra facility that
the joint can performed under water.
Disadvantages of welding: a) Highly trained persons are required for
good welding. b) Initially investment cost is very high. c) During
welding the metallic structure of base metal may be changed for high
temperature. d) Often heat treatment may require after welding
process. e) In welding the edge preparation should required, so more
than one man power is required. f) The welding equipments handling
required with carefully. g) The welder should have sufficient
knowledge about general electric. h) The very dangerous ultraviolet
ray and fumes are produced, so safety should be taken properly.
Classification of welding: There are different types of welding
process are classified into two main groups. One is fusion and another
is pressure welding. The fusion welding are sub-classified in gas
welding, thermit welding, metal arc welding, carbon arc welding,
atomic hydrogen welding, TIG welding, MIG welding. The pressure
welding are forge welding, spot welding, seam welding, butt welding,
flash welding.
The general condition of welding: The welding joint will be easy if
the weld joint portion is cleaned by wire brush or machining or sand
blasting. By these processes the unwanted materials or impurity is
cleaned properly. If these impurity presences in weld pull then it may
be weakened the joint by inclusion. So the quality joint is cannot be
made. The oxidation rate is directly proportional to temperature. Most
welding process performed in high temperature and that time the
oxidation acting as a weakening agent in weld metal. This is prevented
by the using of fluxes and makes a strong weld joint. In manual
welding process the flux is covered on the electrode. This flux is
melted in high temperature and covered on the weld metal. Then it
creates an artificial anti oxidation gaseous covered on weld metal.
Powder type flux is used in gas and forged welding. In other welding
process there are used non oxidation gaseous components like Argon,
Helium etc. which covered on the weld metal and prevent the oxidation.
Industrial application of welding: Today the welding process is very
easy because the machines are much modernized. So the weld joint can
be performed in any position. It has very much application in workshop
to fabricate the small/big structure, repair and maintenance of
various components. In fabrication work there various type angle,
channel or beam is used to make a structure. There may be used the nut
bolt to join together, but it is less strong than welding. The
structure can be made by casting. But this process is very expensive.
In other way the welding process is less expensive, labor cost and
easy. Due to this causes the welding is very popular in fabrication
industry.
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