Effect of long-term thermal influence on mechanical properties of welded joints for carbon steels used in power engineering

For the manufacture of separate power equipment components (steam generators, separators, collectors, pressurizes and so on) it is wide used carbon steel of the type 22K. As these elements are very responsible for pressure vessels having a thickness above 80 mm it is therefore best to apply steel of improved metallurgical quality, obtained by means of electroslag or vacuum-are re-melting. As a rule, 22K steel of standard quality (open-hearth furnace melting) is usually used for multiple forced circulation circuit (MFCC) piping of RBMK reactors and special melting methods - for steam generator case. The application of special method of melting for this type of steel provides a higher quality level. High requirements are imposed also on the level of welded joints mechanical properties at 20 degrees C (ultimate tensile stress UTS = sigma(B) = 420 MPa, yield stress YS = sigma(0.2) =220 MPa, elongation A(5) = 20%, reduction of area Z = 50%), which practically coincides with the minimum level of base metal properties, specified in TY24-3-449-74.