In the paper the reasons for steam pipeline’s elbow material rupture, made of steel 13CrMo4-5 (15HM) that is being used in the energetics.
Based on the mechanical properties in the ambient temperature (Rm, Rp0,2 and elongation A5) and in the increased temperature (Rp0,2t
) it
was found, that the pipeline elbow’s material sampled from the ruptured area has lower Rp0,2 i Rp0,2t by around 2% than it is a requirement
for 13CrMo4-5 steel in it’s base state. The damage appeared as a result of complex stress state, that substantially exceeded the admissible
tensions, what was the consequence of considerable structure degradation level. As a result of the microstructure tests on HITACHI S4200
microscope, the considerable development of the creeping process associates were found. Also the advances progress of the microstructure
degradation was observed, which is substantial decomposition of bainite and multiple, with varied secretion size, and in most cases
forming the micro cracks chains. With the use of lateral micro sections the creeping voids were observed, that creates at some places the
shrinkage porosities clusters and micro pores.