Which of the following is not required on a welder's performance qualification?

When assessing a welder's performance qualification, essential variables must be documented as they affect the strength and soundness of the weld. Essential variables include aspects such as the welding process, type of base materials, welding positions, and filler metal used, which can significantly influence the quality of the weld.

On the other hand, nonessential variables do not affect the weld quality and are not required in the welder's performance qualification documentation. Nonessential variables might include details such as the specific welding technique used (e.g., the speed of travel or the angle of the torch), which, while they can have an effect on the final appearance or ease of the welding process, do not directly impact the structural integrity of the weld joint.

Material specifications, which encompass the types of materials being welded and their classifications, are critical for performance qualification. Welding techniques, while perhaps vital for an understanding of the welder's skill and approach, generally fall under the category of nonessential variables unless specified as a requirement in the context of the qualification.

In summary, nonessential variables are not a requirement for a welder's performance qualification because they do not influence the mechanical properties, strength, or quality of the completed weld as significantly as essential variables do.