Manual ARC Welding (MMA Welding)
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Manual arc welding is an arc welding method that uses manually operated electrodes for MMA welding, referred to as manual arc welding.
Principle
MMA Welding process: Manual arc welding consists of a welding power source, welding cables, welding clamps, welding rods, welding parts, and arcs. During welding, the welding rod is contacted with the workpiece to ignite the arc, and then the welding rod is lifted and kept at a certain distance. The welding power source provides a suitable arc. Under voltage and welding current, the arc burns stably and generates high temperature, and the electrode and weldment are locally heated to a molten state. The molten metal at the end of the welding rod and the molten weldment metal fuse together to form a molten pool. During welding, the arc moves with the welding rod. And the liquid metal in the molten pool gradually cools and crystallizes to form a weld, and the two weldments are welded together.
During welding, the core of the welding rod melts and transitions to the molten pool in the form of droplets. At the same time, the coating of the welding rod produces a certain amount of gas and liquid slag. The generated gas fills around the arc and molten pool, isolating the air. Liquid slag is less dense than liquid metal and floats on top of the molten pool. Thereby protecting the molten pool. When the metal in the molten pool cools and solidifies, the slag also solidifies to form welding slag covering the surface of the weld, preventing the high-temperature weld metal from being oxidized and reducing the cooling rate of the weld. During the welding process, complex metallurgical reactions such as deoxidation, sulfur removal, phosphorus removal, and hydrogen removal occur between liquid metal, liquid slag, and gas. So that the weld metal obtains appropriate chemical composition and structure.
Features
1. The equipment is simple.
2. Flexible and convenient operation.
3. It can perform all-position welding and is suitable for welding a variety of materials.
4. The disadvantages are low production efficiency and high labor intensity.
