부산대학교 도서관

Microstructure, hardness distribution, tensile properties and fracture behavior of the quenched and tempered steel 28MnCrB5 were investigated before and after corrosion tests. The corrosion behavior of the quenched and tempered steel 28MnCrB5 was examined in two different acidic environments, namely a hydrochloric acid solution and fertilizer-containing soil. The specimens were immersed in corrosive environments for 24, 48, 72, 96, 120, 144 and 168 hours, and additionally into fertilizer-containing soil for 240 days. The corrosion losses were determined by measuring the weight changes and the respective corrosion rates were calculated. Ductile fracture was observed in the sample of the quenched and tempered material before and after 168 hours of exposure to the hydrochloric acid solution and fertilizer-containing soil environment. But, in the sample subjected to corrosion in the fertilizer-containing soil environment for 240 days, brittle fracture took place and the fracture topography on the surface exhibited inter-granular cleavage. After 240 days of corrosion test in the fertilizer-containing soil environment, the ductility of the material decreased to a very great extent. The surface of the quenched and tempered 28MnCrB5 samples was covered by corrosion pits, cracks and peelings at the end of 168 h tests in the hydrochloric acid solution environment. At the end of 240 day tests in the fertilizer-containing soil environment, the surface of the samples showed deep peelings and cracks.