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Arc Welding

    Electric arc welding is a modern and efficient welding technology that is widely used in various industries to permanently join metal pieces. This type of welding is achieved by generating high heat through the electric arc that forms between the electrode and the metal to be welded.

    arc welding
    arc welding

    An electric arc is the passage of electrical charges through a gap between conductors. This arc reaches a temperature of up to 5000 degrees Celsius, which is sufficient to melt metals such as iron and its alloys.

    basic-arc-welding-circuit-diagram
    basic-arc-welding-circuit-diagram

    he arc welding process involves the use of a molten metal electrode that is fed through the arc to fill the space between the pieces to be welded. It is important that the electrode metal is similar to the metal to be welded to ensure compatibility and quality in the weld. To increase the efficiency of the welding process and protect the molten pool from oxidation by air, the electrode is covered with an insulating layer that melts during the welding process, generating an amount of gases that cover and protect the molten pool.

    arc-welding-electrodes
    arc-welding-electrodes

    For an electric arc we need a high-Amperage current and get it  by the transformer 

    ac-welding-machine
    ac-welding-machine

    The transformer is a device that transmits electrical energy between two or more circuits by electromagnetic induction, consisting of two winded wires that surround an iron core. The primary coil passes through alternating current. A variable magnetic field is generated in the core. This field generates a variable electric current in the secondary coil according to Faraday’s law In electrical induction

    transformer
    transformer

    Given the following relationship
    Vp / Vs = Np / Ns
    Ip / Is = Ns / producer
    where:
    Vp voltage on the primary coil “Volts”
    Vs voltage on the secondary coil “Volts”
    Np number of winds the primary coil 
    Ns number of winds in secondary coil
    Ip current in the primary coil “Amperes “
    Is  current in secondary coil “Amp”

    Types of arc welding:

    • Metal arc welding (SMAW): It is based on the use of a metal electrode covered with an insulating layer. This type of welding is considered one of the most common and can be used in a variety of applications.
    • Gas arc welding (GMAW): A shielding gas is used with the electrode to protect the molten metal from oxidation. This type of welding is also known as MIG (Metal Inert Gas) welding.
    • Fill gas arc welding (FCAW): An electrode containing metal powder is used with a shielding gas to produce an electric arc. This type of welding can be used in wet and windy conditions.
    • Carbon arc welding (CAC-A): It uses a metal electrode covered with an insulating layer containing carbon materials. This type of welding is used to repair cast iron and other metals.

    Types of electrodes:

    • Hard electrodes (HARD): These electrodes are used for welding in the horizontal position, which requires the addition of additional metal to the weld.
    • Alkaline electrodes (BASIC): These electrodes are used in vertical and horizontal welding. They contain metal powder that increases welding efficiency.
    • Ceramic electrodes (CELLULOSE): They are suitable for vertical welding and welding in difficult locations, and they contain an insulating layer of cellulose materials.
    • Neutral Electrodes: Used in a variety of applications and do not require the addition of additional metal to the weld.

    Arc welding methods:

    • Root Pass Welding: Here the internal part of the connection between the metal pieces is welded.
    • Filler Pass welding: Here the root is completed by adding more molten metal to fill the space between the pieces.
    • Cover Pass Welding: Here the outer layer of the connection is welded to provide additional protection and make the weld more tolerant to the environment.
    • Back Gouging: Used to remove excess metal and prepare the surface for welding.
    • Preheating and Postheating Welding: These processes are used to control temperature to avoid cracks and ensure weld quality.

    In conclusion, electric arc welding represents an important technology in the field of metallurgy and construction industries, and knowledge of welding types, types of electrodes, and welding methods is essential to ensure the quality of work and the safety of metal structures.

    Resourses : https://www.millerwelds.com/resources/welding-guides

    Khaled Saleh

    Khaled Saleh