From critical COD δ_c of HT 80 welded bonds, brittle fracture initiation temperatures at the residual stress field are calculated using COD concept. These temperatures are compared with the temperature Ty, which is calculated from K _c using the equation K _c =√ E σ _yδ_c· T _y indicates the temperature at which the brittle fracture initiation stress reaches to the yield stress of the material. It is clarified that the temperature T _y can be substituted approximately for the brittle fracture initiation temperature of welded joints with the residual stress of the longitudinally welded bead. The validity of T _y is certified by an example of cross-welded notch tests. This paper proposes to employ this temperature T _y for the quality assessment of welded joints of high strength steels. T _y can be obtained from bending COD tests and tensile tests at low temperature. An experimental example on HT 80 welded bonds shows a good correlation between T _yand Charpy transition temperature _v T _s, consequently giving the relation between the Charpy requirement and the defect size at HT 80 welded bonds.