PURPOSE: To control the component compsns. of weld metal and to prevent the generation of microcracks by penetrating a component-controlled ingot block which is interposed within the root surfaces in the groove of a welded joint deep by welding under the conditions of burying the arc.

CONSTITUTION: In submerged or gas shielded arc welding of multiple electrodes, for example, in the former, an insert 5 of a steel block 5 is held in place between the butt surfaces of steel plates 1, 1' to be welded. The arc is generated between a wire 7 and the insert 5 in the flux to melt the insert partially, whereby molten metal 3 is formed. After this, the plates 1, 1' are turned over to weld the opposite side similarly and to melt the unmolten insert 5 fully, and this completes the welding of the plates 1, 1'. The dependency of the compsn. of the metal 3 upon the plates 1, 1' is reduced by this; therefore, the metal 3 of high cracking resistance is formed by controlling the components of the insert 5.