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Chapter: Mechanical : Manufacturing Technology : Metal Joining Process

Arc welding

Arc welding
Uses an electric arc to coalesce metals, Arc welding is the most common method of welding metals, Electricity travels from electrode to base metal to ground.



Uses an electric arc to coalesce metals

Arc welding is the most common method of welding metals


Electricity travels from electrode to base metal to ground



1.Arc welding Equipments

• A welding generator (D.C.) or Transformer (A.C.)


      Two cables- one for work and one for electrode


     Electrode holder




     Protective shield




     Wire brush


     Chipping hammer







Electrode is a thin rod made up of same as that of parent material. Flux is coated over the electrode to avoid oxidation. It is mostly connected to the negative polarity.


Two Basic Types of AW Electrodes

Consumable  consumed during welding process Source of filler metal in arc welding


Nonconsumable  not consumed during welding process


Filler metal must be added separately


Consumable Electrodes

Forms of consumable electrodes


        Welding rods (a.k.a. sticks) are 9 to 18 inches and 3/8 inch or less in diameter and must be changed frequently


        Weld  wire  can  be  continuously  fed  from  spools  with  long

lengths  of  wire, avoiding frequent interruptions


In both rod and wire forms, electrode is consumed by arc and added to weld joint as filler metal.


Nonconsumable Electrodes

Made of tungsten which resists melting


Gradually depleted during welding (vaporization is principal mechanism) Any filler metal must be supplied by a separate wire fed into weld pool




A substance that prevents formation of oxides and other contaminants in welding, or dissolves them and facilitates removal


Provides protective atmosphere for welding Stabilizes arc


Reduces spattering





      Prepare the edges to be joined and maintain the proper position


      Open the acetylene valve and ignite the gas at tip of the torch


      Hold the torch at about 45deg to the work piece plane


      Inner flame near the work piece and filler rod at about 30  40 deg


        Touch filler rod at the joint and control the movement according to

the flow  of the material



Most efficient way to join metals


Lowest-cost joining method


Affords lighter weight through better utilization  of materials


Joins all commercial metals


Provides design flexibility



•  Manually applied, therefore high labor cost.


      Need high energy causing danger


      Not convenient for disassembly.


      Defects are hard to detect at joints.



Difference between Gas Welding and Arc Welding





1. Heat is produced by the Gas Flame

2. The Flame temperature is about 3200oC

3. Separate Filler rod introduced

4. Suggested  for thin materials

5. Gas welded parts do not have much strength

6. Filler metal may not be the same parent metal

7. Brazing and soldering are  done using gas





1. Heat is produced by Electric Arc

2. The temperature of Arc is about 4000oC

3. Arc Producing as well as filler rod material is the  electrode.

4. Suggested for medium and thick materials

5. Arc welded parts have very high strength

6. Filler metal must be same or an alloy of the parent  metal

7. Brazing and soldering can’t be carried out by electric arc.


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Mechanical : Manufacturing Technology : Metal Joining Process : Arc welding |

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