Each G level has specific technical requirements and application scenarios, 

and welders need to undergo relevant training and certification to engage in these welding tasks.

1. **1G (Flat Position)**:

   - The pipe is placed horizontally, and welding is performed on the outer surface of the pipe.

   - Typically used for welding straight pipes.

2. **2G (Vertical Position)**:

   - The pipe is placed vertically, and welding is performed on the outer surface of the pipe.

   - Suitable for connecting vertical pipes.

3. **3G (Vertical Inside Welding)**:

   - The pipe is placed vertically, and welding is performed on the inner surface of the pipe.

   - Generally used for inner wall welding of vertical pipes.

4. **4G (Overhead Position)**:

   - The pipe is positioned above the welder's head, and welding is performed on the upper side of the pipe.

   - This welding position requires a higher level of skill.

5. **5G (Fixed Pipe Welding)**:

   - The pipe is placed horizontally but cannot be rotated; welding is performed on the outer surface.

   - Suitable for situations where welding must be done in a fixed position.

6. **6G (Inclined Position)**:

   - The pipe is inclined at a 45-degree angle, and welding is performed in this position.

   - This welding position has a high technical difficulty and requires the welder to have strong skills and experience.