Degradace vlastností duplexní oceli po expozici čpavkem

Abstract

The purpose of this thesis is to determine the degree of degradation of mechanical properties and structure of ammonia condenser tubes after 19 years of exposure. Tubes 25 x 1.5 mm are of the duplex material, 2205 (1.4462). Mechanical properties were determined using tensile tests. Inclusions and disruption of surface cracks were evaluated using Olympus IX70 light microscope and electron microscope. Microstructure was observed using a scanning electron microscope JEOL JSM 6490 LV. There were detected surface defects and cracks on the tubes indicating that the life of the material was ending.It was found that in the duplex structure affected by ammonia at low temperatures the ferritic phase of duplex stainless steel 2205 (l. 4462), was more corrosion resistant than the austenitic. Mechanical values show only a slight decline. Material SAF 2205 (1.4462) in this case has fully complied with its use and confirmed its good mechanical properties and excellent corrosion resistance to ammonia at lower temperatures.