INFLUENCE OF ANNEALING TEMPERATURE ON LOW -CYCLE FATIGUE AND CYCLIC CREEP OF ULTRA-HIGH STRENGTH LOW-ALLOY STEEL

Low cycle fatigue and cyclic creep at ambient temperature of UHSLA, th e Czech equivalent of the American 300M steel, were studied for differ ent heat treatment (HT). Optimal properties correspond to the annealin g temperature of 300 degrees C that also provides the most favourable complex of other mechanical properties. Cyclic creep threshold curves were proved to exist for this steel, as well. Nevertheless, their rela tion to the fatigue life drop is significant only for high annealing t emperatures. Results show that steel investigated exhibits better mech anical properties than the ROL N steel currently used in the Czech mil itary aircraft and motor-car industry.