Explain welding Process ? Advantages and Disadvantages

Welding

               Welding is the process of joining similar or different metal by heating. welding can be done with or without the application of pressure. 

It can be done with or without the addition of filler metal.  

During welding, the edges of metal pieces are either melted or brought to plastic stage. 

welding gives a permanent joint. welding is used in the fabrication of automobile bodies, air craft, machine frames, boilers, ship building, railway wagons, etc. 

Types of welding

    The following are the two types of welding processes

              1)plastic welding or pressure welding,

              2)fusion welding or non pressure welding.

plastic welding or pressure welding

                  In this type of welding, the metal pieces are heated to plastic stage and joined by applying sufficient pressure.

           Example: electric resistance welding.

fusion welding

         In this type of welding, the metal pieces are melted and joined with the help of filler material without applying pressure.

            Example: electric arc welding, gas welding.

Arc welding

           Arc welding is the process of joining two work pieces by melting their edges by an melting their edges by an electric arc. 

    An electric arc is produced when there is a small air gap ( 2 to 4 mm ) between two conductors.

 The work piece acts as one conductor and the electrode acts as another conductor. 

when the current is passed, an electric arc having temperature 4000 celcius to 7000 celcius is produced between the work piece and electrode. 

The edges of work pieces and the electrode are melted by this high temperature.

              The melted metal pieces are joined together and cooled to give permanent joint.

 The electrode supplies additional filler material into the joint. the current is supplied by a transformer or generator.

Arc welding Equipment

    The following Equipment are needed for arc welding.

     

    1)welding generator 

    2)electrode holder

    3)electrode 

    4)welding cables 

     5)earthing cables

      6)protective shield

      7)gloves

      8)apron

      9)chipping hammer

      10)wire brush

Gas welding

          In gas welding, a gas flame is used for melting the edges of work piece to be joined. gas welding is a process of joining metals by the heat of the flame formed when oxygen burns with another gas. 

One of the gases used for producing another gas induces the burning of the inflammable gas. 

The temperature of flame produced by oxygen acetylene gases 3200 celcius. 

  

              The two gases are mixed at required proporation in the welding torch and flames is produced in the filler rod are torch the edges of pieces and the filler rod melted by the heat of the flux during welding work pieces having thickness  2mm to 50mm can be welded by using this method.

   The filler rod supplies the additional metal needed during gas welding. 

The filler rod is melted by the gas flame and weld is formed with the metal. the diameter of filler rod depends upon the thickness of work pieces. 

Generally the following gases are used to  the produce flame in gas welding.

    1)oxygen acetylene

    2)oxygen hydrogen

    3)air acetylene

Advantages

1) The flame temperature can be controlled Easily

2) The cost of welding equipment is less.

3) The maintenance cost is low.

4) Thin metal sheets can also be welded.

Disadvantages

1) It is a slow process.

2) It is not suitable for welding thick plates.

3) The strength of welded joint is less.