Selection Criteria for Heat Treatment in Order to Optimize Reconstructed Heat Supply Turbine Body Metal Component Properties

For the first time results of heat treatment under laboratory and industrial conditions of housing components made of 15Kh1M1FL grade steel with an operating time of more than 150 thousand hours by six versions during reconstruction of PT-60-130 and T-100-130 turbines are summarized. Heat treatment version tensile properties, critical brittleness temperature, and stress-rupture strength are considered for each metal. It is demonstrated by experiment that high temperature tempering is most suitable for components with metal whose forecast strength properties exceed by 50 MPa those predicted for operating hours. It is established that single normalizing with tempering provides adequate mechanical properties for metal components made of steel grade 15Kh1M1FL for short-term and long-term loading, and it is most suitable for high pressure cylinder housings whose metal strength decreases during prolonged use. It is demonstrated that for metal components made of the steel in question three heat treatment versions with double heating above the full recrystallization temperature and tempering provides increased short-term and stress-rupture strength combined with relatively moderate crack resistance under impact loading. In view of significant oxidation capacity and the possibility of treated surface distortion use of these regimes is most appropriate for stop and control valve housings within whose metal micro-damage may occur alongside cracking. Cyclic heat treatment with heating below the complete recrystallization and tempering temperature did not provide a favorable result.