PURPOSE: To enable stable welding free from welding cracks and lowering of strength of welded metals by using a "Hastelloy" type welding material for root pass, and an "Incone" type material for succeeding pass.

CONSTITUTION: In submerged arc welding of 9% Ni-steel base metal, a "Hastelloy" type welding material is first used for welding of root pass. Successively, a material of "Inconel" type is used for other welding pass. By this welding method, welding cracks can be prevented and a stable weld zone is obtained without lowering of strength of welded metal. Further, by combined use of the both welding materials, whole weld zone can be welded by automatic welding only and reduction of cost and improvement of efficiency are realized.