STRUCTURE AND PROPERTIES OF THE METAL OF EI756 STEEL STEAMLINE PIPING AFTER OPERATION FOR 20,000 h.

An investigation was carried out into the properties of piping from the martensitic-ferritic steel 1CR12W2MoV (E1756) which is more heat-resistant than others and whose welds possess high plasticity under prolonged loading. An experimental steamline with these welds has been in use with a 300 MW unit at the Pridneprovskaya central power station. The tube metal was subjected to metallographic analysis and its mechanical properties were determined from short-time tests and the long-time strength; the chemical composition of the secondary phases was also investigated. The tests were carried out at 585 degree C, and showed that after 20,000 h the strength properties of the metal had changed little. The most noticeable change was the reduction in the impact strength due to precipitation of the intermetallic phase Fe//2W. Plasticity remains at a satisfactory level.