Page 156 - CITS - Welder - Trade Theory

WELDER - CITS

c maintain good ventilation in the weld area
d repair or replace damaged power cables
e make sure the part to be welded is securely grounded/ earthed

f welding helmets should have no light leaks. Should not have scratches or cracks
g use the proper coloured lens with correct shade number in the helmet
h wear safety glasses when grinding
i do not see the arc with bare eyes
j use safety screens or shields to protect your area

h wear proper clothing. Your entire body should be covered to protect you from arc radiation

Introduction to CO welding - equipments - accessories,
2
Description of CO welding set with diagram
2
Objectives: At the end of this lesson you shall be able to
• describe the CO2 welding power source
• explain the CO2 welding CO2 wire feeder
• explain the CO2 welding gun.

Introduction to CO welding: Fusion welding of metal plates and sheets is the best method of joining metals
2
because in this process the welded joint will possess the same properties and strength as the base metal.
• Without a perfectly shielded arc and molten puddle, the atmospheric oxygen and nitrogen will get absorbed
by the molten metal. This will result in weak and porous welds.
• In shielded metal arc welding (SMAW) the arc and molten metal are protected/shielded by the gases
produced by the burning of the flux coated on the electrode.

The above mentioned shielding action can be done by passing an inert gas such as argon, helium, carbon-di-
oxide through the welding torch/gun. The arc is produced between the base metal and a bare wire consumable
electrode fed continuously through the torch.
Basic equipment for a typical GMAW semiautomatic setup: (Fig 1)
• Welding Power Source - provides welding power.
• Wire Feeders - controls supply of wire to welding gun.

• Supply of Electrode Wire.
• Welding Gun - delivers electrode wire and shielding gas to the weld puddle.
• Shielding Gas Cylinder - provides a supply of shielding gas to the arc.
Other names
• MIG (Metal Insert Gas) welding,

• MAG (Metal Active Gas)/CO2 Welding
• GMAW (Gas Metal Arc Welding)
GMAW can be done in three different ways:
• Semiautomatic welding - equipment controls only the electrode wire feeding. Movement of welding gun is
controlled by hand. This may be called hand-held weld-ing.
Machine welding - uses a gun that is connected to a manipulator of some kind (not hand-held). An operator has
to constantly set and adjust controls that move the manipulator.

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CITS : C G & M - Welder - Lesson 49 - 60