The welding process commonly used for fabricating tailor-welded blanks of dissimilar thickness for automotive applications is:

The correct option is laser welding.

Tailor-welded blanks (TWBs) consist of individual sheets of steel or aluminum of different thicknesses, grades, or coatings welded together into a single flat blank before stamping. This allows automotive engineers to place the right thickness and grade of material exactly where it is needed for structural strength and weight reduction.

Laser welding is the preferred and most commonly used process for fabricating tailor-welded blanks for several key reasons:
1. Low Heat Input and Narrow Heat-Affected Zone (HAZ): Laser welding utilizes a highly concentrated, high-energy-density light beam. This results in minimal heat input to the surrounding metal, producing a very narrow and deep weld bead with a minimal heat-affected zone. This is crucial for preserving the mechanical properties of the parent metals, especially when joining dissimilar thicknesses.
2. High Speed and Precision: The laser beam can be precisely controlled and focused at the joint interface, allowing high welding speeds which are ideal for automated, high-volume automotive production lines.
3. Minimal Distortion: Because the heat is concentrated, thermal distortion and warping of the welded blank are minimized, ensuring the blank remains flat and suitable for subsequent stamping or forming operations.

Other welding methods like gas welding, conventional arc welding, or friction welding are not as suitable. Gas and arc welding introduce excessive heat, leading to wider heat-affected zones and significant thermal distortion. Friction welding is generally more complex to apply continuously to long, flat sheet metal blanks of different thicknesses.