When filling plugs or slot welds in metal over 5/8" thick, what percentage of the thickness of the metal must the fill be?

For plug or slot welds in metal that is over 5/8 inch thick, the requirement for the fill is that it must be at least 50% of the thickness of the base metal. This specification is important because it ensures adequate weld strength and integrity by requiring the weld to penetrate sufficiently into the material. This level of fill helps to maintain structural integrity and provides the necessary load-bearing capacity, especially in applications where welds are subject to high stress or loads.

A fill of 50% of the thickness ensures that the weld is not only effective but also allows for sufficient distribution of stresses across the base metal and the weld interface. This requirement is stipulated in the AWS D1.1 code to ensure that welds are designed to be strong enough to perform their intended function. Meeting this fill percentage is critical in preventing potential failure in the weld joint, thus enhancing the safety and longevity of the structure being built.