Frolov I. Development of scientific bases and deformation modes of cold pilger rolling of tubes with predicted metal properties.

Dissertation is devoted to solving the problem of incorporation of the influence of deformation parameters to change the properties of metal during cold pilger rolling and developing on this base effective technological regimes cold rolling precision pipes with high consumer properties, including the predicted level of metal properties and no-round shape of cross section. Dependence, which links the strain on the proportion of diameter and the properties of metal during cold pilger rolling, was obtained. Previously, cold pilger rolling remained change properties depending on the total (in cross section area) strain. The dependence takes into account the proportion of strain on diameter, as the deformation that significantly affects the ratio of strength and yield stresses of metal after rolling cycle. Determined that this ratio is an indicator of use the properties of metal deformation in specific pilger circumstances. The relationship is also an indicator that can range from 0 to 1 to evaluate the effectiveness of technological elements in terms of use of resource metal properties. The characteristics of deformation during cold pilger rolling correlation that links the proportion of strain rate on diameter and use the properties of metal along the length of working cone is given. Scientifically base for the method of partial deformation distribution along the working cone for cold pilger rolling of steel, deformation of which under normal conditions is difficult is established. Relationship of such parameters of cold pilger rolling process, as the temperature of metal, distribution of partial deformation and homogeneity of metal structures is experimentally confirmed. The method of determining equivalent dimension of cross-section of working cone at cold pilger rolling is found. The method takes into account the change in the working cone cross the entire length of the die's perimeter. Actual and equivalent sizes connect by using indicator, which changes according to the current central angle. The dependence that links the deformation in longitudinal and transverse directions to the changing of deformation in diameter along the length of working cone at cold pilger rolling is established. Known dependence to determine the form of cross profile tool takes to account only total strain. Found that changing the relative width for the investigated rolling routes in certain limits to obtain yield stress decrease by 18%, ultimate tensile strength - 3% increase and relative elongation - 6.2%. The method for determining the mode of deformation during cold pilger rolling, which takes into account changes in the properties of metal in the zone of deformation and ensures a certain level tube's metal properties is developed. 6. Based on modeling by FEM research and the distribution of normal stresses along the working cone and determined dependence coefficient that relates the stress and the parameters of the metal deformation in cold pilger rolling is further developed. On the basis of experimental researches of mutual influence of such technological elements of cold pilger rolling as: temperature metal hood ratio, the number of mill movements, feed volume, strength, yield stress, ultimate tensile strength, surface hardness and method of technological cooling are further elaborated. A method to shift the leading dependence on rails, which provides minimum axial force and determine the amount of displacement depending on the difference between forced and natural rolling radius is found. Technological modes of cold pilger rolling with external and internal longitudinal ribs which reflected the results of researches of the distribution of particle diameter on the deformation in total deformation to alter the properties of metal and applied the method of equivalent size of the working cone of communication between the longitudinal and transverse profiles sizes are found. The recommendations concerning the prediction level properties at industrial conditions and methods of forecasting the properties of metal after cold pilger rolling are given.