Which welding process is NOT classified under arc welding processes?

Explanation:

Electroslag Welding:

• Electroslag Welding (ESW) is a highly efficient welding process primarily used for joining thick metal sections (typically 25 mm and above) in a single pass. Here’s a detailed breakdown:

How It Works:
1. Setup:  

•  The workpieces are positioned vertically with a gap between them.  
• Copper shoes (dams) are placed on both sides to contain molten metal and slag.  
• A welding wire (electrode) and flux are fed into the gap.  

2. Ignition:  

• An electric arc is initially struck to melt the flux, forming a conductive molten slag pool.  
• Once the slag pool is established, the arc is extinguished, and the process transitions to resistance heating.  

3. Welding Phase:  

• Electrical current passes through the conductive slag, generating intense heat (up to 1,700–2,000°C) due to slag resistance.  
• The heat melts the filler wire and the edges of the workpieces, creating a molten weld pool.  
• As the weld solidifies from bottom to top, the copper shoes move upward progressively.  

4. Solidification:  

• The molten metal cools and solidifies, forming a dense, high-quality weld.  
• The slag floats atop the weld pool, shielding it from oxidation.  

Key Features:

• No arc: Unlike arc welding, ESW relies on resistive heating of slag after the initial arc phase.  
• Vertical orientation: Best suited for thick, vertical joints (e.g., ship hulls, pressure vessels).  
• Single-pass capability: Can weld very thick materials (up to 300 mm) without multipass layers.  
• Low distortion: Slow cooling reduces residual stresses.  

Applications:

• Heavy industry (e.g., bridges, turbines, nuclear reactors).  
• Large structural components (e.g., shipbuilding, oil rigs).  

Additional Information

Atomic Hydrogen Welding

Definition: Atomic Hydrogen Welding (AHW) is a welding process that uses hydrogen gas as a shielding gas and an electric arc between two tungsten electrodes. The hydrogen gas is dissociated into atomic hydrogen in the arc, which then recombines on the metal surface, releasing heat and providing a high-temperature welding environment. This process is not classified under arc welding processes because it primarily relies on the chemical reaction of hydrogen atoms to generate heat rather than the direct use of an electric arc to melt the metal.

Working Principle: In Atomic Hydrogen Welding, an electric arc is struck between two tungsten electrodes in the presence of a stream of hydrogen gas. The intense heat of the arc dissociates the hydrogen molecules (H₂) into atomic hydrogen (H). As the atomic hydrogen comes into contact with the cooler metal workpiece, it recombines to form hydrogen molecules again, releasing a large amount of heat. This heat is sufficient to melt the metal and create a weld pool. The hydrogen gas also acts as a shielding gas, protecting the molten weld pool from atmospheric contamination.

Advantages:

• Provides a very high-temperature welding environment, capable of welding refractory metals.
• Hydrogen gas serves as an excellent shielding gas, preventing oxidation and contamination of the weld pool.
• Produces very clean and high-quality welds due to the inert nature of hydrogen.
• Suitable for welding thin materials and intricate components.

Disadvantages:

• Complex setup requiring precise control of hydrogen gas flow and electrode positioning.
• Higher operational costs due to the use of tungsten electrodes and hydrogen gas.
• Not suitable for welding thick materials due to limited penetration depth.
• Requires skilled operators to handle the equipment and control the welding process.

Applications: Atomic Hydrogen Welding is commonly used in specialized applications where high-quality welds are required, such as in the aerospace industry, electronic components, and precision instruments. It is particularly useful for welding high-melting-point materials like tungsten, tantalum, and molybdenum.

Tungsten Inert Gas Welding

Tungsten Inert Gas (TIG) Welding, also known as Gas Tungsten Arc Welding (GTAW), is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by an inert shielding gas, usually argon or helium. The process allows for precise control over the welding variables, making it ideal for welding thin materials and achieving high-quality welds. TIG welding is widely used in industries requiring high precision and clean welds, such as aerospace, automotive, and stainless steel fabrication.

Stud Arc Welding

Stud Arc Welding is a specialized arc welding process used to attach fasteners, such as studs or pins, to a metal workpiece. An electric arc is created between the stud and the workpiece, melting both surfaces. The stud is then pressed into the molten pool, creating a strong, permanent bond. This process is highly efficient for attaching fasteners in various manufacturing and construction applications, including shipbuilding, automotive, and steel structures.