Changing form workpiece in rolling high bodies has its own featuresthat must be taken into account when developing technology. One of the main technological parameters of change form, which largely determines the efficiency of processes, is the rate of spread. Known expressions for the calculation of the spread are obtained for a simple case of rolling, so that for the conditions of rolling high bodies do not provide to determine the spread with acceptable accuracy. Therefore, studies of the peculiarities of changing form during rolling of high bodies remain relevant not only for bloomings, but for rough passages on mills for the manufacture of flat and long products.
 The aim of the work is to study the deformation of the metal, in particular spread, when rolling high bodies in rectangular box gauges.
 To achieve this goal, the following tasks are solved in the work: design of experimentfor the study of metal spread using existing laboratory equipment; conducting an experiment, analysis of reproducibility of experiments; obtaining a model of deformation of high bodies taking into account the shape parameter of the deformation zone; comparison of the obtained results with the data of other authors and analysis of the accuracy of the model.
 From the analysis of publications on dependencies for calculation of spread, a rank number of parameters influencing of spread was defined. Of this series, for the conditions of rolling high bodies, the most significant parameters are the parameter of the shape of the deformation zone and the ratio of the initial dimensions of the workpiece. Experimental studies of the effect of these parameters on the spread were performed using a single box pass embedded in the rolls of the laboratory mill 180. For the conditions and size of the caliber, an experiment of dimension 32 was planned and conducted.
 According to the results of the experiment, the dependence for determining the coefficient spread when rolling high bodies in box passes was obtained. The proposed dependence provides a sufficient level of accuracy in determining the spread within the scope and can be used in the development of technology for rolling high bodies.
 From the analysis of the obtained results it is also established that to correctly take into account the effect of limiting the spread of the side walls of box grooves when rolling high bodies, the research area should be spread by supplementing the obtained model with such parameters as ratio depth grooves and stock on spread in the pass.