Corrosion-fatigue strength of operational degraded steel of marine portal crane elements

The results of fatigue strength tests of low-carbon steel for a 33-year operated portal crane are presented. For the experiments, the upper shelf of the rocker arm and the right wall of the column, the metal of which differed twice in the level of impact toughness of the longitudinal specimens to the rolling direction, were chosen. Fatigue and corrosion-fatigue endurance curves of transverse specimens were constructed with the determination of the fatigue and corrosion-fatigue limits. The corrosive medium was a 3% NaCl aqueous solution, which simulated moisture condensed on the surface of steel parts caused by seawater sprayed near the coast. For two states of steel the difference in the fatigue limit is 15%. The corrosive environment at loading frequencies of 3 Hz slightly reduced the conditional corrosion-fatigue limit compared to the fatigue limit but fundamentally did not change the low sensitivity of this characteristic for evaluating the operational degradation of metal. A conclusion was made about the advantages of impact toughness compared to the fatigue limit for evaluating the technical state of the operated rolled products.