Manual Metal Arc Welding
Overview: Perhaps the most primitive of welding processes, this process involves a metal rod with flux coating to give a protective gas shield. When an arc is struck between the metal rod (electrode) and the work piece, both the rod and work piece surface melt to form a weld pool. Simultaneous melting of the flux coating on the rod forms gas and slag which protects the weld pool from the surrounding atmosphere. The slag solidifies and cools and must be chipped off the weld bead once the weld run is complete (or before the next weld pass is deposited).
Overview: Perhaps the most primitive of welding processes, this process involves a metal rod with flux coating to give a protective gas shield. When an arc is struck between the metal rod (electrode) and the work piece, both the rod and work piece surface melt to form a weld pool. Simultaneous melting of the flux coating on the rod forms gas and slag which protects the weld pool from the surrounding atmosphere. The slag solidifies and cools and must be chipped off the weld bead once the weld run is complete (or before the next weld pass is deposited).
The process allows only short lengths of weld to be produced before a new electrode needs to be inserted in the holder. Weld penetration is low and the quality of the weld deposit is highly dependent on the skill of the welder.
Applications of MMA Welding: Due to the simplicity of apparatus, this process is widely used for welding applications in difficult locations, like at heights or where the joint is in abnormal welding position. This process is normally used where the weld metal deposition is less than 20Kg. If the deposition is more than 20 Kg, MMA will be used only if automated processes like MIG / SAW cannot be utilized.
Hazards in MMA Welding: The following hazards are common for MMA process:
a) Welders’ Eye or Arc Eye: This normally happens dues to accidental or inadvertent eye contact with the welding arc. Operators & people in close vicinity of the weld process must wear suitable glasses to safeguard from this hazard.
b) Fumes: The flux coating on the electrodes create gas fumes that protect the weld pool from environmental hydrogen. However these fumes are harmful to the health of the welder. Sufficient air draft has to be provided such that while the fumes protect the weld pool, they do not come in the respiratory zone of the welder.
c) Electric Shock: This may be caused due to improper welding cable connections, improper grounding of workpiece, damaged insulations of power cables etc. thw welder has to check for these points, every time he starts a fresh job, to safeguard against this hazard.
d) Burns: This happens due to contact with hot metal surfaces, contact with flying weld spatters, contact with molten slag etc. Welders must use appropriate clothing, gloves & guards so as to prevent burn injuries.
e) Fire: Since the process involves a naked arc & flying spatters, a danger of fire is always present. There shall be no flammable articles near the welding process. Also the welder has to be cautious enough to see where the spatters & electrode stubs are falling so as to prevent occurrence of a fire.
f) Fall: When working at heights, the falling hazard is eminent. Relevant fall arrestors have to be worn, if proper platform cannot be provided.
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