Question

Which one of the following is a solid state joining process?

• A. Gas tungsten arc welding
• B. Resistance spot welding
• C. Friction Stir welding
• D. Submerged arc welding

Hint:

Solid-state welding processes offer several advantages, including lower heat input, reduced distortion, and the ability to join dissimilar materials that are difficult to weld using fusion processes. Other examples of solid-state welding include diffusion welding, ultrasonic welding, and forge welding.

Answer 1

The Correct Option is C

Step 1: Understand the definition of a solid-state joining process.
A solid-state joining process is a welding process in which coalescence (joining) of materials occurs without melting the base materials. The joining is achieved by applying pressure, heat (below the melting point), or a combination of both, often with significant plastic deformation at the joint interface. Step 2: Analyze each of the given welding processes.
(1) Gas Tungsten Arc Welding (GTAW): Also known as TIG welding, this is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. An inert shielding gas (argon or helium) protects the weld area from atmospheric contamination. GTAW involves melting the base materials and often a filler metal to create the weld. Therefore, it is a fusion welding process, not a solid-state process. (2) Resistance Spot Welding (RSW): This is a resistance welding process in which overlapping metal sheets are joined by the heat obtained from the resistance to electric current flow through the workpieces held together under pressure by electrodes. RSW involves localized melting at the faying surfaces due to the high current and resistance. Thus, it is a fusion welding process. (3) Friction Stir Welding (FSW): This is a solid-state joining process that uses a non-consumable tool that rotates and traverses along the joint line of two workpieces. The frictional heat generated by the rotating tool and the applied pressure cause the material to soften and undergo intense plastic deformation. This deformed material is mechanically intermixed by the rotating tool, creating a strong, solid-phase weld. Since the base materials do not melt, it is a solid-state process. (4) Submerged Arc Welding (SAW): This is an arc welding process in which the arc and the weld pool are shielded by a granular fusible flux on the workpiece. The arc is struck between a continuously fed consumable electrode and the workpiece. SAW involves melting the base materials and the electrode to form the weld. Therefore, it is a fusion welding process. Step 3: Identify the solid-state joining process from the analysis.
Based on the definitions, Friction Stir Welding (FSW) is the only process among the given options that joins materials without melting the base materials.