VARIATIONS OF THE IMPACT TOUGHNESS OF 12KH1MF STEEL IN OPERATING STEAM PIPELINES OF THERMAL POWER PLANTS

摘要

It is shown that, in the intact state, the impact toughness of 12KhlMF steel at room temperature is, as a rule, higher than at the elevated temperature (545°C) for metals both with fair and defective microstruc-tures. It is demonstrated that, under the conditions of long-term operation of the steam pipelines of thermal power plants at room temperature, the impact toughness of steel usually decreases. However, at the working temperature, its changes are insignificant. Hence, the brittle-fracture resistance of the metal at room temperature becomes lower than that at the elevated (working) temperature. We reveal the cases of anisotropy of the impact toughness of the metal cut out from a bend of the steam pipeline with cracklike defects. A correlation dependence of the impact toughness at room temperature on the relative narrowing obtained in the tests for static tension is established.