Abnormal manifestation of the high-temperature degradation of the weld metal of a low-alloy steel welded joint

We have shown that hardness, impact toughness, mechanical properties in tension, and the local parameters of fracture mechanics (static and cyclic crack resistance) are sensitive to the operating degradation of weld metal of steam pipelines of thermal power plants made of 15Kh1M1F steel. The simultaneous decrease in the resistance to brittle and plastic fracture (hardness, strength, and impact toughness) represents a phenomenon of the operating degradation of weld metal. We have established a specific correlation between the characteristics of plasticity and other mechanical parameters of operated metal: the increase in °₅ of operated weld metal is in good agreement with the decrease in its strength, whereas the reduction of Ψ correlates with the lowering of resistance to brittle fracture. Electrolytic hydrogenation decreases the characteristics of strength and plasticity of operated weld metal much stronger than in the initial state. The absence of ferritic edgings on the boundaries of primary austenitic grains makes for a low resistance to brittle fracture, and the change in acicular ferrite deteriorates the mechanical properties. The ductile fracture of nonoperated metal is replaced by brittle intercrystalline failure in operated metal. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 1, pp. 73–79, January–February, 2007.