In horizontal position welding, the gravity makes molten metal flow downward and sometimes causes weld defects such as undercut and overlap.

横向焊接时由于熔化金属重力的作用，会引起熔池金属下淌，从而产生咬边以及焊瘤等焊接缺陷。

youdao

The project position of welder qualification test for long transporting pipe depends on vertical down welding basically, which is namely fixed pipe with axis horizontal welding (5gx).

长输管道的焊工考试项目位置基本以向下焊为主，即水平固定全位置焊(5gx)。

youdao