Papers by Keyword: Pressure Vessel Steel

Abstract: The production process, microstructure, and mechanical properties of 15MnNbR pressure vessel steel were studied by optical microscopy, universal tensile testing, and low-temperature impact toughness testing. It was found that the microstructure obtained after controlled rolling and cooling (known as thermo-mechanical control processing) consisted of ferrite and pearlite with non-uniform grain size. The banded microstructure was prominent, the strength was high, and the toughness was poor. After normalizing, the grain size was refined, both the microstructural uniformity and the banded microstructure were improved, and the strength and toughness of the steel were enhanced. After normalizing and water cooling, the grain was further refined, the microstructure was homogenized, the banded microstructure disappeared, and the strength and toughness of the test steel were improved simultaneously, resulting in excellent comprehensive mechanical properties.

Abstract: The research examines the improvements of mechanical properties of yield strength and toughness for an optimized chemical composition B2 used in industrial trial in comparison with usual chemical composition A1 used for pressure steel grade with higher strength and toughness. For both chemical compositions we rolled three plates with thickness 8, 10 and 12 mm. Rolling mode was a control rolling followed by normalizing heat treatment. Samples from each plate from opposites corner in as rolled and normalized state was taken and tested: spectral analysis, mechanical properties: tension tests, Charpy-V notch impact test. Differences between A1 and B2 chemical compositions are given by the micro alloing elements used and the overall results showed increasing YS and toughness values in the range of euronorm requirements.

Abstract: Increasing attention has been paid on fatigue performance evaluation in the recent years. More efficient fatigue testing methods are imperatively needed to accomplish the test requirement. The modified staircase theory is introduced in this paper. Traditional staircase method and modified staircase method are respectively used to evaluate the fatigue performance of pressure vessel steel Q345R. Results show the fatigue limits are 194MPa and 193MPa respectively, which indicates the modified staircase method can enhance the testing efficiency about 50% and keep the test veracity.

Abstract: The heat treatment process, normalizing plus tempering, of 150 mm-thick plate of 12Cr2Mo1R pressure vessel steel was proposed according to the results of finite element simulation and static CCT curve obtained by thermal simulation experiments. After normalizing at 910 °C for 10 minutes followed by water cooling and tempering at 650 °C for 60 minutes, the microstructure at 1/4 position along the thickness direction of the thick plate consists of bainite and all the mechanical properties meet delivery requirements.

Abstract: With the development of petrochemical industry, the status of pressure vessel has become increasingly important, and higher requirements are introduced for the security of nozzle zone at the pressure bearing region of pressure vessel. In order to study the stress status of nozzle zone at the channel of pressure vessel, solid modeling for channel and straight pipe was performed with ANSYS software. Through finite element analysis and calculation, the stress concentration region of channel was determined and the reason was analyzed. In addition, the nozzle zones of the model before and after loading were compared. The result reveals that symmetrical stress concentration region lies at the junction of channel and pipe. The maximum stress is located at the inside of nozzle zone of channel and less than the yield stress of material.

Abstract: The paper presents the results of finite element analysis of a pressurized vessel typically made of steel 1025 and containing the weld misalignment at the cylinder-to-cylinder junction. This misalignment considered in the vessel’s structure is because of girth weld that is found in most of the fabrications of such type of structures. Geometric misalignment of 50% of thickness is considered for this particular study. The work evaluates the geometrical effects of misalignment on the fatigue behavior of the pressure vessel to quantify its consequences in term of fatigue life and maximum damage. Finite Element (FE) analysis is performed by the use of ANSYS on one quarter of the structure due to symmetry. A significant effect of misalignment on fatigue life of the cylinder has been found and is presented with maximum anticipated damage in the critical areas.

Abstract: Non-Dimensional Design Method (NDDM) for pressure vessels may simplify the design process, reduce the human resource, and it can substitute for the traditional method. The principles and steps of the NDDM were presented. In the method, we constructed two kinds of non-dimension parameters through introducing referenced dimension and pressure. Non-dimensional data of the opening reinforcement structure of pressure vessels were attained. In order to validate the results, two pressure vessels with same structure and different computing pressure and size were designed. The correctness was checked by the present standards. It showed that the NDDM could be applied briefly and reliable.

Abstract: This particular work consider a pressurized vessel typically made of high strength low alloy steel and containing the geometric misalignment at the cylinder-to-cylinder junction. This misalignment produce in the vessel’s structure is because of girth weld that is evident in most of the fabrication of such type of structures apart from other factors which is beyond the scope of this study. This study evaluates the geometrical effects of mismatch on the structural integrity of the pressure vessel and prediction of stresses at the affected area of the cylinder. Analytical and Finite Element (FE) approaches are employed to analyze the configuration. FE analysis is performed by the use of ANSYS on one quarter of the structure due to symmetry. FE results are also compared with the analytical results of different authors. In addition, maximum allowable mismatch is also determined and is a part of this study.

Abstract: In pressure vessels design, WRC107 provides a typical method of local stress analysis to supports and attachments. But influence of the rigidity of attachments on calculation is not considered. For fatigue analysis of round hollow attachment on cylindrical shell, equivalent stresses calculated by WRC107 were compared with those by finite element method. Three attachment thickness configurations, that half, equal, double of the shell thickness were tested. Results show that, in key point Au defined by WRC107 equivalent stress decreases while attachment rigidity increases, and in key point Cu, equivalent stress increases while attachment rigidity increases. When the thickness of attachment equals to that of shell, equivalent stress of WRC107 in Cu comes closest to FEM.

Abstract: This research is based on the project investigation and repeated discussion. The British standard BS7910 was the basic theory, and accordingly carried out the experiment, the computation of the stress parameter and an expert system was developed. In this research, the test materials were gathered from project location, and uniaxial tension test, fracture toughness test are made. Then a material parameter database was established; in the research process, the FEA models of typical power plant pressure vessel were established and the stress parameters were gained through simulation method, and a classified stress database was established. The expert system is an effective assistance method for the safety assessment of the flaws, and it may help the ordinary engineers and technicians to grasp the complex assessment process.