A filler metal used in welding is determined by which of the following factors?

The appropriate selection for determining a filler metal in welding is based on the base metal composition and thickness. This is crucial because the filler metal must be compatible with the base metals to achieve a strong weld joint. The composition affects the chemical and physical properties of the weld, such as its strength, corrosion resistance, and weldability. For instance, using an improper filler metal can lead to issues like cracking or inadequate fusion in the weld.

Furthermore, the thickness of the base metal influences the choice of filler metal as it affects the heat input required during the welding process, which can impact the penetration of the weld and the overall quality of the joint. Selecting a filler metal that aligns with both the composition and thickness ensures that the weld can handle the intended service conditions and stresses it will face.

Choosing filler metal based on personal preference, the color of the filler metal, or the type of welding robot is less relevant and could compromise the integrity and performance of the weld. Each of these factors involves considerations that do not guarantee compatibility or strength in the weld joint.