Study of mechanical properties and brittle fracture resistance for weld metal of WWER RPV

Abstract

The results of the study of mechanical properties and brittle fracture resistance (BFR) are presented for weld metal of WWER RPV performed by automatic arc welding with use welding wire Sv-15CrNiMoTiA and ceramic flux 48AF-71. Mechanical properties are determined on the basis of test results of tensile smooth round bar. BFR are determined from impact strength tests and fracture toughness tests. The anisotropy of mechanical properties and BFR is investigated by testing the specimens with different orientations. Tests are conducted for specimens of two orientations: first orientation corresponds to the position of the specimen, in which the fracture surface is perpendicular to the axis of the weld; second orientation corresponds fracture surface parallel to the axis of t he weld. It i s shown that the weld metal performed according to above mentioned technology has no anisotropy both in mechanical properties and in BFR. An explanation of the significant scatter of BFR on the basis of the results of metallographic studies is proposed. The obtained experimental results on mechanical properties for investigated weld metal allow to use tensile smooth round bar with 3 mm diameter with transverse orientation instead of specimens with 6 mm diameter with longitudinal orientation as the scale factor and anisotropy are negligible. The correlation dependence between the values of reference temperature T0 determined by the Master Curve method and reference temperature T100 determined by the Advanced Unified Curve method and the value of critical brittleness temperature TK0 for the studied weld metal in the initial state is established.