Engineering Workshop Production Welding Concepts

Electric Arc Welding Process:Principle,Arc Welding Equipment,Applications

Electric Arc Welding Process: By using Electric Arc, If the heat required for melting of plates is obtained, called as Electric Arc Welding Process.

The fusion of metals by an electric arc is one of the most important processes in industry. This is commonly called arc welding or SMAW (Shielded Metal Arc Welding).

Applications:

Arc welding is mostly used in the manufacturing and construction industries.

EX: Pipe Welding, Metal Joining for rotary Kilns etc.

This post focuses on the detailed explanation of the Electric Arc Welding Process with its principle, Arc Welding Equipment etc. in a detailed way.

Electric Arc Welding Process-Equipment:

The Electric Arc Welding Process Equipment generally consists of the following parts:

  1. Arc welding power source
  2. Welding Electrodes
  3. Welding cables
  4. Electrode holder
  5. Wire brush
  6. Chipping Hammer
  7. Wire brush
  8. Protective clothing
Electric Arc Welding Process:Principle,Arc Welding Equipment,Coated Electrode
Electric Arc Welding Process: Principle, Arc Welding Equipment, Coated Electrode

1.Arc welding power source:

  • Both direct current (DC) and alternating current (AC) are used for electric arc welding, each having its particular applications.
  • For AC welding supply, transformers are predominantly used for almost all Arc welding processes
  • DC welding supply is usually obtained from generators driven by the electric motors
  • They have to step down the usual supply voltage (200-400 volts) to the normally open circuit welding voltage (50-90 volts) by means of Step-down Transformer.

2.Electrode holder:

  • Electrode holder is used for holding the electrode manually.

3.Welding Electrodes

  • An electrode is a piece of wire or a rod of a metal or alloy, with or without coatings. 
  • An Electrode can generate the arc at the desired welded location between electrode and workpiece.

4.Welding cables    

  • Welding cables are required for conduction of current from the power source to various parts of Arc welding process equipment i.e.electrode, the arc, the workpiece and back to the welding power source.
  • These are insulated copper or aluminum cables.

5.Hand Screen

  • Hand screen is used for the protection of eyes during Arc welding process.

6.Chipping hammer

  • It is used for striking the slag from the weld bead region.

7.Wire brush

  • A wire brush is generally used to clean the surface before and after the welding process.

8.Protective clothing

  • The operator wears the protective clothing such as apron to keep away from the exposure of direct heat to the body.
  • Always wear Gloves before touching any item in the workshop.

Electric Arc Welding Process-Principle:

  • The work to be welded is connected to one side of an electric circuit(Anode), and a metal electrode is connected to the other side(Cathode).
  • When the power supply is given and the optimum gap is maintained between Cathode and Anode, the very high velocity negatively charged electrons will be generated at the cathode.
  • These will be attracted by the anode and moving towards the anode. When these very high velocity negatively charged electrons are impinging on to the anode, the Kinetic Energy of electrons is converted into Heat energy. 
    • Therefore, the heat generation is taking place at the anode. 
    • Simultaneously, the Positively charged ions also will be generated at the anode which is attracted by the cathode and moving towards the cathode.
    • When these high-velocity ions impinging on to the cathode, the Kinetic Energy of ions is converted into Heat energy.
    • Therefore, heat generation is taking place at cathode also.

    The ratio of Heat generation between the cathode and anode is given as follows.

              Heat Generation of Cathode:Anode=2:1

Spark Zone in Electric Arc Welding process:

  • During the flow of electrons and ions, some of them may get collided in between the path so that the Kinetic Energy possessed by both the elements is converted into heat energy.
  • This spontaneous release of heat energy will induce the sparkling and in the spark zone, the temperatures induced are very high which is about 5000°C-6000°C.
  • This high-temperature zone will produce UV rays. Hence the Electric Arc Welding process Zone must be seen only through safety goggles to safeguard the human eye.

Abbreviations in the Electric Arc Welding Process:

  • DCSP-Direct Current Straight Polarity
  • DCEN-Direct Current Electrode Negative
  • DCRP-Direct Current Reverse Polarity
  • DCEP-Direct Current Electrode Positive
  • ACHF-Alternating Current High Frequency
Features of Electric Arc Welding Process:
  • In DCSP, because of higher heat generated at the workpiece, high Melting Point metals and higher thickness plates can be welded very easily and depth of penetration is also higher.
  • Because of lower heat generated at the electrode, melting rate of the electrode is low, deposition is low hence welding speeds are possible.
  • In DCRP, because of lower heat generated at the workpiece, only low Melting Point metals and lower thickness plates can be joined and depth of penetration is also low.
  • Whereas in the case of the electrode, because of the higher heat generated at the electrode, the melting rate of the electrode is high, the deposition rate is high. Hence higher welding speeds are possible.
  • In ACHF, heat generation is 1:1 ratio. Hence, this can be used for medium conditions and depth of penetration is also medium.

This is the complete explanation of the Electric Arc Welding Process in a detailed way.

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