What is the required root opening for joint B-U7, with an angle of 45°, welded in the 3G position?

The required root opening for a B-U7 joint welded in the 3G position with an angle of 45° is indeed 0 - 1/8 inch.

For the B-U7 joint configuration, which involves a bevel and a root opening, the AWS D1.1 code provides specific guidelines. The appropriate root opening is influenced by factors such as the thickness of the base material and the welding process. A joint with an included angle of 45° typically calls for a narrower root opening to ensure proper fusion and penetration during the welding process.

In this scenario, a root opening of 0 - 1/8 inch is optimal as it allows for adequate penetration while minimizing the risk of inclusions and voids. Such a narrow opening works well with various welding processes and helps maintain the integrity of the weld. Wider root openings could lead to a lack of fusion or may require additional filler material, which could compromise the weld quality.

This understanding of root openings in conjunction with joint type and position is critical in adhering to the AWS D1.1 Structural Welding Code and ensuring high-quality welds in structural applications.