The time-dependent distributions of temperature and stresses in a box-column welded from ultra thick plates with a center segregation were analyzed using the commercial finite element package SYSWELD+ for several types and angles of groove. The welding method used in the current study was SAW(submerged arc welding), which was initially simulated using the commercial finite element package MSC/MARC, combined with a user-defined subroutine, to identify the weld thermal cycle. The major points of investigation were the optimum type and angle of groove that would minimize the weld stress, especially at the center segregation. A nonlinear transient heat transfer analysis was accomplished. The thermal properties, i.e. conductivity and specific heat, were found to be temperature dependent, plus the effects arising from a phase change, convection, and radiation were also taken into account.