In the welded joints, it becomes a common idea that the strength of weld metals is equal to or higher than it of base metal from the viewpoints of efficiency of welded joints. Otherwise, it is effective to use the weld metal whose strength is lower it of base metal in order to prevent the initiation of weld cracking. If welded joints having lower grade weld metal have larger strength than it required as the welded joints, it is one of the useful welding procedure to use the lower grade welding rod.
In this report, the state tensile and brittle fracture behaviors of the welded joints having wled metal whose strength is lower than it of base metal—so called "Soft Welded joints"—are investigated. The example results of calculations about soft ratio and fracture toughness of weld metal required to guarantee the static tensile and brittle fracture strength which is almost equal to those of base metal were showed (Figs. 5, 11, 12, 15). In a case of production or selection the welding rod, a suggestion about tensile strength required as weld metals was made (Fig. 8).