Povorotnii V. Improving the efficiency of cold rolling mills by rational synthesis of parts of working stands

Dissertation for the degree of a candidate of technical sciences in the specialty 05.05.08 "Machines for metallurgical production". National Metallurgical Academy of Sciences of Ukraine, Dnipro, 2021. The dissertation is devoted to the questions of increase of efficiency of work of working cells of the CRM states. This goal is achieved in two ways: by combining parts that perceive the load in the process of interaction of the processed product and working calibers; changing the allowable values of the rolling effort, based on the results of the study of the volumetric stress-strain state of the workpiece cage. The paper investigates the volumetric stress-strain state of details of work cells of the HPT states, which perceive the technological load in the process of pipe production. Particular attention was paid to the least reliable details in the study, which include work rolls and beds due to their periodic destruction during rolling of pipes. Using the products of three-dimensional modeling and the finite element method, the fields of equivalent stresses and the fields of elastic displacements of the studied parts were obtained while simulating the conditions of their loading close to real ones. In further analysis of the obtained results, the values of the rigidity of the investigated parts were determined and the dependences of the values of maximum stresses arising in their bodies on the magnitude of the effort were determined. On the basis of the results of studies of the bulk stress-deformed state of details of the work stands of the CRM states, a mathematical model was developed to predict the values of the longitudinal thickness of the pipes, taking into account the complete set of the work stand. Comparative studies of the stress-strain state using the finite element method and the strain gauge method for the work stands of the CRM -32 states of rectangular and oval structures, as well as the condition of the CRM -55 state of rectangular structure. Comparison of the results of prediction of longitudinal pipe thickness obtained using the developed mathematical model with the measurements of the actual value of longitudinal pipe thickness obtained in industrial production using a non-destructive control method. On the basis of the results of studies of the stress-strain state of the details of the working cells of the CRM states, dependences of the magnitudes of the boundary forces, which can act on a part of the coefficient of safety margin, were constructed. Based on the obtained dependencies, recommendations were developed for changing the allowable values of the rolling force for the different types of CRM condition stations.