Short Answer:

Arc welding is a process of joining metals by melting their edges with the heat produced by an electric arc. The arc is created between an electrode and the workpiece when current passes through the air gap. The heat of the arc (around 6000°C to 8000°C) melts the base metal and the electrode, forming a strong joint after cooling.

It is widely used in industries because it provides deep penetration, strong joints, and can be applied to a wide variety of metals. Arc welding is suitable for construction, shipbuilding, and fabrication work where durable metal joining is required.

Detailed Explanation :

Arc Welding

Arc welding is one of the most important metal joining processes used in mechanical engineering and manufacturing industries. It uses an electric arc to generate intense heat to melt and fuse metals together. The process is efficient, versatile, and capable of producing high-quality joints in different metals and thicknesses.

1. Principle of Arc Welding:
   The working principle of arc welding is based on the formation of an electric arc between the electrode and the workpiece. When the electrode is brought close to the metal surface and an electric current passes through the circuit, the air gap between them becomes ionized, allowing current to flow across it. This current produces an arc with very high temperature, which melts both the base metal and the tip of the electrode. When the molten metal cools, it forms a solid, strong joint.

The main source of heat is the electrical energy converted into thermal energy by the arc. The temperature produced is sufficient to melt most metals and even some refractory materials.

2. Equipment Used in Arc Welding:
   The basic setup for arc welding includes the following components:

• Power Source: Supplies either direct current (DC) or alternating current (AC) to create the arc.
• Electrode Holder: Used to hold and guide the electrode.
• Electrode: Conducts current and provides filler material for the joint.
• Work Clamp (Return Lead): Completes the electrical circuit.
• Welding Cables: Carry current between the power source, electrode holder, and workpiece.
• Protective Equipment: Includes gloves, helmet, apron, and face shield to protect the welder from sparks and radiation.

3. Types of Arc Welding:
   There are several types of arc welding processes, classified based on the type of electrode used and the method of arc generation. The most common ones are:

• Shielded Metal Arc Welding (SMAW): Also known as stick welding; uses a coated electrode that melts to form the weld and shield it from contamination.
• Metal Inert Gas Welding (MIG): Uses a continuous wire electrode and a shielding gas (like argon or CO₂) to protect the molten pool from oxidation.
• Tungsten Inert Gas Welding (TIG): Uses a non-consumable tungsten electrode with an inert gas shield. Produces very clean and precise welds.
• Submerged Arc Welding (SAW): Uses a granular flux layer to cover the arc and prevent spatter.
• Flux-Cored Arc Welding (FCAW): Similar to MIG but uses a tubular electrode filled with flux.

4. Working of Arc Welding:
   In operation, the welder connects the power source and adjusts the current. The electrode is brought near the workpiece surface to strike the arc. Once the arc is established, it produces intense heat, melting the base metal and the electrode tip. The molten metal from the electrode fills the joint gap.

A layer of slag or shielding gas protects the molten pool from the atmosphere, preventing oxidation. After cooling, the molten pool solidifies to form a strong, durable weld joint. Proper current, arc length, and travel speed are essential for good weld quality.

5. Advantages of Arc Welding:

• Produces strong and durable joints.
• Suitable for both ferrous and non-ferrous metals.
• Can weld thick as well as thin materials.
• Portable and cost-effective.
• Can be used in various positions and environments.

6. Limitations of Arc Welding:

• Requires skilled operators.
• May produce fumes and ultraviolet radiation that require protection.
• Distortion and residual stresses may occur due to high heat.
• Not suitable for very thin materials without proper control.

7. Applications of Arc Welding:
   Arc welding is extensively used in:

• Fabrication of steel structures and machinery.
• Construction of ships, bridges, and buildings.
• Automobile and aerospace industries.
• Pipeline and pressure vessel fabrication.
• Repair and maintenance works.

Conclusion:

Arc welding is a widely used metal joining process that relies on the heat of an electric arc to fuse metals. It provides strong, permanent joints and is suitable for a variety of materials and thicknesses. Though it requires skilled handling, its versatility and strength make it essential in modern manufacturing and construction industries. Continuous improvements in electrodes and automation have made arc welding more efficient and reliable for industrial applications.