| Abstrakt: |
The concept of durability during the operation of metal structures is one of the most important factors in assessing the duration of the operation of an object. At the same time, an important task is to determine the service life of the structure until the moment when it completely becomes unusable. The main issue in determining the durability is to identify the stress concentration zones, most often during the operation of the equipment these are cracks. These defects, along with a corrosive environment, cause corrosion fatigue of the metal and during operation can become the main cause of the failure of both brittle and ductile materials when cyclic loads are applied. The aim of the paper is to study the low-cycle corrosion fatigue of St37-2 steel in aggressive environments that simulate the operating conditions of refinery equipment. A sample of structural carbon steel grade St37-2 was used as the object under study. The test is carried out on a flat specimen 480×39×10 mm3 in size. The specimen is tested according to the pure bending scheme and symmetric loading cycle. 3% NaCl and an oil emulsion were used as the medium. During the study, it was revealed that with an increase in the number of loading cycles, the thermodynamic stability of the metal in a corrosive environment decreases, which is obviously associated with the accumulation of fatigue damage. The most rapid destruction was experienced by the sample with the application of 3% NaCl simulating ground and formation water, as well as the atmosphere of the maritime climate. Such a rapid destruction is possible due to the violation of the passivity of steel due to pitting in the presence of chloride ions. [ABSTRACT FROM AUTHOR] |
