What primarily determines the size of a weld in AWS D1.1?

The size of a weld as specified in AWS D1.1 is primarily determined by the base metal thickness and joint configuration. This is because the thickness of the base metals being joined influences the amount of weld material required to ensure a strong connection that can adequately support the intended loads. The joint configuration also plays a crucial role, as different configurations (such as groove, fillet, or butt joints) have specific requirements for the weld size to achieve proper penetration and fusion, which are essential for the structural integrity of the weld.

While factors like the type of filler metal used may influence the weld's characteristics and its performance in specific applications, they do not primarily dictate the weld size. The design of the joint, including its geometry and the thickness of the materials being joined, provides the fundamental criteria that dictate how large or small the weld must be to meet the required specifications for strength and performance.