What change necessitates requalification of a procedure for automatic welding without filler metal?

The requalification of a procedure for automatic welding without filler metal is particularly necessitated by changes in joint dimensions. This is because joint dimensions play a critical role in the welding process and can significantly affect the quality and integrity of the weld. Changes in the dimensions could result in variations in the fit-up and may alter the heat transfer characteristics during the welding process, ultimately impacting the mechanical properties and consistency of the weld.

In this context, while factors like the time between passes and changes in shielding gas can influence certain aspects of the welding process, they are not as foundational as joint dimensions. Time between passes may affect the overall efficiency and heating of the weld but doesn’t fundamentally change how the weld is executed in terms of structural integrity. Similarly, the shielding gas's composition can be important for specific applications but does not necessitate a complete requalification when other parameters remain unchanged. Thus, any adjustments in the joint dimensions require a thorough reassessment and requalification to ensure that the welding procedure remains valid and provides the necessary mechanical performance.