Critical temperature of brittleness of high-strength steel for fasteners of power engineering equipment under creep

A level of defect rate of structural service origin (under-cuts and cracks) in a fastener and impact specimen is studied for its effect on accuracy in determination of permissible values of critical temperature of high strength steel brittleness. An estimate of permissible values of critical temperature of the fastening metal brittleness is suggested which permits specifying more substantiated requirements to serviceability of the material at the stage of designing, production and servece as dependent on a technical state of steel and a level of the defect rate of a fastener as well as on a preset operational life of a threaded connection