Method to Overcome Gap Variation by Control of Arc Force in Root Pass Welding for Back Bead by GMAW

Son, Chang-Hee; Cho, Sang-Myung

Journal of KWJS 2011;29(6):77-81.
Published online January 20, 2012.

GMAW 루트패스 이면비드 용접에서 아크력제어에 의한 갭변동 극복 방법

Method to Overcome Gap Variation by Control of Arc Force in Root Pass Welding for Back Bead by GMAW

Abstract

  In most industry, manual GTAW welding is preferred for formation of stable back bead in root weld of butt joint. However, manual GTAW welding has low productivity as compared with GMAW, also it has unstable bead quality which depend on skilled workers. So it is necessary to develop process of root pass welding by using automation GMAW that have stable back bead formation and high productivity. In this paper, the design of U-groove with 3㎜ root face was applied to extend the tolerance of misalignment in condition of standard root gap 1.5㎜.
  Consequently, for the formation of stable back bead in root pass of butt welding, in case of the narrow root gap(0.5㎜) the large arc force was applied by increasing the current and voltage. In case of the large root gap(2.5㎜), the small arc force was applied by decreasing the current and voltage. Considering the various root gap, the required deposited metal was controlled by welding speed only.

Key Words: GMAW, Arc force, U-groove, Root gap, Misalignment, Root pass welding