In fabrication of pressure vessel, narrow gap submerged arc welding is an important process in order to decrease the number of welding passes of thick steel plate, however, conventional fluxes are applied to narrow gap groove, it it very difficult to remove welded slag. It was found out from experimental results that a decrease in expansion due to transformation or an increase in the total thermal contraction of slag during cooling period is effective in imporovimg slag detachability. According to this results, A new agglomerated flux which has good detachability has been developed.
