Investigation of notch impact and dwtt strength at lowtemperatures in Ti - Nb micro alloyed high strength petroleum pipesteels (API)

Steel pipes are used to continue the use of liquid and gas fossil fuels in the world and to transport the need to the required regions. In order to meet this need, petroleum pipe steels, whose standards have been determined by the American Petroleum Institute, are produced with different production technologies both in Turkey and in various regions of the world. There are very important parameters to be considered in steel production so that the steel pipes used during the transportation and use of these fuels such as oil and natural gas are not affected by external factors, especially climatic conditions. In case the climatic conditions in which the pipes are used have very low temperatures, it is aimed to have higher resistance than steel pipes and not to create situations that will prevent the transportation of fuels such as oil and natural gas. For this reason, the minimum mechanical properties required by the institute have been determined by the standards. It is mandatory for steel manufacturers to comply with these standards during the production and end-use approval stages of the relevant steel pipes. In the northern countries where the climatic conditions are difficult, the pipe specifications to be used must have more stringent specifications. In this thesis, the considerations during the production of steels used in oil and natural gas pipe transportation that are resistant to cold climate conditions and the production of steels that can show high impact resistance in colder conditions are examined. In addition to statistical data analysis methods, the results of industrial production were examined with the steel microstructure characterization studies in the laboratory environment, and as a result, the parameters that can increase the resistance at low temperature for petroleum pipe steels, which our country has a large share in the production, were determined.