AGING IVESTIGATION OF METALS OF THE PIPES IN LITHUANIAN POWER STATION

Abstract

This article presents the investigation of mechanical characteristics of the pipe's straight part dependence on operating temperature and exploitation times. The strength characteristics  s_pl, R_p0,2, R_m, s_fl  decrease with increasing exploitation life and temperature, whereas the plasticity characteristic Z a little depend on the exploitation life. It increases with the increasing temperature, except for the pipe after 160 000 h of exploitation.When steel 12Ch1MF is used at 550°C temperature long time, intensive carbon diffusion takes place. Thus carbon contained in perlite diffuses and forms carbides, which results in worsening of steel's properties: increasing plasticity and decrease strength characteristics. Comparison thick walled pipes (Lame) and thin walled pipes equations results with results the finite element method showed that Lame theoretical equation describes stresses in the pipes more precisely.

http://dx.doi.org/10.5755/j01.mech.17.1.198