What is the root opening required for a C-U2a groove with a minimum angle of preparation of 20°?

The root opening for a C-U2a groove weld is determined by the preparation angle and the design specifications outlined in the AWS D1.1 code. For a groove weld with a minimum angle of preparation of 20°, the code specifies that the root opening should be consistent with the requirements outlined in Table 3.4 of AWS D1.1.

For a C-U2a groove preparation, the root opening is typically aligned with the thickness of the base material being welded. A common practice is to have a root opening that allows for proper penetraion and fusion of the weld metal into the base material. Given the minimum angle of preparation, a root opening of 5/8 inch facilitates adequate control of weld quality and integrity during welding procedures.

This choice is correct because it aligns with the design intent for ensuring robust weld performance while following the prescribed standards in the AWS D1.1 code, which takes into account various factors such as the ease of welding, heat input, and prevention of defects like lack of fusion or incomplete penetration. The specifications draw from years of industry experience and research regarding effective welding practices.