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Development of New Approaches in Descaling in the Continuous Production of Steel using High-Pressure Water Jet
Votavová, Helena ; Hloch,, Sergej (referee) ; Čecho, Ladislav (referee) ; Pohanka, Michal (advisor)
The thesis summarizes general and up-to-date knowledge of descaling during the continuous production of the hot-rolled steel and proposes further streamlining of this process in industrial production. The first chapter of the thesis deals with the origin, structure and physical properties of the scales. The second chapter describes the principles of descaling by using a high pressure flat water jet. The third chapter introduces the principles of the experimental methods and describes the used laboratory equipment. The fourth chapter summarizes the description of the particular experiments and their evaluation, and thus represents the focus of the dissertation. It is divided into six sections which independently solve predefined objectives of the dissertation. The first section focuses on the height and structure development of the scales on 54SiCr6 and HDT580X steels. It has been proven that the height of the formed scales increases with the time and temperature of the oxidation. The layered nature of the scales was verified at the same time. The second section examines the effect of the nozzle stabilizer on the focussing and distribution of the impact pressure of the nozzle. Experiments have shown that increase of 11 % of an average maximum nozzle pressure can be achieved, depending on the type of nozzle and the length of the stabilizer. The third section deals with the analysis of shadowgraphy images of water jet structures of the nozzles. A script was developed for analysis of these shadowgraphy photos by an adaptive thresholding. The findings are correlated using a regression analysis with an average heat transfer coefficient. It has been reported that most of the standard nozzle configurations produced disintegrated stream of little droplets at the height of the rolled surface. The fourth section focuses on the area of water jet overlap, especially the area of the so-called washout, where the impact pressure of one nozzle is reduced by the nozzle stream of the other. The influence of the pressure change and the mutual displacement of the nozzles is investigated. The analysis showed that the change of pressure did not have any effect on the percentage of reduction of the impact pressure in the area of the washout. It has been shown that if the area of the washout is wide the descaling efficiency in this area may be reduced. The fifth section builds on the previous section and focuses directly on the areas of waterjet overlaps. The influence of the change of rotation and pitch of the nozzles is studied. Experiments have shown that small changes in nozzle pitch do not have a significant impact on impact pressure and heat transfer coefficient. The effect of nozzle rotation, on the other hand, was a significant factor for the efficiency and homogeneity of the descaling of the surface. The last section deals with the effect of the rolling speed on the heat transfer coefficient in the descaling process. The regression model has shown that with a higher rolling speed there is a reduction in the average heat transfer coefficient. Conclusion summarizes the results of the dissertation and proposes which findings can be used in the industry to make the descaling process more effective.
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Longitudinal rolling
Sigmund, Lukáš ; Peterková, Eva (referee) ; Podaný, Kamil (advisor)
The thesis describes technology of hot-rolled profiles. It defines the conditions which must be fulfilled for successful process of rolling. Further is described process of producing a specific special profile, which is used as an intermediate for making car door hinge. The profile is made of structural steel S355J2. It is manufactured by VÚHŽ a.s., which uses reverse duo rolling stand with special work rolls. The thesis evaluates the usability, advantages, disadvantages and mechanical properties that are obtained after forming at high temperature.
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Computational analysis of working roll surface layers in hot rolling
Luks, Tomáš ; Hajduk,, Daniel (referee) ; Pohanka, Michal (advisor)
This thesis is dealing with an analysis of thermal and mechanical loads on a work-roll. First, hot rolling focused on work-roll is described in general. A theoretical analysis of roll loads and the mechanisms affecting roll durability are presented here. The thesis is concentrated on creation of a model in FEM program ANSYS. The final model is loaded with different rolling schemes and monitored stresses in a surface layer. The parameters obtained from the measurements performed in a rolling mill are applied as boundary conditions within the model.
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Production of Rolled Profile and Its Verification by Using Numerical Simulation
Sigmund, Lukáš ; Lidmila, Zdeněk (referee) ; Řiháček, Jan (advisor)
The thesis deals with technology of hot-rolled profiles, describing total summary of principles and conditions this process is based on. There is a draft of a calibration of profile, the application of which is subsequently verified through a numerical simulation. Futher in the thesis also was verified the mechanical properties of applied construction steel S355J2 through the up-setting test and compared the results with the used material model in the simulation software Simufact Forming. Then, the test rolling of the calibrated profile was carried out. As a next step, the dimensions of the rolled bars were compared with the results of the simulation, on the basis of which the applicability and suitability of the simulation in the future development of other profiles was verified and evaluated.
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Development of New Approaches in Descaling in the Continuous Production of Steel using High-Pressure Water Jet
Votavová, Helena ; Hloch,, Sergej (referee) ; Čecho, Ladislav (referee) ; Pohanka, Michal (advisor)
The thesis summarizes general and up-to-date knowledge of descaling during the continuous production of the hot-rolled steel and proposes further streamlining of this process in industrial production. The first chapter of the thesis deals with the origin, structure and physical properties of the scales. The second chapter describes the principles of descaling by using a high pressure flat water jet. The third chapter introduces the principles of the experimental methods and describes the used laboratory equipment. The fourth chapter summarizes the description of the particular experiments and their evaluation, and thus represents the focus of the dissertation. It is divided into six sections which independently solve predefined objectives of the dissertation. The first section focuses on the height and structure development of the scales on 54SiCr6 and HDT580X steels. It has been proven that the height of the formed scales increases with the time and temperature of the oxidation. The layered nature of the scales was verified at the same time. The second section examines the effect of the nozzle stabilizer on the focussing and distribution of the impact pressure of the nozzle. Experiments have shown that increase of 11 % of an average maximum nozzle pressure can be achieved, depending on the type of nozzle and the length of the stabilizer. The third section deals with the analysis of shadowgraphy images of water jet structures of the nozzles. A script was developed for analysis of these shadowgraphy photos by an adaptive thresholding. The findings are correlated using a regression analysis with an average heat transfer coefficient. It has been reported that most of the standard nozzle configurations produced disintegrated stream of little droplets at the height of the rolled surface. The fourth section focuses on the area of water jet overlap, especially the area of the so-called washout, where the impact pressure of one nozzle is reduced by the nozzle stream of the other. The influence of the pressure change and the mutual displacement of the nozzles is investigated. The analysis showed that the change of pressure did not have any effect on the percentage of reduction of the impact pressure in the area of the washout. It has been shown that if the area of the washout is wide the descaling efficiency in this area may be reduced. The fifth section builds on the previous section and focuses directly on the areas of waterjet overlaps. The influence of the change of rotation and pitch of the nozzles is studied. Experiments have shown that small changes in nozzle pitch do not have a significant impact on impact pressure and heat transfer coefficient. The effect of nozzle rotation, on the other hand, was a significant factor for the efficiency and homogeneity of the descaling of the surface. The last section deals with the effect of the rolling speed on the heat transfer coefficient in the descaling process. The regression model has shown that with a higher rolling speed there is a reduction in the average heat transfer coefficient. Conclusion summarizes the results of the dissertation and proposes which findings can be used in the industry to make the descaling process more effective.
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|
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Production of Rolled Profile and Its Verification by Using Numerical Simulation
Sigmund, Lukáš ; Lidmila, Zdeněk (referee) ; Řiháček, Jan (advisor)
The thesis deals with technology of hot-rolled profiles, describing total summary of principles and conditions this process is based on. There is a draft of a calibration of profile, the application of which is subsequently verified through a numerical simulation. Futher in the thesis also was verified the mechanical properties of applied construction steel S355J2 through the up-setting test and compared the results with the used material model in the simulation software Simufact Forming. Then, the test rolling of the calibrated profile was carried out. As a next step, the dimensions of the rolled bars were compared with the results of the simulation, on the basis of which the applicability and suitability of the simulation in the future development of other profiles was verified and evaluated.
|
|
|
Longitudinal rolling
Sigmund, Lukáš ; Peterková, Eva (referee) ; Podaný, Kamil (advisor)
The thesis describes technology of hot-rolled profiles. It defines the conditions which must be fulfilled for successful process of rolling. Further is described process of producing a specific special profile, which is used as an intermediate for making car door hinge. The profile is made of structural steel S355J2. It is manufactured by VÚHŽ a.s., which uses reverse duo rolling stand with special work rolls. The thesis evaluates the usability, advantages, disadvantages and mechanical properties that are obtained after forming at high temperature.
|
|
|
Computational analysis of working roll surface layers in hot rolling
Luks, Tomáš ; Hajduk,, Daniel (referee) ; Pohanka, Michal (advisor)
This thesis is dealing with an analysis of thermal and mechanical loads on a work-roll. First, hot rolling focused on work-roll is described in general. A theoretical analysis of roll loads and the mechanisms affecting roll durability are presented here. The thesis is concentrated on creation of a model in FEM program ANSYS. The final model is loaded with different rolling schemes and monitored stresses in a surface layer. The parameters obtained from the measurements performed in a rolling mill are applied as boundary conditions within the model.
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